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Cornell University Library
OL 536.H85
V.

The mo: uitoes of Nor’

IN
3 1924 002 846 016 mm

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THE MOSQUITOES
OF NORTH AND CENTRAL AMERICA
AND THE WEST INDIES

BY
LELAND O. HOWARD, HARRISON G. DYAR,
AND FREDERICK KNAB

VOLUME ONE _

A GENERAL CONSIDERATION OF MOSQUITOES,
THEIR HABITS, AND THEIR RELATIONS
TO THE HUMAN SPECIES

 

WASHINGTON, D.C.
PUBLISHED BY THE CARNEGIE INSTITUTION OF WASHINGTON
1912
A.eny Uo
CARNEGIE INSTITUTION OF WASHINGTON

Pusrication No. 159, Vou. ONE

Goseor of thig bak
wore first issued

JA& 21 1918

THe Lord Baltimore Press

BALTIMORE, MD., U. 8. a.
TABLE OF CONTENTS.

TNCVODUCHION: ¢ 5 siyjes cs tusiele u sediale a Seman ea dose VR Rea Salwel o HABE on ab eee ARH eoE sais

Early accounts of mosquitoes............. 0c. cece ec seecceuseecceueenueens 8

Mosquitoes a8 Pe8ts... 2 fas cs o2 eevee hues ea cau ee saacaeuuscaneeens vata 8

Early accounts of the biology and structure of mosquitoes............... 20

Structure of the adult mosquito.......... 0... ccc cece cece cece eececeeneeaees 25

PMG TOA oy otiid oak corti AS cher Mtons tn to Xs aod cme arash Gucalaaln atenea x cieekttn a a eymaonnern teu ae 25

PNG CY OG: 6 cS onsite yrabdern da mies oss Miers en kok sake ee eal eioW Gwe tes 25

The: antenne! eee sceey rangers c yeatesaaeid sana can wia eck geacsaueads 26

EWG: C1Y DOU) aise caisshariacesans avaunceich canis ocaia nied renee BG iohe gate Ndeks Wag Sere Gee 36

DDE PrODOSCIS ise sess ce-raiars aide swe Wickes sie Gua ioe Hee HEIs WS FAG RAS BA 37

ENG: Dall .s:. occa avisam ea wag cae ew Nis wee ds a Fates So SOLES need ee 50

PNG: (HORAN ast. Gate ecaa uve $4-Misis s 4 SMR A 4 MO oe A AERC ona lade oon GlomiES saon oa 55

The :prothorax: 2.0 ssid s-censeaiecue davediasw aveison 0:0 chided. ie « Wea wien. ¢ anaugie ds ar RWnraee 55

DHE MESOENOTAR: i. overaiev eis ayiua-e.n s ialana GAs Sen Gis deawere leg BCS RR ante’ 4 57

Me Metathorax .vciece oarsccsieasiee'y 05 dae at4 Rede ba whe 64 ea awe oa Ew EE 59

PNG WINGS: 307s opis Sas Oe ws haan asl Ginelh <6 Bing a2 4 MS POAT ARES ek RE ene 60

MOG MOBS oc aictans a's at octane Gael v's. aA S ew kone, See vamteioh Sad ude Pan ae BS SHS 62

MNS ADGOMEN. 5:5 sys s sivas 5% saces gis Savesey @asacereie ew drew view Shin 40.4: ¥eenweecd Widied ss 67

The abdomen of the female............. ccc cece cece eee c cee eeeeneees 67

The abdomen of the male.............c cece eeeec cee eeeceeceeceuees 69

PVG: SCAICS iach. issa Sages earns o< dads aren uate R 8 anes i aA Sask RAREST RPE TR Gl 71

The internal anatomy of mosquitoes.......... 0c. cc cece ence eee eee nnetenenes 15

GLOSS AMALOMY. 5 siicitis-s ssieraiin se acavanacavaiouecqusl ra wrnbaie P axaule Casas eae adeaions wededeatatetets 75

The alimentary canal......... 0... cece cece eee e eee ee eee eeeeeeeee 75

The TeproductivVe: SYStOM voi oe cen oa seus es see eeu eea ves cee eauRNRAS 79

Ne fat OGY sass gare yawign wae eos O42 8 GES £4 KE RR OE iad sve Fenced 79

The tracheal system ws sca scwec dss b 4 see oa dew 6 ioe wae wea cece o enerne ® 80

FR ISCOLO RY <> se stasis tee time: eyoaaia id dvsdar ote w.loneyh dh web upaub dsb. abeliook cs tustaen ask Gomeauereterd eaters 80

The alimentary canal and appendages...............ccee eevee ceee 80

The reproductive SySteM........... cc ccc cee nee tec cee ceererseccnces 83

The larva, cassis sess soe es Oe hs eee ee tte 62s abe eG Ape BANE Hy else Deve « 84

Head and mouthparts..............0c cece cect cus e ese eee eevee sneenes 84

ARNG: YES cscs iebesis. 6c o Gerd a ersalsla 8 Wee arr ahee Ns ae SHS eRe ENN yeh RGR EES 87

PENG CH OTAXS -.cigecg ie i pide eles segs cca latars wa Sayles Sea cae squnlnetn's Bai ¢ arene wd aries 88

The abdomen. s.0'ss-sycane a we a 38 4 nes vee ss ORE NEON CAA oe BMWS A Sa Oe 88

The respiratory organs................. Sh gtaee wast ah aed tbinadon ba (ootysae Peed eARMaE 89

Modifications of larval structures............ 0. cece eee cece eee ee eeas 91
Adaptations of the mouthparts of Culicid larve to the predaceous

WA DUG says acer eg ahaa ss anes sa washes leans st aie Witte: ade aw ees 3 is se Es 95

Moulting and the number of larval stages.............. 0c cece cece eeeae 97

TENE DUD Ar sons 5. ,5: es nee ead pes Sees WRG ES aun eed he cages Bede Meade levied ala auondava'a acon 99

EXClOSION: OL CHE: TMA LO. asso s:5-inc cies base sunlig 3.4 stank # deg ealee. Gann Gk Cae aie wie areolar ee 103

Habits: of adult MmosquitOes ives. xcses save wid vice gages « & giete wisi cba Beach: woh lorie ane Aiwa s 106

The £000: Habits iiss seek cos Bee's a eagles Ase Few 4a TE ew RES a4 Say aHele es 106

Mosquito songs and their power of hearing............. cc cece eee eee 114

PLDI OL, ACCEL VAL Vesa: 50e.25 cos asge Se snnbicteercas Causes b iacdeuagcgs HUGS so isrg ap else Hd. faveag PUR. yerleut tS gvipltaueh aN allah 118

AsO MBO VACY 5s 4 sar aise ene weiecar ese ee aaaca secanaised tus ia ‘eas seeipeonsgoarcasig wirawer ane sacindcly ve hid lave de eae 118

Hibernation and estivation........ 0.0... cece ec cee eect rete tence 119

Mating habits «ss¢seesecees sd caw sss mpw aes ie bes GA Os rea Ee A HOw 494 eee 120

Abundance of MOSquitoes...... 6. ccc cece eee eee e teen eens 132

Mosquitoes in the far North....... 0... cece ce ccc eee ree cee renee scans 135

Eges and oviposition. « «cies is nce saws eee sa lee be saeigd ele nurs bed see oa bese 140

Habits: of the: larvets see is sxec4 i mw vs sree ce wenees sew aa wae ye asee eee ew eV a oe 146

Food of mosquito larv®.... 0... ccc eect t eee eee Seti aa tacos 150

Hibernation of MoOSquito 1aTVB... cee cee eee te eee eens 154

The pupal Periods css.s0 cee ssa pesea neg aca ge sea te Ran Gs Sedma’ Rea Ce eee RY 155
1V TABLE OF CONTENTS
Page.
Natural ienemiles: i vic gudteeculsag vey due oa dais 43 eae ee oe ea tneeede es 156
Plants «4.06 goiea ses poe 6555 WG oe eRe ees MER Shas swe ENG HET COE LTA ERO EES O 156
Fungi. and. bacteridiss sone sic dea scauiaias taeda dee Wees sess ESTAS 157
AMIS 55 5 seve 2 -ecgsnesacs dx: tie svania 404 dena Od satayaay od gio euciel ayailo Abe are REE DE DERE ESS 159
IPrOCOZOA.sisis.0 aud antan aed aatenes RaeaTs wa eb Authece a eueites Be avaveuas a 6 avon aerevaneits pe 159
Other lowet animals ss. oc ccssc oun aacce enn cv aeons te slaw S baieoe 6 161
WEFMES* succes beanie sain nd crm i seed oles alate bal signee estnes ad aacae ose 162
Insect, enemies +. sieds sexes vc ccees Fe Meee ceed Ea eed bee Hebee eee es 164
Mites: v2.04 start scadasd watameee aku tai Ree S64 Ta Oe ter Pe eR Yea MeR es 172
SDUGOTS) «55.5. sinssecg-tey ati. & Sach sone’ b anlgdor aaavs WT Apacortade re: Gravenstee ecaiausecsescauavece Wd esesuers 175
Other arthropods ..40.4 5: swede pwede cea nd beaded ta oe dea ew Go Rhdes 176
BatracWlans: a vex cciecce ih wiaiany atone asta ewig was wig wiles le levee ptadoin aa eymieasve wa ae 176
Reptiles: GevsG ete ces eee sins ye ais awe ee genean ous cateate cme 177
Birds jeg ieiss goes p30 Shas 8 eeOS a Oe BUS 8s AS ea Sees MEARE Eee TS HES 177
Bats) Seas sasintn in oar ial t n6 Sew y nie aie ee a sieie toe Sie eB tanec ee ee a Sued 179
Collecting, mounting, and rearing............... cece eee eens sol desusuh Seach 180
Collecting adults ........ 0... cece eee cence eee ariets Seta a reader cata i: aie cadalygrevateuen 180
Mounting adults sic oi sss ecna.s teuiens eae eee Fe aes Ppalie es aG cules 180
Sending by maill:or expresss.c.s<sicades semen 64 Sree 54 GHEE a ee 8s HES ae 181
Rearing: sscce sss dine os een ee 24 aes 8 oak tele es eens SADE eS hs 03 See Boks 181
hide: MiOunts: sexe assy sicis. aaa Seeea ses 842 e wiceod Soe Ryariat visa de wisn ene Gaaseh Syebere ud ed yataig: ea an 183
Collecting Vary icisesvika'sceicne Sees oaieis 8 wud da eslsases Sree eo Sale bee Shel ew 184
Collecting 6228S" sxc cite oecen uiserera dees edna tein SOs eee Hee Oe Ewe MR ae 185
The relation of mosquitoes to MaN.......... cece c cee cece eee eee ene eeeees 186
The carriage of disease by MOSQUItOES...... 2... eee ec eeeeee een ee eee 186
APL Y TU OS. sic ssiahinss 0 Sresoe 065g gw Si eae: NAAN TL saan BS Siw DE eee 186
Malaria x3 arigne Se imeue wise Gee cuelawnenslhe ateaheah anette Maes ARS praeeut 188
The malarial organisms.......... ig at bidbca Snag nga rg Aha dareuasa Sy areca deasie hae Sie 188
The life-cycle of the malarial organisms.............-....20000e 189
Scientific demonstration of the transmission of malaria............. 194
The mosquitoes that carry malaria............ 0... cc cece cee cece 202
The habits of Anopheles mosquitoes.......... 0... ccc cece ccc c eee eeee 204
Resting position of adult Anopheles............. cece ec ee cc eee 205
Semi-domestic and wild specieS..............ccc cc ee eee eereeuee 205
Hibernation and estivation............. ccc cece eee cece cence 206
Feeding habits of Anopheles......... 0c cece cece ease cc eeuteees 207
Nocturnal and diurnal habits................ 0... ccc cee eee cece 209
The note of Anopheles... 0... ccc cece ccc cece eee ec eeceeees 211
Distance Of MISH Ue so cdcisiy oe/s a cassse. dso. say 0g Snevave re Syotahar dra diatvare eraceeness 212
The behavior of Anopheles towards certain colors............... 216 k
Breeding places of ANODheleS...... 0... ccc ceca ccc c ees eeaus 218
Anopheles breeding in sea-water.............ccccceeee cece cceae 224
Habits and food of the larvee of Anopheles....... 0... ccc eee cue 229
Resistance to desiccation..............0 0... cece eee ecnceuceccee 231
Length of early stages........... 0... ccc cece eee e cee ceeeueees 231
Number of generations............... 0... c cece cece neceeucees . 232
Geographic distribution of malaria............ 0.0... cece cece ceeee 232
The appearance and disappearance of malaria...................... 36
Decrease of malaria following settlement and civilization........ 236
Increase of malaria due to civilization and its concomitants...... 239
Vollow fever ci0ssthies-raniaicnawuis 64 bodceeesoeaveuuniw ssiesaeecee. 241
The scientific demonstration of the carriage of yellow fever by mos-
CUTE OCS) sso carcnngiss Slraid yin va Aiserw eS acoieid d wicindee Gensosan cds Beh ae 241
Finlay's “WOrk: oxic o's g sain 8 et dd 556 week dog Anno wR Reba e Bes we cd 242
Dr. A. C. Smith’s experiment...........0.0000 cc cec eee cc cece. 242
Demonstrations by the U. S. Army Commission................. 243
Later work in Cuba by Guiteras and John W. Ross.............. 245
Work done in Brazil by the Sao Paulo and the French Com-
MISSIONS 2... eee eee eee ee eect cee eee enn neces 245
The Laredo outbreak of 1903..............0......-.0.00-00000 252
The New Orleans epidemic of 1905........................... 253
The death of Reed, Carroll, and Lazear........................ 255
The search for the causative orgafism............................. 255
The yellow-fever THOS QUILO sie. soe 2 ds coisci aay Se ee E Ave oa Seeds vee el 258
Domesticity of the yellow-fever mosquito...................... 258

Feeding habits ................ eee 259
TABLE OF CONTENTS v

The relation of mosquitoes to man—Continued.
Yellow fever—Continued.

The yellow-fever mosquito—Continued. Page.
TIME) Of; ACIVILY oo x cucda5 waieean candies ee dead aariws eae washed sae 262

Length: Of: litésof ima go sij-d qavemy ao sku araateg sanseee nen ae wate 270
Influence of temperature............. ccc cece eee e ence eee eeees 271

The biting of cadavers............ 0. cece cece eee eee eeeeees 272
Distance: Of: Might. icc. s:e:¢.scarvin a dcaatsveoe 19) wea ecareaual oacncdverel ala evumavaleiers ate 272

MCR IN Se cepecacies tencsee enerie ae esos ae aera ns ia calesdarks batipre ahead sper esoman sagas oe 275
Relation of food to oviposition. ............ ccc cee ect e ener eeeeee 277
OViposltion: 6 evsies sawieed 4ahed Fae eLE CORE TEGMAT TARE SAR sce ~. 278
Breeding: WaDitss cis ses: sresn.acar:sudesn sud sasea we, oarearee SLIM mew anteen Bom diarewlawn she 281

PENN C) OB BS assesin cs Sic avstal@cagpsncis sd arancien < xnntaverdy vanes ear aucoay gator ougeahaweuanenays 281

Breeding: PACES: sais chcoeds sang sad addnas wean eer ruealas elerakaaie ele 283

Behavior: of Jarvesas\y sawed wwwwe Vier oe bend ee nck heseae meee 286

Food habits of larv®.......... 0... c ec cece cence ene e eens 287

Duration of larval stage.......... 0.0.0 c cece cee cee 288

Resistance of larve to adverse conditions.................. 289

The geographic distribution of the yellow-fever mosquito........ 292
Original home of Aédes calopus........ 0c. cece eect ee ee nen ees 294
Distribution by artificial means............. 00. c cece cee eee 298

The yellow-fever mosquito in Hurope...............00 cee eeeeee 301

DOH BUC! sessed Sarai ohead ara eacieash raionianatoe’ ata aes eeuianio wala beuiade a 303
Hularlasis: ssc) venneg ear Wot awmae es one aewled Hy eieas YARN RG ses Rabe oe 307
Transmission by mosquitoes............ 2 cece c ee eee eee eee eens 308
The flaria, WOrmis a biiceo ocd. sia doaadeusnd. sascadendat guns Saaasdaas Mearsenmayaleenecareds 309
Periodicity Of The Tani Biscssss se cevccacesecanaiiecgsa davies Sosna eree a) Weave hale se 309
Evolution in the mosquito.......... 0... cece eee eee cee eee eeeee 310

Mode of transmission to the vertebrate host..............ceeeeeeees 312
Mosquitoes that transmit filariasis.......... 0... . cece eee eee eee 315
Suggested relations of mosquitoes with other disease................005 316
HWffect, OF WOSQUICO: PILES sooo ce ses apace a everarintec as wcadsr aye otera eee tig ecelgiig ee artiaieis ee leieuee® 316
Relative: SUSCEDLIDINGY 1o.ncc 35d ecdececie as aushaig te esa oe See See waa eaes 318
Economic loss from mosquitoes........... 0... eee e eee e cette eee eeeeees 320
OBS: AROMT: WAV ALL ais s.sepace cesete ker cdis gon hetld cs eca arian Sebi adcenn Ropusndl annie vasaleireradevanensracees 320
LOSS. from: VellOW PEOVER... sn nis ceca eed aed aie del we dene Rieds eae ee 325
Endemic disease as affecting the progress of nations.................... 326
Losses from mosquitoes aside from the carrying of disease.............. 328
Reduced value of real estate... 0.0... cece ce eee cee e eee eeee 328
EEOSS? CO) ARTIC UICUTE aio: ascoa Siacassius adecdrancnias autxivaiieok iguanas avacs ero! SudRomue SaaS G aS 330
COBE OF SCTOSDI TE is secascicecocavsvarcn es has erect deta atiaae secnasten da Sgt aetoctcartabiaanto asastelarinfeo 331
The value of reclaimed lands. ........... eee cece eee eee eae 331
Salt marsh lands in New Jersey....... 0... cece cece cece eee eeaes 336
Influence of wind on the dispersal of mosquitoes...................00005 339
The carriage of mosquitoes by ships, railroads and other conveyances.... 345
Mosquitoes in the courts-at-law........ ccc cece eee eee te eee e teenies 352
Protective and remedial work against mosquitoes.............0..0 20 eeee 354
Protection ‘from. Dites’.4....0.4660 04 charmeqansaies weed seer eens 359
SGPCCiS: ANG. CANOPIES ie cceceocice weed edancsi d Sein dtacaeasdl ener Oa aun deed 359
Screening breeding-places ........... 0c cece eee cece ee eee n teens 365
Protective: Jiquids: aa scis.sie-oee gan saps ces wera acess wteceipty elsoneus eas 365
Smudges and fumigantss 6430.62 cccsecseseer sv ves cawiorees ness 367
Pyrethrum or chrysanthemum................... cece e eee 367

Mimms culicide or camphor-phenol.............. 0.20.0 ueee 369

PyeOP WV «i areas ca tesaerilyg ear svtaralg sa eggs & ialiorg cd edsy lees as a tewraeridce Ritaenans 871

Sulfur dioxide: ... .scaccs.weissa ve samiad wise owsweg eeawes 372

MeTrGUriG-- CHG es oo: cciess cocevasessbscesiteayias evaueceistgu vend ciao ahaiavaiinle udereecen 374

Other LUMISANUS «sce cama ware din wee awed aden tae wales 375

Remedies for mosquito bites.......... ccc eee ec ee ee ee eens 376
Apparatus for catching adult mosquitoes............ 0. cee eee eee eee 377
Destruction Of Warvie.. ccccuedacwe sewed deco SEEMS CSE Ra SES Ree cee 379
Permanganate of potash......... cece cece eee eee ee eees 380
Sulphate: of COPPeP is s4.34 eres Mewar maaewnea deel ears eave 380

Certain proprietary COMPOUNAS........... cece cece eee ete es 380

CaCtis: paste) cc banca weteex ened e cede veins Shae Lees Been seuss 381

PetrO] GUI: arcie!dxerddsiandssaaihonice duddos soanscentesichd Medea s aied SARA ARS ROS 381

GOR OUD esses ots 95% arab tierce ernie daadntiers haneRennd balearse acsLeun reais 383
vi TABLE OF CONTENTS

Economic loss from mosquitoes—Continued.
Protective and remedial work against mosquitoes—Continued.

Destruction of larve—Continued. Page.
Phinotas: Oil ¢s00.00iciew ss ecee vee Wed toenea de wee ese see sesstee ees 384

The ideal. larvicide:\ dei.0% qadccainidset aes panes (eaae ses eels ss 384
Larvicide of the Isthmian Canal Commission..................-. 384
Sensitization to light. .... 0... cece cece cee teen eee e nee enee 387
Poisonous: DIANtS) .cie6 sccm nacieda tered sid datrewtepae SOE Mae zo aeons 387

DALE ca dake PA aly die ahd sate Saginaw y eue aie ere Wana Sa wins Rides 388
Abolition of breeding places of household mosquitoes................ 388
Prevention of sewer breeding.............2e eee e cece reer ee eeee 390
Removal of bromeliaceous plantsS.............. cece cece e eee ence eens 391
Drainage measures for non-domestic specieS.............00eee eee eee 391
The practical use of natural enemies of mosquitoes................. 402
Fish introduced into Hawaii.............. cee cee eee eee eee 408

Fishes in the West Indies......... 0... cc cece ccc cece e eee ee cence 410

A Bragilian, NSW y sicccistssceGus oa teetelbaeee ss wake tas aries sees 411

AT ATE CAN MSD ees cess austere acc e acaitens aie Avot landin eae aa brain vs aaa og ES 411

Mr. Thibault’s observations.......... 0.0... cece cece ence ences 412
Alleged deterrent trees and plants............ cece cece cence nee ener 413
Fauealy DEUSE ce obi ceeace s,5 Sey ei’ ccs Adeeb aie wguaeer se. Season a: Wife Posauaeee dosed. 8 413

Ricinus and Papaya........... eptlsadyaansvanatee Sieve eh arahbiaiy dato ea ates 414
QOPI io aisssis cin auacanaaiens aiseidinia vane ed etree ee cles ea aires eens leads 415

China berry trees............ cece cece cece ence ioe Snibate aghauan Siakrens 416

POS ba nkasta sa 2tanetecieacoreteitea Aivigie ph eann rad ee eesl a aie tele aiaieen Sie eos seed 417
Water“plants: ¢ ina cheese deals oan des aes a shaels Csiaueled Bae s Aas 417
Organization for community work..............0c cee eseee cee eeee 421
The importance of interesting children....................0000- 426

Recent work in Germany..............0.0 ccc eeeeueccccuceeneee 427

Work along river fronts.............. cece cece cee eee eeceeeanes 428
Examples of mosquito control.............ccceeecceece as borehee for Sak RNa ats agile eet 429
Work in Havana during the American occupation...............ee0eeees 429
Work at the Isthmus of Panama..................ceeeees oRaasesseds4H8 430
Work in Rio de Janeiro................... whee Gisele ss Kbit ¥ ecient ea ee ese 432
Work in Veracruz and Mexico generally............ccccccccceceeccccce 435
WOOP: AN) Japan ¢ ossctconcacn yg. diaars nd lakes anata PaeancecnoArsiee di cadcae Senedd Oo 436
"Work. im: Alf Ovi a «ois: 5 casarere yx 95 58845 Gea dsssd Hsdnase oldcese BE H)da welwasbane oan 438
Work in Ismailia. .o4 esis sx cnaw so wisi 8.8 weed G4 4 duets wracanwih o-oo ae, Ble Beeld eo aus 440
Work: in Talyia s «cased exis acverdie ce cod svace dus healers bikes caves carding ond Lieie recs % 440
Work in other parts of the world............. 00. ccc ccveeccceeeccceeces 443
by MNO Oe os fasts csiaa ged emcapoie poe ovetatsy waco Sonu es aes ea yess cee 443
Phe. United Slates ious. csocawwwseainra dua eae wiie bath aeesidead pon wee oes 444

BIGMOERADU Ys castnasians pte naeseas hoa dune o wopeaeeeiiev eds ic nett caec. 451
Plate.

II.
III.
IV.

VI.

VII.

VIII.

IX.

XI.
XII.
XIII.
XIV.

LIST OF ILLUSTRATIONS.

Facing page.
. Antennal sense-organ of Culicide............ 0c. c cece eee eee eee ees 30
Mouth-parts of Culex... .00. css oid cates vedewe wan eed mousse ane vee 36
Thorax Of PSOPOPHOT As .0ceicc sawed cnGwnssnwde sa caiearndwune’s geome wh 56
Fig. 1. Heliconia champneiana Griggs. Eastern Guatemala.......... 156
Fig. 2. Bromeliads. Cérdoba, Mexico..............cce cece eee eee ee 156
. Fig. 1. Heliconia champneiana. Eastern Guatemala................. 156
Fig. 2. Epiphytic Tillandsia. Florida Keys............ccceeeeeeveee 156
Fig. 1. Flower-spike of Calathea. Eastern Guatemala................ 156
Fig. 2. Bromeliaceous plant on trunk of royal palm. Porto Rico...... 156
Fig. 1. Anopheles and Culex larve in natural position in water....... 158
Fig. 2. Adult mosquitoes destroyed by fungus...............2e0e000 158
Wigs. 1,2. Larva..of Chaoboruss eses ss suvess eawassosesasasewnevaeacs 168
Fig. 3. Larva of Corethra.......... 2. ccc cc cece ee eee et ee eee e eee eees 168
Fig. 1. Crane Lake, Saskatchewan, June, 1907. Mosquito net for
PTOtECtlOm. OL“ 1AC Os. cise a serekiag aieacnis Sig ere lea Rene hisiosmenees 252
Fig. 2. Destroying the yellow-fever mosquito by fumigation.......... 252
. Fig. 1. Covered rain-water tanks at New Orleans..................5. 282
Fig. 2. House at Pretoria, Transvaal, protected against ants by resting
on water-filled metal panS............. cece cece cece eeeee 282
Fig. 3. Mosquito-breeding tree-hole .......... 0... ccc cece cece ee eeee 282
Mosquito breeding-places at Dallas, TexaS.......... 0... ce cee eee cees 286
Operations of filling in salt marshes, Sheepshead Bay, Long Island.... 334
Draining the salt marsh, Hackensack Meadows, New Jersey.......... 336
Fig. 1. School children finding mosquito breeding-places, Worcester,
MESS sy» ce gesscgcca oy a veciticcorcens ancien) tice ahvaria Yahoos see (or avo cena uiarea jig S aitanie emg har 356
Fig. 2. Mosquito class-work, Worcester, Mass.............0 eevee eeee 356

vii
INTRODUCTION.

The discovery that mosquitoes are agents in the transmission of certain dis-
eases, and especially the discovery by Sir Ronald Ross, in 1898, that mos-
quitoes are the agents in the transmission of malaria, aroused a widespread
interest in these insects. Hitherto the Culicide had been treated by ento-
mologists with the other flies, and, being regarded as unimportant members of
the order Diptera, were not especially studied and only such species as happened
to find their way into entomological collections were described by systematists.

In the year 1902, when the Carnegie Institution of Washington began its im-
portant work in aid of scientific research, the systematic and biological knowl-
edge of American mosquitoes was slight. A bulletin published by the U. 8.
Department of Agriculture in 1900 embodies our knowledge of the North Ameri-
can mosquitoes at that time. Twenty-three species were distinguished in this
bulletin, while a number of the descriptions by early writers remained unrecog-
nized. For the first time, the full life-histories of two widely different species
were given. In the same year Major George M. Giles, formerly naturalist of
the Indian Marine Survey, published in London the first edition of his “ Hand-
book of the Gnats or Mosquitoes,” which was the first attempt to bring together
and codrdinate the knowledge of the mosquitoes of the world. This work in-
cludes 48 species from North America and, although many of these were un-
known to the author, the original descriptions were made available for students.

In 1901 the British Museum of Natural History published the first two
volumes of “ A Monograph of the Culicide of the World,” by F. V. Theobald.
In this work, 69 species were treated as North American and West Indian, but a
number of these had not been studied by the author. At about the same time a
volume entitled “ Mosquitoes; How they Live; How they Carry Disease; How
they are Classified ; How they may be Destroyed,” by L. 0. Howard, was pub-
lished. In this book 25 species were recognized and classified in synoptic tables
by D. W. Coquillett. Considerable space was given to discussions of the habits
of mosquitoes, their function in the carriage of disease and to the subject of
remedies.

While considerable knowledge had accumulated about the habits of mosqui-
toes in general, it became evident that the different species diverged widely in
habits and detailed information on these points was needed. It is necessary to
distinguish carefully in this respect. Only those species that are harmful to
man, either as agents in the carriage of disease or as annoying by their bites,
need to be considered in economic work. Much useless labor and expense can
be avoided by an accurate knowledge of the habits of the species. For instance,
Boyce (Mosquito or Man?, p. 96, 1909) refers to the mosquitoes living in crab-
holes as “the chief nuisance in those houses which are situated near the sea,”
and figures a tent for capturing these mosquitoes. Our observations prove that
the crab-hole mosquitoes do not bite nor annoy man, and no consideration need
therefore be given to their destruction. Again, the commonest mosquito during

1
2 MOSQUITOES OF NORTH AMERICA

the summer months in the Northern States is undoubtedly Culex territans,
which is the only species breeding abundantly in a certain class of fresh-water
marshes and pools at that season. We now know that this species does not annoy
man (in spite of its name), and are enabled to state that such fresh-water
marshes and ponds are not breeding-places of noxious mosquitoes.

Therefore, realizing the imperfect character of our knowledge and especially
the very great need of a competent monograph of the species of Culicide of
North and Central America and the West Indies, both from the biological and
the sanitary points of view, application was made, in April, 1902, to the
Carnegie Institution of Washington, for a grant which should enable the prepa-

_ tation of a monograph to include all possible information concerning all mos-
quitoes of the geographical regions just mentioned.

The grant requested was made by the Trustees of the Institution in January,
1903, and organization work was at once begun. It was at first expected that the
monograph could be completed in three years, and the grants made by the In-
stitution covered that period. At the expiration of the third year, however, it
was found that the material was by no means complete. Too much reliance had
been placed upon the promises of volunteer observers, and important regions
were, for this reason, not properly covered. The workers engaged in the prepara-
tion of the monograph were not content to publish the material accumulated,
since it was their earnest desire to make the work as complete as possible and as
valuable as possible to biologists and to sanitarians. The investigations were,
therefore, continued during 1906, 1907, and 1906, partly by the help of funds
appropriated to the U. S. Department of Agriculture by Congress for the in-
vestigation of insects affecting the health of man and animals, partly by the
assistance of the Isthmian Canal Commission, partly by the help of volunteer
observers in the West Indies and Central America, and partly at the expense of
two of the authors (Dr. Dyar and Mr. Knab). While it is realized that the
present work is incomplete, the additions gained by the work of the last few
years has surely more than doubled its value.

In planning the work in the early months of 1903, it was decided to secure
local observers advantageously situated in the different faunal areas of the
United States, and to compensate them for observations during the summer
months, in the course of which each should make as complete a collection as
possible of the mosquitoes of the region in which he was located, should rear
each species in all its different stages, and should submit all specimens and com-
plete notes, with sketches, at the completion of the season. During the first
year there were employed for this purpose Miss Isabel McCracken, of Stanford
University, a graduate student and assistant of Prof. V. L. Kellogg; Mr. Fred-
erick Knab, of Chicopee, Massachusetts (one of the present authors) ; Mr. O.
A. Johannsen, of Cornell University, Ithaca, New York; Mrs. E. @. Hinds, at
Victoria, Texas; Mr. John R. Taylor, of Las Animas Hospital, Havana, Chibex
Dr. H. G. Dyar, of the U. S. National Museum (one of the present authors), at
Kaslo, British Columbia; Mr. T. H. Coffin, of the Johns Hopkins Medical
School, in the Bahama Islands; and Mr. Kenneth Taylor, at Minneapolis,
Minnesota.
INTRODUCTION 3

In addition to these observers, the following individuals made volunteer col-
lections and observations which were transmitted to Washington: Mr. G. G.
Coghill, of Pacific University, Forest Grove, Oregon; Major William M. Black,
U.S. Army, Panama; Mr. H. C. Weeks, Bayside, Long Island, New York; Dr.
J. B. Smith, State Entomologist of New Jersey, New Brunswick ; New Jersey ;
Dr. Alfredo Dugés, of Guanajuato, Mexico; Dr. J. W. Dupree and Prof. H. A.
Morgan, of Baton Rouge, Louisiana; Dr. José H. Pazos, of San Antonio de los
Baiios, Cuba; Dr. W. E. Britton, State Entomologist, New Haven, Connecticut.

The material brought together during 1903 was very encouraging, and many
of the reports of the paid observers were full and contained many new contribu-
tions to the knowledge of the early stages of mosquitoes.

With the opening of the season 1904 it was thought best to limit the number
of paid observers working in the manner described above, and only two were so
employed, namely, Mrs. Maurice F. Ricker, of Big Fork, Montana, the wife of
Professor Ricker, the head of the summer biological station at that point, and
Mrs. Hinds, of Victoria, Texas. Dr. A. Siegrist, of Puerto Angel, Pochutla,
Oaxaca, Mexico, was also tentatively engaged. The sanitary officials of the
Panama Canal Commission promised assistance, and two of them were promised
compensation for expenses incurred in collections and observations. The results
from Panama and from Puerto Angel were, however, nil.

The extreme importance of a most thorough knowledge of everything con-
nected with the yellow-fewer mosquito (Aédes calopus) induced the grantee of
the research fund during the spring and summer of 1904 to make an especial
effort to determine its geographical distribution, and to learn as much as possible
about its habits. In the course of another investigation he went to south Mexico
in the spring, going as far south as Oaxaca, and studied the effect of altitude
upon the distribution of the species from the seaboard at Vera Cruz up to
Orizaba. The Mexican sanitary authorities were consulted, and his efforts were
very intelligently seconded through the great courtesy especially of Dr. Eduardo
Liceaga, the president of the Superior Board of Health of the Republic of
Mexico.

Beginning with the middle of June, Mr. Herbert Barber, of Washington, was
sent upon a trip to determine, if possible, the line of northward distribution of
the yellow-fever mosquito in the United States. He began at Brownsville,
Texas, and followed approximately the line of distinction between the upper and
lower austral life zones as laid down by Merriam. He proceeded gradually as
far as Louisville, Kentucky, where the work was taken up September 1 by Mr.
T. H. Coffin, who followed it through to the Atlantic seaboard.

By the operations just described the main portion of the mosquito fauna of
the principal inhabited regions of the United States was rather fully worked
up, and during 1905 an especial effort was made to secure material representing
the mosquito fauna of southern Mexico, Central America, the West Indies, and
Alaska. The Canal Zone was again left to volunteer observers. One of the
authors, Mr. Knab, left Washington the end of May, visited Key West and
Havana, then Vera Cruz, Cérdoba, Orizaba, Santa Lucrecia, Rincon Antonio,
Almoloya, Tehuantepec, Salina Cruz, and Acapulco in Mexico; Acajutla, San
4 MOSQUITOES OF NORTH AMERICA

Salvador, Sonsonate, and Izalco in the Republic of Salvador ; Champerico and
San José in Guatemala; Puntarenas, Santo Domingo, San José and Port Limon
in Costa Rica; and Corinto, Nicaragua. Mr. Knab collected a large amount of
valuable material, and one important result of this work was to show that the
yellow-fever mosquito occurs at every point visited on the Pacific coast. While
it could be assumed that this would be the case, there had, up to that time, been
no authentic record of the fact.

At the same time that Mr. Knab started for Central America, Mr. August
Busck, of the Department of Agriculture, was sent to the West Indies, sailing
from New York on June 1. He visited Grenada, Trinidad, Tobago Island, St.
Vincent, Barbados, Martinique, Dominica, Guadeloupe, St. Thomas, Santo
Domingo (Santo Domingo City, San Francisco Mountains and Samara Bay),
returning to Washington early in October, having collected and bred a very ex-
tensive series of mosquitoes and having aroused the interest of a number of local
observers, who subsequently were of much assistance in the investigation.

Early in the summer Mr. A. N. Caudell was sent to Florida to work out the
life history of a species not yet fully known, and in the spring Dr. Dyar and Mr.
Knab went to western New England to study carefully the as yet little under-
stood spring and early summer mosquitoes of that region. During midsummer
Dr. Dyar visited the Adirondacks to work out some hitherto unknown points in
the life histories of certain species inhabiting that region.

Early in June, while engaged upon another investigation, the grantee visited
the Natural History Museum in Vienna to study the mosquito types of Wiede-
mann, in the Wiedemann and Winthem collections. He took with him from the
United States determined material of several species about which there existed
some doubt as to their identity with the Wiedemann types, and cleared up
several points of systematic importance. Returning to this country in the early
autumn he was able to give many points of value in quarantine measures to the
Public Health and Marine-Hospital Service, and in late October visited New
Orleans and observed the operations of the closing days of the campaign against
the yellow fever, which proved so successful, making notes on the methods used
against the yellow-fever mosquito and taking photographs.

During 1906 Dr. Dyar made extensive observations upon the Pacific coast of
the United States, stopping first at Bright Angel Camp in Arizona, and then
proceeding gradually from San Diego northward through California, Oregon,
and Washington into British Columbia, stopping a sufficient length of time at
favorable localities to make the requisite observations and rearings. The trip
was begun in April and the final observations were made August 26.

Considerable additional material was received from volunteer assistants dur-
ing the year, and especially from Mr. F. W. Urich, of Trinidad, British West
Indies. The main portion of the year was devoted to preparation of descrip-
tions and illustrations and general work on the monograph. The intended ex-
pedition for the study of the mosquitoes of Alaska was, however, not made.

In 1907 the paucity of material from the Panama Canal Zone was very
obvious as contrasted with the abundant material from other Tegions, and,
INTRODUCTION 3

although liberal promises had been made by persons stationed in the Zone,
practically no material had been received during the four years already spent
upon the monograph. An arrangement, therefore, was made with the Isthmian
Canal Commission by which the expenses of a trained observer were met by the
Commission during a period covering the end of the dry season and practically
all of the rainy season, the time occupied in a visit to the Zone and a careful
study of its mosquito fauna. Mr. August Busck was selected for the purpose.
He left New York April 12, arrived at Colon April 19, and from April 19 to
July 30 worked the Zone from Panama to Colon, though mainly the region
around Tabernilla, and also made two trips into Panama, on the Upper Chagres
River, from May 18 to 28, and to Taboga Island, from June 30 to July 7. The
amount of information gained by this expedition was extraordinary. Previously
only 7 species of mosquitoes were known from the Canal Zone, but Mr. Busck
returned with more than 90 species, of which 30 were new to science. His visit
also interested certain persons, resident there, in the more careful study and
rearing of mosquitoes, and a great deal of additional valuable material has been
received since his return, especially from Mr. A. H. Jennings of the Sanitary
Department. The expedition resulted in benefit to the Sanitary Department of
the Isthmian Canal Commission, since Mr. Busck was able to give some im-
portant points on the habits of certain species concerned in the transmission of
disease. At the same time he learned much concerning the practical work carried
on under the Sanitary Department and returned filled with admiration for the
enlightened efforts which had accomplished such admirable results in the prac-
tical elimination of the disease-carrying mosquitoes from the Zone.

Mr. Knab undertook an expedition to Saskatchewan to work out the life
histories of the mosquitoes of the northern prairies, until then unknown. He
left Washington early in April and returned the latter part of June. Dr. Dyar
later visited a new locality in Maine.

The work during 1908 was mainly devoted to the continuance of the prepara-
tion of the monograph. Dr. Dyar did some field work in Maine and New Hamp-
shire in midsummer. Mr. Knab in the winter of 1907-1908 visited Mexico,
remaining during the early months of 1908 in the vicinity of Vera Cruz, Cér-
doba, Orizaba and Omealca, engaged partly upon another investigation, but also
collecting and rearing mosquito material.

During the entire period of the preparation of the monograph the grantee and
his fellow authors have met with the heartiest cooperation on all sides. While
it is true that many promises have been made which have not been fulfilled, and
while it is true that the completion of the work has been delayed through a too
great reliance upon certain of these promises, and while through such a reliance
the mosquitoes of certain regions have not been studied with the necessary care
to properly round out the work, it is well understood by the authors that by no
means all of the good intentions of a busy man can be fulfilled, and they are
grateful for the intention itself and for the cordial promises. They realize also
that while it seems easy to collect and rear mosquitoes, it is really a rather diffi-
cult thing to do properly, and only when properly done are the results of value.
6 MOSQUITOES OF NORTH AMERICA

It has been found necessary to omit the group Corethrine, which should be
included to properly round out the family Culicide, and restrict ourselves to
the Culicine—the forms with the long proboscis.

It seems advisable to call attention at the outset to changes in the scientific
names of those species which are most important from the economic standpoint.
These changes have become necessary, partly through the strict application of the
laws of priority, partly through generic revision, and also from a more exact
knowledge of the specific limitations of the species concerned. The reasons for
these changes will appear in the systematic part of the work.

Most important is the change in the name of the yellow-fever mosquito from
the generally adopted Stegomyia fasciata and Stegomyia calopus to Aédes calo-
pus as a result of the untenability of the generic concept “ Stegomyia.” What
was known in this country as Anopheles maculipennis is now Anopheles quad-
rimaculatus and A. occidentalis, the first-named species being distinct and con-
fined to the Old World. Through priority Culex fatigans or Culex cubensis be-
comes Culex quinquefasciatus. Culex pungens appears to have been used in the
earlier writings on North American mosquitoes as a concept to include Culex
pipiens, Culex restuans, and Culex quinquefasciatus (and perhaps others) before
these species had been differentiated.

While it is expected that this work will be of assistance to medical and sani-
tary men, as well to others, it must be distinctly understood that it is an ento-
mological monograph and not a medical monograph. The writers are ento-
mologists and not physicians or medical investigators. Thus, while necessarily
in the first volume some space is given to the history of the discoveries of the
relation of mosquitoes to disease, and to the diseases themselves in a broad way,
as well as some consideration of the life histories of their causative organisms,
these portions are not the result of original investigation, but have been com-
piled from reliable sources.

We are under great obligations to Dr. Arthur Neiva, of the Instituto Oswaldo
Cruz in Rio de Janeiro, who, during a visit in Washington, gave us liberal
help and advice in the preparation of the parts on mosquito-borne diseases. The
part on the malarial organisms is from his pen and presents the modern views in
succinct form.

Especial thanks are also due to Mr. Louis H. Aymé, United States Consul-
General at Lisbon, Portugal, who, while in the States on a vacation from his
former Brazilian post, spent many hours of his leisure time in translating for
the writers, from the Portuguese into English, the more important portions of
Goeldi’s large work on the mosquitoes of Para. To the following the hearty
thanks of the authors are due for material or for assistance in one way or an-
other. In this list are not mentioned the writers’ colleagues in the Division of
Insects, U. 8. National Museum, or in the Bureau of Entomology of the U. 8.
Department of Agriculture, although many of them have been of assistance.
Individual species or small lots of mosquitoes have been received from many

correspondents, but these are mentioned in the text in the consideration of the
individual species.
INTRODUCTION 7

Rev. J. Aiken, St. Catherines, Berbice, British Guiana.

Prof. J. M. Aldrich, University of Idaho, Moscow.

Mr. E. E. Austen, British Museum of Natural History, South Kensington,
London, England.

Dr. George E. Beyer, Tulane University, New Orleans, Louisiana.

Prof. Raphael Blanchard, University of Paris.

Mr. J. Turner Brakeley, Hornerstown, New Jersey.

Dr. Hiram Byrd, Sanitary Department, Jacksonville, Florida.

Dr. F. E. Campbell, Surgeon, U. S. Navy.

Prof. T. D. A. Cockerell, University of Colorado, Boulder, Colorado.

Mr. O. F. Cook, Washington, D. C.

Prof. R. A. Cooley, Entomologist, Bozeman, Montana.

Dr. C. C. Craft, Department of Terrestrial Magnetism, Carnegie Institution of
Washington, Washington, D.C.

Dr. Oswaldo Goncalves Cruz, Instituto Oswaldo Cruz, Rio de Janeiro.

Dr. George Dimmock, Springfield, Massachusetts.

Dr. A. Dugés, Guanajuato, Mexico.

Mr. F. W. Edwards, British Museum of Natural History, South Kensington,
London, England.

Dr. J. Hobart Egbert, Willimantic, Connecticut.

Dr. E. P. Felt, Entomologist, Albany, N. Y.

Dr. J. Fletcher, Ottawa, Canada.

Mr. Arthur Gibson, Ottawa, Canada.

Dr. E. A. Goeldi, Berne, Switzerland (formerly Para, Brazil).

Col. W. C. Gorgas, U. S. Army, Chief Sanitary Officer, Isthmian Canal Com-
mission.

Dr. M. Grabham, Kingston, Jamaica.

Prof. Dr. Anton Handlirsch, k. k. Zool. Museum, Vienna.

Prof. A. L. Herrera, Mexico City.

Prof. Glenn W. Herrick, Agricultural College, Mississippi.

Mr. A. H. Jennings, formerly Entomologist to the Isthmian Canal Commission,
Ancon, Canal Zone, Panama.

Prof. C. W. Johnson, Boston Society of Natural History.

Prof. K. Kertész, Hungarian National Museum, Budapest.

Dr. Eduardo Liceaga, Mexico City.

Dr. C. S. Ludlow, Washington, D. C.

Dr. Adolpho Lutz, Instituto Oswaldo Cruz, Rio de Janeiro.

Sir Patrick Manson, London School of Tropical Medicine.

Prof. Frederick Meinert, Zoological Museum, Copenhagen.

Mr. H. W. B. Moore, Georgetown, British Guiana.

Dr. G. H. F. Nuttall, Cambridge, England.

Dr. P. Osterhout, Bocas del Toro, Panama.

Dr. José H. Pazos, San Antonio de los Bafios, Cuba.

Dr. H. Polak, Paramaribo, Surinam.

Sir Ronald Ross, Liverpool School of Tropical Medicine.

Dr. A. H. S. Russell, Surgeon, U. S. Navy.

Dr. A. E. Shipley, Cambridge, England.

Mr. W. H. Sligh, Department of Terrestrial Magnetism, Carnegie Institution of
Washington, Washington, D. C.

Dr. John B. Smith, Entomologist, New Brunswick, New Jersey.

Prof. E. P. Taylor, Entomologist, Mo. State Fruit Experiment Station, Moun-
tain Grove, Missouri.

Mr. J. R. Taylor, Las Animas Hospital, Havana, Cuba.

Prof. F. V. Theobald, Wye (Kent), England.

Mr. J. K. Thibault, jr., Scott, Arkansas.

Dr. W. F. Thornton, Bluefields, Nicaragua.

Prof. E. S. G. Titus, Entomologist, Logan, Utah.

Prof. W. V. Tower, Entomologist, San Juan, Porto Rico.

Mr. F. W. Urich, Entomologist, Port of Spain, Trinidad.

Mr. J. B. Vanduzee, Estero, Florida.

Dr. H. A. Veazie, New Orleans, Louisiana.

Mr. H. C. Weeks, Bayside, Long Island, New York.

Mr. T. N. Willing, Regina, Saskatchewan.

Dr. K. S. Wise, Public Hospital, Georgetown, British Guiana.
EARLY ACCOUNTS OF MOSQUITOES.
MOSQUITOES AS PESTS.

The old writer, Thomas Moufet, collected from early writings accounts of
mosquito abundance, from which it appears that Herodotus noted that these
insects swarmed in prodigious numbers in old Egypt and that the natives of
marshy regions built towers on which to sleep, since the mosquitoes did not fly
high. Mosquito nets and canopies were in use in those early days. The army
of Julian the Apostate on one occasion was so fiercely attacked by mosquitoes
as to be driven back. In ancient Greece, according to Pausanias, the inhabitants
of cities were sometimes forced to abandon their homes on account of mosquitoes
making it impossible for them to remain. Mionte, a rich city of Ionia, was
abandoned by its inhabitants on account of mosquitoes which forced them to flee
to Mileta. The same thing happened with Pergamo, a beautiful city in Asia.
Sapor, King of Persia, according to Theodoritus, was compelled to raise the siege
of Nisibis by a plague of gnats which attacked his elephants and beasts of burden
and so caused the rout of his army.

Ammianus Marcellinus, in his Roman History, in discussing the wild beasts
of Mesopotamia, gives the following paragraph on lions versus mosquitoes
(quoted from Cowan) :

“ The lions wander in countless droves among the beds of rushes on the banks
of the rivers of Mesopotamia and in the jungles, and lie quiet all the winter,
which is very mild in that country. But when the warm weather returns, as
these regions are exposed to great heat, they are forced out by the vapours, and by
the size of the Gnats, with swarms of which every part of that country is filled.
And these winged insects attack the eyes, as being both moist and sparkling,
sitting on and biting the eyelids ; the lions, unable to bear the torture, are either
drowned in the rivers, to which they flee for refuge, or else, by frequent scratch-
ings, tear their eyes out themselves with their claws, and then become mad. And
if this did not happen, the whole of the East would be overrun with beasts of this

kind.”

Pliny, in his natural history, speaks of mosquitoes and in referring to their
humming noise says (freely translated) : “ Who gave the mosquito so terrifying
a voice, infinitely greater than it should be in comparison to the size of its
body?” He distinguished the Hymenoptera from the Diptera by stating that
the former have the sting in the tail and the latter in the mouth, and that to
the one it is given as an instrument of vengeance and to the other of avidity.

About 1736 Culex pipiens became so numerous in England that, as described
by John Swinton, vast columns of them were seen to rise in the air from the
steeple of the cathedral at Salisbury, which, at a little distance, resembled
columns of smoke and caused many people to think that the cathedral was on
fire. In the same account it is stated that in the year 1766, in the month of
August, they appeared in such incredible numbers at Oxford as to resemble a
black cloud darkening the air and almost intercepting the rays of the sun. On

8
MOSQUITOES IN THE CRIMEA 9

the evening of August 20, Sir John Swinton, in the garden of Wadham College,
about half an hour before sunset, saw six columns of these insects ascending from
the tops of six boughs of an apple tree—two in a perpendicular, three in an
oblique direction, and one in a pyramidal form—to the height of 50 or 60 feet.
During that season mosquitoes were particularly troublesome by their bites.

Such swarms as these were evidently rather commonly seen in the marshy
parts of old England, as indicated by the following lines from Spenser’s Faerie
Queene:

As when a swarme of gnats at eventide

Out of the fennes of Allan doe arise,

Their murmuring small trumpets sownden wide,
Whiles in the air their clust’ring army flies,

That as a cloud doth seem to dim the skies;

Ne man nor beast may rest or take repast,

For their sharp wounds and noyous injuries,

Till the fierce northern wind with blust’ring blast
Doth blow them quite away, and in the ocean cast.

Spenser, in his “ View of Ireland ” (1633), has the following on the subject
of the Irish mosquitoes :

“They goe all naked except a mantle, which is a fit house for an outlaw—a
meet bed for a rebel—and an apt cloak for a thiefe. It coucheth him strongly
against the Gnats, which, in that country, doe more to annoy the naked rebels,
and doe more sharply wound them, than all their enemies’ swords and speares,
which can seldom come nigh them.”

Kirby and Spence have brought together several instances of remarkable
stories from the older travels, such as the following:

“ In the neighborhood of the Crimea the Russian soldiers are obliged to sleep
in sacks to defend themselves from the mosquitos; and even this is not a suffi-
cient security, for several of them die in consequence of mortification produced
by the bites of these furious blood-suckers. This fact is related by Dr. Clarke,
and to its probability his own painful experience enabled him to speak. He
informs us that the bodies of himself and his companions, in spite of gloves,
clothes, and handkerchiefs, were rendered one entire wound, and the consequent
excessive irritation and swelling excited a considerable degree of fever. In a
most sultry night, when not a breath of air was stirring, exhausted by fatigue,
pain and heat, he sought shelter in his carriage; and, though almost suffocated,
could not venture to open a window for fear of the mosquitoes. Swarms never-
theless found their way into his hiding-place ; and, in spite of the handkerchiefs
with which he had bound up his head, filled his mouth, nostrils, and ears. In
the midst of his torment he succeeded in lighting a lamp, which was ex-
tinguished in a moment by such a prodigious number of these insects, that their
carcasses actually filled the glass chimney, and formed a large conical heap over
the burner. The noise they make in flying can not be conceived by persons who
have only heard gnats in England. It is to all that hear it a most fearful sound.
Travellers and mariners who have visited warmer climates give a similar account
of the torments there inflicted by these little demons. One traveller in Africa
complains that after a fifty miles journey they would not suffer him to rest,
and that his face and hands appeared, from their bites, as if he was infected with
the small-pox in its worst stage. In the Hast, at Batavia, Dr. Arnold, a most
attentive and accurate observer, relates that their bite is the most. venomous he
ever felt, occasioning a most intolerable itching, which lasts several days. The
sight or sound of a single one either prevented him from going to bed for a

2
10 MOSQUITOES OF NORTH AMERICA

whole night, or obliged him to rise many times. The species, which I have ex-
amined, is distinct from the common gnat, and appears to be nondescript. It
approaches nearest to C. annulatus, but the wings are black and not spotted.
And Captain Stedman in America, as a proof of the dreadful state to which he
and his soldiers were reduced by them, mentions that they were forced to sleep
with their heads thrust into holes made in the earth with their bayonets, and
their necks wrapped round with their hammocks.”

Quite the most interesting and really important of the observations upon
mosquitoes by the older travellers, however, are those of Humboldt. The account
is of general interest as indicating the conditions of life in the regions of the
upper Orinoco and Magdalena rivers, and the hardships endured by the mission-
aries who early visited those regions and who passed their lives there. It is also
of special interest as a record of the observations of a very acute observer and
reasoner. The observations were all original, and most of them were in direct
contradiction to the views of former travellers and of the writers on natural
history. The differentiation between the different species of biting flies, includ-
ing mosquitoes, the discovery that different species inhabit different regions and
bite at different times of the day and of the night, the fact that with certain of
the residents of the upper Orinoco the existing fevers and other maladies were
attributed to mosquitoes, the curious reasoning of the author on the possible
carriage of disease by blood-sucking insects and the origin of fevers, and many
other points in this chapter combine to make it one of very great interest in thé
light of present knowledge of the Culicide of tropical regions. Parts of it,
therefore, in free translation, are here presented. It must be kept in mind that
Humboldt’s account deals with biting flies belonging to different families, and,
in speaking of the separate forms, he uses the terminology customary in the
Spanish-American countries. By the term “ mosquitos” he does not mean
Culicide, but Simuliide; the mosquitoes in our sense are called “ zancudos”
and “ tempraneros ” ; the “ jéjen ” are minute Chironomid, now assigned to the
genus Culicoides. In speaking of these forms collectively, Humboldt uses the
term “ tipulaires,’ which roughly corresponds to the group Nemocera, as now
understood. In order to avoid confusion we have translated the French word
“cousin,” which corresponds to our word “ mosquito,” by the word “ gnat.”

“ After having spent two days at the cataract of Atures we were glad to be
able to leave a place where the temperature of the air was generally 29° C. in
the day and 26° C. at night. This temperature seemed still warmer than it
really was. The lack of concurrence between the thermometer and our feelings
should be attributed to the continuous irritation of the skin by the mosquitoes.
An atmosphere filled with venomous insects always appears hotter than it really
is. A Saussure hygrometer indicated in the shade (as usual) at the minimum
in the day time (3 hours after noon) 78° 2”, at night at the maximum 81° 5”.
.. « We were horribly tormented by the mosquitos and by the jéjen, venomous
little flies or simuliums; at night by the zancudos, a species of large gnat or
mosquito which is feared even by the natives. We began to have badly swollen
hands and faces, and the inflammation increased from day to day until our
arrival on the banks of the Temi. The means by which they try to escape from

these little animals are very extraordinary. The good missionary, Bernardo Zea,
who passes his life under the torments of mosquitoes, has constructed himself,
HUMBOLDT’S OBSERVATIONS 11

near his church, upon a scaffolding of palm trunks, a little room in which he can
breathe more freely. We mounted there in the evening by the help of a ladder,
to dry our plants and to write up our journey. The missionary had noticed with
exactness that the insects abound most in the lower layer of the atmosphere, that
which is near the soil, up to 12 to 15 feet in height. At Maypures the indians
leave their village in the night in order to go to sleep on the little islands in the
middle of the cataract. They get some sleep there; the mosquitoes appear to
avoid the air surcharged with vapors. Everywhere we found them less abundant
in the middle of the river than on the banks; in descending the Orinoco one
suffers only when getting into the boat.

“ Persons who have not sailed upon the great rivers of equinoctial America,
the Orinoco for example, or the Magdalena, can not conceive that at every mo-
ment, without interruption, one can be tormented by the insects swarming in the
air, and how the number of these little animals can render vast regions almost
uninhabitable. One can never become accustomed there to stand the bites with-
out complaint. However lively may be one’s interest in the objects of his search,
it is impossible that one should not be constantly distracted by the mosquitos,
the zancudos, the jéjen, and tempraneros, which cover the hands and face, which
pierce the clothing with their spear-like suckers, and which, getting into the
nostrils and into the mouth, make you cough and sneeze. Thus... in the
missions of the Orinoco, in these villages placed on the banks of the river, sur-
rounded by immense forests, the plague of flies affords a constant topic for con-
versation. When two persons meet in the morning the first question asked is,
“ How have you found the zancudos during the night?’

“This is the place to mention the geographic distribution of these insects
which shows quite remarkable phenomena. It does not appear to depend solely
upon the heat of the climate, upon the excess of humidity, or the thickness of
the forests, but upon the local conditions difficult to characterize. It can be said,
for example, that the torment of mosquitos and zancudos, is not as general in
the torrid zone as is commonly believed. Upon plateaux more than 400 fathoms
higher than the ocean level, on very dry plains distant from the banks of great
rivers, for example at Cumana and at Calabozo, there are not obviously more
mosquitos than in the most civilized part of Europe. Their number becomes
enormously increased in Neuva Barcelona, and, more to the west, upon the coast
which extends towards Cape Codera. Between the little port of Higuerote and
to the mouth of the River Unare the unfortunate inhabitants have the custom
of stretching themselves upon the ground and passing the night covered with
earth 3 or 4 inches thick, leaving out only the head, which they cover with a
handkerchief. One still suffers from the bite of the insects, but in so much less
degree that it can be easily borne, in descending the Orinoco from Cabruta
towards Angostura, and in going up from Cabruta towards Uruana, between the
vth and 8th degree of latitude. But beyond the mouth of the Arauca River,
after the Straight of Baraguan is passed, the scene changes constantly. Beyond
this point there is no longer any repose for the traveller. If one remembers his
Dante he believes that he has entered the citta dolente, and he will believe he can
read upon the granite rocks of Baraguan the memorable lines of the third canto:

Noi sem venuti al luogo, ov’i’ t’ho detto
Che tu vedrai le genti dolorose.

“ The lower layers of the air, from the earth up to 15 to 20 feet in height, are
filled with venomous insects like a condensed vapor. If one places himself in
an obscure place, as, for example,'in the grottos of the cataracts formed by
blocks of granite, and directs his eyes towards the opening, one sees clouds of
mosquitos which are thicker or thinner according as these little animals in
their movements come together or disperse. At the mission of San Borja they
12 MOSQUITOES OF NORTH AMERICA

suffer even more from mosquitos than at Carichana, but at Aturés, and above
all at Maypurés, this suffering reaches its maximum. I doubt whether there is
any part of the earth where man can be exposed to more cruel torments during
the rainy season. In passing the fifth degree of latitude one is somewhat less
bitten, but on the upper Orinoco the bites are more painful because of the heat
and the absolute lack of wind. ;

“€Qne should be in the moon,’ said a Saliva indian to Father Gumilla, ‘ for
in its beautiful and clear light one would be free from mosquitoes.’ These
words coming from a savage are very remarkable. Everywhere this satellite of
the earth is for the American savage the habitation of happiness, the country of
abundance. The Eskimo who counts among his riches a plank or tree trunk
thrown by the waves upon a coast deprived of vegetation, sees in the moon
plains covered with forests. The indians of the forests of the Orinoco see bare
fields in which the inhabitants are never bitten by mosquitoes.

“ Going further towards the South where the system of brownish yellow river
waters begins, which are generally called black waters, upon the banks of the
Atabapo, of the Temi, of the Tuamini, and of the Rio Negro, we enjoyed a repose,
I had almost said an unexpected happiness. These rivers run through thick
forests like the Orinoco, but the Nemocera and gnats, and the crocodiles as well,
avoid the neighborhood of the black waters. Are these waters, a little colder and
chemically different from the white, unsuitable for the larve and nymphs of
the Nemocera which must be considered as true aquatic animals? Some small
rivers, which are dark blue or yellowish brown, like the Toparo, the Mateveni,
and the Zama, are exceptions to the general rule of the absence of mosquitos near
black waters. These three rivers swarm with them, and even the indians discuss
the problematical causes of this phenomenon. In descending the Rio Negro
we breathed freely at Maroa, at Vavipe, and at San Carlos, villages situated on
the borders of Brazil. But this amelioration of our condition was very short, for
our sufferings recommenced when we entered the Cassiquiare. At Esmeralda, at
the eastern extremity of the upper Orinoco, where the country known to the
Spaniards ends, the clouds of mosquitos are almost as thick as in the Grand
Cataracts. At Mandavaca we found an old missionary who told us with an air of
sadness that he had passed his twenty years of mosquitos in America. He told
us to look at his legs in order that we might be able to tell the people some day
across the sea what the poor monks suffer in the forests of the Cassiquiare. As
each bite leaves a little brownish black spot, his legs were so speckled that one
could with difficulty see the whiteness of his skin between the spots of coagulated
blood. While the insects of the genus Simulium abound on the Cassiquiare,
which has white waters, the Culex or zancudos are proportionately rare; one
hardly encounters them, whereas on the rivers which have black waters, on the
evel and the Rio Negro, there are generally many zancudos and no mos-
quitos....

“T have just shown according to my own observations that the geographic
distribution of venomous insects varies according to whether the water is white
or black, and it is much to be desired that a learned entomologist should study
upon the spot the specific differences between these criminal insects which play
in the torrid zone, in spite of their minute size, a very important part in the
economy of nature. What appears to us very remarkable, and it is a fact known
to all the missionaries, is that the different species do not associate, and that at
different hours of the day one is bitten by distinct species. Each time the scene
changes, and when, according to the naive expression of the missionaries, other
insects mount guard, one has some moments, even a quarter of an hour, of rest.
The insects which disappear are not immediately replaced in the same number
by those that succeed them. From half past six in the morning until five o’clock
HUMBOLDT ON BITING DIPTERA 13

in the evening the air is filled with mosquitos, which are not, as has been stated
in some travellers’ stories, of the shape of our European gnats, but of that
of a little fly. These are the Simuliums. . . . Their bite is as painful as that of
Stomozys. It leaves a little reddish brown spot which is very excruciating and
is the extravasated and coagulated blood where the beak has pierced the skin.
An hour before the sun sets these creatures are replaced by a species of small
gnat called tempraneros (one which shows itself early) because they appear also
at sunrise ; their presence lasts one hour and a half; they disappear between six
and seven o’clock, or, as they say here, after the Angelus. After some minutes
of sleep one is bitten by the zancudos, another species of gnat with very long
legs. The zancudos, whose beak forms a piercing sucker, causes the sharpest
pain and an inflammation which lasts several weeks. Its song is like that of
our European gnat, but it is stronger and more prolonged. The indians claim
to recognize the zancudos and the tempraneros by their song; these latter are
true twilight insects, while the zancudos are nocturnal and disappear towards
sunrise.

“In the journey from Carthagena to Santa Fé de Bogota we have observed
between Mompox and Honda, in the valley of the Rio Grande de la Magdalena,
zancudos filling the air from eight o’clock in the evening until midnight, dimin-
ishing about midnight and hiding themselves three or four hours, and return-
ing in clouds with a devouring appetite about four o’clock in the morning.
What is the cause of these alternations of movement and repose? Are these
animals tired by a long flight? On the Orinoco it is very rare to see true day
gnats, while on the Magdalena one is bitten day and night except for about
two hours at midday. The zancudos of the two rivers are without doubt of dif-
ferent species. Are the eyes of one of these species affected by the light of the
sun more than the eyes of the other species? . . .

“ At a time when they had not yet studied the geography of animals and
plants they often confounded the analogous species of different climates. They
thought that in Japan, in the Andes and at the Strait of Magellan the pines,
the Ranunculus, the deers, rats, and the Nemocera were the same as those of
Europe. Celebrated naturalists have thought that the gnat of the torrid zone
was the same as the gnat of the European marshes, only more vigorous, more
ferocious, and more dangerous under the influence of a burning climate. This
opinion is very erroneous. I have examined and described with care upon
the spot the zancudos with which one is most tormented. On the rivers of
Magdalena and Guayaquil there are five very distinct species. Latreille, the
foremost entomologist of the century, has been good enough to revise the detailed
description of these little animals, which I will give in a note.

[Here follow the Latin descriptions of the following new species: Culex cyanopen-
nis, C. lineatus, C. ferox, C. chloropterus, and C. maculatus.]

“The species of Culex of South America generally have the wings, the
thorax and the feet bluish and striped, giving a metallic effect from the mingling
of spots. Here, as in Europe, the males, which are distinguished by their plu-
mose antenne, are extremely rare, and one is never pierced except by the females.
The preponderance of this sex explains the immense increase in numbers of in-
dividuals, each female laying several hundred eggs. In traveling up one of the
great rivers of America, one notices that the appearance of a new species of
Culex announces the proximity of a new tributary. To cite an example of this
curious phenomenon, Culex lineatus, which belongs to the Cafion of Tamalamé-
que, is noticed in the valley of the Rio Grande de la Magdalena only at a spot
north of the juncture of the two rivers. It extends up but not down the Rio
Grande. Itis in the same way that upon a principal vein the appearance of a
new substance in the vein rock indicates to the miner the neighborhood of a
secondary vein joining the first.
14 MOSQUITOES OF NORTH AMERICA

“In recapitulating the observations just indicated, we see that in the tropics
these insects do not extend upon the slope of the Cordilleras toward the tem-
perate region where the mean heat is below 19 to 20 degrees C.; that with only
a few exceptions they avoid rivers with black waters, and dry and deforested
localities. On the upper Orinoco the atmosphere swarms with them much
more than on the lower Orinoco, because in the first region the river is bordered
by thick forests and because the borders of the forest are not separated from
the river by extensive arid plains. With the diminution of water and the de-
struction of the woods the mosquitos will diminish in the new world; but the
effects of these changes are as slow as the progress of agriculture. The towns of
Angostura, of Nueva Barcelona, and of Mompox, where, by a lack of police
supervision, the streets, the squares, and the interior of the courts are covered
with brush, are sadly celebrated for their abundance of zancudos.

“ The people born in the country, whether they are whites, mulattoes, negroes,
or indians, all suffer from the bite of these insects ; but, just as the extreme cold
does not render the north of Europe uninhabitable, the mosquitos do not deter
men from establishing themselves in countries where they abound if these
countries, by their situation and their government, offer resources to agriculture
and to industry. The inhabitants pass their lives complaining of the plague, of
the insufferable torment of flies ; but, in spite of these continual complaints, they
none the less seek by preference the commercial cities of Mompox, of Santa
Marta, and of Rio la Hacha. Such is the power of adaptation to evils con-
tinually suffered, that the three missions of San Borja, of Aturés, and of Es-
meralda, where, to use the hyperbolical expression of the friars, there is less
air than mosquitoes, would become, without doubt, flourishing cities if the
Orinoco offered to the colonists the same advantages for exchange of productions
as the Ohio and the lower Mississippi. The abundance of venomous insects
retards but does not entirely stop the progress of population ; it does not prevent
the whites from establishing themselves there where the commercial and politi-
cal condition of the country promises real advantage. . . .”

[Here follows an account of the chigoe (Sarcopsylla penetrans) |:

“One of the most barbarous of the tribes of the Orinoco, the Otomaques,
know the use of mosquito bars made of palm fibers. We have seen that at
Higuerote the people of color sleep covered with earth. In the villages of the
River Magdalena the indians often invited us to lie down with them under the
skins of cattle, near the church, in the middle of the plaza, where they brought
together all the cows of the vicinity. The proximity of the cattle gave some
repose to the men. The indians of the upper Orinoco and of the Cassiquiare,
seeing that Monsieur Bonpland could not prepare his plants on account of the
continual torment of mosquitos, made him enter their ovens or hornitos. Thus
they call their little rooms without doors or windows, which they enter on their
bellies through a very low opening ; then by a fire of damp brush which produces
much smoke they succeed in driving out the insects through the opening. The
absence of mosquitos is purchased very dearly by the excessive heat of the
stagnant air and by the smoke of the torch of copal which lights the oven while
one remains in it. Monsieur Bonpland dried, with a courage and a patience
ee of eulogy, hundreds of plants, shut up in these bake-houses of the
indians.

“ The pains which the natives take in order to lessen the annoyance by insects
sufficiently proves that, in spite of the different organization of the dermal
system, the copper-colored man is as susceptible to the bites of mosquitoes as
the white man, but, as we have elsewhere stated, the pain appears less great and
the bite is not followed by the swelling which follows without interruption
MOSQUITO LOCALITIES 15

for several weeks, and which increases the irritability of the skin, and which
throws persons with delicate complexion into that feverish condition which
always accompanies irruptive maladies. Whites born in equinoctial America,
and Europeans who have lived a long time in the missions on the borders of the
forests and of the great rivers, suffer much more than indians, but infinitely less
than Europeans recently landed. It is not, then, as some travelers say, the thick-
ness of the skin which renders the bite more or less painful at the moment it is
experienced ; it is not on account of the particular character of the skin that the
swellings and the inflammatory symptoms are less with the indians; it is upon
the nervous irritability of the dermal system that the degree and the duration of
the trouble depends. This irritability is increased by very warm clothes, by
the use of alcoholic liquors, and by the habit of scratching the wound; finally,
and this physiological observation is the result of my own experience, by baths
taken at too short intervals. In places where the absence of crocodiles allows
one to enter the river we have observed that the immoderate use of baths, while
allaying the pain of old zancudo bites, rendered us much more sensitive to new
bites. If one bathes more than twice a day one gets his skin into a state of
nervous irritability of which no one in Europe can form any idea. One would
say that all of his sensitiveness was in his skin.

“ As the gnats pass two-thirds of their life in the water, it is not surprising
that in forests traversed by great rivers these injurious insects become more rare
in proportion as one leaves the river. They seem to prefer to remain near places
where they have bred and where they are to lay their eggs. As a matter of fact
the savage indians become accustomed to mission life with greater difficulty
since in the Christian villages they find a torment which they did not know in
their own homes in the interior. We have seen at Maypurés, at Aturés, and at
Esmeralda that the indians fled to the forests solely from fear of mosquitoes.
Unfortunately all the missions of the Orinoco, from their very beginning,
have been too near the banks of the river. At Esmeralda the inhabitants assured
us that if the village had been placed in one of the beautiful plains which sur-
round the high mountains of Duida and of Maraguaca, they would have breathed
freely and would have enjoyed some sleep. The ‘great cloud of mosquitos’
(this is the expression of the friars) is found only upon the Orinoco and its
tributaries. This cloud grows less in proportion as one leaves the rivers. . . .

“TJ have learned that these little insects make migrations from time to time,
like the monkeys that live gregariously. At the beginning of the rainy season
certain species, by which we have not yet been bitten, are found in certain
places. We have been informed that on the Rio de la Magdalena, at Simiti, they
know no other Culex than the jejen. One can pass the night there peacefully,
for the jejen is not a nocturnal insect. Since 1801 the large gnat with blue
wings (Culex cyanopterus) has become so abundant that the poor inhabitants of
Simiti do not know how to obtain a peaceable nap. On the swampy canals of
the island of Baru, near Carthagéna des Indes, there is a little whitish fly known
as the cafafi.* It is scarcely visible to the naked eye, and causes very painful
swellings. It is necessary to wet the mosquito bars in order to prevent the cafaft
from working through them. This insect, fortunately rare elsewhere, comes up
in January by the canal to Morales. When we were in this village in the month
of May we found Simulwum and zancudos, but more of the jejen.

“ Slight changes in nourishment and in climate appear to change the activity
of the poison in the same species of gnats or mosquitoes. On the Orinoco the
most voracious insects are those of the Grand Cataracts, of Esmeralda and of
Mandavaca. On the Rio de la Magdalena Culex cyanopterus is the one feared

 

*“ Perhaps a Culicid.” [This is very probably a Culicoides, H., D. & K.]
16 MOSQUITOES OF NORTH AMERICA

above all at Mompox, at Chilloa, and at Tamalaméque. It is here that it is the
largest and strongest, and here its legs are blacker. One can hardly help laugh-
ing when one hears the missionaries dispute about the size and ferocity of the
mosquitos on different parts of the same river. In the midst of a country where
they are ignorant of what is going on in the rest of the world this is the favorite
subject for conversation. ‘How sorry I am for you!’ the missionary of the
Raudales on our departure said to the missionary of the Cassiquiare. ‘ You are
alone just as I am in this country of tigers and of apes; fishes where I live are
rarer than here; the heat there is greater, but as to the flies, I can boast that with
one of mine J can beat three of yours.’ : :

“ This voracity of insects in certain places, this avidity with which they attack
man,* this activity of the venom, variable in the same species, are remarkable
facts, but they find their analogy with some of the larger animals. The croco-
dile of Angostura pursues man, while one can bathe peacefully at Nueva Barce-
lona in the Nevari River in the midst of these carnivorous reptiles. The jaguars
of Maturin, of Cumanacoa, and of the Isthmus of Panama are cowardly com-
pared with those of the upper Orinoco. The indians know very well that the
monkeys of such and such a valley are easily domesticated, while others of the
same species, caught elsewhere, will die of hunger rather than submit to slavery.

“The people in America form ideas concerning the health of climates and
concerning pathological phenomena, just as the savants of Europe do, and these
ideas, just as with us, are diametrically opposed to one another according to
the provinces into which the new continent is divided. On the Rio de la Magda-
lena the abundance of mosquitos is regarded as a nuisance, but very healthy.
‘These animals,’ say the inhabitants, ‘ bleed us slightly, and in an excessively
warm country, preserve us from the tabardillo, from scarlet fever, and other in-
flammatory maladies.” On the Orinoco, the banks of which are very dangerous
to health, the sick people accuse the mosquitos of all the diseases that they have.
* These insects are born in corruption and increase it; they inflame the blood.’
It is useless to deny this poner belief which considers mosquitos as acting in
a salutary way by local bleeding. Even in Europe the inhabitants of swampy
countries do not ignore the fact that insects irritate the dermal system. Far
from diminishing the inflammatory condition of the skin, the bites increase it.

“The abundance of gnats and mosquitos characterizes unhealthy countries
only when the development and multiplication of these insects depends upon
the same causes which give birth to miasmas. These injurious animals love a
fertile soil covered with vegetation, with stagnant pools, and moist air which is
never agitated by the wind. They prefer, in place of bare spots, shade, that
degree of light, of heat, and of humidity, which all favor the action of chemical
affinities and accelerate the putrefaction of organic substances. Do the mos-
quitos themselves add to the unhealthiness of the atmosphere? When one
thinks that, at an elevation of three or four fathoms, a cubic foot of air is often
peopled by a million winged insects and that these have within them a caustic
and poisonous liquid—when one remembers that several species of Culex are
from the head to the end of the body (without counting the legs) 1-4/5 lines
long—when one considers finally that in this swarm of gnats and mosquitoes,
spread like a cloud in the air, there are a great number of dead insects carried by
the force of the ascending current and by the side currents which are caused by
the unequal heat of the soil—one asks if the presence of so much animal matter
in the air does not give birth to certain miasmas. I think that these substances

 

* “ How surprising is this voracity, this appetite for blood on the part of littl h
teed Donnas ae me Mee van five Yn op pimost vaninhabited country ! x what eid
‘ou ere,’ the creo
there are only crocodiles covered with scaly skin and hairy cionkeyin im: paraing ‘planes: where
INSECT TORMENTS 17

act differently upon the atmosphere than soil and dust; but it will be prudent to
make no definite assertions upon this subject. Chemistry has not yet solved any
of the numerous mysteries of the unhealthiness of the air. It has taught us only
that we are ignorant of many things which we thought we knew fifteen years
ago, thanks to the ingenious dreams of the ancient eudiometry.

“What is less uncertain, and confirmed, so to speak, by daily experiences, is
that on the Orinoco, the Cassiquiare, the Rio Caura, and everywhere where the
air is very unhealthy, the bite of the mosquitos increases the disposition of the
organs to receive miasmatic impression. When during whole months one is ex-
posed night and day to the torment of insects, the continual irritation of the
skin causes febrile movements and depresses the functions of the stomach by
the effect of the antagonism, so long known, between the dermal system and the
gastric system. One begins to digest with difficulty; the inflammation of the
skin brings about abundant perspiration ; one can not quench his thirst; and
to his always increasing impatience follows, with persons of weak constitution, a
condition of low spirits during which all the pathogenic causes act with force.
Today it is not the dangers of navigation in little canoes, it is not the savage
indians, or the serpents, the crocodiles, or the jaguars, which makes Spaniards
fear the voyage up the Orinoco; it is, as they say naively, ‘the sweats and the
flies’ Let us hope that man, in changing the surface of the earth, will little by
little bring about a change in the constitution of the atmosphere. The insects
will diminish when the old trees of the forest will have disappeared, and one
will see in these desert countries the rivers bordered with villages, the plains
covered with pastures and cultivated fields.

“ Whoever has lived a long time in countries infested by mosquitos will
have proven, as we have, that there is no radical remedy against the torment of
insects. Indians covered with onoto, with bolary earth, or with turtle oil,
are every instant slapping their shoulders, their sides, their legs, almost as
though the body had not been painted. It is doubtful in general whether paint-
ing is a relief—certainly no great relief. Europeans recently arrived on the
Orinoco, on the Rio de la Magdalena, on the Guayaquil or the Chagres rivers (I
mention the four rivers where the insects are the most numerous) at first cover
the face and the hands. They soon find the heat too great, and they are tired of
being completely inactive, and end by uncovering. Persons who do not wish to
do any kind of work during the navigation of the rivers can bring from Europe
an especial kind of clothing in the form of a sack under which they can rest
hidden, opening it only every half hour. This sack should be held open by
whalebone hoops, for a simple mask and gloves would be hardly bearable. Sleep-
ing upon the earth, upon skins or in hammocks, we have not been able in the
Orinoco region to use mosquito bars. A mosquito bar is useful only when it
forms about the bed a tent so well closed that there is not the least opening by
which a mosquito can enter. This condition is very difficult to bring about, and
often one is forced (for example when going up the Rio de la Magdalena, where
they travel with these mosquito bars), in order not to suffocate with heat, to get
out from under his bar and to walk in the open air. A mild wind, smoke, and
strong odors afford almost no relief in the places where these insects are very
numerous and very voracious. It is wrongly stated that these little insects avoid
the odor of the crocodile. We were horribly bitten at Bataillez on the road from
Carthagéna des Indes to Honda, while we were dissecting a crocodile eleven
feet long and which infected the whole atmosphere of the neighborhood. The
indians recommend the exhalation of burnt cowdung. When the wind is very
strong and accompanied by rain the mosquttos disappear for some time. They
bite the most cruelly on the approach of a storm, and especially when the thunder
is not followed by showers.
18 MOSQUITOES OF NORTH AMERICA

“ Byerything which moves about the head or the hands helps to chase the
insects away. ‘The more you move, the less you are bitten, say the mission-
aries. The zancudo buzzes a long time before alighting, but when it has gained
confidence and has once commenced to insert its sucker and to suck blood one
can touch its wings without frightening it. At this time it holds its two hind
legs in the air, and if, without bothering it, one lets it suck its fill there is no
swelling and no pain. We have often tried this experiment upon ourselves in the
valley of the Rio de la Magdalena on the advice of the natives. One asks oneself
whether the insect only injects the poison at the moment when it is frightened
away, or if it sucks back the poison when it is allowed to suck as much as it will.
I am inclined to the latter opinion, for, in allowing Culex cyanopterus to peace-
ably bite the back of my hand, I noticed that the pain, very strong in the begin-
ning, diminished as the insect continued to pump up the blood. It ceased
absolutely at the moment when the sucking was finished. I tried also the experi-
ment of wounding my skin with a pin and of rubbing the puncture with crushed
gnats, but no inflammation followed. The irritating liquid of the nemocerous
insects, in which chemists have not yet recognized any acid property, is con-
tained, as with the ants and other hymenopterous insects, in special glands, and
it is probably too dilute and in consequence too weak if one rubs the skin with
all of the crushed insect.”

If, in the above account, one has kept in mind that by the word “ mosquito”
Humboldt designated Simulium, it will be seen that he clearly distinguished
between the blood-sucking flies belonging to different families.

In the account which follows, of the abundance of mosquitoes in southern
Russia, by Jaeger, the Culicids and Simuliide were evidently not differen-
tiated. Thus the statement of the mosquitoes entering the noses, mouths and
ears of cattle and of causing the death of many of these animals, clearly applies
to the Simuliide, the ravages of which, in that country, are well known. The
account is nevertheless of interest.

“ When traveling some years ago in the country of the Czernomorzi, or Cos-
sacks of the Black Sea, we observed before each house of the different slanilzas
or villages, of the Cossacks, large heaps of half dried manure ignited and smok-
ing, which our driver informed us was for the purpose of keeping off the mos-
quitoes. Toward evening, on a very hot June day, we ascended the right bank
of the muddy and slowly-running River Kuban, on the left bank of which the
independent Circassia stretched out before us, when suddenly swarms of small
mosquitoes covered us, our servant, and driver, and horses, lighting upon us in
lumps an inch thick, and, in spite of all the covering we could hastily throw
over us, tormenting us excessively with their bites.

“On the road, at a distance of every four or five versts (three or four English
miles), we found a military post of about a dozen Cossacks, keeping themselves
and their horses under ground, except one sentinel, who was standing upon a
scaffold twelve feet high, in order to watch any inimical movements of the
Circassians, to repulse their attacks, and, in case of one, to give notice of it to
the two nearest posts by means of the ancient Persian telegraph, viz. : by igniting
a bundle of straw, which was then fastened to the top of a high pole and elevated.
At midnight our misery reached its climax. Though covered with a wide cloak,
the mosquitoes entered every opening, and inflicted upon us such painful wounds
that our faces were so swollen we could scarcely recognize one another. To our
joy a large camp-fire was seen at some distance, which, according to the driver’s
assurance, was the post-station, where fresh horses could be had. We arrived at
BITING GNATS OF SOUTHERN RUSSIA 19

the spot, and with great precipitation left the carriage, running in haste to the
fire, near which a large dog was howling and running as if mad; the horses, as
soon as they were unharnessed, sprang into the fire to get rid of the mosquitoes,
and only with difficulty could they be removed to the subterranean stable, where
the postmaster, a half-invalid officer of the army, with some men and a number
of imperial horses, resided. The officer immediately ordered fresh horses for
us, and, looking from under a very heavy covering at our pitiful condition, told
us to hurry on, and by daybreak we should arrive at the next station, where we
could find comfortable houses and be relieved from the attacks of mosquitoes.
In less than five minutes the horses were harnessed, and the Russian word
Boshoal, ‘ Go on,’ from the commander to the new driver, was music to our ears.
When we arrived at the next station we stopped at the first house, the owner of
which was a captain of the Cossacks, who received us with the usual hospitality,
inborn in the Russians of all grades, and entirely unknown in any part of Europe
or America, Poland and Hungary excepted. The captain conducted us into a
well-furnished, comfortable room, assisted us to undress and get to bed, and
from time to time applied wet cloths to our swollen face and body, until a pro-
found sleep temporarily relieved our excruciating pains. The same care was
taken of our servant, who, in the madness caused by his sufferings, attempted
to shoot himself that he might be out of misery, but was prevented by two
athletic Cossacks, and watched and nursed until he, too, was relieved by sleep.
It was not until after a week of suffering that the fever and inflammation sub-
sided so that we could open our eyes. .

“ As the Cossacks of the Black Sea are no agriculturists, but derive their sub-
sistence from their numerous herds of horses, oxen, sheep, goats, and hogs, they
suffer immensely at times from the ravages of the mosquitoes. Although they
are fortunately not seen every year, these blood-suckers may be considered a real
Egyptian plague among the herds of these Cossacks ; for they soon transform the
most delightful plains into a mournful, solitary desert, killing all the beasts,
and completely stripping the fields of every animated creature. One can not
look upon the spectacle without pity when he sees the poor cattle exhibiting so
much terror at the approach of these innumerable swarms of mosquitoes, whole
herds hurrying home for shelter, running as if mad, and often, in their fright,
plunging into the river and being drowned. Thousands of these insatiate tor-
mentors enter the nostrils, ears, eyes, and mouth of the cattle, who shortly after
die in convulsions, or from secondary inflammation, or from absolute suffoca-
tion. In the small town of Elizabethpol alone, during the month of June, thirty
horses, forty foals, seventy oxen, ninety calves, a hundred and fifty hogs, and four
hundred sheep, were killed by these flies.”
20 MOSQUITOES OF NORTH AMERICA

EARLY ACCOUNTS OF THE BIOLOGY AND STRUCTURE OF
MOSQUITOES.

Although simple lenses were known in very ancient times, and although many
interesting and important observations were made with these simple lenses, it
was not until the invention of the compound microscope, at the end of the six-
teenth century and its development during the seventeenth century, that com-
petent observations began to be made upon the very small animals. In that
century, and especially towards its close, a number of patient workers examined
with these new instruments the small, common forms of life about them and
discovered many most interesting and, to them, almost miraculous facts con-
cerning their microscopic appearance and concerning their habits and methods
of life.

The organization of the proboscis of the mosquito and its manner of function-
ing were the objects of especial interest to the early investigators with lens and
microscope. The work of some of these anatomists, when we consider the in-
struments at their command, was most remarkable, and while faulty in the light
of our present knowledge, gives testimony to the enthusiasm and devotion of
these men. It would lead too far to enter into a discussion of the early investi-
gators. A brief account of them, and their relation, to the facts as found by
modern workers, is given by Dimmock, while Meinert, in his “ Fluernes Mund-
dele,” gives a very complete account of these early researches on the composition
of the mosquito’s proboscis. There were naturally enough discrepancies as to
the component parts of the proboscis, but Swammerdamm, in his work of 1669,
had already determined them correctly.

Many of the earlier works, like Barth’s “ De Culice dissertatio,” contain little
that is original, but quote, as was then the fashion, at great length from the
writings of ancient authors.

Robert Hooke, in his “ Micrographia, or Some Physiological Descriptions of
Minute Bodies made by Magnifying Glasses, with Observations and Inquiries
thereupon,” published in 1665, treats so interestingly of the life-history of the
mosquito that we quote from it at some length. He calls the larva

Oa ate small scaled or crusted animal which I have often observed to be gen-
erated in Rain water. . . . It is supposed by some, to deduce its first original
from the putrifaction of Rain-water, in which, if it have stood any time open to
the air you shall seldom miss, all the Summer long, of store of them striking
to and fro.”

A description of the larva follows, with constant reference to the plate, with
its crude but characteristic figures, and observations on the internal structure
and the circulation of the “bloud.” Its mouth was “ pretty large” and “ con-
trived like those of Crabs and Lobsters, by which, I have often observed them to
feed on the water, or upon some imperceptible nutritive substance in it... . . e

“Both its motion and rest is very strange and pleasant . . . for, where it
ceases from moving its body, the tail of it seeming much lighter then the rest of
its body, and a little lighter then the water it swims in, presently boys it up to
the top . . . where it hangs suspended with the head always downward... .
the hanging of these in this posture, put me in mind of a certain creature I have
seen in London that was brought out of America, which would very firmly sus-
TRANSFORMATION OF MOSQUITO 21

pend it self by the tail . . . and was said to sleep in that posture, with her
young ones in her false belly. . . .”
He kept some in a glass of rain-water and observed their transformation to

pupa and adult and described the pupa, and also, very accurately, the emergence
of the adult. He philosophizes:

_ “Thave been the more particular, and large in the relation of the transforma-
tion of divers of these little Animals which I observed, because I have not found
that any Authour has observ’d the like; and because the thing it self is so strange
and heterogeneous from the usual progress of other Animals, that I judge it may
not onely be pleasant, but very usefull and necessary toward the completing of

Natural History.”

He speculates upon what he has seen, and wonders if, after all, the varied
organisms supposed to come from putrefaction may not develop from eggs
dropped in the water by the parent. He had an idea that the gnat’s eggs might
possibly be ejected in the air—*. . . for it seems not very improbable, but that
those small seeds of Gnats may (being, perhaps, of so light a nature and having
so great a proportion of surface to so small a bulk of body) be ejected into the
Air, and so, perhaps, carried for a good while too and fro in it, till by the drops
of Rain it be washed out of it.’ He believes, speaking of metamorphoses of
insects, that were men “ diligent observers, they might meet with multitudes ”
of instances.

He describes, in another place, a female mosquito, and speaks of letting it bite

his hand, and of watching its body swell with the blood,
“ making it appear very red and transparent, and this without further pain than
whilst it was sinking in its proboscis . . . a good argument that these creatures
do not wound the skin and suck the blood out of enmity and revenge, but for
meer necessity and to satisfy their hunger.”

The copper plates of Hooke’s work were republished with new text by an
anonymous writer in 1745, under the title “ Micrographia Restaurata.” The
self-satisfied complacency of this edition is in sharp contrast to the intimate
style of the original work. It alternately apologizes for Hooke’s short-comings
and exalts the present-day perfection of scientific knowledge, brevity and direct-
ness of speech. Under our treatment of the mosquito larva the accounts of
Swammerdamm, Réaumur and Hooke are mentioned. The unknown com-
mentator, however, draws upon the paper by J. J. Wagner, “ De Generatione
Culicum ” (Ephem. Acad. Nat. Curios., 1684), for his description of the life-
history. This account, which in reality treats of one of the Chironomide, states
that the female gnat dips its tail into the water and lays a gelatinous mass of
eggs attached to a water weed—that they hatch into small reddish maggots which
sink to the bottom of the water, where they form cases in which they live for a
time and later come forth and become pup and mosquitoes.

John Swammerdamm, in his Historia Insectorum Generalis, Utrecht, 1669
(in English in Book of Nature, London, 1758, pp. 153-159), shows plainly that
he had carefully studied mosquitoes with the microscope, and describes the larva
very carefully (complimenting Robert Hooke’s admirable figures in his Micro-
22 MOSQUITOES OF NORTH AMERICA

graphia) and stating that the mosquito larva holds its position at the surface of
the water because its tail never becomes wet, supposing it to be oily. He de-
scribes the transformation to the pupa stage, carefully describes the pupa stage
and the transformation to adult, and gives a long description of the adult, in-
cluding the mouthparts, determining correctly the number of sete in the
proboscis. He thought, however, erroneously, that in biting the mosquito was
able to protrude the sete from the end of the sheath, without flexion of the latter.

P. Bonanni, in a curious work entitled “ Observationes Circa Viventia,” etc.,
Rome, 1691, in which he considers the methods of reproduction of many dif-
ferent kinds of lower animals with especial reference to spontaneous generation,
gives very good figures of the larva, pupa, and adult, and of the wing-scales, of
a Culex. The drawing of the adult is obviously traced from Swammerdam and
printed reversed. The larva and the pupa are different from the Swammerdam
drawings, and may have been drawn originally from specimens under obser-
vation.

P. P. San Gallo, “ Esperienze intorno alla generazione dele zanzare” (Ephem.
Acad. nat. Curios., 1712, cent. 1 and 2, pp. 220-223, Tab. 1), gives some atten-
tion to the writings of earlier authors, and quotes Pliny, Ammianus Marcellinus,
the Arabian doctor Zacharias Ben Muahammed Ibn Mahmud, and Francisco
Redi. He gives an account of observations made by himself in June, 1679,
upon mosquitoes in breeding-jars. He describes the larva, figures the male and
female adults, and also a larva which is very poorly done.

D. Reviglias, in an article entitled “ De Culicum Generatione,” in the Acta
Acad. Nat. Curios., 1737, T, 4, Obs. 3, p. 420, gives a study of the mosquito’s
beak, and figures very poorly the adults. He gives an illustration of a larva
which is obviously not a mosquito larva, but that of a dermestid beetle which
had found its way under the glass in which the female mosquito had been
confined.

In 1734 Réaumur began the publication of his “Mémoires pour servir 4
V Histoire des Insectes,” and in his fourth volume (1738), has, as his thirteenth
memoir (pp. 573-636), his famous “ Histoire des Cousins ” in which he describes
the entire life-history and structure of Culex pipiens with a wealth of detail
that is almost the despair of modern naturalists—in fact, few modern works
even approach it, if we except Lownes’s classical study of the anatomy of the
blow-fly. The observations of Réaumur were so full, and his authority was ac-
cepted as so all-satisfying, that the publication of this memoir practically put a
stop, for a hundred and fifty years, to all further studies of the aspects of mos-
quito life. The general works published in that period derived their informa-
tion concerning mosquitoes from the standard observations of Réaumur, and
this, it may parenthetically be stated, holds for a number of the other studies
made of common species of insects by the famous French author. And this
confidence in him has in the main been fully justified, although here and there a
different interpretation is possible in the light of later knowledge, especially in
physics and in microscopic interpretation. While it is not strange that his
accurate observations on the transformations and structure should have been
REMARKABLE EARLY WORK 23

followed by later writers, frequently without credit, it is a curious fact that the
duration of the different stages as ascertained by him in Paris prior to 1738
should have been slavishly quoted in standard works as the duration of the stages
of practically all mosquitoes. Down to the publication of the life-history of
Culex pipiens in America by one of us in 1896, the data established by Réaumur
in a different part of the world have been considered as applicable to all mos-
quitoes. The frequent references to Réaumur by Miall in his admirable book
entitled “The Natural History of Aquatic Insects,” published in London in
1895, shows that even at the present time, and with the latest instruments and
methods of research, the French author practically remains standard.

Most of the accounts of the early writers are based on material obtained from
rain-water barrels or like receptacles and consequently treat of the same species
of mosquito, the common Culex pipiens, or at most closely related forms. As
we have already mentioned, the transformation so faithfully described by
Wagner was not that of a mosquito but a Chironomus, a midge quite similar in
general appearance. A Parisian naturalist, Joblot, in 1754, was the first to
describe the larva of Anopheles in “Observations d’histoire naturelle, faites
avec le microscope, sur un grand nombre d’Insectes.” We have not seen this
work.

The Swedish naturalist, De Geer, in the sixth volume of his “ Mémoires,”
published in 1776, gives a chapter on mosquitoes with many interesting original
observations. He had already determined that the adults are by no means
restricted to a blood diet. He states that they visit various flowers to suck honey
and that he had found them particularly abundant on the blooms or catkins of
the willow. He gives an excellent description of the mating habits and of the
swarms of dancing males. He appears to have been the first to observe the
larvee of the species of Aédes which develop in the snow-water of early spring
and which are the predominating mosquitoes in northern countries. “It is in
the stagnant waters of ponds and swamps that the larve of mosquitoes live, and
which swarm with them in the spring and summer; but it is principally during
the first season, and in those in which the ice has melted, that one finds them in
abundance.” Very naturally De Geer confused the species of Culex and Aédes,
and io complete his description of the life-history he drew upon Réaumur, re-
peating his statements for Culex pipiens regarding the eggs, the succession of
generations and the mode of hibernation. The Aédes he appears principally to
have had under observation have but one brood and lay their eggs singly, facts
which have only been determined within the present century and which will be
found discussed in our general account of the habits of mosquitoes.

The German miniature painter Kleemann published, in continuation of
Rosel’s “ Insecten-Belustigungen ” a remarkable work under the title “ Beytrage
zur Natur- und Insecten-Geschichte.” The work in some respects even exceeds
that of the famous Réaumur. Thus we find in the chapter on mosquitoes (vol.
1, 1792, pp. 125-148, plates 15 and 16) that, while he gives the observations of
Réaumur and others, he has verified them by observation, adding to them, and
in some cases criticizing them. His plates, particularly the one illustrating the
24 MOSQUITOES OF NORTH AMERICA

life-history of Culex pipiens, are wonderfully characteristic, exquisite in execu-
tion, and stand unsurpassed to this day. Like De Geer, he found the Aédes
larve which appear in the early spring in snow-water, although, like that
author, he failed to realize that they were different from the rain-barrel mos-
quitoes, assuming that they were the first of a series of generations produced
through the warmer months. He is quite pardonable in this, as the error per-
sists with many even to this day.

Kleemann calculated that there could be three generations of mosquitoes
during a season. After speaking of the retarded development of the larvee, when
confined in a small receptacle, he says (free translation) :

“ However, in this year 1762, with long-continued warm spring weather, I
found this out in the following manner: I had already found these worms, full
grown, in a wooden vat in which rain-water had been caught, at the beginning
of June, and soon brought some of them to transformation. On this account I
emptied it out and left it standing for some days without water. Towards the
end of the month, however, I had it again filled with clean water and at the be-
ginning of July found very many mosquito eggs therein, which brood then came
to completion at the beginning of August. Thereupon I emptied the vat once
more and again filled it with clean water, and also found in this, after some days,
mosquito eggs which hatched in the middle of September. Even in October of
this year I have still found mosquito eggs, the worms of which, however, at
present (towards the end of this month) do not incline to transform: therefore
I believe that they will hibernate without food and only transform in the spring;
as I have also found the like full-grown worms already in April and May in the
swamps of the forests; yes, even in March of this year, on a bright day, I have
caught a male mosquito which I could not take for a hibernated one but for one
freshly issued.”

As above stated, the other general accounts of the last century followed
Réaumur, and the life-history of Culex pipiens was not restudied until 1896,
and of other mosquitoes not until several years after this. Since 1900 the whole
civilized world has been turning out mosquito literature, good, bad, and in-
different ; papers descriptive of new species have multiplied, many accounts of
habits have been published, and much space has been devoted to the subject of
internal anatomy, so that since that date the bibliography of mosquito literature
has run into many thousands of titles.
STRUCTURE OF THE ADULT MOSQUITO.
THE HEAD.

The head is more or less globose, inserted upon a slender, flexible neck, a large
part of its surface occupied by the eyes; there is a prominent clypeus, the an-
tenne are long, and the mouthparts consist of a long sucking proboscis and a
pair of palpi, usually considered maxillary, inserted at its base. There are no
ocelli,

THE EYES.

The many-faceted compound eyes are large, in most species almost or quite
contiguous above and beneath. In front the eyes are deeply emarginate to
make place for the insertions of the antennz and the depth of the emarginations
varies with the size and place of insertion of these organs according to the
species or the sex. As the basal joint of the antenne is often much larger in the
male than in the female, in accordance with this the emargination of the eyes
is deeper in that sex.

Aside from the emargination the eyes of the two sexes usually differ somewhat
in shape and those of the female may be somewhat larger than those of the male.
In the culicine tribe the eyes are markedly broadest at the sides and are much
narrowed above the antenne, particularly in the male; beneath they are broad
and may be contiguous in’ their whole width. In the Sabethini the eyes are
nearly as broad behind the antenne as at the sides and the sexual differences are
less marked. In certain genera of this tribe the eyes are broadly contiguous be-
hind the antennz ; in other forms a chitinous wedge is inserted between the eyes
in such a manner that the eyes touch at their hindermost angles and diverge
towards the front. In a curious sabethid from the Philippine Islands, Heiz-
mannia scintillans, the eyes are separated above by a broad strip of chitin,
almost a third the entire width of the head. In the Culicini the eyes, when
contiguous above, are never contiguous along the entire margin. The chitin of
the occipital region is produced wedge-shaped between the eyes ; when this wedge
is small the eyes are contiguous, when large they are separated, the separation
being usually greatest at the broadly rounded hind angles. In this tribe the
median suture of the occiput may be seen continuing forward between the eyes
thus clearly indicating that the intra-ocular wedge belongs to the occiput. In the
Sabethini, as already mentioned, a wedge is inserted anteriorly and the eyes are
approximated at their hind angles.

In addition to the compound eyes there are present a pair of rudimentary or
vestigial eyes. These are situated laterally, close to the hind margin of the
compound eyes. They are covered by the scale vestiture of the cheeks and are
therefore not visible; however, they become plainly visible in a balsam prep-
aration in which the pigment of the eyes has not been destroyed. These vestigial
eyes consist, in fact, wholly of groups of pigment cells; there does not appear to

3 25
26 MOSQUITOES OF NORTH AMERICA

be any modification of the chitin overlying them, and of course there is no trace
of the “rod and cone” structure of the compound eyes. We shall revert to
these vestigial eyes again in our discussion of the eyes of the larva.

THE ANTENNZ.

The antenne are composed of fifteen segments. The basal segment is greatly
reduced and not distinctly visible, and therefore in descriptive work the antennx
are considered as fourteen-jointed.

Child, who demonstrated the presence of the basal rudimentary segment,
states that the antenna is made up of sixteen elements, but he was in error with
the number of joints in the shaft. In all Culicide examined by us the number
of antennal joints, both in the male and female, have been found the same,
fifteen, if one counts the basal reduced joint. The second joint differs from all
the others; it is large, globose, with a cup-shaped hollow on top, and upon the
floor of this hollow the third joint is inserted. In descriptive work this joint is
usually termed the torus. This joint constitutes a highly specialized sense-
organ, generally accepted to be an organ for the perception of sound waves.
Farther on we will give the details of structure of this organ and a discussion
of its functions. The joint differs considerably in size in different species and
in the two sexes. The torus is largest in the male and this sexual difference is
most marked in those species in which the male antenne# are strongly plumose.
The tori are usually naked and smooth; often they are pruinose and sometimes
more or less densely clothed with scales; there may be small scattered hairs
present upon the surface.

The outer thirteen joints constitute the shaft and are slender, more or less
elongate, and cylindrical ; they are more or less pubescent and each bears a whorl
of hairs. The appearance of the shaft, and the details of structure of the com-
ponent joints, differ considerably with the species and groups of species and
particularly in the two sexes.

The simplest form, perhaps, is that which obtains in the females of Culez,
Aédes, Anopheles, and related forms. In these the joints are elongate, cylindri-
cal, subequal, with a whorl of long hairs at the base; the fourth joint (the second
of the shaft) is the shortest, each succeeding joint progressively longer. The
first and the last joints of the shaft differ most from the others. The first joint
of the shaft is longer than the succeeding ones and usually more or less swollen;
it also differs from the others in lacking the basal whorl of hairs and bears in-
stead some irregularly inserted hairs near its middle. The terminal joint is the
longest of the series and has a pointed apex; besides the basal whorl it has a
whorl of sparse hairs just below the tip.

In some forms there is an apical whorl of smaller hairs upon all the joints of
the shaft, but these do not show the regularity of insertion of the basal whorl
of hairs. Besides these coarse hairs of the whorls there are many fine hairs, in-
serted in sensory pits, scattered irregularly over the surface of the joints; they
vary in coarseness and abundance with the species. In addition scales may be
present on some of the joints—particularly the first joint of the shaft is some-
ANTENNZ OF IMAGO 27

times densely clothed with scales, as in Megarhinus and Aédeomyia. The shape
and proportion of the joints differs considerably in different genera. Thus in
Aédeomyia the joints are very short and stout, the second joint of the shaft
hardly longer than broad; the succeeding ten joints are subequal, hardly twice
as long as thick. The opposite extreme is reached in Deinocerites, where the
joints of the shaft are slender and very long.

In a majority of the species the antenne of the male are plumose; that is, the
joints of the shaft are shortened, bringing the whorls of hairs close together, and
the whorls themselves are composed of longer and much more numerous hairs.
The torus, as already mentioned, is larger in the male, and this contrast is
greatest in the forms in which the male antennz are differentiated most. In the
typical plumose antenna the whorls of the first eleven segments of the shaft are
subapical, the basal one bearing a whorl as well as the others. The last two
joints are very long and slender and bear basal whorls of hairs. On all but the
last the slender segment is greatly expanded at the insertion of the whorl in
order to accommodate the numerous, closely crowded hairs; the whorl does not
form a complete circle, but there is a very slight interruption on the outer side.
The first joint of the shaft is much longer than the succeeding ones and it bears
coarse hairs upon the part below the whorl. The short segments, aside from the
whorl, are smooth or nearly so; sometimes very small hairs are present upon the
very short chitinous ring just above the whorl. The two last very long joints are
densely hairy beyond the whorl, the hairs of the penultimate joint are particu-
larly long and thus complete the plumose effect. The last joint is pointed at the
tip, its whorl contains fewer hairs and they are inserted as in the female.

Raphaél Blanchard, in Les Moustiques, pages 45 and 47, states that the
antenna of the female has fourteen joints, that of the male fifteen, following
Ficalbi in this respect. In fact, the number of segments is the same in both
sexes. Ficalbi’s error occurs, as one can readily see by his figure, with the first
joint of the shaft of the male antenna; the parts above and below the whorl are
regarded as separate segments. This was done, apparently, in the attempt to
homologize the antennz of the two sexes and, as the third antennal joint of the
female bears no whorl, it was natural to consider the basal part of the same seg-
ment of the male as a unit, and the part beyond, with the whorl at its base, as
a separate segment.

Many modifications occur in the different genera and species. In the male of
Megarhinus the antenna is remarkably stout and rigid; the first joint of the
shaft is unusually long and very stout, clothed with numerous coarse hairs and
a dense covering of scales; the whorl is apical. In the succeeding ten joints the
whorls are much nearer base than apex, and the apical part of the joints is dis-
tinctly hairy.

In Culex latisquama the antenne of the male are remarkably long, nearly
equaling the considerably lengthened antennez of the female. They are of the
usual plumose plan but there is a lengthening of all the joints; even the two
terminal joints are longer than in the ordinary type and the last joint is the
longest ; the ten shorter subequal joints are from three to four times as long as
28 MOSQUITOES OF NORTH AMERICA

broad and bear the whorl slightly below the middle, the part above the whorl
being pubescent. The hairs of the whorls are unusually long.

In Culiseta the antenne of the males are usually as in the typical Culex males ;
in Culiseta inornatus, however, the male antenne approach in character those of
Culex latisquama, just described. The subequal joints of the shaft have the
part above the whorls lengthened and the hairs of the whorls are less numerous,
so the antenne do not present the usual plumose appearance. Thus it will be
seen that considerable differences in the character of the male antenne may
occur within a genus.

Another striking example of such difference occurs in the genus Uranotenia,
where they are usually distinctly plumose in the male. In U. lowi, however, the
male antennz closely resemble those of the female. In the males of U. sap-
phérina and U. geometrica, with distinctly plumose antennz, the joints of the
shaft are long and slender; the whorls are basal and consist of numerous very
long hairs and the part beyond the whorl bears many, irregularly inserted, long
hairs which give the effect of a secondary whorl; the last two joints are
lengthened, but not to the same degree as in the forms first described; these
joints are coarsely hairy and the whorl on the last one is represented by a few
hairs, inconspicuous among the general pubescence. Thus, in these forms, the
antenne, while distinctly plumose, approach in structure those of the female. In
U. lowti the male antenne are like those of the female. The joints of the shaft
are long, cylindrical, and very coarsely hairy; the whorls are basal and consist
of a few coarse, moderately long bristles; the two last joints are not modified in
the manner of the plumose type and only the last joint is somewhat lengthened.

The mosquitoes of the genera Deinocerites and Dinomimetes are remarkable
for the very great length of their antenne, those of the male even exceeding
those of the female. The joints of the shaft are cylindrical, long and slender,
coarsely hairy, with a basal whorl of but few hairs. The first joint of the shaft
is always very long and differs from the other joints by lacking the whorl-hairs.
In the female of Deinocerites the first joint is three or three and a half times as
long as the one following it and at least fourteen times as long as its own diam-
eter. The other joints are subequal, each successive one becoming slightly
shorter. The antenna of the male Deinocerites closely resembles in character
that of the female but is still longer and more slender. The second joint of the
shaft is nearly as long as the first and the joints beyond shorter slightly in suc-
cession ; the last five to seven joints, however, are about equal. The relative
proportions of the joints differ with the species. There may be a slight thicken-
ing of these last joints, most pronounced in the terminal one, the species differ-
ing in this respect. Thus in Deinocerites troglodytus the last seven joints show a
thickening, while in D. cancer the last joint only is distinctly swollen.

In Dinomimetes the female antenna approaches very closely in character that
of the male Deinocerites. The first four joints of the shaft are greatly elongated,
the second nearly as long as the first, the next two somewhat shorter. The an-
tennz of the male Dinomimetes are very similar but lengthened still more. In
both these genera the whorls are inconspicuous and consist of few and rather
ANTENNAL SENSE-ORGAN 29

short hairs and they are further obscured by the presence of scattered equally
coarse hairs among the general pubescence of the shaft.

The antenne of Dinanamesus are intermediate in character between the forms
just discussed and the ordinary culicine type, both as regards length and the
nature of the hairs.

In the Sabethini the antenne of the two sexes are usually similar and those
of the female may in many cases be characterized as sparsely plumose. In the
genus Joblotia, however, the antennx approach closely the culicine type. In the
female the hairs of the whorls are longer than in the culicines and there is a
crowding of cilia towards the tip of the joints, giving the effect of a small apical
whorl. In the male Joblotia the antenne are densely plumose but differ from
the common type by having the whorls basal and by having the penultimate joint
densely clothed with long hairs. In the common type of sabethine antenna the
joints of the shaft are slender, cylindrical, with a basal whorl of long hairs and
an apical whorl of short hairs. The apical whorl is a modification of the general
pubescence of the joint and is variously developed according to the species. The
shaft of the male antenna is often longer and more slender than in the female.
When the hairs of the whorls are sufficiently abundant the female antenne
appear sparsely plumose, like those of the male. The last two joints of the male
antenna are somewhat longer than the preceding ones, but these differences are
less marked than in the culicine forms. This lengthening of the last two joints
also occurs in the females of some species, but usually it is only the last joint that
is longer in this sex.

The globose second antennal segment, as we have already mentioned, is a
highly developed organ of sense. Child has investigated this organ anatomically
and histologically in the most careful manner, not only in a number of Nemocera,
including Culex, but in insects of other orders. He succeeded in tracing the
organ, variously modified, in nine different orders of insects. The organ reaches
its highest development in the Nemocera, and, as it was first recognized as a
sense-organ by Johnston, Child has named it Johnston’s organ. The function
of this organ has been frequently discussed. As our present knowledge of mos-
quito habits tends to modify the generally accepted ideas regarding its function,
a description of the organ itself is essential. We translate this, as far as seems
necessary, from Child’s classic paper, and adhere to his procedure in first de-
scribing the organ in Corethra (Mochlonyz auct.), a non-biting culicid, and
following with a comparative description in Culex. The conditions in the male
of Corethra culiciformis are as follows:

“The cup-shaped second segment is 0.15 mm. in length and 0.25 mm. broad.
The hollow of the cup, in which the shaft is attached, measures 0.08 mm. in
diameter and is 0.05 mm. in depth. The outer surface of the segment is densely
clothed with very small sete and in addition with a few larger ones. This seg-

ment rests upon the annulate segment which is hidden in the anterior surface
of the head, so that the movement of the entire antenna is brought about by the

muscles attached here.
“Tt is this second segment which contains the sense-organ in question, Johns-
ton’s organ, an organ of great development and very complicated structure (pl. I,
EXPLANATION oF Puate I.

ANTENNAL SENSE-ORGAN OF CULICIDA.

Figs. 1-6. Corethra

1. First and second antennal segments of mature
male; longitudinal section.
N, main antennal nerve.
, antennal muscles within first segment.
O, anterior head-integument.
C, chitinous covering of first segment.
@, posterior portion of layer of ganglion cells.
N’, nervecord which passes through layer of
ganglion cells.
W, transition stages between rods and hypo-
dermal cells.
t, layer of rods.
K, basal nuclei of the rods.
fibrous layer.
layer of ganglion cells.
single layer of hypodermis.
ehitinous covering of the second segment.
chitinous process of plate.
the plate.
, Inass of hypodermis behind plate.
oO”, chitinous covering of first segment of shaft
(third antennal segment).
N”, nervecords of antennal shaft.
M’, muscles of head.
T, trachea.
2. Part of plate with processes drawn in perspective.
A, chitinous processes.
P, plate with radial thickenings.
c”, chitinous covering of first segment of shaft.

r
x,
O,
A,
B

First and second antennal

main antennal nerve.
muscles of first segment.
chitinous covering of first segment.
, nervecord which supplies second segment.
& outer and inner layers of ganglion cells.
?
Cc’,

peas
¢
St, rods.

Fig. 7. Culex.
N,
M,
N
G&

itinous covering of second segment.

culiciformis Degeer.

3. Section through periphery of plate showing
bases of processes.

A, transverse section of a process.

c’, chitinous covering of second antennal seg-
ment.

P, peripheral part of plate.

Sector at about point A of fig. 1 of transverse
section of second antennal! segment of male.

A, chitinous process seen in transverse section.

O’, chitinous covering of second segment.

Y, radiate spaces between groups of rods.

St, rods,

K, basal nuclei of rods.

F, fibrous layer.

G, layer of ganglion cells.

, hypodermis of second segment.
Rods.
G, ganglion cells of rods.
fiber.

F er.
K, basal nucleus.
St, body of rod.
. Transverse sections of rods; a, through base of
a rod; b, through upper nucleus.
St, body of rod.
K, nucleus of rod.

4

segments of female; longitudinal section.

L, K, V, thickened parts of chitinous covering of
second segment.

P, plate. :

B, base of shaft.

o”, chitinous covering of first segment of shaft.

WN”, nervecords of shaft.

T, trachea.

 

29a
SVeUIVALIVIN 109

PLATE |

 

 

 

 

 

After C, M. Child.

Antennal sense-organ of Culicidz.
30 MOSQUITOES OF NORTH AMERICA

fig. 1), especially in the male. As mentioned above, the shaft of the antenna
(pl. I, fig. 1, C”) is inserted in the center of a plate which is striped with radial
thickenings of the cuticula (fig. 1, P; fig. 2, P) and which forms the floor of the
cup-shaped depression upon the distal surface of the segment. Through an
opening in its center the tracheal trunk and the nerves (fig. 1, N”, T’) penetrate
into the shaft of the antenna. Around the base of the shaft the plate is 0.01 mm.
in thickness, however, towards the periphery it becomes somewhat thinner, then
again thicker. At the same time it bends forward and joins the chitin covering
the sides of the cup-shaped depression. This plate therefore, when seen from in
front, has the form of a radially striped saucer with an opening in the center.
From the periphery of this plate, in its entire circumference, there arise in a
lateral direction 70 to 90 fine chitinous processes, 0.03-0.05 mm. in length,
which gradually bend forward (fig. 1, A, 2, A) and which serve as points of at-
tachment to the nervous end-organs in the manner to be described later. The
processes do not take their origin from the surface of the plate but from deep
within its substance. This is proved by the fact that in a section through this
part of the plate from front to back the transverse sections of the processes can
be recognized as small, more strongly light difracting circles (fig. 3, A) within
the surrounding mass of the plate substance. The plate is composed of cuticular
substance and its posterior surface is covered by a layer of hypodermal cells
(fig. 1, H’). The plate is affected by different coloring substances in entirely
the same manner as the connecting membrane between the antennal segments ;
for this reason and others to be mentioned below, it is not to be looked upon as
a separate segment of the antenna but simply as connecting membrane.

The outer surface of the segment, as well as the sides of the cup-shaped de-
pression up to the margin of the plate, which also belong to the surface, is formed
by a layer of chitin, 0.005-0.008 mm. in thickness (fig. 1, C’). At the anterior
margin of the cup its hollow is somewhat narrowed by the thickening of the
chitin (fig. 1). At the base also, which serves as point of insertion for the
muscles moving the antenna, the chitin is somewhat thickened. Under the
chitinous layer there lies the hypodermal layer which in the imago generally
consists of very small cells (fig. 1, H).

“ Separated from the chitinous covering by a narrow space there is a layer of
ganglion cells, 0.02—0.04 mm. in thickness (fig. 1, @),* consisting of nearly
round, indistinctly defined ganglion cells of about 0.005 mm., which possess
comparatively large nuclei. In preparations by maceration one sees that from
the cells fine protoplasmic processes proceed (fig. 5, G@). Owing to these fine
threads, which are probably connected with each other, this layer has the ap-
pearance, under low magnification, of a nearly homogeneous mass densely filled
with nuclei.

“ Still farther inward, between the ganglion cells and the end-organs, there
lies a layer, 0.005-0.007 mm. in thickness, of fibres running in two directions
(fig. 1, F; 4, F). One set of these connects the ganglion cells, with the end
organs, the others cross these at right angles from behind forward; these are
fibres originating from the large antennal nerve and which connect with the
ganglion cells. On the posterior portion of the ganglion layer the place can be
detected where this nerve fiber passes through the cell layer (fig. 1, N’). It is
noteworthy in this connection that the nerve fibres, which supply the larger part
of the cell layer, lie between these and the end-organs instead of on the outer
side of the layer, as in the posterior section. The smaller portion of the ganglion
cells lying within the posterior half of the organ (fig. 1, @’) connect mostly with
fibres emanating directly from the nerve.

 

*“ With reference to the cells my drawings are diagrammatic. I have not attempted to
draw in the fine processes.”
JOHNSTON’S ORGAN 31

_ “This part of the organ contains only such cells and nerve-fibers as are found
in the ganglion of every sense-organ composed of several elements, and in this
case they are, moreover, very similar to the elements of the optic ganglion of the
same animal. Its cells show the same size and also appear to stand in connection
with each other by a net-work of protoplasmic fibers.

“ More differentiated are the end-organs proper which form the remainder of
the nerve-elements filling the interior of the chitinous capsule (fig. 1, St; 4, St).
These lie inward from the layer of fibers and consist of a great number of small,
thin, rod-like structures which can only be distinguished clearly in an isolated
state, after maceration. Such a rod (fig. 5) is 0.04 to 0.05 mm. long, 0.002 to
0.003 mm. in diameter at its base, and represents a very pointed cone on the sides
of which are generally found two oval nuclei, 0.005 to 0.008 mm. long and rich
in chromatin, of which one is situated basally and the other towards the apex.
In transverse section (fig. 6) the nucleus lies, perhaps covered by a thin layer of
protoplasm, upon the surface of the rod, which is clasped more or less by it.
At its base the rod gradually passes over into a fiber which proceeds through the
fibrous layer to the ganglion cells (fig. 5, F). The body of the rod itself behaves
towards stains like a cell-body but appears to be of more solid consistence and in
preparations by maceration often shows an inclination to split from the apex
into two or three fibres. Ontogeny proves that the rods are formed from the
cell bodies. The rods are attached or hang by their apices from the chitinous
processes of the above described central plate (fig. 1, 4), and mostly upon their
posterior surface. Asis proved by maceration, this connection is a very firm one,
for sometimes the apices of the rods may still be seen upon the processes while
the larger part of them is already torn away. Through their slender form and
close disposition the radiate arrangement is brought about. In longitudinal
section (fig. 1, St) they correspond approximately with the radii of a circle the
center of which is situated somewhat before the chitinous process. In a trans-
verse section through the anterior end of the processes one sees that the rods (fig.
4, St) are divided into groups corresponding with them ; between these groups
there are narrow spaces, through about half their length (fig. 4, V), which are
probably filled with blood during life. In each group the rods lie close together,
and each, in transverse section, possesses several rods. Upon the rods lying next
to the interspaces the nuclei are nearer to the apices of the rods than in the
others ; these nuclei lie upon the surface of the group and bound the interspaces,
so, that, in a transverse section through the groups striking the rods at about
their middle, one sees the rods and their nuclei as alternating layers; a double
layer of nuclei separated by a narrow interspace and a multiple layer of rod-
bodies, etc. In their basal portion the groups can no longer be distinguished

fig. 4).

on. antennal nerve arises on both sides from the anterior ventral part of
the cerebral ganglion as a large nerve trunk containing ganglion cells. At the
point of entrance into the antenna the nerve is nearly 0.1 mm. in diameter (fig.
1, V). After its entrance into the second segment the nerve spreads out in all
directions and gives off fibers (fig. 1, N’) to the ganglion layer in the entire
circumference of the organ, and these form a funnel, as it were, upon which the
nervous parts of the sense organ are attached. These fibers pass through the
layer of ganglion cells and continue into the fibrous layer (fig. 1, F), which in
the anterior part of the organ separates the ganglion cells from the rods. This
funnel is incompletely separated into bundles of fibres by interspersed ganglion
cells. Other fibers go directly towards the posterior part of the layer of ganglion
cells and from the center of the funnel there arise two thin threads of fibers
which pass anteriorly through the opening in the central plate into the shaft of
the antenna (fig. 1, NV”).
32 MOSQUITOES OF NORTH AMERICA

“The tracheal system is somewhat complicated and very variable. In general
the antenna is supplied by a large tracheal trunk which is present upon both
sides of the head. This generally throws off a branch, which, passing towards
the median side of the antennal nerve, enters the antenna and in its course sends
out a number of branches to the large nerve. Another somewhat larger trunk
passes along the lateral side of the nerve-trunk as continuation of the main
trunk, probably also throws off branches to the antennal nerve and can also be
traced into the antenna. At the base of the second segment both trunks divide
into several branches; some of them pass between the ganglionic layer and the
hypodermis and divide further, while others penetrate the ‘ nerve-funnel’ and
supply the central parts of the organ. At least one of these continues through
the opening in the central plate into the shaft of the antenna.

“ Beneath the central plate there is a space through which the trachee and the
nerve cords pass. This space is enclosed at the sides by the ‘ nerve-funnel,’ the
layer of ganglion cells and the rods, as well as by some less differentiated cells
(fig. 1, W) which represent transition states between the rod-cells and hypo-
dermis (H’) lying beneath the plate; anteriorly the hollow space is limited by
the plate and the hypodermal layer pertaining to it. It is connected, through
the opening in the plate, with the interior space of the shaft as well as with the
radial spaces between the groups of rods and in consequence it is also connected
with the outer space between the hypodermis and the layer of ganglionic cells;
during life it is filled with blood fluid.

“The essential among the elements of this highly developed sense-organ are
then the rods, which are, as will be shown in the following, modified hypodermal
cells. The remarkable size of the organ and the great number of sensory termi-
nal elements, as well as the large nerve-trunk in immediate connection with the
cerebral ganglion, point to a function of great importance in the life of the
insect or the preservation of the species.”

In the female the antenna is more simple and the sensory organ is much
smaller and less complicated.

“The part corresponding to the plate of the male consists of a circular plate
of cuticular substance surrounding the base of the shaft. Here it is clearly
apparent that the plate is nothing but the connecting membrane, and the plate
of the male is without doubt homologous with that of the female, only developed
to a much higher degree. . . . The rods are in every respect similar to those of
the male, of the same size, and also connected with the ganglion cells by fine
fibers. Their mode of termination is, however, a different one than in the male.
The plate in this case does not possess any processes but the rods terminate
with their apices in the substance of the plate itself, and, to be more exact,
between the chitinous ring and the base of the shaft. Upon the median and
lateral surfaces of the rod-layer lie elongate, less differentiated cells representing
intermediate stages between the rods and the ordinary hypodermal cells.”

Child gives the following comparison of Culex pipiens with Corethra:
1. Male:

“The antenna of the Culex male shows great similarity with that of Moch-
lonyz. . . . The basal segment is here also rudimentary, somewhat sunken into
the head and serves as point of attachment for the antennal muscles.

“The second segment is a comparatively large, cup-shaped organ, the relation
of which to the other segments, and its structure, are in general the same as in
Mochlonyz, so that I do not need to give a separate figure; I only wish to men-
tion a few points in which the two forms differ from each other. The entire
segment measures 0.17 mm. in length and 0.12 mm. in breadth, therefore is
ANTENNAL NERVE-STRUCTURES 33

smaller than in Mochlonyx. The hollow of the cup is proportionally somewhat
deeper and larger. The ganglion cells, instead of lying in one, lie in two layers
separated from each other by nerve-fibres. Accordingly the nerve, which corre-
sponds to the nerve N’ (fig. 1), divides into two parts, of which one passes be-
tween the two layers of ganglion cells, and the other between the inner layer and
the rods.* The rods are somewhat shorter and more slender than in Mochlonyz.
Their length fluctuates from 0.02 to 0.025 mm. They appear shorter in the
anterior part of the organ than in the posterior. Their nuclei are richer in
chromatin than the ganglion cells.”

2. Female: The following gives the essential parts relating to the organ:

“Tt departs in its structure from that of the female Mochlonyx and forms,
to a degree, a transition between this and that of the male.

“The form of the entire segment is that of a very thick-walled cup provided
with a very shallow hollow (pl. I, fig. 7); in this hollow the shaft is placed,
the base of which is formed by a disk perforated by a central opening (fig. 7,
B). In connection with this disk and covering its peripheral part, is the con-
necting membrane (P), which, as in the male, is furnished with radial thicken-
ings and corresponds to the plate. The noteworthy thing is that here the base
of the shaft forms a part of the floor of the depression. I consider this part B as
belonging to the shaft because it is in direct connection without interruption
with the lower part of the shaft and no difference can be detected from the
chitinous covering of this. At the same time the demarkation between it and
the connecting membrane or plate (P) is very distinct. The latter is nearly
transparent, like the plate of the male, and appears to possess a consistency dif-
ferent from that of the common chitin. The outer wall of the depression is
formed by a thickened portion (fig. 7, K) of the chitinous covering of the
second segment with an annulate projecting margin (fig. 7, V) which projects
towards the shaft and reduces the opening of the hollow. Outwardly from this
excrescence the chitinous covering forms a zone covered with blunt elevations
which carry fine bristles (fig. 7, L). The remainder of the surface of the seg-
ment is also covered with short, fine bristles.

“Close below the chitinous covering lies, as usual, the hypodermis of one
layer ; these are succeeded inwardly by the ganglion cells, which here, as in the
male, are arranged in two layers, incompletely divided by nerve fibres. Sepa-
rated from the inner layer of ganglion cells by a layer of fibres lie the rods, which
are directly connected at least with the inner layer of cells by fine fibres. The
rods are somewhat longer than in the Culex male, about 0.03 mm., but agreeing
with them in form. In longitudinal section they lie in radiate arrangement,
radiating from the connecting membrane or plate. In transverse section it is
seen that, similarly to the male of Mochlonyz, the rods form groups (compare
pl. I, fig. 4), separated by very narrow interspaces, throughout the circumfer-
ence of the organ and corresponding to the thickenings of the connecting mem-
brane. On the median and lateral margins of the rod-layer more or less modi-
fied hypodermal cells represent the transition stage between rods and ordinary
hypodermal cells. Two nerve cords and a tracheal trunk pass through the cen-
tral hollow space into the shaft of the antenna.”

This organ, in conjunction with the antennal shaft and its whorls of hairs,
has been generally looked upon as an organ of hearing. The long hairs of the
whorls vibrate in response to sound waves of a certain pitch and react upon the
sensory organ of the globose second segment. Johnston, in a paper published
in 1855, was the first to describe the antenna as a complex sense-organ, and he

 

*In fig. 7, plate I, belonging to the female of Oulez, this arrangement is likewise present.
34 MOSQUITOES OF NORTH AMERICA

confidently termed the second joint the “auditory capsule.” His studies were
evidently influenced by his knowledge of the structure of the vertebrate ear, not
only in the interpretation of the anatomical structure of the organ, but, in con-
sequence, also of its functions. Probably inadequate microscopes and methods
contributed in large part to his errors. He described what he found as follows:

“The auditory capsule is filled with a fluid of moderate consistency, opales-
cent, and containing minute spherical corpuscles, and which probably bears the
same relation to the nerve as does the lymph in the scale of the cochlea of higher
animals. The nerve itself of the antenna proceeds from the first or cerebral
ganglion, advances towards the pedicle of the capsule in company with the large
trachea which sends its ramifications throughout the entire apparatus, and,
penetrating the pedicle its filaments divide into two portions. The central
threads continue forward into the antenna and are lost there; the peripheral
ones, on the contrary, radiate outwards in every direction, enter the capsule
space, and are lodged for more than half their length in sulci wrought in the
inner wall or cup of capsule.

“In the female the disposition of the parts is observed to be nearly the same,
excepting that the capsule is smaller.”

Assuming the conditions to be such as described it was very natural to at-
tribute to the organ complex functions. Johnston sums up his reasons for be-
lieving the antenna an auditory organ of high perfection as follows:

“The position of the capsules strikes us as extremely favourable for the per-
formance of the function which we assign to them; besides which there present
themselves in the same light the anatomical arrangement of the capsules, the
disposition and lodgment of the nerves, the fitness of the expanded whorls for
receiving, and of the jointed antenne fixed by the immovable basal joint for
transmitting vibrations created by the sonorous modulations. The intra-cap-
sular fluid is impressed by the shock, the expanded nerve appreciates the effect
of the sound, and the animal may judge of the intensity, or distance, of the
source of the sound, by the quantity of the impression: of the pitch, or quality,
by the consonance of particular whorls of the stiff hairs, according to their
lengths ; and of the direction in which the undulations travel, by the manner in
which they strike upon the antenne, or may be made to meet either antenna, in
consequence of an opposite movement of that part.”

A. M. Mayer, in the course of his researches in acoustics, made most interest-
ing experiments with the supposed auditory function of the antennal hairs of
the male mosquito. With tuning-forks, he showed that some of the hairs are of
such a structure that they vibrate in response to sound-waves numbering 512 per
second. Other hairs vibrated to other notes, showing altogether a considerable
range. He says:

“T infer from my experiments on about a dozen mosquitoes that their fibrils

are tuned to sounds extending through the middle and next higher octave of
the piano.”

Mayer carried his experiments farther, and, taking accurate measurements of
the thickness and length of two hairs which vibrated in response to the tuning-
forks Ut 3 and Ut 4, made large wooden models of them. The model of the
hair vibrating to the Ut 3 tuning-fork was a meter in length. These models
responded to vibrations of approximately the same number as the hairs them-
selves.
HEARING IN MOSQUITOES 35

Perhaps the most interesting result of his experiments was the discovery of
the fact that the antennal hairs enable the mosquito to determine the direction
from which the sound-waves proceed. He experimented with the song of the
female and found that the hairs of the male antennex vibrate when the song of
the female comes more or less at right angles to them, while those which point
to or from the source of sound are not affected. If the song is directly in front
of the head it will be most fully received by the antennal hairs. If the song of
the female affects one antenna more than the other, the male, by turning until
both antenne are equally affected, could thus determine the direction of the
female.

“The song of the female vibrates the fibrille of one of the antenne more
forcibly than those of the other. The insect spreads the angle between his an-
tenne, and thus, as I have observed, brings the fibrille, situate within the angle
formed by the antenne, in a direction approximately parallel to the axis of the
body. The mosquito now turns his body in the direction of that antenna whose
fibrils are most affected, and thus gives greater intensity to the vibrations of the
fibrils of the other antenna. When he has thus brought the vibrations of the
antenne to equality of intensity, he has placed his body in the direction of the
radiation of the sound, and he directs his flight accordingly; and from my ex-
periments it would appear that he can thus guide himself to within 5° of the
direction of the female.”

While Mayer accepted the function of the antenne as auditory, he clearly
perceived that no comparison could be made with the sense of hearing in the
higher vertebrates, and expresses his conclusions in these terms:

“ Some may assume from the fact of the co-vibration of these fibrils to sounds
of different pitch, that the mosquito has the power of decomposing the sensation
of a composite sound into its simple components, as is done by the higher verte-
brates ; but I do not hold this view, but believe that the range of co-vibration of
the fibrils of the mosquito is to enable it to apprehend the varying pitch of the
sounds of the female. In other words, the want of definite and fixed pitch to
the female’s song demands for the receiving apparatus of her sounds a corre-
sponding range of the co-vibration, so that instead of indicating a high order
of auditory development it is really the lowest, except in its power of determining
the direction of a sonorous centre, in which respect it surpasses by far our own
ear.”

Our own observations of the habits of mosquitoes lead us to doubt that the
antenne, if auditory at all, are so in their primary function. The foregoing
hypotheses are founded upon the assumption that the male seeks the female and
is attracted by her song. In fact such is not the case. At least in those forms
in which the antenne of the male are most highly specialized the males
“swarm ” and the female seeks the male. In our experience the song of the
female does not attract the male. Mayer appears to have come very near the
truth when he found that the antenne served for orientation. One of us (Knab)
has observed that the males in a swarm always dance facing the breeze or air-
current, no matter how slight this may be, and adjust themselves instantly to
any shifting of the breeze. Why this is done would be difficult to explain, but
that the antennz make this possible is clearly apparent from Mayer’s observa-
tions. Of course it can not be denied that the antenne are perhaps also, in a
36 MOSQUITOES OF NORTH AMERICA

very rudimentary way, auditory in function. Child already observed the great
sensitiveness of the swarms of dancing males to sound vibrations,

“ moreover not alone to the higher, but also to deeper tones. If one sings a deep
note in the vicinity of a swarm, the entire swarm is immediately thrown into
confusion which lasts several seconds. . . . Faint noises have the same effect,
naturally in a lesser degree. I have observed the same from the whistle of a loco-
motive, even when this was one or two kilometers away. If one approaches a
swarm of gnats in a boat, upon some sudden noise, such as a stroke of the oars,
the entire swarm is thrown into a wild dance and frequently flies away or dis-
solves. As, however, with great care, even with fairly rapid movements, one can
get close to the swarm without the gnats reacting in any way, it follows that the
disturbance is caused by the sound and not by a visual impression. From these
observations of course nothing can be concluded regarding the location of the
organs of hearing; it is only proved thereby that the gnats are very sensitive to
sound. But because it is in these insects that an organ occurs which appears
especially equipped for the reception of air-vibrations, the probability of a con-
nection with that behavior is very great.”

While it is evident from the foregoing that mosquitoes react to sound-waves,
it is by no means clear that they can perceive them as such. If the sound-im-
pressions are received through the antenne, as the organization of these ap-
pendages seems to indicate, it is still to be doubted that there is a differentiation
of the impressions produced by sound-waves and other stimuli, such as a current
of air, or between sounds of different pitch. Child’s conclusion was that the
function of Johnston’s organ was originally the perception of tactile stimuli,
and that when it became more highly developed it also served for the perception
of sound-waves. “The resulting ‘auditory impression’ is a modified tactile
impression.” It is worthy of note, in this connection, that the male mosquitoes
emit a very high-keyed song while swarming ; in fact, this sound is so high that
it is probably beyond the range of many human ears.

The part of the head inclosed by the eyes and bearing the antenne shows little
specialization, is partly membranous, and in large part hidden by the globose
second antennal joints. Medianly, above the antenna, and resting against the
front margin of the eyes, is a small chitinous piece. In the Culicini this is
usually rather poorly defined, subquadrate or more or less triangular, with its
base resting against the margin of the eyes and the apex projecting forward be-
tween the antennz. In the Sabethini it is conspicuous, although small, in those
forms in which the eyes are separated above by a narrow wedge. This wedge, in
fact, is a backward extension of the chitinous piece in question ; the portion pro-
jecting forward beyond the margin of the eyes is prominent and may be either
pointed or truncate in front. That part of the front below the antenne and
above the clypeus usually shows no structural peculiarities. In one sabethid
genus, Rhunchomyia, however, this portion is produced into a tubercle which
projects just above the clypeus.

CLYPEUS.

The clypeus is large and prominent, chitinous, and projects above the inser-
tion of the proboscis. Its development is unusual, and this is to furnish a place
of attachment, on its inner walls, for the powerful muscles of the epipharynx.
It is strongly chitinized above and its shape is roughly globose, or roundedly
SO WAM RoE

_

11,

12.
13.
14,
15.

EXPLANATION OF Piate II.

. Side view of head of Culex, with extended mouth-parts; a, antenne.

Same from above with mouth-parts partly cut away.

Tip of labium of female Culex.

Tip of labium of male Cuwlez.

Tips of separated sete of mouth-parts of Culez.

Tip of labrum-epipharynx seen from beneath and in section.

. Cross-section through labelle and tip of labium of female Culez.

Cross-section near middle of the proboscis of female Culez.
Cross-section through pharyngeal region of forward part of head of female Culez.

. Cross-section through posterior part of head of female Culez, to show the sucking

bulb of the esophagus. 0b, lumen of esophageal bulb; bm and bm’, muscles to
dilate the bulb; 7, chitinous rods which support the wsophageal bulb; rm,
retractor muscles of maxille, at their point of origin; t, elastic plates of sides
of bulb.

Longitudinal section of head of a female Culex. b, esophageal bulb; g, point
where the clypeus appears cut off from rest of head; v, valve between pharynx
and esophagus.

Cross-section near middle of the proboscis of a male Culez.

Cross-section at base of the proboscis of a male Culez.

Cross-section further into the base of the proboscis of a male Culez.

Cross-section through pharyngeal region of head of a male Culez.

The following letters have the same signification throughout :

ce, clypeus. Ir, labrum. p, pharynx.

e, epipharynx. Ire, labrum-epipharynx. pm, pm’, pharyngeal muscles.
h, hypopharynx. , mandibles. &, supracesophageal ganglion.
4, infre@sopiagedl ganglion. mh maxillary palpi. tr, tracheal stem.

i, labium, me, maxille.

1b, labelle. oe, cesophagus.

36b
FUBLICATION 159

PLATE (I

  

After Dimmock.

Mouth-parts of Culex.
MOUTHPARTS OF MOSQUITO 37

conical more or less constricted at base. It presents no noteworthy modifica-
tions. Its surface is usually naked and smooth, or, due to the presence of very
fine hairs, pruinose. In some cases it is densely clothed with scales, and in one
genus, Joblotia, it bears many scattered coarse hairs, particularly towards the
margin.
THE PROBOSCIS.

All true mosquitoes have a long proboscis of complex structure; it is used as
a sucking-organ, and in the females of many species as a piercing organ as well.
It is most highly organized in the females with blood-sucking habits. The organ
was already carefully studied by the early workers with the microscope, among
whom may be particularly mentioned Leeuwenhoek, Swammerdamm, Barth,
and Réaumur. These early investigators only studied the mouthparts per se,
without thought of their relations to the mouthparts of other insects, It was not
until after the study of entomology had been put on a firm footing by systematists,
and the significance of the mouth-parts of insects in classification had been
pointed out by Fabricius, that attempts were made to homologize the mouthparts
of the different orders of insects. Savigny, in 1816, already developed the idea
that the mouthparts of all insects were reducible to the same general plan of
those of the chewing insects, and that these mouthparts were the serial homo-
logues of locomotory appendages. The belief that the mouthparts of the mosquito
(and of the Diptera in general) are homologous with those of mandibulate
insects has been very generally accepted by modern entomologists. It was not,
however, until about 30 years ago that any exact knowledge of the organization
of the proboscis of the mosquito was reached, the previous analyses having been
unsatisfactory from the scientific point of view, and conflicting. In 1880 two
careful studies of the mouthparts of the mosquito and of other Diptera, carried
out independently with strictly modern methods, were published by Dimmock
and by Meinert. Both these works describe very completely the anatomy of the
proboscis and related parts; the interpretation of the mouthparts by the two
authors, however, is quite different. Dimmock followed the generally accepted
idea and homologized the components of the proboscis with the mouth-organs of
mandibulate insects. Meinert, on the other hand, concluded that no such
homology exists and presented an entirely different interpretation. The studies
of Kellogg, of the development of the mouthparts of the dipterous imago within
the larva, show conclusively that the generally accepted view is correct and essen-
tially as presented by Dimmock. It seems desirable, however, to present briefly
Meinert’s views, and also those of other authors when at variance with the ac-
cepted interpretation of the facts. Additions to our knowledge of the mouth-
parts made since by different workers will be also considered. Dimmock’s de-
scription of the mouthparts of the female and male Culez is so clear and full
that we reproduce it herewith, together with the excellent plate elucidating the
structures (pl. II, opposite page 36).

In the female:

“The mouth-parts which form the proboscis of the female Culez, as I have
found them by study of C. rufus, C. ciliatus, and C. pipiens, consist of a labrum
4
38 MOSQUITOES OF NORTH AMERICA

(pl. II, fig. 1, Ir), an epipharynx (e), a hypopharynx (1), two mandibles (m),
and two maxille (ma), all sheathed, when in repose, in the labium (7), which
receives them into a groove on its upper side. Hach maxilla has a maxillary
palpus (mp), which lies outside the labium ; the latter has no palpi. The labium
and maxillary palpi are covered with hair and scales ; the other mouth-parts are
naked, light brown, setiform, and transparent ; they all originate at the anterior
basal portion of the head, and are, with the exception of the maxillary palpi,
of about equal length, that is, about three to four times the length of the head.
The maxillary palpi, in the females of Culex proper, are about the length of the
head. The scaleless mouth-parts are not jointed, and are the ones which pene-
trate the skin in biting. The labrum and epipharynx are united in their whole
length, forming a piece which is shown in section in fig. 6, d. The other mouth-
parts are free to the base. A pumping organ, trianguloid in cross-section (fig.
10, b), is formed by a dilation of the esophagus behind the cesophageal nerve-
ring. Each of the above-mentioned parts will be described more in detail later.
In comparative size and strength the mouth-parts would be arranged as follows,
the largest and stoutest first: labium, labrum-epipharynx (the name by which
I designated this compound piece in diptera), hypopharynx, maxille, and
mandibles.

“ The general arrangement of the mouth-parts, relative to each other, is shown
best in fig. 8, which is a figure of a cross-section through the middle of the pro-
boscis of a female Culex rufus, while in repose, with the sete sheathed in the
labium. The labium (1), clothed on the outer side with its scales and hairs, is
wrapped nearly around the other mouth-parts. In it lie the two maxille (mz),
partly enclosing the parts above them, and thus helping to bind the parts to-
gether; above the maxille are the two mandibles (m), and immediately above
the mandibles, in the median line, is the hypopharynx (h), with a thickened
middle portion. Resting on the hypopharynx is the labrum-epipharynx; the
epipharynx (¢) is omega-form in section, and above it, delicately attached, is
the labrum (Ir). The changes in relative position which the mouth-parts of
Culex undergo as they approach the head can be best described in the subsequent
description, in detail, of each separate part.

“ The labrum-epipharynx (fig. 1, 5, 6, 7-8; Ir and e) of Culex consists of the
thin labrum resting upon and fastened to the epipharynx; it tapers gradually
from base to apex. The epipharynx is omega-form in cross-section, being a chan-
nel rather than a tube, a tube being formed by the pressing of the hypopharynx
upon its under side. The tube thus formed is the channel through which the
blood, which Culex sucks, passes into the pharynx. At its base or proximal end
the epipharynx is supported and moved by strong muscles having their inser-
tions on the upper side of its wings or lateral portions, and upon the upper side
of its tube. These muscles extend upward and posteriorly, and have their origin
on the inner surface of the clypeus. (See figs. 9 and 11.) These muscles (pm),
by their contraction, elevate, and perhaps slightly retract, the epipharynx and
the labrum to which they are attached. These muscles probably aid in suction
for when the sete are all stuck firmly in the skin, the contraction of these muscles
would only serve to raise the base of the epipharynx from that of the hypo-
pharynx; this action would tend to produce a vacuum between the two (see fig.
9), and thus cause the blood to be drawn up in the tube of the epipharynx. The
probability that these muscles aid in suction is augmented by the fact, the ex-
planation of which I have more fully developed in the part of my dissertation
devoted to a comparison of the mouth-parts and suctorial apparatus in the dif-
ferent families of diptera upon which I have worked, that the corresponding
muscles are devoted to suction in other flies, which cannot raise their epi-
pharynx from their other mouth-parts so freely as is seen in fig. 1, and further,
LABRUM ; HYPOPHARYNX 39

that in the male Culex, which does not possess—as does the female— a pumping
apparatus behind the oesophageal nerve-ring, these muscles are the ones that
must serve for suction. The section represented in fig. 9 was taken near the base
of the clypeus ; a few sections further on, posteriorly, the channel for the passage
of food turns upward and then backward again, passing in its course a place
(fig. 11, v) where its walls approximate dorsally and ventrally. This narrowing
of the walls is probably a valve to prevent the return of fluids to the mouth dur-
ing the pumping process. The pharynx with its surrounding muscles in Culex
is the equivalent of what has been termed the fulcrum in Musca. Macloskie *
writes of the fulcrum, ‘It seems to be general in diptera; even the mosquito
possesses it,’ but he does not further describe it, in other diptera than Musca.

“The tip of the labrum-epipharynx seems to turn upward (fig. 1, Ir-e), al-
though the opening is upon the ventral surface, as may be seen in fig. 6, b, which
represents the ventral view of the tip of this part. The tip of the labrum-epi-
pharynx is comparable to a quill-pen with three tips near each other, the middle
one of these three tips being slightly shorter than the other two. The two lateral
portions of the epipharynx, as seen in section, when they near the tip, lay them-
selves closely upon the sides of the tubular portion, passing upward upon it, as
seen in fig. 5, lv-e; they thus serve to strengthen the two outer points of the tip
of the epipharynx, while the labrum continues to a sharp point at the tip, and,
united with the upper surface of the epipharynx tube, forms the middle point of
the tip. The channel, or slit, along the under side of the epipharynx, widens
toward the tip (fig. 6, b), leaving thus an opening for the passage of fluids into
the tube of the epipharynx.

“The labrum itself is a thin lanceolate lamella of chitin, concave along the
under side from the basal portion to the tip, and its concavity rests upon and
fits to the convexity of the tubular part of the epipharynx, to which it is so
lightly attached that they readily separate by application of caustic potash. The
outer edges of the labrum roll slightly inward toward the epipharynx along most
of its length. (See fig. 6, d.) Atits base the labrum sends a chitinous support
beneath the clypeus, where it separates more from the epipharynx and has its
own muscles, indicating that the labrum has a degree of motion independent
of the epipharynx, a motion allowed, perhaps, by the elasticity of the connection
between the labrum and epipharynx. The muscles of the labrum (fig. 9, pm’)
are inserted upon the upper side of its base and have their origin on the inner
surface of the roof of the clypeus. These muscles are, at least in the females of
Culex rufus, divided into three portions in their upper part, as shown in fig. 9.

“The hypopharynx of the female of Culex is a linear, lanceolate, transparent
lamella of chitin, with a longitiudinal rod through the middle, the nature of
which will be discussed later. At its base the hypopharynx forms the continua-
tion of the under wall of the pharynx. (See fig. 11,4.) The hypopharynx is
closely pressed upon the under side of the epipharynx, completing the tube
nearly formed by the epipharynx. No muscles have their insertion on the base
of the hypopharynx. Its tip is simply lanceolate (fig. 5, h). In Culex pipiens
and C. rufus nothing further is visible (with a magnifying power of five hundred
diameters), in sections of the thicker middle portion of the hypopharynx, than
a simple rod of chitin ; but, in C. ciliatus, a North American species of which the
mouth-parts are larger, this rod appeared to be tubular. Is it a rod or is it a
tube? Menzbier + writes (p. 25) that in diptera ‘neither the labrum nor the
hypopharynx possesses a completed tube, but only a channel’ which leads into

 

* Macloskie, G.: The proboscis of the house-fly. (Amer. Naturalist, March, 1880, v. 14, pp.
153-161, figs. 1-3. a

+ Menzbier, M. A. Ueber das Kopfskelet und die Mundwerkzeuge der Zweifliigler. (Bull, Soc.
impér. natur. de Moscou, 1880, t. 55, no. 1, pp. 8-71, tabs. 2-3.)
40 MOSQUITOES OF NORTH AMERICA

the salivary duct. That Menzbier is incorrect in affirming that the hypopharynx
has no complete tube I have clearly proved in my observations on Bombylius
and Fristalis; but the question still remains unsettled whether Culex has any
passage, either tube or groove, through the hypopharynx. Réaumur * (tome 4,
part 2, p. 396) discusses the probability of a poisonous fluid being secreted by
Culez, to cause the blood to flow more readily when it bites, and since his time
writers have, on the one hand, accepted this statement, without proving the
presence of such a fluid or of the glands to secrete it, or they have, on the other
hand, denied the existence of such a fluid and affirmed, as Leeuwenhoek did, that
the swelling subsequent to the bite of Culex was due to the irritation produced
by the tearing of the mouth-parts in the skin, without the aid of a poisonous
secretion. After having experimented a large number of times with the living
mosquito, I am convinced that there is use made of a poisonous saliva; for, when
biting, if the mosquito fails to strike blood, which it often does on parts of the
back of my hand, it may have inserted its proboscis (labium of course excepted)
nearly full length, in from one to six directions, in the same place, and with-
drawn its proboscis; indeed it may have inserted its proboscis, as often occurs,
in extremely sensitive parts; yet in such cases, if no blood be drawn, no more
effect is produced upon my skin than is produced by the prick of a sharp needle;
a red point appears only to disappear in a few hours. Certainly there has been
as much tearing of tissues in such a case as the above-mentioned, as there is
when Culex settles on a place richer in blood, and, with a single probing, draws
its fill. When the insect is allowed to draw its fill on the back of my hand, the
subsequent swelling lasts from forty to forty-eight hours, and the amount of
poisonous effect upon me, as proved by numerous experiments, is in direct pro-
portion to the length of time which the Culex has occupied in actually drawing
blood. The above-mentioned facts would indicate a constant outpouring of
some sort of poisonous fluid during the blood-sucking process, and would neces-
sitate a tube or channel for its conduction. Now, no other channel! exists through
which saliva could pass from the base to the tip in the mouth-parts which Culex
inserts in the skin, and this, together with the position occupied by the salivary
duct in other diptera, leads me to believe, without as yet being able to give
anatomical proof for it, that the hypopharynx of Culex contains a duct that
pours out its poisonous saliva. Having no fresh specimens of Culez ciliatus, and
the extreme minuteness of the hypopharynx in the species of Culex available, has
precluded my determination of the actual presence of glands in connection with
this mouth-part.

“The mandibles (figs. 1 and 8, m), the most delicate of the mouth-parts of
Culex are two very thin linear-lanceolate lamelle of transparent chitin, which
rest with their inner edges beneath each half of the hypopharynx, their outer
edges projecting beyond its outer edge, on each side. At the base of the proboscis
they appear to have no muscular attachments. They are slightly tapering from
the base to the tip, but are of equal thickness throughout their breadth; at the
tip they have a slight thickening, in form of a letter V, with its opening turned
toward their very delicate, almost invisible tip. (See fig. 5, m.)

“The maxille (mistaken by Gerstfeldt + for the mandibles, but correctly
figured by Muhr { on his diagram as maxille) are tapering lamelle of chitin,
apparently serrate at the tips. Hach maxilla is thicker near the inner edge, the
thickening being formed by a solid chitinous shaft, which is fixed longitudinally
upon the upper side. (See figs. 5 and 8, ma.) The bases of the maxille join

 

me ee A. F. Mémoires pour servir A I’histoire des Insectes. ... . {Edition 17387-
. 4, part 2.
Gerstfeldt, G. Ueber die Mundtheile der saugenden Insecten .... 18538.

Muhr, J. Die Mundtheile der Insekten dargestellt auf 5 Wandtafeln....1878.
MAXILLARY PALPI; LABIUM 41

the stouter maxillary palpi just before passing under the clypeus, and immedi-
ately afterwards they join the labium, and become imbedded, with the man-
dibles, in connective tissue. (See fig. 9, ma.) Their continuations in the head
are two delicate chitin-supports, each of which ends in a strong muscle; this
muscle, the retractor maxille (fig. 10, rm), passes backward and downward
through the head, beneath the infracesophageal ganglion, and has its origin in
the posterior basal part of the head. The maxille probably have no protractor
muscle, their forward motion being due to the elasticity of the chitin frame-work
of the head. The shaft of the maxille is very transparent, except near the inner
side where the chitin-rod runs; here it is brownish and more opaque. Out from
the above-mentioned chitin-rod extends a very delicate feathering, or corruga-
tion, of chitin to the edge of the most transparent portion of each maxilla, as
seen upon the basal portion of fig. 5, mz. The tip of the maxille (fig. 5, mz)
is very acute, has none of the before-mentioned chitinous corrugations, but, in
their place, near the outer edge, is a row of papille, which have their tips
slightly recurved toward the head, and consequently appear serrate. These
papille are upon the upper surface of the maxille, as can be readily seen, by
preparing the mouth-parts by lateral pressure, as in fig. 1.

“The maxillary palpi (figs. 1, 2, and 9, mp) are four-jointed in some species
of Culex, five-jointed in others. At first sight they appear to be three-jointed,
but more careful examination serves to show that the apparent basal joint is
made up of two joints, and oftentimes to reveal a very short, knob-like joint at
the extremity of what appears to be, at first, the apical joint. At their base the
maxillary palpi join the maxilla just before the latter pass beneath the clypeus,
and, with the maxille, join the other mouth-parts, as shown, in section, by fig. 9.

“The function of the maxille is, probably, to draw the other mouth-parts
into the skin, when Culez bites, for if one watches the maxillary palpi of Culex,
while the sete are entering the skin, the sete seem to pierce the skin, and enter
it with a slow gliding motion, as if drawn from below, instead of pressed from
above ; meanwhile, if one observes carefully, with a lens, the maxillary palpi can
be seen to be in an alternating motion, as if the maxilla to which they are
attached, pressed, first one then the other, into the skin, and then pulled the
other parts after them. The muscles, retractores maxillarum, already described,
lend weight to this view of the functions of the barbed maxille.

“The labium (figs. 1, 2, and 3, 1), the largest of the mouth-parts of Culez,
and the only one of them, helping form the proboscis, which contains muscles,
forms a sheath opening along the upper side, and receiving in its channel the
other mouth-parts (excepting the maxillary palpi), as seen in cross-section in
fig. 8; it tapers from base to tip, is flexible, has a delicately annulated structure,
and is clothed with hair and scales. At its base it unites with the maxille, man-
dibles, and hypopharynx, and continues into the under surface of the head.
Throughout its length it contains, on each side, muscles, which have their origin
in the base of the head and serve to control the motions of the labium. (See
figs. 8 and 9, ml.) At the sides of the tip of the labium are attached two lobi-
form appendages, the labelle, which are seen at Ib in fig. 3 with the true tip of
the labium proper between them. These terminal lobes are jointed to the
labium, a little distance behind its tip, as can be seen in fig. 7, which is a cross-
section of the labium a trifle anterior to the actual centre of motion of these
joints. The section of that portion of the labium which extends forward to form
its tip is seen in the middle of the figure, just below the section of the maxille
(mx). Outside the section of each lobe is seen the section of a portion of the
exterior edge of the labium itself, which here forms a double socket, or pair of
acetabula, into which the heads of the two labelle are set. Each of the lobes of
the labium,—the labella,—is provided with an extensor and flexor muscle (fig.
7, me, and mf), and is attached to the labium by a true joint.
42 MOSQUITOES OF NORTH AMERICA

“The labium has for function, for the most part, the protection of the fine
setee which form the true piercing organ of Culex. In the females of Culex
proper, the protective sheath is formed by the labium alone. When the mosquito
has found a place which suits its taste for piercing, it plants its labelle firmly
upon the spot, and a moment later the labium flexes backward in its middle, the
sete, firmly grouped together, remain straight and enter the skin, while the two
labellee guide them, much as a carpenter guides his bit with his fingers while
boring a piece of plank. When the set of Culex have entered the skin to nearly
their full length the labium is bent double beneath the body of the insect, the
labellee still holding the base of the sete at the point where they enter the skin.
When the mosquito wishes to withdraw the sete it probably first withdraws the
two barbed maxille beyond the other sete, that is, so that their barbs, or
papille, will be kept out of action by the mandibles and hypopharynx; then it
readily withdraws the sete, perhaps aiding their withdrawal by the muscles of
the labium, for, during the process of extracting the sete from the skin, while
they are slowly sinking back into the groove upon the upper side of the
straightening labium, the mosquito keeps the labelle pressed firmly upon the
skin.

“The mouth-parts of Culex, as above described, are suspended under a
clypeus, or epistom, which is figured from the side in fig. 1, c; from above in
fig. 2, c; in length-section in fig. 11, c; and in cross-section in fig. 9, ¢. This
clypeus is the hood-shaped forward continuation of the lower part of a A-shaped
piece of chitin which forms the framework of what may be termed the ‘ face’ of
Culex; right and left of the upper portion of this framework pass out the an-
tennal nerves, the antenne being supported by the framework itself.

“The pharynx (fig. 11, p), the tubular continuation of the epipharynx above
and the hypopharynx below, as it passes backward, beneath the centre of the
A-shaped framework, turns somewhat upward, is narrowed to the valve pre-
viously described, then widens slightly again, and, as cesophagus (fig. 11, oe)
passes through the cesophageal nerve-ring, in which it is supported by three
delicate chitinous rods, which lie, one longitudinally on its ventral surface, and
two to the right and left on its dorsal surface. Just posterior to the cesophageal
nerve-ring, directly above the nerve-commissure which connects the infra-
cesophageal ganglion with the first thoracic ganglion, the cesophagus suddenly
expands into an cesophageal pump, or bulb, the longitudinal section of which is
shown in fig. 11, 6; the cross-section in fig. 10, 6. This bulb, which is the chief
sucking organ in the female Culex, and which I have found in no other dipteron,
is supported by three longitudinal chitinous rods, which are stouter continua-
tions of the three rods supporting the cesophagus through the nerve-ring. These
rods (fig. 10,7) have between them chitin-plates (fig. 10, +) which are suspended
from the rods by elastic membranes. On the dorsal plate is inserted a double
muscle, or a pair of muscles (bm), the origin of which is in the dorsal part of
the chitinous shell of the head. Each of the lateral plates has inserted on it a
muscle (bm’), the origin of which is in the chitin of the lower lateral regions of
the head. The origin of each of these muscles is in the so-called occipital
region of the head, that is, behind the eyes. By the simultaneous contraction of
these muscles (bm and bm’), the lumen of the esophageal bulb is enlarged, and
the blood flows into the bulb from the pharynx, and, upon their relaxation, the
elasticity of the chitinous walls of the bulb, drives the blood, which can not
return to the pharynx because of the closing of the valve at v (fig. 11), into the
stomach.

In the male.

“ The mouth-parts of the male of Culex have not been described, as far as I
know, with any degree of accuracy, although, since Swammerdamm’s time, the
PROBOSCIS OF MALE 43

males have been distinguished from the females, by all scientific entomological
a on the subject, by means of their feather-like antenne and maxillary
palpi.

“The proboscis of the male of Culex pipiens, the only species the male of
which I have studied, is slightly longer and slenderer than the corresponding
organ inthe female. The sete are fewer in number and less completely sheathed
by the labium than in the female; they consist of a well-developed labrum-epi-
pharynx and two slightly developed maxilla. The mandibles are absent, and
the hypopharynx coalesces with the labium (fig. 12 h and /). The labium and
maxillary palpi are more densely covered with hair and scales than they are in
the females, and they contain muscles; the other mouth-parts, the sete proper,
are naked, chitinous, and contain no muscles. In comparative length the mouth-
parts may be arranged, longest first: maxillary palpi, labium and labrum-epi-
pharynx, maxilla ;—in comparative size they may be arranged, largest first :
labium, maxillary palpi, labrum-epipharynx, maxille. The relative position of
the mouth-parts of the male is different from that in the female (compare figs.
8-9 with 13-15) in that the short, rudimentary maxille are pushed out sidewise
to allow the hypopharynx to coalesce with the labium. In the male the cesoph-
ageal pump, or bulb behind the nerve-ring, fails, and the sucking of fluids
must be done by the pharynx alone, as it is done in most diptera.

“ The labrum-epipharynx is nearly the same in general form and structure in
the male Culez as it is in the female, it is a trifle longer and slenderer, but the
same figures (5, Ir-e, and 6) will serve for the tips of both. In section (fig. 12,
lr-e), the labrum shows a groove on its upper surface, which deepens as it nears
the base (fig. 13, Ir-e). The apical four-fifths of the labium contains no other
seta than the labrum-epipharynx, as seen in fig. 12, which is a section at about
the middle of the proboscis. At the base of the labrum-epipharynx are pharyn-
geal muscles similar to those found in the female, and with similar insertions
and origins, except that the median muscle (fig. 15, pm’) is not divided into
three parts as in the female (fig. 9, pm’).

“ The hypopharynx is, throughout its whole length, joined to the labium, and
thus necessarily pushes the maxille, which would normally lie between it and
the labium, to one side. (See fig. 13, 4 and mz.) The hypopharynx shows, in
section (fig. 18-15, h), the same chitinous rod through the middle as in the
females, but I was unable to detect any channel for saliva through this rod.

“The maxille are very thin lamelle of transparent chitin, about one-fifth as
long as the labium, and so delicate as to be easily overlooked. Although as broad
at the base as is the tube of the epipharynx, they taper regularly from their base
to their fine tips.

“The maxillary palpi are five-jointed, very hairy toward the tip, much longer
than they are in the female, and when at rest their basal portions cover the
labrum-epipharynx and maxilla in the sheath of the labium.

“The labium of the male Culex is similar in general structure to that of the
female, if one considers it together with the hypopharynx. It is, however,
slenderer, more densely covered with scales, has a shallower groove for the recep-
tion of the labrum-epipharynx, and has a joint near the middle. The slender-
ness of the labium in the male extends itself to the labelle. (Compare fig. 4, 1b,
with fig. 3, 7b). The groove of the labium of the male increases in shallowness
from tip to base; at the middle of the proboscis (fig. 12) it is so shallow that it
fails to fully protect the labrum-epipharynx, and at its base (fig. 13) it is so
shallow that the other mouth-parts rest only on top of the labium. To make up
for this deficiency of protection by the labium, the maxillary palpi, as was pre-
viously mentioned, cover over the upper side of the enclosed parts (see fig. 13),
and thus, although free from the labium, form a part of the protective sheath,
44 MOSQUITOES OF NORTH AMERICA

which, in the female, is formed by the labium alone. Whether the joint near the
middle of the labium of the male Culex is true or false I cannot say, since I
have never seen it bent by the insect itself; its appearance is that of a true joint.
Like the labium of the female, that of the male has two longitudinal main
tracheal stems (figs. 12-14, tr), and two rows of longitudinal muscles.”

Kraepelin expressed the opinion that the labrum is not formed by the union
of two pieces, the labrum and epipharynx, but that it is an evagination of the
head and in consequence necessarily hollow. “It can therefore, as all body-
appendages are evaginations and consequently hollow, impossibly be interpreted
as the fusion of an upper and lower lamina.”

Becher was of the same opinion and states that the so-called epipharynx of
the Diptera is never found as a free part; he calls the part the lower lamella of
the labrum.

Meinert has traced the course of the salivary duct and found that it differs in
the two sexes. His interpretation of the hypopharynx does not agree with that of
Dimmock. In the female Meinert found that the salivary duct penetrates the
posterior part of the hypopharynx; before entering it forms a large receptacle
from the upper part of which a strong muscle extends to the under side of the
pharynx. “In the male the hypopharynx does not protrude but is very short
and rounded anteriorly and the salivary duct runs through the entire sheath
[labium] along the under side of its floor until it terminates in the tongue.”

Wesché considers the hypopharynx of the male as long, like that of the fe-
male, and the “ tongue” of Meinert, protruding between the labelle, as its apex.
He speaks of the ciliation of the free apex, which he states to be present in all
males, as “ a surprising reversion ”; perhaps it can be explained as readily as an
adaptation to the feeding habits of the male. One gets the impression from
Wesché’s paper that he believed that the hypopharynx is free in the male
throughout its entire length ; such does not, however, appear to be the case. He
figures the abnormal mouthparts of a male Anopheles maculipennis which ap-
proach those of the female. Not only the mandibles and maxille are present, but
also a free hypopharynx which extends to the tip of the proboscis.

The mandibles of Diptera are present only in the females of the blood-sucking
orthorrhaphous forms. Becher, whose work has been criticized for its inexact-
ness, states that two parts can usually be clearly distinguished in these organs:
“a basal piece, which lies in the interior of the head, and the mandible proper,
which can be moved upon this base by means of a joint.” None of the students
who have followed exhaustive methods appear to have detected any such joint.
Becher’s interpretation of the mouthparts is at variance with the commonly
accepted homologies in various details but his paper is neither clear nor con-
vincing. Furthermore, he commits the error of basing his views on studies of
the mouthparts of the higher Diptera and interpreting the lower forms from this
standpoint ; thus we can, with the more propriety, pass over a detailed considera-
tion of his work. It may, however, be pointed out in passing, that while Becher
Tightly, we believe, rejects the idea, held by some of the earlier authors, that the
maxilla and even the mandibles may enter into the composition of the labium
MEINERT ON MOUTH-PARTS 45

of the Diptera, he adopts Burmeister’s view that the labellz are homologous with
labial palpi. None of the recent authors have concurred in this view. ‘The
three terminal lobes of the labium have been designated by Kellogg, who has
given a very clear exposition of the mouthparts of the Nemocera, as, medianly
the fused glosse, and, outwardly the paraglosse. This interpretation has been
followed by Wesché and others. Other details, such as the attempts to find
homologues of the components of the maxille and labium of mandibulate in-
sects, can be passed over as purely hypothetical.

All the authors who have endeavored to homologize the mouthparts of the
Diptera with those of the mandibulate insects have, with one exception, agreed —
as to the fundamental parts, the labrum, hypopharynx, mandibles, maxille, and
labium.

John B. Smith, in a paper published in 1890, took an entirely different view
and defended this in a further paper which appeared in 1896. This interpreta-
tion has been adopted in a recent popular book on mosquitoes. He used the
mouthparts of certain highly specialized Hymenoptera and Coleoptera as a basis
for his homologies. Smith found in Simulium, apically in the labrum, a pair of
small dentate chitinous structures which he considered rudimentary mandibles ;
these structures appear to be absent in all other nemocerous Diptera. He sup-
posed, not only that the parts usually considered mandibles are maxillary, call-
ing them laciniex, but that maxillary structures entered largely into the composi-
tion of the labial sheath. The parts supporting the labelle are said to be part of
the maxille, the subgalex, the labellee themselves the galee. The labium is rep-
resented as a free piece, enclosed by the galeal structures, and the hypopharynx
united with it. Smith’s work has been adversely criticized by the students of
dipterous mouthparts and moreover bears clear evidence that it was based merely
on rough dissections; only recently Leon, in a paper on Stmulium, discusses
Smith’s homologies and points out the relationships of the parts in accordance
with modern studies.

Meinert developed views at variance with all the other students and did not
believe that the mouthparts of the Diptera are homologous with those of man-
dibulate insects. While his interpretation is in the main controverted by the
histological work of Kellogg, it still seems of sufficient interest for a brief notice,
all the more as it has been generally ignored.

Like all other modern investigators Meinert recognized that generally the
mouthparts of insects are homologous with the legs of the body and that, there-
fore, they are the exponents of distinct metameres. He demanded, however,
that to identify them with these, and those of the different orders of insects with
each other, something sufficiently characteristic should be in evidence and he
says:

“I find this in the presence of a metamere and in the free jointing of the ex-
ponents to the under side of such a metamere, and according to this criterion
I test, whether the mouth-parts (that is the mouth-parts proper, the paired ones)
are homologous with appendages of the body on the one side, or among them-
selves on the other.”
DEVELOPMENT OF MOUTH PARTS 47

adult insects of incomplete metamorphosis. There remains to determine the
relations of the larval mouth parts of Simulium with its very different imaginal
mouth parts.

“In selecting flies for the study of the postembryonic development of the
mouth parts I have chosen two which in the imaginal condition possess all the
parts possessed by any fly, and these parts in as generalized condition as ig to be
found in the order, and which also possess in the larval stage a similarly full
complement of mouth parts. Such larve as those of the Muscide, with their
problematical hooks and lack of other parts, and such imagines as the muscid
flies, with no parts left except proboscis and maxillary palpi, are impossible for
the determination of the relation between larval and imaginal parts. From the
mouth parts of the imaginal Simulium and of other nematocerous forms it is

 

Fic. 1.—Sagittal section through head of old larva of Simulium sp., showing
forming imaginal head parts within.

i.¢., larval head wall; i.d., imaginal derm; La., larval antenna; i.a., imaginal
antenna ; 7.¢., imaginal eye; i.md., larval mandible; ene mandible ; l.ma.,
larval maxilla ; i.ma., imaginal maxilla ; 1.1i., larval labium; 4. ,» imaginal labium,

not difficult to trace the evolution to the specialized muscid conditions, and if
the mouth parts of Simulium and similarly equipped flies can be interpreted,
the various members of the dipterous series culminating in the muscids can. So
in Simulium and Blepharocera I have found suitable forms for study ; both with
females possessing the so-called mandibles, both with maxille and labium well
developed in both sexes, and both with larve equipped with biting mouths with
unmistakable mandibles, maxille, and.labia, and in one case, that of Simulium,.
with the embryonic development of the larval mouth parts fully traced and the
homologies certainly * determined.

’“ Simulium sp.—tIn the female imago ¢ the mouth parts consist of a short
liplike labium composed of a short basal sclerite and three terminal lobes, being
the two large paraglosse and a median short membranous lobe, the fused gloss ;
a pair of maxille, each consisting of a basal sclerite, a long five-segmented
palpus, and a single pointed, bladelike terminal lobe reaching nearly to the end

 

* Metschnikov, E. Embryologische Studien an Insekten. Zeitschr. f. wiss. Zool., vol. xvi.
1866; embryonic development of mouth parts of Simulium described on pe. 392-421.

+ “In describing the adult mouth I shall assign to the various parts those names which, from
my earlier study of the comparative anatomy, seem correctly used, and the use of which is
confirmed by the results of this ontogenic study.”
48 MOSQUITOES OF NORTH AMERICA

of the third palpar segment, serrate on its inner margin at the tip and better
developed than in most Nematocera; and a pair of short mandibles, broad, thin,
and weakly chitinized. As in other nematocerous flies, there is a well-developed
labrum-epipharynx and an elongate flattened hypopharynx. In the males the
mandibles are wanting.

“Tn the larva the mouth is of the biting type, with short-toothed and heavy
mandibles, short, jawlike maxilla with distinct one-segmented palpus, and a
small, strongly chitinized labium or labial plate. In addition, labrum, epi-
pharynx, and hypopharynx are all well developed. : :

“The head of the larva having a thoroughly opaque, strongly chitinized cuticle,

yh

  

   
 

te J ai SF fe
: hae , : ‘
y i PSM.
4 ! Imd.
lmxp — Lhyp.j tmd.
2.mad.
Fic, 2.—Frontal section through the head of old larva of Simulium sp., show-
ing forming imaginal parts.
., larval cuticle; ¢.d., imaginal derm; I.md., larval mandible; ¢md., imaginal

Le.
mandible ; Lme., larval maxilla; t.ma., imaginal maxilla; l.ma.p., larval maxillary
palpus; Lhyp., hypopharynx.

it was impossible to clear whole heads sufficiently to make visible the develop-
ing imaginal head and its parts, so that the method of sections had to be relied
on to reveal the internal conditions. These sections of heads of larve of various
ages show plainly that the general method of development of the imaginal parts
within the larval head, and the correspondence between forming imaginal parts
and the corresponding larval parts already noted in the other orders of holo-
metabolous insects, hold good in the Diptera. Fig. 1 shows in sagittal longitud-
inal section the forming imaginal head parts within the larval head. This sec-
tion shows particularly well the relation of the forming imaginal antenna to the
larval antenna. In the larva the antenne are very small compared with their
size in the imago, and the imaginal antenna is thus forced, in its development, to
occupy a region in the larval head not included in the larval antenna. But the
tip of the imaginal organ lies fairly within the larval organ, thus indicating by
correspondence in position, what is plainly obvious from anatomical considera-
tion, the homology between the larval and imaginal organs. Similarly the
forming imaginal mouth parts are to be found in unmistakable correspondence
or homologous relation with the larval parts. By tracing the development of
the parts, marked in fig. 1 as the forming imaginal mouth parts, through larve
MODIFICATIONS OF MOUTH-PARTS 49

of successively older ages to pupation and the achievement of the definitive
imaginal condition of these parts, it is certain that the parts marked respect-
ively imaginal mandible, imaginal maxillx, and imaginal labium, lying respect-
ively in the larval mandibles, maxille, and labium (with homologies firmly
based on ontogenic basis) , do develop into those definitive imaginal parts named
mandibles, maxille, and labium. .. . Fig. 2, a horizontal, frontal section
through the head of a Simulium larva, shows also the forming imaginal maxilla
and mandibles within corresponding larval parts.”

Wesché has found that abnormal male Culicids occur with all the trophi
present, as in the females, although in these cases the maxille and mandibles did
not extend to the tip of the proboscis. Such males, to conclude from Wesché’s
work, appear to be not uncommon. Examining a number of males of different
species, he found an abnormal Anopheles and also a male Culex pipiens with all
the parts present.

It would seem that the mandibles and maxille may be absent in the female of
certain species which do not suck blood. Such appears to be the case with the
female of Harpagomyia splendens, recently described by De Meijere. This
curious Javan species feeds upon honey which it obliges the ant, Cremastogaster
difformis, to disgorge. In this mosquito the hypopharynx is free, as usual, but
appears to lack the salivary duct. It is interesting to note that early in the
pupal stage both mandibles and maxille can be readily seen in the developing
imago. These gradually retrograde, until, by the end of the pupal period, they
have become wholly atrophied, just as has been shown to occur in the develop-
ment of the males of the blood-sucking forms.

While the external appearance of the proboscis is frequently described, we
know practically nothing of the modifications of structure in the different species
or genera—Wesché states that in Anopheles the mandibles are serrated at the
tip. The sheath of the proboscis shows much variation in length and diameter
in the different species and it is frequently expanded towards the apex. The
labellz also show much difference in shape and in details of structure but these
need not be described. In Megarhinus the sheath is unusually rigid, tapering,
becoming very slender at the tip, and the labelle: are narrow and much elongated.
In this genus, in which both sexes feed wholly upon the honey of flowers, the
labium can not be bent as it can in the forms which suck blood.

In the males of many species the sheath of the proboscis shows a suture out-
wardly from the middle. Usually it is indistinct, but in the male of Deinocerites
there are chitinous margins connected by a membranous strip as in a true joint.
Its significance is not clear; perhaps it indicates the limits of the true labial
structures. It may be mentioned in this connection that Meinert considered
the sheath of the proboscis as of composite origin and formed mainly by the
greatly produced portion of that part of the head which he considers the ventral
plate of the first metamere.

It has already been shown that there is a salivary duct in connection with the
hypopharynx. Macloskie found that there were two sets of salivary and poison
glands in connection with this duct. The glands are situated in the anterior
ventral part of the thorax and each set consists of three glands, two of which
50 MOSQUITOES OF NORTH AMERICA

are ordinary salivary glands and the third, between the other two, differs in ap-
pearance and structure and secretes the poison. Each set of glands discharges
into a very fine duct and these ducts unite in the back of the head and continue
forward as a single duct through the ventral region of the head. Macloskie’s
studies were made with Aédes teniorhynchus and a species of Anopheles.

At the base of the hypopharynx is the salivary pump into which the salivary
duct empties, to be continued beyond it into the hypopharynx. Macloskie failed
to recognize its true character and called it the salivary “ reservoir.” Its true
character appears to have been first recognized by Annett, Dutton, and Elliott.
The organ is fully described by Nuttall and Shipley, from whom we quote. As
yet the organ has only been demonstrated in Anopheles.

“. .. The structure is more than a receptacle, it constitutes a pump, the
mechanism of which corresponds to that of the pharyngeal pump in a sense, that
is, it depends upon the action of powerful voluntary muscles which overcome the
elasticity of a chitinous membrane which, when released by the muscles becom-
ing relaxed, rebounds or returns to its original form, as a bow does when the pull
on the bow-string is released. . . . It will be seen then that the common salivary
duct ends (lumen 5,) in the centre of the chitinous membrane, the junction be-
ing strengthened by a chitinous thickening of annular form. The membrane is
continuous with a highly chitinized cup, which tapers anteriorly, and is continu-
ous with the hypopharynx, an opening therein connecting it with the groove
described above. . . . Spicules of chitin occur about the duct on the pump-
membrane, these serving for the attachment of the powerful muscles presently
to be described. The thickened chitin surrounding the membrane is flattened
on its dorsal surface which is applied to the floor of the buccal cavity. The
pump-membrane is covered in the centre by the insertion of two stout bundles of
muscle-fibres which pass backwards, parallel with one another, to their origin
on the anterior surface of the chitinous flange which projects ventrally from the
floor of the buccal cavity. When the muscles contract a partial vacuum is
produced within the cup, saliva flows in from the glands, and when they relax
the membrane rebounds forward, driving the saliva out of the cup into the
salivary channel along the hypopharynx.”

Leon, who investigated this organ independently, gives a description at vari-
ance with that of Nuttall and Shipley. He found that the salivary duct empties,
not into the center of the posterior membrane of the cup, as described by Nuttall
and Shipley, but into the side of the chitinous cup. The pumping device Leon
describes as follows:

“The mouth of the cup, which is directed posteriorly and ventrally, is covered
by an elastic chitinous membrane which is pushed back into the interior of the
cup like the bottom of a champagne-bottle. Outside, in the middle of this mem-
brane, a chitinous piston-rod is attached. This has the form of a round concave-
convex dise and is more darkly colored ; the convex side of the disc is attached to
the elastic membrane, while in the middle of the concave side the rod is fixed.
. . . The posterior end of the rod is thickened and muscles are attached to it.”

THE PALPI.

The palpi, as they appear in both sexes of Culea, have been described in the
foregoing in connection with the other mouthparts. Great diversities of
opinion have been expressed by the different students as to their structure and
MAXILLARY PALPI ol

the number of the joints. They show great diversity in the different genera and
in the species. They differ greatly in length, in shape, and in the number of
joints. The relative length of the palpi, without reference to the number of
joints, has been generally considered as a character of primary importance in
classification. Beyond that there has been general disagreement as to the
number of component joints. Dimmock, whom we have quoted, considered
the palpi of Culex pipiens as four-jointed in the female, five-jointed in the male.
Meinert states for the same species, three-jointed in the female, four-jointed in
the male. Both these authors found that in other species a small additional
joint was present in the females. Ficalbi considered that in Culex the palpi of
the female are three to four-jointed, those of the male three-jointed. Wesché
considered the palpi four-jointed in both sexes. Felt states that in most
Culicide the palpi are five-jointed in both sexes, except in certain females “ when
the rudimentary fifth appears to be wanting.” Theobald, in Genera Insectorum,
states that the palpi of the Culicide have from one to six joints.

The idea that the number of joints in the palpi is constant within groups and
of great classificatory importance has been very generally accepted. The state-
ment that the palpi of the Nemocera are four or five-jointed, which originated
with Latreille (1809), has been widely followed with but little modification.
Becher considered the palpi of the Nemocera four-jointed and called the basal
part “ Tasterschuppe,” the equivalent of the palpifer, or, in its absence, of the
maxillary stipes. Williston, in the introduction to his Manual of North Ameri-
can Diptera (third edition, 1908, page 26), states of the palpi of the Diptera:

“Perhaps the most important of all the mouth-parts, from the systematic
standpoint, are the maxillary palpi. . . . They are variously described as being
composed of from one to five joints. There are never more than four articulated
joints, the basal joint being merely a process of the plate bearing the maxille.
The tendency in diptera is toward their entire loss, and in the more highly
specialized families there is never more than one joint.”

Farther on (p. 65) he says of the Nemocera: “ Palpi usually more or less
elongate, composed of from one to five, usually four, joints, rarely absent.”
While there is undoubtedly a reduction in the palpi parallel with specialization,
this reduction has taken place independently at different points, and, except in
a very broad way, the palpi can not in themselves be considered as a safe index
of relationships. The ideas of systematists have been based largely upon the
study of a few typical forms, and no attempt appears to have been made to test
their constancy within a family. In fact, within the Culicide the palpi may be
said to be remarkably unstable in character. They range all the way from forms
with several well-defined joints, as Anopheles, to forms in which they are re-
duced to a small club-shaped organ without trace of jointing. In fact, the
homologizing of the palpal joints of the different forms, which Felt attempted to
carry out, assuming five joints for the more generalized forms, is beset with pe-
culiar difficulties. The conditions in the basal portion of the organ, which have
generally been considered as true joints, are not clearly defined or sufficiently.
uniform within the group to be so interpreted. We have not found any mos-
52 MOSQUITOES OF NORTH AMERICA

quitoes in which either one or both of the two supposed basal joints are differ-
entiated in such a manner that they may be called true joints. We doubt that
these correspond to the two basal joints of the four-jointed palpus of the more
primitive Chaoborus; the integument is of the same character throughout,
simply that there is less chitinization at the “ joints.” Furthermore, it does not
seem plausible that joints would tend to disappear at the very point where they
would be most in use and most needed.

Should we accept the two basal modifications as true joints, we would then
have, in the female Anopheles, which has in addition three well-defined joints,
mosquitoes with six-jointed palpi. If, on the other hand, we carry out strictly
the idea that these basal joints are secondary modifications, we must consider
all that part of the palpus below the first true joint as a prolongation of the
basal structure and a part of the maxilla itself. Thus we would have to con-
sider the first “ long joint ” of Anopheles, there being no jointing apparent at the
base of the palpus, as belonging to the basal structure. The palpi of Anopheles
would then be three-jointed in the female, two-jointed in the male. In the
normal Culex pipiens there would be but a single true palpal joint in the female,
two in the male. In the higher forms, where there has been a reduction to a
club-shaped organ, this appears to have been produced, not by fusion of the
joints, but by their loss. This unjointed club would then represent the basal
structure.

This process of reduction, first in the length of the joints, then in their num-
ber, can in fact be traced progressively through the genera and species of mos-
quitoes. The arrangement we have adopted in our classification, although it was
founded upon other characters without reference to the palpi, follows very closely
this process in the two tribes. It is interesting to note that this reduction has
been the most rapid in the female, where the functions of the mouth-organs are
of the most importance, and that in the majority of species the palpi of the male
show the more primitive condition. Thus Anopheles, in which the palpi are
long in both sexes and show several joints, is to be regarded as the most primitive
mosquito, while such forms as Uranotenia and Sabethes, with greatly reduced
and unjointed palpi, must be considered highly specialized.

We have already, on a previous page, called attention to the view of Meinert,
apparently supported by Kellogg’s histological work, that the palpi of the
Diptera are not homologous with the maxillary palpi of other insects but are
rather modifications of the maxille themselves. As this view has some bearing
on the interpretation of these organs and the number of joints, we quote Meinert
in part:

“_. . The palpi are regarded by everybody as corresponding to the maxillary
palpi of the other insects; but I shall here make some comments on this. The
maxillary palpi always originate from a maxillary trunk, which, through an
intermediate joint, the cardo, springs from the metamere. They are, in other
words, only the outer joints (corresponding to the foot of the exponent. In
the Diptera, on the other hand, the palpi originate directly from the metamere;

and while in the several-jointed palpi the first joint might be regarded as a
modified cardo, and consequently the outer joints of the palpi as homologous
REDUCTION OF PALPI 53

with the maxillary palpi, it is different when the palpi consist of only two, or
even of a single joint, as is the rule in the Diptera, for there will then be no
joint left to explain as maxillary palpus. I therefore prefer to regard the palpi
of the Diptera as homologous with the entire maxille of other insects, only that
they are oftenest unjointed and not divided into different components. Only in
Simulium, Tipula, and Limmobia I have thought to find an indication, in the
before mentioned appendix at the base of the palpi, of the different working
divisions of the exponents of the second metamere of other insects.”

The palpi are variously modified in the different forms. In Anopheles and in
the males of a great many other forms the palpi about equal the proboscis in
length, or even exceed it. In most of these forms the palpi are slender, particu-
larly in their proximal halves, and furnished with false joints to increase their
flexibility so that they can be folded back when the insects are feeding.

In Megarhinus, however, where the palpi are less in the way, on account of the
downward-curved proboscis, they are stout and quite rigid, without basal false
joints, and the joints are armed near their apices with heavy spines. In the
males of Anopheles and of most species of Culiseta the palpi are enlarged
apically into a distinct club. In Anopheles the club is composed of the outer
two joints, while in Culiseta it may be composed of these same two joints or of
the last joint alone.

In the males with long palpi of many species of Culex and Aédes the outer
half of the palpi is more or less thickened and densely hairy, the last joint, how-
ever, generally tapering to a point; the last two joints are usually curved upward.

In Megarhinus and Bancroftia we begin to get a reduction in the female palpi,
and this occurs principally in the terminal joint. In the American species of
Megarhinus the palpi of the female are about two-thirds the length of the pro-
boscis, while in the Old World species of this genus the reduction has gone still
farther and they are sometimes less than one-fourth the length of the proboscis.
In the females of both the New and the Old World species of Megarhinus there
is a minute terminal joint, and the number of joints is the same.

In Bancroftia the palpi of the female are about two-fifths the length of the
proboscis, the terminal joint small; in the case of one species (B. fascipes) the
terminal joint is about three times as long as wide, in another (B. signifer) it is
nearly globose. In the male of this last-named species, although the palpi are
as long as the proboscis, the last joint is similar in character to that of the
female.

In the males of most species of Aédes and of Culex the palpi are longer than
the proboscis, curved upward, their outer halves densely hairy, the last joint
long and tapering. In certain species of Aédes the palpi of the male are slightly
shorter than the proboscis, straight, less hairy, the last joint long but blunt at
the tip. In Aédes fuscus the palpi of the male are very short, in fact shorter
than those of the female, and the terminal joint is indicated by a flattened
tubercle. In the related genus Stegoconops the reduction of the male palpi has.
become more general. In 8. equinus the palpi of the male are about three-
fourths the length of the proboscis ; in S. albomaculatus the palpi are practically
alike in the two sexes, short and with a minute terminal joint.

5
o4 MOSQUITOES OF NORTH AMERICA

In certain species of the genus Culea a similar reduction of the male palpi
is found. In Culex latisquama the palpi of the male are about half as long as
the proboscis. The reduction is in the apical portion; the apical joint is sub-
globose, the one supporting it is less than three times its own diameter in length.
In the female of this species the palpi are about one-fourth the length of the
proboscis, but, as in the male, have a minute terminal joint. In Culex bisul-
catus the palpi are slightly less than half the length of the proboscis in both
sexes. In the female there is a single true joint, which makes up more than
half the length of the entire palpus. In the male we have been unable to dis-
cover any differentiated joint except the minute terminal one.

In Uranotenia reduction has gone to the extreme. In both sexes of U. sap-
phirinus the palpi are very small, projecting but slightly beyond the clypeus,
club-shaped and unjointed.

In the females of most Culicini the palpi are short, although differing much
in length and configuration in the different species. They consist of a basal
portion, which in most cases shows a triple false-jointing ; beyond this there is a
stout joint and in many species this bears at its apex another minute joint.
Sometimes there is even what appears to be a second minute joint, inserted upon
the other, but this is with little doubt produced by constriction of a single joint.
Such a condition exists in Mansonia fasciolatus, as has already been indicated
by Neveu-Lemaire, It may also occur as an abnormality, as in the case of a
female Culiseta annulata figured by Dyé and Neveu-Lemaire. In the species in
which the minute terminal joint is usually absent specimens may occur with this
joint present. Dyé and Neveu-Lemaire describe such palpi in a female Culex
pipiens. We have a Culex tarsalis with the same abnormality.

In Deinocerites and Dinomimetes the palpi are short in both sexes, but show
considerable diversity of structure in the different species. In Deinocerites
pseudes female there is a distinct terminal joint, more than half the length of
the entire palpus. In the male of this species there is in addition a minute apical
joint. The palpi of the male D. troglodytus are similar but the apical joint is
still more minute, while in the female there is no distinct jointing. The palpi
of D. cancer are unjointed in both sexes. In Dinomimetes epitedeus there is a
single joint in both sexes.

In the group of Sabethini the reduction of the palpi is far more general and in
most species these organs are short and unjointed in both sexes. In the forms
examined the female palpi always proved unjointed, and although only a few
forms have been studied it is evident that such is the rule in this group. In
Joblotia digitatus the palpi are long and slender in the male, distinctly jointed ;
in the female the palpi are short and unjointed. In Lesticocampa the palpi are
very slender. They may be long or short in the male, according to the species,
but they are jointed like those of the male Joblotia. The palpi of the female,
as in other sabethids, are unjointed.
STRUCTURE OF THE THORAX 0D

THE THORAX,

The terminology of the parts of the thorax of mosquitoes is very confused and
shows that its structure has not been generally understood. We, on this account,
requested Mr. R. E. Snodgrass, formerly of the Bureau of Entomology, U. 8.
Department of Agriculture, who has made a study of the homologies of the
thorax of insects of different orders, to prepare the following study, with figure,
of the thorax of a mosquito, Psorophora ciliata (see plate IIT).

The thorax of the mosquito is conspicuously wedge-shaped, the base being
uppermost and forming the large rounded dorsum of the thorax. The triangular
sides form the pleura, while the apex is ventral and carries the legs. The wings
(w,) are inserted on the upper parts of the sides much behind the middle, so
that the greater part of the thorax is in front of them, but the balance of the
entire body is preserved by the long, slender abdomen extending posteriorly.
The second wings are represented by the halteres (w,) which, of course, take no
part in the mechanism of flight. Consequently the great muscles of the meso-
thorax alone afford the motive power of flying. The active function of the pro-
thorax and the metathorax is the support of the front and hind legs. Hence,
both of these segments consist of little more than anterior and posterior collars
against the great mesothoracic mass. The consolidation of the three segments
is so complete that many entomologists find it difficult to define their limits with
certainty.

Two conspicuous points on each side of the thorax are the spiracles (18p and
2Sp). Hach is a large black-rimmed aperture situated in a membranous area,
one near the middle of the anterior half of the side, the other somewhat behind
the middle of the posterior half. Since, in most adult insects, these thoracic
spiracles are situated in the intersegmental membranes, it is a difficult matter to
decide to which segment each belongs. The second is nearly always regarded
as metathoracic, but entomologists are divided in opinion as to whether the first
is mesothoracic or prothoracic. Amongst morphologists, however, the first view
seems to have the greater support. However, this question is of little importance
for the more practical needs of the systematist, who may avoid the difficulty by
referring to them simply as the first and second thoracic spiracles.

The Prothoraz.—The lateral walls of this segment consist of three plates
(T,, Eps,, and Epm,). Closely associated with them is a large cervical sclerite
(mt) lying on each side of the neck and forming a support for the head an-
teriorly. The most conspicuous of the prothoracic plates is the prominent oval
lobe (T',) beneath the projecting anterior end of the mesotergum. This very
probably is a lateral part of the protergum, for it is connected by a median
narrow transverse bridge in front of the mesotergum with the corresponding part
of the opposite side. These two lobes are called “ patagia” by Christophers, a
name properly belonging to the prothoracic tergal appendages of Lepidoptera,
but of doubtful propriety when applied to similar parts in the mosquito, because
there can be no homology between them. Connected with the lower end of the
protergal lobe is a stalk-like piece which expands ventrally into a larger plate
EXPLANATION OF Puiate III.

The individual segment of the thorax to which any part belongs is indicated by the
small figure placed behind and below its symbol. The abdominal segments are
distinguished by Roman numerals placed before the symbols of the parts. Arabic

numerals placed before symbols signify numerical order of repetition. is
Ant, antenna. Prb, proboscis.
AxC, axillary cord of wing base. PS, pleural suture.
Clp, elypeus. psc, prescutum.
Cu, coxa. S, sternum.
CzP, pleural coxal process. scl, scutellum.
E, compound eye. set, scutum.
Epm, epimerum. Sp, spiracle.
Eps, episternum. T, tergum.
eps,, detached part of episternum of | W., wing.
mesothorax. W,, halter.
Lb, labium. WP, pleural wing process.
mi, cervical sclerite. a, small plate of mesopleurum bearing
MzxPip, maxillary palpus. articulation of coxa.
P, parapterum. b, accessory plate of mesoepimerum.
PN, postnotum (postscutellum). c, lower part of metapleurum.

56
PLATE III

PUBLICATION 159

 

 

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Thorax of Psorophora.

 
MESOTHORACIC STRUCTURES 57

(Eps,) above the base of the front coxa (Oz,), and which is connected by a
transverse arm with the prosternum. (The last is not visible in side view.)
The third prothoracic plate (Hpm,) lies behind and above the other two and is
much larger than either of them. It extends posteriorly almost to the first
spiracle (1Sp) and sends a narrow strip downward to the precoxal membrane.
It might be questioned whether this plate does not really belong to the meso-
thorax, but a little comparative study of other flies will make its morphological
relations clear. It will be observed that in Psorophora the anterior coxa is not
directly articulated to the side of the prothorax, being connected with it only
by a wide membrane. In most other flies, however, it is articulated in normal
fashion to the propleurum, at the ventral end of the pleural suture. In the lower
flies this suture separates two distinct pleural plates—the episternum and the
epimerum. In Tipula the first spiracle is much farther forward than in the
mosquito and lies on a line which is clearly the boundary between the prothorax
and the mesothorax, the epimerum of the prothorax being in no way expanded
or specially developed. In Bibdio the first spiracle is farther back than in Tipula
and the epimerum is much extended posteriorly. In Psorophora, finally, this
character is still more exaggerated, the first spiracle being halfway between the
base of the wing and the front of the mesotergum, while the epimerum of the
prothorax forms a large lobe reaching posteriorly to the spiracle, though its
ventral extremity is reduced to a narrow band close to the posterior edge of the
plate in front. The latter (HZps,) we can, therefore, identify as the episternum,
and the line (PS,) between the two plates as the pleural suture. The only dis-
tinctive character in the prothorax is, therefore, the separation of the coxa from
its pleural articulation.

The plate (eps,) lying below and behind the spiracle is separated only by a
weak line from the proepimerum, but for reasons to be given later it is regarded
as belonging to the mesopleurum.

The prosternum consists of a transverse plate lying in front of the bases of the
cox, connected laterally with the episterna, and having a median posterior in-
tercoxal extension fused with the anterior sternal part of the mesothorax.

The cervicum or “ microthorax” is represented by the two lateral cervical
plates (mi) already mentioned. The two are connected with each other ven-
trally by uniting transverse arms.

The Mesothorax.—This segment, in the mosquito, forms the great bulk of the
entire thoracic mass. The anterior end of its tergum projects over the top of the
head and the posterior end is separated from the abdomen only by the narrow
metatergal bridge (7',). As in nearly all insects the mesotergum consists of
two principal plates, a large anterior one (psc, sct,, and scl.) constituting the
true notum and carrying the wings, and of a smaller posterior postnotal plate
(PN,) lying between the first and the metatergum and connected laterally with
the epimera of the mesopleura. The first plate is indistinctly divided into a
prescutum (psc,), a scutum (sct,) and a scutellum (scl,). The second plate
constitutes the postnotum, usually termed postscutellum in the higher orders.
On account of the posterior location of the wings and the narrowness of their
58 MOSQUITOES OF NORTH AMERICA

bases, both of the notal wing processes, 7. ¢., the lateral lobes of the notum to
which the wings are articulated, arise near the posterior end of this plate. The
first belongs to the scutum, the second to the scutellum. The scutum bears also
asmall lateral lobe (w) between the front spiracle and the base of the wing. The
axillary cords (AxC), which form the corrugated cord-like thickenings of the
posterior margins of the basal or axillary membranes of the wings, arise from the
posterior margin of the scutellum. They thus mark the posterior limit of the
true notum as distinguished from the postnotum, though the two plates are
separated from each other by a membranous suture.

The mesopleurum is triangular, its corners being marked by the anterior
spiracle (1Sp), the base of the wing (W.,) and the base of the middle coxa
(Cz,). Its two main plates, the episternum (#ps,) and the epimerum (Hpm,)
are separated by the pleural suture (PS,) which extends from the coxal articu-
lation into the pleural wing process (WP,). In front of the main episternal
plate (Hps,) is a smaller one (eps,) evidently derived from the first but sepa-
rated from it, except ventrally, by a wide membranous suture. Its front edge
is united along a weak suture with the prothoracic epimerum (Hpm,) and the
plate itself, therefore, may appear to be a part of the latter, though its dorsal
end projects upward behind the first spiracle. In Tipula there is no separate
sclerite corresponding with this plate, the mesoepisternum being continuous
from the pleural suture to the first spiracle. In Bibio there is a suggestion of
the separation of the anterior plate from the rest of the episternum, while in all
higher flies it forms a conspicuous sclerite on the anterior part of the side of the
thorax. Some authors have regarded it as a part of the mesosternum, but this
would involve the unseemly condition of having the sternum reaching to the
tergum in front of the episternum.

The principal episternal plates (Hps,) of the opposite sides meet on the
ventral surface and fuse with each other along the mid line. In most of the
Diptera a distinct longitudinal suture cuts off a ventral plate from the lateral
episternal plate, which is usually regarded as a mesosternal sclerite, but no such
suture is present in Psorophora.

The epimerum (Hpm,) of the mesothorax is a large plate lying behind the
pleural suture (PS,). Below itis asclerite (S,) lying posterior to the mesocoxa
(Cz,) and connected ventrally with the mesosternum. It may be regarded, in
fact, as a postcoxal wing of the sternum, though there is no positive evidence that
it does. not belong to the epimerum. Its upper end is overlapped by a small
marginal sclerite (6) on the edge of the epimerum.

The articulation of the coxa is against a small triangular plate (a) wedged in
between the episternum (Hps,) and the postcoxal sclerite (S,), beneath the
epimerum (Zpm,). The internal pleural ridge extends upward from this plate
along the line of the pleural suture (PS,) to the pleural wing process (WP,).
The latter is formed by the adjacent parts of both the episternum and the
epimerum, and is the support of the wing from below.

The mesothoracic paraptera are not as well developed in the mosquito as in
some other flies. The first is absent entirely and the second (2P,) is fused with
MODIFICATIONS OF THORAX 59

the episternum in front of the wing process. The third (3P,), lying behind
the wing process, is well developed.

The mesosternum is hard to define in the mosquito. A pentagonal sternal
plate lies between the mesocoxal cavities behind the median ventral extension
from the episterna already described. The postcoxal plates (S,) of the meso-
thorax are attached to the posterior parts of its sides, while its posterior angles
are prolonged into slender bands that extend outward and upward in front of
the metacoxze and become continuous with the lower parts (c) of the metapleura.
Hence, this plate would appear to represent both the mesosternum and the
metasternum, for otherwise there is no metasternal element.

The Metathorax.—The third segment of the thorax is difficult to describe. It
is not only reduced in size, but the typical structure is so obscured by secondary
modifications that it is impossible to say, from a morphological standpoint, what
some of the parts are. The tergum (7’,) forms a narrow dorsal bridge between
the postnotum (PN,) of the mesotergum and the first abdominal tergum (I7T’)
The upper part of the pleurum carries the halter (W,) the representative of the
hind wing. An irregular line (PS,) extends downward from the wing support
(WP,), which may be known, by the corresponding internal ridge, to be the
pleural suture, but it divides before it reaches the coxa and incloses an elongate
area (c) that carries the coxal articulation. The plate (Hps,) in front of this
suture is, of course, the episternum, while at least some part of the surface be-
hind it must be the epimerum (Hpm,). The structure of this part, however, is
so broken up by accessory sutures that the limits of this sclerite can not be posi-
tively asserted. The ventral pleural plate (c) is anomalous and may represent
the lower parts of both the episternum and the epimerum since it bears the ar-
ticulation of the metacoxa (Cz,). It is connected by a precoxal band with the
pentagonal sternal plate, as described under the mesothorax. Behind the epi-
merum (Hpm,) are two plates (PN,) reflected upon and fused with the an-
terior edge of the first abdominal tergum (IT). A study of other Diptera sug-
gests that these two plates together represent the postnotum (postscutellum) of
the metathorax, though, on the other hand, they may belong to the first abdom-
inal segment.

The second spiracle is almost surrounded by the metaepisternum, an unusual
condition, though it is generally conceded to belong to the metathorax.

To the preceding discussion of the thoracic structures by Mr. Snodgrass but
little need be added. The thorax is remarkably uniform in structure within the
Culicide and but few modifications occur that are of systematic value. In the
systematic part of this work we call the most prominent parts of the prothorax,
considered by Snodgrass as probably tergal, the prothoracic lobes. These lobes
show considerable diversity in different genera. In most of the Culicini the pro-
thoracic lobes are small and lateral. In the genus Stegoconops, however, they
are large and very prominent, and nearly contiguous upon the dorsum. In the
Sabethini a few genera have the lateral lobes well separated but rather promi-
nent laterally (Joblotia, Lesticocampa, Prosopolepis). In most sabethids,
however, the prothoracic lobes are large and prominent, contiguous or nearly so,
60 MOSQUITOES OF NORTH AMERICA

and form a kind of projecting collar under which the head is inserted. The
prothoracic lobes bear coarse bristles which are usually irregularly scattered over
the surface; where the lobes are collar-like, as in Sabethes, the bristles are in-
serted along the anterior edge.

The scutellum is usually sinuaté in outline posteriorly ; there is a large median
lobe and a smaller lobe on each side. Each lobe bears a group of coarse seta.
Theobald has described a curious mosquito (Rachionotomyia ceylonensis) from
Ceylon which is characterized by the “scutellum drawn out into a large, thick,
backwardly projecting spine, hiding to a large extent the metanotum.” In
Anopheles and a few other forms the scutellum is feebly arcuate behind without
indication of lobes; there are, however, forms with feebly differentiated lobes
which form the transition to the distinctly trilobate ones.

The region of the mesotergum lying in front of the scutellum is called meso-
notum in descriptive work and for convenience we have retained this term. It
offers no modifications in structure of a tangible character. It bears coarse sete,
variously disposed, and their arrangement and abundance are of some signifi-
cance. There are always coarse sete: along the anterior and lateral margins and
these are particularly coarse and abundant over the roots of the wings. In the
Sabethini, and also in Megarhinus, the disk is devoid of sete. In most of the
Culicini there are numerous bristles upon the disk arranged more or less in longi-
tudinal series. There is a double series along the median line which does not,
however, reach the posterior margin. Two other rows of sete form sublateral
longitudinal series.

The part of the mesotergum behind the scutellum is called metanotum in most
descriptive work. This term implies that the structure belongs to the metathorax
whereas in reality it is mesothoracic. We have, therefore, in the systematic part
of the present work, adopted the term postnotum. The postnotum shows no
variations in structure of a tangible sort. Usually it is nude and smooth or
pruinose. It may be indistinctly keeled. In the Sabethini there is a group of
setee, medianly near the posterior margin. In the genus Dinomimetes of the
Culicini one or two coarse, spine-like bristles are present in the same situation ;
these arise from a common base, while in the Sabethini the sete are inserted
separately.

THE WINGS.

The wings are Jong and narrow. The venation is the same throughout the
family Culicide: and shows only variation in minor details. In the nomenclature
of the veins we follow Williston. The costal vein encompasses the wing and is
strongest along the anterior margin. The auxiliary vein encloses a narrow area,
the costal cell, along the anterior margin and terminates in the costa about two-
thirds the length of the wing from the base. Following this are six principal
veins of which the second, fourth and fifth are forked. The first vein is sepa-
rated from the auxiliary vein and the costa by a narrow cell, the subcostal cell,
and joins the margin near the apex of the wing. The second vein originates
from the first vein behind the middle of the wing. The third vein springs from
the second beyond the middle of the wing and is angulate at its base; the small
THE WINGS 6]

transverse portion has been frequently called the “ supernumerary cross-vein.”
The fourth, fifth and sixth veins arise at the base of the wing. A small cross
vein, which joins the basal part of the third vein with the fourth vein, is
called the anterior cross-vein. Another cross-vein joins the fourth vein anc
the upper branch of the fifth vein and is called the posterior cross-vein. The

osterior cross-vein is usually a short distance behind the anterior cross-vein, it
hay, however, be in line with it or even beyond it. There is also a humeral
cross-vein, close to the base of the wing between the costa and the auxiliary vein.
Between the first and auxiliary veins and behind the origin of the second vein
is the subcostal cross-vein. Besides these veins there are chitinizations resem-
bling veins and sometimes in continuation of them. These ‘are variously de-
veloped in the different forms. The second and third veins are usually thus con-
tinued longitudinally backward from the point of angulation. A particularly
heavy chitinization follows the fifth vein on the anal side, and in Megarhinus,

 

 

 

 

 

 

 

 

   

costal cell ‘ etiole oy 29 marginal cell
h \ i t auxiliary vein Ps :
MIE AS eal vein ay ! ~sebmarginakeelt:
= i‘. L is 4 ——— —
Ss) 8 we
—— = ae marge: cel ; = 1

; - and Marginal) cell 2

Sub . pee
——S¥bmarginal cell a
3

   

Fig. 3.—Venation of wing of Culea.

where the chitinizations are particularly marked, there is also a chitinization in
front of the lower branch of this vein. In some forms there is a chitinization,
usually poorly defined, which traverses the hindmost area of the wing (the
axillary cell) longitudinally and forms a more or less well-marked fold. In
Megarhinus it is particularly distinct. In the case of certain African mosqui-
toes this fold bears a few scales. It has been incorrectly looked upon by Theobald
as a seventh vein and upon this character he founded a subfamily, the Hepta-
phlebomyine.

The relative length of the fork and the stem, particularly in the second vein,
is in some cases of diagnostic value, not only specifically but generically. Thus
the genera Megarhinus and Uranotenia are remarkable for the very short
branches of the second vein. The part of the wing enclosed by the two branches
of the second vein is the second marginal cell; it is often incorrectly called the
first submarginal cell. The position of the posterior cross-vein in relation to
the anterior cross-vein is also of significance in classificaton, although there is
naturally some individual variation.

The wings are clothed with scales along the veins and along their margins.
These scales show great diversity in shape and characters in different species and
62 MOSQUITOES OF NORTH AMERICA

on different parts of the wing; they offer excellent characters for specific dif-
ferentiation. Also the scales of the wing may be of different colors, either
irregularly distributed or forming a definite pattern, as in many species of
Anopheles. The vestiture is heaviest in the costal region, and the several series
are often crowded and overlapping; sometimes there is a series of coarse scales
which project spine-like from the costal margin. The wing-membrane is usually
clear and transparent; sometimes, however, it is infuscated, particularly along
the costa. Such infuscation is usually diffused over the entire wing. Sometimes
the infuscation occurs in diffused spots in the region of the cross-veins, and else-
where, as in certain species of Culiseta.

The shape of the wing often differs in the two sexes and the wing of the male
is then smaller and narrower. The narrowing of the wing of the male is often
very marked and is accompanied by differences in the proportions of the veins ;
particularly is there a tendency to crowding towards the costa and to the re-
duction of the second marginal and second posterior cells. When the male has
much narrowed wings the scales are often very deciduous.

THE LEGS.

The legs are long and slender. They are composed of trochanter, femur,
tibia, and a tarsus of five joints. The trochanters are short, jointed with the
cox above, and with the femora below. They are freely movable upon the coxa
but they are rather closely united with the femur and there appears to be but
little motility at that point.

The femora are always long but show considerable variation in the different
forms. Usually they are nearly alike in all three pairs of legs and are sub-
cylindrical or compressed. In Anopheles they are very long and slender and of
nearly equal thickness throughout. In Psorophora ciliata the femora are some-
what thickened towards their apices. In many forms the femora are compressed
and more or less enlarged. This enlargement is usually most pronounced in the
front and middle pairs; the middle femora, furthermore, are often fusiform,
largest above the middle. In some Sabethids the front femora only are
thickened. All three pairs of femora are usually of very nearly equal length.
In most forms the middle femora are slightly longer than the other two pairs.
In the Sabethini the hind femora are the shortest, in many forms appreciably
so, and this characteristic is usually more marked in one sex or the other. In
Sabethes the middle femora are much the longest. The femora are armed with
a group of spines at their apices which differ in character and arrangement in
the different genera. There are also longitudinal series of sete, varying in num-
ber and coarseness. In Megarhinus these sete are represented by spines.

The tibie are slender and of approximately the same length as the femora.
They are subcylindrical and slightly thickened apically. This thickening is
most marked in the hind tibie. In the Culicini the three pairs of tibiee may be
subequal in length, or the front pair may be markedly shorter. In the Sabethini
the hind pair of tibiee are always the shortest, although this character varies in
degree with the species and the sex; they are also stouter and more incrassate.
TARSAL STRUCTURES 63

The front tibie are often the longest in the Sabethini. At their apices the tibiee
are more or less excavate behind and bear several stout spines, and in addition,
particularly on the front and hind pair, numerous stiff sete. Upon the front
and hind tibiz these sete are densely massed upon the broader portions of the
tibize and in addition there is, subapically on the inner side, a transverse row of
very densely placed sete. Below this row of sete are usually present several
slender spines, also in a transverse row. These spines have been termed the
tibial scraper and their presence or absence, on the hind tibie, and their number,
are of systematic value. The tibiz also bear longitudinal series of spines and
these differ in character with the species.

The tarsi are slender, cylindrical and differ considerably in their proportions
on the three pairs of legs. They are, as a whole, much longer on the hind legs
and it is they largely that determine the predominating length of this pair of
legs. The first tarsal joint is always very long in all three pairs of legs, although
usually somewhat shorter than the tibia. In Anopheles, however, the first tarsal
joint of the hind legs is longer than the tibia. The first tarsal joint is by many
systematists called the “ metatarsus.” The application of this term is incorrect
as it implies something beyond, or outward, from the tarsus. As the first tarsals
differ from the following ones only in length, and this is not true of all Diptera,
there is no reason why they should be designated by a special term. Further-
more the introduction of this term has brought about much confusion in de-
scriptive work; when an author has been inconsistent in this usage it is some-
times impossible to determine if his “first joint” is in reality the first or the
second.

Each tarsal joint is shorter than the one preceding it; the only interruption
occurs, sometimes, in the last two tarsals of the front and middle legs, the fourth
joint being in such case the shorter. This progressive reduction is most rapid
on the front and middle legs, the hind tarsi are always much the longest. In
many forms the front tarsi are, as a whole, noticeably shorter than the middle
ones, while still more often they are nearly equal. In some Sabethini the middle
tarsi are shorter than the anterior ones.

The fourth tarsal joint, as already indicated, is often shorter than the fifth,
either upon both the front and middle legs or upon the front legs alone. This
difference is greatest in those males in which the claws show the most sexual
modification. In the female the fourth joint, if shorter than the fifth, is usually
but slightly so; in Bancroftia, however, the fourth joint is very short, about as
long as broad. In the females of Anopheles and in both sexes of most Sabethini
the last tarsal joint is distinctly the shortest. All the tarsal joints but the last
bear a pair of spurs apically beneath. In addition there are longitudinal series
of spines or sete; these, and the terminal spurs, are variously developed in the
different genera and species. The last tarsal joint bears the two claws, or, in a
few cases, a single claw. In the females, and in many males, the fifth tarsal
joint is cylindrical, resembling in character the other joints. It is often ob-
liquely excised at the tip beneath for the insertion of the claws and their mechan-
ism. In the males of most Culicini, and in the male of Joblotia, the fifth tarsal
64 MOSQUITOES OF NORTH AMERICA

jotniof the front and middle legs, or of the front legs alone, differs considerably
from the others. In these cases it is considerably longer than the fourth joint
and is more or less deeply concave along nearly its entire under side. It is
broadest at the base which is often produced beneath into a tooth. Sometimes
there is a spinose process near the middle of the concavity. The fifth joint
usually bears many sets towards the apex, particularly when modified as just
described. In the case of such modification it also generally bears a series of
spines basally beneath. When the fifth tarsal of both the front and middle legs
is modified as just described the development is greater on the front legs, in-
deed, forms occur in which the concavity is but slightly indicated on the middle
legs.

“The claws are inserted at the apex of the last tarsal joint. There are nearly
always two claws but in a few cases (Limatus, Lesticocampa) there is but a
single claw on the hind legs. They are curved and taper to a point. When with-
out teeth the claws are said to be simple. When the two claws of the same foot
are of the same length they are said to be equal. In the females each pair of
claws is equal or nearly so, but they differ much in size in the different genera.
The claws of the hind leg are often much smaller than the others. In the female
the claws are most often simple. In the females of many species of Psorophora
and Aédes, and of some Stegoconops, at least the claws of the front and middle
legs bear a distinct tooth before the middle. In certain species of these genera
the hind claws also are toothed. This, however, appears to be a variable char-
acter in some species. In Aédes sylvestris the hind claws of the female may be
simple or toothed. Indeed we have a specimen of this species in which three
of the claws of the hind legs are simple while the remaining one is toothed; in
another specimen three claws of the hind legs are toothed and one is simple.

In the males the claws of some of the legs are usually modified in a striking
manner. In the Culicini it is generally the claws of the front legs that show
sexual peculiarities, and often also the claws of the middle legs. There is often
considerable diversity in this respect among the members of a single genus. In
Culex pipiens, and in many other species of Culex, the inner claw of the front
and middle legs is much larger than its mate and bears a long tooth outwardly
near the middle; the other claw bears a tooth on the opposite side near the base.
The position of the teeth on the claws differs in some of the species; the tooth on
the large claw may be nearer the base and the tooth on the small claw moved
farther out. In certain species the tooth of the small claw is much reduced and
in others it is absent. In Culex latisquama only the large claw of the front legs
is toothed ; the claws of the middle legs are simple, but unequal in shape and
length. It may be remarked that in correlation with these simple claws of this
species are the longer fourth tarsal joints of the front and middle legs. There is
great diversity in the claws of the males of the different species of Aédes and
Psorophora. In Psorophora, irrespective of the claw structure of the female,
the male has the large claw of the front and middle legs armed with two teeth,
one near the middle, the other basal, while the smaller claw bears a single tooth.
In those forms of this genus in which the claws of the female are toothed the
MODIFICATIONS OF CLAWS 65

hind claws of the male are also toothed. In the main group of Aédes, in
which the claws of the female are toothed, there is much diversity in the front
and middle claws of the male. Thus in Aédes curriei and other forms the large
claw of the front feet bears two teeth, the smaller claw one, while on the middle
legs both claws bear a single tooth. In Aédes sylvestris both claws of the front
feet bear a single tooth, while on the middle feet the large claw only is toothed.
In Aédes fuscus only the large claw of the front and middle legs bears a tooth.
In all the forms in which the hind claws of the female are toothed these are also
toothed in the male, and, as in the female, of equal length. In Aédes calopus
the female has toothed claws on the front and middle legs ; the male has a tooth
on the large claw of the front feet only, the claws of the middle feet are simple
but unequal. In the males of other forms of Aédes in which the claws of the
female are simple, as Aédes fulvithorax, the large claw of the front and middle
legs is toothed, the smaller one simple. The same is true of Mansonia per-
turbans and other species of that genus. In Bancroftia the large claw of the
front and middle legs of the male bears a single slender tooth near the middle,
while the smaller tooth is simple. In the male of Megarhinus the larger claw
of the front and middle feet bears a sharp tooth. In the male of Stegoconops
capricorni both claws of the front feet bear a small tooth near the base; on the
middle feet the large claw is simple, while the small one carries a tooth. The
female of this species has toothed claws. Stegoconops albomaculatus, in which
the claws of the female are simple, has the larger claw of the front and middle
feet of the male armed with a single tooth while the smaller claw is simple. In
Culiseta, where again the female claws are unarmed, the male has the claws of
the front and middle legs toothed, the larger claw bearing two teeth, the smaller
a single one.

In the genus Deinocerites the tendency in the male claws is towards sim-.
plicity. In Deinocerites cancer and D. melanophylum the claws of the front and
middle legs are unequal in the male, the larger claw toothed, the smaller simple.
In Deinocerites troglodytus the claws of the front and middle feet of the male
are large but equal; both claws are toothed on the front feet, on the middle feet
only one of them. In Deinocerites pseudes, finally, all the claws of the male are
simple and equal; those of the front feet, however, are very large and sickle-
shaped. In the male of Uranotenia all the claws are simple; those of the front
legs are equal; the middle feet, however, have a single, large, strongly hooked
claw which is inserted beneath, behind the apex of the tarsus.

In Anopheles the claws of the,front feet only are modified in the male. There
is one large claw with a tooth at the middle and another laterally at the base.
The second claw is rudimentary and, with the empodium, inserted some distance
behind the large claw. Theobald figures the large claw of Anopheles grabhamit
without basal tooth; there is, however, a well-developed basal tooth in this, as
in all the other species of Anopheles we have examined. In the closely related
Celodiazesis barberi the small claw, together with the empodium, is placed well
forward near the large claw; it is, however, very small and strongly curved. The
large claw has an additional smaller basal tooth on the side opposite the other

one.
66 MOSQUITOES OF NORTH AMERICA

In the males of the Sabethini it is usually the claws of the middle feet alone
that show sexual peculiarities, and even these may be but slight. With a very
few exceptions the claws are simple in both sexes and the male characters consist
of differences in the length and shape of the claws. In Wyeomyia trinidadensis
the claws of the middle feet of the male are nearly equal in length; one of them,
however, is much stouter and more strongly curved, and the fifth tarsal joint is
deeply excised apically beneath. In Limatus durhamii the claws of the male’s
middle feet are similar to those just described, the last tasal joint, however, is
without excision and only slightly tapered towards the apex. In the male
Wyeomyia circumcincta the claws of the middle feet are unequal in length, the
large one sickle-shaped, the small one gently curved. In the male of Wyeomyia
smithii there is one large sickle-shaped claw and the small claw is represented by
a minute stout spine. In Sabethinus undosus the male has the claws of the
middle feet of nearly equal length ; however, one claw is deeply cleft and one of
its branches, instead of tapering to a point, is flattened and truncated at the tip,
the truncation bearing a series of very fine teeth. The claws of the middle feet
of the male Sabethes cyaneus are very similar to those just described; the
flattened branch, however, is much broader and covers the other, the point of
which projects slightly from below.

In the Sabethini just discussed it is only the middle claws of the male that are
modified ; the front claws are simple and equal. In the genera Joblotia and
Lesticocampa both the front and the middle claws are differentiated. In Job-
lotia digitatus the claws of the front and middle legs of the male are unequal but
simple, those of the front legs being the larger and more curved. In the male of
Lesticocampa lampropus the claws of the front and middle legs are unequal and
simple, bent strongly backward so that the tip of the large claw nearly touches
the fourth tarsal joint.

In Joblotia trichorryes the claws of the front and middle legs of the male are
unequal ; the large claw of the front feet has a slender tooth while all the other
claws are simple. The claws of the male Lesticocampa dicellaphora are perhaps
the most remarkable of any mosquito. The front claws are unequal, the larger
with a tooth. The middle claws are also unequal; the smaller is slender and
unarmed ; the larger has along its under surface a comb, composed of about
twenty very long, slender, sharp teeth.

The claws are supported by a membranous cushion which occupies the apical
portion of the last tarsal segment beneath. This cushion may be nearly obsolete,
as in the male of Uranotenia, when the claws are inserted close upon the tarsus
and more or less ventrally. The cushion covers the ventro-apical excision of the
fifth tarsal joint and upon the size of this excision the development of the cushion
depends. On this account this cushion is well developed in most of the Culicini
and produced forward beyond the tarsus to support the bases of the claws. The
cushion is furnished with two, more or less lanceolate, chitinous pieces, the
flexor plates. These flexor plates have muscles attached to their bases and hinge
upon the tarsus ; apically they are attached to the bases of the claws. By traction
of the muscles the claws are drawn downward. When the cushion is well de-
ABDOMEN OF FEMALE 67

veloped it is hairy and particularly on the apical half the hairs are long and
stiff. The pulvilli, a pair of fleshy lobes present on the feet of the higher flies,
are absent in the Culicids, as in most other Nemocera. Ficalbi wrongly showed
pulvilli in the foot of the mosquito and has been followed in this by Blanchard
and others. The error is based upon a misinterpretation of the cushion just
described.

The empodium is an unpaired organ arising between the claws. It is usually
slender and tapers outwardly into a bristle and bears a number of sete. It
differs much in length and development and may even be absent altogether. It
is, however, well developed and long in the front feet of the male Anopheles,
where one claw is rudimentary ; but in this case it is inserted at a considerable
distance behind the large claw. In Lutzia bigotti it is broadly compressed, with
a setose margin; at the base of the claws, externally are a series of long sete,
the whole forming a mechanism to enable this large mosquito to rest upon the
water. In Culex melanurus the empodium has the form of a chitinous plate
the outer margin of which is produced into a series of long spines.

THE ABDOMEN.

The abdomen is elongate, more or less cylindrical, and is composed of ten
segments. Of these the first eight are similar in character while the last two are
greatly reduced and modified for the sexual functions. Each of the first eight
segments consists of chitinized dorsal and ventral plates, the tergum and
sternum ; these are connected at the sides by a broad area of flexible membrane
which is folded when the abdomen is not distended. The segments are con-
nected with each other by flexible membrane which is normally retracted in such
a manner that each segment projects over the succeeding one. There are six
pairs of abdominal spiracles. These are small and situated before the middle
in the pleural membrane of the second to seventh segments. The first segment
is shorter than the succeeding ones and its tergite bears many long hairs upon
its surface.

THE ABDOMEN OF THE FEMALE,

The oviduct opens in the membrane behind the eighth sternite; the orifice is
large and is surrounded by chitinous strips. The ninth segment is small and
bears a small chitinous tergite while the sternite is carried outward and pro-
jects beyond the tenth segment. The ninth sternite bears a pair of gonapophyses
which are variously developed. They may be nearly obsolete, represented by a
pair of blunt tubercles; in other forms they are long and slender and bear many
coarse hairs. The tenth segment is greatly reduced, without tergite or sternite ;
it bears the cerci and in it is the anal opening. The cerci are not jointed, but
present great variation in form and size. There is often present a third chitinous
appendage which apparently also belongs to the tenth segment ; in certain forms
this is large and of nearly equal length with the cerci and may be emarginate at
the apex. The general form of the abdomen of the female differs greatly, and
correlated with this difference is the form of the terminal appendages. To a

6
68 MOSQUITOES OF NORTH AMERICA

certain extent at least these modifications are correlated to the mode of ovi-
position. Thus in Culex, Culiseta, Mansonia and Uranotenia, which lay their
eggs in a raft, the tip of the abdomen is blunt and the cerci are small and broad
and not promiment. In Psorophora, and most species of Aédes, which deposit
their eggs singly, the abdomen tapers towards the tip and the cerci are long,
slender and exserted.

In Psorophora the eighth segment is flexible and completely retractile within
the seventh. Basally on the eighth segment there is a broad area of membranous
tissue ; outwardly are the tergum and sternum and these are also membranous
in character but differentiated in structure by the presence of numerous minute
transverse strips of chitin. Internally the two plates are supported by two pairs
of slender chitinous rods and these probably also form part of the mechanism
for retracting the segment. The sternite is broadened posteriorly and projects
considerably beyond the tergite, thus forming a ventral support for the greatly
reduced ninth segment. The eighth segment when fully protruded is longer
than the preceding one. In most species of Aédes the eighth segment is partly
retractile, having a broad basal membrane, but this is not as extensive as in the
forms just described. The tergal and sternal plates are, however, in Aédes,
continuously chitinized and clothed with hairs and scales.

In the females of Deinocerites and Dinomimetes the abdomen is long, some-
what compressed, and slightly tapered towards the tip; the eighth segment is
peculiarly modified. The tergite of the eighth segment presents nothing un-
usual but the sternite is larger, compressed, and produced posteriorly, the apical
portion heavily chitinized. In Dinomimetes epitedeus and Deinocerites pseudes
the sternite is much produced in the form of two rounded lateral lobes, their
upper portions most prominent ; the margins of the lobes are closely beset with
coarse sete inserted in tubercles. In Deinocerites cancer and related forms the
lobes of the eighth sternite are roughly quadrate and very heavily chitinized,
with the lower angle somewhat produced ; upon this angle and along the lower
margin are a series of tubercles bearing coarse sete which give the margin a
serrate effect. In this last-described type of Deinocerites the cerci reach an un-
usual development. They are large, conical, heavily chitinized, and have in-
serted at their apices a pair of long, slender flattened appendages. The gona-
pophyses are inconspicuous in these forms. The shape of the sternal lobes and
of the cerci differs in the different species. In Deinocerites pseudes and Dino-
mimetes epitedeus the cerci are, as in other mosquitoes, without terminal ap-
pendages ; they are, however, rather large, leaf-like and heavily chitinized. In
these two species the gonapophyses are well developed, heavily chitinized and
setose.

The eighth abdominal segment of the female Mansonia titillans is remarkable
in that it is completely retractile within the seventh while its tergite is mem-
branous and bears at its apical margin a row of stout chitinous hooks. In many
forms the abdomen is more or less depressed, particularly towards the base. In
Carrollia and in Wyeomyia codiocampa the abdomen is strongly compressed.
In the Sabethini the abdomen is usually subcylindrical and blunt at the tip, and
MALE GENITALIA 69

sometimes it is very elongate. The surface of the tergites and sternites bears
many scattered hairs and these vary in coarseness and abundance with the
species ; there is a series of coarser and longer hairs along their posterior margins.
These marginal hairs, and still more so the others, are much less conspicuous in
the Sabethini; in this tribe, however, the eighth segment bears numerous stiff
bristles posteriorly, particularly beneath.

THE ABDOMEN OF THE MALE.

The abdomen of the male is often much longer than that of the female. The
ninth and tenth segments are crowded together and carry the genital armature.
Often the abdomen is depressed and of nearly uniform width throughout. The
tergite of the first segment, as in the female, bears many long hairs. The abdo-

 

Fig. 4.—Diagram of the male genitalia of Aédes: A, Side
piece; B, Clasp filament; 0, Lobes of side piece; D, Harpe;
#, Harbago; F, Unci.

men is often strongly ciliate along the sides, numerous long hairs being inserted
laterally on the tergites. This is true of Anopheles, Megarhinus and most
species of Culex and Aédes as well as of many others. In other forms there is no
obvious lateral ciliation but there is a tendency to increased coarseness of all
the sete towards the tip of the abdomen. Sometimes the eighth segment is
armed with many coarse setew. Usually the sete of the sternites are coarser in
the male than in the female. In the Culicini there is a reduction in the size of
the segments near the tip of the abdomen. In many Sabethini the abdomen is
distinctly expanded towards the tip, and the sternite of the eighth segment par-
ticularly, bears many coarse bristles. The male genitalia are very important
in classification and for systematic purposes may be described as follows:

The Male Genitalia (fig. 4)—The male genitalia consist of two thick
conical appendages, the side-pieces (a). These each bear a smaller terminal
70 MOSQUITOES OF NORTH AMERICA

appendage, the clasp-filament (b) and also occasionally certain lobes near base
or tip (c), designated as subapical or subbasal lobes. There are three sets of
paired basal appendages, the harpes (d), harpagones (e) and unci (f). The
penultimate segment generally has a pair of setose appendages, the basal ap-
pendages (g). In the simplest forms these smaller basal appendages, harpes
and harpagones are absent, as in Anopheles, though the unci are always present.
In the succeeding higher forms the harpes appear and still later the harpagones.
The harpes are present in all the genera above Anopheles, Aédeomyia and
Uranotenia and are probably homologous throughout the group as they have
essentially the same form in all, only becoming modified in Culex. The harpa-
gones, or at least a third pair of appendages, appear in all the highest forms, but
it is doubtful if they can be regarded as strictly homologous as they seem to have
arisen three times independently, once in Aédes, once in Culex and once in
the sabethid line. We have, however, uniformly designated the third pair of ap-
pendages as harpagones. Several different lines of modifications are found in the
different groups. The Anopheles are all very simple, having besides the side-
pieces, clasp-filament and unci, nothing but various spines and hooks without
forming definite accessory clasping organs. In the most specialized species,
such as bellator and barberi there is a rounded basal lobe bearing a tuft of long
hairs. Next to Anopheles in simplicity comes Aédeomyia, in which there are
present only somewhat complex unci. The side-pieces have a small basal lobe
while the clasp-filament has a multiple terminal spine. Next comes Uranotenia,
in which there is a complex series of small basal appendages perhaps represent-
ing divisions of the unci, but no recognizable harpes. The side-pieces bear a
more or less well-developed conical basal lobe. Next come the lower Sabethids,
Lesticocampa and Joblotia, together with the lower Culicids, Megarhinus, Ban-
croftia, Mansonia and Culiseta. These have the harpes well developed but no
harpagones. There is generally present a basal lobe to the side-piece, which in
Mansonia becomes modified into a ribbon-like appendage or a rod carried on the
basal lobe. In the Sabethid line a division of the small basal parts occurs, so
that in many forms a third pair of appendages or harpagones can be recognized.
The characteristic development of the line, however, takes another direction,
that of the modification of the clasp-filament, which becomes lobed and dis-
torted, culminating in Sabethes, where a truly wonderful structure is produced.
In a few forms the clasp-filament is reduced to a rudiment, its place being taken
functionally by an expanded outer angle of the side-piece, and in others a basal
lobe of the side-piece is developed (as in Wyeomyia eloisa and allies) in which
case the clasp-filament is more or less reduced. In the Aédes line the lower
forms are simple. In calopus there are no harpagones and in other tree-hole
species the first rudiments of these organs are seen as a conical basal lobe of the
side-piece bearing a seta (for instance in walkeri, albonatata, etc.). Later this
becomes developed into a rod bearing a filament. Sylvestris and fuscus have no
harpagones, but in these cases the organs have not improbably retrograded. In
the Janthinosoma group the rod bears several filaments and in Psorophora a
capitate tip is developed with a large group of filaments. The harpagones of
VESTITURE val

Aédes are derived from basal lobes of the side-pieces, but have reached a dif-
ferentiation of structure such that we consider them as separate organs, while we
do not so consider the similarly derived structures of Mansonia. In the Culex
line we find two simple forms, dyari and melanurus. In these the side-pieces
are simple with basal lobes only. The unci and harpes are normal while the
harpagones are undeveloped or indicated by a division at the base of the harpes.
This is essentially the structure of Culiseta, etc. But in this line the harpagones
arise as division from the base of the harpes and not as basal lobes of the side-
piece. In Culex proper and its derivatives Carrollia and Lutzia both harpes and
harpagones are progressively notched and divided into lamelle, the harpes
evolving a curved basal branch and the harpagones becoming divided. The unci
are not recognizable in these highly developed forms. The side-pieces of Culex
generally bear a lobe near the middle which carries set or filaments and gen-
erally a leaf-like appendage. The Deinocerites group is apparently a develop-
ment from Culex in which one of the lobes of the harpagones has grown out into
a long spatulate process. The clasp-filaments are thickened and hirsute, some-
what as in some Culex, and there are a number of smaller modifications render-
ing the type distinct in appearance in this line.

THE SCALES.

It has already been stated that the wings bear scales along the veins and on
the margins. The body and the legs, proboscis and palpi of mosquitoes are
always more or less scaled. Scales are modified hairs. Among the least special-
ized mosquitoes, the Anopheles, we find in the body vestiture of the different
species an imperceptible transition from hairs, through “ hair-like ” scales, to
well-differentiated scales. The scales differ greatly in form and size on different
parts of the body. They also show important specific differences and may even
present peculiar characteristics within a certain group. The color of the scales
in great measure gives the different species their characteristic appearance and
upon vestiture-coloration specific identification largely depends. There is great
range in the coloration of the scales. Many mosquitoes show only dull colors,
such as black, brown, and dull reddish or yellowish shades, variegated with white.
Others show a pattern of silvery or golden scales, while still others are clothed for
the most part with scales of brilliant metallic blue, green or purple.

Theobald, who has utilized to the utmost in his systematic work the character
of the scales, in Genera Insectorum, Culicide (1905), enumerates seventeen
types of scales, as follows: “1, Flat or spatulate scales; 2, Broad Mansonia
scales; 3, Broad Aédomyia scales ; 4, Curved hair-like scales; 5, Narrow-curved
scales; 6, Spindle-shaped scales; 7, Small spindle-shaped scales; 8, Inflated or
parti-colored scales ; 9, Pyriform scales; 10, Upright forked scales; 11, Twisted
upright scales ; 12, Lanceolate scales ; 13, Linear scales ; 14, Teniorhynchus-like
scales; 15, Melanoconion scales; 16, Cycloleppteron scales; 17, Heart-shaped
scales.” In addition Theobald has introduced other terms, such as “ fan-
shaped,” “ long twisted ” and “ obovate ” and he has differentiated further by the
use of adjectives so that his distinctions become highly complex and often very
72 MOSQUITOES OF NORTH AMERICA

vague. In many cases intergrades between the different types of scales occur so
that the application of the terminology becomes necessarily a matter of opinion.
In fact the differences in the conception of these terms as employed by different
authors has brought about great confusion in the systematic literature.

Part of the above terms are self explanatory, others can hardly be interpreted
without recourse to specimens. The wing-scales show the greatest diversity and
have been utilized the most and eleven of the types enumerated above, and their
modifications, are employed by Theobald as wing-characters. Along each wing-
vein there are two paired series of scales and the scales of these two series often
differ greatly in form and size. The non-biting Culicide of the group Core-
thrine show the most primitive condition of wing vestiture. In Chaoborus the
scales along the wing-veins are long and hair-like and the two series are not
differentiated. Among the biting Culicide the Anophelines show the most
generalized condition. In most species of Anopheles the scales along the veins
are narrow, lanceolate, and, while there are distinctly two series, the scales of
these series are often much alike. In other forms of Anopheles there is some
differentiation, the scales of the lower series being smaller, shorter and less
divergent. In Anopheles grabhamii the scales are much broader but of the
lanceolate character; irregularly scattered among these, and with a tendency
towards grouping, are larger and darker very broad scales, their apices broadly
rounded or subtruncate. These large, broad scales are the “ Cycloleppteron
scales ” of Theobald and are said by him to be inflated; they are, however, flat
like other scales.

The wing vestiture is remarkably diversified in Uranotenia. On nearly all
the veins one of the series consists of small, truncate scales arranged in a single
row and overlapping. On the outer part of the wing the veins also have lateral
series of large scales and these differ in shape on some of the veins. Finally on
the basal portion of the fifth vein there is, in most species, a double series of very
broad small scales of a silver-blue color. In some species the scales on certain
parts of the wing are white.

In Culiseta the wing scales are narrow and in two double series along the
veins. The lower series are of smaller shorter scales, closely applied to the veins;
the upper series consists of long and very narrow outstanding scales. A very
unusual feature occurs in certain species of this genus; the anterior cross-vein
bears scales. In most species of Culex the appearance of the wing is similar to
Culiseta. There are, however, three double series of scales outwardly on some of
the veins. The long scales are usually narrow and blunt or truncate at the tip;
these are the “ linear ” scales of Theobald, and we have termed these “ ligulate.”
In many forms the scales are broadened and rounded at their apices and there is
an increased tendency to crowding towards the apex of the wing. This con-
stitutes the so-called “ Melanoconion scales” of Theobald; however these are
not separable as a distinct type, but, through different species, intergrade with
the ordinary Culex scales, and the tendency to crowding towards the apex of the
wing is a very general one. The smaller scales when broad are often obliquely
subtruncate. In most species of Aédes the wing scales are entirely similar to the
SCALES OF THORAX 73

typical Culex. In Aédes squamiger and some other species the scales of the
upper series are broad and subtruncate and these are the “ fan-shaped ” scales
of Theobald. While in most species of Aédes the color of all the scales is dark, in
certain species there is a sprinkling of light-colored scales. This is also the case
with certain species of Psorophora, and in some species the scales are grouped
to form a definite pattern (P. discolor, P. signipennis).

In the genus Mansonia the scales of one series are more or less broadened with
a tendency to oblique truncation. This is the least marked in Mansonia fascio-
latus of any of the species we have examined and in it many of the scales are
hardly different from the “fan-shaped” ones above mentioned. These are the
so-called “'Teniorhynchus scales” of Theobald. In Mansonia titillans these
scales are differentiated most and very broad and asymmetrical and many of
them are shallowly emarginate at their apices. This constitutes the “ Mansonia
scales” of Theobald. A similar type of scales, but with more rounded apices,
occurs in Bancroftia fascipes. Hardly distinguishable in character are the wing-
scales of Aédeomyia squamipennis, designated as “ Aédeomyia scales ” by Theo-
bald; their angles are somewhat more rounded.

Along the costal margin there is often a series of scales which are combined
into groups of several in such a way that they give the effect of stout spines and
this has led to the introduction of the term “spinose.” The spinose effect is
produced by the crowding together of the pointed apices of several scales. Fre-
quently this spinose arrangement is hidden by overlapping broader scales.

The head behind the eyes is covered with scales. The covering may be en-
tirely of broad scales lying flat, as in Megarhinus, or there may be several types
of scales present. Very often there is an area of greater or less extent on the
vertex covered with “ narrow, curved scales.” In addition there is frequently
a mass of “upright forked scales” upon the vertex. These are narrow scales
with a long slender stem and expanded fan-like apically; the apical margin is
roughly spinose, or it may be emarginate or tridentate. Transition forms may
occur between these and the other scales. Usually these “upright forked
scales” are in a dense mass on the vertex. In Joblotia and Lesticocampa they
are arranged in a long, regular, transverse row on the occiput. When the pro-
thoracic lobes are large the upright forked scales are absent.

The thorax is more or less clothed with scales. This scale covering is least
developed in the lowest forms, the Anophelines. In these there is but a sparse
vestiture of hair-like scales upon the mesonotum, so that the integument itself
remains plainly visible. When the scale-covering is sparse the integument
usually shows peculiarities of coloration and it may be ornamented with spots, as
in many Anopheles and Aédes fulvus. The prothoracic lobes are usually more
or less scaled. There may be but a few loose scales or the lobes may be densely
covered with them. This latter condition is particularly true of the Sabethini
and other forms with large prothoracic lobes and the coloration of this vestiture
is often important for specific determination. The mesonotum is usually for
the most part densely covered with scales. In many forms a median depression
in front of the scutellum, the ante-scutellar space, is devoid of scales. The
44. MOSQUITOES OF NORTH AMERICA

scales of the mesonotum vary much in size and shape. They are sometimes very
small and hair-like, or they may be larger and slightly broader and are then the
“ narrow curved ” scales of Theobald. They may be broad, more or less trun-
cate at the apex and are then Theobald’s “ flat or spatulate ” scales. There may
be broad, flat scales pointed at both ends and these are the “spindle-shaped
scales” of Theobald. The scales of the mesonotum may be all of one type or
several kinds may be present. The scales may be diffierent in color as well as
form and thus produce more or less distinct patterns. A curious type of scales
is present on the mesonotum of certain species of Bancroftia. These are white,
very long, narrow, flat scales arranged in longitudinal rows; some of these rows
are continued over the scutellum, the end scales projecting far beyond its pos-
terior margin. The scutellum is covered with scales of similar character with
those of the mesonotum. The scales on the scutellum may be broad while those
on the mesonotum are narrow. In many species there are areas or longitudinal
stripes upon the mesonotum which are devoid of scales.

The postnotum is usually naked ; in a few Sabethini, however, scales are pres-
ent. There may be only a few scales arranged in one or more rows, or the entire
postnotum may be covered, as in some species of Sabethes and Sabethinus.

The pleure and coxe are generally more or less covered with pale scales, but
these are often very deciduous or they may be absent altogether. Sometimes a
part of the scales on the pleure are of another color.

The abdomen is usually covered with broad overlapping scales. In many
Anopheles there is only a sprinkling of hair-like scales ; in others flat scales are
present on the last segment, or on all the segments. In certain species of Anoph-
eles, and in some other mosquitoes, there are tufts of erect, flat scales on some
of the abdominal segments. In certain species of Megarhinus there are long
scales which extend laterally as fan-shaped tufts on the apical portion of the
abdomen. In a few cases the cerci are covered with scales.

The legs are covered with scales in all mosquitoes and usually these scales
are small and closely applied to the surface. Sometimes the scales are long and
more or less raised, usually most pronounced on the hind legs, as in certain
species of Psorophora and Lesticocampa. In some cases very long, narrow scales,
which extend outward in a plane, are present on certain parts of the legs. These
in Sabethes give the well-known “ paddle” effect. These paddles involve parts
of the tibia and the tarsus. Such paddles may be present on one pair of legs or
on all the legs. In Aédeomyia squamipennis the femora are furnished with
rough scale-tufts nears their apices.

The proboscis and palpi are clothed with scales. These are usually small and
closely applied, but sometimes they are more or less raised and long and give a
shagey effect.

In a few cases scales are present upon the clypeus. The tori or globose basal
joints of the antenne often bear scales. The first joint of the shaft is densely
scaled in Megarhinus and in other mosquitoes still other antennal joints bear
scales, but these forms are exceptional.
THE INTERNAL ANATOMY OF MOSQUITOES.

Early investigators already did considerable work on the internal anatomy of
mosquitoes and since the discovery of their relation to disease there has been
much activity along this line. Already in 1851 Dufour, in his monumental
work on the anatomy of the Diptera, gave a very clear description of the digestive
and reproductive systems of mosquitoes, based largely on dissections of Culiseta
annulatus. In a work like the present which attempts to cover the greater part
of the field of our knowledge of mosquitoes, this important subject should not
be omitted, but time has not permitted us to make original studies of the internal
anatomy which has seemed to us to demand less attention than the other aspects.
Several papers bearing upon this subject might be mentioned, especially the
studies of Pressat and of Nuttall and Shipley, the careful paper on the ali-
mentary canal of the mosquito by Millet P. Thompson, and others. In order
that this work shall not be published without some consideration of this topic,
the authors have asked the permission of Dr. J. W. W. Stephens, of the Liverpool
School of Tropical Medicine, to use the chapter on this subject from the excellent
work entitled “ The Practical Study of Malaria and Other Blood Parasites,” by
Stephens and Christophers, published by The University Press of Liverpool,
1908. Doctor Stephens has consented, and the following account of the anatomy
of a female Anopheles is taken from this work :

GROSS ANATOMY.

“THE ALIMENTARY CANAL.

“The alimentary canal is specialized on account of the blood-sucking habits
of the mosquito. It differs from many insects in not possessing any cecal
diverticula of the mid-gut. It also differs in the possession of five malpighian
tubules, these being in insects usually even in number.

“The parts of the alimentary canal are as follows:

The mouth

The pharynx with pumping organ {ms e fore-gut.
The csophagus

The esophageal diverticula

The homologue of the proventriculus

The stomach (so-called) The mid-gut.
The pylorus

The pyloric dilatation

The ileum Sig
The colon frm hind-gut.

The rectum with rectal papille

“The mouth, pharynx, and cesophagus are ectodermal in origin, and both the
mouth and pharynx are lined with chitin. The hind-gut is also ectodermal in
origin ; it does not possess, however, any portion lined with chitin. The mid-gut
is the true digestive portion of the tract. ;

“The Pharynz.—The pharynx, which is lined throughout its extent with
chitin, passes upwards and backwards through the ganglionic ring formed by

75
76 MOSQUITOES OF NORTH AMERICA

the supra and infra-cesophageal ganglia and their commissures. At first it is
narrow, but posteriorly becomes a large chamber (the pumping organ).

“The pumping organ occupies with its muscles a large portion of the head
behind the level of the cerebral ganglia. In the state of rest its lumen is tri-
radiate in transverse section. The walls are formed of three large and thick
chitinous plates, one placed on either side, and one superiorly. Into each of
these plates powerful muscles are inserted. The plates are connected by thin
non-chitinous membrane, and their edges are rolled so that they form a spring
capable of returning to their original position so soon as the separating force of
the muscles ceases.

“ Posteriorly, where the pharynx becomes very narrow, a sharp bend occurs
and a valvular action is produced. The whole forms a very powerful suctorial
apparatus.

“The Gsophagus—Immediately beyond the pumping organ the chitinous
layer ceases, and the rest of the fore-gut is formed of excessively thin membrane.
At the junction of the two portions a sharp bend occurs, and the floor projects
so as to form a valvular flap.

“The thin-walled cesophagus is a large dilated sac, whose walls are supported
by surrounding structures. Into the posterior wall of the dilated and thin-
walled cesophagus projects the papilla-like anterior portion of the mid-gut.

“The Dwerticula of the @sophagus—From the cesophagus two or three
diverticula, similar in nature to the cesophagus, extend backwards. Of these,
one is of great size, and usually contains gas bubbles. This usually extends into
the abdomen, and is a prominent object in dissections and sections.

“ The Homologue of the Proventriculus.—There is no true proventriculus as
in many insects. There is, however, an interesting fold of the fore-gut into the
mid-gut which represents this organ. The muscular bundles are here increased,
and the whole forms a valvular muscular organ.

“The Mechanism of Feeding.—The powerful pumping action which must
result from a drawing asunder of the three large chitinous plates of the pumping
organ is very evident. These plates, also, when drawn apart must, by reason of
their spring-like shape, revert to their original positions close together, without
any muscular aid. Posteriorly the valve-like arrangement mentioned before
prevents regurgitation. Further, when the blood reaches the junction of the
cesophagus and mid-gut the invaginated portion is withdrawn, and is distended
by the entering blood into a distinct ‘ crop, the valvular function is suspended,
and the blood flows onward.

“ The Mid-gut.—The mid-gut extends from the proventriculus to the origin
of the malpighian tubes.

“The anterior narrow portion of the mid-gut lies in the thorax, and does not
become distended with blood. The posterior portion when fully dilated fills the
greater portion of the abdomen, the viscera being pushed into the last few
segments.

“ The Hind-gut.—The hind-gut is short and passes in one or two bends from
the pylorus to the anus. Immediately beyond the pylorus there is a considerable
dilatation which is poorly supplied with muscular fibres: into this open the five
malpighian tubules. For a short distance beyond this the lumen is narrow
(ileum), but becomes gradually larger (colon). At the termination of the colon
there is a slight constriction, after which the canal dilates again to form the
rectum.

“ Into the rectum project six solid growths, the so-called rectal glands, which
are, however, papilla. Posteriorly the rectum ends in the anus close above the
genital canal.
(ESOPHAGEAL DIVERTICULA T7

“The appendages of the alimentary canal are :—

“ The Salivary Glands.—The salivary glands consist of six tubular acini lying
three upon either side. A duct can be seen traversing almost the entire length of
each acinus. Shortly after leaving the acinus, the three unite to form a single
duct. Beneath, and in contact with the lower surface of the subcesophageal
ganglion, the ducts of each side unite to form a common salivary duct which
passes forwards and enters the chitinous first portion of the alimentary canal
close to the base of the proboscis.

“ The Malpighian Tubules.—These are five in number and open into the first
portion of the hind-gut immediately beyond the pylorus. Their blind ends are
held in position in the neighborhood of the rectum by tracheal branches. They
pass forwards in loops above their origin, so that, in transverse section, as many
as ten may be seen cut across.

“The Vascular System.—As in most insects where the respiratory system
ramifies throughout the whole body, the vascular system is not well developed.
A dorsal vessel or heart and an anterior prolongation of this (aorta) are the only
closed blood-vessels. Apart from the dorsal vessel the blood circulates in large
blood spaces, which lie between the lobes of the fat-body and among the muscles
and viscera.

“The dorsal vessel passes close beneath the tergal plates throughout the
abdomen. It is very thin walled, and is not provided with valves. The upper
portion is attached to the dorsum at intervals by suspensory fibres (muscular),
so that a festooned appearance is given in longitudinal section. There is, how-
ever, no true division into compartments. Laterally large cells (pericardial
cells) are arranged throughout its entire extent, and fibres of a muscular nature
(alary muscle) pass from the body wall and end in branches in close connexion
with the dorsal vessel.

“ At the first abdominal segment the dorsal vessel dips down beneath the
mesophragma, lying as it does so in direct contact with the cuticle. In the
thorax it again arches upwards, and lies between the lower portions of the
antero-posterior wing muscle close above the anterior portion of the mid-gut.

“ In the anterior third of the thorax it divides into two smaller portions which
pass outwards, and coming in contact with the salivary ducts enter the neck.

“ Blood spaces without definite walls occur throughout the body. The thorax
especially contains large spaces among the muscles, and the complex fat-body
which lies between and supports the organ is everywhere bathed with blood

fluid.”

The diverticula of the cesophagus are of sufficient interest to warrant further
remarks. There are three of these diverticula, arising near the posterior end of
the cesophagus. Two of them are dorso-lateral and small, the third one is ven-
tral and very large and extends into the abdomen. Dufour examined these
organs carefully and speculated regarding their possible function, assuming that
they were in some way connected with the digestive process. He called the
smaller pair “ bourses ventriculaires,” the large one “ panse” or paunch. In
fact this paunch is the so-called “ sucking stomach,” “ food-reservoir ” or crop of
many other insects. In the mosquito it is, when expanded, globose, ovoid. Du-
four states that when empty it is folded into plaits. Graber has determined that
in flies this organ actually serves as a food-reservoir by feeding them with colored
liquid. Dufour found that when the stomach of the mosquito is distended with
blood the paunch is filled with a colorless or faintly amber-tinged liquid. He
78 MOSQUITOES OF NORTH AMERICA

supposed that this liquid was lymph from the cutaneous tissues, which the mos-
quito must suck before the flow of blood into the capillaries is brought about.
He thought that possibly this liquid was afterwards rejected by disgorging, or
that it was held in reserve against future needs. The two smaller diverticula
Dufour found to be filled with an amber-colored liquid and with bubbles of air
and he states that their volume is variable, according to contents. Thompson
and others have observed that all three of the diverticula are usually filled with
air. Christophers, in considering the mechanism of feeding, discusses the
diverticula as follows:

“In mosquitoes as usually killed, the proventriculus and anterior portion of
the mid-gut are considerably distant from the posterior end of the pumping
organ, so that the large delicate walled cesophageal chamber with its extensive
diverticula intervene. Immediately after feeding, however, though blood is very
evident in the mid-gut, and even in the calyx-like proventriculus, yet in the
cesophagus there is no trace. As this latter is so large and has such delicate
walls, it is evident that, in the act of feeding, the calyx-like proventriculus must
be applied directly to the posterior opening of the pharynx, thus shutting off the
capacious oesophageal pouch. The large esophageal diverticulum probably acts,
not only as an air chamber to specifically lighten the body of the mosquito, but
also as an air pad to distribute the pressure of the large coagulum formed in
the mid-gut after feeding. In a fed mosquito a transparent area is generally to
be seen in front of the opaque mass of blood in the abdomen. This transparent
area is the abdominal portion of the air-containing cesophageal diverticulum.”

It is undoubtedly the presence of air that led Giles to the view that the
diverticula belonged to the tracheal system. He calls them “ pneumatic sacs ”
or “ aspiratory vesicles ” and claimed that they were part of the tracheal system
and not connected with the digestive tract. This view has been thoroughly con-
troverted and Thompson states that the diverticula “have a less extensive
tracheal supply than any other part of the alimentary canal, except possibly the
pharynx and antlia.” Giles thought that there were two ventral sacs and that
they have an aerostatic function. He makes the interesting statement, which
should be investigated further, that “the more gorged the insect or the heavier
it be with eggs, the larger will these sacs be found . . . .”

Eysell appears to have studied the diverticula and their function most care-
fully. He calls the large ventral diverticulum “ Vorratsmagen” (reservoir-
stomach) and the two dorsal diverticula “ Flugblasen ” (flight-bladders). He
states that the dorsal diverticula are always filled with air and that this is
usually also the case with the ventral one. However, after a meal the ventral
diverticulum is filled with nectar, fruit juices or blood which remains there for
hours, and with low temperature even for days.

“Sweetened watery solution of litmus is readily taken by mosquitoes. As
long as it remains in the reservoir-stomach it retains its beautiful blue color.
Transmitted to the mid-gut it turns red at once and also remains red in the
hind-gut. Only when the blue color has completely given way to the red has
the reservoir-stomach given up the last vestiges of the sugar solution to the
mid-gut. By this simple experiment, which can be easily repeated at any time,

one can determine with certainty how long nourishment remains in the reservoir-
stomach at determined temperatures.
REPRODUCTIVE ORGANS 79

“When the reservoir-stomach, which is supplied with longitudinal and en-
circling muscles that furthermore are assisted by the pressure of the body, has
ie by little given up the nourishing liquid to the mid-gut air again takes its
place.

“The air is in part swallowed, as one can observe in emerging * mosquitoes
by the increasing inflation of the abdomen and the movements of the pharynx-
pump, very nicely visible through the as yet unpigmented clypeus. Later, how-
ever, it is also produced in situ, in the form of carbonic acid, through vegetable
comensals, an yeast mould (Laveran, Schaudinn) ; at the same time an enzyme is
formed in which Schaudinn has recognized the poisonous, wheal-producing
substance which the mosquito introduces when stinging.”

“THE REPRODUCTIVE SYSTEM.

“ The organs of the reproductive system are:
1. Ovaries.
2. Oviducts and common oviduct.
3. Mucus gland and duct.
4. Spermathece and ducts.

“ The ovaries occupy a variable position dependent upon the state of their de-
velopment. In the newly-hatched mosquito they are small bodies lying in the
fourth and fifth abdominal segments close by the posterior portion of the mid-
gut, hind gut, and malpighian tubes towards the venter, so that eventually the
ovaries occupy nearly the whole of the posterior portion of the abdomen. Each
ovary consists of very many follicular tubes, each containing egg follicles in dif-
ferent stages of development. In the mature ovary the lower follicles have in
every tube become the large completely-formed egg.

“The oviducts are muscular tubes passing from the ovaries. They join be-
neath the rectum to form the common oviduct, which is still more abundantly
supplied with muscle fibres, and which eventually opens beneath the anus.

“ The spermatheca is a chitinous sac, which in the impregnated female is filled
with a mass of spermatozoa. Its duct is long and twisted and opens into the
common oviduct near its termination. (In Culex spp. there are three sper-
mathece. )

“The mucus gland, globular or ovoid in shape, opens by a short duct into the
same region.”

Neveu-Lemaire has shown that the number of spermathece or receptacula
seminis present in the female differs in certain genera. He determined that in
Anopheles there is but a single receptaculum seminis, in the oriental Manso-
niodes uniformis there are two receptacula seminis and in Culex pipiens there
are three of these receptacles. We have found that in Uranotenia and Aédeomyia
there is, as in Anopheles, but a single receptaculum seminis. In all the other
American mosquitoes we have examined, including several species of Mansonia,
there are three receptacula seminis. When three receptacula are present one of
them is often larger or smaller than the other two.

“THE FAT-BODY.

“The adipose tissue is disposed in two ways.

“1, As a general lining to the body wall, being nearly everywhere present
directly beneath the cuticle, and

“2. As lobular masses lying in among the organs and muscles. Thus a large
pad lies over the compound thoracic ganglion, and sends processes which lie in

 

*“ During the pupal stage the diverticula contain no air whatever, in the newly emerged
imago they ate on the entree. dilated with air. The newly issued mosquito therefore floats
even on alcohol.”
80 MOSQUITOES OF NORTH AMERICA

among the salivary glands and other viscera. Other smaller masses lie in the
head and abdomen.”
THE TRACHEAL SYSTEM.

There are two main tracheal trunks, passing along each side of the body near
the digestive canal. A branch is sent off to each spiracle and other branches pass
to the different organs and ramify through the body. The thoracic spiracles
are described on another page in connection with their function in the produc-
tion of sound. Both spiracles and trachee of the thorax are greatly developed.
The abdominal spiracles are very small and the tracheal trunks are much more
slender in this part of the body than in the thoracic region. No large air-sacs
belonging to the tracheal system are present. The branches of the tracheal
system are described by Christophers as follows:

“ The Trachee.—Very large trachee pass inwards from the anterior thoracic
spiracles.

“1. A large branch passes forwards towards the neck and gives off a branch
which passes down on either side of the middle line to the two anterior coxa and
the salivary glands. The main branch continues on through the neck, and sup-
plies the head with numerous large branches.

“2. A large branch passes upwards and backwards along the edge of the meso-
scutum, and gives off branches which supply the wing muscles. A smaller
branch also passes forwards and supplies the muscles of the thorax.

“3. The largest trachea in the body (main trachea) passes downwards, back-
wards, and inwards, so as to lie on either side of the anterior portion of the
alimentary canal. Numerous branches are given off from this trunk to the
thoracic muscles, the alimentary canal, and legs. Posteriorly the trunk is con-
tinuous with a trachea passing forwards from the second thoracic spiracle, thus
forming on either side a large tracheal loop.

“ Large trachee also pass inwards from the posterior thoracic spiracles.

“1. Branches pass forwards and join in a loop with the main trachea, also
backwards to join the abdominal system.

“2. Branches pass downwards to the meta-thorax and posterior pair of legs.

“ 3, Branches pass inwards to the muscles and mid-gut.

“From each abdominal spiracle a short thick trunk passes inwards which
gives rise to the following branches :—

“ A dorsal branch ramifying beneath the tergum and joining the branch of the
opposite side.

“ A sternal branch supplying the sternal plate and muscles, also joining the
branch of the other side.

“ Loop branches passing to the trunks anterior and posterior.

“ Branches passing inwards and supplying viscera. Branches from the first,
second, third, and fourth abdominal trachee supply mainly the mid-gut, those
from the fourth and fifth the ovaries, those from the sixth and seventh the
genital organs.”

* HISTOLOGY.
“THE ALIMENTARY CANAL AND APPENDAGES.

“The epithelial lining differs considerably in the mid-gut from either the
fore-gut or hind-gut. In the mid-gut the possession of a marked striated border
by the epithelial cells is characteristic. The muscular fibres of the alimentary
canal are striated throughout.

“ The Fore-gut.—The anterior portion of the fore-gut is lined by chitin and
does not differ from the cuticle in structure. It consists of a single layer of
cubical cells of small size. The cesophageal dilatation and its diverticula re-
HISTOLOGY 81

semble one another in structure. In the adult mosquito they consist of an
extremely delicate membrane formed of a single layer of flattened cells, with
externally some scattered muscular fibres. In fresh preparations peculiar wrink-
lings of this membrane are seen, which may appear like bundles of sporozoits.
A similar appearance is seen in the dilated portion of the hind-gut just beyond
the pylorus.

“In the majority of mosquitoes the walls of the esophageal diverticulum are
crowded with micro-organisms and bodies which appear to be protozoal in
nature.

“The Mid-gut.—The epithelium consists of a single layer of large cells,
which are columnar in the undistended organ, but become flat and pavement-
like when the organ is full of blood. They have a finely-reticulated protoplasm,
which stains more deeply towards the free border. Stained with Heidenhain’s
hematoxylin, alcohol-hardened specimens are seen to contain numerous stained
granules, collected especially in the outer portion of the cell. These are espe-
cially abundant in the anterior portion of the mid-gut. They have also, very
frequently, a number of small clear vacuoles (droplets), which become more
frequent and of larger size towards the free border of the cell. The most marked
feature of the cell is the clear striated border which is present in all the cells of
the mid-gut, but absent in all other portions of the alimentary canal. The
striated border is best marked in the undistended organ, and becomes almost
invisible in the fully distended state, when the cells are much flattened.

“ The nucleus of these cells is large and centrally situated.

“The muscular coat is very thin. It consists of an open mesh-work of long
muscular fibres running longitudinally and circularly.

“The individual muscle fibres are very long, fusiform, striated fibres. On
the outer surface of the mid-gut lie numerous large branched cells in which the
small trachese end, and from which bundles of minute structureless air tubes
pass into the wall of the mid-gut. These cells are frequently well shown in gold
chloride specimens. Similar cells occur throughout the viscera in connexion
with the tracheal endings.

“The Hind-gut.—Structurally the small and large intestine are similar,
whilst the dilatation beyond the pylorus, and especially the rectum, differ from
these.

“The dilatation which occurs at the origin of the malpighian tubules is thin-
walled and poorly supplied with muscle fibres. The cells lining it are small and
flattened.

“The intestine is lined with a single layer of large cubical cells; external to
these is a muscular coat. The cells of the intestine have large nuclei. The pro-
toplasm is finely reticular, and stains less deeply than that of the cells of the mid-
gut. Stained with Heidenhain’s hematoxylin, no granules are present as in
the cells of the mid-gut. They have no striated border.

“Tn the rectum the cells become small and flattened. There are here, how-
ever, bodies usually termed rectal glands. These are papille covered with a
single layer of much hypertrophied cells resembling those lining the small in-
testine and colon.

“ The Salivary Glands.—The salivary acini lie in a cleft in the fat-body, which
latter comes in close contact with the glands. Each gland acinus consists of a
single layer of large cells, limited externally by a delicate sheath (basement
membrane) and internally by the intra-glandular duct wall.

“In Anophelines the intra-glandular duct becomes larger as it approaches
the termination of the acinus, and forms a large cavity.

“In Culicines the duct remains of the same diameter throughout the acinus,
and terminates abruptly near the end of the acinus without any dilatation.
82 MOSQUITOES OF NORTH AMERICA

“Tn both Culicines and Anophelines there are two types of gland acinus.
These are recognizable both in the fresh gland and in fixed specimens. From
their appearance in the latter they may be termed

(1) The granular type.
(2) The clear or colloid-like type.

“The Granular Type-——The greater portion of the acinus consists of cells
whose nucleus and protoplasm has been pushed to the outer portion of the cell
by a large mass of secretion which occupies almost the whole of the cell. In the
fresh gland this secretion appears as a clear, refractive substance, and can, by
pressure, be made to exude from the cell in refractive globules. In specimens
hardened in alcohol, this clear secretion appears as a granular mass, occupying
the greater portion of the cell. It stains faintly with hematein, and shows under
high powers a coarse reticulum and isolated globules, an appearance probably
due to the precipitation or coagulation of the secretion by the alcohol.

“The protoplasm of the cell occupies, in the fully-matured gland, only the
extreme periphery, and the nucleus, which is much degenerated, is pushed to
the outer portion of the cell, and usually lies in the angular interval left at the
base of two or more contiguous cells.

“ The Clear or Colloid-like Type.—Of this type there is but a single acinus
upon either side, which usually lies between the two acini of granular type.

“Tn the fresh gland the cell outlines are not so distinct as in the granular
type, and the secretion, when extended by pressure, is much less refractive. In
alcohol-hardened specimens, the acinar cells contain a large mass of clear, homo-
geneous secretion which, as in the last-mentioned type, fills almost the entire
cell, and pushes the protoplasm and nucleus to the periphery.

“ Tn the clear type, however, the protoplasm is always in greater amount than
is the case with the granular type, and the nucleus never becomes so greatly
degenerated. The clear, homogeneous secretion stains readily with hematein,
and may even stain quite deeply. With Heidenhain’s hematoxylin it frequently
becomes almost black. It resembles very much in appearance colloid substance
as it is seen in the mammalian thyroid.

“In Anophelines this substance also distends the central duct space within
the acinus. In this situation an appearance is sometimes produced which re-
sembles faintly-stained sporozoits, but which is a normal condition.

“ The Malpighian Tubules.—The malpighian tubules are tubular bodies with
cecal ends, which open into the hind-gut. The cells are extremely large, being,
next to the pericardial cells, the largest in the body. Each cell contains a large
nucleus, and contains numerous large granules which stain feebly with hem-
atein, but powerfully with Heidenhain’s hematoxylin. Numerous fatty granules
are also present. Hach cell is wrapped round a central lumen, the cells being
arranged alternately, so that a zig-zag appearance is given in section. The inner
portion of each cell is markedly striated, the lumen being thus bounded by a
striated area. In relation with these tubules, a large number of trachee and
tracheal end-cells exist.

“Tn certain conditions the malpighian tubule cells may be found quite free
from granules, though otherwise unchanged. This change occurs in mosquitoes
with large numbers of flagellates in the rectum and hind-gut.

“ The Vascular System.—The dorsal vessel is a delicate-walled tube composed
of longitudinal and oblique fibres with a nucleated inner layer. The fibres may
be traced directly from the terminations of the branched alary muscle fibres.
The alary fibres break up into fibres which pass in close connexion with the large
pericardial cells, and eventually form (1) fibres passing into the dorsal vessel
as longitudinal fibres, (2) fibres joining in an anastomosis in connexion with the
floor of the dorsal vessel.
HISTOLOGY OF FEMALE ORGANS 83

“The pericardial cells are extremely large cells lying on either side of the
dorsal vessel throughout its whole extent. They are by far the largest cells in
the mosquito, varying from 30» to 50 in longitudinal diameter. They are
elongate or pear-shape in form, and contain several nuclei. The nuclei usually
show signs of degeneration. The peripheral portion of the cell stains more
deeply than the central portion, which contains the nuclei and small stained
granules. There is a considerable number of masses of a light yellowish pigment
resembling that found in the large visceral ganglia cells. The fibres from the
branches of the alary muscles pass over and around the pericardial cells to reach
the dorsal vessel. From their structure and situation the pericardial cells
appear to be of the nature of ganglion cells.

“ The Fat-body.—The fat-body, both where it occurs as a portion of the body
wall and where it lies as free lobulated masses, consists of cells containing
numerous oil globules. The cells are of considerable size, and their borders may
be frequently traced as polygonal areas. The nuclei are oval in shape with a
central mass of chromatin and chromatin threads. Besides oil globules the cells
contain granules staining with hematein, and minute droplets of a highly re-
fractive, dark substance, which gives the appearance of pigment. These drop-
lets are larger in amount in old mosquitoes than in those freshly hatched.”

THE REPRODUCTIVE SYSTEM.

“ Hach ovary consists of a large number of follicular tubes whose lower ends
open into the ovarian tube, and whose upper ends terminate in a delicate sup-
porting filament (terminal filament). The apex of the ovary is formed of a
single follicular tube, whose filament is attached to the fat-body of the fourth
segment,

i Aeon the whole ovary there is a delicate nucleated sheath.

“Hach follicular tube contains one or more egg-follicles in different stages
of development. In the freshly-hatched mosquito each follicular tube contains
an undeveloped egg-follicle. As this develops, a second and a third undeveloped
follicle appear above it, which again undergo development into mature eggs.
The follicle at first consists of two to four large cells, with large nuclei sur-
rounded by a single layer of smaller epithelial cells.

“The central cells then increase in size and number, so that many very large
cells are contained in the now enlarged follicle. The surrounding epithelial
cells also become larger, and rapidly increase in number so as to form a layer
of regular cubical cells surrounding the follicle. The central cell nearest the
ovarian tube is the ovum, the rest are nurse cells, and eventually disappear.
Both the ovum and the nurse cells increase greatly in size.

“ Frequently in Anophelines a large portion or the whole of the adult ovum
consists of a mass of Sporozoa. These consist of numerous small cysts, each
containing eight round or crescent-shaped bodies, each with a central chromatin
spot.

me The ovarian tube arises in the centre of the ovary, and receives on all sides
the follicular tubes. It is lined with a single layer of small cubical epithelium.
After passing out of the ovary, a considerable number of striated muscular fibres
are arranged in a loose net-work around it, and pass from it to surrounding
structures. ; i

“ The spermatheca consists of a chitinous sac, with large cells lying externally.
These resemble the cells of the cuticle, and contain droplets. They do not cover
the whole of the surface of the spermatheca. The spermatozoa have a narrow,
slightly-curved head and a long tail. The duct of the spermatheca is narrow and
thick-walled, and contains muscular fibres. Certain large cells lie in connexion
with the duct externally. The mucus gland contains cells filled with secretion.”

7
THE LARVA.

All mosquito larve are aquatic. They possess a complete, well-chitinized head
with the typical mouth-parts of mandibulate insects. The thorax is broad and
its three segments are fused. The abdomen is long and slender with nine well-
defined segments. There are no ambulatory appendages. The anal opening is
at the apex of the ninth segment and is surrounded by four more or less de-
veloped tracheal gills. The tracheal system is metapneustic with the openings
dorsally on the eighth segment, usually through a chitinous tube of greater or
less length. The larve are active and move backward through the water by
jerking the body from side to side. They also can move slowly forward by the
action of the mouth-brushes. By means of a mechanism at the end of the respir-
atory tube the larva can suspend itself from the surface film in order to take
in air. Raschke has pointed out that the breathing tube has the further function
of an hydrostatic apparatus. It will be most convenient to discuss in detail the
structures of the larva of Culex and afterward point out the various modifica-
tions that occur in other mosquito larve.

THE HEAD AND MOUTH-PARTS.

The head of the Culex larva is broad, rounded, and somewhat flattened. It
is inserted upon the thorax by a narrow neck, the opening into the head being
surrounded by a heavy chitinous collar, the foramen. The antenne are promi-
nent and inserted anteriorly upon the outer angles of the head. Between the
antenne the head is arcuate and a narrow clypeus forms its anterior margin.
In front and beneath is the labrum with its appendages. The median free lobe
of the labrum is attached between two long, stout spines which project forward
and downward from the anterior margin of the clypeus. The other mouth
organs are upon the ventral side of the head and the anterior part of the head
may be considered a broad rostrum which projects over them. The eyes are
placed laterally and consist of two pairs, the large compound eyes, and behind
them the accessory eyes.

The antenne consist of a single chitinous piece and are cylindrical and
slightly curved. About two-thirds from the base the shaft is suddenly narrowed
and at this point is inserted a fan-shaped tuft of long feathered hairs. The
slender apical third is obliquely truncate at the tip. Upon the tip is inserted a
conical sensory organ surrounded by three long sete and a shorter spine-like
seta. Raschke interprets the sensory cone as an olfactory organ. It has a
chitinous cylindrical basal portion with a minute spinous process upon its side
and a very delicate conical sensory portion at the apex. The antennal shaft is
beset with numerous small spines. The antennx have but little motility. They
are controlled by a single rather weak muscle, inserted at the base and running
backward to the hind margin of the head. The antennew are connected with the

84
LARVAL MOUTH-ORGANS 85

head by an elastic membrane which has some small chitinizations imbedded in

it. A spine-like projection of the side of the head prevents the antenna from
turning outward.

Several hairs or hair-tufts are inserted on the head integument of the larva.
Three pairs of these are situated dorsally on the front or epistoma. One pair is
inserted close to the antenne and is usually the best developed; the other two
pairs are inserted nearer the median line and more or less approximated. These
hairs or hair-tufts differ in development, and also in position, in different forms
and are valuable for specific diagnosis.

The mouth-parts consist of labrum, mandibles, maxille with their palpi, and
labium, grouped around the pharyngeal opening.

The labrum plays an important réle in bringing food to the mouth and on
this account is highly developed and complex; its position is on the under side
of the anterior portion of the head. Three parts of the labrum can be dis-
tinguished, two lateral portions and a median one which projects freely from
the anterior margin of the head and has been called the palatum. The lateral
pieces have inserted upon them dense masses of long yellow hair, the so-called
mouth-brushes. By the action of powerful retractor muscles and their relaxa-
tion the side-pieces are jerked backward and forward and communicate to the
mouth-brushes a lashing motion. The labrum and adjoining parts are described
by Thompson as follows:

“The relations of the pre-antennal region of the head are hard to describe.
As noted, the dorsal surface is convex and heavily chitinized. The ventral face
slopes sharply inward and downward toward the entrance to the pharynx, a point
almost in the center of the head. Thus the pre-antennal region is in reality a
broad rostrum which overhangs the mouth-parts, situated near the transverse
line below, slightly forward of the entrance of the pharynx. Its cross-section
would be the segment of a circle, the arc being represented by the convex dorsal
surface. In the mid-ventral line, about halfway between the anterior shelf-like
fold and the entrance of the pharynx, a crest is formed. This bears four stout
sete and is flanked by setose areas. Here the thin chitin characteristic of the
ventral face of the rostrum generally, is strengthened by a triangular sclerite.
I regard this structure as an epipharynx. It receives a pair of slender muscles
(Raschke, 1887) which arise on the top of the head and probably function as
retractors.

“The border line and shelf-like fold already described, mark the boundary
between the heavier chitin of the dorsal and the thinner chitin of the ventral
face of the rostrum, above and in front. But on either side, near the antenne,
the thicker chitin involves part of the ventral face of the rostrum. These in-
flected areas of heavy chitin I call the black-spot areas, because each bears a
conspicuous patch of pigment. From either area a narrow-linear ‘line’ of
heavier chitin traverses the ventral face of the rostrum to strengthen the sclerite
of the epipharynx. In the bay of thin cuticle bounded in front by the anterior
shelf and border line, and posteriorly by the black-spot areas, lie the small,
median palatum and the larger, lateral flabelle. These are protuberances,
densely clothed with fine hairs, the flabelle having in addition a peculiar ar-
rangement of long yellow sete. Black-pigmented apodemes that are continuous
externally with the black-spot areas enter each flabella and the two flabellx are
united by a transverse rod. To the apodemes the flabellal muscles are attached,
two for each flabella, an inner and an outer, both retractor in function and act-
86 MOSQUITOES OF NORTH AMERICA

ing simultaneously. When these muscles contract the seta-bearing area of the
flabella is depressed and the setze come together in a brush whose tip points
caudad. On their relaxation the flabelle protrude beyond the front of the head
and the sete stand out in great yellow fans. ‘The median prominence or pala-
tum passively follows the movements of the flabellz, which are strictly syn-
chronous, as far as J have observed.”

The palatum is clothed on its dorsal surface with short but coarse spine-like
hairs; ventrally is inserted a dense tuft of long pendant hairs which swing in
unison with the lateral brushes. In the region of the epipharynx are two
fringes of dense hairs arranged in closely approximated longitudinal series. Ac-
cording to Raschke the epipharynx when in repose reaches down to the hypo-
pharynx and closes the mouth. In swallowing, the epipharynx is raised and
drawn back by two muscles inserted at its base.

The mandibles are large and elaborate in structure. In a ventral view they
lie behind the maxille and are in large part hidden by them. They are very
broad and situated well apart. The apices facing each other bear a group of
projecting irregular teeth and near these on the outer side a large movable spine
is inserted. Below the teeth there is a broad truncate chitinous projection. On
the dorsal margin is a series of seta-bearing tubercles and at the outer angle
several long spines. On the inner side there is a fringe of long hairs, inserted on
a crescentic chitinous ridge near the apical margin, which helps to sweep the
food into the mouth. The mandibles are moved by two pairs of powerful
muscles. A muscle attached to the lower inner angle draws the mandible down-
ward and inward, another muscle at the outer lower angle draws it outward. At
their opposite ends the muscles are broadly attached in the posterior part of the
head to the epicranium walls.

The maxille are large but very simple, showing none of the components trace-
able in most mandibulate insects. They are flattened, roughly conical with a
small basal appendage, the maxillary palpus, on the outer side. The maxille
are situated upon the apical ridge of the under side of the hypocranium and
cover the mouth from beneath. Like the mandibles they are well separated,
leaving an open space between them, which is however closed by projecting hairs.
There is a longitudinal suture and the surface is more or less hairy, particularly
towards the apex where the hairs are dense and long. The small palpus bears
at its apex several spine-like sensory appendages. Raschke does not think that
this palpus can be homologized with the maxillary palpus of the typical mandib-
ulate insects and he points out that different components of the maxilla of
such insects can not be traced in the maxilla of the mosquito larva. The
maxille are broadly attached to the hypocranium by a membrane and but
slightly movable. Two weak muscles effect the movement of each maxilla, both
inserted at the middle of the base and passing back are attached posteriorly to
the epicranium walls.

A broad median region of the hypocranium, bounded by strong longitudinal
sutures, constitutes the mentum.

At the attachment of the maxille the hypocranium terminates in a sharp
transverse ridge, somewhat lobed outwardly from the maxille. Behind this
EYES OF LARVA 87

ridge the parts supporting the mental and labial structures turn abruptly to the
hypopharynx and pharyngeal opening. Medianly, and immediately behind the
ridge, are four successive chitinous structures. In a ventral view these are in
order: (1) a delicate roughly triangular plate with a marginal hair-fringe and
produced into a long tooth at the middle; behind this is (2) the “ mental
sclerite,” a heavily chitinized, dark, roughly triangular, dentate plate; and back
of this (3) a complicated plate with teeth and spine-like structures, the labium ;
farther back, at the margin of pharynx is the hypopharynx, a simple chitinous
cone.

The first two plates are excrescences of the mentum; the labium is attached
to the mentum on the inner side by a flexible membrane. The labium, although
complex in structure, allows none of the typical parts of that organ to be recog-
nized ; it presents very different aspects in dorsal and ventral view. It can be
drawn back by two muscles attached to its outer angles.

The mental plate is conspicuous in preparations of mosquito larve by its dark
color and serrate anterior margin and is frequently alluded to in systematic
writings as the “labial plate.” Miall and Hammond have termed this plate the
submentum.

THE EYES.

The organs of sight of the mosquito larva consist of two pairs of eyes. In most
insects with complete metamorphosis the eyes of the larva (when present) are
larval organs, independent of the eyes of the imago; these latter only develop
towards the close of the larval period and do not become functional until the
imago-state is reached. In the mosquito, however, and in other Nemocera, the
eyes of the larva are compound in character and are those of the future imago,
they are retained throughout the different stages. Ocelli, like those of other
insect larve, are absent. The two pairs of eyes are situated laterally, a small
pair posteriorly and just in front of these are the large eyes which become the
compound eyes of the imago. The large eyes in the advanced larva are crescent-
shaped, the concave side turned posteriorly and the horns of the crescent ex-
tending backward over the dorsal and ventral surfaces of the head.

When the larva first hatches only the smaller posterior pair of eyes are present
and before hatching these are already visible through the egg-shell as two reddish
spots. The character of the eyes at the time of hatching, and their subsequent
development, are described by Zavrel as follows:

“The rose-red to brown pigment is differentiated into three portions: two
round ones and one in the shape of a band. With high magnification one finds
structures upon its margin similar to the lenses of a compound eye, which, how-
ever, are here only faintly indicated. Its nerve forms a small round ganglion in
front of the brain. On the fourth day the band or sickle-shaped main eye
appears in front of the accessory eye; first it consists of rust-brown ommatidia,
later it is pigmented black. The entire main eye does not develop at once.

“In young pup the main eye is in the form of a band pointed at the ends.
It is always pigmented deep black and one also finds scattered groups of black
pigment in its vicinity. One can never detect that it is composed of separated
red ommatidia, as it is in the young pupa of Anopheles. Only later does it take
88 MOSQUITOES OF NORTH AMERICA

on its final ovate form. The accessory eye is short and broad, at first separated
somewhat from the main eye, later partly covered by it. In young pups one can
distinguish three darkly pigmented portions in it, later it becomes entirely
black.”

Raschke states that the accessory eye has an outer transparent gelatinous
layer; out of the pigment mass projects a single crystalline column. The cornea
of the main eye is represented by a smooth layer of crystalline hypodermal cells.
The lateral parts of the supracesophageal ganglion send large nerve trunks to
the main eyes and these each send out a branch to the accessory eyes.

Similar to what Weismann has shown in the larva of Chaoborus a kind of
regressive metamorphosis takes place in the accessory eye, while the main eye be-
comes highly developed. Nevertheless the accessory eye persists in the imago as
a pigment spot, but it is hidden by the scale-covering of that part of the head.

Radl has shown that in Arthropods the compound eyes are developed from two
foci; in the course of development both of these may unite to form the eye, or
one of them may be wholly or partly suppressed. The latter is the condition in
the Culicide and other Nemocera.

THE THORAX.

The thorax consists of the fused first three segments of the body, and its
integument ismembranous. It is broad and somewhat flattened, broadest at the
middle, and without prominent angles. There are hairs present, mostly long,
along the anterior and lateral margins; these show a definite arrangement and
indicate the three elements of the thorax. At the middle and hind angles there
are large fan-shaped tufts of ciliate hairs with a common base. These hinge, to
bend forward, upon low tubercles, and are prevented from bending backward by
a small chitinous plate.

THE ABDOMEN.

The abdomen is long, slender and cylindrical and consists of nine well-defined
segments. The integument of all but the ninth is entirely membranous. The
divisions of the segments are marked by constrictions and the integument is
more delicate and flexible in that region. The first seven segments are alike in
character but differ in size, the anterior ones being much shorter and the
seventh much the longest. The first six segments bear lateral groups of long
hairs ; the hairs in the groups of the first two segments are more numerous than
in the succeeding ones and are curved and stouter. In addition to the larger
lateral hairs there are other smaller hairs, singly and in groups, which form
various series, lateral, dorsal and ventral.

The eighth segment is shorter than the preceding ones and bears dorsally
the chitinous respiratory tube. At the apex of the tube is the opening through
which the larva takes air into its tracher. The tube can be closed by a set of
flaps and these, with their mechanism, will be described later. Close to the apex
of the tube, dorso-laterally, are a pair of small movable spines. Basally on the
tube are a pair of ventro-lateral longitudinal series of dentate flattened spines
which point obliquely backward. These have been termed the pecten. At
RESPIRATION OF LARVA 89

intervals along the tube are long hairs, in several groups of twos and threes with
a common base.

Another peculiar structure of the eighth segment are the lateral groups of
small scales which form large patches behind the middle. Behind these, inserted
on a small chitinized tubercle, are large fan-shaped tufts of ciliate hairs. Simi-
lar tufts are present, near the base of the breathing tube and also ventro-pos-
teriorly.

The ninth segment is not in a plane with the others but is inserted upon the
eighth segment ventro-posteriorly, pointing obliquely downward. It is short
and its diameter is less than that of the other segments. In the final larval stage
it is in large part covered by a chitinous plate which completely surrounds it.
In the previous stages the plate is smaller, dorsal and saddle-shaped. Beyond
the plate the segment is fleshy, cushion-like with the anal opening in the middle.
Surrounding the anus are four cylindrical transparent appendages, the tracheal
gills. Dorsally, at the apex, the segment bears a group of very long sete which
are inserted upon two chitinous pieces. Ventrally and outwardly the anal plate
is excised to make room for a fleshy portion upon which is situated a remarkable
organ, the ventral brush. The ventral brush consists of a series of long fan-
shaped tufts with curved stems, inserted close together along the ventro-median
line. Each tuft hinges upon a slender transverse strip of chitin and, towards
the middle, where the tuft is inserted, these strips are thickened and perforated.
Outwardly these transverse strips are joined to a pair of longitudinal strips.
The tufts are not inserted exactly upon the median line but alternately a little
to one side or the other, thus showing the bilateral origin of the structure.
There are no muscles to control the ventral brush. Its function is that of a
steering or steadying apparatus.

THE RESPIRATORY ORGANS.

The respiratory system of the mosquito larva has been carefully investigated
by Raschke. His studies were apparently based upon larve of two species, Culex
pipiens and a species of Aédes. We give herewith a translation of the part of
his paper dealing with this subject.

“Tt is perhaps rarely that one finds in the insect world such many-sidedness
with reference to respiration asin our larva. We must here consider a stigmatal
respiration, an intestinal respiration, a respiration through the tracheal gills
and finally such a one through the external skin, therefore four different modes
of taking in gases. Naturally one of the mentioned modes will have to be con-
sidered as the most important and there can hardly be a doubt that this is the
stigmatal respiration, the breathing of atmospheric air by means of the siphon.

“ When the larvee were deprived of the opportunity to breathe air directly, by
confining them in a receptacle covered by gauze and placing this in an aquarium
so that it was entirely surrounded by water, they showed great unrest; after a
short time they shrank noticeably and died after about ten hours.

“On account of the enormous exchange of gases the tracheal system is very
extensively developed. ‘Two strong tracheal trunks extend from the apex of the
breathing tube of the penultimate body segment to somewhat before the middle
of the thorax, and these are united apically by a strong tracheal bridge. In
90 MOSQUITOES OF NORTH AMERICA

addition there are transverse connecting tubules in each segment, which however
are not in the form of a simple bridge but formed like the two links of a rec-
tangular triangle. In each segment branches go out from the longitudinal
trunks which ramify in the manner of capillaries and twine about all the organs.
The foremost ends, which are bent like knees, divide into several branches of
which two on each side pass into the head and there take a branching de-
velopment.

“ From the penultimate segment two small trunks go to the last segment.

“ At the point where the colon begins a countless number of weak, small
tracheal branches arise which run to the colon, where they resolve themselves
upon the previously described papille into innumerable branchlets. Haller, who
also saw these fine tubes, explains them as an air reservoir. This, however, with-
out considering that this would be a most unfavorable reservoir, appears falla-
cious because the branches are exceedingly fine and in comparison with the two
large tracheal trunks can only hold a very small amount of air.

“ Histologically nothing remarkable can be said of the trachea. Inwardly,
bounding the lumen, lies the chitinous integument showing the spiral threads;
around it and in intimate connection with the fat body lies the peritoneal en-
velope. Itis remarkable that the traches of the colon are without spiral threads.

“The already frequently mentioned larval organ arising from the penulti-
mate segment, the siphon, shows the following conditions: The two tracheal
trunks pass upward to the right and left inside the tube; towards the end they
lose their spiral-thread structure and become firm cylindrical cups which are
differentiated by a considerable constriction at their bases. Between them lies
a stiff, hollow, chitinous rod which unites with the two cups where they come to-
gether and helps to bound the hollow space thus formed ; thus this hollow space
is formed by the cups on the right and left and by the hollow rod above and below.

“Thus the two tracheal trunks do not empty separately to the outside, as
Haller asserts, but through a single common orifice.

“On the lower side the part of the wall of the common hollow space, which
arises from the firm chitinous tube, is continued as two flaps which rest upon the
siphon. The outer basal margins of these flaps are connected with the siphon by
an elastic membrane. On the dorsal side the wall of the common hollow bears a
median and two small flaps which are also connected with the end of the breath-
ing tube by flexible membrane.

“Tf now, by the contraction of the muscles pertaining to this apparatus, the
entire upper tract is pulled down the result is twofold: first the rigid end-cups
(of the tracheal tubes) are pressed down upon the constriction and bring about
a closure at this point; secondly by the traction upon the chitinous rod, and
through the muscles of the flaps, the flaps are brought together in the form of a
three-sided pyramid composed of the three large flaps. When the apparatus is
closed and forms, as it were, a pyramid resting with its base upon the tube, the
two small dorsal flaps lie against the ventral flaps.

“ When the larva wishes to breathe air, it sticks the end of the tube out of the
water and opens the flaps. Thereby a wreath-like formation results which
enables the animal to remain suspended from the water surface.

“The muscles of the closing apparatus originate in the penultimate body-
segment and remain free in their passage through the breathing tube. In all
five pairs of these muscles are present. Two pairs belong to the ventrally located
flaps, two pairs to the flaps lying opposite, and one pair belongs to the median
chitinous rod.

* * * * * * * *

“The anus is surrounded by four lanceolate tubes which are to be looked upon
as tracheal gills. They have an extremely fine and delicate cuticle under which
LARVA OF ANOPHELES 91

extends a rather thick layer of plasma with scattered nuclei. Each tube contains
a tracheal trunk which sends off numerous branches to the sides; the tube is
hollow and represents a blood sinus. The tracheal gills are connected with
muscles and thereby serve as closing apparatus of the colon. While ordinarily
they are disposed wreath-like around the anus, they can, by muscular exertion,
fold together into the form of a wedge.”

MODIFICATIONS OF LARVAL STRUCTURE.

Other mosquito larvae present essentially the same structures as the larva of
Culea, although variously modified. With a good knowledge of the Culex larva
there should be no difficulty in understanding the structures of other larve.
Many of these differences are brought out in the systematic part of this work,
others may be briefly noted here.

The most striking difference is presented by the larva of Anopheles in the
absence of a respiratory tube and its adaptation to the surface-feeding habit.
Aside from its adaptation to habits the larva ofAnopheles is primitive, as is in-
dicated by many of its structures. The larva when at the surface of the water
is still submerged ; it is suspended from the surface-film by means of the struc-
tures surrounding the spiracular openings on the eighth segment and by the
“ stellate tufts,” situated on the dorsal surface of the body. These stellate tufts
are little rosettes of leaf-like hairs with a common stem which spread out upon
the surface of the water. The stellate tufts are situated dorsally in pairs on
certain of the abdominal segments, and in some Old World species also upon
the thorax.

The head of the Anopheles larva is narrower and more elongate than in other
mosquito larve. The elongate appearance is due to the fact that the dorsal
region of the head is well produced between the antenne. The “mouth-
brushes” are more compact and closer together than in the Culex larva and
their mechanism is simpler. The primitive character of the larva is indicated by
the comparatively simple mandibles, the large, square maxille and the very
large, nearly independent, maxillary palpi. These latter are not inserted in a
plane with the maxille but hinge farther back upon a part of the ridge of the
hypocranium, which is interrupted at this point.

The traches open separately through spiracles on the eighth segment. An-
other primitive character of the Anopheles larva is the presence of chitinous
dorsal plates on the abdominal segments. These are small and transverse, situ-
ated at the anterior margin on all but the ninth segment. This last has a large
saddle-shaped dorsal plate.

The “lateral comb” of scales of the eighth segment of the Culex larva is
represented by two large chitinous plates, situated laterally near the posterior
extremity of the segment. These are attached to the sides of the segment by
their upper margins and project downward and slightly outward; the lower
margin is produced into a series of long irregular teeth, which point backward.
The two plates are connected posteriorly by a chitinous strip in continuation of
the thickened upper margins. These structures serve as a support to the
mechanism surrounding the spiracles. In the first stage larva of Anopheles
92 MOSQUITOES OF NORTH AMERICA

there are in place of lateral plates series of large simple spines such as are present
in some larve of Aédes.

As before stated the traches open separately. The spiracles are situated well
back on the dorsum of the eighth segment, in a slight depression surrounded by
chitinous plates. When the larva is at the surface of the water these plates are
spread out in such a manner that they support the larva and at the same time
expose the spiracles to the air. When the larva wishes to go down the plates are
folded together and form a nearly closed cavity over the spiracles. The air held
in this cavity prevents the water from entering the spiracles.

The mechanism has been described by Nuttall and Shipley and by Imms, but
neither of these descriptions are clear or wholly correct. There are six chitinous
elements in this closing mechanism. These range themselves about the spiracles
as an anterior piece, a pair of lateral flaps and three posterior pieces. Just in
front of the spiracles and overshadowing them is a small median transverse
plate, the “ anterior fan-shaped plate” of Nuttall and Shipley. This plate is
so hinged that it can be turned back over the spiracles while these latter are
withdrawn far beneath it. Close to each spiracle outwardly, is a leaf-like
fleshy flap which is strengthened distally by a small chitinous strip sur-
mounted by a sensory seta. When the larva is at the surface of the water these
flaps are directed outward and prevent the water from entering the spiracular
depression from the sides. When the larva goes down these flaps are turned up-
ward and inward and thus help to form the air-containing cavity over the
spiracles. The structures behind the spiracles consist of a very large, median,
roughly triangular plate and two smaller plates which support it. The acute
anterior end of the large plate intervenes between the spiracles and its apex is
strengthened by a chitinous peg which is attached keel-like beneath. Nuttall
and Shipley, and also Imms, claim that this chitinous peg is connected with the
anterior transverse plate, but careful study has convinced us that this is not the
case. The two rounded hind angles of the plate project well beyond the end of
the segment and the plate slopes upwards towards these angles. Medianly the
plate is flexible while the sides, and particularly the angles, are well chitinized ;
anteriorly there is a median suture. Powerful muscles attached to the middle
portion of the plate beneath, and to the anterior peg, can draw the plate down-
ward and forward. When this is done the posterior angles are bent broadly up-
ward and inward and constitute a pair of flaps which close in the spiracular
depression behind. The supporting plates support the projecting hind angles of
the median plate. They are irregular in outline, almost quadrate, and rest with
their proximal basal portions upon the thickened rim of the lateral serrate plates.

The breathing apparatus of Anopheles, just described, is the most primitive
found among mosquito larve. From it the breathing tube of the other larve is
evolved and the components of the closing apparatus are homologous with the
six pieces present in Anopheles. In Culex and other larve the stirrup-shaped
piece within the tube, through which the trachese communicate with the outer
air, is homologous with the large triangular plate of the Anopheles larva; the
five flaps surrounding the rim of the tube correspond with the five other pieces.
LARVAL MODIFICATIONS 93

In Uranotenia, which is closely related to Anopheles, the closing mechanism of
the breathing-tube is simpler than in the more specialized larvee and clearly
shows the derivation of the parts. The piece within the tube is large, of irregular
shape, and concave, the concavity towards the mouth of the tube. Its position
in the tube is transverse. The long spur which exists in Culex for the attach-
ment of the retractor muscles is absent, but two chitinous strips extend to the
trachez and support them. The opposite end is bent upward and pointed, and
against its sides the two large flaps at the rim of the tube rest. These large
flaps are ventral in their position at the apex of the tube and represent the two
posterior supporting plates of the Anopheles mechanism. The three remaining
flaps represent the two lateral flaps and the anterior plate of the Anopheles larva.
The chitinous rings of the spiracles are represented in the Uranotenia larva
by short chitinous tubes which cap the trachee. Both orifices of these tubes are
oblique and the upper ones are prolonged on the outer side and in contact with
the lateral flaps which they control.

In Culex, Aédes and other more specialized larve we find the conditions as
described by Raschke. The triangular posterior plate of Anopheles has now
become folded and elongated to the peculiar stirrup-shaped piece within the tube
which is such an important component of the closing mechanism. In these
forms the broad, hollowed out, apical portion of the stirrup closes the end of
the tube and through it the trachee open and communicate with the outer air.

The greatest specialization of the breathing apparatus is presented in the
larvee of Mansonia. The tube is modified for insertion into the roots of aquatic
plants through which the larva obtains its supply of air. The outer portion of
the tube is greatly attenuated and furnished with serrations, while the flaps at
the apex are transformed into a complex set of spines and hooks. With this
apparatus the larva can pierce the plant tissues and then, by spreading the hooks,
maintain a firm hold on the plant. The chitinous piece in the interior of the
tube, which in large part controls the mechanism, is highly developed and ex-
tends back through the tube into the body of the larva.

In the Sabethini the mechanism of the breathing tube is rather simple. The
flaps are small and the chitinous piece within the tube is reduced to a long
slender strip. The trachee are continued as long chitinous tubes which termi-
nate in oblique openings that face each other. The tubes are approximated
apically and attached to the long chitinous piece. When the larva takes in air
they are slightly protruded beyond the orifice of the breathing tube and push the
flaps out of the way. In most sabethine larve there is a pair of well-developed
freely jointed hooks dorsally at the apex of the breathing tube. In most of the
culicine larvee these hooks are present but very small; they may, however, be
well developed, as in certain species of Culex where the larva lies on the bottom
back down and uses the hooks to maintain its position.

The pecten of the air-tube is absent in the larve of Megarhinus, Mansonia
and Bancroftia, and in the Sabethini; in certain larve of the latter there are a
few spines on the tube which do not, however, appear to correspond with the
true pecten. The other appendages of the breathing tube, hairs and hair-tufts,
94. MOSQUITOES OF NORTH AMERICA

differ greatly according to the genera and species and these differences are
brought out in the systematic part of this work.

The lateral comb of the eighth segment shows great variation, not only in the
shape of the scales, but their number and arrangement. The scales may even be
absent altogether, as in Joblotia, where they are represented by single spinose
tubercles, or in Megarhinus by a chitinous plate. In other cases, as Uranotenia
and Anopheles, there is a plate with a series of teeth along the margin. The
larve of Bancroftia are remarkable in that both comb-scales and plates are
present, and in the last stage chitinous dorsal plates are also present on the sixth
and seventh segments.

On the ninth segment the chitinous plate differs greatly in shape and size in
the last stage larva of different species. It may completely encircle the segment
or be reduced to a dorsal saddle. In some forms there is a group or row of spines
or scales, laterally along the hind margin; in Megarhinus these form an elabo-
rate fringe. Laterally, on each side, is usually inserted a small hair or hair-tuft,
occasionally this becomes conspicuous. The ventral brush also varies much in
development ; in some cases it is continued into the chitinous plate, in others it
is much condensed. In some cases the ventral brush is inserted upon a separate
chitinous plate which is perforated for the insertions of the hair-tufts. In the
Sabethini there is no ventral brush but only a pair of lateral tufts or hairs below
the margin of the dorsal plate.

The tracheal gills show great modifications in adaptation to larval habits. In
certain larvee which do not come to the surface for air the tracheal gills are very
large and are traversed by a large trachea. In other forms they are obsolete and
only represented by fleshy papille. This is particularly true of the species in-
habiting saline water.

The larva of Sabethinus is remarkable in the presence of a pair of chitinous
hooks upon the seventh segment, situated upon fleshy tubercles, dorsally, near
the end of the segment. In some larve the entire integument is covered with
minute hairs or spicules and this may also be true of the plate of the ninth seg-
ment and sometimes of the breathing tube.

In certain larve there are small chitinous plates at the insertions of the large
hairs on the thorax and sides of the abdomen. These plates are particularly well
developed in Megarhinus and Aédeomyia. In many larve there are stout spines
at the angles of the thorax which prevent the long hairs from being bent back-
wards.

There is wide diversity in the coloration of mosquito larve. While certain
forms have a characteristic coloring there is often great variation in this respect ;
color, beyond the fact that certain genera show a characteristic coloring, can
not be used for identification.

All the larve of the tribe Sabethini that we have seen have a characteristic
pale appearance. The body is opaque creamy white and the head and other
chitinous parts light yellow. Only the foramen of the head is more or less
broadly edged with black, and sometimes the anal plate also shows a dark
margin. The larve of Megarhinus are dark and the integument shows a more or
PREDACEOUS LARVAI 95

less pronounced wine-red coloring; the chitinous parts are brown or piceous.
Certain South American forms of M egarhinus are said to show an iridescence,
similar to mother-of-pearl. The larva of Bancroftia also show a pronounced
red color of the body.

Generally speaking the body of mosquito larve is pale, more or less translu-
cent. It may be modified within the same species by a great variety of circum-
stances, such as age, condition of health, food, exposure to light, and the presence
of internal or external parasitic fungi or bacteria. The trachee usually show
through the integument as wavy lines of a silvery or golden luster from the air
contained in them. They become less distinct as the larva with approaching
maturity grows more opaque. The chitinous parts may be yellow, brown or
nearly black. Sometimes the head shows darker spots dorsally, characteristically
arranged. We have seen larve in which the head was entirely yellow, others
with brown maculations, others entirely dark brown, all belonging to one species.

ADAPTATION OF THE MOUTH-PARTS OF CULICID LARVA TO THE
PREDACEOUS HABIT.

The habit of feeding exclusively upon living organisms, principally upon
other culicid larve, has arisen several times independently among the Culicids.
The mouth-parts have been correspondingly modified in every case that the habit
has been developed. It so happens that the organ which has been modified for
prehension differs in the several groups. The Corethrine are all predaceous
and seize their prey with the antenne. These organs are consequently modified
for this special purpose, differing in the several genera. In these forms the
mandibles have the toothed parts well developed but the hair fringes undevel-
oped, being confined to a few filaments. The maxille in all the forms known to
us, Hucorethra, Corethrella, Corethra and Chaoborus, are progressively reduced,
being slight rudiments only in the latter two genera. This is a special modifica-
tion in this line of descent and does not represent the condition in the general-
ized culicid stock. No predaceous form will be found in a primitive condition
as the habit is secondarily acquired and accompanied by special modification.
The most generalized condition of the culicid larva is found in Diza. This
larva is a vegetable feeder with mouth-brushes on the labrum and a coarse hair-
fringe on the mandibles. It is a surface feeder. The mandibles are dentate on
the inner side toward the base. The maxille are quadrate and furnished with a
long functional palpus, comparable to the antenne in shape and size. From
such a form the culicid series is derived. The lowest mosquitoes, Anopheles, are
still surface feeders, retaining square maxilla, the palpi of which, though much
reduced, are still comparatively large. The square maxille may be regarded
essentially as organs of mastication. They are modified in the higher forms,
whose manner of feeding has become more refined, into a conical or pointed
shape with papille and hairs. There is, however, a tendency to the reappearance
of the square maxilla in the predaceous genera, in adaptation to the new habit
which requires more mastication. Throughout the Culicid series there is a
progressive degeneration of the maxillary palpi, whether the predaceous habit
96 MOSQUITOES OF NORTH AMERICA

has been acquired or not, and this serves as an index to the systematic position
of the form in question. As we have before pointed out, the Sabethini form a
separate group from the other mosquitoes. This line is not entirely ancestral,
having been derived from the culicid stem at a point near Megarhinus, above
Anopheles, Aédeomyia and Uranotenia, The mouth-parts therefore were origi-
nally in a certain state of modification, now still shown in the lowest genera
such as Joblotia and Lesticocampa. In these the maxillary palpi are rather
large, much more so than in the higher forms, such as Wyeomyia. In the Sabe-
thini, the predaceous habit has been twice acquired, in Lesticocampa and in
Sabethinus (presumably in Sabethes also, the larve of which are unknown).
In both cases the maxillee have been modified into organs of prehension, but with
essential differences. Lesticocampa is an old predaceous type, profoundly modi-
fied, derived from a generalized sabethine form (such as Joblotia). The max-
illary palpi are long and distinct, the maxille bearing semi-jointed appendages,
and the mandibles are much modified. Sabethinus is a recent predaceous
type, little modified, derived from a specialized non-predaceous form (such as
Wyeomyia). The maxillary palpi are rudimentary, the maxille of the general
type but bearing teeth and an apical horn, which is not jointed, while the man-
dibles are scarcely changed from the usual non-predaceous form. In the Ameri-
can Culicini, the predaceous habit has been acquired thrice, in Megarhinus,
Psorophora and Lutzia. We do not consider the Anopheles true predaceous
forms though some of them have the habit developed to some extent (e. g.,
Celodiazesis barberi), because there is as yet no essential modification of the
mouth-parts for this purpose, and the larve are able to subsist also on a vegetable
diet. No doubt the habit indicates the beginning of such a modification, and, if
persisted in until it became the only method of feeding, structural modifications
would follow. The Anopheles must hold their prey by the mandibles, as no
other organs are sufficiently developed for the purpose. The antenne have
already too far degenerated to become functional for the purpose, while the
maxille are of a too primitive flat type. It is necessary for the maxilla to have
progressed from this type to the conical form of a species feeding only on par-
ticles in suspension in water before its modification into an organ of prehension
would be possible. The mouth-brushes are not strongly developed enough to be
of service in holding prey. We therefore venture to predict that if any strictly
predaceous Anopheles larva exists it will be found to have the mandibles modi-
fied into organs of prehension. In the truly predaceous Culicini above men-
tioned the mouth-brushes have become organs of prehension. Megarhinus is
derived from low on the culicine stem. Its maxille consequently show a large
palpus. They are short and square, the shape being partly, no doubt, ancestral
on account of the primitive origin of the genus. The mandibles are not espe-
cially noteworthy, the toothed surface being well developed, the hair-fringe
slight. The predaceous Psorophora are derived from the lower, non-predaceous
Janthinosoma group. The maxille have regained secondarily the flattened
quadrate form but the palpus is still a small rudiment borne upon the body of
the maxilla. The modification appears at first sight profound, but is in reality
NUMBER OF MOULTS 97

superficial, all the parts present in Psorophora (Janthinosoma) sayi, for in-
stance, being easily traceable on close examination in Psorophora ciliata, the
shape only being altered. The mandibles have the toothed area well developed,
the hair-fringe much reduced.

Lnutzia is derived from Culex, from the more generalized part of that genus.
The maxille have a generally quadrate shape, but the modification from the
usual Culex type is not great. The median suture is still distinct, the papille
are present, even the crown of hairs is represented by shortened appendages. The
mandibles have the toothed area well developed and terminally placed owing to
the reduction of the other parts.

Though the three genera above mentioned, Megarhinus, Psorophora and
Lutzia, are all predaceous with their mouth-brushes, the individual hairs of the
brushes are differently modified in each, as would be expected from the inde-
pendent evolution of the predaceous habit in the three cases.

MOULTING AND NUMBER OF LARVAL STAGES.

The larve of mosquitoes have four stages, that is, they moult four times,
transforming to pupa with the fourth moult. Apparently the number of moults
is constant and is the same for all species. The newly hatched larve already
show all the organs of the mature larva but they are much simpler. The chiti-
nization of the head and breathing tube are less evident and complete than in
older larvee. The breathing tube is only chitinized in its apical portion and the
chitinous plate of the anal segment is very small. The principal hairs present
in the older larvex are already found on the first-stage larva; but all of them are
simple, whereas in the later stages many of them become composite. The ventral
brush of the culicine larve is absent in the first stage. The first-stage larva may
be recognized by the presence, on the head, of the egg-burster. This is situated
dorsally on the middle of the head and consists of an oval, pale, depressed area
in the middle of which is situated a chitinous disc surmounted by a small, black,
chitinous peg.

When the larva is about to moult the hairs of the following stage may already
be seen beneath the skin. The long hairs of the sides of the thorax and abdomen
are wrapped about the body transversely and show as transverse blackish lines.
Immediately after moulting the color of the chitinous parts is pure white;
gradually these assume their characteristic color. The approach of the last
moult may be recognized by a number of changes in the appearance of the larva.
The coloration of the body becomes more opaque. Most striking is the increase
in the size of the compound eyes, these becoming gradually drawn out dorsally
into a sharp point until they nearly meet upon the median line. This change
is particularly striking in the Sabethini where the compound eyes do not become
evident until late in larval life. A short time before pupation two dark spots
appear on the thorax, dorsally at the anterior angles. These are produced by
the breathing trumpets of the pupa lying underneath.

The moulting larva or pupa makes its escape from the old skin through breaks
in the dorsum of the head and thorax. The head splits open along the epicranial
98 MOSQUITOES OF NORTH AMERICA

suture. This suture extends posteriorly in two branches from the bases of the
antenne, the two branches uniting behind a short distance before the foramen ;
from this point backwards it forms a single median suture. It is along these
lines that the head splits open and in continuation a rent appears along the
median line of the thorax. The head moult remains attached to the skin of the
body.

The last moult, or transformation to pupa, is described by Hurst as follows:
“ Towards the end of larval life the animal becomes sluggish; profound changes
in its mouth-parts deprive it of the power of eating, and it floats with its siphon-
stigma at the surface. Shortly the cuticle bursts in the thoracic region, along
the mid-dorsal line; the pupal ‘ horns’ or siphons are protruded, the abdominal
trachee appear to collapse, and the animal floats with the anterior end up-
wards, the new siphons coming to the surface. The old larval siphon, or rather
its soft parts, are withdrawn from the cuticle and invaginated into the eighth
segment of the abdomen; the intima of the abdominal and thoracic tracheal
trunks beak up into pieces, which in the abdomen correspond to body-segments.
The body of the escaping pupa is gradually withdrawn from the larval cuticle,
and the eighteen fragments of the old tracheal intima are drawn out of the body
by nine pairs of stigmata, and cast off with the exuvie. These nine pairs of
stigmata are situated, one in the hinder part of the thorax, one in each of the
first seven segments of the abdomen, and the ninth pair are united to form a
single aperture, the old respiratory opening at the end of the larval siphon.”
THE PUPA.

The pupa of mosquitoes, like the larva, is aquatic, but depending upon
communication with the air for respiration. The pupa is active and capable of
moving rapidly through the water but it takes no food, the appendages of the
head and thorax of the future fly being enclosed in a common chitinous covering.

The appearance of the pupa differs greatly from the larva. The anterior
portion is large and very robust and composed of the head and thorax enclosed
in a common casing, in which, however, the component parts, the head with its
appendages, and the three segments of the thorax with their appendages, can
be distinguished. The head, wings and legs are packed together ventrally and
laterally, so that in a dorsal view only the dorsum of the thorax is visible. The
abdomen consists of nine flattened segments, freely movable, of which the first
eight are roughly quadrate in outline and slightly broadened posteriorly. The
eighth segment bears at its apex a pair of large chitinous plates, the “ paddles ”
or “ fins.”

Respiration in the pupa takes place through a pair of appendages on the
thorax, the “respiratory trumpets” or “horns.” The respiratory trumpets
are inserted at their bases on the mesothorax, anteriorly to the bases of the
wings, and communicate with the anterior pair of thoracic spiracles. When
the pupa is at the surface of the water the trumpets break through the surface
film and admit the air to their interior and into the tracheex.

When the pupa is at rest at the surface of the water the dorso-ventrally
flattened abdomen is curved under the bulky cephalo-thorax and almost in con-
tact with its ventral surface. In this attitude the “ paddles,” which are terminal
in position, point directly forward. By lashing with its abdomen the pupa can
descend rapidly into the water. Owing to the fact that the specific gravity of
the pupa is less than the medium containing it, the pupa is rapidly carried to
the surface as soon as it ceases its efforts. It should be noted that the specific
gravity of the pupa differs with age, the pupa becoming lighter as it approaches
maturity. There is also considerable difference according to species, the pupe
of some being so nearly of equal specific gravity with the water that they can
remain nearly stationary at the bottom or at a certain depth. Certain pupe,
when alarmed, can remain below for some time by clasping objects with the
abdomen,

The pupa is very easily alarmed and at the appearance of a shadow, or at a
slight disturbance of the water, it immediately darts towards the bottom.
Hurst has found that the cephalo-thorax of the pupa contains a large air-cavity,
which must be very effective in lightening it and in maintaining its equilibrium.
The pupa is additionally lightened towards the period of eclosion by the secre-
tion of air beneath the pupal skin, as will be described in connection with the
emergence of the imago. Hurst describes the cavity just referred to as follows:

8 99
100 MOSQUITOES OF NORTH AMERICA

“The pupa does not eat. It breathes air through the apertures at the ends
of its siphons. It floats, thorax uppermost, by virtue of a large air cavity lying
under the hinder part of the thorax and the anterior part of the abdomen. This
cavity is bounded in front by the legs, at the sides by the wings, and below by the
mouth-parts. It extends up at each side of the first segment of the abdomen,
where it is covered by the halteres, and into this part of the cavity at each side
opens a large stigma, held open by the fairly well-developed cuticular lining
(‘intima’), and guarded near its entrance by numerous spines. These two
stigmata belong to the first abdominal segment, and put the air-cavity just
described into direct communication with the tracheal system. As already men-
tioned, I regard this cavity and these stigmata as being mainly, if not ex-
clusively, hydrostatic in function, serving not only to make the pupa float when
at rest, but to make it float in a definite position, with the thorax uppermost and
the apertures of the siphons at the surface of the water.”

There is no special necessity for dealing here with the internal anatomy of the
pupa, as will be understood from the following statement by Hurst:

“ As to the anatomy of the pupa, it is only necessary now to state that at the
beginning of pupal life the internal arrangements are those of the larva; at the
end of that period they are those of the imago.”

Hurst has given an excellent description of the external conditions in the pupa
of Culez, which we quote herewith. We must, however, call attention to one dis-
crepancy: The region called by him the “ prothorax” is in reality the meso-
thorax. De Meijere, in an extensive paper on the anterior spiracles of dipterous
pup, considers the anterior thoracic spiracles and their appendages as pro-
thoracic, which, of course, also involves the region in question. A careful ex-
amination of the external conditions leads us to differ. In dipterous larve the
spiracles in question are prothoracic, in the imago they occupy a position which
can not be designated as such with certainty. Hurst’s description of the pupa
of Culex is as follows:

“The head is broad from side to side; the epicranium has a well-marked
median groove ; the clypeus, broad above, is gradually narrowed below, and con-
tinued without any distinct line of demarcation into the labrum. At the sides
are a pair of compound eyes, to be regarded rather as the rudiments of the eyes
of the future gnat than as the visual organs of the pupa itself. .. . During
pupal life they increase in size till they almost encircle the head. Corneal facets
are never formed in the pupal cuticle, but beneath it the convex facets of the
imaginal cornea are formed during pupal life.

“ Behind the compound eye, on each side of the head, is an ocellus with fully-
developed lens, etc. In the youngest pupe it is separated by a small interval
from the compound eye; but the growth of the latter obliterates this interval,
and the ocellus is in the older pupe not readily distinguishable except in sec-
tions. The statement, found in systematic works, that the Tipulariz are devoid
of ocelli is, however, not strictly true; in Culex, at least, they are well developed,
though, as they abut upon the compound eye, they are in the imago so incon-
spicuous that they may easily be over-looked.

“In the mouth-parts, the labrum, epipharynx, mandible, maxille with their
palps, labium and hypo- and epipharynx are present, though the two last can
only be seen on dissection.

“ Of their mode of origin in the larva I as yet know nothing. At the time of
escape of the pupa from the larval cuticle they are of the full size, which is con-
STRUOTURES OF PUPA 101

siderably greater than in the adult. . . . That I may not have to refer to these
parts again, I will at once say that the chief changes which occur in them during
pupal life are: (1) The development of a cuticle within the pupal cuticle, and
this, in the case of the labium (fused second maxilla), is covered with scales
closely resembling those found in Lepidoptera; (2) a considerable shrinking ;
(3) in the male only, atrophy of the mandibles, which in a young pupa are as
large as in the female, but in the adult are not recognisable.

“The antenna, which were folded and telescoped at their bases in the larva,
are in the pupa laid upon the sides of the thorax. . . . Their hinder (distal)
extremities are hidden by the wings. The swollen basal joint of the antenna of
the imago is hardly recognisable on the surface, although it is already a con-
spicuous object in sections of the youngest pups, and even in the larval state. I
shall describe it with the other sense organs. The shaft of the antenna is seg-
mented, but the external segmentation loses its correspondence with the seg-
mentation of the developing antenna within it early in pupal life.

“The thorax is large and rounded, but somewhat compressed from side to
side. Mid-dorsally the cuticle of the prothorax * is marked by fine transverse
corrugations, and this is the part which ruptures to allow the imago to escape.
- pair of branched sete arise from the dorsal region of the hinder part of the
thorax.

“The respiratory siphons are nearly cylindrical, narrowed at their bases and
curved forwards to be attached by flexible membranes to slight prominences on
the sides of the prothorax.* Above they are obliquely truncate and open, and
the margin is slightly notched on the inner side. The outer surface is marked
so as to resemble imbricated scales, each with a minute spine at its apex. The
cavity of the siphon communicates directly with that of a tracheal trunk at its
base. Palmén says that after a ‘ close investigation ’ he has found that there is
no opening. The tone of assurance in which he contradicts all previous observers
led me to put the question to the test. I removed the side wall of the thorax,
with some of the underlying muscles and trachee, from a specimen pre-
served in alcohol. I drew out the alcohol from the cavity of the siphon by means
of blotting-paper, and then touched the tip with a minute drop of glycerin. I
watched the effect under the microscope, and saw the glycerin force its way into
the siphon, driving the air before it into the trachee. Palmén, morover, says
the organs are gills! Each is a thick chitinous tube, the cavity guarded by nu-
merous hooked spines, the walls consisting of hardly anything but the chitinous
cuticle, the epidermis (‘ hypodermis ’) between its two layers being barely recog-
nisable on account of its thinness. The ‘ tracheal gills’ on which Palmén lays
much stress have absolutely no existence.

“The wings of the pupa, that is the organs within which the wings of the
imago are developing, are a pair of oblong plates about 2 1/2 mm. in length.
They are closely applied to the sides of the hinder part of the thorax, and
directed downwards and backwards. They are immoveable.

“ The halteres are a pair of elongated triangular plates lying along the dorsal
and hinder border of the wings.

« All these three pairs of dorsal appendages arise within the larva in the same
way, and their bases or points of attachment all lie in the same horizontal plane.
Each is at first (in the larva) a fold of the epidermis ; each acquires a cuticular
covering (like all other parts of the body), and the first pair become rolled up:
to form tubes, the respiratory siphons, while the other two remain flat plates.

“The three pairs of ventral appendages of the thorax, or legs, are long cylin-
drical bodies folded upon themselves, and lying beneath the thorax and between

 

*This is in reality the mesothorax. The prothorax is represented by a very small field
anteriorly, just above the base of the antenne. H. D. & K.
102 MOSQUITOES OF NORTH AMERICA

the wings. The same segmentation into femur, tibia, etc., is recognisable as in
the adult gnat, but the segments are more nearly equal in the pupa, and the
joints of the developing and shrinking legs of the future imago soon lose their
correspondence with those of the pupal cuticle enclosing them. They arise in
the larva, like other appendages, as folds of epidermis enclosing mesoblastic
tissues.

“The abdomen is dorso-ventrally compressed and exceedingly flexible dorso-
ventrally, though not from side to side. It is the only part of the pupa in which
the segmentation of the body is readily recognisable, and as I shall very fre-
quently have to refer to the various segments by number, J shall use the terms
“first segment, etc., to signify ‘ first segment of the abdomen,’ etc.

“ Nine segments are readily recognised in the abdomen, and the last one,
though it is probably composed of no less than three condensed and highly modi-
fied segments, I shall call simply ‘ ninth segment.’

“ Hach abdominal segment has a chitinous tergum and sternum, and sete are
distributed sparingly over them, being almost confined to the hinder parts of
the terga. The terga and sterna of successive segments are united by soft
arthrodial membranes.

“ Of the sete, only one pair need special mention. These are placed on the
hinder part of the first segment, the base of each being a triangular plate at-
tached by one angle to a soft membrane, and the distal side of the plate is divided
into a number of bars which, by repeated division or branching, give rise to about
one hundred sete all lying in one plane parallel to the median plane of the body.
Each seta bears a few fine hairs. When at rest, the pupa floats with the tips of
these sete, and the tips of the respiratory siphons, at the surface of the water,
and these sete probably assist in maintaining the equilibrium of the animal in
this position, as well as serving as sensory organs by means of which any dis-
turbance of the surface is felt.

“ The eighth segment bears a pair of large fins, thin oval plates about 1.2 mm.
in length, attached by the narrow end beneath the tergum behind. Each is
stiffened by a midrib which projects beyond the hinder border of the fin as a
spine.

“ Beneath the fins and behind the eighth segment is the ‘ninth segment’ with
its appendages. ‘Though this region is probably made up of more than one seg-
ment, its composite nature is not easy to recognise, as the plates supposed in
other insects to represent the terga and sterna of tenth and eleventh segments
[see, for instance, Huxley and Miall and Denny] are not developed in the young
pupa, nor, indeed, is there in any stage any such development of the pupal
cuticle, though plates developed within as parts of the imaginal cuticle may per-
haps represent some of these parts.

“The appendages of the ‘ninth segment’ of the pupa are a pair of blunt
processes arising below and in front of the anus, and directed backwards below
the fins. They are much larger in the male than in the female. A pair of ap-
pendages are already recognisable in this region in sections of the larva, and I
think even two pairs, but this portion of the larva is particularly difficult to
cut, and I am not yet certain as to the hinder of the two pairs. Of the existence
of one pair I have no doubt.”

Some mention must be made of the modifications of structure which occur in
the pupe of different species or groups of species. The early writers on the
biology of Anopheles made much of the difference in the shape of the respiratory
trumpets between Anopheles and “ Culex.” Their statements appear to have
remained unchallenged and are still widely quoted. The variations in the shape,
EMERGENCE FROM PUPA 103

size and length of the breathing trumpets between different species of mos-
quitoes are numerous, but they furnish no characteristics which are diagnostic
for genera or larger groups. The differences assumed to exist were based on
the study of a very few species and with larger series they are bridged over by
intergrading forms. Moreover, differences occur between species within a genus
far more striking than any between genera. The best illustration of this is a
species of Wyeomyia (W. circumcincta) which has exceedingly long and very
slender respiratory trumpets; no characters appear on either the imago or the
larva that are in any way abnormal for the genus. Another striking modifica-
tion 1s found in the respiratory trumpets in the.pupe of certain species of Man-
sonia. These pup do not come to the surface of the water, but remain sub-
merged, attached to aquatic plants by their respiratory trumpets. Here the
trumpets are armed at their apices with a stout chitinous spine by means of
which the pupa pierces the stems or roots of aquatic plants to extract the neces-
sary air from them.

There is considerable difference in the shape of the paddles but the remarks
just made regarding the respiratory trumpets will also apply here. It may be
stated, however, that there is a striking difference between the two tribes
Culicini and Sabethini. In the Culicini the paddles are large, broad and
rounded in outline ; they are strengthened by a stout longitudinal mid rib which
bears a spine or seta apically. In the Sabethini the paddles are much smaller,
narrower and tapered to a point ; the mid rib is either absent or poorly developed
and there is no terminal spine or seta.

Perhaps the greatest diversity among the pupe of mosquitoes will be found
in the number and arrangement of the sete on different parts of the body.
These, we are sorry to say, have not been adequately studied, but we are con-
vinced that they will furnish both generic and specific characters. Again there
is a well-marked difference in the two tribes above mentioned. In the Sabethini
the seventh and eighth abdominal segments each bear a pair of ample fan-shaped
tufts at the apical angles; these are absent in the Culicini.

There is, of course, some difference in proportions in the pupe of different
species. Generally speaking the pupe of the Sabethini have a more slender and
elongate abdomen. There is also much diversity in coloration. The Sabethini
have pale yellow pups, in some cases marked with a dark pattern. The pupe
of the Culicini are invariably darker, shades of brown and black being the usual
colors.

ECLOSION OF THE IMAGO.

Towards the end of the pupal period the pupa becomes gradually inflated with
air. It grows so light that it at last experiences great difficulty in going down
into the water and when it succeeds it is carried to the surface again with great
rapidity. Ecdysis takes place at the surface of the water and requires but a short
time, although it is by no means as rapid a process as one would be led to suppose
from the statements of certain authors. It is accomplished by the employment
of air and Eysell has given a very excellent description of the process of which
we give a translation herewith.
104 MOSQUITOES OF NORTH AMERICA

“The pupa begins to straighten the abdominal part while in the meantime
the cephalothorax retains its position. The straightening does not occur sud-
denly or by jerks, but steadily. After 10-15 minutes the operation is concluded.
Already before this the excretion of air between the epidermis (of the imago)
and the pupal skin has begun; the pupa then appears silver-white. Finally the
anterior parts of the cephalothorax are raised by a powerful jerk and now the
pupa touches the water-surface, in front with the dorsal parts of the pro- and
mesothorax, in the middle with the stigmata of the breathing tubes, and behind
with the end of the body. The previously strongly convex dorsal surface of the
animal has become concave. :

“ Now the pupal skin breaks exactly along the median line on that part of the
cephalothorax touching the water-surface, and at once there issues into the air,
through the gaping slit, the scale-covered, dry dorsum of the imago. By jerks
the slit is widened ; soon two transverse slits are added on each side, and after
the pupal skin has receded about ten times (synchronous on the two sides) the
thorax in its entire width appears in the cleft. Now the scutellum, the stretched
neck and the vertex of the strongly downward bent head also appear. The push-
ing forward of the mosquito’s body by jerks then ceases and the animal issues
from its prison, like the actor from a trap-door, with truly ghost-like steadiness
of motion.

“When the head is born the antenne, which lie in special chitinous sheaths
on the sides of the cephalothorax, first become free; then the palpi and proboscis,
which are enclosed in a tapering sheath lying loosely upon the pupal case, are
disengaged.

“The abdomen in the meantime has of course also moved further forward
and the last segments of the pupal skin are inflated with air.

“The insect now raises the head and extends the antenne, palpi and pro-
boscis ; then it draws the anterior pair of legs from their sheaths by bending the
knee-joints, and later also the joints of the feet, in a plane with the body-axis.
After the front legs are freed the middle legs are extracted in the same manner
and now both anterior pairs of legs are extended forward and outward as far as
possible and the tarsal joints are placed gently upon the water. Now the mos-
quito’s body, which had heretofore only balanced on the air-filled pupal skin, is
supported at five points and its equilibrium has become very steady. Then
finally the hind legs follow.

“All the legs are disengaged independently of the movement of the body
itself. They are extracted from their sheaths in pairs, by repeated very short
movements.

“ Finally the wing tips and the end of the abdomen become free.

“ The entire process is completed within a few minutes.

“The complete insect issues from the floating pupal skin almost colorless,
translucent and strongly inflated and assumes its permanent color and form
after some hours.

“The study of the motive power in the process of ecdysis gives highly in-
teresting results.

“Tn the first place, as already remarked above, the pupal skin, which had be-
fore been in close contact with the mosquito’s body, is detached and inflated to
the utmost by a layer of air which is pressed out of the stigmata of the imago.
The previously dark pupa becomes shining silvery. The increasing pressure
within causes the pupal skin to burst at its weakest point over the thorax and at
the same time tears the connection of the breathing trumpets with the tracheal
system of the mosquito.

“ Now the layer of air surrounding the mosquito’s body stands in direct con-
nection with the atmosphere and at once the animal begins to swallow great
quantities of air.
INGORGEMENT OF AIR 105

“Hereby the volume of the mosquito is considerably increased; the pupal
case can no longer hold it, and, at a time when the hind end of the body still
remains exactly in the same position as during the pupal stage, the greatly
lengthened body is already forced a considerable distance through the slit in the
thorax. Through the ingorged air the abdomen loses its limpness, it is stiffened
like an air-inflated bladder and continues to increase in volume proximally.
The conical form of the body thus brought about causes it to glide forward in the
anally narrowed pupal skin, and under normal conditions this motion needs
hardly any assistance from the abdominal muscles.

“The specific weight of the animal is greatly diminished by the taking in of
great quantities of air, a circumstance which is equally important for the imago
when issuing and immediately after.”

It appears from the observations of Eysell that the three diverticula of the
cesophagus perform an important function at this time, they receive the swal-
lowed air and it is by their means that the volume of the insect is so much in-
creased. During the pupal stage the diverticula contain no air whatever, but
immediately after ecdysis they are found inflated to the utmost. We have
already discussed (page 78) the double function of the large diverticulum and
shown that in the mature insect it serves as a food-reservoir. The two smaller
diverticula remain filled with air at all times.
HABITS OF ADULT MOSQUITOES.

THE FOOD-HABITS.

Mosquitoes have engaged the attention of man largely through their bites and
on this account they have been considered blood-suckers as a group. This, how-
ever, is far from being the case. There are a great many species, perhaps more
than half, which never suck blood at all, while others do so but rarely. On the
other hand there are many species in which the craving for blood is evidently
very powerful. Everyone will have noticed the impulsiveness of attack in cer-
tain mosquitoes. Many of these will attack all warm-blooded animals indis-
criminately. Grassi states that with such species the largest animals attract
the most; thus a horse will attract mosquitoes more than a man, a man more than
a dog. Certain species of mosquitoes have a decided predilection for certain
animals. The yellow-fever mosquito under normal conditions probably feeds
exclusively upon man: more than this, it will be seen in the chapter on yellow
fever that this mosquito even discriminates between the different races of man.
Culex pipiens and Culex quinquefasciatus are closely associated with man yet
they do not persecute him with the same persistence as Aédes calopus. There is
reason to suppose that these species of Culex are primarily persecutors of poultry.

It will be remembered that Ross, in India, in his original investigations with
a malarial disease of sparrows, found that this was transmitted by Culex quin-
quefasciatus. There are malarial diseases of other birds, probably carried by
other mosquitoes. MacCallum’s original observation in which he discovered the
true meaning of the flagellate bodies, the real males of Proteosoma, was made
in studying a malarial disease of the American crow.

Captain James, who investigated the blood diseases of birds, states that “ the
voracity with which Culex mosquitoes (C. fatigans) [=C. quinquefasciatus]
will gorge themselves upon the blood of sparrows is extraordinary, and if too
many mosquitoes are put in the cage with the same sparrow they will literally
bleed it to death.”

Goeldi, in discussing the habits of Culex quinquefasciatus in comparison with
Aédes calopus, touches upon this adaptation as follows:

“ T have the impression that, in general, Culex fatigans behaves more contrary,
obstinate, timid, refractory to domestication and comprehension: I believe
that I can perceive significant proof of this in the singular circumstance that in
all the trials made with this species of mosquito I only succeeded in inducing a
single individual to bite, either among those captured or those bred in captivity.
I attribute to it a degree of intelligence decidedly inferior to that of Stegomyta
fasciata. This accords well with my idea that, in the same manner as the other
blood-sucking insects, this species of Culicid has a primary relation to a definite
and determinate species of vertebrate host. I feel induced to say that in Culex

fatigans we have a mosquito primitively less addicted to the human species than
to certain domestic animals, amongst which, my suspicion points principally

106
FOOD PREFERENCES 107

towards an inquiline of our poultry-houses. And may it not be possible that,
furthermore, in the marked intellectual diversity between Culex fatigans and
Stegomyia fasciata there is reflected the primitive diversity between their re-
spective hosts? It is certain, and no one will dispute me, that a mosquito must
be more expert to persecute man than to persecute poultry, cats or dogs, as the
case may be. And are not the rats and house mice, and, among insects, the re-
pulsive roaches proof how much effect the daily association with ‘homo sapiens’
has upon intellectual development and refinement? ”

Culex erythrothorax occurs in Californian swamps exclusively among the tall
reeds. Dyar found that “a person sitting on the bank was immune from their
attacks, but among the reeds they bit viciously in the daytime.” These reeds
were inhabited by numerous water-fowl and it is upon these that this species of
Culex, without a doubt, normally feeds. Pet caged birds, in regions of mosquito
abundance, are reared with difficulty, and young birds are often killed by mos-
quitoes.

There is reason to believe that many of the species of Aédes prefer mammalian
blood. The females of the species breeding upon the salt marshes of our coasts
migrate inland in large swarms and these journeys are very probably under-
taken in search of mammalian blood. The ferocity of the mosquitoes in northern
regions is remarked upon by all who have visited such regions. Linneus early
testified to it from his Lapland experience. Many other authors could be cited.
One of us (Knab) experienced it on the prairies of Saskatchewan.

In the opinion of Knab the blood-sucking instinct is so strong and so pre-
cisely adjusted to circumstances that it must be looked upon as a function of the
greatest importance to the mosquito. In the case of Aédes spencerii, the most
abundant species of the prairies of the northwest, Knab has observed that it has
the habit of flying towards prominent objects. Under natural conditions upon
the open prairies such prominent objects would always be some warm-blooded
animal and this habit demonstrates a very fine adjustment on the part of the
mosquito.

Some writers have held that but few of the mosquitoes which are so numerous
in far northern regions could obtain a meal of blood and therefore the blood-
sucking habit could not be considered normal or important in the economy of the
insect. This idea is based upon an erroneous conception of the fauna of these
regions. In fact the northern countries in former times teemed with warm-
blooded animals; it is only necessary to mention the great herds of bison, elk,
deer and antelope. Today, where the former inhabitants have disappeared
before the settler, they are replaced by horses and cattle, and there is sufficient
testimony as to how viciously these are attacked.

Galli-Valerio and Rochaz de Jongh, in their investigations upon European
mosquitoes, noted that certain mosquitoes showed a preference to animals over
man. One of them noted that in a locality in which he had always been bitten
by many Aédes nemorosus when there alone, when another person and a white
dog were also present these mosquitoes attacked and greatly worried the dog
while the persons sitting near were spared. This was the more remarkable as
the persons should have been preferred. on account of the dark color of their

clothing.
108 MOSQUITOES OF NORTH AMERICA

Some species, and among these may be counted many of those in temperate
and tropical regions, seem to have the appetite for blood but weakly developed.
Such species only bite occasionally and they have been observed sucking ripe
fruit, watermelons, and even boiled potatoes.

With reference to certain species the observations of different authors conflict.
According to most writers the European Culiseta annulatus does not bite.
Ficalbi states that he has never known this species to bite either man or animals
and he believes it to be phytophagous. Theobald states that in England it bites
in some localities but does not do so in others. We believe that these discrep-
ancies may be explained by differences in season and in temperature. It may be
stated in a general way, that mosquitoes increase their activity in ratio with the
rising temperature and increasing humidity of the atmosphere. During hiber-
nation they show little inclination to feed, even when the temperature is com-
paratively high. It should be noted that in certain European species of Culicide
which have long been associated with man, and the species just discussed is in-
cluded in these, the inclination to bite man seems to be weak at best. Perhaps
this can be explained in that the most blood-thirsty individuals would be the ones
to be destroyed ; thus, by a process of elimination, the least aggressive individuals
would be the ones to perpetuate the species and transmit this characteristic to
their offspring.

Cold-blooded vertebrates are also attacked. Brakeley, of New Jersey, has
seen a black terrapin surrounded by a swarm of mosquitoes, but she paid no
attention to them, possibly because she was engaged in egg-laying. It would be
an interesting observation to find whether the mosquitoes ever had an oppor-
tunity to pierce the terrapin eggs. Brakeley states that they also bite lizards,
snakes and frogs. Unfortunately we have no record of the species concerned.

There are several records that mosquitoes have been seen to puncture the heads
of young fish, but these observations apply to biting flies of another family,
namely, Simuliide. One of these observations was made by C. H. Murray in
the mountains of Colorado near the snow line. He found a small swarm of
“ mosquitoes ” circling about over a quiet shallow pool in a mountain stream ;
in this pool were very young trout and when these came to the surface of the
water they would be pounced upon by a “ mosquito ” and sucked to death. The
behavior of the insects, as described, suggests Simalium, as does the locality, and
it must be remembered that the observer was not an entomologist. P. Combes
gives an account of similar observations made in the island of Anticosti. He
calls the insects “ moustiques,” but from the detailed description of their habits
it is very clear that it was Simuliwm he had under observation. The confusion
has come about through the loose application of the popular term “ mosquito ”
or “ moustique.”

But blood-sucking mosquitoes are by no means absolutely confined to a verte-
brate diet. They attack other insects, particularly the soft-bodied ones, although
direct observations upon this point are rare. Veazie, of New Orleans, has seen
mosquitoes piercing a cicada, or “locust,” as it is incorrectly called in this
country, and also the soft-skinned pupa of the same insect. Hagen has recorded
FOOD OF MALES 109

an observation in the northwest United States in which he saw a mosquito en-
gaged in feeding on the chrysalis of a butterfly. Theobald has on two occasions
seen Culex nigritulus sucking at the body of Chironomus and other small
Diptera.

Male mosquitoes do not suck blood. In the chapter on the anatomy of the
mouth-parts we have shown that some of the mouth organs are absent or greatly
reduced in the male and on this account it is unable to pierce the skin. There
are, however, records by good observers of male mosquitoes sucking blood. One
of these is quoted herewith from Howard’s “ Mosquitoes ”:

“Tn spite of what we have just said about the non-penetrating mouth parts of
male mosquitoes, Dr. C. W. Stiles informs me that he and Hurst (the author of
an important paper on the pupal stage of Culex, Manchester, 1890) made an
observation in the summer of 1889, at Leipsic, which convinced him that either
the males do occasionally bite or that occasionally females possess feathered an-
tenne. Stiles and Hurst were out in a row-boat one evening and were bitten a
number of times by Culex nemoralis. One individual which bit Stiles on the left
hand was crushed, and in the crushing act a considerable quantity of blood
exuded—enough to make a fair-sized blood-stain on his skin. Upon examining
the dead body he was surprised to note that it possessed male antenne. Hurst
also examined it, and remarked that it was the first instance he had known where
a male Culex had actually been caught sucking blood. Dr. Stiles tells me that
Hurst intended to place the observation on record, but that he does not think it
was ever published. Dr. Stiles is so well known as an accurate observer, that
some other explanation than faulty observation must be offered in this instance.”

Ficalbi makes the following statement regarding Aédes calopus: “ A most
remarkable peculiarity of this species is that the male stings as well as the female
and sucks blood, producing a puncture equally painful with that produced by
the female.” The statement has been widely quoted but we have been unable to
find independent observations in confirmation of Ficalbi’s statement. In our
own wide experience with this species we have never known the male to bite nor,
of the numerous specimens handled by us, has there been any male with traces of
a blood-meal. W. Wesché, on account of the reports of the male biting, has ex-
amined the mouth-parts of several male Aédes calopus. He states that he
“ found very short atrophying maxille, no mandibles, a ciliated hypopharynx,
and the labrum and labium well developed,” a condition which does not support
the idea that the male bites.

There is still the possibility that the observations just quoted, of males suck-
ing blood, are based upon abnormal indviduals. Wesché found that aberrant
males occur in which the mouth-parts are fully developed. But one would still
have to assume that, along with the complete mouth-parts, such males had in-
herent the appetite for blood otherwise peculiar to the female.

It seems certain that the females of many species and of certain genera are
unable to pierce the skin of human beings and do not suck blood. The large and
brilliant mosquitoes of the genus Megarhinus do not suck blood. The pro-
boscis is so modified, the labium being entirely rigid, that they can not pierce
with it; recent observations show that both sexes are habitual flower-feeders.
Recently Mr. Edward Jacobson has discovered a mosquito, Harpagomyta
110 MOSQUITOES OF NORTH AMERICA

splendens de Meijere, in Java, which obtains its food by causing a certain ant,
Cremastogaster difformis Smith, to disgorge the liquid in its crop. This mos-
quito habitually sits upon the ant-streets on the tree trunks to waylay the ants.
The observer writes as follows:

“ They sit mostly immediately upon the ant-streets and constantly rock them-
selves back and forth, from left to right and the reverse.

“When now an ant comes down the tree and, so to speak, runs between the
legs of the mosquito, she is at once held up by the latter by rapidly tapping the
ant with fore legs and palpi, upon the head and vertex. Most of the ants then
immediately stand still, press the body firmly against the tree, fold the abdomen
towards the front and open the mandibles wide, at the same time drawing back
the antenne. The mosquito at once ceases its rocking movements and brings
the wings into rapid vibrations.

“While the ant now vomits a drop of food-liquid the mosquito licks it up with
great haste, upon which the ant goes on its way. The mosquito again begins to
tock itself back and forth until another ant allows itself to be robbed by the
waylayer.

“ However, not all ants permit themselves to be robbed and many hurry
rapidly upon their way without paying toll. The mosquito then often attempts
to bring the escaping ant to a standstill by flying down the tree in front of the
ant, at the same time constantly touching it with its fore legs and palpi.
Thereby she often accomplishes her object.”

The mosquitoes of the genus Deinocerites, which breed in crab-hoies along
the coast, are not blood-suckers. There are several species of Culex which are
exclusively crab-hole breeders and none of these appear to suck blood. We have
specimens of Culex extricator from Panama in which the abdomen is distended
by a whitish substance, showing that they had fed on something else than
vertebrate blood.

The little pitcher-plant mosquito, Wyeomyia smithti, does not suck blood.
Neither does Culex territans, a very common species throughout the summer in
eastern North America. Culex melanurus apparently does not bite. These
species probably obtain nourishment from plants in some form or other. Ob-
servations on the habits of such species are yet to be made.

Ficalbi discovered a species in Italy which punctures plants and feeds upon
their juices and which he therefore gave the name Culex phytophagus. In speci-
mens that had fed, the distended abdomen distinctly showed the green color of
the chlorophyll within. Theobald cites an observation by Dr. W. Hatchett Jack-
son that Culiseta annulatus apparently sometimes sucks plant juices. . . .
“on a warm sunny day in November the 9’s settled on the stems of periwinkle
and wall-flowers and inserting their proboscides, apparently engaged in sucking.”

The whole question of the feeding of mosquitoes upon plants has been rather
carefully gone over by one of us (Knab) in an article entitled “ Mosquitoes as
Flower Visitors,” published in the Journal of the New York Entomological
Society, Volume XV, December, 1907, pages 215-219. This article also in-
cludes certain original observations, and for convenience we reproduce it in full:

“Tn discussions of the feeding habits of mosquitoes one often finds the state-
ment that mosquitoes suck the juices of plants and visit flowers to obtain honey.
Generally, however, no details are given that would convince one that these
MOSQUITOES AND FLOWERS 111

statements are based upon actual observation. During the past season I found
a species of mosquito frequenting flowers in large numbers. It was obvious from
the behavior of these mosquitoes that the habit is quite normal with them. Con-
fident that the habit, of mosquitoes, of visiting flowers could not have altogether
escaped observation I made a hasty canvas of the available literature and brought
together the following records of a more definite character.

“Theobald states: ‘I have frequently seen Culicide settled on Composite,
sucking the juices of the flowers, both males and females.’ * According to Giles
‘they are frequently found on flowers, and especially in England on the catkins
of the willow.’ + Ficalbi found the first male of his Culex albopunctatus upon
a flower, sucking the honey, and upon searching the woods he found numbers of
males thus engaged upon flowers of the same kind.t{ A number of records
were traced through Knuth’s Handbuch der Bliitenbiologie. Hermann Miiller
has observed the male of Culex pipiens sucking on the flowers of Rhamnus
frangula.§ He has observed, in his room, this same species of mosquito effect-
ing the fertilization of Lopezia coronata by releasing the pollen and transmitting
it to the stigma of an older flower.|| Burkill, in observations on the flower-
visitors of Mentha aquatica, made at Scarborough between September 20 and
October 7, found an Anopheles species ‘ four times, seemingly sucking honey.’ {
The sex is not indicated.

“ The foregoing records are all European. Several American observers have
noted mosquitoes on flowers. Robertson, in a list of insects found on the flowers
of Ceanothus americanus between June 19 and 29, includes an undetermined
species of Culicide.** Smith has found the males of Aédes sollicitans ‘in great
numbers in wild cherry blossoms in the early evening, apparently busied in
getting at the nectar. Females have been observed at the same time; but ap-
parently these abandoned the vegetable food readily, when the animal odor
advised them of something more to their taste.’ ++ Dr. Graenicher lists Aédes
stimulans among the flower-visitors of Smilax herbacea and Smilax hispida.tt
No further data are given and upon inquiry Dr. Graenicher informed me that
he has no notes which would supply details regarding these observations. How-
ever he has very kindly furnished me the following interesting observations upon
Aédes sylvestris, recently made by him, which I give verbatim.

“¢ At the beginning of August, while collecting the visitors of our earliest
species of goldenrod, Solidago juncea, I came across a species of Culex on two
different occasions. Before writing to you on this subject I preferred to follow
up the matter more closely. Last Sunday [Sept. 1] the opportunity presented
itself, and I found Culex sylvestris Theo. (determined by Mr. C. T. Brues,
Public Museum of Milwaukee) on the flowers of the following three species of
Solidago: juncea Ait., canadensis L., and lanceolata L., (Huthamia gramini-
folia (L.) Nutt. in Britton’s Manual). This species of Culex is common in our
region, and it was well represented on the flowers throughout the afternoon, but
especially towards evening. Males and females were present, both eagerly suck-
ing nectar. By approaching them cautiously I was able to observe their actions

 

* Theobald, F. V.: Monogr. Culicidsx, vol. 1, 1901, p. 69.

+ Giles, G. M.: Handbook of Gnats or Mosquitoes, 2 ed., 1902, p. 114.

t Ficalbi, E.: Venti specie di zanzare (Culicide) italiane. Bull. Soc. Ent. Ital., vol. 31,
1899, pp. 107, 186.

§ Miiller, H.: Die Befruchtung der Blumen durch Insekten, 1873, p. 153.

L. c.. p. 198.

Lule J. C., and I. H. Burkill: Flowers and Insects in Great Britain, pt. 1, Annals of
Botany, vol. 9, 1895, p. 256.

** Robertson, C. H.: Flowers and Insects, III. Bot. Gazette, vol, 14, 1889, p. 304.

+t Howard. L. O.: Mosquitoes, 1902, p. 36, and Smith, J. B.: Report, mosquitoes of N. J.,
1904, pp. 27, 203.

tt Graenicher, S.: Flowers adapted to flesh-flies. Bull. Wis. Nat. Hist. Soc., vol. 1, no. 1,
1902, pp. 33, 34.
112 MOSQUITOES OF NORTH AMERICA

very distinctly with the aid of a lens. During the earlier part of the afternoon
the females (which by some are supposed to partake of animal juices only) were
present in greater numbers than the males, but later on both sexes were about
equally represented.’ ;

“My own observations were made last spring upon Aédes spenceri Theo.
during my stay in Saskatchewan. I shall give some particulars of the life his-
tory of this species as they throw some light on its feeding habits. This species
develops in immense numbers from the numerous ditches and temporary pools
of snow-water scattered over the prairie. The females are voracious blood-
suckers and in the early part of the summer make life on the prairie a torture
for man and beast. The species is strictly diurnal. The season was an unusually
late one this year, and the first mosquitoes were seen flying on May 30. The first
males were seen swarming on June 5. After several cold, damp days the mos-
quitoes were again active on June 9, the females biting, the males swarming.
The following day there was a very high wind which confined the mosquitoes to
their retreats in the grass. June 11 was a hot day with only light wind. On
an excursion into the prairie, early in the afternoon, the female mosquitoes were
found much fewer in number, perhaps as a result of the great heat. No males
were seen swarming, as had been the case on previous favorable days. However,
upon examining the willow bushes along the margins of ponds and ditches the
males were found in numbers upon the willow catkins. Often there were five or
six on one catkin, confining themselves to that part of it which was in full bloom.
They climbed about on the stamens and probed down amongst them to get the
honey. They appeared very eager in this work, plunging the proboscis down for
a second then quickly withdrawing it to reinsert it in another place, sometimes
even scrambling over each other in their eagerness. The palpi, together with an-
tenn, are held erect nearly at right angles to the proboscis. There were also a
few females at the willow catkins, feeding in the same manner as the males but
less eagerly. The following day, June 12, was warm but very windy. Along
the river bank the mosquitoes were again found abundant upon the willow
blooms, and this in spite of the high wind which must have made it very difficult
for them to maintain their position. As before, most of the mosquitoes on the
catkins were males. Although there was an abundance of flowers of various
kinds on the prairie at this time none of these were visited by the mosquitoes.
A period of continuous violent wind followed. When this had subsided the mos-
quitoes were again investigated on June 18. The males had now nearly all
disappeared ; there were none upon the willow catkins and only a very few could
be obtained by beating.

“Several points are brought out by these data. The life of the male mosquito
does not, at the most, extend over more than two weeks. The males do not
appear to take food until after the period of swarming or copulation, nor, in
spite of the food taken, do they survive long after the mating period. The
females probably only resort to flowers when very hungry and blood is not obtain-
able. It should be borne in mind that these deductions apply in particular to
Aédes spenceri. Now that we are more familiar with the habits of individual
species of mosquitoes it is obvious that no statements which apply generally can
be made from observations on the habits of one species. Thus, according to Dr.
Graenicher’s observations, the females of Aédes sylvestris visit flowers in equal
numbers with the males. This species, although a well-known blood-sucker, is
not so aggressive and persistent in its quest for blood as Aédes spenceri. More-
over it is crepuscular in habit and therefore most abundant on the flowers in the
evening, while Aédes spenceri frequents them during the day. édes sollicitans,
both sexes of which have been observed by Smith upon flowers, is noted as a most
persistent blood-sucker. In fact in all the species recorded in the foregoing as
FOOD DIFFERENCE OF SEXES 113

flower-visitors the females suck blood. In these hematophagous females the
nectar of flowers may be considered as a supplementary food which prevents
starvation when blood is not available. With the males nectar appears to be
the natural food. It is hardly to be supposed that species of mosquitoes limit
themselves to particular flowers, nor is there any structural modification that
would indicate adaptation to certain flowers, such as exist, for example, in the
flower-visiting Hymenoptera. The great diversity of flowers visited by mos-
quitoes bears this out. With the mosquitoes it is probably merely a question of
easy accessibility of the nectar and also of the season in which a particular
species of mosquito makes its appearance. As the appearance of many species of
mosquitoes is regulated by conditions of rainfall which vary from year to year,
the flowers available to a given species can not always be the same.

“. . . In conclusion I wish to place on record an observation on Megarhinus
septentrionalis D. & K., our largest mosquito. On July 14 of this year I found
a female of this species at Glen Carlyn, Virginia, probing for honey upon a cyme
of Hydrangea arborescens L. The mosquitoes of the genus Megarhinus are so
rare that very little is known of their habits, but it appears quite certain that
they do not attack animals, indeed, their proboscis is unfit for piercing the skin.
Probably they feed wholly upon the nectar of flowers, but as they are very rare,
even in their proper home—the tropics, and withal very shy, it is not strange
that they have escaped observation.”

It-is worthy of note that Réaumur fed Culex upon syrup and believed
that the greater part of them are contented with a diet of the sap of plants.
Mosquitoes have been observed to come to exposed honey in large numbers.

There is a decided difference in the food of the male and female of most
mosquitoes. Goeldi, referring to this difference, says:

“ A curious phenomenon is the difference in the methods of alimentation be-
tween the mosquitoes of the male and female sexes. The former out of doors
seek ripe fruit and flowers, and when they visit our houses frequent the sugar
basin, coffee, tea, wine, soups, the cups and saucers and plates of our tables—all
sweet substances in a word—abstaining as a rule from drinking blood. The
females, participating up to a certain point in this diet, are at the same time
addicted to the vice of blood-sucking. They are blood-suckers by choice, which
harms us, and it is chiefly against them that our hatred, the result of despera-
tion, is directed.”

Making experiments in this direction he found that out of thirty-seven mos-
quitoes captured in a sugar-bowl there were one female and one male of Aédes
calopus and two females and thirty-three males of Culex quinquefasciatus,
whereas, crushing, with one blow of his hand, a number of mosquitoes trying
to enter a mosquito bar, he found that he had killed twenty-three specimens of
Culex quinquefasciatus, all of which were females.

Goeldi also calls attention to the attraction which perspiration has for the
yellow-fever mosquito, both males and females, and shows that males often alight
upon the skin and drink the perspiration. He believes that the biting mosquitoes
were originally attracted by perspiration and that the females have developed
into blood-drinkers while the males have preserved the original condition. It
may be that the few reported cases in which males have been supposed to bite
are based upon a faulty deduction, males being seen in a biting position but
only drinking the perspiration and perhaps slightly irritating the skin.
114 MOSQUITOES OF NORTH AMERICA

Smith, in discussing the question of the food of adult mosquitoes, states that
he has examined the stomachs of a number of specimens, and has found some of
them filled with a colorless liquid like plant nectar. On the other hand, with
Aédes sollicitans, a salt marsh species, he has found the stomach filled by a mass
which he could not distinguish from thin marsh mud.

Some very interesting observations have been made upon biting of corpses by
mosquitoes. In our section on yellow fever we have given an account of experi-
ments made with captive Aédes calopus at Vera Cruz. In these it was shown
that one female feeding upon a corpse twelve hours after death apparently ob-
tained blood, but this was only one of a number; three of a number in another
case, one-half hour after the death of the patient, succeeded in feeding with
blood. Christy, in making a post-mortem examination in Nigeria, found a num-
ber of a large brown Anopheles feeding upon the body of a non-commissioned
officer who had died three and a half hours previously.

The laboratory studies consequent upon the discovery of the relations between
mosquitoes and certain diseases have brought about necessary experimentation
as to the kinds of food upon which to prolong the life of blood-sucking mos-
quitoes used for experimental purposes, and it has been found that they will live
almost for indefinite periods upon a vegetable diet, bananas, dates, raisin-grapes,
and other fruit used for this purpose, and it has been found that frequent meals
of water are necessitated in order to prolong life. One of us (Dyar) has reared
two successive generations of Aédes atropalpus in captivity by feeding the adults
upon sugar and water.

MOSQUITO SONGS AND THEIR POWER OF HEARING.

Probably owing to an association of ideas, the curious sound made by mos-
quitoes as they approach one’s ear is to most people extremely irritating. This
faint sound will waken many from the soundest sleep. It is not loud, and in
quality may perhaps best be compared to the distant note of a bagpipe.

As with flies and other dipterous insects the sounds emitted by mosquitoes
are not a true voice. It has been supposed that the sounds are produced in two
ways, by the vibration of the wings and by air forced through the thoracic
stigmata. Landois, in his classical paper on the sound-producing organs of
insects, apparently proved the latter to be the case, but more recent investiga-
tions show that he was at fault in his conclusion that the stigmata emit sound.

Landois thought that mosquitoes produce sounds in two ways. The normal
tone, which can not be modified in any way by the insect, is produced by the
wing stroke. The common Culex pipiens during flight produces the sound

= (d’). If one removes the wings, head, and all the legs of such a

mosquito she emits a sound which is much higher than that produced in flight.
This sound Landois thought to be produced by the stigmata of the thorax and
said it might be called the voice of the mosquito. He found within the spiracle,
a membrane, stretched like a double curtain, which he supposed produced the
sound when the air was forced through it. He considered the posterior thoracic
STRIDULATING ORGAN 115

spiracles those most concerned in sound production, but that the anterior ones
also took part. He found that the insect was able to modulate the sounds within
a considerable compass and he explained this by the fact that the spiracles are
under the control of muscles. By means of these muscles tension can be exerted
upon the chitinous ring of the spiracle and the position of the membranes
changed and this, Landois thought, modulated the sounds. Landois further con-
sidered that the halteres helped to control the sound from the metathoracic
spiracles,

Shipley and Wilson, in 1902, described a stridulating apparatus on the basal
part of the wings of Anopheles which is most probably the principal sound pro-
ducing organ. These authors call attention to the careful investigations of J.
Perez which prove, experimentally, that no sounds are produced by the stigmata.
Jousset de Bellesme reached the same conclusion and quite recently C. E. Pem-
berton has made experiments with confirmatory results. This last investigator,
like Nuttall, found that if in removing the wing a stump remained the insect
continued to emit a sound; if, however, the stump of the wing was entirely re-
moved, all perceptible sound ceased.

The apparatus described by Shipley and Wilson is very complex and lies
among the series of nervures and ridges on the narrowed basal portion of the
wing. It consists of two structures which rest against each other and are capa-
ble of a certain limited amount of movement. “ The anterior system consists of
a slightly movable bar, which covers a thickening in the tissue of the wing. This
last-named ultimately passes into the subcostal nervure. The bar extends from
the articulation of the wing to the humeral cross-nervure, and, as we have stated,
we consider it to be slightly movable. On its hinder, free edge the bar carries a
series of thirteen to fifteen well-marked teeth, which, under certain circum-
stances, rasp across a series of ridges borne on the second part of the system.”
This second part “consists primarily of a chitinous blade, shaped something
like a butcher’s knife, which is ridged on its upper surface with thirteen to fifteen
sharply-defined elevations placed slightly obliquely. It is against these ridges
that the teeth of the bar mentioned above rasp. The relative position of the bar
and the blade is not constant. The latter is usually lying partly under the
former, but at times it is free from it, and it seems as though it were hinged at
the handle and can oscillate through a few degrees, around an axis at the base
of the proximal end. But it can not rotate very far. A little way behind the
back of the blade is an upstanding flange of the membranous tissue of the wing,
which we have called the trough. This trough catches and holds the blade, and
prevents the latter being thrown too far back.” The authors then describe the
complex structures at the base of the wing which in their opinion constitute
part of the mechanism for producing sound by means of the above-described
organs. They further state that the area over which the blade travels is the only
part which “is quite smooth and entirely free from the minute hairs and
prominences which cover the rest of the wing.” These authors also found cer-
tain minute structures upon the halteres which they thought might be used to
produce a sound, although they consider that the principal function of the
halteres is one of balancing and orientation.

9
116 MOSQUITOES OF NORTH AMERICA

The exact musical note of the different species of mosquitoes seems to have
been investigated only in a few cases. Marked differences have been found in
the notes of different species. Both sexes emit a sound but there is a marked
difference, the note of the males being much higher than that of the female.
There is also a slight difference in the note of fed and unfed individuals of the
same species.

Landois found that in Culiseta annulatus the male range is through

f
— ; the female =.

Goeldi, in Brazil, has made an effort to determine the note of the yellow-fever
mosquito (Aédes calopus). It has several times been stated by observers that
this mosquito makes no sound when it flies, but this Goeldi denies. Aided by
two of his Museum colleagues who were musicians, he made his experiments as
follows :

“ For this purpose we made use of the inhabitants of two cages, one contain-
ing only males; the other only females. An hour of the afternoon was selected,
and the cages exposed to the mild rays of a partly cloudy day. We made use of
a zither and of a tuning fork of a known number of vibrations. We found that
the pitch of the female corresponded to C while that of the male corresponded to
A. The two sounds hold the relation of a sixth to each other; the A of the male
corresponds to 880 vibrations; the C of the female to 480 vibrations. In each
case we had the impression that along with the principal sound there was heard,
from time to time, the respective octaves so that the timbre seemed to be covered
by the proper concomitant sounds (‘ Oberténe’ in German technico-acoustic
language). It is evident that a certain effect is produced upon the pitch of the
sound by the greater or less dilation of the abdomen with food, and who knows
whether not also under the psychic effect of the influence of mutual suggestion.”

The musical note of Anopheles has been studied by Nuttall and Shipley and
their results will be found in our section on malaria in a later part of this
volume (p. 211).

The curious reaction of a swarm of mosquitoes to sound of a certain pitch
was related to Osten Sacken by a Cuban naturalist. While a swarm of mos-
quitoes was hovering over the head of the observer a band was playing at a dis-
tance. Whenever the note A was struck the mosquitoes were all precipitated
downward, striking against the face of the observer. The following observation
along the same line is from Howard’s “ Mosquitoes.”

“Mr. A. DeP. Weaver, an electrical engineer of Jackson, Miss., wrote me
that while engaged in some experiments in harmonic telegraphy, in which a
musical note of a certain pitch was produced by electrical means, he was amazed
to find that when the note was raised to a certain number of vibrations per
second, all mosquitoes, not only in the room where the apparatus was, but also
from other parts and from outside, would congregate near the apparatus and
would be precipitated from the air with astonishing force, striking their bodies
against the apparatus. He states that he therefore covered a large surface with
sticky fly-paper and after sounding the note for a few second captured all the
mosquitoes in the vicinity. He then devised an apparatus to electrocute them.
A section of wire window screen with the paint removed was mounted on a board
and small pins were driven between the meshes, the heads coming flush with the
ATTRACTION TO SOUNDS 117

surface of the screen. All the pins were connected together electrically, the
whole forming one electrode of the secondary coil of induction coil, while the
wire screen formed the other electrode. An alternating current of high potential
was then passed and when the note was sounded the insects precipitated them-
selves against the screen and were immediately electrocuted. Mr. Weaver, un-
fortunately, does not state whether males only were captured in this way.”

Nuttall and Shipley point out that Grassi (1900) states that persons are more
liable to be bitten by Anopheles when engaged in conversation than when silent,
and that Joly (1901) in Madagascar observed that mosquitoes were decidedly
affected by music and that if he played a stringed instrument the mosquitoes
began to fly about in the room and flew in from the outside, gathering about the
player in great numbers. They also state that Ross has been informed by Mr.
Brennen, of Jamaica, that he has seen mosquitoes there “ respond to such sounds
as a continuous whoop or hum,” stating further, “I have tried the experience
lately, and find swarms gather round my head when I make a continuous whoop.”

A very interesting instance of the attraction of mosquitoes to sounds of certain
pitch, as related in a letter to the London Times of October 29, 1901, by Sir
Hiram 8. Maxim, is published by Nuttall and Shipley :

“In 1878 I made and erected an apparatus for lighting the grounds of the
Grand Union Hotel at Saratoga Springs, New York, by electricity. The lamps
employed were rather large and each was provided with its own dynamo machine.
One of the lamps worked something like a telephone and gave a note the pitch
of which corresponded exactly with the strips on the commutator passing under
the brushes of the dynamo machine. Some of the other lamps would occasionally
give off a musical note, but only for a few minutes at a time. With this one,
however, the note was practically constant, and no adjustment of the carbons
had the least effect upon it. One evening whilst examining this lamp I found
that everything in the immediate vicinity was covered with small insects. They
did not appear to be attempting to get into the globe, but rather into the box that
was giving off the musical note. Upon a close examination of these insects I
found that they were all the same kind—viz., mosquitoes, and, what is more, all
male mosquitoes. Although there were certainly 200 times as many female mos-
quitoes on the grounds as males, I was unable to find a single female mosquito
that was attracted in the least by the sound. When the lamps were started in
the beginning of the evening every male mosquito would at once turn in the
direction of the lamp, and as it were face the music, and then fly off in the
direction from which the sound proceeded. It then occurred to me that the two
little feathers on the head of the male mosquito acted as ears, that they vibrated
in unison with the music of the lamp, and as the pitch of the note was almost
identical with the buzzing of the female mosquito the male took the music to be
the buzzing of the female. I am neither a naturalist nor an entomologist, still
I was much interested in this peculiar and interesting phenomenon. I wrote
down a full account of it at the time and sent it to a scientific paper, but it ap-
peared to be too stupid to find a place in that particular publication. However,
it now appears that others have stumbled across the same thing. A very interest-
ing experiment may be easily made in the following manner :—Obtaining a
tuning-fork which gives a musical note as much like the hum of the female mos-
quito as possible. If you strike this fork within 20 ft. of a male mosquito he
will at once turn about, face the music, and erect the two little feathers on his
head, something after the manner of a cockatoo.”
118 MOSQUITOES OF NORTH AMERICA

TIME OF ACTIVITY.

Mosquitoes are generally looked upon as nocturnal in habits but this is prob-
ably true of only a small number of species. . Our house mosquitoes of the genus
Culex are nocturnal. Culex quinquefasciatus, the house mosquito of the tropics,
is strictly nocturnal and bites in complete darkness. Many species of mosquitoes
are crepuscular, confining their activities to the twilight of evening and early
morning. This is the case with most Anopheles and the peculiarities of some of
the species, in this respect, are discussed in our chapter on malaria. The yellow-
fever mosquito (Aédes calopus) is strictly diurnal; its behavior is fully dis-
cussed in connection with yellow fever. In far northern regions the mosquitoes
are of necessity diurnal. One of us (Knab) found that the mosquitoes of the
Saskatchewan prairies are active throughout the day, during the hours of full
sunlight. At evening their attacks ceased, and indeed the rapid fall of tempera-
ture at that time puts an end to all insect activities. In the tropics, at least in
America, a large proportion of the species of mosquitoes are strictly diurnal.
It is true of many, if not all, the mosquitoes of the tribe Sabethini; they are
forest inhabitants and fly about during the hours of full sunshine. The large
and showy members of the genus Megarhinus appear to be diurnal. Lutz
states that the males of Megarhinus solstitialis are seen flying rapidly by day.
Knab has found a female of Megarhinus septentrionalis sucking honey from a
flower in broad daylight. It is probable that all brilliantly colored mosquitoes
are diurnal. The species of Aédes of our northern woods appear to be cre-
puscular. Yet, while they are normally quiescent during full daylight, they are
easily aroused. The presence of food, in the shape of a human being, will attract
them, apparently from a considerable distance, as one can ascertain by remain-
ing in one spot foratime. Aédes canadensis, Aédes stimulans and related forms
attack viciously during midday. Aédes atropalpus will bite by day and we have
known it to bite so late in the evening that it could no longer be seen. Knab
found that at Winnipeg Aédes riparius came to bite in numbers during the
middle of the day; it also bit at night in bright moonlight. Mansonia pertur-
bans is strictly crepuscular but in dark woods will attack in the daytime.

Different situations are sought out by the different species to pass the time of
quiescence. Certain species which have become more or less associated with man
seek shelter within houses or other structures. Certain species of Anopheles
frequent cellars, out-houses and culverts, and certain species of Culex are even
more domestic. The majority of the species of mosquitoes, however, are practi-
cally never found in houses. They hide in the woods, on the under side of leaves,
upon tree trunks, in hollow trees or under old logs. The prairie species hide in
the grass.

LONGEVITY.

The question is frequently asked, how long a mosquito lives; the adult form
alone being in mind. The males are very short-lived, in most cases probably a
matter of a few days only. Their only office is to fertilize the female and this is
usually very soon accomplished. Observations made by Knab in Saskatchewan
HIBERN ATION 119

upon édes spencerti, under unusually favorable conditions, indicate a length of
life of from two to three weeks for the males of that species. Indications are that
only a very few of the males live to the maximum of three weeks. It was possible
to gauge the length of life of these males thus accurately because this species has
but a single brood and all the adults issued within, at the most, a week.

The length of life of the female exceeds that of the male but differs with the
species and with circumstances. In temperate regions certain species hibernate
and these probably live longest as their activities are divided by an intervening
long period of quiescence. In these cases the length of the winter will determine
the longevity of the mosquito and we must look upon certain species of Culiseta
and Anopheles which occur far to the north as living longest.

There is a correlation between the habits of oviposition and length of life.
Members of the genera Culex, Culiseta, Lutzia and Uranotenia deposit all their
eggs at one time in a mass and death ensues immediately or soon after the eggs
are laid. The females of these genera may be said to be short-lived, the species
being perpetuated through a rapid succession of broods during the warm months.
In Aédes, where the eggs are deposited in small lots, at intervals, the female
lives much longer, in many cases several months. Accurate data can not often
be had on account of disturbing factors and we must rely largely upon our
general knowledge of the species. In a few cases, however, we have experimental
or other evidence which is conclusive. Aédes calopus has been a frequent subject
of experiment and females have been kept in captivity as long as 154 days, al-
though this appears to be far in excess of the normal span of life. Observations
by Knab, made in western Massachusetts in 1903, indicate that the females of
certain species of A édes live at least three months. He found that Aédes stimu-
lans, A. fitchii and A. abfitchit have but a single brood which develops early in
the spring. The data for the three species coincide so closely that they may be
considered together. The earliest capture (as appears from preserved speci-
mens) of a female was April 29; they continued abundant and troublesome
through May and June but showed some decrease during August. We have
specimens captured as late as September 12.

HIBERNATION AND /ESTIVATION.

With the majority of the species of mosquitoes the unfavorable season is
passed in the egg state. Certain genera, however, pass the winter, and in cer-
tain tropical regions the dry season, in the adult state. In such cases it is only
the female that survives, having been previously fertilized, to deposit her eggs
at the beginning of another season. Theobald states that the male of Culiseta
annulatus hibernates in England but this record stands quite alone. It is certain
that at least in the genera Culex and Anopheles no males survive the winter.
The hibernating females seek shelter with the approach of cold weather and at
this time they show no inclination to feed. Those species more or less associated
with man take advantage of the shelter of cellars, stables, sheds and other build-
ings, the darkest ones apparently being the most favored. They have also been
found hibernating in caves. Other species retire to hollows in trees, crevices in
120 MOSQUITOES OF NORTH AMERICA

the bark or other protected situations. There they remain quiescent until the
return of warm weather, closely hugging the surface upon which they rest.

Stephens and Christophers state that in India the Anopheles pass the season
of hot, dry weather in the houses. They found that while they feed regularly
they do not lay eggs even when breeding opportunities are present. The species
of Culex must also, in the absence of breeding-places, pass the dry season in
the adult state, although no exact data concerning them are available.

In temperate North America a few species pass the winter in the larval state.
Such is well known to be the case with Wyeomyia smithii. Larvee of all sizes are
overtaken by cold weather in their habitat, the water in the leaves of the pitcher
plant. They become enclosed in the solid ice and when liberated in the spring
continue development in the normal manner. This appears to be the only way in
which this species passes the winter and the hardiness of these larvee can be un-
derstood when one considers that the species occurs as far north as Minnesota
and Ontario. Culex melanurus hibernates in the larval state. The larve live in
spring-holes in marshes and remain at the bottom during cold weather. The
larva of Megarhinus septentrionalis, which normally lives in water in hollow
trees, hibernates, although, apparently, it will not survive freezing. It goes to
the bottom in cold weather and remains submerged. The larva of Bancroftia
signifer, which usually is found associated with Megarhinus, also hibernates.

In England and in the more southerly part of Europe, where the winters are
much less severe than in North America, one species of Anopheles (A. bifur-
catus) regularly hibernates as larva. The larve in various stages of develop-
ment have been found in the winter, living beneath the ice, by a number of ob-
servers, and these larve later produced imagos. In Switzerland, Galli-Vallerio
and his collaborators have made observations through about ten consecutive
winters that show that Anopheles bifurcatus and Culiseta annulatus regularly
hibernate there as larve.

The majority of the mosquitoes in temperate climates hibernate in the egg-
state and in far northern regions this is the only mode of hibernation. These
hibernating eggs hatch in the spring, in the water from the melting snow;
consequently these larve appear very early. Galli-Vallerio and Rochaz de
Jongh found that in Switzerland the hibernating eggs hatch during the winter
if pools are formed by rains or by a thaw. The larve survived under the sub-
sequently formed covering of ice and later produced imagos.

MATING-HABITS.

The mating-habits of a very limited number of species of mosquitoes are
known. From the observations at hand it is evident that there is considerable
diversity and it must be pointed out that for one large group, the Sabethini, we
have no records whatever. With many species the males “ swarm,” that is, they
gather and hover in the form of a cloud, to which, it seems, the females are
attracted. In some cases there are two swarms or clouds, one of males the other
of females. There are species, it seems, that do not swarm and others have the
habit but weakly developed.
MATING HABITS 121

The attitude assumed during the copulatory act differs according to the struc-
ture of the claws of the female. In the forms with simple claws (Culex, Anoph-
eles) the position is end to end, the pair facing in opposite directions. The forms
in which the female claws are toothed copulate face to face, clasping each other
with their claws. The first exact observation of the mating habits of mos-
quitoes was based on such a species (Aédes calopus) and to this may be traced
the repeated statement that mosquitoes all copulate in this way. This early
account, by Godeheu de Riville, will be found abstracted in the chapter on the
yellow-fever mosquito (p. 276).

One of us (Knab) has published his observations on the mating-habits of mos-
quitoes in a series of papers which are brought together here. The first is on
the swarming of Culex pipiens (Psyche, October, 1906, pp. 123-133), and is
based on observations made by himself in Illinois, and in it he includes accounts
of many former observations. The general question of swarming and mating
as considered in this article is herewith largely quoted from:

Tt has been the writer’s good fortune to observe the swarming and mating of
Culex pipiens upon four consecutive evenings, October 15-18, 1904. Many
notices of the swarming of Culicide and related forms have appeared, but most
of the accounts deal with the swarming simply as a remarkable phenomenon
while its significance escaped them. It therefore seems worth while to record
my own observations. Following these I shall give the more interesting data of
previous writers, and at the end, a bibliography of the subject.

“ My observations were made at Urbana, Illinois, under exceptionally favor-
able conditions. Although the country about Urbana is well drained and there
is but little water, mosquitoes were remarkably abundant. As far as could be
determined all came from one source. On the outskirts of the town is a small
stream, known as the Salt Fork, which, during dry weather, becomes practically
stagnant. About a mile up the stream the water was polluted by the discharge
from an abattoir. The foulness of the water was such that the fish normally
present in the stream were all destroyed and thus an ideal breeding-place for
mosquitoes was created. Early in October the writer found the larve of Culex
pipiens present in immense numbers, and when the shrubbery bordering the
stream was disturbed the imagos rose in great clouds. These mosquitoes, how-
ever, showed no inclination to leave the water-side and would quickly return to
the shelter of the marginal vegetation.

“ October 15 was a warm autumn day and its close was marked by one of
those clear calm evenings when not a leaf stirs and the air appears to be perfectly
still, At five o’clock the writer was crossing a corn-field not far from the stream.
The sun was already near the horizon and its direct rays were cut off by an in-
tervening line of tall trees. When near the middle of the field a cloud of mos-
quitoes was noticed directly overhead. The lowest mosquitoes were about the
writer’s head and shoulders, the topmost ones perhaps five feet higher; the
transverse diameter of the swarm was about two feet. The high-keyed piping,
vibrating between two notes in constant rapid reiteration, was very distinct.
The variations in tone seemed to correspond to the upward and downward move-
ments of the individuals. In the light of the succeeding observations it would
seem that this swarm had been forming above the writer’s head from the time he
entered the field. The swarm was watched for about twenty minutes. The
individuals in the swarm flew up and down amongst each other with a kind of
weaving motion—a downward and forward plunge and back again, performed
without unison or regularity. The movements were sufficiently slow to allow
122 MOSQUITOES OF NORTH AMERICA

the plumed antenne of the males to be clearly distinguished and it appeared that
the swarm was composed wholly of males. Once a female was seen to dash into
the midst of the swarm and emerge on the other side united with a male. The
insect-net was swept through the swarm a number of times. At each stroke the
mosquitoes would disperse somewhat but returned at once to their former posi-
tion and continued their dance, and there was no perceptible diminution of their
numbers. An examination of the captures showed 897 males and four females.
This count includes the female observed passing through the swarm, as narrated
above, and it is obvious that the other three females in the capture are not to be
considered as members of the swarm. They may have entered the swarm un-
noticed in the manner described, or they may even have been hovering about out-
side of it. The observations of T. H. Taylor (in Miall & Hammond, The Harle-
quin Fly) show a like condition in Chironomus. On a still evening his captures
from a swarm were 700 males, no females. Ona windy evening, when the swarm
was thrown more or less into disorder by the breeze, a capture of 4300 specimens
included 22 females.

“ Upon turning to leave the mosquito-swarm another one was discovered close
by, hovering over and about a corn-stoock. The swarm extended about half way
down the side of the stook and kept on the south side of it, the mosquitoes all
facing northward. Although there was no perceptible breeze it was thought
that the attitude of the mosquitoes was in response to a current of air and sub-
sequent observations confirmed this supposition. It was but seldom that one of
the mosquitoes alighted on the corn, and as in the cloud first observed, all ap-
peared to be males. A round of the field showed that each corn-stook had its
swarm of mosquitoes, and furthermore, single stalks that remained standing
had small swarms dancing over them—sometimes of only six or eight individuals
—and the bushes and small trees on the edge of the field had their swarms. In
every case the mosquitoes faced northward and the swarm kept on the south
side of the object of attraction. Always the mosquitoes gathered over some
promiment object such as a tree or a projecting branch, a bush, a corn-stook or a
person. In this last case the swarm would move with the person and the only
way to get rid of it was by passing under some taller object where the swarm
would then remain.

“On the following evening at five o’clock the field was again visited. Upon
approaching the region of the creek swarms of mosquitoes were noted over every
tall object—at the tops of telephone-poles, orchard-trees and shrubbery. Ona
very tall elm, standing alone in a pasture, a swarm was dancing before a project-
ing branch. In the corn-field the swarms were found, as on the evening before,
over every prominent object and as the writer entered the field a swarm im-
mediately began to form over his head. This time, however, the position of the
swarms in relation to the objects was the opposite of the evening before—the
mosquitoes were now all facing southward and they kept on the north side of the
objects. The trees on the south side of the field, some of them 25 or 30 feet high,
had immense clouds on their north sides. As on the evening before, there was
no perceptible breeze but the drift of smoke showed that there was a current of
air from the south. Station was taken near the row of trees bordering the field
and some swarms dancing before projecting limbs kept under observation. Re-
peatedly females were seen to issue from the foliage, dash into the swarm, and
emerge united with a male. When in copula the male and female face in oppo-
site directions, their bodies in a horizontal plane; the female dragging the male
after her.* The pair (or rather the female) would fly upward for a while and

 

** Goeld! (Os mosquitos no Parfi, 1905, p. 74, [: i fig. 83a) describes and figures the copula-
¢€

tion of Stcgomyia calopus. In that species the ma ngs to the under side of the female.”
SWARMING OF MALES 123

then slowly drift towards the ground. Once a pair in copula was seen to issue
from one swarm and plunge into another swarm close by. The pair made great
haste to extricate itself while the swarm was immediately thrown into frantic
excitement and the mosquitoes danced up and down at a furious pace for some
time, until at last the ordinary measure of speed was regained. With the grow-
ing darkness the excitement in the swarms increased and the movements became
more rapid. Few successful unions now took place. Females entering the
swarm would be pounced upon by two or three males, and together, tumbling
over each other, they would fall to the ground and there separate. Towards the
last no more females appeared and with the increasing darkness the swarms
rapidly diminished, the males flying off into the air.

“ At 5 o’clock on the following evening the swarms were found as before,
dancing over every object projecting above the general level. Single mosquitoes
were seen flying rapidly and straight. These looked larger than the dancing
males and when captured proved to be females. The air was again very still
with a current from the south and, as before, the dancing males faced towards it
and kept on the opposite side of the objects. The west side of the field was
bounded by tall trees and high up on these, at least fifty feet from the ground,
before projecting branches, clouds of mosquitoes could be distinguished while
lower down on these trees there were none. Station was taken at a corn-stook to
determine how long the dance would continue. As the darkness grew the num-
bers began to diminish, and at 5.50, when the darkness was almost complete, the
last male flew away. The departing males flew upward and none of them
alighted on the stoock.

“On the fourth evening the field was visited nearly an hour earlier than be-
fore. The sun was still shining and there were no mosquitoes present. Later,
when the sun had disappeared behind the trees, the swarms were again present
just as on the previous evenings. On this evening, however, there was quite a
breeze blowing and the mosquitoes could not maintain their position over the
projecting objects and swarmed altogether on the leeward side of them. Other-
wise their behavior was much the same, only that the freshening wind occasion-
ally threw the swarms into confusion and greater activity. Rain and cold
weather followed the next day and put an end to further observations and pre-
sumably to the swarming.

“There are many records of swarms of Culicide and related forms, although
in many cases there is no exact indication of the identity of the insects in ques-
tion. I am convinced that all such records, in so far as they refer to swarms of
the nature described above, apply to Nemocera and probably in every case either
to Culicidee or Chironomide. I believe that these swarms of dancing males,
congregated for sexual intercourse, are peculiar to the Nemocera. Many of the
records from untrained observers, called forth by the appearance of these
Diptera in extraordinary numbers, though incomplete, are nevertheless of in-
terest. In nearly all of them the fact that the swarming leads to sexual union
has been entirely overlooked.

“ Moufet, in 1634, already speaks of these swarms and notes how they gather
at the gables of houses and over the heads of people passing over bridges. It
should be noted that in his chapter ‘De Culicidum’ the Culicids and Chiro-
nomide are not distinguished, as indeed has been the case with many a writer
since.

“The oldest record of the copulation of Culex appears to be that of the
Spaniard Diego Reviglias, communicated to the Leopold-Carolinian Academy in
a letter dated 4 March, 1728, but not published until 1737. Reviglias observed
under the microscope, and described at considerable length, the sexual union
and the copulatory apparatus of the mosquito. He treats his discovery as a very
124 MOSQUITOES OF NORTH AMERICA

important one, which indeed it was in those days of lingering belief in spon-
taneous generation. However he does not mention swarming and there is reason
to believe that he had before him a species which does not swarm—a matter
which I shall take up again farther on. Later the French commander Godeheu
de Riville also claimed as the first his observation of the copulation of mosqui-
toes, made on board his ship. The account is quite detailed and it is evident
that in this case likewise copulation took place without swarming.
* * * * * * * *

“ There are a number of accounts of such swarms about church steeples caus-
ing alarm of fire. We have them from Germar (1813), Boll, Kirby and Spence,
and Hagen. Boll records three such swarms. One of them on the steeple of
the Nicolai church in Hamburg took place on a June evening at nine o’clock.
The discovery of the true nature of the apparent smoke, after the fire-department
had been called to the spot, caused great merriment in the crowd of spectators.
In 1807, when the St. Mary’s church in Neubrandenburg served as a powder
magazine, the sudden news that the steeple was on fire caused many of the in-
habitants to flee precipitately from the city. As the column of smoke about the
steeple did not increase, some courageous men finally ventured onto the tower
and discovered that the source of alarm was an immense swarm of gnats. An-
other swarm was observed about the cross of this same church-steeple, at a height
of 300 feet, on the afternoon of August 20, 1859. Hagen relates that dense
swarms of gnats about the church-steeple at Fischhausen caused an alarm of
fire which has earned for the inhabitants the nickname of ‘ Miickenpeitscher.’
Koch has reported a swarm from the wings of a windmill, at a height of perhaps
a hundred feet from the ground, curled by the breeze and resembling smoke.

“ Haliday states that Culex detritus * occurs at Holywood, County Down, ‘in
multitudes, during the day among hedges on the seacoast, in the evening in
columns about the tops of trees, appearing like smoke at the distance of a fur-
long.’ Weyenbergh records two swarms of Culex pipiens from the vicinity of
Haarlem, observed in 1857, dancing in perpendicular columns.

“ Mott gives an interesting account of an unusual gathering of gnats observed
by him in 1879. As the article is not generally accessible and describes well the
phenomenon, I quote it nearly in full. ‘On the evening of September 1st, be-
tween six and seven, after a fine, sunny day, the sky being clear, and the full
moon just rising as the sun went down there was a grand festival among the
gnats. Above the tops of the trees and hedge-rows in the low meadows north of
Leicester these little Diptera were out in immense numbers. . . . They as-
sembled in groups of various shapes, sometimes a vertical column from 6 ft. to
20 ft. high, and 1 ft. to 3 ft. diameter, rose from a tree top like a pillar of smoke.
Sometimes a sheet 4 ft. or 5 ft. high and 10 ft. long hung above the hedgerow,
but seemed never more than a foot or so in thickness. The following evening,
at the same hour, the sky being more clouded, a few gnats only were to be seen;
but on the evening of the 6th, with the sky again cloudy, there was a still more
remarkable display of gnat life. The little creatures were out again in millions,
but this time the vertical column formation was adopted by nearly the whole of
them. These columns rose from the hedges on either side of the road, and were
visible for half a mile ahead at irregular distances, averaging, perhaps, 21 ft. or
15 ft. They formed an avenue of such a singular and unusual appearance that
everyone who passed along the road paused at intervals to watch and wonder
at them. This piece of road is about half a mile long, on the top of an embank-
ment which carries it over the low meadows and the river. At the farther end

 

*“ Haliday’s Oulew detritus greatly resembles the comm
the observation should be credited to the latter species.” PE nee Siete Sn ine praeaay
POSITION OF SWARMS 125

there are a number of trees, and from the top of nearly every tree three or four
of the strange, smokelike columns could be seen standing up in the air, always
straight but not always vertical, some of them being inclined at small angles.
. . . On watching one of the columns closely, it was apparent that all the gnats
had their heads one way, facing the breeze, which, however, was a very light one.
It was a calm evening; what air-current there was came from the south-east.
It seemed to be sufficient occasionally to press back the column a few inches
from its normal position, and whenever this happened the whole body of gnats
jerked themselves forward again with one perfectly synchronous impulse.’

“ A picturesque account of a remarkable swarming of Culices, at Lewisham
Road near London, is given by Douglas. During ten days he observed ‘ the air
thick with millions of them, at times charging in close column up the road, like
a squadron of cavalry, at other times engaged in dancing up and down, after the
manner of their race.’ These swarms were in evidence only during the hour
before dark and it appears were over or near the road, within reach of the
riding whips and sticks of the ‘ profanum vulgqus.’ Near by ‘are several tall
trees, and round the top of the highest one only, at the same hour of the evening
that the periodical saltatory performances are going on in the road, enormous
swarms of gnats congregate. At first they appear as a small black cloud curling
about the ends of the branches, and soon, when the air is calm, rising in a close
column, like smoke from a chimney, for a distance of some 20 or 30 feet, the
bulk gradually becoming more grey and attenuated until lost to sight in the
upward progress. When a breeze is moving, the insects, always preserving close
order, are blown out laterally, and after skirmishing with the wind return to
their cover among the top leaves of the tree.” This last remark may be an as-
sumption and at such distance from the ground could hardly have been based
upon actual observation. Douglas suspects that the species in the tree was ‘ not
the same as that of the acrobats of the road, and with right; unfortunately
neither form was definitely identified. It further appears from the remarks of
Douglas that these swarms are an annual occurrence, only that the number of
individuals varies greatly from year to year.

“Tn all the foregoing notes the writers failed to notice the true function of
these gatherings of Nemocera. However it had not escaped that keen observer
Gilbert White. He was evidently uncertain of the identity of the insects con-
cerned, for in his posthumously published notes he calls them ‘empedes or
tipule.’ Speaking of their swarms at evening he says: ‘ At this juncture they
sport and copulate ; as it grows more dark they retire. All day they hide in the
hedges. As they rise in a cloud they appear like smoke.’ No further mention
of copulation in connection with swarming appears until Taschenberg’s popular
account of Culex pipiens, published in 1882. He notes their habit of gathering
at the gables of houses and other prominences and describes how the females fly
to the swarm of males to effect copulation. In the notes on the swarming of
Chironomide which follow, Taschenberg describes the formation over trees and
in tall columns, and we are left to infer that the Culex swarms do not assume the
columnar form—at least not in the same degree.

* * * * * % * Eo

“ Radl has written two most interesting and suggestive papers on the light-
reactions of Arthropods and a great part of his discussion is based on the be-
havior of swarming insects, particularly of Culicids and Chironomids. It
would lead too far to enter into a discussion of these papers, but the fact is
brought out that these insects orient themselves towards some definite object
which is differentiated from its surroundings either by greater prominence or a
difference in color. He not only cites instances of orientation towards trees,
126 MOSQUITOES OF NORTH AMERICA

bushes, sign-posts, or even heads of grass, but others where the swarms hovered
over paths through fields, or spots of different color but not elevated above the
surroundings. The swarms over spots on the ground in all probability belong
to different species from those attracted to prominent objects. Radl confesses
that he made no attempt at close determination of the insects under observation
and it is evident that he had no conception of the number of forms of similar but
distinct habits that he might have before him. In consequence his statements
are far too general and much that might have been used for or against his con-
tention has escaped him.

“Little as we yet know of the subject, it will be well to state right here that,
even within the Culicide, there is not only a marked diversity in the mode of
swarming of different species, but that there are many forms which do not
swarm atall. In the case of the almost exclusively house-inhabiting Stegomyia
calopus, as Goeldi has shown, there are no such swarms as in Culex proper. The
males congregate in little groups of 15 or 20, hovering over the corner of a
cabinet or other prominent object, and pounce upon the females that come within
range. I can add that copulation frequently takes place when there is no evi-
dence of even such weak swarms. It should be noted that in Stegomyia copula-
tion takes place during the brightest part of the day. On the other hand I have
upon two occasions observed small swarms of Stegomyia (presumably males)
hovering over the heads of persons, in both cases shortly before sunset. Once
this occurred upon the hotel veranda at Cordoba, Mexico, and again in the street
at Acapulco, over the heads of passers and keeping along with them. In this
case the meaning of the swarms would be hard to interpret.

“ Upon a recent trip to the west coast Dr. H. G. Dyar found a pair of Culiseta
consobrinus * in copula, resting on the under side of a board. This observation
shows a wide departure from the short copulatory act of Culex and Stegomyia.

“The crab-hole inhabiting Deinocerites cancer swarms during the short twi-
light period just outside the crab-holes and copulation takes place then.

“ Goeldi has given a vivid account of the swarming of the common house-
mosquito of Para which he designates as Culex fatigans.t Swarming takes place
indoors when it is nearly or quite dark and there are separate swarms of males
and of females. Such peculiar mating-habits surely indicate a distinct species.
In the case of our Culex pipiens the males are never found in houses—unless,
indeed, they happen to come from larve developed indoors.

“My. E. A. Schwarz has kindly placed at my disposal his observations made
on a species of Culex, probably the Culex cubensis of Bigot,t at Cayamas in
Cuba. The swarming occurred in the house, always on the side away from the
sun, and when it was almost fully dark. The mosquitoes could only be seen
against the sky, when between the observer and the open doors and windows and
close observation was impossible under the circumstances. However, the swarms
in this case were made up of both sexes and copulation freely took place. A cap-
ture of 60 specimens from such a swarm contains 44 males and 16 females.”

In a later paper entitled “The Swarming of Anopheles punctipennis Say ”
(Psyche, February, 1907), Knab published some novel observations on the
swarming of the species mentioned. This is quoted:

“Upon October 7 and 14 the writer observed the mating habits of Anopheles
punctipennis and as, up to the present, nothing appears to have been made known

 

*= Ouliseta inornatus,
a eee. quinquefasciatus, The passage will be found in translation in the systematic part
t The specimens on which the observation was made have since been identified as Culex
quinquefasctatus.
SWARMING OF ANOPHELES 127

regarding the mating habits in the genus Anopheles, the following notes are
offered. Much to his surprise the writer found that the males of Anopheles
ole as do those of Culex, although the behavior in the two forms is quite dif-
erent.

“The observations were made on Plummers Island (Maryland) in the
Potomac River, about ten miles above Washington. Near the highest part of
the island is a ledge of rock forming an open space surrounded by the woods on
three sides. The side towards the river is open, save for a couple of small trees
at the edge, and terminates in a nearly perpendicular cliff. On October 7,
shortly before 5 o’clock, the writer visited the spot to enjoy the sun-set. The
ledge is about sixty feet above the water and on its highest part, where some tufts
of tall grass grow in a crevice of the rock, was a swarm of dancing Diptera. The
swarm was directly over the tufts of grass, its base seven or eight feet from the
ground, the apex five or six feet higher. Although in appearance and action
quite unlike Culex pipiens (observed on previous occasions) they were recognized
as mosquitoes by the prominent palpi and the plumed antennz. With a sweep
of the net fifteen were secured and proved to be males of Anopheles punctipennis.
Their appearance in flight differed from pipiens mainly by the position of the
legs which were held straight behind and close together. The palpi and antenna,
directed straight forward, also appeared much more prominent than in pipiens,
which, together with the much longer legs, extending out behind, gave them a
very characteristic appearance.

“ Tn their actions, too, they differed markedly from pipiens. The swarm was
small, composed of less than a hundred individuals, and was not as compact as
the swarms of pipiens. The movements of these males were far more free and
varied than those of pipiens which constantly repeat the same circumscribed
movements. The Anopheles flew about in the swarm in a circling upward or
downward ‘ corkscrew ’ course. Their movements were more rapid than those of
pipiens and often irregular; single individuals would at times leave the swarm,
and cutting a wide circle, return into it. Sometimes these stray individuals
would fly for a short distance with a peculiar rapid zig zag motion—a series of
short sidewise jerks—and then return with the ordinary steady flight. In spite
of these varied evolutions the mosquitoes showed a tendency to face in one
direction, presumably towards the wind, although the evening was perfectly calm
and there was no breeze apparent. As it began to darken the males began to
leave the swarm one by one, flying upward, either into surrounding trees or more
often they would disappear into the sky. On this evening copulation was not
observed and from the following observations it may be assumed that union only
takes place during the early part of the swarming.

“ Although stormy and cold weather intervened, the following Sunday proved
fine and the ledge on the island was again visited. Shortly before 5 o’clock,
with the sun still shining but near the horizon, a few males were found already
assembled and engaged in their circling flight above the grass-tufts. Others
came from different directions and joined the swarm and by sunset it consisted
of perhaps sixty or seventy mosquitoes. It was difficult to follow the movements
of single mosquitoes but it seemed that in circling about they described a figure-
of-eight—sometimes on a plane, or ascending and descending. At 5.15 a pair
was seen falling out of the middle of the swarm, grappling each other as they
fell. They had not dropped far below the swarm when union was effected, and,
swinging out in opposite directions, still united they drifted slowly away towards
the ground. Within ten minutes six pairs were seen to drop out of the swarm
and copulate in this manner but after that no more. Three of the pairs were
captured in the net; one pair tested in the bottom of the net about a minute,
then separated and flew out; the other two pairs remained united even after
128 MOSQUITOES OF NORTH AMERICA

death in the killing-bottle. It could not be determined if in the slow flight of
the united pair the female leads off as is the case with pipiens, but it is to be
presumed so, as she is the larger. Neither could it be positively ascertained
whether any females formed part of the swarm. None were seen to enter at the
time copulation took place, but with the rapid and confused movements of the
members of the swarm (some flying out of the swarm and back again, as de-
scribed above) it was impossible to keep all the individuals under close observa-
tion. However it is safe to conclude that, as in pipiens, the swarm proper con-
sists wholly of males—certainly the fifteen specimens captured out of the swarm
on Oct. 7 were all males. If there is any choice made in the selection of a mate
it must be on the part of the female, for there appears to be no effort made, or
any struggle, on the part of the males to secure the female entering the swarm.

“ An interesting fact was the prompt reaction of the entire swarm to sound.
The sound of the voice in conversation would, at the first shock, precipitate the
entire swarm about a foot, and the mosquitoes would continue in rapid and con-
fused movement while the speaking continued. This effect could be noticed even
when one spoke in quite a low voice, and a pistol-shot, perhaps half a mile off,
precipitated the swarm in the same manner. When silence was restored the
swarm immediately resumed its normal flight. The experiment was repeated
many times and each time the effect was instantaneous.

“ At about 5.30 the swarm began to diminish, the males flying off singly into
the air. Very often a male would start off with a hesitating flight, and after
flying some distance and hovering about as if reluctant to leave, would again
return into the swarm. At last the swarm was reduced to three males which re-
mained for some time, and at the last a single male remained, continuing his evo-
lutions alone for fully three minutes, when, at 5.45, he too flew off.

“ A curious circumstance was the presence, on both occasions, of a swarm of
minute Chironomide in close proximity to the swarm of Anopheles. Mr. D. W.
Coquillett kindly determined these as Ablabesmyia pilosella Loew. While these
did not mingle with the swarm of Anopheles they were as close as they could be
without interference. Apparently the spot which the Anopheles had fixed upon
had the same attraction for them. This swarm seemed likewise to be composed
wholly of males.

“Tt seems remarkable that the attitude taken by Anopheles in copulation,
end to end and facing in opposite directions, is identical with that of Culex
pipiens. This remarkable agreement is significant when the structure of the
tarsal claws is considered. In both forms it is practically the same and all the
claws of the female are simple. In both cases the legs are not made use of in
the copulatory act itself but only in the preliminary scuffle. Dr. H. G. Dyar has
found that Culiseta consobrinus,* another form with simple claws and quite a
distinct generic type, takes the same position in copulation. It is fair to
assume that this is the mode of copulation in all the forms in which the female
has simple claws. On the other hand it appears that in those forms in which
the female has toothed claws the position in copulation is face to face, the pair
clasping each other. The writer can confirm Goeldi’s observation that Stegomyia
calopus copulates in this manner. Dr. Dyar has observed the same method of
copulation in Aédes varipalpus Coq. One can not avoid the inference that the
difference in the structure of the claws is closely correlated with the mode of
copulation. .. .”

Since the publication of the above article we have found that Curtis, in,his
British Entomology, vol. 5, no. 210, quotes the observations of Haliday on the

 

*= Ouliseta inornatus Will.
SWARMS OF MALES 129

mating-habits of two European species of Anopheles. Of Anopheles bifurcatus
it is said that “ the males hover in small flights about the skirts of groves near
rivulets in the still evenings of June,” and of Anopheles maculipennis, “ these

also fly in small swarms in the evenings of June, when I have taken them paired
in the air.”

In their “ Report of the malaria expedition to Nigeria” Annett, Dutton and
Elliott give a short note on the swarming of male Anopheles in west Africa.

_ “But after sunset, clouds of mosquitoes were often observed flying and hover-
ing in characteristic flocks in the neighborhood of native huts, about eight feet

above the ground. On capturing and examining many of these, all were found to
be Anopheles males.”

F. C. Willcocks has recently published observations, made in Egypt, in the
vicinity of Cairo, on the mating-habits of several species of mosquitoes. He
points out the difference in behavior of the different species in an interesting
manner.

“The aerial dances performed by male mosquitoes at sunset are perhaps
worthy of note. The males of Culex, spp. dance in columnar form, well in the
open, or in some cases, near or above bushes, and from fifteen to twenty feet from
the ground. Thousands of individuals may be present in one of these dances,
all in extremely rapid movements of limited range. They produce a very
audible hum. The males of Cellia [=Anopheles] pharoensis dance as a rule
in the open, but much nearer to the ground than Culex, nor do they collect to-
gether in such large numbers. Their flight is also much slower. The aerial
dances of the males of Grabhamia [=Aédes] willcocksii are again different.
They appear almost invariably to take place close to bushes, under trees or sheds ;
the males fly backwards and forwards with a slow and easy flight, about three
feet from the ground, columns not being formed. One rather striking fact con-
cerning these aerial dances is the comparatively small numbers of females which
join them in order to pair with the males.”

An overlooked paper by Wahlberg, published in 1848 (Ofversigt Kongl.
Vetenskaps-Akad. Forhandl., v. 4, p. 257) describes the mating-habits of far
northern mosquitoes, undoubtedly belonging to the genus Aédes, as follows:

“Tt has been noted as strange, that the males of mosquitoes (Culex) are only
found in very small numbers in the extensive moors of the far north, where the
bloodsucking females surround and attack the traveller in numberless swarms.

“ Rev. Lestadius of Karesuando has informed me that these males are often
found on the surface of the lakes, beaten down by rain or wind, in such endless
numbers, that, when blown ashore, they form thick windrows.

“One wonders then why they are not observed more commonly together with
the females.

“T have recently had opportunity to convince myself of the reason for this,
during my stay at the ‘Great Oive’ mountain. On the top of this mountain we
were surrounded and pestered by female mosquitoes in great numbers, but not
a single male was observed until I became aware of a loud singing noise, which
on investigation was found to be produced by immense swarms of mosquitoes
high up in the air, dancing in separate flocks.

“On examination these swarms were found to consist nearly exclusively of
males.

“ This indicates that the males of the Culez—like those of Chironomids and
some other non-biting gnats—keep to themselves in a higher stratum of the air,
130 MOSQUITOES OF NORTH AMERICA

where they, especially towards evening, flock together in dancing swarms and
tempt the females to come up by the noise of their wing-beats.

“When a female comes up into this dancing cloud it is chosen by a male and
the two separate themselves from the rest, while the male swarm continues the
dancing with uninterrupted music at varying heights in the air.”

The swarming of Aédes spencerit has also been observed by Knab, on the Sas-
katchewan prairies. This is described in Smithsonian Miscellaneous Collec-
tions, volume 50, part 4, pages 542-544.

“ Adults of this species first appeared active on May 30 and a few came to
bite. They were first noted in numbers on June 5, a warm, sunny day follow-
ing four days of cold, cloudy weather. They came drifting before the wind, and
during calm intervals were very annoying. At 10.45 a. m., on a rise of ground
west of the town, the highest rise on that part of the prairie, a swarm of about
50 males gathered above my head. They emitted a high-keyed piping sound,
swinging backward and forward and swaying sidewise, all the time facing the
wind. With every gust of wind they were scattered toward the ground, only to
reassemble when the wind decreased. When I passed the place again, at 12.45
p. m., the males were still in evidence, although much interfered with by the
wind. The same day, at 5.30 p. m., another swarm of males was observed in the
upper part of a ravine, where the slopes were gentle. They were going through
rapid evolutions, darting forward and upward and dropping back again, but
without unison. When disturbed by the wind their flight became more rapid,
and sudden gusts caused them to fly to the ground. Several pairs were seen
flying off in copula, and once the female was observed approaching the swarm
from beneath. There was a second swarm of males farther down the ravine,
about half way up the slope, and, like the other, at the margin of the shrubbery
filling the bottom of the ravine. In this case a swarm of very small Chironomids
was mixed with the lower part of the swarm. In crossing an open field in the
river valley at 6.30 p.m. a swarm of males formed over my head and, following
me, increased to the number of perhaps two hundred. They disappeared when
I approached the woods on the edge of aravine. This experience was repeated in
the field beyond, and upon nearing the edge of the woods the swarm again de-
parted and could be seen in the middle of the field. Several days of cold and
cloudy weather followed, during which the mosquitoes remained quiescent.
After the heavy rain of the previous night, the afternoon of June 9 was warm
and sunny and the mosquitoes exceedingly abundant and active. At 6.30 p. m.
I walked toward the river with a companion. As soon as we had left the town
the female mosquitoes began to rise out of the grass and alight upon us. There
was a brisk breeze blowing and the mosquitoes settled on the leeward side of our
bodies, and a cloud of them followed us, keeping for the most part about our legs.
These clouds increased rapidly and became very aggressive as we passed down
into the valley, where we came upon a cloud of males on the open prairie. When
we approached them they formed in two swarms over our heads. My companion,
being the bulkier man, attracted a much larger swarm. We thus each had two
swarms of mosquitoes about us; the one, of females, kept about the lower part of
our bodies, while the other one, of males, kept above our heads. Several copula-
tions were noted. Upon entering a ravine the males all left us and only a part of
the females followed. Upon emerging on the other side of the ravine a new
swarm of females quickly gathered, and shortly we came upon another large
swarm of males, which again concentrated above our heads in separate swarms.
It was now 7 o’clock, but still bright daylight at this season of the year. The
swarms of males I judged to contain many hundreds, if not a thousand, indi-
viduals. These swarms, in close formation, followed us up the long hill and
MALES OF MEGARHINUS 131

continued with us nearly to the town, in the end being much disturbed by the
wind. About 7 o’clock quite a number of copulations were observed. The
females approached the swarm from beneath and left it united with a male, the
pair drifting away toward the ground and the union lasting but a short time.
They copulate face to face, grasping each other with their long legs, the female
in the upper position, the male back downward. This day proved the maximum
of activity for this species of mosquito. No more swarming of males or matings
were observed.”

In the same paper occurs an account of the swarming of Aédes fitchii, also
in Saskatchewan. Following is the description:

“ On the evening of June 19 I was fortunate enough to observe the swarming
of this species in a shallow depression at the head of one of the ravines near
Oxbow. The ground sloped gently from the prairie, which at that point was 15
or 20 feet above the bottom of the depression. When the swarm of males was
first noticed, at 8.30 p. m., it was loosely organized, and there were perhaps forty
individuals, which gyrated and circled about close to the ground. Close by there
were some thorn brushes, and between and round these were several swarms of
Chironomide, but no mosquitoes. In a short time other swarms of mosquitoes
began to form in the open, along the bottom of the depression and on the
western slope, where they were protected from the wind. These various swarms
kept close to the ground and spread out in such a way that they might be said
to have been loosely connected, but still there were foci where the mosquitoes
were massed closer together. At no time was the top of a swarm more than
four feet above the ground, while it spread out to at least twice that diameter.
The size of the swarms gradually increased until, at 9 o’clock, one swarm con-
tained several hundred males. Copulation took place most frequently between
9 and 9.15, but matings were observed both earlier and later. The females en-
tered the swarm from beneath, when they were seized by one or more males.
Union takes place ‘face to face,’ the pair flying obliquely upward for several
yards. Then the pair would either separate promptly or swing out end to end
and struggle to disengage themselves. In this latter case both of them could be
seen to jerk violently and rapidly in their efforts to free themselves, and the
pair would slowly rise, but make no appreciable progress in either direction.
When two males seized a female the group would rise straight into the air,
apparently engaged in a violent struggle, one of the males finally uniting with
the female or all of them separating. In one case four individuals rose thus,
scrambling over each other, so to speak. The swarm was watched until 9.30,
when the twilight was already quite deep; copulation appeared to have ceased
and the swarms were gradually breaking up.”

Surgeon E. H. Ross remarks as follows regarding the mating-habits of
Aédes [Acartomyia] zammittti of the Mediterranean region. “ Coitus does not
necessarily take place on the wing, for I have observed it occur when the female
is resting on the edge of the glass jar or sitting on the rock; the male clasping
the female when she is sitting.”

Knab has observed that the males of Megarhinus tend to congregate upon a
certain bush, alighting upon prominent leaves. Near Puntarenas in Costa Rica
he captured six males of Megarhinus moctezuma upon a single bush. When
approached they would fly up but alight upon another leaf of the same bush ;
two that were frightened away returned to the bush after a short time. No
others could be found anywhere in the vicinity. Mr. J. K. Thibault, Jr., of

10
132 MOSQUITOES OF NORTH AMERICA

Scott, Arkansas, has observed the same habit in Megarhinus septentrionalis.
He took a large number of males of this species upon a certain vine of poison ivy
(Rhus toxicodendron) and always upon this one plant ; none could be found else-
where. Such bushes are undoubtedly places of rendezvous in connection with
the mating-habit.

Many species of Culicide, on account of their specialized mating-habits, can
not be bred in captivity. The yellow-fever mosquito, the mating-habits of which
are discussed in another chapter (p. 275), can be bred successfully for a num-
ber of generations in comparatively small receptacles. Dr. Dyar has bred two
generations of Aédes atropalpus in a quart jar containing a small quantity of
water.

ABUNDANCE OF MOSQUITOES.

In our treatment of the subjects of the migrations of mosquitoes, of their
carriage by wind, of far northern mosquitoes, and of early accounts of mos-
quitoes, we give many instances of mosquito abundance, and there will be men-
tioned here only certain recent observations. We have just discussed how at
times mosquitoes may be found gathered in concrete swarms for sexual purposes
and these swarms are appropriately considered under mating-habits, In so far,
however, as they are an indication of unusual abundance of mosquitoes they may
be mentioned here.

Theobald briefly describes a few swarms, probably of this character, as follows:

“ Occasionally cloud-like masses of various Culices are seen. I remember
twice having noticed dense swarms of them in the fens; in both cases the in-
sects were male and female C. cantans. So abundant were they that the air was
quite darkened by them. These insect-clouds were constantly moving up and
down about ten to twelve feet above the ground. At times the noise they pro-
duced could be heard a quarter of a mile off, then it would suddenly cease for
some time and commence again.

“Mr. W. W. Smith records a case in New Zealand where ‘a train passed
through a wall of mosquitoes three-quarters of a mile in length, twenty feet high,
and eighteen inches thick.’ This abnormal swarm was composed of Culex
(Uranotenia) argyropus Walker.

* * * * * * R *

“ During the present year I had reported that dense masses of gnats were seen
along the Downs near Wye, appearing like columns of smoke in the valley,
rising and falling. I did not see this, but visited the Down-sides the next day
and found great numbers of male C. pipiens about in the evening, dancing in
little clouds where they were sheltered from the wind.”

“Romolo Gessi Pascha, in his book ‘Seven Years in the Soudan,’ p. 47
(1892), speaks of ‘ myriads of mosquitoes which obscured the air’ at Meshra-el-
Rek. If we go to the Arctic regions we get similar phenomena, for Dr. Lugger
informs Professor Howard that Dr. Emile Bessels, of the Polaris Expedition,
was obliged to interrupt his work in Davis Straits (latitude 72° N.) on account
of the multitude of mosquitoes.”

The above notes on Culex pipiens clearly refer to swarms of males such as
have been described under mating habits. This may also be the case with the
above-mentioned swarms of Aédes cantans and Uranotenia argyropus, but there
MOSQUITOES OF THE NORTHWEST 133

are too few details to justify a conclusion. The abundance of such mating
swarms and the numbers of mosquitoes in them is, of course, an indication of
the abundance of the species as a whole. Such abundance may be normal and
occur from year to year, as with our northern mosquitoes, or it may be due to
unusually favorable conditions, such as increased breeding facilities for the
larvee.

One of us has elsewhere stated (Howard, “ Mosquitoes”) that Prof. E. W.
Hilgard, of the University of California, once wrote him that up in northern
Washington, in the pine forests north of Spokane, a gray mosquito seems to be
the sole possessor of the land, and is as fearful a nuisance as the mosquitoes in
arctic regions. “ The first thing on going into camp is to establish a close line of
smudges above the wind, so as to enable the pack animals and the men to eat in
comparative peace, but about midnight the entire swarm is back again.” Pro-
fessor Hilgard further wrote that in Montana he has seen all the work-horses in
the field sheathed in sheets during the day, to protect them from the swarms of
mosquitoes, and these were dotted with small blood spots.

Schwarz at Corpus Christi, Texas, in the late 90’s wrote that at that place,
“ when the wind blows from any other direction than south, ‘ hundreds of thou-
sands of millions’ of mosquitoes blow in upon the town. Great herds of horses
run before the mosquitoes in order to get to the water, but with a change of wind
the mosquitoes disappear.” Many parts of the North American continent are
famous for the numbers of the mosquitoes in the neighborhood. Felt has called
attention to the fact that these insects are so aggressive in some localities as to
give name to a place. For example, there is a town named “ Mosquito” in!
Tllinois, a village bearing the same title in Newfoundland, a Mosquito Creek in!
Indiana, another in Jowa, and still another in Ohio, while the whole eastern
coast of Central America is known as the Mosquito Coast. Riley is quoted as
stating that the bravest man on the fleetest horse dares not cross some of the
more rank and dark prairies of Minnesota in June.

Captain Butler in “The Great Lone Land” gives a vivid description of the
abundance of mosquitoes on the northwestern prairies in the early days.

“ As soon as the sun had dipped beneath the sea of verdure, an ominous sound
caused me to gallop on with increasing haste. The pony seemed to know the
significance of that sound much better than its rider. He no longer lagged, nor
needed the spur or whip to urge him to faster exertion, for darker and denser
than on the previous night there rose around us vast numbers of mosquitoes,—
choking masses of biting insects, no mere cloud thicker and denser in one place
than another, but one huge wall of never-ending insects, filling nostrils, ears,
and eyes. Where they came from I cannot tell: the prairie seemed too small to
hold them; the air too limited to yield them space. I have seen many vast
accumulations of insect-life in lands old and new, but never anything that
approached to this mountain of mosquitoes on the prairies of Dakota. To say
that they covered the coat of the horse that I rode, would be to give but a faint
idea of their numbers: they were literally six or eight deep upon his skin, and
with a single sweep of the hand one could crush myriads from his neck. Their
hum seemed to be in all things around. To ride for it was the sole resource.
Darkness came quickly down, but the track knew no turn, and for seven miles I
kept the pony at a gallop; my face, neck, and hands, cut and bleeding.
134 MOSQUITOES OF NORTH AMERICA

“ Tt took us but little time to rush over the gangway and seek safety from our
pursuers within the precincts of the steamboat. But they were not to be
baffled easily: they came in after us in millions; like Bishop Haddo’s rats, they
came ‘in at the windows and in at the doors,’ until in a very short space of time
the interior of the boat became perfectly black with insects. Attracted by the
light they flocked into the saloon, covering walls and ceiling in one dark mass.”

Mr. L. A. Fuertes, the well-known ornithologist, tells us that on the western
plains in Saskatchewan, at Maple Creek along the line of the Canadian Pacific
Railroad, in June, 1908, mosquitoes were so numerous and were such a pest
that, unless there was sufficient wind blowing to keep them down, it was almost
insupportable, and the sheep herders and the laborers on the railroads daily
were forced to wear head-nets and gloves in the pursuit of their occupations.
On nights when there was a slight wind, the cattle would trot up the breeze and
could be with certainty found at the farthest fence that they could get to.

Mr. H. W. Henshaw, of the Biological Survey, U. S. Department of Agri-
culture, relates the following:

“ While in camp on the western shores of Kern Lake, California, in the fall
of 1875, about 4 o’clock in the afternoon, the light breeze which had been blow-
ing steadily all day suddenly ceased. Within a few moments the air was so
filled with hosts of mosquitoes which came from the swampy land adjoining
the lake that it was impossible to talk without dozens of the insects entering the
mouth and nostrils. The mules which were picketed out on grass became
frantic, and it was only with the utmost difficulty they could be restrained—in
fact, so persistent were the attacks of the insects that the camp equipage was
immediately packed on the animals and the place vacated.”

When mosquitoes appear in such enormous numbers this is due to the simul-
taneous development of immense numbers of larve. In cases of. excessive
abundance the species concerned are nearly always single brooded. As the best
example we can give the northern species which must develop their single brood
in the early spring from the water of the melting snows. Naturally, in these
cases, there is a very evident relation between the amount of snow and the num-
ber of mosquitoes in different seasons.

It was until recently believed that mosquitoes reached such enormous abun-
dance by rapid progression through a series of generations. Careful observa-
tion, however, shows that those species which breed continuously throughout the
summer, while they increase somewhat in numbers as the season advances, never
reach the enormous numbers of the single-brooded species. It has been assumed
by some writers that an almost unlimited number of mosquitoes can be bred
from a single rain-water barrel. Lugger has attempted to estimate the actual
number of mosquitoes (eggs, larvae: and pup) present at one time in such a
barrel, as follows:

“ July 6th, 1896, the water in one barrel was filtered. It contained 35 grams
of mosquitoes, each gram, by count, numbering 217, hence 35x 217=7,595
larve and pups. Besides this 32 egg-masses, each containing on an average 302
eggs, were found, which would hatch into 302 x 32=9,664 mosquitoes. Total
number of eggs, larves and pupe 17,259. July 22d, 1896, by a similar process,
19,110 mosquitoes were counted.”
EXTRAORDINARY ABUNDANCE 135

At first sight these figures appear overwhelming; in fact, however, they are
insignificant. It must be remembered that the mosquitoes in a barrel are of all
stages, from egg to pupa, and that only a very small proportion reach maturity
each day. The greater the number of larvae present in a barrel the slower will
be their development, on account of the limited food supply, and it is by no means
certain that anywhere near all the larve in such a barrel ever attain the adult
state. Moreover the above figures appear exaggerated; thus counts by others
show an average, in some cases of about 200 eggs, in other cases less, in the egg-
masses of the common species.* Experience has shown us that the amount of
annoyance to the inhabitants of a house, from the mosquitoes of a single well-
stocked rain-water barrel, is not so great as would be thought, and beyond a very
limited area there is no perceptible effect.

One of us (Knab) has observed a case of extraordinary abundance of Culex
pipiens at Urbana, Illinois, due to unusual breeding facilities. A creek in the
vicinity of the town is practically stagnant in the late summer. At a certain
point this creek received the waste from an abattoir and, as a result, for some
distance was so charged with decomposing animal matter that no fish could
live in it. In this strongly polluted water immense numbers of Culex larve
throve. They were so numerous that their breathing-tubes produced the appear-
ance of a scum upon the surface of the water. The imagos covered the foliage
of the trees and bushes along the stream ; they were present in millions and they
continued to reproduce until cut off by cold weather. Yet their presence was
not felt at even a short distance, and very few of these mosquitoes found their
way into the town—perhaps a mile away.

Thus it will be seen that great mosquito abundance in any region is not the
result of the accumulated products of successive generations but the practically
simultaneous development of large numbers over a wide area.

MOSQUITOES IN THE FAR NORTH.

As is well known, mosquitoes abound, for a short season, even in arctic regions.
The writers have made a number of efforts to secure good mosquito material
from the arctic regions, but very few specimens have been sent in, so it has been
impossible to study the species, As a matter of fact, mosquitoes seem to be even
more numerous in individuals in the far north than they are in certain parts of
the tropics; in the tropics, on the other hand, there is a very much greater
variety and very many more species. Many accounts of arctic exploration and
of travels in the far north dwell upon the extraordinary abundance and ferocity
of the mosquitoes during the short arctic summer. Such accounts are merely
a part of the record of the travellers’ experiences and are almost wholly prompted
by the discomforts endured. They contribute practically nothing beyond the
facts which were forced upon the travellers—abundance and ferocity.

That mosquitoes should develop in such extraordinary numbers in the arctic
regions seems remarkable when we consider the extreme brevity of the summer
season. In fact, however, it is this brevity of the summer which brings about

 

* Weber, S. E.: Entom. News, v. 17, pp. 214-217; Davis, J. J.: Ibid., p. 369.
136 MOSQUITOES OF NORTH AMERICA

the extraordinary abundance of mosquitoes. There is, so to speak, over the
entire Arctic region, one enormous brood, which reaches maturity within a very
short time. The eggs, which have lain dormant from the previous summer,
hatch in the pools formed everywhere by the melting snows, and the larve de-
velop rapidly under the constant influence of the midnight sun. The abundance
of these northern mosquitoes, then, is not due to accumulations of the product
of a number of generations, but rests mainly upon the unlimited breeding
facilities furnished by the great number of pools of snow-water, for it is the
opportunities for larval development that largely determine the abundance of
mosquitoes.

Linneus in the “ Flora Lapponica” dwells at some length upon the great
abundance of mosquitoes in Lapland and the torments they inflict upon man and
beast. He states that he believes that nowhere else on earth are they found in
such abundance and he compares their numbers to the dust of the earth. Even
in the open you can not draw your breath without having your mouth and
nostrils filled with them; and ointments of tar and cream or of fish grease are
scarcely sufficient to protect even the case-hardened cuticle of the Laplander
from their bite. Even in their cabins the natives can not take a mouthful of
food or lie down to sleep unless they be fumigated almost to suffocation. The
Lapps of the desert keep their houses filled with a dense smoke by the burning of
fungi. The reindeer come to the houses of their own accord twice a day and the
herdsman fumigates them thoroughly by approaching the herd from the wind-
ward side with the smudge of fungi. The animals show the relief they ex-
perience from this treatment by chewing their cud and almost falling asleep.

The abundance of mosquitoes in the arctics is mentioned in the narrative of
nearly all arctic expeditions.

Sir John Ross in the appendix to the “ Narrative” of his second voyage
states: “ Of this genus [“ Culex ’’=Aédes] only one species was observed. It
first appeared about the 10th of July, on the 15th it became very numerous, and
on the 22d so extremely troublesome, as to prevent the necessary duties of the
ship. They were in perfect clouds over the marshes, and their larve constitute
the principal food of the trout that inhabit the lakes. It was only in the beau-
tiful summer of 1830 that we found them so very numerous. On the 13th of
August of that year they came out again after the rain, but were no longer very
troublesome, being apparently nipped by the frost at night; indeed soon after
this time the ground was again covered with snow, and all entomological ob-
servations were terminated.”

The expedition of the “ Alert ” and “ Discovery ” found mosquitoes extremely
troublesome when off the lower portions of the coast of Greenland; in the ex-
treme north they still found them common but not troublesome.

Lundbeck found that mosquitoes occur in enormous numbers on the west
coast of Greenland. He states that their bites are very troublesome and cause
swellings, particularly when one is attacked for the first time. “ Larve and
pup are common in all water holes all through the summer and the mosquito
itself is found from mid-June into August. The plague of mosquitoes reaches
ARCTIC MOSQUITOES 137

its culmination in the district of Kristianshaab; at Upernivik, on the other
hand, it is considerably lessened.”

Among modern writers Mr. Ernest Thompson Seton gives an interesting
account of his experiences with northern mosquitoes on a journey to the Great
Slave Lake region of Canada. This will be found in Scribner’s Magazine for
November, 1910, under the title: “The Arctic Prairies; i. The Land of the
Buffalo; 6. Mosquitoes (pp. 522-526). It quite substantiates the accounts of
the earlier travellers.

A. 8. Packard, in his book entitled “The Labrador Coast” (New York,
1891), on page 86, refers to mosquitoes on Caribou Island. He writes concern-
ing an alder swamp:

“ Here mosquitoes and black-flies swarm ; we are under shelter of a. cliff, and
there is no wind to keep off these horrible pests. How they rage and torment,
these myriad entomological furies!' Now for a frantic rush out of this purga-
tory, and a tiresome climb of a hundred feet up this cliff!”

Again, on page 191, referring to Strawberry Harbor—which, by the way, he
thinks must have been called “ Strawberry ” because it is but little larger than
that berry—he writes:

“ Deep and seemingly inaccessible to outside life as Strawberry Harbor prom-
ised to be, the next day, which was nearly calm and sunny, with a little breeze
from the east, the mosquitoes, swarming from land and peering over into our
den, swooped down upon us and made life miserable. Ashore with my insect-
net, they fairly drove me off the hunting ground, which proved to be richer in
arctic insect life than any yet experienced.”

The explorer, Charles F. Hall, gives many instances of mosquito abundance
during his extensive visits to Arctic America. The citations given here are from
the narrative of his second expedition, published in Washington in 1879. On
page 75 the statement is made that he went into winter quarters north of Depot
Island and had his beard cut, “Its length had been a special protection in the
summer months against those tremendous blood-suckers called in the English
tongue mosquitoes, which abound in swarms here.” Again, on page 322, the
statement is made that at Ships Harbor mosquitoes made their appearance as
early as the 4th of July. Again, on page 426, an account is given of a walk on
one of Hall’s trips to Talloon, as follows:

“The sun was about 5 degrees high. Not a breath of air stirring, the sun
shining hot, and the mosquitoes desperately intent on getting all the blood of
the only white man of the country. I kept up a constant battling with my seal-
skin mittens directly before my face, now and then letting them slap first on one
and then on the other of my hands, which operations crushed many a foe. It
seemed to me at times as if I never would get back. Minutes were like hours,
and the distance of about two miles seemed more like half a score. At length I
got back to my home, both temperature and temper high. I made quick work in
throwing open the canvas roof of our stores, and, getting to our medicine-chest,
snatched a half-pint bottle of mosquito proof oil, and with a little of this be-
smeared every exposable part of my person. How glorious and sudden was the
change. A thousand devils, each armed with lancet and blood-pump, coura-
geously battling my very face, departed at once in supreme disgust at the con-
founded stink the coal-oil had diffused about me.”
138 MOSQUITOES OF NORTH AMERICA

In the Bulletin of the New York Zoological Society, January, 1905, Mr. C. H.
Townsend, Director of the New York Aquarium, says:

“The writer has had very trying experiences with mosquitoes in the Arctic
portions of Alaska. During the short Arctic summer the cold, moss-grown
morasses of that region breed mosquitoes in vast numbers, and life is almost un-
bearable if one is not protected against them by gloves and veils. Sleep is
scarcely possible against them without the protection of netting.”

In his narrative of the Harriman Alaska Expedition of 1899, John Burroughs,
writing of Port Clarence, the northernmost point reached by the expedition says:

“ And mosquitoes, how they swarmed up out of the grass upon me, when in
my vain effort to reach a little voleanic cone that rose up there before me like a
haystack in a meadow, I sat down to rest. I could not seem to get nearer the
haystack although I sometimes ran to get rid of the mosquitoes.”

Miall, in his excellent work entitled “The Natural History of Aquatic In-
sects” (London, 1895), says of northern mosquitoes (pp. 109-110) :

“They have been found in immense numbers in uninhabited parts of Lab-
rador, on the tundras of Siberia and in the desolate Kerguelen Island. ‘ Of the
millions of mosquitoes which in the short Norwegian summer often thicken the
air of the Tromsdal—a wild valley within the Arctic Circle, practically unin-
habited either by man or probably by beast—how few are ever likely to taste
blood !,* Sir James Ross and his men found it necessary in their polar expedi-
tion to wear gauze over their faces in the summer months as a defence against
Gnats.”

The stories which the returning gold hunters from Dawson City and other
Alaskan localities told of the abundance and ferocity of Alaskan mosquitoes are
almost beyond belief, but are vouched for by scientific men, belonging to the
U. 8. Coast and Geodetic Survey, to the U. S. Geological Survey, and to the
Signal Service of the Army, who have come back to the United States with
similar and even stronger stories. An Alaskan traveler, the late W. C. Hender-
son, of Philadelphia, said, concerning Alaskan mosquitoes, “ They existed in
countless millions, driving us to the verge of suicide or insanity.”

Capt. A. T. Clifton, U. S. A. (Signal Corps), who has spent much time in
official work in Alaska, writes as follows (in litt.) :

“ Mosquitoes in Alaska seem to be numerous and poisonous pretty much over
the whole country. They are a hardy insect apparently, as they rise out of the
tundra from under the patches of snow in the spring, and in my quarters in St.
Michael they have appeared quite lively in December when a chinook sent the
thermometer up above 50 degrees above zero. Like the rest of their tribe, they
do not like wind or smoke, though they were so fierce at St. Michael that in a
thirty-mile breeze clouds have fallen in behind me as I breasted the wind,
taking advantage of the slight protection afforded by my body to alight on my
back. In central Alaska in the vicinity of Fairbanks and Fort Gibbon they are
just as fierce and if anything much more numerous, as the country is wooded
and covered with bushes as well as tundra. From May to August they are at
their worst.

“The only protection the prospectors, wood-choppers and Indians have is
from the use of smudges made of green grass, sticks and anything that will throw

 

* A, D. Michael, in Natural Science, vol. 1, p, 203.
MOSQUITOES OF ALASKA 139

off a dense smoke. I have seen telegraph operators ticking messages out at
isolated stations with their heads in a cloud of smoke from a smudge in a bucket
under the table, while mosquitoes hummed thick everywhere except in the im-
mediate vicinity.

“Stock has to be well protected in summer from their bites. I have seen and
heard of numerous cases where the poor animals have been driven frantic
from bites when not protected with empty gunny-sacks or nets of some kind.
The mosquitoes alight on the animals in such swarms as to entirely change the
color of the hide. Anything with blood seems to be a sweet morsel, and mosqui-
toes seem to race to see which shall be the first at it and the last to leave it.

“The Alaskan mosquitoes are huge, fierce, aggressive, and extraordinarily
persevering, and stop at nothing, for I have been well bitten through the pores
of my buckskin gauntlets.

“ When steamers stop at a wood-pile to ‘ wood-up’ the deck hands wrap their
heads up, leaving only the face exposed, and consequently only one spot to de-
fend, and each will move with his own attentive following in a dense and close
formation around his devoted head.

“The use of head-nets—a form of mosquito bar which is worn over the head
and comes down on the shoulders—is very common except in the timber, but it
is a fine scheme for torture if it gets torn, for the mosquitoes are always on the
alert unless prevented by rain, wind or smoke. The Indian smears his face,
neck and hands with a thick coating of mud and uses a smudge.

“ Tn Rex Beach’s good story, ‘ The Barrier, his killing a man with mosquitoes
is by no means far-fetched, for one can well imagine a man being stung to death
by the pests when left bound for insect slaughter. Personally I heard of a pros-
pector in the Inuoko country who had lost his bearings and wandered around in
the brush and timber with no means of warding off the attacks of mosquitoes,
and when found he was a raving maniac and never recovered. The Jersey
branch of the family is a mild suggestion compared with the Alaskan branch.
In Alaska the mosquito seems to breed in the tundra, brush, trees, anywhere
where there is moisture. The clearing off of the brush seems to lessen the swarms
in the immediate vicinity. I have watched a ball game at Fairbanks, standing in
the smoke of a smudge, and after the sun set, 10.30 p. m., was driven to cover
by them. They are as bad on the coast as in the interior, in the old settlements
as in the new, and are generally warred upon without seeming effect.”
EGGS AND OVIPOSITION.

The mode of disposal of the eggs shows wide diversities in different genera and
species and these affect the entire life-history of the species. The method of
oviposition best known is that of the typical species of Culex, and this is shared
by Culiseta, Lutzia, Mansonia and Uranotenia. In these forms the female lays
all her eggs at one time, grouping them together in the so-called raft or egg-
boat. These eggs are cylindrical, rounded at the ends, and taper slightly
towards one end. The eggs are placed in an upright position with the larger
end downward and are fastened together along their sides by a viscous secretion
which quickly hardens. The slight upward taper of the eggs brings about the
characteristic convexity of the bottom of the egg-raft and this prevents it from
being overturned. These egg-rafts are deposited either upon the water or close
to it. We have found egg-masses of Culex upon the sides of rain-water barrels,
some distance above the surface of the water. Egg-masses so placed are probably
carried to the water by rain-water, or perhaps even water from a heavy dew,
trickling down the walls of the barrel.

Réaumur, in his classic work, gives a detailed and most interesting account of
the egg-laying process in the common house-mosquito, Culex pipiens. The
account of this wonderful observer is so faithful that we reproduce it here:

“Towards the end of May I left my laboratory work at about 6 o’clock
in the morning, to watch the mosquitoes. The thermometer stood at 13-1/2
degrees . . . On arriving I first noticed more than thirty egg-masses which had
just been laid, but fortunately I saw also a mosquito which had not yet finished
oviposition. This mosquito was clinging by her four anterior legs to a bit of
leaf touching the side of the bucket. Her body was above the leaf, the penulti-
mate segment touching the water. A raft of eggs which was placed near the end
of her body and which had not yet reached full size indicated that the laying was
well advanced but not yet finished. The mosquito, busy with this important
measure, did not notice my presence, and permitted me to approach near enough
to her to watch her through a strong lens. I soon knew how it happens that the
eggs are placed perpendicularly to the surface of the water and how they are ar-
ranged. It is the end of the abdomen which does it all. We have said that the
penultimate segment of the body touches the water, and we can now say that the
last segment (that which carries the anus) forms with the rest of the body a kind
of hook elevated a little above the surface of the water. From this last segment,
thus turned up, I soon saw an egg come out; I saw that it came out in a different
direction from that in which the eggs ordinarily issue with other insects. The
latter are placed horizontally, or lying down, while these are placed upright,
in a vertical direction. The egg issues very near the mass of eggs already put
in place. As soon as it is entirely, or almost entirely out, the mosquito has only
to push it against those of the little boat which it is nearest to; for this egg, like
those of almost all insects, are without doubt provided with a sticky substance
which fastens it to the object to which it is applied.

“The laying of an egg and the placing it in position is for the mosquito an
affair of an instant, and as soon as she has placed one another begins to issue
from her body. The mosquito which I observed laid in this way, without inter-

140
REAUMUR ON OVIPOSITION 141

ruption, more than thirty eggs in less than two minutes; either because the lay-
ing was then finished, or because she was finally disturbed by my presence, she
flew away and left the little floating boat upon the water, but the shape of the
boat was not as regular as that of the majority of the other egg-boats. I searched
further, but could find no other mosquito engaged in laying. However, I had
not yet seen everything essential to the operation; I had been sufficiently in-
structed in the method by which the mosquito was able to place each egg per-
pendicularly on the surface of the water and to attach it to the mass composed
of eggs already laid, but it remained to be found out how the mass is sustained
upon the water when the base is still too small in relation to the height, how the
first egg is sustained or a small group of only two or three eggs. The mosquitoes
which | watched on the following days at 6 o’clock in the morning or thereabouts
gave me a complete explanation of this. I found them occupied in laying, find-
ing some in which the oviposition was very advanced and others in which the
mass was very small. These latter instructed me sufficiently concerning what
occurs at the instant when the first eggs are laid, a moment which is very diffi-
cult to observe. Among the mosquitoes which I watched in this operation were
several which were clinging with their four anterior legs to the wall of the
bucket, and others which, like the first one described, were standing upon a float-
ing fragment of leaf. The abdomen in both cases stretched over the surface of
the water and touched it only by a part of the penultimate segment. But what
was essential to notice was the position of the two hind legs, which are the
longest, or rather their positions, for I observed two different positions. The
mosquitoes which had almost finished laying and whose little boat was almost
completed had these two long legs extended and almost parallel to each other.
The end of each one reached to the surface of the water and even a little raised
above it, but they were both thrust a little in the water near the end, as though
forced by a weight, this weight being that of the little boat. This little boat
was, so to speak, on a dock. It was not abandoned to the water. The two legs,
like two long beams, sustained it at the surface of the water or a little above the
water. The mosquito held this boat in this way while she was adding eggs to it,
and she did not set it afloat until all the eggs had been placed.

“The mosquitoes which had advanced but slightly with egg laying and whose
boats had not yet reached half size had their legs in a different position from
that of which we have just spoken. Here the legs crossed each other in the form
of an X, and the place where they crossed was nearer the anus when the as-
semblage of eggs was smaller and the boat was shorter. The interior angle of
the legs sustained this little mass of eggs. From this it is easy to divine that
when the mosquito lays its first egg the legs are crossed very close to the end
of the body so as to support the egg; that they hold up the eggs which are suc-
cessively placed against this one ; that in proportion as the mass of eggs lengthens
the space between the place where the legs cross and the end of the abdomen
grows; and that finally the two legs assume a parallel position when the boat is
half or more than half done; and that thus, from the placing of the first egg
until the end, the eggs are always held up by the hind legs. It is only when the
laying is finished that the mosquito abandons the little boat, which is then in
condition to sail without risk.”

One of us (Knab) has observed the process of egg-laying in Culex territans
and found that it agrees substantially with the account of Réaumur. St. George
Gray, in the Journal of Tropical Medicine, vol. 6, page 313, has described the
remarkable manner of forming the egg-raft in an African mosquito.

“The fore and mid legs of the mosquito rested on a couple of the egg-rafts
that had been deposited at an earlier hour, and the two hind legs were stretched
142 MOSQUITOES OF NORTH AMERICA

out on the surface of the water behind her, parallel to each other, not crossed as
some observers state. A single row of creamy white eggs had been laid flat on
the surface of the water and were kept in position by the two hind legs. . . .

“ When the first row of eggs was completed she laid another row on the top of
it, and then another on the top of that, and so on until the raft was finished.
Then by a movement of the hind legs she tilted the raft so that the eggs stood
on end.”

In the genera Culex, Culiseta and Mansonia the egg-mass rests upon the sur-
face of the water. The mass has a certain repellant quality, inherent, it seems,
in a covering of delicate air-cells on the under surface. In the genera Urano-
tenia and Lutzia the egg-boat is in part submerged, only the upper part of the
eggs protruding from the water. Thus, Dyar states that in the egg-boat of
Uranotenia sapphirinus the middle eggs are nearly half submerged. In the
case of Lutzia bigotii, as observed by Jennings, the egg-boat is in large part
submerged, only the apices of the eggs protruding above the water. The eggs,
which are arranged in a double row, are remarkable in coloration ; the submerged
portion is pale yellow with a golden luster while the exposed part is pale blue.

The number of eggs and their mode of arrangement varies for the species,
and to a certain extent within the species. The egg-raft of Lutzia bigot, just
mentioned, is composed of about fifty eggs arranged in a double row. The eggs
of Mansonia fasciolatus and M. arribalzage are arranged in a long, ribbon-like,
double row with a gentle convexity upon the under side. Goeldi states that
there are about 60 eggs in these egg-rafts but his reproductions of photographs
of such egg-masses show from 70 to 80 eggs in a row, therefore 140 to 160 in the
entire mass. Our Mansonia perturbans forms an egg-raft similar to that of
Culex, that is, with the eggs in a number of rows forming an elongate mass and
the under surface of the mass convex. In Culez, Culiseta and Uranotenia the
egg-masses are elongate, and, on account of the convexity of the lower surface,
the sides are somewhat upturned.

Few exact data are available as to the number of eggs laid, even for the com-
monest species. With reference to the common house mosquito, Culex pipiens,
250-300 is generally given as the normal number, a statement to be traced back
to Réaumur’s work. Our American observations are unsatisfactory, as a num-
ber of species have undoubtedly been confused under the one name. Davis, in
Illinois, found the number to vary from 120 to 309 in a count of ten egg-boats.
Smith states that normally the number of eggs laid by Culex pipiens in a single
raft is about 400 but that if the female is disturbed in the process there may be
two or more smaller rafts formed. Goeldi (at Pard), in a count of two egg-
masses of Culex quinquefasciatus found 225 and 270 eggs respectively and his
pictures show that they are arranged in from 9 to11 rows. C.S. Banks, with the
same species before him in the Philippines, found the number of eggs from 180-
350, arranged in from 6 to 9 rows. In Culex territans two egg-masses counted
by Knab contained respectively 105 eggs in six rows and 132 eggs in eight rows.

A singular departure in the mode of egg-laying, or rather in the character of
the eggs, has been recorded by Busck in Culex jenningsi, and this is probably
shared by other bromelia-inhabiting species of Culex. In this case the eggs are
DISPOSAL OF EGGS 143

deposited in the water and surrounded by a gelatinous substance. Busck found
about twenty-five of these eggs united in an ovate gelatinous mass, each egg
surrounded by its own spherical gelatinous envelope and supplied with an air-
bubble which helped to keep the mass afloat. Mr. Jennings has since repeated
this observation. The gelatinous matter furnished the first food to the newly
hatched larvee.

So far Joblotia digitatus stands unique, not only among the members of the
genus, but in the entire tribe of Sabethini, by depositing its eggs in a raft. Its
raft is a type entirely distinct from those previously described. It is flat and
circular in outline, instead of elongate and concave as in the egg-boats of Culex.

Anopheles deposits its eggs separately in small numbers, upon the surface of
the water. The eggs lie upon their sides and are kept afloat by a peculiar struc-
ture, a partial envelope which is more or less expanded, particularly along the
median portion of the egg. This hydrostatic organ is variously shaped and de-
veloped in the different species of Anopheles. In one case, Anopheles turkhuds
of India, this apparatus is nearly obsolete and the only trace remaining is a
small rudiment concentrated near the larger end. In a remarkable Brazilian
anopheline, Chagasia fajardot, the hydrostatic apparatus reaches a remarkable
development, completely surrounding the egg and forming a series of longi-
tudinal, remarkably constructed, air-chambers.

So far as we are aware the eggs of all Anopheles are provided with the hydro-
static organ and are normally laid upon the water. The eggs of such a large
proportion of the species are now known that we can expect no exceptions. The
eggs of Anopheles turkhudi and Chagasia fajardot, just described, probably rep-
resent the two extremes of modification of the hydrostatic organ. Recently H. I.
Cazeneuve claims to have found that in northern China Anopheles pass the
winter in the egg-state, the eggs being frozen into the mud and hatching when
thawed out. The observation evidently is based on an error in determination.
Cazeneuve has undoubtedly taken the males of certain species of Aédes (which
agree exactly in habits with his observations) for Anopheles on account of their
long palpi. This is the more excusable as several famous entomologists, in their
systematic work, have fallen into the same error and have described males of
culicines as Anopheles.

The eggs of Bancroftia signifer are laid singly upon their sides, at the margin
of the water. These eggs are remarkable in that they are fastened down by a
gelatinous covering which extends all around them in the form of a broad,
curiously sculptured, rim. Megarhinus lays its eggs singly upon the water.
Goeldi found the egg-shells of Megarhinus hemorrhoidalis floating separately
upon the water in little groups of from four to six and this has given rise to the
statement that the eggs are laid in chains. Green, in Ceylon, has obtained the
eggs of Megarhinus immisericors from a confined female and found that they
were scattered singly over the surface of the water. The eggs are regularly oval
and their surface is closely studded with spinose tubercles which hold the air
between them and keep the egg afloat. “ The actual operation of egg-laying was
not seen, but the female was observed jerking itself up and down in the air just
above the water, and it seems probable that the eggs were shed at that time.”
144 MOSQUITOES OF NORTH AMERICA

All the mosquitoes we have so far considered, with the exception of Bancroftia,
lay their eggs upon the water, or, in the case of Culex jenningst, into the water.
In these the development of the larva within goes on uninterruptedly and the
eggs hatch within a short time. We now come to a group of mosquitoes in which
the eggs lie dormant for some time to await favorable conditions for the de-
velopment of the larva. These are the species of the genera Aédes and Psoro-
phora. In these forms the eggs are laid singly or in small batches, never fastened
together in the form of a raft, and, in most cases at least, not upon the water.
That they are not laid upon the water is shown by the fact that, where for a long
time there has been no water, the larve appear promptly when puddles are
formed. In these mosquitoes the female does not mature all her ova at one time ;
therefore they are deposited in several batches, at intervals. To Aédes belong
the mosquitoes which are so troublesome in the northern regions and we have
already touched upon their breeding-habits in our discussion of the adults.
The eggs are laid in the summer and they do not hatch until the following
spring, when the larve appear in great numbers in the water from the melting
snows. The females must deposit their eggs upon the ground, at least in most
cases, for by the time they have developed their ova the breeding-places have
usually dried out. Galli-Valerio and Rochaz de Jongh, in Switzerland, have

_ found hibernating single eggs attached to fallen leaves in depressions of the

) ground. It appears that the hibernating eggs, although they may be repeatedly

) submerged, will not hatch before they have been subjected to freezing tempera-

{ tures. Thus these mosquitoes appear in one great annual brood, in spite of the

- fact that the eggs are not all laid at one time. With a few species of these
northern Aédes, for example Aédes fuscus and A. canadensis, larvee appear in
small numbers at intervals during the summer, after heavy rains, These larve
are undoubtedly from hibernated eggs which failed to hatch in the spring, and
not from freshly laid ones. Eysell, who observed species with similar habits in
Germany, suggested two ways in which such subsequent appearance of larve
might be accounted for. Eggs which were not submerged in the early spring
might be washed into the pools by heavy rains. Or the water in the pools might
be raised to a higher level and reach eggs until then unsubmerged.

A peculiarity of the eggs of the group we are now considering is that not all
of them hatch at one time; a certain number lie over until later in the season or
even until another year. To the southward the species of Aédes depend for the
most part upon the rains for their development. In regions with a well-marked
dry season the eggs must withstand desiccation for a long period. Here the eggs
lie upon the ground from one rainy season to another, hatching with great
promptness when submerged by the rains. Viereck found that in the case of one
of our salt-marsh mosquitoes (Aédes sollicitans) that upon immersing a piece
of sod which contained eggs the young larve appeared within three minutes.
This prompt hatching is of the greatest importance as in hot climates rain-
puddles dry out very rapidly and the mosquito must reach full development
before this occurs. As it is, whole broods must often perish through the too
rapid drying up of their breeding places. Another provision, to insure the
EGGS OF SABETHINI 145

species against destruction in such case, exists in the fact, already mentioned,
that not all the eggs hatch, a part of them lying over until again submerged by
subsequent rains.

Certain species of Aédes and Stegoconops are partial to the water in hollow
trees and these are almost continuous breeders during favorable conditions and,
while they are dependent to a certain extent upon rains, they show no well-
marked broods. These species deposit their eggs near the water, usually close
to the moist margin above it, and the eggs hatch when the water rises to them.
The water in such holes in trees is usually well protected against desiccation and
every slight rain contributes to it; as a comparatively slight rise of water will
reach the eggs, these can hatch at frequent intervals. The yellow-fever mosquito
(Aédes calopus), although so closely associated with man, is in its habits es-
sentially a tree-hole species. The eggs are deposited in the same manner, only,
through the fact that they are deposited in water receptacles which are being
constantly refilled by man, the chances for the hatching of the eggs are greatly
increased and, to a large extent, made independent of weather conditions.

Little is known of the eggs or egg-laying habits of the tribe of Sabethini. We
have already mentioned that Joblotia digitatus lays its eggs in a raft. Other
species of Joblotia lay their eggs singly upon the water.

Smith found that with the pitcher-plant mosquito (Wyeomyia smithii) the
favorite place for the disposal of eggs is the younger leaves which had not yet
filled with water. The eggs were found in abundance upon the inner surface of
such leaves ; they were also found in lesser numbers, floating upon the water in
the older leaves, and the oldest leaves had the fewest eggs. Busck, in Trinidad
and Panama, found certain species of Wyeomyia breeding in the flower-spathes
of Heliconia. The eggs were found deposited in the uppermost, still unex-
panded, spathes of the series, which as yet contained no water.
HABITS OF THE LARV£E.

So far as known the larva of all mosquitoes are aquatic. The larval forms of
so many of the genera are now known that it can be considered safe to assume
that there will be no exceptions found. It has already become apparent from
the egg-laying habits that mosquito larve occur in a great variety of situations.
What has not been sufficiently understood until recently is that each species, or
group of species, has its own very definite habitat—a fact of the greatest eco-
nomic importance. By far the most of the mosquito larve occur in small de-
posits of water. While certain species do occur in large bodies of water, such as
ponds and streams, this is under unusually favorable circumstances, and even
then they are present only in small numbers. In the larger bodies of water fish
and other life act as a check upon mosquitoes, if, indeed, their eggs are deposited
there at all, which there is reason to doubt.

Those species of mosquitoes which appear in the greatest abundance develop
in transient deposits of water. This is the case with the mosquitoes of the genus
Aédes which are so troublesome in our northern woods and in the arctic regions
in early summer. The eggs of these mosquitoes are deposited upon the ground
during the summer. There the eggs lie until the following spring; although
they are repeatedly wetted or even immersed in water they will not hatch until
the following spring. Then, with the melting of the snows, the eggs promptly
hatch and the larve appear in the pools of snow-water in immense numbers.
The previous freezing appears to be a necessary stimulus to their development.
In the course of a few short weeks the entire mosquito crop of those regions is
produced.

It has often been noted that upon the plains of the arid and semi-arid west
mosquitoes occur at times in immense numbers and their presence, in the
absence of all water, has seemed inexplicable. Yet these too pass their larval
life in the water. On the northern plains these mosquitoes develop in the very
transient snow-water, in the manner described above; south of the regions of
heavy snow-fall they depend upon temporary deposits of water resulting from
heavy rains. Similarly, in semi-arid tropical regions the appearance of mos-
quitoes depends upon the heavy rains of the summer months. The rapidity of
development of the larve in such regions is astounding, but it is conditioned by
the rapid evaporation of the rain puddles in such acclimate. The eggs which had
lain upon the ground for a year, and perhaps two years, upon being submerged
hatch at once; the larve reach their full growth within one or two days and the
pupal period is a matter of hours. Even so a whole brood may perish from the
too rapid drying of the pools. There is a remarkable provision to prevent the
extermination of the species through such circumstances, in the fact, above
mentioned, that not all the eggs hatch at one time. Part of them lie over
until a succeeding rain, and some of them even until another year. Thus the

146
BREEDING PLACES 147

survival of the species is assured. All the forms so far discussed, and to them
belong by far the most mosquitoes in point of numbers, being dependent upon
seasonal conditions, show a marked periodicity. This is also true of the salt-
marsh mosquitoes, although their development is governed by somewhat differ-
ent conditions and there may be, and usually are, a number of broods during a
season. Here the determining factor is the flooding of the marsh, either by
rains or by a high tide, the higher ground along the beach preventing the escape
of the water. Here again the eggs lie buried in the mud or sod and hatch when
submerged, and here, also, a part of the eggs lie over until another flooding of
the marsh. On the Pacific coast, where no rains occur for many months, a crop
of salt marsh mosquitoes appears every four weeks following the monthly high
tides that overflow the upper reaches of the marshes where the eggs are. All
these species in which a long unfavorable period is passed in the egg state are
closely related and belong to the genera Aédes and Psorophora. The genus
Psorophora is most adapted to the conditions in the semi-arid tropics. Simul-
taneously appear, and developing with equal rapidity, the non-predaceous larvee
of the subgenus Janthinosoma and those of Psorophora proper which prey
upon them.

In marked contrast to the forms just discussed are those which breed con-
tinuously, as long as breeding-places exist and temperature conditions are
favorable. Such are the forms in which the eggs are deposited upon the water
and which hatch soon after being deposited ; these are the species of Anopheles,
Culex, Culiseta, Uranotenia and Lutzia. The growth of the larve depends upon
food conditions and upon temperature, so with these forms there are no well-
marked broods or generations; adults and larve in all stages may be found at
all times until frost cuts the larve off. As it is the hibernating females that pre-
serve the species until the following season, and many of these females die off
in the course of the winter, these species first make their appearance in small
numbers and gradually increase to the end of the season. Never, however, do
they reach such enormous numbers as the periodic species. To the continuous
breeders belong the house mosquitoes which breed in rain-water barrels or other
artificial receptacles. Other species of Culex breed in natural pools of a more or
less permanent character, in swamps, or along the margins of streams. Others
breed in the water of various water-bearing plants, such as the bromeliads, Heli-
conia and Calathea of the tropics. In these continuous breeders the eggs are
laid upon the water and develop at once, hatching within a few days. Certain
forms of Aédes take a position intermediate between the forms with well-marked
broods and the continuous breeders. Such are the species of Aédes and Stego-
conops which breed in the water in hollow trees and in similar situations. With
these the eggs are laid above the water line and they hatch when the water
rises to them. As the result of successive rises, due to rains or other causes,
eggs hatch at brief intervals and larve of various sizes are always present. Thus
mosquitoes of these species are continuously present while there is warm
weather and occasional rain.

11
148 MOSQUITOES OF NORTH AMERICA

An important fact to be considered is the habitat peculiar to each species or
group of species and this, of course, is intimately connected with the feeding
habits. Thus certain species are found only in rain puddles charged with mud.
Other species thrive in pools and ditches full of dead leaves and other vegetable
debris, or in sphagnum swamps. The Anopheles larve are surface feeders and
often occur where there is a slight flow of clear water which favors the growth of
the alge upon which they feed. Some species of Anopheles thrive, however, in
other situations. We have found the larve of certain species plentiful in tem-
porary rain puddles which showed no trace of alge. Other species of Anopheles
breed in the water in holes of trees and between the leaves of bromeliaceous
plants. Tree-holes form the habitat of the larve of a number of species of mos-
quitoes which breed nowhere else. Plate x, fig. 3, shows such a mosquito breed-
ing tree-hole. Others, while strongly attached to tree-holes, show a certain
degree of adaptability, breeding in rock-pools, tubs and barrels under suitable
conditions. It is to be supposed that the food conditions along with the general
environment are here the determining factors.

In the tropics the larvee of many species live in the water or liquid held by
various plants which are modified for this purpose. While this water or liquid
furnishes a breeding-place for mosquitoes and other insects it fulfills a more or
less important function in the economy of the plant. Thus in many Brome-
liaceze water collects at the bases of the leaves and this water serves as a barrier
to prevent the access of ants and other injurious insects to the flowers. With
certain tropical American species of Heliconia and Calathea the flower bracts
form a receptacle whose office is probably primarily to protect the flower itself.
In the case of Calathea at least the liquid held by the bracts is dark and thick
and is probably secreted by the plant itself. In America certain species of
Sarracenia and in the East Indies certain Nepenthes have leaves peculiarly
modified to hold liquid. These leaves act as traps to most insects, which, having
entered, can not escape and are finally drowned. Their decomposition is sup-
posed to furnish food for the plant. In our common pitcher plant (Sarracenia
purpurea) the leaf cups are open and have a broad lip to catch the rain-water
and dew. In the case of Nepenthes the leaf cup has a lid which projects over its
mouth and which, while it does not close it, prevents water from entering; the
cups are filled with a viscous liquid secreted by the plant itself. All these plants
support mosquitoes peculiar to themselves. In tropical America the many
species of the tribe Sabethini inhabit almost exclusively such plants. Certain
species of Culex are peculiar to the bromeliads, as are also a few species of
Anopheles and Megarhinus. Most of these larve are scavengers and feed upon
the remains of insects that have been trapped by the plants. A few are pre-
daceous and prey upon the larve of the other species. Such are Lesticocampa
and certain species of Megarhinus. A remarkable fact is that even these canni-
balistic forms are confined to a single plant, each species of plant thus having
a fauna peculiar to itself. The only case in our temperate zone, of such close
adaptation to a single plant, is the pitcher-plant mosquito, Wyeomyia smithit.
Our plates iv, v and vi show water-bearing plants known to harbor mosquito
larve and other aquatic insects in the American tropics.
PECULIAR HABITATS 149

In the moist tropics the water-filled ends of broken bamboos furnish breeding-
places to a number of species. In America among the bamboo inhabitants the
sabethids again rank first in number of species belonging to several genera;
of culicines there are representatives of Culex, Carrollia, Stegoconops and
Megarhinus. Here again we have, among these species restricted to a peculiar
habitat, predaceous forms (Sabethinus, Megarhinus) which prey upon the
others. A few species of Sabethini breed in the water of cocoanut and cacao-
husks and their larve are rarely found elsewhere. The larvee of Limatus and
of Joblotia digitatus are constantly found in these husks and they thrive there
no matter how foul the liquid, as a result of the decomposing vegetable matter,
may become.

A peculiar habitat is furnished by certain reeds growing in swamps. The
leaves begin to spread below the surface of the water and thus form a chamber
isolated from the surrounding water. The larve of several species of Wyeomyia
have been found in this situation and Lutz has found there the larva of
Menolepis.

In the tide-water regions of the American tropics certain crabs live in holes
in the soil which go below the water level. In the water in these holes, some-
times at a considerable depth below ground, certain species of mosquitoes breed.
Most remarkable of these are the specialized forms of Deinocerites and related
genera. Besides these there are a number of species of Culex peculiar to the
crab-holes and even structurally these show more or less adaptation to their
habitat.

The most peculiar and specialized larvee of mosquitoes yet discovered are the
species of Mansonia (Teniorhynchus, auct.). The habits of these larve have
recently been worked out with our common Mansonia perturbans and the same
habits are indicated for Mansonia fasctolatus and M. arribalzage. The eggs are
laid in swamps where there is a dense growth of grass and sedges. The newly
hatched larvee make their way down through the water to the roots of these
plants and there they attach themselves by inserting the apex of the peculiarly
constructed breathing-tube. Here they remain anchored until full grown, ob-
taining air through the vascular tissues of the plant-roots. The pupa, it appears,
remains in the same situation, deriving air from the roots by means of its
peculiarly modified thoracic “breathing trumpets.” The habits of Mansonia
tstillans are similar according to the observations of H. W. B. Moore, except that
the host plant is Pistia, an aquatic plant belonging to the Aracez, which grows
in floating tufts, the roots loosely entangled in the mud.

The subject of the character of water frequented by the larve of different
species has already been touched upon in the discussion of their habitats. By
far the largest number of species frequent fresh water. Certain species, how-
ever, occur in saline water and some in water charged with alkali. Some species
thrive in sea-water of full strength and even in water, as a result of evaporation,
of much greater salinity. The larve of these same species will do equally well
in brackish or even in entirely fresh water. This is important in the economy
of the species as opportunities for larval development may be produced at one
150 MOSQUITOES OF NORTH AMERICA

time by overflowing sea-water from a high tide or storm, at another by the flood-
ing from heavy rains. On the Panama coast the larve of a species of Stego-
conops and of Aédes fluviatilis occur in rock pools of concentrated sea water
resulting from the splash of high seas. The larve of these identical species occur
inland in perfectly fresh water. Of most of the salt-water species it may how-
ever be said that they adhere closely to the tide-water region; Aédes sollicitans
may almost be said to be confined to the pools immediately back of the sea
beaches. While these larve occur in salt or fresh water and will survive a cer-
tain change of density of their medium, as in the case of a salt-water pool being
diluted by rains, transfer from one medium to the other is fatal to them. The
cause of death in this case is the osmotic action of the media of different density.
Perhaps the most remarkable of the species breeding in salt water is Aédes
zammittii of the Mediterranean region. According to Surgeon HE. H. Ross
they occur only in highly concentrated sea-water as it occurs in the rock-pools
left by high tides. He states that while, in summer Mediterranean sea-water
contains twenty-eight grammes of salt per litre, this species “can only live in
water containing from forty-eight to eighty-seven grammes per litre of salt.
As soon as salt begins to be formed on the surface of the pool, the larve and
pupz move on to another part of the pool, which is often most extensive. These
pools may be very deep, but, in common with all the sea-water pools on the shore
of the Mediterranean, never contain fish or shrimps. When a thin layer of salt
forms on the whole surface of the pool, the larve die.” Carter found that if the
water was sufficiently saline the larve were present, regardless whether the
water was strongly polluted or very clean. At Port Said he found them in
cesspools under the houses in which there was a large percentage of salt.

THE FOOD OF MOSQUITO LARV£E.

The larve of many species undoubtedly swallow anything in the water that
they inhabit which can enter their mouths. With many of the species the mouth-
brushes produce a vortex into which pass all minute objects floating on the water
or suspended in the water. The spores of algex, particles of dust, bacteria, pro-
tozoa, minute aquatic animals of many different kinds, are thus swallowed. With
many species it seems that the important food is animal. Anopheles has been
found feeding upon the dead bodies of other culicid larve. In studying the
larvee of Anopheles quadrimaculatus in the laboratory, these insects seemed to
thrive best in water containing green alge, and this observation has been con-
firmed by other laboratory workers; but it has been suggested that perhaps the
important food of these larve is after all the microscopic animal life which
swarms among these alge and of which the alge themselves constitute perhaps
part of the food. The alge in our experiments belonged to the genera Aédo-
gonium, Cladophora, Spirogyra and in lesser degree Oscillaria. Stephens and
Christophers have found that the food of Anopheles larve examined at Accra
consisted of a unicellular organism (Protococcus?). Theobald found that the
food sucked into the mouth of the larve of Culer pipiens and C. nigritulus
consisted of alge and water crustacea such as Daphnia and Cyclops. He has
FOOD OF LARVA5 151

bred C. nigritulus almost exclusively upon flagellate protozoa which seem to he
a very favorite food of this species. In our experience the larvee of Aédes, which
occur in early spring, when small crustacea often abound, do not feed upon these
latter. In confinement the Aédes larve do not thrive if many crustacea are
present in the water and probably these deprive the mosquito larve of their food. ,
In nature these Aédes larve are largely bottom feeders and they may be seen
vigorously working over the dead leaves and vegetable debris with their mouth
organs, apparently removing the fungoid growth which covers them.

Certain larve thrive best where animal refuse abounds in the water and this
is particularly true of the species associated with man. The larve of Culex
pipiens and Culex quinquefasciatus develop most rapidly in water charged with
fecal matter or animal refuse. The same has been asserted for the yellow-fever
mosquito by the Brazilian observers. We have found that the larve of this
species thrive in comparatively pure water, in collections of rain-water, in jars
or bottles of drinking water. Unavoidably such water, kept in or near the house,
although clear, does contain a certain amount of animal matter and it is upon
this the larve feed.

The food of the larve of the pitcher-plant mosquito (Wyeomyta smithit) con-
sists altogether of the remains of insects that have been trapped by the plant.
The presence of such food, and its amount, are largely a matter of accident and
upon it the growth of the larve depends. Sometimes no insects find their way
into a water-filled leaf for a considerable time but the larve can endure starva-
tion for a long period. Larve of this species which we have kept without food in
the laboratory, lived nearly a whole year. Probably the larvee of all the species
of Wyeomyia are scavengers feeding upon insects’ remains, although those in the
bromeliads at least, have access to vegetable debris. The larve of Joblotia and
LIimatus appear to feed wholly upon dead insects and their remains and their
powerful mandibles are well fitted for this work.

It has already been mentioned that the larve of certain genera are predaceous,
in every case feeding upon other mosquito larve.. The genera known to have
predaceous larve are Celodiazesis, Megarhinus, Psorophora, Lutzia, Lestico-
campa and Sabethinus. Each of these larve has its own peculiar habitat and as
a result it is limited in its food to the larve found there. The larve of Celo-
diazesis barbert occur in water in hollow trees and there they prey upon the
larve of Bancroftia signifer and Aédes triseriatus. These larve have another
formidable enemy in the larva of Megarhinus septentrionalis which usually
occurs singly or in small numbers in tree-holes. Some of the tropical species of
Megarhinus also live in tree-holes—others are partial to bromeliads and to
bamboos, while one occurs in cocoanut-husks and preys upon the larve of
Joblotia digitatus. The larve of Psorophora occur almost wholly in rain-
puddles where the predaceous species feed upon those of the subgenus Janthi-
nosoma and of Aédes. They are extremely voracious and consequently their
development is very rapid. Lutzia is a continuous breeder and consequently
preys more largely upon Culex larve. The habits of the predaceous sabethine
forms are very imperfectly known. The larve of different species of Lestico-
152 MOSQUITOES OF NORTH AMERICA

campa appear to be restricted in habitat, each to a particular plant, where they
prey upon the other mosquito inhabitants.

Certain mosquito larvee may be said to be partly cannibalistic, feeding upon
their own kind and upon other species when pressed for food. This has been
observed with Anopheles, and in Brazil Aédes calopus and Limatus durhamu
have been shown to behave in the same way by Peryasst and his associates.

It would seem, on the whole, that the presence of mosquito larve in water must
be beneficial rather than the reverse, and this is probably the only good thing
from the humanistic standpoint which can be said about mosquitoes. Of course
there is no doubt as to the benefits derived from the larvee of Psorophora, Mega-
rhinus, Lutzia and the like, since they destroy the larve of other biting mosqui-
toes, including those forms which carry disease. As to the others, their effect
upon the water on the whole must be purifying, and there is an idea in parts of
Texas and others of the southern United States that where mosquito larve occur
in the rain-water tanks and wells—the tanks in many places furnishing the
drinking water supply—this water is purer and safer than water which does not
contain these larve. We have had drinking water served at table in small hotels
in the South, which contained Culex or Aédes larve, and, on requesting a glass
of water without larve in it, have been assured by the waiters that this was an
evidence of the purity of the water. This possibly restricted popular idea may
have a sound basis, since certainly mosquito larve eat many organisms and
among these must often be such as are injurious to the human species. It must
be remembered, however, that with bacilli this function may not in the least
reduce their vitality and they may pass through the alimentary canal of the
mosquito larva unharmed.

Recently Boyce and Lewis have attempted to show that bacteria thrive better
in the presence of mosquito larve, and this may be true under some circum-
stances. They point out that there is some opposition to the destruction of the
larvee of the yellow-fever mosquito (Aédes calopus) in receptacles with drinking
water on account of their supposed purifying function. To test the truth of this
belief they made a series of experiments. These consisted in placing larve of
Culex and of Culiseta annulatus “in a flask of non-sterilized drinking-water,
and comparing from day to day the number of bacteria present in the water with
the number present in a control flask to which no larvee had been added. The
number of bacteria was estimated by plating 1 cc. of the water in gelatine and
incubating at 21° C. for 72 hours.” In all but one of the four experiments the
bacteria showed greater increase in the flasks with mosquito larva. This in-
crease might easily have been due to the introduction of further bacteria together
with the mosquito larve, although it finds its readiest explanation in the organic
substances discharged by the larvee. The experiments are inconclusive as they
were carried out under artificial conditions and as, furthermore, it is impossible
to avoid all sources of error. The fact that the larve of different species differ
in feeding habits also must not be lost sight of as it will affect the bacteria.

There is great diversity in the behavior of mosquito larvee. Some live almost
wholly at the surface of the water, others at the bottom, while many rise and
MODES OF FEEDING 153

descend—seeking their food along the bottom and being obliged to come to the
surface for air. The larve of Anopheles normally remain at the surface. They
lie with their bodies extended straight and locked to the surface film by the
chitinous flaps surrounding the sessile breathing-tube and by the stellate tufts
of the abdominal segments. When they move they do so in very rapid jerks,
either along the surface, or, when alarmed, descending into the water. When the
Anopheles larva is at rest its body is always extended in a straight line and this
gives these larvee a curiously rigid appearance which is very characteristic. The
head is very motile and in feeding its ventral side is usually turned upward,
while the mouth-brushes, in constant vibration, produce a current which brings
floating particles to the mouth.

The larve of other mosquitoes progress through the water with a peculiar
snake-like motion, most marked in the species with the longest bodies, such as
Aédes calopus and Aédes triseriatus. The movement is a lashing one; the body
is bent in the shape of a letter “S ” and lashed from side to side. Certain larve
can also be seen, at times, progressing merely by the action of the mouth-brushes.
In the former case the larva progresses through the water backwards, in the
latter case it moves head foremost. _

The larve of many Culea and Aédes feed mostly while suspended from the
surface film by the end of the breathing-tube, obtaining their food by the action
of the mouth-brushes. Other larve feed at the bottom and only come to the
surface at intervals to obtain air, this interval differing with the species. Some,
indeed, never rise to the surface and obtain the necessary oxygen from the water
by osmosis, or, in the case of Mansonia, from the vascular roots of aquatic plants.

The attitude, when suspended from the surface film, differs with the species.
Uranotenia maintains a horizontal body-position and this, together with the
similarity in the shape of the head, produces a resemblance to Anopheles which
has often proved deceptive. The larva of Culex territans holds its body in a
nearly horizontal position when suspended from the surface film, but the long
perpendicular breathing-tube and the broad deflexed head give it a characteristic
appearance. Other species suspend themselves with their bodies at more or less
of an angle. In certain species of Aédes the body hangs nearly straight down.

Certain larve feed altogether at the bottom and only come to the surface at
long intervals. Such is the case with many species of Aédes. Wycomyia and
other sabethids are bottom feeders and are busy most of the time working over
the rubbish at the bottom of the breeding-places ; they seem to require but little
air and never remain suspended from the surface film for any length of time.
The larve of certain species of Culex lie upon the bottom back downward,
anchored, so to speak, by a pair of hooks at the tip of the breathing-tube; the
head is somewhat deflexed and the large mouth-brushes procure the food ; they
rise at intervals for air. Psorophora discolor has a larva of very similar habits;
however, it never comes to the surface, procuring oxygen from the water by
means of the highly developed anal gills.

The predaceous larve can not be said to hunt their prey. They remain
quiescent until a larva comes within reach when they seize it with great rapidity.
154 MOSQUITOES OF NORTH AMERICA

One of their own kind is as likely to fall a prey as any other species and in fact
the confinement of several of these larve in a narrow compass usually ends in
the destruction of all of them but one.

HIBERNATION OF MOSQUITO LARVEE.

The continuous breeders, such as Anopheles and certain species of Culex, de-
velop while temperature conditions are favorable. Cold weather puts an end
to their activities and the larve are destroyed by the freezing over of the water,
or perhaps even before. However the larve of certain species normally hiber-
nate. This is the case with the pitcher-plant mosquito, Wyeomyia smithu;
the larva survive the complete freezing up of the water in the leaves of the plant
and complete their development the following season. The larve of a few other
species of the eastern United States hibernate regularly although they do not
withstand actual freezing; these larve remain dormant at the bottom during
cold weather. The tree-hole breeders Bancroftia signifer and Megarhinus sep-
tentrionalis hibernate as larvee and the same is probably true of Celodiazesis
barberi. Culex melanurus hibernates as mature larva. The larve live in spring-
holes in swamps or in the woods and the last brood appears very late in the
season. They remain at the bottom during cold weather, and do not produce the
imago until the following April or May.

All the foregoing species, with the exception of Wyeomyia smithi, may be
said to be rare and the larva are not generally in evidence. The observations of
Galli-Valerio and Rochaz de Jongh, in Switzerland, show that in Europe the
larve of certain species of mosquitoes hibernate in great numbers. Thus it
appears that the larve of Anopheles bifurcatus hibernate normally, remaining in
hiding among the leaves of water-cress (Nasturtium officinale) and other
aquatic plants. In the case of Culiseta annulatus, which was observed in a
water-barrel in an open field, even pupe continued to appear throughout the
winter at temperatures but little above freezing. These observers found that
larvee of Anopheles and Culex (?) survived in the thin layer of water between
two sheets of ice. These observers also found that the larve of Aédes nemorosus
occur during the winter in great numbers. On December 2, 1906, they found
great numbers of these larve: in an ice-covered puddle. This puddle had a depth
of five centimeters and an area of six square meters and they calculated that it
contained about 3,750,000 larvee. The larve in these puddles did not increase
in size during the winter; early in April they finally began to grow and trans-
formed to pupe towards the end of that month. From another observation by
these investigators it appears that such larve are hatched from eggs in mid-
winter. Thus they found on January 15, 1902, great numbers of very small
larve in a puddle thickly covered with ice; this puddle had been dry between
December 1 and January 1 and had, as the result of warm weather in early
January, afterward filled with snow-water. This last species, then, may be
classed with those species of Aédes the larve of which elsewhere appear in the
snow-water of early spring.
NATURAL ENEMIES.

The subject of the practical use of natural enemies of mosquitoes is considered
in the section of “ Remedies.” As virtually the only natural enemies of mos-
quitoes which can be used practically are fish, a rather full consideration of fish
will be found in that portion of this work, and is omitted in this present treat-
ment.

PLANTS.

At least two groups of herbaceous plants contain mosquito destroyers. The
bladderworts (Lentibulariacee) of the genus Utricularia, living in water, have
little bladders which trap small aquatic animals. The bladders have each a
valve-like door through which the animals enter when looking for food or when
trying to escape from their natural enemies. Darwin, in his work on insectiv-
orous plants, cites observations made by Mrs. Treat in New Jersey with Utric-
ularia clandestina. It was found that larve, probably those of mosquitoes,
when “ feeding near the entrance, are pretty certain to run their heads into the
net, whence there is no retreat. . . .” Fully nine out of every ten bladders con-
tained these larve or their remains. The species which grow in stagnant waters
have the most effective bladders. Mosquito larve inhabiting stagnant pools in
which the Utricularia grows are quite often entrapped in this way.

Recently J. H. Hart has kept under observation a species of Utricularia which
occurs in pools at the Pitch Lake in the island of Trinidad. He found dead
mosquito larve in the bladders and also newly caught ones struggling for free-
dom which afterwards succumbed. Eysell gives photographic reproductions of
Utricularia with mosquito larve in the bladders.

Ernst Krause * has called attention to the presence of Utricularia, in Brazil,
in the water accumulations between the bases of the leaves of bromeliaceous
plants, and as these water accumulations have since been shown to be fertile
breeding-places for certain species of mosquitoes, it is very probable that the
Utricularia here exercises a certain degree of mosquito control.

Another Brazilian bladderwort, Genlisea ornata, is said by Dr. Adolf Eysell
to capture mosquito larvee. He compares the tubular leaves of this plant to an
eel-trap.

According to the same author a member of the sundew family (Droseracee),
which grows submerged, captures mosquito larve. This is the Aldrovanda
vesiculosa of southern Europe and the adjacent warm countries, the leaves of
which have a structure and function similar to that of the well-known Venus’s
fly-trap (Dionea muscipula), its leaves closing quickly upon any insect that
touches them.

 

* Die Schutzmittel der Bltithen gegen unberufene Giste (Kosmos, 1887, vol. 1, p. 80).
156
PUBLICATION 169 PLATE IV

 

1. Heliconia champneiana Griggs. Eastern Guatemala.

 

2. Bromeliads. Cordoba, Mexico.
PLATE V

PUBLICATION 159

‘shay plop y

‘eIspueliyT o4ydidg

%

‘eeulayenyy uslojseq

‘sObtay euelaudweys eiuosay

ok

 
wo

PUBLICATION 159

 

1.

2.

Flower-spike of Calathea. Eastern Guatemala.

Bromeliaceous plant on trunk of royal palm. Porto Rico.

PLATE VI
ENTOMOPHTHORA 157

FUNGI AND BACTERIA.

Thaxter has recorded attacks on adult mosquitoes by the fungus known as
Entomophthora spherosperma. It reaches Diptera generally, but is especially
noticeable with the mosquitoes. Another fungus (EZ mpusa culicis) also destroys
mosquitoes in both Europe and America. Thaxter also states that Empusa
papillata destroys small gnats (probably mosquitoes among them). The eggs of
Psorophora howardu were found in the summer of 1901 to be covered with a
fungous growth which has been determined by Mrs. F. W. Patterson, of the U.
8. Department of Agriculture, to belong to the genus Polyscytalum.

A most interesting instance of the destruction of mosquitoes by Entomoph-
thora is described by Mr. R. H. Pettit in Special Bulletin No. 17 of the Michigan
Agricultural Experiment Station (see pl. VII, fig. 2).

“On August 5, Mr. Barlow found a number of adult mosquitoes killed by a
fungus, Hntomophthora sp. nov. They were very numerous on the margins of
one of the pools in the north woods, sometimes almost covering the soil and the
pieces of bark to which they clung. Some were just killed and showed little, if
any, external growth, and some were covered with a dense dull white growth.
All were within a few inches of the water and all faced away from it. Imagine
thousands of mosquitoes all headed away from the water as if they were trying
to get away from it.

“Tt would seem that the effect of the disease is to draw the affected insects
to the water, possibly by creating a thirst, after slaking which the insects, in
trying to retreat, are caught and stopped in their course by numerous rhizoids
or anchor ropes which are sent out by the fungus in the body to fasten the victim
permanently to the place where its ill luck overtakes it. Unfortunately for the
mosquito host, the diseased individuals die just in the right place to infect their
fellows as they go to the pool to drink or to lay eggs. This is a case where the
fungus seems to influence the host in such a way as to lead to the spread of the
disease. Similar impulses seem to be induced in the case of other species—the
Sporotrichum that is used against chinch-bugs seems to impel the diseased in-
dividuals to hide under clods or in other moist and protected places, just the
places where the young bugs come to shed their skins or to molt. This is of
course the best possible way to spread the disease. Then, too, in the case of the
common grasshopper disease, Zmpusa grylli, the dying hoppers are impelled to
climb to the tops of weeds and plants, and as the fungus throws its spores to some
distance, there is a good chance that some of them will fall on the bodies of other
grasshoppers.

“The appearance of the mosquito fungus is quite characteristic. The entire
body is swollen and covered with a dull white growth, sometimes almost
plumbeus. The body is fastened down by many slender brownish ropes. A
microscopic examination shows the growth to be made up of fine threads
(mycelium) bearing spores at their distal extremities. These threads are
usually simple, though sometimes bearing a few short branches. They are
septate at long intervals, granular, and contain vacuoles. The spores are lunate,
bluntly rounded at both ends. In size they measure about 50 microns long by
13 in diameter, some being as long as 55 microns and a few as short as 28
microns. They are finely granular, with oil globules usually near the ends. In
a single specimen large numbers of resting spores were found. In this case the
mycelium had largely disappeared. The resting spores were spherical, hyaline,
with many small translucent interior globules. They measured from 40 to 44
microns in diameter.
158 MOSQUITOES OF NORTH AMERICA

“The fungus also was found at the same time on several specimens of Mus-
cide, on a Chironomid, and on Diplaz, probably D. rubicundala. Attempts were
made to introduce the disease into new regions, but with little success. In the
laboratory, a large piece of bark bearing mosquitoes killed by the disease was
placed in a cage with many mosquito larve and pups. A few adults died after
emerging but not nearly all of them.

“ On August 7, a number of pieces of bark covered with mosquitoes killed by
the fungus, were placed on the margins of a pool in the river woods. The dis-
ease had not previously appeared in that section. On August 13 a few dead
mosquitoes were found near the place where the infection was made. On August
23, the disease was widespread throughout these woods.”

Marchoux, Salimbeni and Simond found that in Brazil the yellow-fever mos-
quito (Aédes calopus) was the bearer of several fungi. These fungi they found
to be very abundant at certain seasons of the year. These parasites not only
invade the digestive tract but also the body-cavity, in that case causing the mos-

quito’s death.

Perroncito found a bacterial parasite in Anopheles in Italy. This parasite
proved pathogenic, in fact it was the mortality it caused among mosquitoes that
led to its discovery. The parasite infests the larve and finally destroys the mos-
quito soon after it has transformed to adult.

Dyé, in 1904, in an excellent summary on the parasites of mosquitoes, dis-
cussed the yeasts found in mosquitoes as follows:

“We ought to give some words to the yeasts found by several authors in
mosquitoes.

“In October, 1900, Laveran announced a case of an yeast parasitic on Culi-
cide. This author has observed, in sections of Anopheles maculipennis, the ex-
istence of an yeast in the ceelomic cavity of mosquitoes coming from Rio-Tinto
(Spain) ; they had sucked malarial blood and had been well preserved in abso-
lute alcohol. According to Laveran this yeast presented the appearance of
minute ovate elements, measuring from 2 to 5 win length; a certain number of
these cells had at one extremity a small bud; each one of them possessed a
nucleus which was readily stained by the process of Heidenhain.

“ The greater part of the yeast cells are free in the coelomic cavity, or they are
grouped in small masses. In a number of longitudinal sections of these
Anopheles Laveran saw clearly that this yeast passes through the epithelium of
the walls of the digestive tube and falls into the ccelomic cavity.

“This yeast appears to be pathogenic for the mosquito; in fact, following the
observations of Laveran, Dr. Macdonald of Rio-Tinto investigated systematically
these small cell-elements which he succeeded in finding again. He noted, more-
over, that the larvee of Anopheles die rapidly at the season of the year at which
one finds the Anopheles infested by the yeast described by Laveran. Hence it
is probable that the yeast is transmitted from the larva to the adult insect, as in
the case of the parasitic fungi of Culicide observed by Perroncito.

“ Marchoux, Salimbeni and Simond also have observed yeasts in most of the
Stegomyia calopus which they had occasion to examine in the course of their in-
vestigations'on yellow fever. They found them particularly in mosquitoes dis-
sected soon after their emergence: they exist in abundance, especially in the
ceelom of the mosquitoes, in individuals fed with honey, with fruits and with
sweet substances. These authors note that these yeasts differ according to the
character of the food of the insect.
PUBLICATION 159 PLATE VII

 

1. Anopheles and Culex larvee in natural position in water.

 

2, Adult mosquitoes destroyed by fungus.
HAMOSPORIDIA 159

“ Contrarily to the fungi, announced previously by the same authors, these
yeasts do not become pathogenic to the culicids; neither can one, according to
them, attribute any réle whatever in the aptitude of Stegomyia calopus for
transmitting yellow fever.

“ Nevertheless the study of these yeasts is not devoid of interest : the spherical
or irregular masses formed by these yeasts, which one encounters in the large
air-sac of the culicid, may be easily taken, upon superficial examination, for
sporozoans, and the authors are not far from supposing, as we shall see farther
on, that these yeasts were taken by the Americans Parker, Beyer and Pothier,
for one of the stages of the parasite which they described under the name
Myzococcidium stegomyie. It is well to indicate, now, the possible errors of
interpretation to which the encountering of these yeasts, parasites of culicids,
can give place.

“ Schaudinn, in his remarkable work, interprets in a wholly individual man-
ner the réle of these yeasts, which he nearly always found in the diverticula of the
stomach (air-sac, sucking stomach, food reservoir) of the numerous culicids
which he dissected in the course of his beautiful researches. According to him
these yeasts have a purely physiological réle: by his investigations he has been
led to conclude that the irritating effect of the bite of Culex is due, not alone,
as it had been thought up to now, to the saliva secreted by the salivary glands,
but as well to the combined action of gas and diverse products, secreted by the
yeasts of the cesophageal diverticula. We will not follow the author in his very
concise demonstration of this réle of the yeast parasites in any physiological way ;
we have only to mention this original interpretation in passing, which shows us
how much all these questions of the parasites of culicids need to be seriously
studied. We see in fact, on the subject of these yeasts of the stomach of the
mosquito, three authors, studying them successively in different countries,
Schaudinn in Germany, Parker, Beyer and Pothier in Mexico, Marchoux,
Salimbeni and Simond in Brazil, and each one of them attributing a totally
different interpretation from the viewpoint of their parasitic réle.”

ANIMALS.

PROTOZOA.

Parasites of mosquitoes belonging to the Sporozoa and Flagellata have been
described by many authors. Among the Sporozoa are Myxosporidia, Hemo-
sporidia and Gregarinez. To the Hemosporidia belong the malarial and other
blood parasites of mammals and of birds. These are grouped in the family Plas-
modide and, as is well known, have a life-cycle which necessitates two hosts. The
agamic phase is passed in the blood of a vertebrate, the sexual phase in some
blood-sucking insect. These parasites are discussed in a later chapter, in con-
nection with malaria (p. 188). A nearly related group of Hemosporidia is the
family Hemogregarinide, a large proportion of which live in cold-blooded
animals (reptiles, batrachians and fishes) but also some in warm-blooded
animals (mammals and birds). It was in a species of this group, an Hemopro-
teus from the crow, that MacCallum was the first to prove the existence of sexual
phases in the Hemosporidia. Several Hemogregarinide are known to be
transmitted by mosquitoes. According to Schaudinn, Hemoproteus noctue, a
blood-parasite of owls, is transmitted by Culex pipiens. Another species,
Hemoproteus danilewskyi, and probably still other species, all living in the blood
160 MOSQUITOES OF NORTH AMERICA

of birds, conjugate and undergo sporogeny in mosquitoes. Before leaving these
blood-parasites it should be stated, however, that Dr. Fritz Schaudinn, in 1904,
expressed his belief that the parasite of malaria and also a trypanosome and a
spirochete might be hereditary in mosquitoes.

A spirochete was found to be an abundant parasite of mosquito larve by
Jaffé. It was described by him as Spirocheta culicis and is a relatively large
species, its length being from 10-20 microns. It occurs in the digestive tract
of the larva of an undetermined mosquito; in the vicinity of Berlin as many as
90 per cent of the larve were found infested. Very rarely the parasite was also
found in the imago, in the malpighian tubes. Its mode of reproduction is un-
known. The Sergents have found a similar organism in the larva of Anopheles
maculipennis in Algeria. Patton has determined that in India Spirocheta
occurs in mosquitoes in great numbers.

The Gregarinz are perhaps the most abundant protozoan parasites of insects.
They have been observed as parasites of mosquitoes by various authors. Ronald
Ross found gregarines in mosquito larvee at Secunderabad. Léger and Duboscq,
in Corsica, found a gregarine, which they assign to Diplocystis, in a mosquito
larva. The French investigators at Rio de Janeiro found gregarines in adult
Aédes calopus.

The French Commission at Rio de Janeiro, in its first memoir, gave a descrip-
tion of a microsporidian parasite of the yellow-fever mosquito which they
called Nosema stegomyie and frequently met with in this mosquito. In their
early researches the manner by which the mosquito becomes infected with this
parasite escaped them, but later they determined that the ordinary method is by
heredity, and this is stated in their second memoir, published in the Annals of
the Pasteur Institute, vol. 20, January, 1906. They show that with females
strongly infected with Nosema these reach the ovary and penetrate the eggs.
The egg parasitized in this way does not always die, and when it develops with
the spores in its interior it gives birth to an infested larva. Larve carrying the
parasite are easily recognized from the beginning of their development by a
microscopical examination. The parasite attacks particularly the transparent
vesicles situated near the anus, and in the interior of these vesicles they can be
distinguished either in the developing stage or the sporulating stage. Later the
digestive tube and the other organs are infected, and the larva is killed by the
development of the parasite. The mortality of larve brought about by the
parasite appeared to be considerable, but there was almost none with the perfect
insect. The investigators were able to bring about a direct infection of larve
by taking the spores of the Nosema from other larve or from adult mosquitoes
and mixing them with their food. They remark that this is not surprising, since
with Lepidoptera, parasites of the same group are easily transmissible to cater-
pillars by the ingestion of spores, while hereditary transmission occurs at the
same time. The occurrence of this parasite in the yellow-fever mosquito has
no relation with the transmission of yellow fever; but the investigators thought
the knowledge of its hereditary propagation none the less interesting, and it
induced them to carry out studies concerning the possibility of the hereditary
HYDRA AND MOSQUITO LARV 161

transmission of the organism of yellow fever. These are discussed in our
section on yellow fever.

Various flagellate Protozoa have been reported as parasites of mosquitoes.
These forms do not require an intermediate host. They may be transmitted
hereditarily by breaking through the digestive tract and, invading the body-
cavity, entering the eggs of the insect. One of these forms has been described
by Léger as Crithidia fasciculata, as an intestinal parasite in Anopheles maculi-
pennis in France. Novy, MacNeal and Torrey report the same form from Culez
in Michigan. The brothers Sergent have described a form of Herpetomonas
(H. algeriense) from females of Culex pipiens and Aédes calopus. Ronald
Ross, Chatterjee, Léger, Patton and Stephens and Christophers have found
similar parasites in mosquitoes. A form described by Novy, MacNeal and
Torrey from various mosquitoes occurring about Ann Arbor, Michigan, as
Trypanosoma culicis is now referred to the same genus. There appears to be
some reason to believe that the genera Herpetomonas and Crithidia represent
merely different phases of the same organisms and that the same forms have been
described in both genera.

Giles, in India, found a stalked infusorian attached in numbers to mosquito
larvee. In the second edition of his “ Gnats or Mosquitoes,” p. 151, he says:

“T have repeatedly found every Jarva in a pool simply covered by these para-
sites, which lie crowded together in enormous numbers, attaching themselves
especially to the softer parts of the integments, such as the angles between the
anal tubercles, and the soft membranes between the segments. Larve affected
in this way have a peculiar, slimy appearance, and seldom appear healthy,
though it is difficult to see how these ecto-parasites can be harmful, unless it
may be that being, at the very least, greedy mess-mates, they may appropriate to
themselves an undue share of the food that would otherwise fall to the share of
their hosts. Nevertheless, I strongly suspect that they may be the cause of the
inexplicable disappearance of larve, already alluded to, from situations where
they were just before present in abundance.”

Vorticellids have also been often found upon mosquito larve in this country.
H. P. Johnson, in an appendix to Smith’s report for 1902, states that he fre-
quently found beautiful clusters of these creatures on the thorax, abdomen, and
even the head of the larve of Culex pipiens. He states that they may be so
abundant as to give the thorax especially a whitish gelatinous appearance to the
naked eye. He believes that it is unlikely that these vorticellids do the larve
any harm, and that the latter simply afford them an attachment and transpor-
tation ; possibly also food, brought by the vortex which the mosquito larva creates
in the water. In fact vorticelle are very common on larve in open pools. The
only harm we ever saw done by them was in the case of an Anopheles larva
observed by one of us (Dyar) ; this was so loaded with Vorticella that it could
not turn its head to feed properly and eventually died.

OTHER LOWER ANIMALS.

The common fresh-water hydras (Hydra viridis and Hydra fusca) will de-
stroy mosquito larve that come within reach of their tentacles. One of us
162 MOSQUITOES OF NORTH AMERICA

(Dyar) has seen a Hydra, accidentally introduced into a breeding-jar, kill a
mosquito larva. When Hydra is abundant, as it sometimes is in ditches and
small ponds, it may become to some extent a check upon mosquitoes.

VERMES.

Martirano has described a minute trematode (Agamodistomum martiranot
Stiles, 1903) found in the body-cavity of Anopheles maculipennis in Italy.
Grassi, in his “ Studi di uno zoologo sulla malaria” (edit. 1901, p. 197 ) states
that both in the pupa and the imago of Anopheles a trematode is found encysted,
and most likely this is identical with the form observed by Martirano. Since
then these “ Distomum ” forms have been further studied. They have been most
intelligently discussed in a recent paper by Alessandrini, who throws some light
on their life-cycle. He believes that these distomi are the larval form of
Lecithodendrium ascidia (v. Beneden), a common parasite of the European bat
(Pipistrella ewropa@i). The bats are infected by eating mosquitoes which con-
tain the Distomum encysted ; the mosquito larve become infected in turn from
the feces of the bat, containing Distomum eggs, being dropped into the water.
The eggs hatch in the water and the larve of the Distomum enter a mosquito
larva and become encysted. These distomi are usually found in cysts on the
walls of the stomach or esophagus of the imago, but sometimes they occur free
in the body-cavity. Alessandrini thinks that the Distomum described from
Anopheles by Schoo is the same as that of Martirano. On the other hand, he
considers a Distomum found in Anopheles by Ruge to be the larva of a form
(Distomum globiporum) described much earlier by Linstrow from a snail
(Limnea ovata) and which becomes the intestinal parasite of a fish.

Nematode parasites of mosquitoes were observed in Europe by Stiles as early
as 1889 and were at that time already known to Professor Leuckart. However,
no record of them appeared until the same or a similar form was discovered in
this country, in 1902, by Dr. J. B. Smith. This parasite was described by Dr.
Stiles as Agamomermis culicis. In this connection Dr. Stiles discussed the
European forms as follows:

“In the summer of 1889 I collected a number of specimens of Agamomermis
sp. from mosquitoes of the species Culex nemoralis taken in the vicinity of
Leipzig, Saxony. Whether they were identical with the present form I am un-
able to state. The interesting fact may be mentioned, however, that the Leipzig
Agamomermis was decidedly injurious to the mosquitoes. It was found in the
abdominal cavity of larve, pupx, and adults, so that infection must have taken
place in the water, namely, in the larval and pupal stages of the Culex. The
infested insects were very sluggish in their movements and could usually be
easily recognized as diseased. Many of them died from the effects of the para-
site, and the ovaries of infected females were underdeveloped. Professor
Leuckart informed me at that time that he had frequently found Culez
nemoralis infected with this worm, and that during the years that the worms
were most common the mosquitoes seemed to be less numerous.”

Agamomermis was first found by Dr. John B. Smith in the course of his early
New Jersey work, while examining the females of Aédes sollicitans, in order to
determine the development of the ovaries. He saw a strange enlargement of
AGAMOMERMIS 163

the alimentary canal, and on one occasion, tearing the abdomen in two, he
found that this enlargement contained two worms. These were the types of
Stiles’s Agamomermis. In 1903, examining a large series of sollicitans, Smith
found a considerable number of adults infested by these worms, and from that
time on he made careful examinations of all material that came into his labora-
tory. The result was that every collection, from the Raritan River to Cape
May, was found to be more or less parasitized. None, however, were found on
the Newark or Elizabeth marshes. The records made by Mr. Viereck at Cape
May, and published in Smith’s report on the mosquitoes of New Jersey, al-
though incomplete as omitting the month of August, are very interesting in
showing the proportion of infestation :

** Date. Number of specimens taken. Number parasitized.
June 25 113 3
July 1 148 15

“« 10 151 88

2 137 10

« 31 309 112
Sept. 13 100 50

“ 14 100 39

NY U7 16

“« 18 62 2

21 100 8

«22 100 1

«25 82 2”

In Doctor Smith’s opinion, this roundworm is a very material check to the
multiplication of Aédes sollicitans, for in no case where a parasitized specimen
was examined were the ovaries developed. Several of the worms will sometimes
occur in a single adult mosquito, completely filling the body-cavity. As abun-
dant, however, as the parasites were they did not reduce the mosquitoes appre-
ciably even in those localities where they were most abundant. But it must be
remembered that any such reduction would not become apparent until a later
generation of the mosquitoes. The life of the adult is probably shortened to
some extent by the parasite, which does not, however, prevent migration, since
parasitized mosquitoes were taken far inland. Neither does the presence of the
parasites prevent the mosquitoes from feeding, for Doctor Smith killed infested
specimens that had actually bitten him. In fact, he sat for an hour one after-
noon at Anglesea, capturing such specimens as came to bite, and found that
nearly or quite one-half were infested.

Doctor Smith also records the fact that in 1902 one of his assistants, Dr. H.
P, Johnson, found the young of an intestinal worm in an Anopheles larva.

E. Gendre has recently found a similar larval nematode parasite, at Labé in
French Guinea, infesting the larve of the yellow-fever mosquito (Aédes calo-
pus). The worms were always found in pairs, one large and one small, and in-
habited the general body-cavity of the mosquito larva, rolled up in the thorax.
The mosquito larve, while they were growing, did not appear to suffer from the
presence of the parasites but retained their appetite and vivacity. No injurious

12
164 MOSQUITOES OF NORTH AMERICA

effect was apparent until the larve were about to pupate; then the worms, hav-
ing probably completed their parasitic stage in the mosquito, leave the host.
They break forth from the posterior end of the body by perforating the mem-
brane surrounding the anus. The larger worm leaves first, the smaller follow-
ing a little later, and the mosquito larva dies as a result of the injuries. The
Mermis larve died some hours after leaving their host. In one catch all the
mosquito larvee were infested, but parasitized lots of larvee were rare ; only two
out of 26 lots were infested and these came from water in trees. No parasites
could be found in adult Aédes calopus and Gendre considered the infestation
accidental.
INSECT ENEMIES.

Many insects and nearly all of the predatory aquatic forms that are able to
master mosquito larvae, will feed upon them and they form an important article
in the diet of many species. Most of these carnivorous insects, however, are
not prolific breeders, and they seldom deposit their eggs except in rather per-
manent pools; as a consequence their importance as mosquito destroyers is
not so great, though nevertheless considerable. Mosquitoes breed practically
unmolested in artificial receptacles for rain-water and in transient pools.

The larva of the predatory water-beetles of the families Dytiscide and Hydro-
philide eat many mosquito larve, although from their great activity these often
escape and the beetle larvee derive the greater part of their subsistence from
other forms.

Dr. W. E. Britton, of New Haven, Conn., who has made careful study of the
mosquito problem in Connecticut, has found that the larva of Hydrophilus
obtusatus Say (Schwarz det.) is one of the important natural enemies of mos-
quito larve in the vicinity of New Haven.

One of us (Howard) has recorded an observation in the course of which he
took a half gallon of water from a stagnant pool which was teeming with aquatic
insects, including hundreds of mosquito larve. Among these insects were three
Hydrophilid larve and in the course of a week these three larve devoured practi-
cally all of the other animal life in the jar in which the half gallon of stagnant
water had been placed.

Dr. J. B. Smith thinks that the larve of the Dytiscide are among the greatest
enemies of mosquitoes. He is inclined to attribute the comparative freedom
from mosquitoes of the hilly section of New Jersey very largely to these insects,
and he quotes an interesting observation by Doctor Johnson in support of this
conclusion. He also notes an observation by Mr. Viereck in which one good-
sized dytiscid larva was seen to devour 434 mosquito larvee in two days. Galli-
Valerio and Rochaz de Jongh found that an adult water-beetle, Dytiscus mar-
ginalis, although it had been previously fed with meat, destroyed great numbers
of mosquito larvee and pupe. Dr. Adolf Eysell states that a single, nearly full-
grown, larva of Acilius sulcatus destroyed more than forty mosquito larve over
night.

Dr. Smith states that the Gyrinide or so-called “ whirligig beetles,” which live
nearly wholly at the surface of the water, are great destroyers of mosquito larve ;
DRAGON FLIES AND MOSQUITOES 165

he asserts that “no Anopheles larva has a chance in any bit of water inhabited
by them. .. . Their surface habit and their tendency to get near the edges
make them especially dangerous to Anopheles larvee, which absolutely fail to
maintain themselves within the range of these beetles.” The larve of the
Gyrinide are also predaceous but live at the bottom and no observations of their
preying upon mosquito larva have come to hand.

Dr. Eysell dwells upon the efficiency of aquatic Hemiptera as mosquito de-
stroyers. He states that of the forms living beneath the water Nepa, Ranatra,
Naucoris, Notonecta and Coriza destroy great numbers of mosquito larve. The
forms living upon the water-surface, like Limnobates and Hydrometra, destroy
emerging imagos or females in the act of depositing eggs.

In German New Guinea, Drs. Dempwolff and Wendland, in the course of
their malaria work, found that waters which contained many Notonecta har-
bored no mosquito larve. This led them to introduce these insects into the 17
water-tanks of-an European settlement with the result that within a week the
mosquito larve had all disappeared from the tanks and the number of mosquitoes
inside the houses was considerably diminished. Further experiments with
Notonecta, initiated with mosquito-breeding pools, gave no practical results on
account of the rapid drying up of the pools.

Doctor Smith also gives observations upon several aquatic bugs, indicating
that Notonecta, Nepa, and Ranatra are effective enemies of mosquito larve but
that, owing to the fact that they occur chiefly in permanent waters, their use-
fulness is restricted. He quotes an interesting observation by Mr. Viereck, as
follows:

“The early stages of Ranatra fusca were destructive to wrigglers. With
their raptorial legs they nip the larva near the breathing tube, then either drop
or suck it. Quite a number were nipped and dropped, and, once dropped, they
rose no more. Pupe, both of Anopheles and Culex, were expert in evading the
grasp and were not readily caught. In less than an hour three Ranatra killed
and sucked ninety-eight larve. It is a question whether Ranatra would be use-
ful in stagnant pools, because the specimens used in the experiment could only
be found in the clear water of a lily pond where, no doubt, they controlled the
Anopheles; but when put into the stagnant water which sollicitans inhabits,
they died.”

Dragon flies feed upon flying mosquitoes, and their larvee feed upon mosquito
larve and pupe. This propensity of dragon flies is so well known that in some
sections of the country they are popularly termed mosquito hawks. The late
Dr. R. H. Lamborn, of New York City, was so impressed with the voracity of
dragon flies, from observations made while engaged in railroad building in the
swampy forests around the head of Lake Superior, that, in 1889, he offered three
prizes for the best essays on the mosquito and the house fly. These essays were
to include observations and original investigations regarding methods of de-
stroying the mosquito and the house fly, observations and experiments to best
accomplish the artificial multiplication of dragon flies to breed them in large
numbers, and to include an estimate of the cost of producing them by the
thousand. How feasible his plan seemed, not only to himself, but even to as
166 MOSQUITOES OF NORTH AMERICA

experienced an entomologist as Doctor P. R. Uhler, of Baltimore, appears in
the following letter from Doctor Uhler to Doctor Lamborn, written in 1889,
just before the prizes were offered :

“Permit me to say that you have taken hold of one of the hobbies of my
young manhood, in which I have never ceased to take an interest, and that is
the development of the Odonata in our rivers and marsh ditches to such an ex-
tent as to greatly reduce the number of mosquito larvae, as well as those of other
pestiferous Diptera which develop in such places.

“ How extensively this can be done I do not know; but as I have raised all the
common forms of our Atlantic coastal plain region, I know that the dragon fly
larvee can be reared in vast numbers.

“Of course, you know that each locality supports its own species, and the
forms which develop in the brackish drains and pools near tide, where they are
covered twice each day by salt water, cannot flourish in fresh water. Accord-
ingly, for the littoral belt from Long Island to Beaufort, N. C., I would select
Diplax berenice, Libellula auripennis, and Mezothemis longipennis. For the
region next inland from this, multitudes of common species could be had, such
as Anax junius, A’schna heros, Libellula pulchella, L. luctuosa, L. semifasciata,
Plathemis trimaculata, and most of the species of Diplax. In the clear streams
which rush down from the hills, Cordulia, Epitheca, and Gomphus prevail. In
order to raise any of the species, Cyprinodonts and all other carnivorous fishes
will have to be excluded.

“T agree with you that the mosquito nuisance might be greatly lessened by
filling the mosquito breeding waters with the larve of dragon flies.

“T believe this might be done by securing vast numbers of the eggs of dragon
flies, protecting them until hatched, and then turning them loose in the waters
where the mosquitoes breed most abundantly.

“ Along the seacoast, however, most of the eggs and hibernating female mos-
quitoes might be exterminated by burning the grass, in early cold weather of
autumn, all over the marshes.

“ Permit me to say that I hope you will offer the prize, as stated in your letter,
and agitate the subject quite extensively.”

The letter is also of interest as indicating Doctor Uhler’s idea as to the most
valuable species.

The three prizes were awarded to Mrs. Carrie B. Aaron, of Philadelphia; Mr.
A. C. Weeks, of Brooklyn; and Mr. William Beutenmiiller, of New York City;
and were jointly published in a volume entitled “ Dragon Flies vs. Mosquitoes ”
(New York, 1890). The essays were all admirable and brought together a great
deal of useful information on the subject of mosquitoes and mosquito enemies ;
but they did not solve the problem of the commercial breeding of dragon flies
for the destruction of mosquitoes. .

In the course of these essays, no doubts were expressed as to the value of
dragon flies as natural enemies of mosquitoes, and in fact Mr. Beutenmiiller
quoted from an army correspondent a rather striking statement of observations
indicating their effectiveness. But Doctor John B. Smith concludes from his
observations that, not only do the adult dragon flies fail to lessen materially the
mosquito supply, but that the dragon-fly larve are as little entitled to credit for
effective work as are the adults. He points out that they are bottom feeders as
a rule, and usually below the range of “ culex,” while Anopheles is in no danger
PREDACEOUS MOSQUITO LARVH 167

from them. It may be mentioned, however, that one of us (Knab) has seen
agrionid larve come to the surface of the water and seize Culex larve.

We are of the opinion that dragon flies do destroy a great many mosquitoes.
While they show no preference for mosquitoes there seems to be, on the part of
adult dragon flies, a marked preference for Diptera; with their great rapidity
and activity, where mosquitoes are abundant, a considerable number must be
destroyed by them. This must be particularly true of the large crepuscular
species, such as Aschna, their time of activity coinciding with that of most
mosquitoes. Mr. Nathan Banks tells us that, at College Station, Texas, he has
observed a large dragon fly capturing flying insects in rapid succession, pre-
sumably mosquitoes, as a great many of these were flying about at the time. Mr.
McAtee, at Church’s Island, North Carolina, has seen a dragon fly (Hrythemis
simplicicollis) pick Anopheles quadrimaculatus off the weather-boarding of a
house.

Certain ephemerid larve are active destroyers of mosquito larve. Foley and
Yvernault found that in Algeria ephemerid larve are more efficient destroyers
of mosquito larve than Dytiscide.

Some very efficacious natural enemies of mosquitoes are to be found in the
family Culicide itself. The larve of Psorophora, Megarhinus, Lutzia and
Lesticocampa are voraciously carnivorous and even cannibalistic, while the
larger larvee of Anopheles will attack one another and the larve of other mos-
quitoes. In a lot of larve of Anopheles quadrimaculatus and A. punctipennis,
kept in the laboratory in a large battery jar for study by one of us, the larve
were noticed to disappear, and one morning nine heads were found of which the
bodies were gone. Nothing but mosquito larvee were in the jar. One larva was
noticed which looked as if it had two heads, but upon examination it was found
that the body of one had been almost devoured and the survivor was eating the
head which was all that was left of the victim. Several larvae: were found which
had been half eaten. The Anopheles larve were several times seen eating the
young Culex larve. The cannibalistic tendencies of Anopheles larve have been
noted repeatedly by a number of writers. The larve of certain species, having
a restricted habitat in the water in holes of trees and between the leaves of brome-
liads, are probably entirely predaceous.

Dr. Oswaldo Cruz, of Brazil, while on a visit to Washington, stated that in
Rio de Janeiro Lutzia bigotii is used practically to destroy the larvee of Aédes
calopus, The Lutzia larve are introduced into receptacles in which the calopus
breeds and soon destroy the larve of this dangerous insect.

The habits of Psorophora in the larval stage are such as to make them very
desirable inhabitants of stagnant pools. They have been frequently described,
but the series of observations made at the request of one of us by Dr. W. E.
Hinds, in the summer of 1901, and hitherto unpublished, will be of interest
here. The following extract from Doctor Hinds’ notes, treats of the feeding
methods of the larve:

“ August 16. A.M. Received a lot of Psorophora ciliata larve from W. P.
Seal, Delair, N. J. They came in a large quart bottle and with them were quite
168 MOSQUITOES OF NORTH AMERICA

a number of living Anopheles and Culex larve. The bottom of the bottle was
literally covered with heads, breathing tubes and decaying parts of the larve
which these big cannibals had destroyed on the way. There were no plants in
the bottle.

“ [TI] observed one Psorophora attack another. It seized its victim in the thin
tissue which unites the breathing tube to the body. With its own breathing tube
at the surface, it held its victim firmly in spite of its wiggling in its struggle to
escape, keeping it always below the surface. Of course with its advantageous
hold it could quite easily keep its victim from getting a fresh supply of air and
thus it was drowned. I did not see that the victim made any attempt to bite its
captor, only wiggling violently. After several minutes it seemed to be nearly
dead, struggling occasionally and the valves at the end of the breathing tube
could be seen to frequently open and close in the water. When disturbed the
victor would now swim down with its prey, soon coming to the surface again
but never once losing its hold.

“ Another larva came up and proceeded to assist the victor, eating off all the
anal flaps of the victim. When disturbed again the second one let go but the
first one held on and was taken out in a watchglass, nearly all the water removed
therefrom, and examined under a compound microscope. It still held to the
same place, the mandibles working far into the mouth and carrying the tissues
with it but without appearing to masticate them. It was apparently sucking
the juices from the victim which was shrinking in size.

“ Another Psorophora was observed to take a 3/4 grown Culex larva by the
head and swallow it whole as a snake does a frog. The whole operation did not
take more than half a minute.

“The mouthparts are rarely moved except when attacking prey. Yesterday I
saw one Psorophora seize a piece of water plant and bite enough to pull it along
with it.

“T divided the Psorophora larve into three lots of 16 each in evaporating
dishes and from a bucket of standing water back of insectary, I procured a large
number of Culex larve which I put into the Psorophora dishes. Immediately
they seized upon the Culex and 8 or 10 at one time had Culex larve part way
down. In only one case out of many (probably 40-50) did I see a Culex seized
tail first. It took from 2 to 3 minutes to swallow the largest Culea larve and
from that to perhaps 20 seconds for very small ones.

“The method of catching is as follows: The Culex hang at the surface head
downward while breathing. Sometimes the Psorophora floats along in similar
position toward it, sometimes remains motionless till Culea comes within reach.
When they have reached a position so that Culex hangs almost directly over
the head of Psorophora, like a flash, before Culea has time to move, the Psoro-
phora turns its head (its mouth is on under side) and seizes Culex by the head
in a fatal grasp, pulling it under and, in spite of its victim’s struggles, quickly
swallowing it whole.

“T examined some excrement just as it came from one larva and found that
it was composed of the breathing tube and the two main tracheal tubes from the
body of the victim passed whole through the alimentary canal of the cannibal.
From these observations on eating whole larve it may be inferred that practically
all the heads and breathing tubes which strew the bottom of my jars by hun-
dreds, yes thousands, have passed through the alimentary canals of the Psoro-
phora larve.

“In the case of the Psorophora eating each other, the strongly chitinized
breathing tubes and the cylinder around the last segment are rejected as too
tough, but in the case previously observed this day fully 1/2 the length of the
body posteriorly has been thoroughly chewed up and the inner soft parts ab-
PUBLICATION 159 PLATE vill

 

1, 2. Larva of Chaoborus,

3. Larva of Corethra.
PREDACEOUS CHIRONOMID LARVZ 169

stracted without swallowing the chitinous epidermis. This specimen was kept
for hours in a few drops of water on a watchglass, for observation under the
microscope, and was very lively when put back with the others.”

The predaceous habits of Megarhinus larvee have been noted by observers in
both hemispheres. The feeding-habits of the larva of Megarhinus septentrio-
nalis, have been studied by Morgan and Cotton. Twenty-four larve of this
species were collected by Professor Morgan in a half-barrel of rain-water and
carried to his laboratory, where they were placed in beakers containing tap-
water, several larvee in each beaker. They were fed upon the larve of smaller
species, chiefly Aédes calopus and Culex sp. The observers stated that the
Megarhinus larve swallowed the smaller larve bodily, but when feeding upon
one another the victim was held in the strong mandibles and slowly devoured.
They made no effort to pursue their prey but remained quietly near the bottom
of the water until a smaller larva approached, when it was seized with a quick
movement and speedily devoured. No effort was apparently made to change the
hold, whether the prey was seized near the head, near the middle or posteriorly.
One Megarhinus was seen to seize a nearly mature larva of Culex salinarwus
near the middle, and without loosening its hold to swallow it gradually, the head
and tail disappearing together. When swallowing the prey head foremost, there
was much difficulty, and in one instance it took an hour to swallow one in this
way, whereas usually three or four minutes sufficed.

The larve of the culicid subfamily Corethine are predaceous and some of
them feed extensively upon mosquito larve. In northerly regions the larve of
Corethra (Mochlonyx auct.) appear simultaneously with those of Aédes in the
snow-water of early spring; they prey largely, if not altogether, on these and
must act as a check to some extent. The larve of Chaoborus (Corethra auct.,
Sayomyia Coq.) occur under more varied conditions and their food appears to
consist mostly of small crustacea; they do, however, feed upon mosquito larve
to some extent. Thus one of us (Knab) has found the larve of Chaoborus
punctipennis in a temporary puddle preying upon the larve of Culex pipiens.
Plate VIII, figs. 1-8, shows the larve of Chaoborus and Corethra.

The larva of another non-biting mosquito of this subfamily, Hucorethra
underwoodi, has been found by W. L. Underwood to feed upon the larve of other
mosquitoes, and this has been abundantly confirmed by other observers. On
one occasion Mr. Underwood found that fourteen of these larve ate over night
sixty out of seventy mosquito larve that had been placed with them. He says
(Popular Science Monthly, Sept., 1903, p. 466) : “ When eating the larve of
mosquitoes smaller than themselves, the victim is caught, shaken violently a
few times, and swallowed in a few seconds in very much the same way that a
pickerel would catch and swallow a smaller fish.”

The aquatic larve of many nemocerous Diptera are predaceous and doubtless
many of these capture mosquito larve along with other prey. The larve of
certain Chironomid, particularly those of the genus Tanypus and related
genera, have long been known to be predaceous. The digestive tract of certain
European species has been found to contain red coloring-matter, suggesting that
170 MOSQUITOES OF NORTH AMERICA

these larvee prey upon the small red worms known as Tubifex or upon the larvae
of Chironomus. One of us (Knab) found that larve of Tanypus dyari, acci-
dentally introduced into breeding-jars, were very destructive to mosquito larve.

A remarkable case is that of an adult fly preying upon mosquito larve. J.
Mitford Atkinson gives an account of Lispa sinensis Schiner, an Anthomyid fly,
which at Kennedy Town, Hongkong, was seen to be eating the larvee of mosqui-
toes. On stirring up the stagnant water crowds of larve were disturbed. “The
flies pounced down upon them and rapidly devoured larve almost as long as
their own bodies; at times they would fly away with the larve in their mouths.”
The flies were determined by Mr. E. E. Austen.

Dr. Paul Osterhout, of Bocas del Toro, Panama, has recently observed flies
of the family Dolichopodide, well known for their predaceous habits, to attack
mosquito larve in a similar manner. We quote the following from his letter to
the Surgeon-General of the Public Health and Marine Hospital Service: “A
short time ago, in passing through the outskirts of the town, I saw a large
swarm of small flies seemingly very much occupied about a small pool of water
standing in a wagon track (the track had been undisturbed for several days
from the appearance), so I stooped to see what the commotion was about and I
saw hundreds of these small flies and thousands of mosquito larve. J remained
for some time watching the commotion and saw several of the flies catch the
larve and drag them to the dry earth and devour them.”

D’Emerez de Charmoy, the Director of the Museum in the Island of Mauri-
tius, has made a study of the natural enemies of the malarial mosquitoes in
Mauritius. He has drawn up the following interesting table showing at a glance
the results of a series of experiments which he made to determine the relative
effectiveness of certain species of insects and of a small fish in destroying mos-
quito larve :

 

 

 

 

 

 

 

Least
Numberof 7
Number | larvee of span , eee
Enemies. of individ-] Anopheles/oy, Tovas| Pet
uals. | in the re- [Seg lervie| of larvre
ceptacle. hour: 5
Hours.
Be i pisnsnenes 3 By 16 <a ouiee cdl aay
er desjardinst.......... 2 ees ndifferent destruction.
Hh, daticus exclamationis.... 1 ie 3 12 Indifferent destruction.
a Date. aie aris q a : so Capture with difficulty.
Ranatra larvie......... ses 3 30 48
Larvee of Culex tigripes..... 4 12 aie 48
Cyprin doré (8% in. long).... 1 30 15 2 Quick destruction.

 

Various adult insects have been found to prey upon adult mosquitoes. Dragon
flies have already been mentioned and there is no doubt that mosquitoes furnish
their quota of the food captured by these insects while on the wing. In this
connection the crepuscular habits of certain species of dragon flies should be
noted.

In the Diptera the Empidide are well known to be predaceous, capturing other
insects upon the wing. Wahlberg, in an interesting paper on the mosquitoes of
WASPS CAPTURING MOSQUITOES 171

northernmost Sweden, records two species of Empidide (Hormopeza obliterata
and Tachydromia macula), and a species of Scatophagide (Cordilura hemor-
rhoidalis) as active enemies of mosquitoes. We give a free translation of his
interesting account:

“It is well known that when animals collect in large numbers—as for example
lemmings or grasshoppers migrating from one locality to another—they are
attacked by numerous predaceous enemies; the lemmings by foxes and birds
of prey—the grasshoppers by various birds. Similar conditions are found with
the enormous swarms of Culex, as well as with those of Simulia and Cera-
topogon.

“T have already communicated to this Academy my observations on one of
the predaceous enemies of mosquitoes, Tachydromia macula, which catches its
prey by the help of its specially adapted front legs.

“ Not less agile and voracious enemies of the mosquitoes are two other small
predaceous flies Cordilura hemorrhoidalis and Hormopeza obliterata, which
even come inside the tents of the Lapps in order to catch the mosquitoes there.

“ Of the Hormopeza, which Prof. Zetterstedt only found in one example and
of which Prof. Boheman has since found also but one male, I found in great
numbers of both sexes near the river Sidosjocki on the Ounastunturi mountain
while I visited a Lapp house there. I had first occasion to observe them inside
the house, where they flew about catching such gnats as had gained entrance in
spite of the continuous smoke. As I previously had noticed great swarms of
gnats outside, over the top of the cabin, I went out to seek the Hormopeza there
and found them in great numbers. They continued preying upon the gnats far
into the night and were found in company with the above mentioned Cordilura.”

Paul Combes has observed that in the island of Anticosti freshly emerged
mosquitoes were attacked and killed by another blood-sucking dipteron, Simu-
lium, which is a great plague in that region.

A male of a very common and widely distributed predaceous fly, Scatophaga
stercorarius has been found by Claude Morley sucking one of the non-biting mos-
quitoes (Corethine) and presumably does not discriminate against the biting
ones.

Two species of wasps have been observed to prey upon adult mosquitoes.

Charles Ferton, in the Annals of the Entomological Society of France for
1901 (p. 113), states that, at Bonifacio in Corsica, a specimen of Crabro quadri-
maculatus was captured carrying an incompletely paralyzed male of Culex to
its nest, and states that it is probable that this little wasp also captures Anoph-
eles, and so merits esteem in a malarial country.

Mr. H. J. Browne, of Washington, at Calapatch Island, 70 miles south of
Batabano, Cuba, and 30 miles east of the Isle of Pines, found the large wasp,
Monedula signata, in great numbers. They seemed to make their practical diet
on the yellow-fever mosquito, which they seized upon the wing and devoured in
large numbers. Mr. Browne says that he has seen one of these wasps seize and
devour upon the wing 20 mosquitoes in the space of five minutes. Bates, in his
“ Naturalist on the River Amazon,” states that this particular wasp is an enemy
of the motuca fly (a tabanid, Lepiselaga), and that one of the wasps captured a
motuca from his (Bates’) neck and carried it off to its burrow.
172 MOSQUITOES OF NORTH AMERICA

Recently Mr. W. L. McAtee, of the U. 8. Biological Survey, while in Arkansas,
found the curious “thread bug,” which is often common about farm houses,
capturing mosquitoes and has furnished us the following note:

“ There were 3 or 4 Emesa longipes on each window screen of the house in
which I stayed at Big Lake, Ark. Mosquitoes would accumulate on these screens
each evening and be eaten the next day by the Hmesa. I picked up some
Anopheles quadrimaculatus that had been sucked dry by the bugs.”

Undoubtedly many other predaceous insects capture adult mosquitoes and
Eysell mentions bugs (Hemiptera-heteroptera), locusts (Orthoptera), scorpion
flies (Panorpide), wasps and robber flies (Asilide), but we have seen no exact
observations on these forms in relation to mosquitoes.

MITES.

Certain acarids are frequently noticed attached to the bodies of adult mos-
quitoes. One of us (Howard) has quoted a letter from Mr. E. P. Salmon, of
Beloit, Wisconsin, in which it was stated that one of these mites attacks the mos-
quitoes of Madeline Island a few weeks after their appearance in June, and that
from the time the little red creature appears under the mosquito’s wings the
latter begins to lose its strength. “ After a few weeks, along toward the end of
July, the mosquito ceases to be very troublesome and seems to be fighting with
his parasite for his life.” The writer stated that the parasite is probably one of
the red mites found upon flies and particularly upon the common house fly.
Mosquitoes being aquatic insects, it was suggested that the mite observed by Mr.
Salmon might be one of the little water mites of the family Hydrachnide, but
that the mosquito issues from its pupa so rapidly that this was hardly likely
to be the case. It was suggested that it might be one of the Trombidiide, the
young of which may crawl upon the mosquito when it is at rest upon the plante
(Howard’s Mosquitoes, pp. 165-166).

Since that time a number of these mites have been sent in and others have
been examined by other observers. All have been found to be hydrachnids and
so far as known to us there is no exact record of the finding of a trombidiid on
a mosquito. Specimens of these mites taken from a mosquito at Kanawha Sta-
tion, W. Va., by Dr. A. D. Hopkins, have been determined by Mr. Nathan Banks
as larve of the hydrachnid genus Fylais. Larve of an Fylais have also been
determined by Mr. Banks upon mosquitoes from the Philippine Islands, sent in
by Dr. Clara 8. Ludlow. Other larval hydrachnids found upon mosquitoes have
been sent to us from the Great Slave Lake by Ernest Thompson Seton. We
have ourselves frequently found them and it may be stated, in a general way,
that their presence on mosquitoes is a common occurrence. Dyé, previously
cited, gives accounts of a number of instances in which larval hydrachnids have
been found upon adult mosquitoes in different parts of the world. These larve,
according to Blanchard, nourish themselves at the expense of the host, and in
certain cases undoubtedly bring about its rapid death. Interesting observations
upon one of these larval hydrachnids have been made by Sergent, in Algeria.
There he found that Anopheles maculipennis carried these hydrachnids in the
MITES ON MOSQUITOES 173

larval, pupal and adult condition. He showed that when the larva of Anopheles
molts in its transformation to pupa, the mite passes to the pupa, and when the

perfect insect is given out the hydrachnid leaves the skin of the pupa to attach
itself to the adult.

Dr. Aubrey Hodges, in the “ Journal of Tropical Medicine ” (1902, p. 300),
gives an interesting account of mites found upon Mansonioides and upon Anoph-
eles paludis in Uganda. He states that in certain places quite 50 per cent of
the mosquitoes were attacked and he found as many as nine parasites upon
one mosquito. He asserts that the color of the parasite depends upon the
nourishment of the host, and that they are red when attached to a mosquito
which has sucked blood. He thought that the mites injure the mosquitoes, the
latter becoming weakened and living only a few days in captivity.

It would seem from this statement by Doctor Hodges, as well as from the fact
that so many mosquitoes coming from Madagascar were found by Blanchard
to have mites attached to them, that in Africa there must be some genus or
genera, of hydrachnid mites, that more commonly attach themselves in the
larval condition to the larvee of mosquitoes than is the case in temperate regions.
This is the opinion of Mr. Banks, who thinks that the northern forms more com-
monly attach themselves to other aquatic insects.

In the course of his interesting observations on mosquitoes at Scott, Arkansas,
Mr. James K. Thibault, Jr., has studied this question of parasitic mites. He
writes as follows:

“More or less every adult specimen of certain species is found to be infested
by a red mite very similar in general appearance to those occasionally found on
house flies, though for the most part such will be the case only early in the
season—spring. The proportion of infested individuals among the various
species is very striking, Anopheles and Mansonia showing the greatest number
of infested individuals, likewise the greatest number of mites per mosquito.
The first Anopheles and Mansonia to hatch out show over ninety-five per cent of
infested specimens, and indeed it is well-nigh impossible to find a single speci-
men that is not parasitized. Culex abominator D. & K. probably comes next,
but in this case the mite is bluish-green—about the same shade as that seen in
Culex abominator itself when first hatched. This probably accounts for the
blue-green color of the otherwise red mite.

“T list the various species which I have found to be infested, placing those
showing the greatest percentage of infested individuals first in the list, and
so on in order:

“ Anopheles crucians Wied.; Anopheles quadrimaculatus Say; Anopheles
punctipennis Say; Mansonia perturbans Walk.; Culex abominator D. & K.;
Culex territans Walk. (rarely) ; Aédes triseriatus Say (only once) ; Megarhinus
septentrionalis D. & K. (rarely).

“ Nearly all of the above-named species hibernate as adults, and one might
be led to believe that there was some connection between this and the fact that
they are so often parasitized, but I do not think this is the case. I believe that
it is more probable that the mites attach themselves to the mosquitoes when the
latter are in the larval or pupal stage, perhaps both. I once found three larve
of Culex abominator all having mites upon them. These mites were of the
typical red color, whereas those found upon adult Culex abominator are in-
variably bluish green. This difference in color is, I believe, to be explained by
174 MOSQUITOES OF NORTH AMERICA

the fact that the larve of this mosquito are not green, even when found among
vegetation of that color until nearly full grown, after which, like the larve and
pupe of Anopheles quadrimaculatus, they may be bright grass-green. These
mites lived for several days on the larve, but when removed from them and
placed in water, they soon sank to the bottom and died. .

“Tt is possible that the bluish green mite of Culex abominator is a different
species, for I have never found them of this color on Anopheles quadrimaculatus ;
yet under similar circumstances the larve, pupe and freshly emerged adults of
this mosquito are also bright green. It is certainly very probable that this mite
destroys quite a good many mosquitoes, and it is unfortunate that they do not
extend their operations throughout the season instead of only the early part.

“ A good many species seem to be for the most part never or only very rarely
attacked at all.”

In considering the whole question of the effect of these mites it seems doubtful
whether they destroy adult mosquitoes. Mr. Banks gives as a result of his ob-
servations that mosquitoes that do carry mites do not seem to be inconvenienced
by them. The mites, he states, can not live long out of the water, and can never
complete their transformations. If extremely numerous their weight might
hinder the flight of a mosquito, or they might take enough nourishment from
the host to seriously weaken it. Mr. Banks’s observations have been made for
the most part in the vicinity of Washington, where this mite infestation is rare.

In their work on malaria in Algeria, the Sergents made a number of observa-
tions upon these parasitic mites. They found there that the mites seem to occur
only on Anopheles and never upon Culex or any other genus of mosquitoes.
Their specimens were examined by Trouessart, who found them to be hexapod
larve of hydrachnids which could not be determined in the larval condition
but which probably belonged to the genera Fylais, Hydrodroma, Hydryphantes,
or Diplodontus, whose larve are known to have parasitic habits but whose dis-
tinctive characters are too slightly marked to connect them with the adult forms.
Parasitized Anopheles were found by them from May to October, in the larval,
pupal and adult condition. They found nine larve, two pupe, twelve adult
females and five adult males of Anopheles maculipennis so parasitized on the
plain of Mitidja and in the valleys of Kabylia. They were able to follow in the
laboratory the development of most of the parasitized larvee and these underwent
their metamorphoses normally and did not seem to be inconvenienced by the
hydrachnids. When the larva transformed to pupa the hydrachnids passed
from the larval skin onto the pupa, and when the adult issued the mites left
the nymphal skin and attached themselves to the winged insect. In their ex-
perience these parasites are rarely single, and as many as ten were found upon
the same insect. With the larve and adults they were found upon the abdomen ;
with the pupe upon the dorsal portion, near the point where the skin splits to
allow the adult to issue. They were attached to the host by their beaks and were
observed to grow. The Sergents tried an experiment to see whether the larval
hydrachnid can change its host. A female of Anopheles algeriensis was put into
the same cage with two specimens of Anopheles maculipennis which carried
numerous mites. The next day, upon the abdomen of the Anopheles algeriensis,
found dead, they found a mite. From this experiment they concluded that these
SPIDERS AND MOSQUITOES 175

larval hydrachnids can change their host, but that the mites are not especially
harmful to the mosquitoes. In their rearings, larve, pups and adults most
abundantly parasitized did not die any more frequently than unparasitized in-
dividuals which they kept as checks. Doctor Trouessart informed them that he
also believed that the well-known parasitization of aquatic insects in general by
hydrachnids does not appear to be burdensome.

SPIDERS.

There is no doubt that many mosquitoes are destroyed by spiders. It is a
matter of frequent observation to find mosquitoes in spider webs. Dr. H. C.
McCook, a well-known writer on spiders, has written the following paragraph
on this subject:

“But do the spiders have a special taste for mosquitoes? it may be asked.
They take what comes to them, and when mosquitoes are abundant mosquitoes
are taken. I have counted in an orb weaver’s snare, spun upon the railing of the
long bridge over Deal Lake, New Jersey, thirty-eight mosquitoes at one time
hanging entangled upon the viscid spirals. Times without number have I seen
like destruction wrought to mosquitoes by spiders’ webs; for it is a fact that, even
after the aranead has satisfied its appetite, its snare continues to capture insects.
On one occasion I took the pains to count the number of insects of various species
upon one large web, which was spread in a favorable position, and found that
there were two hundred and thirty-six. It is a most common thing to observe
three, four, or half a dozen flies or other insects trussed up upon the viscid orb
of some of our orbweaving species. It is needless to add the conclusion from
the above facts: if people would decrease the number of mosquitoes, let them en-
courage the multiplication of spiders.”

The jumping spiders are probably more often an effective check upon the
mosquitoes infesting houses than is generally realized. The commission of the
Institute Pasteur, while engaged in their studies on yellow fever and the trans-
mitting mosquito at Rio de Janeiro, found that their studies were seriously in-
terfered with by spiders of the genus Salticus. They found that these jumping
spiders were very common in houses in the tropics and that they are a valuable
aid in the destruction of mosquitoes. In further praise of these spiders they
state: “ Not only do they reduce the large number of mosquitoes, which enter
the houses, in a noticeable manner, but the flies as well contribute largely to
satisfy the appetite of these voracious jumping spiders.” It is probable that
with us the mosquitoes which hibernate in cellars and similar situations are
considerably reduced by the spiders which prowl about in these places.

Doctor John B. Smith seems to be impressed by the number of mosquitoes that
are destroyed by spiders. He states that he has frequently looked over a series of
webs in the morning and found only mosquitoes captured. Sometimes there
would be only one or two, and sometimes there would be a great bunch of them—
reduced to little balls or dry husks. He considers it probable that many spiders
subsist largely upon mosquitoes, and that they are among the most effective mos-
quito checks.

In a recent article Doctor N. Leon, of the University of Jassy, shows that in
the marshes of the delta of the Danube, and in other localities in Roumania,
176 MOSQUITOES OF NORTH AMERICA

spiders are among the most important enemies of mosquitoes. Spiders are very
abundant in these swamps and Doctor Leon states that enormous numbers of
mosquitoes are caught in their nets and killed. Different species of spiders
weave their webs on sedges, reeds and willows and it is not rare to find as many as
twenty webs on one willow. Sometimes the number of webs is so great that they
become continuous and completely enwrap the tree and one can conceive the
large numbers of mosquitoes that can be caught in such webs.

Mr. W. L. McAtee recently made an observation in Arkansas which is at
variance with those already given and which indicates the necessity for more
careful observations.

“On a rainy day a large number of Anopheles quadrimaculatus were found
sitting on a spider web in a hollow tree. Thinking they must be at least slightly
entangled, I counted on capturing them easily. Upon putting my cyanide bottle
near one, the whole swarm rose lightly on the wing, not sticking to the web at
all. By further tests I found that they were perfectly at home on the web.”

OTHER ARTHROPODS.

Doctor Dupree once stated in a letter that he was satisfied that small crayfish
and fresh-water shrimps kill the larve of mosquitoes. Britton has shown that
salt-water shrimps (species not mentioned) will eat the larve of the salt-marsh
mosquitoes but thinks that their structure and small capacity prevent them from
consuming any great numbers.

BATRACHIANS.

It appears from the observations and experiments of Galli-Valerio and Rochaz
de Jongh that frogs and toads will not capture mosquito larve or pupa. No
observations appear to have been made with reference to frogs and toads as de-
stroyers of adult mosquitoes but there can be no doubt that they capture mos-
quitoes along with other insects. The above-mentioned observers found that the
north African Discoglossus pictus, a frog-like batrachian, is an efficient de-
stroyer of mosquito larve. This animal has the habit of capturing its prey under
water while the frogs and toads do not do so. The same observers found that in
Switzerland Triton cristatus and Triton alpestris are effective destroyers of
mosquito larve. They observed that a certain puddle which in past years was
inhabited by Triton cristatus at that time contained no mosquito larve ; during
two subsequent years, when the tritons were absent, this same puddle harbored
great numbers of mosquito larve. They found that the larva of this triton, as
well as the adult, destroyed mosquito larve.

In the section on “ Remedies ” under the head of the “ Practical use of natural
enemies of mosquitoes,” mention is made of the importation into Hawaii of the
western salamander or newt (Diemyctylus tortosus) which has been kept for
several weeks in an open tank by Mr. Albert Koebele, with the result that they
devoured all of the mosquito larve in the tank.

The aquatic larve of our terrestrial salamanders are predaceous and feed on
mosquito larve as well as other aquatic insects. Mr. W. L. McAtee of the Bio-
logical Survey has fed the larve of Amblystoma opacum with larve of Chaoborus
BIRDS EATING MOSQUITOES 177

and of mosquitoes and found that they captured them very promptly. In
Europe the larva of Salamandra maculosa is known to destroy mosquito larve.

Tadpoles, or pollywogs, are so frequently found in stagnant ponds that the
question has often arisen as to whether they destroy mosquito larve. In our
experience tadpoles and mosquito larve do not occur together; we have found
mosquito larve invariably absent from water inhabited by tadpoles. This may,
however, be purely a coincidence and not due to any effect from the tadpoles
themselves. As the tadpoles are wholly vegetable feeders their influence, if any,
upon the mosquitoes must be a purely mechanical one; their violent movements
might cause a contant disturbance which would interfere with the mosquito
larve. It must also be remembered that, at least in temperate regions, the tad-
poles appear when the great wave of mosquito larve has already passed and when,
in fact, very few mosquito larve are to be found. Doctor Smith records some
experiments made by Mr. W. P. Seal, of Delair, N. J., with the tadpoles of the
bullfrog (Rana pipiens) which resulted negatively. Even when the tadpoles
had been deprived of all food for several weeks they would not eat mosquito
larvee.

REPTILES.

In the tropics insectivorous lizards undoubtedly destroy mosquitoes along
with other insects. Giles states that the bright little gecko lizard, commonly
found in bungalows in India, is a valuable destroyer of mosquitoes in houses.
He considers an individual gecko “at least equal in mosquito destroying effi-
ciency to a fly paper of the largest size, and their company should be encouraged
accordingly.” ‘There must be other species having similar habits, but as far as
we are aware specific mention has not been made of their mosquito diet.

BIRDS.

As a matter of course, many insectivorous birds which feed while on the wing
destroy mosquitoes in great numbers. This is especially true of the goatsuckers
(Caprimulgide), to which belong our night-hawks and whip-poor-wills, as they
are mostly active at twilight when mosquitoes are most in evidence. An observa-
tion is on record by the late Professor F. L. Harvey, in which he states that he
found over 600 insects, largely gnats and flies, in the crop of a single night-hawk
(Chordeiles virginmianus).

Mr. Allan H. Jennings, formerly entomologist of the Isthmian Canal Com-
mission, has published an interesting note in the Proceedings of the Entomo-
logical Society of Washington, vol. 10, pp. 61-62, on the mosquito-eating habit of
the Cuban night-hawk (Chordeiles virginianus minor). He states that while
collecting birds on the island of New Providence, Bahamas, in May, 1887, he
had an opportunity of observing the effectiveness of this bird as a mosquito
destroyer.

“One afternoon about 4 o’clock a heavy thunderstorm came up from the
west accompanied by much rain. When the storm passed by, about an hour
before sunset, it was followed by large numbers of birds of many species, but
mainly the smaller insectivorous birds, warblers, etc. ‘They were moving in the
direction the storm had taken and were evidently feeding as they went, though
passing quite rapidly. Accompanying them was a number of Cuban night-
178 MOSQUITOES OF NORTH AMERICA

hawks flying rather low at about the level of the tops of the somewhat low trees
fringing the coast at this point, or, in other words, at a height of 25 or 30 feet.

“ Two of these were taken and on preparing the skins were found to be exceed-
ingly fat while the stomachs were distended with mosquitoes, apparently a small
species of Culea and resembling the species that was most abundant in the

locality.
“The stomachs of a few warblers taken at the time were also full of mos-

quitoes. Unfortunately I made no note of stomach contents of other specimens
of the species taken at other times and points in the island.”

The whip-poor-will (Antrostomus vociferus) has also been mentioned as a
mosquito destroyer but the food of this goatsucker is known to consist largely
of nocturnal moths.

In an interesting letter from Doctor John B. Fort, of Athens, Georgia, dated
February 4, 1909, the statement is made that in his opinion the most useful bird
in the destruction of the mosquito is the chimney-swallow or American swift
(Chetura pelagica). He states that he once examined the stomach of a newly
killed bird of this species, and estimated more than 600 insects of the order
Diptera in its stomach. They were nearly all mosquitoes. Doctor C. Hart
Merriam also gives this bird first place in the list of mosquito destroyers. It
should be noted that this bird is crepuscular in habits.

The true swallows (Hirundinide) are often mentioned as mosquito de-
stroyers. It is obvious that this must be so where mosquitoes are present when
one considers their habit of feeding upon the wing and being most active in
quest of food towards evening. Florence A. Merriam, in “ Birds of Village and
Field,” states that the eaves- or cliff-swallow (Petrochelidon lunifrons) “ eats
enormous quantities of winged ants, mosquitoes, injurious wheat midgets,
spotted squash beetles, and beetles that work under the bark of trees.” Forbush
enumerates mosquitoes as part of the food of the white-bellied swallow (Iri-
doprocne bicolor) and the barn swallow (Hirundo erythrogastra). W. L. Mc-
Atee gives the purple martin (Progne subis), bank swallow (Riparia riparia)
and northern violet-green swallow (Tachycineta thalassina lepida) as mosquito
feeders.

The tyrant flycatchers (Tyrannide) feed mostly upon insects which they
capture upon the wing, watching for them from some prominent perch. Mos-
quitoes also make up part of the food of the birds of this family. Forbush
specifies mosquitoes as part of the food of the wood pewee (Mytochanes virens),
phoebe (Sayornis phebe) and kingbird (Tyrannus tyrannus).

Aside from the work of birds against adult mosquitoes, it is certain that
aquatic birds must destroy many larve and eggs. Mr. Wm. Beutenmiiller, in
the essay previously cited, is of opinion that aquatic birds could be used for the
purpose of destroying mosquito larve, in rain-pools, ponds, and other waters
near houses ; also in ponds in well-cleared fields and cultivated land where there
is no extent of woods. He thinks that the management of aquatic birds under
such conditions can be made simple, and their breeding profitable. Some years
ago, Mr. Wilton Lockwood, of Boston, an artist, who had at that time, and per-
haps still has, a fad for raising aquatic fowls, told one of us that in his opinion
they are great destroyers of mosquito larva. He was particularly impressed by the
BATS AS MOSQUITO DESTROYERS 179

favorable work of the spoon-bill duck, which he thought is particularly adapted
to the destruction of mosquito larve resting at the surface of the water. Mr.
McAtee, of the Biological Survey, has recently found mosquitoes in the gizzard
of the Mallard (Anas platyrhynchos).

Doctor Smith has recorded the fact that some of the shore birds eat mosquito
larvee in considerable numbers. He examined the stomachs of a ring-necked
plover (Zgialitis semipalmata), of a least sandpiper (Pisobia minutilla),
and of a semipalmated sandpiper (Hrewnetes pusillus), and all of these had
eaten the larva of Aédes sollicitans in some numbers, the ring-necked plover
having eaten the most. He states, and this has also been our experience, that
there was no especial difficulty in identifying the larvee from the remains, the
head and breathing-tube are so strongly chitinous that they are not digested.

W. L. McAtee, in a recent circular of the Biological Survey, sums up our
knowledge of the office of shorebirds in the control of mosquitoes as follows:

“ Shorebirds perform an important service by their inroads upon mosquitoes,
some of which play so conspicuous a part in the dissemination of diseases. Thus,
nine species are known to feed upon mosquitoes, and hundreds of the larve or
“wigglers’ were found in several stomachs. Fifty-three per cent of the food of
28 northern phalaropes from one locality consisted of mosquito larve. The in-
sects eaten include the salt-marsh mosquito (Aédes sollicitans), for the suppres-

sion of which the State of New Jersey has gone to great expense. The nine
species of shorebirds known to eat mosquitoes are:

“ Northern phalarope (Lobipes lobatus).

Wilson phalarope (Steganopus tricolor).

Stilt sandpiper (Micropalama himantopus).

Pectoral sandpiper (Pisobia maculata).

Baird sandpiper (Pisobia bairdi).

Least sandpiper (Pisobia minutilla).

Semipalmated sandpiper (Lreunetes pusillus) .

Killdeer (Oxyechus vociferus).

Semipalmated plover (Aegialitis semipalmata).”
BATS.

Bats are important mosquito-destroying animals. Flying at dusk and after
dark, and capturing all flying insects upon the wing, they devour large numbers
of adult mosquitoes in times of mosquito prevalence. Mr. C. Few Seiss, at a
meeting of the Feldman Collecting Social, in Philadelphia, June 19, 1901,
stated that he had dissected a specimen of the common brown bat (Hptesicus
fuscus), and had found its stomach full of mosquitoes. The suggestion has been
made by Mr. A. C. Weeks, of Brooklyn, that an attempt be made to breed bats
artificially on account of their importance as mosquito destroyers, but until
recently no one seems to have taken the matter up.

Greatly impressed with the value of bats as mosquito destroyers, Dr. Chas. A.
R. Campbell, formerly city bacteriologist of San Antonio, Texas, has erected a
novel bat breeding-house six miles south of that city. His idea is that the bats
will rapidly become sufficiently numerous, with this admirably adapted nesting
place, to rid the neighborhood of night-flying mosquitoes, and at the same time
the entire expense will be more than paid by having the structure built in such a
manner that the bat-guano can be readily collected and taken away.

13
COLLECTING, MOUNTING AND REARING
MOSQUITOES.

COLLECTING ADULTS.

In flight, adult mosquitoes may be captured with a net. A small, light,
silken net is preferable, though an ordinary insect net will serve, if care be taken
to let the insects settle before inserting the bottle. The chloroform killing
bottle is the best, as the insects die more quickly and are thus less liable to injure
themselves. A satisfactory bottle may be made by placing a rubber stopper in
the bottom of a test-tube and pouring chloroform upon it. The chloroform is
absorbed by the rubber, which swells to fill the tube, and a supply of vapor is
subsequently given off without a residue of liquid to wet the captures. An ordi-
nary cyanide bottle will serve, but it is necessary with this to wait a longer time
until the insects are quiet before reopening it to admit others. Cotton should
be placed in the bottom of the tube or jar to keep the mosquitoes from becoming
abraded by sliding about as the jar is carried, or in the case of a small jar, narrow
strips of absorbent paper. On no account should any other insects be killed in
the same jar with mosquitoes.

The female adults of many species are readily captured as they come to bite,
when they can generally be taken by placing the collecting bottle over them.
Horses or other animals may be used as bait, or the person of some obliging
friend. The collector can often attract specimens in some numbers by sitting
in the woods or open, evenings after dark or by day, according to the species
sought, and may collect them as they come. All males and those females that do
not bite may be taken by beating bushes and low vegetation, especially in damp
situations along streams and marshes. Some species frequent trunks of trees,
hiding in the crevices of the bark, and may be searched for in the daytime.
Outhouses, cellars and caves should be searched for the species which seek
shelter in such situations.

MOUNTING ADULTS.

In mounting the adults for the cabinet a double mount should always be used.
The insects are too small to admit of pinning them directly upon ordinary insect
pins, except those of the smallest calibre. These can only be handled with
forceps and this is very inconvenient in ordinary work. The specimens should
be mounted upon card-points, small triangular pieces of card, the insect glued
upon the small end, an insect pin passed through the larger end. The specimens
should be attached by the ventral surface of the thorax, so that the upper side
will be free for examination. We find shellac dissolved in alcohol the best
adhesive. The pins carrying the card-points should be stout enough to be
handled easily. Large specimens, like Megarhinus, may be pinned with the

180
REARING MOSQUITOES 181

small pins used for Microlepidoptera upon narrow strips of cork. The method
of pinning on pins run through card-board disks, in use among British col-
lectors, we find objectionable, as the disk interferes with the proper examination
of the specimen, and it is impossible to remove the insect from the mount with-
out relaxing and remounting it. Furthermore, the specimens very often get
broken by the disks becoming loose upon the pin. Labels, giving the exact
locality and date of capture and the name of the collector, should be pinned upon
the larger pin of every mount.

SENDING BY MAIL OR EXPRESS.

Specimens which are to be sent to a distance, should be placed while still soft
in pill boxes between two layers of cotton, packed loosely and not again opened
until they reach their destination. Tin boxes and glass vials should be avoided,
as the retained moisture causes the specimens to mould. Collections made in
moist climates must be well disinfected with creosote or some similar substance.
The pill boxes to be sent by mail, should be securely packed in a stout outer
wooden box that will not be crushed in transit. Considerable risk always attends
sending pinned specimens by mail or express. This can be minimized by proper
packing. The pins should be firmly set in a cork-bottomed box over which a thin
layer of loose cotton has first been spread. This box should then be packed in a
stout outer box, at least four inches larger than the inner box in all dimensions,
the space between loosely packed with excelsior or other elastic packing material.

REARING.

Captured adult mosquitoes, even when most carefully collected, are liable to
be more or less damaged, often unrecognizable, since the insects lose their scales
easily even when living in a state of nature. It is therefore desirable to breed
specimens from the larve as far as possible. It is still important to collect the
adults, as many species may be thus taken which would be overlooked if only bred
specimens were retained. Some species are not infrequent as adults, the larve
of which are very difficult to obtain, if they are not entirely unknown. The
larve of mosquitoes are of great importance in specific determination. Many
species of Culex are of uncertain determination without the associated larve,
while some Aédes have identical adults, yet dissimilar larve. The characters
of the larve reside in the modifications of the chitinous appendages of the skin
and the arrangement of the hairs. As these are fully retained by the cast skins,
it is possible to preserve both the larva and the adult of the same identical speci-
men, thus assuring absolutely correct associations. This should be done wher-
ever possible. To secure it, the mosquito larve to be reared should be isolated in
separate tubes. We find flat-bottomed glass tubes about one inch in diameter to
be suitable. They should be loosely stoppered with cotton. Having obtained a
culture of mosquito larve, the collector pours the liquid and contained larve
into a shallow dish, one of white material preferred, and with a pipette or spoon
places one larva in each tube. Care should be exercised to introduce no pre-
daceous enemy with the larva. The tube is then filled two-thirds full with the
182 MOSQUITOES OF NORTH AMERICA

original liquor and the cotton stopper inserted. As any given culture is apt to
contain a mixture of species, it is well to use care to select those larvee that appear
to be of different kinds. A culture may contain hundreds or thousands of in-
dividuals, and it is seldom feasible to isolate them all. The rest may be bred in
common to secure a supply of adults; but the jar should be kept under daily
observation to see if any different species at first unnoticed appear.

The isolation made, each individual should be given a double number, one for
the original entire culture as reference to the notes of locality and date, the
other a serial number for the identification of the individual isolation. These
numbers should be attached to the tube so that they are not liable te get mixed.
‘All the isolations should be viewed at least once a day, and as soon as the larva
has pupated the cast skin should be removed with a pipette and put in a small
vial with alcohol containing a little glycerine and stoppered with cork. A small
label bearing the locality and isolation numbers should be inserted in the bottle,
and the bottle kept with the isolation until the adult has emerged. On the is-
suance of the adult, the pupa skin may be added to the same bottle. Finally,
the small bottles of skins should be stored in a larger jar containing alcohol, to
keep them from drying.

The adult should rest at least twenty-four hours after emergence for its chitin
to harden and become perfectly dried. If killed too soon the specimens will
shrink and collapse and be rendered unfit for study. When sufficiently hardened,
the mosquito can be removed, killed by chloroform, mounted and given the
locality and isolation numbers in addition to the usual data of locality, date and
collector. The locality note-book should be kept as fully as possible, giving not
only locality and date, but the character of the water in which the larve occurred
and in what it was retained. There is no danger of recording too many data;
the recording of too few is a common failing.

The food of mosquito larve consists of the organic matter in suspension in
the water, or floating upon the surface, or settled or growing upon the bottom.
It varies with the different species, so that the safest rule for general use is to
keep a supply of the original water together with the detritus at the bottom and
change the water in the isolation tubes occasionally. Experience will often
show the nature of the food of a given species, and in such cases artificial food
can be supplied, on which the larve will thrive even better than in their natural
environment; but such an experiment may have a fatal termination. Doctor
John B. Smith, who was familiar with the habits of Culex pipiens and Culex
restuans, which live in foul water containing decaying organic matter, fed
pieces of meat to larve of Wycomyia smithit, that live in water in pitcher-
plant leaves, and the resulting fermentation killed them all. Some mosquito
larve are cannibalistic and must be supplied with the larve of other species for
food, preferably of the same species with which they were found associated. No
general rules can be given, as each species is a law unto itself; but the collector
who desires the quickest results will isolate the largest, or most nearly fully
grown larve, which will generally successfully complete their transformations
upon the food material collected with them. It must not, however, be forgotten
PERMANENT MOUNTS 183

that the small larvae may belong to another species, and they should not be
neglected. Anopheles larve, which are surface-feeders, will not thrive in the
isolation tubes above described. They must he isolated in broad dishes or
saucers, which should be kept uncovered, in order that the dust from the air
may settle continuously upon the water. By properly watching the cultures
daily, the skin can be preserved at pupation and the pupa transferred to a cotton-
stoppered isolation tube for the emergence of the adult.

SLIDE MOUNTS.

The above method of preserving the larval skins suffices for temporary pur-
poses, and the skins when destined for dissection of the mouth-parts should be
kept in the alcohol and glycerine mixture. For examination the skins may be
placed on slides in a drop of glycerine; but for permanent preservation they
should be mounted in balsam. The skin should be treated with weak alcohol to
remove the glycerine, then in strong alcohol, absolute alcohol, oil of cloves and
finally Canada balsam, which should be heated after the cover glass has been
applied. Often sufficiently satisfactory results may be obtained by drying the
skin on a slide and applying balsam directly ; but if glycerine has been used this
must first be removed. Skins thus mounted are liable to become distorted, but
the method is more rapid and often suffices for ordinary determination.

The male genitalia are important not only for specific identification, but also
for general study of systematic relations. For proper examination, the genitalia
must be mounted on a slide as microscopic objects. The tip of the abdomen
with the male organs attached can be readily broken off from a dried specimen by
the use of a pair of fine forceps. They are then placed in a solution of caustic
potash ; about one part of the saturated solution to ten parts of water will give
satisfactory results. The genitalia are left in this solution until only the
chitinous parts remain and all the details are readily visible. The time required
will vary with the temperature and with the size and chitinization of the speci-
men, very fresh specimens requiring much less time than old ones. The speci-
men should be examined from time to time while in the potash, as, if left too
long, it will become too soft and transparent and the details will then be very
difficult to see. Usually, if put in the potash late in the afternoon, the specimens
will be ready to mount on the following morning. If one desires to study a speci-
men immediately, it should be boiled in the potash over an alcohol lamp or
Bunsen burner. In this case, care must be taken, as the potash in boiling is
likely to spatter and the specimen thus be lost. Moreover the specimens treated
by the slower process make better mounts.

When sufficiently cleared the specimens must be thoroughly washed with water
to remove all traces of the potash, then dehydrated with absolute alcohol, cleared
with oil of cloves and finally mounted in balsam. Before placing the cover glass,
the specimen should be examined to see that it is in the proper position for study.
Sometimes, when the parts are folded together, they can be spread by pressure
on the cover glass directly over them. This is especially true of those forms in
which the abdomen is depressed and the claspers prominently exserted, such as
184 MOSQUITOES OF NORTH AMERICA

the species of Aédes and Anopheles. In those forms in which the abdomen is
compressed or wedge-shaped, it is often very difficult to get the parts into posi-
tion for a dorsal view. It is then necessary to press the tip of the abdomen with
forceps until the parts lie flat, and this is best done while the specimen is in the
oil of cloves. Sometimes the end pieces of the claspers are folded under, and
then it requires careful manipulation to bring them into view without injury.
In certain cases, where the genitalia are very compact, and in others where they
are very complicated, it becomes necessary to break them up in order that the
details may be brought into view. This must be done carefully under a dis-
secting microscope or a good lens, and requires skill and practice.

The slides should be numbered and the data entered in a book. The mosquito
from which the genitalia were taken should receive a pin-label referring to the
number which has been given to the slide.

Whole adults or portions of them or entire larve which it is wished to mount
can be treated with caustic potash in the manner above described.

COLLECTING LARVE.

All mosquito larve are aquatic, and all sorts of water should be examined to
collect them. In general, lakes, ponds and streams are not suitable breeding-
places, for these larger bodies of water contain insufficient nourishment for
the larvee, and generally do contain fish, which would devour any larve that hap-
pened to appear. It is exceptional for mosquito larve to be found in large, or
running bodies of water, though there are such exceptions. Anopheles larve not
infrequently breed along the margins of swiftly running streams, and large
ponds may harbor Culex larve in their grassy edges. Mansonia larve live in the
mud at the bottoms of the sedgy swamps, attached by their air-tubes to the vas-
cular roots of the aquatic vegetation. In the tropics, almost any water may con-
tain larve. The collector will, however, find the best results in small stagnant
collections of water, particularly those of a transient character. The different
genera will be found to occur in different situations. For example, Aédes, with
the Psorophora that prey upon them, in temporary ground pools, some species in
tree-holes ; Culex, with the predaceous Lutzia, in permanent or semipermanent
ground pools; a few species in tree-holes; Bancroftia, with their enemy Mega-
rhinus, in tree-holes, some species in bromeliaceous plants; Deinocerites and
allies in crab-holes; all the sabethids in water in the leaves or flower-sheaths of
plants, some species in tree-holes, etc. The sabethid larvee, in the tropics, re-
quire especially careful search, as they occur in such peculiar locations, while
every different plant harboring them will be found to have its own fauna both
of Wyeomyia, etc., and the predaceous Lesticocampa and others. This fauna is
especially characteristic of the tropics, where many plants are water-bearing ;
but in our temperate region only a single sabethid occurs. It has, however, the
normal habits of its tribe, living in the water in the leaves of the pitcher-plant,
Sarracenia purpurea, the only water-bearing plant of temperate distribution.

The season of the year is an important factor in the occurrence of species,
rains being essential to the development of perhaps the majority of larvee. Espe-
NECESSITY FOR EXACT DATA 185

cially is this true of Aédes. Many species of this genus develop only in the water
formed by melting snows and are to be found only in early spring, while others,
are partial to tree-holes or rock-pools. The species of Psorophora breed with
astonishing rapidity in the temporary puddles following showers, in which they
hatch and pass the four larval stages in a scarcely greater number of days.

To follow the complete life-history of any species and to breed it from egg to
adult will require special experiment in each case. Many species have never been
thus bred. In fact, our collectors have all been too much hurried, and in en-
deavoring to breed as many isolated examples as possible in a limited time, have
been obliged to omit the full and careful study of individual species, so much
to be desired. Especially are we lacking in knowledge of the habits of the adults,
their ordinary length of life, dispersal, swarming habits, etc., and these can only
be discovered by careful, unhurried observations in the field.

COLLECTING EGGS.

Eggs of many mosquitoes may readily be obtained by confining captured
females over water. Aédes will generally oviposit readily, but Culex less readily.
Bred specimens can not often be mated in captivity, on account of the peculiar
swarming habits, which seem essential to copulation, and which can not be
executed in a confined space. Doctor Dyar, however, bred two generations cf
Aédes atropalpus in a quart jar. Adults confined for oviposition require food.
All will eat sugared water, preferably soaked into cotton, or they may be fed with
raisins or figs. Many thrive best on mammalian blood. There are, however, few
species that absolutely require that article of diet. Speaking broadly, mosqui-
toes are flower-insects, living upon honey. The habit of taking mammalian
blood, while common, is not universal, and seems to be obligatory only in the case
of a few species. The group in general suffers in reputation from the vicious
habits of a minority of its members. We are far, however, from wishing to imply
that mosquitoes are negligible or harmless to man; only we can not emphasize
too strongly the need of specific study of the different forms in order to direct
our efforts against the dangerous or noxious species only, and not waste time
and labor in destroying harmless or even beneficial forms.
THE RELATION OF MOSQUITOES TO MAN.
THE CARRIAGE OF DISEASE BY MOSQUITOES.

That certain mosquitoes are an essential factor in the propagation of certain
diseases is now well demonstrated and generally accepted. In every case where
such relation of the mosquito has been proved the réle of the insect is not that of
a purely mechanical carrier or transmitter, as is, for example, the conveyance of
typhoid fever by the house fly. The diseases in question are caused by organisms
which have a complex life-cycle, part of which is passed in man and part in the
mosquito, and in the absence of one or the other of the hosts their existence or
continuance is impossible. In other words, the causative organisms of these
diseases, as far as we know them, are animal parasites. These parasites can
exist only in definite hosts. This restriction goes so far that a given parasite is
restricted, on the one hand to a certain vertebrate host (for example, man, the
dog, the sparrow), on the other to a certain species of mosquito. It is the full
recognition of these facts that has made the thorough investigation of mosqui-
toes, systematically and biologically, such an important study.

In the following, the causative organisms, their life-cycles, and the mosquitoes
concerned in each case, are discussed under the heading of the respective diseases.

EARLY IDEAS.

The idea that mosquitoes carry disease is not only very old historically, but
occurs among primitive nations in various parts of the world. References have
been found in the very early literature of India, in writings that are practically
prehistoric, that indicate that the idea was held in those early days, especially
with reference to malaria. The natives of different parts of Africa and in Assam
are said to hold the same idea, and it has been pointed out that the belief has
long been prevalent among the Italian peasants and among those in the southern
Tyrol. According to Humboldt the inhabitants of the upper Orinoco at the time
of his visit accused the mosquitoes of being the cause of the febrile maladies from
which they suffered. Koch points out that the negroes of the Mschamba tribe
on Mount Usambara in Africa do not descend into the lower regions on account
of fear of fever. Fever in their language is called mbui and mbz is also their
name for mosquito, indicating that they understand the connection between the
two so perfectly that they have but one name for both.

Dr. A. F, A. King, of Washington, in an important paper published in 1883,
called attention to an article by John Crawford entitled: “ Mosquital Origin
of Malarial Diseases,” said to have been published in the Baltimore Observer in
1807, but subsequent investigations by Dr. King and Dr. W. S. Thayer, of
Baltimore, have failed to find the article, either in the newspaper itself, or in a
review of Crawford’s papers published in the Baltimore Medical and Physio-
logical Recorder, 1809.

186
DISEASE RELATION SUSPECTED 187

In 1848 Dr. J. C. Nott published a paper on the origin of yellow fever in the
New Orleans Medical and Surgical Journal, in which he expressed his belief in
the insect transmission of yellow fever and malaria. He called attention to the
fact that yellow fever occurs under conditions and in places favoring the de-
velopment of insects, and he thought it was spread from one locality to another
by them. He thought it likely that the disease itself is produced by micro-
organisms.

Recently Dr. A. Agramonte, in an article in the Cronica Médico-Quirtirgica

de la Habana, and quoted by the British Medical Journal, calls attention to the
pioneer suggestions of Louis Daniel Beauperthuy, born in Guadeloupe in 1808.
Writing in the Gaceta Official de Cumand (Venezuela), in May, 1853, Beau-
perthuy says that yellow fever is due to the same cause as that producing inter-
mittent fever, and that it is by no means to be regarded as a contagious dis-
ease. It develops under conditions favoring the development of mosquitoes.
The mosquito introduces into the circulation of a person bitten a poison which
softens the red blood corpuscles, causes their rupture, and facilitates the mixing
of the coloring matter with the serum. There are many mosquitoes but not all
are equally dangerous ; most so are those with legs striped with white and partly a
household kind. He further states that remittent, intermittent and pernicious
fevers, like yellow fever, have as their cause an animal or vegeto-animal virus
which is inoculated into the human body. He supposed that this poison was
sucked up by the mosquitoes from decomposing substances, exposed at low tide,
on the seashore and in the mangrove swamps and pointed out that yellow fever
invariably breaks out in such places. These fevers are grave in proportion to
the abundance of mosquitoes. It is not the air from marshes, nor stagnant
water, that makes such regions unhealthy, but the presence of mosquitoes.
Beauperthuy wrote most fully to the journal above mentioned, but he made
more than one communication to the Academie des Sciences, of Paris. We have
seen one of his communications, dated January 18, 1856, entitled: “ Researches
into the cause of Asiatic cholera, into that of yellow fever and of marsh fever,”
in which he states that as early as 1839 his investigations in unhealthy localities
in South America convinced him that the intermittent or so-called marsh fevers
are due to a vegeto-animal virus inoculated into man by mosquitoes. His idea,
however, was that this virus was extracted by the mosquitoes from decomposing
substances.
' Dr. Oswaldo Cruz, director of the Public Health Service of Brazil, in a recent
paper (Public Health Reports, U. S. P. H. and M. H. Service, Nov. 19, 1909)
calls attention to the fact that in Brazil, before the American experiments, Dr.
Utingguassti and afterwards Dr. Stapler, of Sao Paulo, also made references to
the transmission of yellow fever by mosquitoes. It is probable that there were
other physicians in advance of their times who, like Nott and Beauperthuy, held
similar ideas, but if they expressed them, or if they wrote about them, their words
have not been preserved.

Many curious ideas about the possible relation between mosquitoes and disease
have been published. For example, in a paper entitled “ Curious Facts Concern-
188 MOSQUITOES OF NORTH AMERICA

ing Man and Nature With a Few Practical Suggestions on Other Subjects,”
Dr. Samuel W. Francis, in 1874, made the following statement, which, in the
light of recent developments, is a very curious instance of a conclusion dia-
metrically opposed to the right one having been drawn from practically the same
premises :

“Tt is my firm conviction that the mosquito was created for the purpose of
driving man from malarial districts; for I do not believe that in nature any
region where a chill and fever prevail can be free from this little animal. Now
if man will not go, after warning is given in humming accents, then the mos-
quito injects hypodermically a little liquid which answers two purposes—first
to render the blood thin enough to be drawn up through its tube, and secondly
in order to inject that which possesses the principles of Quinine! This idea I
published in a work entitled ‘ Life and Death, p. 210, March, 1871; a few lines
will suffice. ‘The time will come when it will be publicly acknowledged that the
little fluid they (mosquitoes) inject into your blood contains certain specific
properties for different diseases. To prove that I am right, let any skillful
chemist test the powerful drop contained in a mosquito’s sack, and he will find
many of the properties of Quinine.’ ”

A curious old account of the value of measures undertaken with the idea of
preventing malaria, and which at the same time were incidentally antimosquito
measures (although cause and effect were not in the least recognized), is given
in the 15th Annual Report of the American Society for Colonizing the Free
People of Color of the United States, Washington, 1832, p. 51.

Joseph Reynolds, of Bristol, writing to Elliot Cresson, in the United States,
gives an account of the measures adopted to preserve the health of the crew of
the ship Cambridge during the period of about ninety days when she lay in the
river above Sierra Leone. None of the crew were suffered under any con-
sideration to be out of the ship at sunset or after. A sail was stretched on the
windward side of the vessel and an awning was also provided which extended
over the poop and the whole of the main-deck “ to defend the crew from the night
air.” “The night watch was encouraged to smoke tobacco.” Incidentally, the
hull of the vessel was kept pure by the constant use of chloride of lime. The crew
were given a tonic treatment of strong coffee and French brandy. “The result
was, that the ships on each side of the Cambridge, lost the greater part of their
crews: not one man of the Cambridge was seriously unwell, during the whole
time they lay in the River, and it was remarked that the ship was so clear of mus-
quitoes, that the Captain threw aside the curtains which he had provided for his
defence against them.” Mr. Reynolds remarks that the instructions given to the
commander were derived from reading Dr. Macculloch’s “ Essay on Malaria,” a
work which advocated protection against the exhalations of malarial localities.

MALARIA.

THE MALARIAL ORGANISMS.
The disease known as malaria is caused by parasites in the blood which feed
upon the red blood-cells. They are unicellular animals, belonging to the Spo-
rozoa. They have been classified in the sub-order Hemosporidia and genus
MALARIAL ORGANISMS 189

Plasmodium of Marchiafava and Celli. Recently, as the result of more exact
studies of blood parasites, Max Hartmann and Victor Jollos have worked out a
new classification. They have created a new order, Binucleata, in which are
united the various blood parasites, it being shown that the trypanosomes and
other forms living free in the blood-fluid are related to the plasmodii and con-
nected by intermediate forms. The malarial parasites are grouped in the family
Plasmodiide and four genera are recognized. The genera Achromaticus and
Polychromophilus of Dionisi are parasites of bats, the genus Proteosoma Labbé
is parasitic in birds and the genus Plasmodiwm infests man, monkeys and
squirrels. All the Plasmodiide require two hosts to complete their life-cycles
and one of these hosts acts as the transmitting agent. Three species of Plas-
modium are generally recognized as affecting man, but some investigators be-
lieve that more species are concerned in producing the various types of malarial
fevers. The nomenclature of the malarial parasites is a most confusing one,
hardly two authors agreeing in the specific names applied to the different
parasites. We follow here the nomenclature of Blanchard who has carefully
worked out the synonymy according to the rules of zoological nomenclature.

Plasmodium vivax (Grassi & Feletti)—This parasite produces the benign
tertian fever, simple or double. The period of schizogony is 48 hours and may
sink to 44 hours. It is the most widely spread and commonest of the species.

Plasmodium malaria (Laveran).—Thig parasite produces the regular quar-
tan fever. The period of schizogony is 72 hours. It is more prevalent in tem-
perate and subtropical regions, but appears to be rare everywhere. It resembles
the Plasmodium vivax in its appearance and development, but can be dis-
tinguished readily by morphological differences, besides the different type of
fever that it produces in man.

Plasmodium falciparum (Welch).—This is the parasite of pernicious, trop-
ical or estivo-autumnal malaria. It is most frequently termed Plasmodium
precox or Laverania malarie. The genus Laverania is based on the crescent-
shaped stage but has been generally abandoned. The opinion has been expressed
by various investigators that there is more than one species of organism account-
able for the various forms of pernicious or quotidian fever. Schizogony usually
occurs in the internal organs, particularly the spleen, instead of in the peripheral
circulation, as is the case with the tertian and quartan forms. The fever pro-
duced is of an irregular type and the period of schizogony, as it does not occur
in the periphery, has not been definitely determined. Most observations indicate
a period of about 48 hours, others one of 24 hours.

THE LIFE-CYCLE OF THE MALARIAL ORGANISMS.

There are two cycles in the evolution of the malarial parasites. One takes
place in the blood, is asexual, and is designated the schizogonic cycle; the other
is the sexual cycle which develops within the transmitter and is called the sporo-
gonic cycle.* The continuous existence of the parasites depends upon the trans-

 

*The cycle in the blood is sometimes called endogenous, or cycle of Golgi, that in the
mosquito exogenous, or cycle of Ross.
190 MOSQUITOES OF NORTH AMERICA

fer from one host to the other. When a mosquito sucks the blood of an individual
harboring gametes in a state of complete maturity, these, finding themselves in
a temperature favorable to their further development, copulate. The male
gamete or microgametocyte throws off prolongations in the form of flagella,
called microgametes, and these seek to unite with the female gametes or macro-
gametes. Upon contact with the microgamete the macrogamete prolongs its pro-
toplasm, forming the so-called cone of attraction. This first stage, brought about
by the union of microgamete and macrogamete, is designated as the odkinete and
can be easily observed in any mosquito, or even in blood transferred from the
human body directly to the microscope slide. However, the succeeding stages can
only take place in the stomach-wall of an Anopheles, as demonstrated by Grassi.
The odkinete, to undergo further development, penetrates into a cell of the
stomach-wall of the transmitting insect and there transforms to the odcyst.
In the process of growth of the odcyst further stages occur, first, by its division
the sporoblasts, and from these, by further division, the sporozoits. When the
odcyst is mature it bursts, liberating the sporozoits which thus pass into the
general body-cavity of the host. The sporozoits now find their way into the
salivary glands of the host and there they remain until the mosquito, in biting,
forces them, along with the saliva, through its proboscis into a human being.
Then the other, sporogonic, or asexual, cycle begins.

The sporozoits when introduced into the blood at once enter the red blood-
corpuscles and are now called schizonts. The schizont grows within the blood-
cell and finally undergoes a process of division. The products of this division
are called merozoits. These merozoits are liberated but at once enter another
blood-cell where they again go through the stages of schizonts and merozoits.
Parallel with this development the schizonts begin also to produce gametes or
sexual elements. These sexual elements, however, can not copulate within the
human organism on account of the unfavorable temperature. To enable them to
carry out this function, and to develop further, they require the intervention of
an intermediary host, as already described.

In the macrogametes there is furthermore to be observed a curious phe-
nomenon first determined by Schaudinn; we refer to the parthenogenesis which
is nothing less than a stage which insures the survival of the plasmodium. The
macrogamete when mature, in order not to disappear from the organism, as
happens with the microgametocyte, divides in the same manner as the schizonts.
Probably each product of this division then again becomes a macrogamete. In
this parthenogenesis of the macrogametes lies the explanation of the cases cf
malaria with periodical attacks recurring at great intervals of time. This phe-
nomenon has already been determined for Plasmodium vivax and Plasmodiu
falciparum, and there is every reason to believe that the same occurs with
Plasmodium malarie. An ancient Roman imprecation “ Quartana te teneat”
is significant in this connection as it can be given no other interpretation.

As already stated there exist three well-defined species of Plasmodium which
cause human malaria: Plasmodium malaria, P. vivax and P. falciparum. For
the diagnosis of the species two methods are employed. One is to examine a drop
PARASITE OF PERNICIOUS MALARIA 191

of fresh blood, unstained, placed upon a slide and under cover-glass. It is the
method least employed because it requires greater technical skill; it permits,
however, all the details to be seen, as Schaudinn has shown. Among other
notable achievements he succeeded with this method in following clearly the
penetration of the sporozoit into the blood-cell. The second method consists
in staining the blood which has been spread in a very thin layer upon a micro-
scope-slide. There are various methods of staining which all have as a basis
more or less the same color substances. That most in actual use, because it is
the simplest and the one which enables all the details of the parasite to be dis-
tinguished, is the process of Giemsa.

Plasmodium malarie (the organism of quartan malaria).—When one ex-
amines with the microscope a slide with live parasites of quartan fever one sees
that their movements are much weaker than those of Plasmodium vivar. The
black pigment-granules appear early; the parasitized red blood-cell shrinks a
little, and in stained preparations this can be seen readily. The quartan parasite
sometimes also produces a heavier coloration ; however it does not possess granu-
lations like those of Schiiffner (seen in stained preparations as small red dots)
in Plasmodium vivax, or of Maurer (a very few dots) in P. falciparum. Schi-
zogony takes place only in the peripheral circulation. The parasite divides into
from 8 to 14 merozoits arranged with great regularity, hence this phase is some-
times called the “rosette,” “daisy,” or “marguerite” form. The evolution
takes longer than in any other plasmodium, 72 hours being consumed from one
schizogony to the next. There is a characteristic appearance which this parasite
assumes during growth, that of a more or less broad band across the corpuscle -
which is by many called the aquatorial band. The gametes are round, not only
when inside of the corpuscle, but also when free in the blood-plasm.

Plasmodium falciparum.—The disease caused by this parasite goes under
several names: quotidian, malignant tertian, atypical, irregular, estivo-autum-
nal, pernicious, or tropical fever. The Germans follow Koch and use the term
“ tropical fever ” but this expression is not in accord with the geographic dis-
tribution of the parasite. The differentiation of this parasite is based more on
clinical data than on the structure and biology of the organism. When alive the
schizont is very active. Schizogony takes place in less regular periods than in
the other parasites, fluctuating between 24 and 48 hours. Doflein states that
there may be a prolonged period of 72 hours. Also the number of merozoits is
variable and may range from 4 to 30, although commonly between 6 and 14.
The division always occurs in the internal organs ; in acute cases it can, however,
also be found in the periphery. In this parasite there is commonly formed a pre-
cocious division in the young forms, a fact which explains the rapid progress
which pernicious attacks make. Besides the habitual cycle, then, the parasite
can subdivide before it has completed it. It is quite common to find blood-cells
containing more than two schizonts ; there have already been found as many as
6 or 7 in a single corpuscle. A peculiarity of this parasite is its retreat to the
internal organs after 30-36 hours; after having divided the parasites reappear
in the periphery, generally two or three hours after this process. To this phe-
192 MOSQUITOES OF NORTH AMERICA

nomenon is due the fact that blood examinations made just before a fever-
paroxysm may be negative, the parasite not having yet reached the periphery. In
the greatest part of the cases there can only be observed annular parasites, gen-
erally situated close to the margin of the blood-cell. Rarely there can be found
adults and schizonts in process of division. The proportion of parasitized cor-
puscles is variable and in acute cases can reach an enormously high number, far
beyond what is known to occur in the other two species.

The gametes have a form characteristic of the species. They were the first
malarial organisms to be observed. In 1843 Klencke found them but it was
Laveran who, in November of 1880, in Algeria, recognized them as the causative
agents of malaria, calling them crescentic bodies or half-moon bodies. On
account of this very characteristic form of the gametes certain authors have
placed the organism in a genus by itself, under the name Laverania, in spite of
the fact that this form is transient and changes to a spherical shape when it
becomes free in the blood-plasm.

Ziemann described a form of Plasmodium falciparum which he found in
Africa, founding it on the more pronounced roundness of the crescents and the
rarity of their appearance in the peripheral blood. This rarity of the crescents
is, however, everywhere a frequent occurrence with the pernicious parasite and it
is particularly accentuated during the epidemic months. This variety, as also
various species indicated by certain investigators, have not been accepted by the
majority of good workers. Withal it seems nearly certain that still another
species of Plasmodium exists, characterized by annular forms identical with
those of P. falciparum, but developing without provoking the acute attacks char-
acteristic of this species.

Plasmodium vivax.—This species is responsible for the benign tertian malaria.
It is the best studied of all the species, being the one used by Schaudinn in his
famous researches which have thrown so much light on the biology of the
malarial parasite. Seen fresh the schizont appears endowed with lively move-
ments. Schizogony takes place in periods of 48 hours, each parasite liberating
from 12 to 24 merozoits. It is this species which produces the greatest change
in the blood-corpuscle. After 16 hours it already presents the characteristic
granulations of Schiiffner. The parasite, 24 hours after having invaded the
corpuscle, begins to produce an hypertrophy of the blood-cell which becomes more
accentuated with the growth of the parasite. Parallel with this change the
granulations of Schiiffner increase in number and the anemia of the corpuscle,
which begins with its hypertrophy, continues to grow more pronounced. In
stained preparations these changes can be very distinctly perceived. The
gametes are spherical. The macrogametes when fully developed are about 1 1/2
times as large as the normal red blood-cells; the microgametocytes are very
slightly larger than the corpuscles.

The human organism can be parasitized at the same time by more than one
generation of parasites, either of the same species or of different species. These
evolve independently of each other and therefore also produce separate fever-
paroxysms. The “ double benign tertian” is an example which can be cited;
MALARIAL PARASITES 193

here there are two generations of the same Plasmodium, which, developing
alternately, produce an attack every 24 hours. The double and the triple
quartan are rare forms; the first is marked by two successive days of fever, fol-
lowed by a day of repose, while in the second the attacks are daily. The explana-
tion is the same, the presence in the same individual of two or three generations
of Plasmodium malaria which alternately undergo schizogony.

In acute cases of malignant tertian the attacks are prolonged and another
attack begins before the previous one has ended; such attacks are called sub-
wntrant, There are cases in which a continuous fever appears. As there are
diverse generations of the parasite, whenever any one of them enters into schi-
zogony this is indicated by a fever-paroxysm, generally preceded by a chill which
coincides exactly with the schizogony. The initial chill can be absent in malig-
nant tertian fever; it is, however, always present in benign tertian and in
quartan fever.

When more than one species of Plasmodium is found in the blood this associa-
tion is called a mixed infection. These are most frequently produced by the
parasites of benign tertian and malignant tertian fevers and it is very rarely
that one of these forms has been reported as associated with the quartan parasite.

In these cases not only does each Plasmodium develop in the most complete
independence, without the development of one affecting that of the other, but
also the two species can grow and develop within the same blood-corpuscle with-
out interfering with each other. The same thing happens with like or unlike
elements of the same species. For example one corpuscle can be infested by
various schizonts, each one of which goes through its evolution without disturb-
ing the others ; or, the same may occur with schizont and gamete, male or female,
when they happen to be found together in the same corpuscle.

The mixed infections have contributed much to furnish arguments for the
unicists who believed in the existence of only a single species of Plasmodium and
that this was capable of transforming into varieties, according to temperature,
the transmitting species, the climate, ete. Kinoshita has demonstrated that from
the odcyst onward the species of parasites can be differentiated. These differ-
ences become more marked, both morphologically and biologically, in the differ-
ent stages of schizogonic development and moreover produce different organic
reactions. The specific identity of all the parasites is a point now disposed of.
Few still defend this extravagance and among these there is only one of uni-
versal renown.

Another hypothesis, formulated by some authors, is in a similar position.
This is the hypothesis of the possible transmission to man of the Plasmodium of
monkeys, and, more startling, of other similar parasites of various animals.

Some points in relation to the malarial parasites still await future research
to better elucidate them. The hereditary transmission of the sporozoit to the
egg of the mosquito is a possibility indicated by Schaudinn. This investigator
also believed in a differentiation of the sporozoits into males, females and un-
differentiated. The belief in the possibility that another cycle may occur in the
mosquito, different from that already known and perhaps more rapid, can not
194 MOSQUITOES OF NORTH AMERICA

be summarily dismissed. The suspicion of such a possibility must occur to any-
one who has experience with the subject and who has observed that when in the
months of epidemic malaria the carriers of gametes, who serve as the means of
infecting mosquitoes for experimental research, are in very small proportion
and that nevertheless the epidemic increases with great rapidity. Withal it
will be futile to seek the explanation of this phenomenon outside of the mosquito,
where alone, sooner or later, it will be found.

Practically an Anopheles can become a transmitter in 10 to 12 days after
having fed. This period may be diminished under optimum conditions for the
vitality of the Plasmodium. It would appear from the few experiments in this
direction made with each species of Plasmodium that this period is variable.
The most favorable temperature appears to lie between 22° and 28° Centigrade.
Beyond these conditions the development of the parasite goes forward more
slowly and there are-observations which show a period of more than 50 days. In
hot countries, during the months of greatest heat, the proportion of malignant
tertian to the entire number of cases of malaria may reach as high as 96 per cent.
After this epoch the malignant tertian decreases and is replaced in proportion
by the benign tertian. The quartan malaria is generally everywhere much
the rarest form.

It is not rare in malarial countries to find children harboring ring-forms of
the parasites which are indistinguishable from Plasmodium falciparum and yet
these children present no symptoms of abnormal health except splenomegaly.
They are typical cases of imunitas non sterilans—immunes who, nevertheless,
are bearers of the parasites and therefore sources of infection. Do the parasites
lose their virulence, or are they a different species? We have already mentioned
that parasites exist in every way like those of malignant tertian but which in
their development produce attacks of a very benign character. Some authors
also report two clinical types of quartan malaria, one benign, the other malig-
nant; however it has been impossible to differentiate the parasites micro-
scopically.

Spontaneous recoveries from malaria can be observed with a certain frequency.
It is to this circumstance that the supposed efficacy of remedies other than
quinine is to be attributed. Of such remedies the only one of any value is
methylene blue which acts destructively upon the plasmodia, but its effect is slow
and in cases of acute malignant tertian it does not act with the necessary
rapidity and energy, as does quinine. Under certain conditions there may come
about the formation of races of Plasmodium resistant to quinine.

THE SCIENTIFIC DEMONSTRATION OF THE CARRIAGE OF MALARIA.

Before the actual demonstration of the carriage of malaria by mosquitoes
of the genus Anopheles,-a number of observers in different parts of the world,
in addition to those already stated, had announced their belief in the relation
between mosquitoes and the malady. By far the most forcible argument, how-
ever, was presented by Dr. A. F. A. King, of Washington, in a paper read before
DISCOVERY OF MOSQUITO ROLE 195

the Philosophical Society of Washington in 1882 and subsequently published in
the Popular Science Monthly for September, 1883 (vol. 23, pp. 644-658). This
paper attracted much attention in this country, but the author himself realized
that the arguments brought forth could not be held to prove the theory. He said,
however, “ they may go so far as to initiate and encourage experiments and ob-
servations by which the truth or fallacy of the views held may be demonstrated.”
The main arguments used by King were substantially as follows:

1. The malarial season corresponds to the season of mosquito abundance.

2. Malarial country is suitable for mosquito breeding.

3. Similar conditions afford protection against malaria and against mos-
quitoes.

4, Exposure to night air means exposure to mosquitoes.

5. Influence of occupation. Soldiers, tramps and fishermen are particularly
susceptible to malaria and are especially exposed to mosquitoes at night.

6. Turning up the soil or making excavations in previously healthy districts
is often followed by malaria, but this turning up of the soil gives opportunities
for water to accumulate and for mosquitoes to breed.

%. Coincidence of malaria and mosquitoes.

The scientific study of malaria may be said to begin with the far-reaching dis-
covery of the malarial parasite. Laveran, on November 6, 1880, first recog-
nized the organisms as minute protozoan parasites of the red blood-corpuscles.
He furthermore discovered the flagellate and crescent forms of the parasites
which were afterwards shown to be sexual phases of it. The idea that the in-
fection was brought about through mosquitoes was suggested by Laveran in
1884; by Robert Koch in 1892; and by Sir Patrick Manson in 1894. The
Italians Bignami and Mendini mentioned it in 1896, and Grassi in 1898.
Bignami and Dionisi are said to have conducted mosquito experiments which,
however, turned out negative, in 1893 and 1894. Manson, who had already
proved that mosquitoes acted as the transmitters in filariasis, pointed out that
there was probably a similar relation in malaria. He expressed his belief that
the flagella were spores and that they underwent further development in the
mosquito.

Following the publication by Manson, in 1894, of his theoretical induction that
the gametes of malaria undergo further development in mosquitoes, Dr. Ronald
Ross, of the Indian Medical Service, commenced, in May, 1895, certain re-
searches in the hope of demonstrating this hypothesis by practical experiment.
He was then stationed in India, and almost immediately proof that the gametes
undergo their peculiar changes more readily in the stomach of mosquitoes than
elsewhere was obtained. Then followed two years of arduous work with mos-
quitoes of the genus Culex without the desired results. In August and Sep-
tember, 1897, however, in Secunderabad, he succeeded in following the develop-
ment of the parasites in Anopheles mosquitoes, and his results were published
in the British Medical Journal for December 18, 1897, and February 26, 1898.
The following year he was unable to work with human malaria on account of
the public agitation against plague inoculation in Bengal, so he determined to

14
196 MOSQUITOES OF NORTH AMERICA

study the malaria of birds. As the result of work carried on from March to
August, 1898, he completely demonstrated the life-history of a malarial organism
in birds. He succeeded in infecting healthy birds by the bites of infected mos-
quitoes, the species being identified as Culex fatigans.* Before this (in 1897)
MacCallum of Baltimore had found that with Halteridium of birds the flagella
and the pigmented spheres represented sexual forms of the parasite, the flagella
impregnating the spheres. He was able to observe this process with malarial
parasites of human blood. Thus the general law of infection and of the develop-
ment of the malarial parasites was established.

Grassi, approaching the subject from another viewpoint, conceived the idea
that the disease and its transmitter must be coincident and that therefore the
host relation of the malarial parasite is restricted to definite mosquitoes. He
carried out most careful studies, which proved this to be the fact and showed
that mosquitoes of the genus Anopheles alone are concerned in the trans-.
mission of malaria in man. In 1898 Grassi, together with Bignami and Bas-
tianelli, was working in Italy upon the malarial problem ; on November 28 they
reported finding developmental stages of the malarial parasite in the stomachs
of two Anopheles claviger, fed on patients with malarial crescents in their
blood. On December 3, in the London Lancet, Bignami described the first suc-
cessful infection (of a man named Sola) by an infected Anopheles. Later
numerous valuable publications by the Italian investigators followed. Ross’s
finding of the pigmented cells in Anopheles mosquitoes, in August, 1897, and his
complete demonstration of the life-cycle of a malarial organism of birds, entitles
him to the credit of the complete scientific demonstration of the relation between
mosquitoes and malaria, a fact which, though still disputed by certain of the
Italian school, has been recognized by most writers and has brought him the
Nobel prize in medical discovery. To Grassi belongs the credit of the discovery
that human malaria is only transmitted by Anopheles mosquitoes. Later work
by investigators of many nations has resulted in an extensive knowledge of the
life-history of the causative organisms of malaria, and a number of species be-
longing to Anopheles have been proved to be secondary hosts of the malarial
parasites of man. The Italian workers, Machiafava and Celli, and those above
mentioned, Koch, and above all Schaudinn, of Germany, Laveran and Marchoux,
of France, Manson, Ross, Daniels, and others, of England, have all contributed
to the final results. It is perfectly demonstrated that the full development of
the malarial parasite can not take place within the human body, and that certain
species of Anopheles mosquitoes are the necessary secondary hosts, the sexual
generation of the parasite taking place only in these mosquitoes.

Some especial attention must be give to the work of Robert Koch on account
of his large share in malarial investigation, not only from the scientific, but also
from the practical side. In Italy, in the autumn of 1898, he was able to find the
various stages of Proteosoma in birds and in mosquitoes. He succeeded in in-
fecting mosquitoes by allowipg them to feed on birds harboring the parasites.
Koch continued the ivetigon in Berlin, and in the middle of November fol-

 

*=Culea quinquefasciatus Say.
PROOF OF MOSQUITO ROLE 197

lowed the developmental stages of the parasite to the end, thus verifying the dis-
coveries of Ross. He had in June of the same year, without knowledge of Mac-
Callum’s investigation, detected the process of fertilization and the function of
the flagella as spermatozoa.

In the course of his malarial investigations in Java, late in 1899, Koch dis-
covered that when malaria is endemic it is often confined almost entirely to the
children, a fact which he had already noted previously in East Africa; the adults,
therefore, that have survived have acquired a certain degree of immunity.
Koch found that very little malaria was in evidence in localities which seemed
to be favorable in every way. He therefore sought a native village, which was
situated in the midst of swamps and offered optimum malarial conditions, for
the purpose of making blood examinations of the natives. He found that the
adults did not suffer from malaria while a large percentage of the children did,
the youngest ones being worst infected. Koch’s discovery of the frequent in-
fection of naked children in the tropics, Ross considers to be one of the highest
importance. It indicates the possibility of the disappearance of the effects of
malaria, and that such apparently immune individuals, harboring the malarial
parasites, are the source of most malarial infections in the tropics.

Large scale practical demonstrations were soon made. One of the most in-
teresting was that carried on in Italy by Professor Grassi during the summer of
1900 in the Plain of Cappacio near Salerno. The objects of this experiment
were: (1) To afford an absolute proof of the fact that malaria is transmitted
exclusively by the bite of mosquitoes; (2) To formulate, in accordance with
the results, a code of rules to be adopted to free Italy from malaria within a
few years. The experiment consisted in protecting from mosquitoes rail-
way employés and their families along about 12 kilometers of railway in an
intensely malarious region. These people lived in ten cottages and two stations
at St. Nicolo, Varco, and Albanella, situated along the Battipaglia-Reggio Rail-
way. They numbered 104 persons, including thirty-three children under ten
years of age. Of these 104 individuals, at least eleven, including four children,
had never suffered from the disease, not having previously lived in a malarious
district ; a certain number, it appeared, had not suffered from it in two or three
years, and all the others, that is to say, the large majority, had suffered from it
during the previous malarial season, some of them even in the winter. During
the malarial season, the health of the protected individuals was exceptionally
good ; there were a few cases of bronchitis and one of acute gastro-enteritis, and
none of these cases were treated with quinine. Among these 104 persons, only
three cases of malaria appeared and these were clearly relapses from malaria
acquired the previous year. The unprotected neighbors, however, without excep-
tion, contracted malaria.

Another very striking experiment which, during the autumn of 1900, was
mentioned in newspapers all over the world, was that performed by Doctors
Sambon and Low, of the London School of Tropical Medicine, in the Roman
Campagna, reputed for its malaria, during more than three months of the late
summer and early autumn of 1900. They had constructed a comfortable little
198 MOSQUITOES OF NORTH AMERICA

five-roomed wooden house about three hours drive from Ostia, in one of the
most malarious portions of the Campagna. The house was tightly built and was
thoroughly screened. The experimenters, together with a Signor Terzi and two
Italian servants, lived in this house through the period when malaria is most
prevalent. They took no quinine and no health precautions beyond the fact
that at sundown each day they entered the house and remained there until
daylight the next morning. Dr. Rees, of the London School, visited them and
occupied the house with them for a portion of the time, and all three conducted
laboratory work in one of the rooms, which was fully equipped for such a pur-
pose, and led a busy and contented life. They explored the neighboring swamps
and woodlands and visited the neighboring villages. They received and en-
tertained many visitors who were interested in the experiment. They always
turned indoors before sunset and then stood at the windows and timed the first
appearance of Anopheles, which would come at a certain hour each evening and
try to enter the screened windows and doors. As Dr. Rees expressed it, “ It
must have been very tantalizing for them to be unable to get at us.” When the
rains set in, everyone said that that was the critical time of the experiment.
The people in the surrounding country became ill generally with malaria, the
chilling caused by the rain having brought about an explosion of the fever.
The experimenters, however, went out into the rain and got soaked to the skin,
but their health remained perfect. Not the slightest trace of malaria de-
veloped in any of them. As above stated, the spot where the house was built
was probably the most malarious one in the whole Campagna, and it was situated
on the banks of one of the canals, which literally swarmed with Anopheles
larve. The prevalent idea that the night air of the Campagna is in itself so
dangerous was included in the experiments and the windows were always left
open at night, so that if the marsh air had anything to do with malaria they
would have contracted it.

A check experiment was carried on at the same time. Anopheles mosquitoes,
which, under the direction of the Italian doctors Bignami and Bastianelli,
had been fed on the blood of a sufferer from malaria in Rome, were sent to
London early in July. A son of Sir Patrick Manson offered himself as a subject
for experiment and allowed himself to be bitten by the mosquitoes. He had
never been in a malarious country since he was a child and was in perfect health,
but in due time he was taken with a well-marked malarial attack of the benign
tertian type ; microscopical examination showed the presence of the parasites in
his blood. Later a second subject, also an Englishman, who had never suffered
from malaria, submitted to the experiment, allowing himself to be bitten by
infected mosquitoes sent from Rome. He also developed malaria after two
weeks and the parasites were demonstrated in his blood.

Another early experiment on a large scale, to control malaria through pro-
tection from mosquitoes, was carried on in 1900 by Fermi and Tonsini on the
Island of Asinara. This island is north of Sardinia, and inhabited only by
convicts and their guards. After a close study of the malarious localities, and
mapping of the mosquito breeding places, measures were taken for (1) de-
KOCH’S CONTROL WORK 199

struction of mosquito larve (petrolizing pools and emptying tanks and tubs
completely twice a month) ; (2) destruction of adult mosquitoes in the convict
dormitories with pyrethrum powder, ‘zanzolina,’ chlorine gas, etc.; (3) pro-
tection of habitations against mosquitoes by screening doors and windows. The
results in one season were: Anopheles almost never found (and other mosquitoes
much more rarely than formerly) in dormitories. Not a single primary case
of malaria developed, the new cases, nine in number, were all importations or
relapses. The previous year there had been ninety-nine cases, of which about
forty-four originated on the island.

Since that time the relation of the mosquito to malaria has become the
common knowledge of the civilized world, and many regions have been freed
from the disease by anti-mosquito work. Some of these have been mentioned in
other sections of this work.

Koch, in 1900, at Stephansort, in German New Guinea, conducted a vigorous
anti-malaria campaign to determine if malaria could be eradicated from a given
locality. His work was based on the idea of destroying the parasites in the blood
of man by means of quinine and thus depriving the mosquitoes of the source of
infection. In the first place, by the microscopic examination of the blood, all the
persons of the community in whom malaria was latent were discovered. These
potential transmitters of the disease were treated with quinine, administered
methodically at regular intervals until the parasites had disappeared from the
blood. Every one of these, at intervals of ten or eleven days, was given one gram
of quinine on two successive mornings. When necessary the intervals were
shortened and the doses of quinine increased. In this manner Koch succeeded,
in the space of a few months, in almost wholly eradicating malaria from
Stephansort. The results of Koch’s experiments indicated that this method of
destroying malaria, so that there is no disease for the Anopheles to transmit,
may be most useful under certain conditions. Koch protests that his method
differs radically from the so-called quinine prophylaxis with which it has been
frequently confused. This latter method aims to prevent the infection of man
and, to be effective, would have to be applied to all the inhabitants of a malarial
Tegion.

Dempwolff later continued the work of Koch in German New Guinea. He
found, when he tried to apply the Koch method on a large scale, that the method
has its limitations. He found much difficulty in making the necessary blood
and spleen diagnoses, not only in the prejudice and superstition of the natives,
the shifting character of the population, but often in the indifference of the
European settlers as well. Dempwolff points out that the prospects are much
more hopeful when the Anopheles appear only at a certain season and one can
hope to break the chain of the malarial organisms from one season to another.
He points to the results, under such conditions, of Vagedes in Franzfontein
(German South-west Africa), Frosch in Brioni (Istria) and Ollwig in Dar-
es-Salaam (East Africa).

Tt should be here stated that cinchonization was tried in 1903 by Edmond
and Etienne Sergent in France at Saint-Philbert de Grand-Lieu, but their
200 MOSQUITOES OF NORTH AMERICA

effort, based exclusively upon Koch’s method, did not give good results. They
found it difficult to make exact microscopic diagnoses, and also found it im-
possible to give agricultural laborers the doses of quinine prescribed by Koch,
since such doses incapacitated them from work and made them refuse subsequent
treatment. Giving the doses recommended did not in two cases prevent the re-
appearance of the fever. They concluded that, if the results obtained by them
in this test are compared with the results which they obtained in Algeria by
mechanical defense against mosquito bites and the use of petroleum against
their larve, there can be no doubt about the superiority of the latter methods.
The theoretical idea of the disinfection of the blood of malarious patients is
very logical, provided that the quinine actually kills the parasite in all its stages.

Quininization has been used in many of the British colonies, not entirely on
the Koch plan to use it as the sole means of doing away with malaria, but as an
auxiliary, and with considerable success. In British Guiana, as pointed out by
Boyce, the government gives out quinine at the postoffices to laborers, and he
states that it is sought after and does good.

In Italy very marked results have followed the general use of quinine, intro-
duced by the government and encouraged in every possible way. There was
already a very marked reduction of malaria in the first years following the dis-
covery of the transmission of the disease by mosquitoes, when many efforts were
made to control malaria through the mosquito. Further improvement was
brought about by extensive drainage operations, but the statistics show that
with the introduction of the free use of quinine there was a great reduction in
the, until then still high, malarial rate. Professor Celli is the strongest advo-
cate of the extensive use of quinine. He believes that by this means alone
malaria can be controlled in Italy and that other measures are negligible.
There has been much opposition to his view, but he argues that drainage
measures, while theoretically the ideal method of malaria control, can not be
carried out in a sufficiently perfect manner to insure results. He points out
that drainage can never be perfect and that the smallest collections of water will
furnish breeding places for Anopheles. Furthermore, agricultural irrigation
works, established on the reclaimed lands, have unavoidably established new
breeding places for Anopheles. It seems to us that neither method alone would
have given the results now obtained, but just what share should be credited to
the different methods would be difficult to determine. Certainly in Italy the
general use of quinine appears to have very materially reduced malaria. The
accompanying maps, from Professor Celli’s paper in the Atti della Societa per
gli Studi della Malaria, vol. xi, 1910, show the wonderful improvement which
has been brought about in malarial conditions in Italy through the modern ideas.

Stephens and Christophers state that a prophylactic method was tried with
considerable success at one point in Africa. This consisted in removing the
residences of the Europeans to a distance from the native town, and thus, from
the source of infection. “Several years ago at Accra, Gold Coast, the residences
of the officials were removed from Accra town to an unoccupied site about half
a mile from any native dwellings, since called Victoriaborg. ‘This is almost the
MORTALITY FROM MALARIA IN ITALY IN 1903

MORTALITY FROM MALARIA IN ITALY IN 1900

Mortality per 1000 population

Mortality per 1000 population

[-__] From 0.00 -to 0.010

[____] From 0.00 to 0.010
ESg

“0,010 ‘* 0.050

“0.010 ** 0.050

0.050 ** 0.100

“* 0,100 ** 0,200
0.200 ** 0.400

=

0,100 ** 0.200

0.400 ‘* 0.600

“0.400 ** 0.600

EREa
SS

MALARIA CONTROL

0.600 ‘* 0.800

        
  

201

Fie. 5.—Showing comparative mortality from malaria in Italy in 1900 and 1908.
202 MOSQUITOES OF NORTH AMERICA

only case we have seen where in Africa a scheme of segregation has been carried
out. The result has been to make Victoriaborg reputedly the most healthy
European settlement on the West Coast of Africa.”

THE MOSQUITOES THAT CARRY MALARIA.

No mosquitoes belonging to genera other than Anopheles have been shown to
carry malarial diseases of human beings. Culex quinquefasciatus has been
shown by Ross to be the necessary secondary host for a closely allied malarial
disease of birds, and other mosquitoes have been shown to carry malarial dis-
eases of other animals. At present our knowledge of malarial diseases in wild
animals is very slight. With the human species it will probably be ascertained
that many, though by no means all, of the species of the genus Anopheles, in its
broader sense, transmit malaria. Grassi, Bignami and Bastianelli have proved
that in Italy Anopheles maculipennis, A. bifurcatus and A. superpictus trans-
mit the various types of malaria. In Japan and Formosa, Tsuzuki deter-
mined that Anopheles jesoénsis, A. formosaénsis and A. cohesa are responsible
for tertian and estivo-autumnal malaria.* Dr. W. S. Thayer, in his chapter on
malaria, vol. 2, part 2, Allbutt & Rolleston’s System of Medicine, London, 1909,
indicates the following species as having been shown to carry malarial infection:
Anopheles bifurcatus (Hurope) ; A. maculipennis (Europe) ; A. quadrimacu-
latus (North America) ; A. jesoénsis (Japan); A. martini, A. pursati (Cam-
bodia) ; A. vincenti (Tonkin) ; A. listoni, A. culicifacies (India) ; A. funesta,
A. superpicta, A. paludis (West Africa); A. coustant (Madagascar and Re-
union) ; A. costalis (Africa) ; A. cruzi (Brazil) ; A. albimanus (Panama). Ac-
cording to Stephens and Christophers Anopheles listoni, A. culicifacies and A.
fuliginosus are the species principally concerned in India, and to these A. turk-
hudi has been added and A. jeyporensis is suspected. Kinoshita reports Anoph-
eles annulipes as transmitter of pernicious malaria in Formosa. Dr. Arthur
Neiva states that in Brazil Anopheles albimanus, A. argyritarsis, A. pseudo-
maculipes, and A. intermedium have been proved malaria carriers. HExperi-
mental work with Anopheles punctipennis in the United States was begun in
1902. Smith in New Jersey, on the 24th of September, caused a number of
specimens of the females of this species to bite a patient suffering with malaria.
These specimens were later examined by Dr. W. N. Berkeley, of New York City,
but without any definite result. Hirschberg reports the result of comparative
experiments with Anopheles quadrimaculatus and Anopheles punctipennis con-
ducted by feeding them with the blood of patients known to contain the parasite
of estivo-autumnal malaria. The results were that of 58 specimens of Anopheles
punctipennis fed, none were found to be infected, whereas of 48 A. guadrimacu-
latus fed, 8 were found to be infected. The same writer pointed out that the
distribution of the latter species in the vicinity of Baltimore coincided in a gen-
eral way with the occurrence of malaria-infected districts. The disease prevailed

 

% ee to Kinoshita Anopheles jesoénsis=A, sinensis, A. formosaénsis and A. cohesa=
. listoni,
MALARIA TRANSMITTERS 203

where Anopheles quadrimaculatus had its breeding-places, but was absent from
districts where A. punctipennis abounded. Smith, in his report of the New
Jersey State Agricultural Experiment Station upon the mosquitoes occurring
within the State (1904, page 158), discusses the relation of Anopheles to malaria
in New Jersey. Where Anopheles punctipennis is the abundant species malaria
is practically unknown ; while within the range of A. crucians malaria does occur,
it is by no means prevalent and A. quadrimaculatus is also found there and is
considered by him the responsible species. Dr. J. W. Dupree, however, has re-
corded the fact that the malarial relation has been established for Anopheles
punctipennis by himself. He further states that it has been established for
Anopheles crucians by Pothier and Beyer.

The discrepancies in the results of different investigators, which are par-
ticularly obvious in the above-mentioned experiments with Anopheles puncti-
pennis, may find an explanation in facts brought out by Professor Beyer and
his collaborators (Prof. George E. Beyer, Dr. 0. L. Pothier, Dr. M. Couret
and Dr. I. J. Lemann: Bionomics, experimental investigations with Bacillus
sanarelli, and experimental investigations with malaria, in connection with
the mosquitoes of New Orleans. N. Orl. Med. & Surg. Journ., Jan., 1902).
These investigators show that a definite species of Anopheles can be the host of a
certain type of malaria while other types of malaria can not develop within it.
In a series of careful experiments it was found by these students that Anopheles
quadrimaculatus became infected with the parasites of tertian and quartan, but
not of estivo-autumnal fever. On the other hand Anopheles crucians proved
to be the bearer of estivo-autumnal malaria while it remained wholly negative
to the other types of parasites. The results were obtained by feeding mos-
quitoes of both species upon humans in whose blood the malarial parasites were
found to be present, and, after a suitable interval, examining the mosquito for
the parasite. These experiments were repeated a sufficient number of times
with the different types of malaria and the two species of Anopheles to be
conclusive. They found further that the distribution of Anopheles crucians
about the city of New Orleans corresponded very closely with the distribution
of the cases of estivo-autumnal fever.

Kinoshita, in his studies in Formosa and Japan, found that the type of
malaria depends upon the species of Anopheles, and that, while in Europe
Anopheles maculipennis appears to be capable of transmitting all three forms of
malaria, this is not true of any of the Anopheles studied by him. In Formosa
the occurrence of pernicious malaria corresponds, both geographically and in
time, with the occurrence of A. listoni. “ Every epidemic of malaria tropica
depends upon the increase and decrease of A. listoni, of which, as determined
above, more than 50 per cent can transmit tropical malaria. This mosquito
develops very abundantly between the months of April and October. The new
infections of tropical malaria begin also about the end of April and reach the
highest number between June and July. Anopheles listont is generally more
abundant in mountainous regions than on the coast and the distribution of
tropical malaria corresponds. Taihoku, where A. listont does not occur, is there-

fore free from the tropical malaria.”
204 MOSQUITOES OF NORTH AMERICA

Kinoshita states further that Anopheles listoni does not occur in Japan and
that the country has always been free from pernicious malaria in spite of the
fact that persons suffering with pernicious malaria frequently come to Japan.
On the other hand, Kinoshita found that both in Formosa and Japan Anopheles
sinensis is the principal transmitter of tertian malaria. By experimentation
he found that about 50 per cent of this species became infected with tertian
parasites; quartan parasites developed in this mosquito only at low tempera-
tures and the parasites of pernicious malaria never. Another interesting point
in this connection is that he not rarely found new infections of tertian malaria
in winter, while this was not the case with pernicious malaria. The explanation
lies in the fact that in Formosa Anopheles sinensis is active throughout the
winter.

It will thus be seen that negative results with a given species of Anopheles
are not conclusive unless the experiments are conducted with all types of malaria
and under the most favorable conditions. Furthermore it would appear that
different species of Anopheles, where susceptible to the same types of malaria,
may be so in different degrees. Grassi, Bignami and Bastianelli, in their early
experiments, had found that a certain proportion of the Anopheles appeared to
be naturally immune and failed to develop the malaria parasite, even under the
most favorable conditions. This proved to be the case with all the species of
Anopheles and of parasites experimented upon by them.

In a recent paper Dr. Samuel T. Darling discusses the relation of the various
species of Anopheles to malaria in the Panama Canal Zone. His careful studies
show that Anopheles albimanus is the principal transmitter of malaria, both
wstivo-autumnal and tertian, in that region. He found that 70.8 per cent of
the individuals of this species which he induced to bite malarial patients became
infected. He also found that this was the species which frequented houses most,
constituting in Ancon, during October, 1908, 72.5 per cent of the Anopheles
found, and in some villages being the only species present. Of Anopheles
pseudopunctipennis it was found that 12.9 per cent of the individuals experi-
mented with became infected, while of 17 A. malefactor none became infected.
Anopheles argyritarsis and A. tarsimaculata were later found by him to be
malaria transmitters.

The brothers Sergent have recently found sporozoits, probably malarial, in
the salivary glands of Anopheles algeriensis and A. hispaniola in Algeria. In
addition to the malaria-bearing forms above mentioned, Theobald in the fourth
volume of his monograph lists Anopheles barbirostris, A. pseudopictus and A.
theobaldi as transmitters of the malarial parasites.

THE HABITS OF ANOPHELES MOSQUITOES.

The general points of difference between adults of this group and those of
other mosquitoes are very well understood, the long palpi of the female as con-
trasted with the short palpi of the females of most other mosquitoes, for example.
The other points of difference will appear from the systematic descriptions.
ASSOCIATION WITH MAN 205

While full descriptions, not only of the adults, but of the early stages of the
different species of malaria-bearing mosquitoes, together with some remarks
concerning the geographical distribution and habits, will be found in their ap-
propriate places under the systematic consideration of the genus Anopheles, later
in this work, some general consideration of their habits will be given here. The
general question of distribution is briefly mentioned under the head of geo-
graphical distribution of malaria.

RESTING POSITION OF ADULTS.

Much has been said concerning the resting position of Anopheles as compared
with that of other mosquitoes. It has been held that Anopheles always sits with
its body-axis at a considerable angle to the surface upon which it rests. This,
however, can not be relied upon for identification. When Anopheles rests upon
a surface, such as the wall of a room, the body is frequently held at only a
comparatively small angle to the surface; in fact, it is sometimes held parallel,
but more often at a considerable angle. The angle at which the body is held
differs with the species and is characteristic for it. The hind legs are frequently
in motion but as a rule hang down with more or less of a bend at the knee joint.
In whatever position Anopheles rests, the beak and the rest of the body are
practically in the same plane, whereas with other mosquitoes the beak and the
abdomen are by no means in the same place. In Culex and Aédes, for example,
the appearance is that of being humpbacked. During hibernation, the hind legs
are drawn in, and, for the most part, the body is brought close to the wall, as
observed by one of the writers (Howard) upon Anopheles quadrimaculatus
hibernating in barns in southern Idaho.

Giles has found an Indian Anopheles, which he claims has exactly the resting
attitude of a Culex. This caused him to give it the specific name culicifacies.
Grassi states that Anopheles superpictus holds itself rigidly perpendicular to the
wall, and the Sergents state that Anopheles hispaniola rests in the same perpen-
dicular attitude. Schiiffner has observed the same habit in a Sumatran species.
Peryasst states that Anopheles nimba rests and flies like a Wyeomyia, with the
hind legs raised and curved forward over the body.

SEMI-DOMESTIC AND WILD SPECIES.

Several of the species of Anopheles seem to be on the verge of becoming do-
mesticated, like Culex pipiens, and the yellow-fever mosquito, and are commonly
found about houses. They attempt to enter houses at the times during which
they are active and, once inside, remain there. They seek cellars, attics, barns,
and outhouses for hibernation purposes. They often find shelter elsewhere, as
under culverts and other protected places, but they seem to prefer to get into
buildings if possible.

Mr. A. H. Jennings has pointed out that, in the Canal Zone, Anopheles
albimanus is the semi-domesticated form and occurs everywhere about houses
and villages. This species, in fact, is the great carrier of malaria in the Ameri-
can tropics. Away from civilization, in Panama and the neighboring countries,
206 MOSQUITOES OF NORTH AMERICA

Mr. Jennings states that this species is very rare or can not be found at all, but
Anopheles eiseni takes its place as a wild, undomesticated species.

James and Liston have a significant statement which bears upon this differ-
entiation in regard to domesticity among the different species of Anopheles in
India.

“Tt is a well recognised fact that some species of ‘ anopheles’ are more com-
monly found near villages and dwellings than others. We may, in fact, divide
these insects broadly into two classes: the ‘ domestic’ species, which are usually
found near human dwellings, and the ‘ wild’ species, which are rarely found in
houses. Of the first class, A. rosst is a typical example, and of the second A.
barbirostris. Some species would appear, as regards this habit, to occupy a place
intermediate between the typically domestic and the typically wild species.
A, fuliginosus, for example, may, in certain parts of India, be found in enormous
numbers in the sheds and outhouses on the outskirts of a village, while in other
parts, though large numbers may be caught in tents pitched at some distance
from a village, few or none will be found in the houses of the village itself.

“Tt is usual to say that the greater the number of ‘ anopheles’ there are in a
place, the greater will be the prevalence of malaria. This is not by any means
borne out by experience. We have already mentioned that some species of
‘anopheles’ are better malaria-carriers than others, and apart altogether from
the fact that ‘ anopheles’ may be abundant in a place without there being any
malaria there at all, it often happens that the species which is present most
abundantly is not the one which is carrying malaria at the time. It is, however,
a difficult matter to estimate the relative abundance of different species in any
place, for some are much more easily seen than others, and the habits which some
species have of secreting themselves among the straw of a thatched roof and of
resting only upon objects which are as nearly as possible the same colour as they
are themselves, are very important. In order to exemplify this, it seems worth
while to recount an instance which happened in our experience. In the malari-
ous village of Ennur in the Madras Presidency, A. rossi was so abundant that on
almost every straw of the thatched roof of every house three or four specimens of
this species were resting. A careful search in the ordinary way did not reveal the
presence of any other species, and it is certain that, had there been no other
object in the search than the mere determination of the species of ‘ anopheles’
present in the village, the observer would have gone away quite satisfied that
A. rossi was alone present. But the village was an extremely malarious one, and
knowing that A. rossi was an inefficient carrier of malaria in nature, he was
unwilling to believe that no other species was present in the houses. Fixing his
mind, therefore, upon the thought that he was looking for A. culicifacies and not
for A. rossi, he again commenced the search with great care, and was rewarded
not only by detecting the presence of A. culicifacies, but by catching a sufficient
number of this species during several days’ work, to prove that it was the species
responsible for the prevalence of malaria in the place and not the very much
more abundant species A. rosst.”

HIBERNATION AND ZESTIVATION.

Anopheles pass the winter, for the most part, in the adult condition. In
regions with a rigorous climate the fecundated female is the only form that sur-
vives the winter and starts a fresh generation with the return of mild weather.
Smith has shown that in New Jersey they begin to seek winter quarters in Sep-
tember. He dissected specimens during the winter and found the alimentary
canal empty and the ovaries undeveloped. In the early winter he found the
ANOPHELES AND MAN 207

abdomen filled with a fatty mass, but in the early spring the fatty mass had
disappeared. In cellars and in attics they remain motionless on the walls,
or under shelves in pantries. Professor Hodge, of Worcester, Massachusetts,
has found them resting under such pantry shelves in winter literally by thou-
sands. This points out the great desirability of cellar fumigation in winter in
malarial regions, as will be shown under the head of remedies. In Washington,
adults often appear in houses during the winter when stimulated by high tem-
perature. Under such circumstances they have been known to bite even in mid-
winter, although it would seem that it is only a small proportion of the hiber-
nating individuals that become active. Giles has found that in the colder
portions of northern India, Anopheles hibernate, and he points out that they
pass the intense dry heat of the early summer in much the same condition.
Grassi found that Anopheles can not withstand the same amount of desiccating
heat as other mosquitoes. Stephens and Christophers state that in India the
Anopheles pass the hot, dry season in houses, and although they feed at intervals
they will not lay eggs even if artificial breeding-places become available. James
and Liston, in India, found eggs, young larve, and pup of two species during
the winter in newly made breeding-places and another species was able to hiber-
nate in the larval condition. Giles on the other hand shows that in many locali-
ties in India Anopheles may be found in all stages practically every month in
the year, decreasing in numbers in the hot weather and increasing in the rainy
season, the determining factor undoubtedly being the moisture conditions.
Hibernating larve have been found in Italy and Galli-Valerio and Rochaz de
Jongh have demonstrated that the larve of Anopheles bifurcatus hibernate
normally in Switzerland.

FEEDING HABITS OF ANOPHELES.

The feeding habits of the female Anopheles have an important bearing on
the malarial relations of these mosquitoes. It has already been pointed out that
certain species of Anopheles occur more or less in association with man and these
species are the important malaria carriers. Other species show, at least, no
preference forman. Thus, for example, Jennings has observed that, in Panama,
Anopheles eiseni is the abundant species in regions uninhabited by man, while
A. albimanus, which is the chief malarial agent in the American tropics, is
absent from such localities. The Anopheles found in localities uninhabited by
man must have recourse to other animals to procure blood. Schiiffner asserts
that a species of Anopheles found by him in Sumatra could not be induced to
suck blood. On the other hand, he remarks on the extreme voracity of another
species, and this last species proved to be instrumental in the transmission of
malaria. “ When the animals have an empty stomach it is sufficient, in order to
feed them, to put the hand into the cage. Instantly this is covered with them,
and one feels, from the slight burning sensation which follows immediately, how
rapidly they can sting. When they have once begun to suck they do not easily
allow themselves to be disturbed ; one can touch and shake them without succeed-
ing in driving them away. Therefore there is no trouble in capturing them while
208 MOSQUITOES OF NORTH AMERICA

feeding. The voracity of the animals is incredible. An ordinary Culez, after it
has sucked its fill, flies away. These Anopheles, however, are not satisfied with
this but continue to suck, making more room by discharging the surplus through
the anus. At first they discharge the faces and intestinal liquid, but afterwards,
drop by drop, pure blood follows. So, before it chooses to fly away, it flushes its
digestive tract with three to four times the amount of bood which would have
been necessary to fill its stomach.”

Grassi, in Italy, was the first to study carefully the habits of Anopheles and
his observations still stand unsurpassed. He believes that the normal food of
Anopheles is blood, and, if they can find it, exclusively that of warm-blooded
animals. They prefer the blood of mammals, but he found that sometimes they
would, as it seemed with some reluctance, suck the blood of birds (poultry,
sparrows and hawks). Grassi does not believe that there is a predilection for
particular mammals, but that they are attracted in proportion to the size of the
animal, the larger animals appealing more strongly to the olfactory sense of the
mosquitoes. He found that frequently, when a man and horse were near each
other, the horse would be bitten many times before the man was bitten at all. On
the other hand, in the case of a man and rabbit, the man is generally attacked
first.

Grassi found that under proper conditions Anopheles will bite in the open, in
houses and in stables. He states that in-malarial regions it very often happens
that, in the evening, when persons are sitting at their doors, they are attacked
by great clouds of Anopheles. He found that in the summer the Anopheles,
after having procured a blood-meal within the house, seeks a hiding place
outside where it can digest the food. It does not fly far but hides in the foliage
near by and returns to the same place to obtain another meal of blood. During
the day they remain quiescent among the herbage, upon the under side of leaves,
selecting a spot where they are best protected from sun, rain and wind.

Grassi found that in the winter the Anopheles sought shelter in houses and
particularly in stables, and that, while with low temperatures they remained
quiescent, if the temperature rose they would suck blood. The preference of
Anopheles for stables has been repeatedly observed. Kinoshita, in Formosa,
found Anopheles abundant in stables and he utilized these in his studies on
malaria, for it proved that such Anopheles were all free of malarial parasites.
Mihlens, in his studies of some malarial epidemics in northern Germany, made
some interesting observations on the preference of Anopheles for stables. In
the spring of 1907 and 1908, at Bant in the vicinity of Wilhelmshaven, he found
the Anopheles preponderatingly in the warm stables of cattle and hogs, where
they had hibernated. They were rare in the cellars of houses, while, on the con-
trary, Culex were abundant in the cellars but rare in the stables. The Anopheles
fed through the winter and showed a preference for the animals over man. The
stomach contents of the Anopheles from stables were tested by the Uhlenhut
process and it was found that they consisted of the blood of cattle or hogs, ac-
cording to whichever animal they happened to have been associated with. As
already pointed out by Grassi, two factors probably determine the preference of
TIME OF ACTIVITY 209

Anopheles for stables. The size and number of animals exercise a strong at-
traction upon the Anopheles, and the even warm temperature within the stables
is probably another influence.

Anopheles females will feed upon other substances when they can not obtain
blood. Grassi states that Ficalbi has seen them sucking the juices of fruits and
the filth in out-houses. Grassi and Noé have surprised Anopheles feeding upon
unripe ears of Indian corn and sucking green grasses; they have noted that they
would, in time of need, absorb dirty water and they have seen them attracted to
sweetened water.

Grassi states that Anopheles first sucks blood two or three days after emerging
from the pupa and that in cool weather a longer time passes. Darling, in
Panama, found that they would bite after 24 or 48 hours. Peryasst states that
Anopheles argyritarsis and A. albtimanus will sometimes suck blood ten hours
after emergence. Many observations show that Anopheles suck blood frequently
under favorable conditions. Neiva made careful experiments on this point and
found that the various Brazilian species would suck blood at intervals of 24
hours or even more frequently. In Italy it has been observed that the Anopheles
fed upon successive days even when they had not fully digested the previous
meal. Neiva noted that weather conditions had a marked effect on the activity
of Anopheles. When there is a change of weather and rain threatens the Anoph-
eles are numerous and bloodthirsty. During rain they remain quiescent but
become active afterwards, even if a heavy rain has fallen for some hours. Neiva
found that on very hot days the Anopheles also attacked with great ferocity.

Little is known of the feeding habits of the male Anopheles. Grassi thought
that the males normally feed on the juices of fruits and he has kept them alive
on this food for 25 days. It is probable that the males of Anopheles suck the
honey of flowers, as do those of other mosquitoes. There are several records of
Anopheles visiting flowers but the sex is not mentioned and it is probable that
the females also resort to flowers when their normal food fails them.

NOCTURNAL AND DIURNAL HABITS.

Most of the Anopheles fly preferably at twilight. This fact was turned to
practical account in the first anti-malarial work in Italy. Grassi found that,
while occasionally Anopheles will bite during the day, their time of normal
activity is at twilight, and in reality very short. He observed that on un-
clouded days, during June, July and August, the period of greatest activity
lasted from 30 to 40 minutes and they would disappear before the obscurity be-
came complete. At first they would come in small numbers and these increased
until the maximum was reached after about 20 minutes; then they would again
decrease in numbers. On cloudy days they would come earlier and remain
longer, the governing factor being the amount of light. The Anopheles would
appear when it was still light enough so that one could read easily, and when it
became so dark that it was hardly possible to read the Anopheles disappeared.
The Anopheles were active both during the evening and morning twilight but
their number was much greater in the evening. In some cases a certain number
210 MOSQUITOES OF NORTH AMERICA

of Anopheles remained on the window screens from evening until the following
morning.

Grassi found that Anopheles will bite even at night if the temperature is high.
He found them very troublesome on a calm night when the moon was shining
brightly. They proved very annoying up to 2 a. m., but after that the tempera-
ture fell and none were felt up to 4 a. m.; between 4 and 6 a. m. they again bit
in the fiercest manner. The above observations apply to the hot plains of central
and southern Italy. In northern Italy the time during which Anopheles bites
is much restricted on account of the low night temperature.

When it is windy no Anopheles are seen or felt. On calm evenings they come
in clouds and it may happen that on the next evening none appear. In suffi-
ciently shaded localities it is not rare to have Anopheles bite out of doors during
the day and this is also the case in houses which are not well lighted or when
the day is cloudy. Cases of Anopheles biting in sunlight are very rare. During
the day Anopheles, when hungry, will bite if a victim happens to be near, but
they will not go far to obtain food.

Grassi further states that Anopheles do not come directly to artificial light,
but they are attracted to the edge of the illuminated zone. A method of getting
rid of the Anopheles and other mosquitoes in a room, indicated by Grassi, is
based upon their preference for a certain amount of light. In the evening the
room is closed and the light allowed to enter only through a single aperture;
the mosquitoes will then leave by this opening. This expedient is only successful
at twilight; during full daylight the mosquitoes can not be induced to leave in
this manner.

Careful observations in Brazil, by Doctors Chagas and Neiva, show that the
different species of Anopheles follow each other in regular sequence in the
evening and morning twilight. Thus Neiva found that, at Xerém, Anopheles
pseudomaculipes appeared first, later Anopheles intermedium, and last, when it
is already quite dark, Anopheles mediopunctatum. Anopheles albimanus and
argyritarsis appear together as soon as the twilight begins and remain until
dark. Apparently the activity of each species is governed by a definite amount
of light and on this account the time of appearance and disappearance of a
species varies with the season and with the weather conditions. Generally the
time for biting lasted but thirty minutes but this was extended on moonlight
nights. These observers found that with artificial light the Anopheles bite at
all hours of the night but they doubt that they bite in absolute darkness. In the
morning the Anopheles appear when it is already much lighter and remain
longer, but they appear in much smaller numbers. In the forest every species of
Anopheles comes to bite during the daytime but not in such numbers as in the
evening. Dr. Neiva found that Anopheles brasiliensis attacked man and animals
in open fields in the hot sunshine, and immediately after a rain it appeared in
true swarms, characteristic for this species.

Anopheles crucians, according to Smith, bites during the day, and the same
authority has upon rare occasions seen Anopheles punctipennis bite in the after-
noon on porches in New Jersey. One of us (Knab) has been attacked by this
SONIFACTION OF ANOPHELES 211

species in full sunlight, early in the spring, in Massachusetts. Smith states that
Anopheles crucians bites readily from sunrise until 11 a. m., and from 3 p. m.
until after dark. In his opinion it will bite any time during the day, provided
the victim is in a cool and sheltered location. Captain Fernside, I. M. S., ac-
cording to Giles, has seen an Indian Anopheles (presumably undetermined)
“feed greedily in the daytime,” and a number of similar observations might be
quoted.

Rev. James Aiken, in his “ Notes on the Mosquitoes of British Guiana” (5th
Series), in the British Guiana Medical Annual for 1908, shows that at least one
species of Anopheles bites during the day in British Guiana. His statement
is as follows:

“ Anopheles during the day never by any chance attack in front, but in-
variably settle on some part of the anatomy invisible to the eyes of the subject
to be bled. I have often experimented with a hungry albipes, turning round
and following her with my eye as she vainly endeavored to lodge on the back of
my neck. As J am still somewhat sensitive I have sometimes occasion when

seated on a cane chair to rise and interpose a sheet of newspaper or some such
protection from the subtle attack of this troublesome gnat.”

THE NOTE OF ANOPHELES.

The senior author pointed out in 1900 that there is a distinct difference be-
tween the buzzing sound or hum of Anopheles quadrimaculatus and that of Culex
pipiens, in that the former is indisputably lower in tone. His attention was
called to this by Mr. F. C. Pratt, who believed that he could at once distinguish
the two insects from the pitch of the hum as he was sitting reading in his house
in Virginia. The note of Culex, as it approaches the ear, is higher in pitch and
that of Anopheles is certainly several tones lower and not so clear. This differ-
ence becomes at once perceptible by confining the respective insects under gauze
in a breeding-jar.

Some interesting experiments on the sounds produced by Anopheles were
made by Nuttall and Shipley, who found that by cutting off more and more of
the wing the sound decreases in volume, the pitch rising progressively.

“When the wing was cut off quite closely, a very high-pitched note of slight
intensity remained, this as we supposed being produced by an internal apparatus
such as Howard indicates. It may however be due to respiratory movements
which are exaggerated through the efforts at flight, the sound is not produced by
the insect in repose. We found that the males gave a higher-pitched note than
the females, and that the note was higher in both sexes when they had fed; the
greater the meal, the higher the note. Of four unfed females three gave notes
within a quarter of a tone of 264 (i. e., of 240 to 270 vibrations), the fourth
female gave an abnormally low note of about 175 vibrations. Four other females
were arranged in the order of the distension of the abdomen by food, the last
being largely distended, these gave notes corresponding roughly to 264—281—
297—317 vibrations or according to the musical scales, the notes:

é ce = :

“Three unfed males gave exactly the same note, viz. corresponding to 880
vibrations = immediately after feeding one gave the note A #, another

15
212 MOSQUITOES OF NORTH AMERICA

which had fed well BY. The unfed males were more closely concordant than
the unfed females, the latter varying over about a semitone. Mr. J. W. Cap-
stick, M. A., Fellow of Trinity College, Cambridge, to whom we are greatly
indebted for making these ear determinations for us by means of tuning-forks,
was not certain that the note given by the males was not one of 440 vibrations.
Overtones were obviously strong and it sounded at times as if there were a faint
note of 440 vibrations overshadowed by a strong one of 880.

“The obvious explanation of the higher note given off by the males is that
their wings are markedly narrower and shorter than those of the females. Al-
though a female Culex pipiens gave a higher pitched note than a female A.
maculipennis, we are not at all sure that it was not simply due to the smaller
size of the former insect. The male of this species of Culex certainly gave a
higher pitched note than the female.”

DISTANCE OF FLIGHT.

Distances to which malarial mosquitoes will fly is a very important point in
the consideration of malarial prophylaxis. It seems reasonably sure that they
are much less capable of extended flight than many other mosquitoes and that
ordinarily they travel but a very limited distance. Statements that Anopheles
fly a long distance may be set down as based upon faulty observations. Thus
Craig has recently stated that he determined a flight of Anopheles of two and a
half miles in the Philippines. The difficulty of determining, in a tropical region,
that no breeding-places are present within a radius of two and one-half miles
must be obvious. When we consider that Anopheles larvee may exist in the
water-filled foot-prints of animals, and that these may be hidden by vegetation,
that furthermore they may breed in hollows in trees, or in water-bearing epi-
phytic plants, the task of determining with absolute certainty the absence of
breeding-places over a large area will be clearly seen to be impossible. Grassi
already pointed out that on account of the absence of scaly covering these mos-
quitoes are less able to withstand desiccation than others and that, therefore,
they can not cross large areas which afford them no shelter from the direct rays
of the sun.

Pressat, who made careful studies at Ismailia in Egypt, objects to the state-
ment of certain authors that Anopheles fly very long distances and points out
that they are not capable of sustained flight. He affirms that, when Anopheles
are present, careful search will reveal breeding-places within a distance of a few
hundred yards. Pressat admits that under certain conditions Anopheles, pro-
gressing by stages, travel considerable distances. When they are found at great
distances from their breeding-grounds they have reached the place in a passive
manner, transported by wagon, by railway or by boat. They may travel with a
caravan, as he determined by actual observation at Ismailia, by resting upon the
animals, the baggage or clothing. Pressat believes that Anopheles can not cross
a region denuded of vegetation, or a considerable expanse of water. On the other
hand wooded country affords them the necessary shelter and the animals found
there furnish them food.

Celli has concluded, from his observations in Italy, that Anopheles do not fly
farther than from 200 to 350 meters. When at greater distances from their
FLIGHT OF ANOPHELES 213

breeding-places they have traveled passively. They may be carried by a light
wind but in that case the limit is two kilometers. Dr. J. M. Young, of the
British Army, after extensive observations in China, came to the conclusion that
as a rule malarial mosquitoes will not fly over two hundred yards.

Stephens and Christophers, however, in their reports on the malaria expedi-
tion to Sierra Leone, state that under some conditions Anopheles may fly much
greater distances than has been supposed. In one small inland house which had
been occupied by one old man, five and six Anopheles were to be caught each
morning. These were fresh from pup and could only be derived from the
breeding-place three to four hundred yards away. The same writers have also
demonstrated a flight of six hundred yards. The Royal Society’s malarial com-
mission in India found that, in certain villages in the central provinces, Anoph-
eles culicifacies, A. stephensi, and A. fuliginosus were always present if there
were extensive breeding-places within a quarter of a mile, but that villages which
were distant half a mile from these breeding-places contained few or no malarial
mosquitoes. The obvious conclusion is that half a mile was beyond the normal
flight. James and Liston point out that in Mian Mir three groups of rain-pools
gave an opportunity to make fresh observations upon this question of flight. The
first group was four hundred and fifty yards distant from any house; the second
seven hundred and fifty yards distant; and the third upwards of three-quarters
of a mile. “On repeated occasions the pools of the first group were found to
contain larve within a week of a shower of rain, on three out of four occasions
the pools of the second group contained larve, but on no occasion were larve
found in the pools of the third group. These experiments appeared to show that
A. rossi, which was the species concerned, would readily fly to a breeding place a
quarter of a mile away, that it would less readily fly to a breeding-place 750 yards
away, and that it would never fly to breeding places three-quarters of a mile away.
It is obvious, however, that from none of these experiments can any knowl-
edge of the maximum flight of ‘ anopheles’ be obtained ; they prove only that
when these insects are once established in a village they naturally select the
nearer breeding places in preference to those which are further away. But in
their search for food adult ‘ anopheles’ often become attracted to villages which
have no breeding places near at hand, and recent observations have shown that
they may be abundant in a place even when there are no breeding grounds within
a very long distance. Captain James, I. M. S., in the operations at Mian Mir
already referred to, found on one occasion that numerous adult A. fuliginosus
were present in the bazaars and houses when no larve of this species were to be
found nearer than two and a quarter miles, and Dr. Christophers, during the
same operations, found that the limit of flight of A. rossi had not been reached at
three-quarters of a mile, and that although all breeding places of this species
had been obliterated up to this distance, it still appeared in increasing numbers
in the houses. The latter observer draws the following conclusions from his
experiments :—

“ (1) In every case where an abundant food supply existed, anopheles
travelled long distances (half a mile or more) to reach it, and traversed an equal
214 MOSQUITOES OF NORTH AMERICA

distance, if necessary, to lay their eggs. Where, however, a suitable breeding
place lay near at hand they did not appear to pass it over.

“ (2) The maximum distance of flight of A. rossi is not known with certainty,
but under the conditions at Mian Mir the experiments showed that they flew to
and fro a distance of more than half a mile.

“ (3) The breeding places of A. fuliginosus were in no case nearer than 1000
yards from the situation where the adults were captured.

“ (4) In the later part of the season it was difficult to understand where adult
A. culicifacies came from unless distances of half a mile or more were traversed
by this species.

“Tt is obvious that in any attempt to estimate the probable efficacy and
practicability of efforts at destruction of ‘ anopheles,’ these conclusions are ex-
tremely important.” *

The Sergents in Algeria found that the breeding-places are generally to be
found from 100 to 300 meters from infested houses, but in the case of the railway
station of Ighzer-Amokran, absolutely isolated in the Valley of the Soumman,
the station contained adult Anopheles while the nearest breeding-place was dis-
tant one kilometer. The mosquitoes found in the station were in good con-
dition. The authors do not mention the possibility that they were brought there
in the railway coaches. Further observations by these authors, at Mondovi,
showed adult Anopheles at a distance of two kilometers from breeding-places
but they ascertained that this distance was traversed by successive short flights.

It is obvious, then, that these mosquitoes do not progress by direct flight for
considerable distances but usually spread by other means. A succession of short
flights, e. g., from areas in which they are abundant, will carry them farther
than by any single direct flight. Moreover, the adults are frequently carried by
railroad trains and in other conveyances for long distances. This question we
have considered in regard to mosquitoes in general in another section.

That Anopheles perhaps may be carried, exceptionally, for considerable dis-
tances by winds is indicated by the observation of Surgeon A. C. H. Russell,
U.S. N.; he sent us a specimen of A. annulipalpis Arribalzaga, with the state-
ment that it was one of a considerable number of mosquitoes blown aboard the
U.S. 8. Newark in June, 1903, at anchor off Montevideo, more than two miles
from the shore. Carter credits Goldberger with the observation that Anopheles
albimanus appeared on board a ship, at Vera Cruz, anchored half a mile from
shore.

In a most suggestive address, delivered before the Section of Preventive
Medicine of the Congress of Arts and Sciences at the St. Louis Exposition in
1904, entitled “The Logical Basis of the Sanitary Policy of Mosquito-Reduc-
tion,” Dr. Ronald Ross considers the whole question of the spread of mosquitoes
from their breeding-places, both in communities in which anti-mosquito work is
being carried on and from outside breeding-places from which cleared areas may
be restocked. He states that the problem which governs the prophylaxis of
malaria through mosquito control may be stated in the following words: “ Sup-
pose that a mosquito is born at a given point, and that during its life it wanders

 

* A Monograph of the Anopheles Mosquitoes of India. 8S. P. z
Calcutta, 1904. PD! q James and W. Glen Liston;
216 MOSQUITOES OF NORTH AMERICA

would remain the same, even if the birth rate were to be reduced to zero. Ina
reeent experiment at Mian Mir in India the astounding result was obtained that
the mosquito-density was, if anything, increased by the anti-propagation meas-
ures—which is equivalent to saying that the population of the United States
would be increased by the abolition of the birth-rate. It is to be hoped that if
such experiments are to be repeated they will be conducted by observers who
have considered the subject. In the meantime, I for one must continue to
believe the somewhat self-evident theory that anti-propagation measures must
always reduce the mosquito density—even if the results at Havana, Ismailia,
Klang, Port Swettenham and other places are not accepted as irrefragable ex-
perimental proof of it.”

THE BEHAVIOR OF ANOPHELES TOWARDS CERTAIN COLORS.

As is pointed out with relation to the yellow-fever mosquito, persons dressed
in white are less liable to be bitten than those dressed in black. It was early
found that Anopheles, like many other mosquitoes, seeks dark places to rest
during the day and alights by preference upon dark objects. A study of the
behavior of Anopheles towards different colors has been made by Nuttall and
Shipley, which is of sufficient interest to quote in full:

“ The behavior of the insects towards various colours has not as yet received
sufficient attention. Whilst engaged with experiments upon the influence of
shade and colour we came upon a few data cited in the recent literature.

“ Austen (March 1901, p. 341) writes, ‘If the walls of the room be white-
washed, with a dark dado, it is interesting to note that the insects will always
be found upon the dark strips, and never on the white portions of the wall.’
Buchanan (April 1901), in India, notes that ‘The men who collect the living
Anopheles say that the Anopheles hide in a black coat, but avoid a white coat, so
they hang up one or two black coats in the Hospital Ward’ when they desire to
catch the imago. Neither Austen nor Buchanan say anything about the influ-
ence of colour. The first as far as we know to refer directly to the influence of
colour is Joly (May 1901, p. 259) who made observations on mosquitoes in
Madagascar. He states, without saying what genus, that mosquitoes there were
more attracted to black than to red soil, or to white sand. Persons wearing black
shoes and socks were more bitten than when these articles of apparel were white.
Brown clothes protected less than those of white or blue. He states that the
natives of Madagascar know the attraction black offers to mosquitoes and for this
reason hang up a black cloth on the rafters of the room for the insects to collect
upon. Joly observed that a yellow haired dog was very much less bitten than a
black one. For the same reason the natives are more bitten than the whites,
although they suffer less from the after effects.

“Tt seemed to us to be a matter of considerable practical utility to determine
what influence, if any, colour exerted upon a known malaria-bearing species of
mosquito. And we deem our results sufficiently striking to make it worth the
while for those who are engaged in similar studies abroad to take the matter up
systematically. Our experiments certainly indicate that Anopheles macult-
pennis is attracted by some colours and repelled by others, a matter which would
have its practical application in the choice of the colour of clothing and the in-
terior of rooms in malarious districts. We are moreover inclined to believe that
suitably constructed coloured boxes, or colour-traps, might be of practical utility
in and about houses infested with mosquitoes. By periodically closing the boxes
and sweeping out the contained insects into a receptacle, or, possibly by render-
ing the interior of the boxes sticky a considerable number of mosquitoes might
be destroyed.
COLOR PREFERENCES 217

“Our experiments were made in a large gauze tent which had been erected
within a disused photographic establishment, the one end of the tent ending
against large windows into which the sunlight poured on bright days. Large
stone basins were placed on the floor for the Anopheles to breed in, the stock
being renewed from time to time.

“Tt was noticed at the beginning that when one entered the tent in dark grey.
clothes, that the imagos frequently flew up and settled on the dark cloth, but that
they never did this when the person entering the tent was clothed in white
flannels. To test the influence of colour, a number of pasteboard boxes were
taken which measured 20 by 16 cm. and had a depth of 10 cm. The boxes were
lined with cloth, having a slightly roughened surface, to which the insects could
comfortably cling. All of the fabrics had a dull—not shiny—surface, and each
box was lined with a cloth of different colour. The boxes were placed in rows
upon the floor and upon each other in tiers, the order being changed each day
after the observations had been made. The interior of the boxes was moderately
illuminated by light reflected from the surface of the white tent. On 17 days
during a month beginning with the middle of June, we counted the number of
flies which had accumulated in the boxes. Counts were actually made on 17
sunny and cloudy days, and with the following result :

Number of A. maculipennis
Colour of Box counted in each box
during 17 days.

Navy DIME asdi ed besa eis HOS Cae aue eee eee ea
ADK. TOC sacetece sg stsgee-ack steed Ges has due oe ahteate re Miaona nena aca sree
Brown: (Reddish): a6 psiiaciewaais view mieeiee eae eos-aaiee ces
SCARIOU: fis 5 cuenslg/ aus tts oy aravenaisan eo ohisede Ga weamnee aie ce beranasg bee ac
Black esac ee.¥8 se Roe O04 SES es SEG Bee Re Ke oe We. seein re a
DIGG BYOY 2604 cae 29 dee 4 64 ee oso Ae CeO k wR ew ORWS ES
Dark green (olive)
WH OTE sis onestewtedieiyes
Leaf green ..........
BUG. wes saws ys enw see ae
Se) ee ee Tree eee eee ee
PAlO: BTCOM: i655 S359. h6d ays Gong Brae POS aio TASS A MR Sa 8
Light blue (forget-me-not) ........ 0. e cece cece ee eee 3
OCHIE: -eeiaswrs Section Sala Sea i giae ea O eT eake ts WOM G ase 2
Wit wick cee sad ides Bae nad Gane eM A OME eee Ree AES 2
OLANLC. Scecod dieis Sa SMS Eee SOS AAT Es OWES 4 Gow ples 1
VOMOW. ob as nd 6 sieskd ant a dane ea ones eRe eee a eS 0

 

“ We see from the above table that dark blue was most attractive, the other
colours being less and less attractive in the order of numbers given. A marked
fall in the number of insects resting in the boxes begins with the ‘ pearl grey’
box. Pale green, light blue, ochre, orange, and yellow, especially the last two
colours seemed to repel the insects. The karki-coloured uniform at present in
vogue should offer advantages besides invisibility to human foes! These obser-
vations on colour were described by one of us in a short note which appeared in
the British Medical Journal (14 Sept., 1901).

“Mr. J. Cropper, of Mount Ballan, Chepstow, who read the above note wrote
to us (17 Sept., 1901) : ‘ Seeing your article on Colour Selection by Anopheles
reminds me that I found the dark navy-blue lining of my tent this summer (in
Palestine) extremely attractive to mosquitoes, almost entirely Anopheles—and
when the sun got hot I always noticed an increase in their numbers, presumably
as they came from the herbage and trees near by. No one ever slept in the tent,
and I never found Anopheles bite in the day time.’
218 MOSQUITOES OF NORTH AMERICA

“ Moreover Dr. H. E. Durham has since informed us that whilst he was study-
ing yellow fever at Para, Brazil, he was much less bitten about the feet than
was his late companion Dr. Myers. Dr. Durham wore ochre coloured socks, Dr.
Myers black ones.”

Further experiments upon color preferences have been made by Jordan and
Hefferan (“Observations on the Bionomics of Anopheles,” Journal of In-
fectious Diseases, vol. ii, No. 1, January 12,1905). Their results are as follows:

“ Experiments were made to determine the color preference of adult A. puncti-
pennis. The conditions of the experiment were substantially the same as those
in a similar series of observations made by Nuttall upon A. maculipennis. The
mosquitoes were confined under a large hood with glass sides and front. Boxes
covered with different colored cloths of similar texture were placed under the
hood, and every day at a fixed hour during a week the number of mosquitoes that
had settled on each color was counted. The position of the boxes was changed
every day after counting to eliminate possible influences of light and shade and
other factors. The results were as follows:

Number of Mosquitoes. On
Dark red
Dark blue
Black
Dark pink
Dark green
Lavender

... Light blue

. Pale green

. Light pink
... Yellow

 

“These results with A. punctipennis are very much like those obtained by
Nuttall with A. maculipennis, dark red and dark blue proving the most at-
tractive in both cases.”

BREEDING-PLACES OF ANOPHELES.

Some observations bearing on this question will be found under the genus
Anopheles in the systematic portion of this work. In the early investigations
in America the larvee were found in more or less permanent pools of water in
the bed of an old canal, in the side pools of spring-fed woodland streams, in the
side pools or shallows of field springs, or in artificial excavations filled with sur-
face water. In such places, especially when supplied with a certain amount of
green scum, the little larvee were often found resting at the surface of the water,
occasionally darting from one spot to another. They were also found in water
contained in barrels and troughs, in fountain basins, but comparatively rarely
found in the same water with the larve of Culex. Austen, in the report of the
proceedings of the expedition for the study of the causes of malaria at Sierra
Leone, states that on August 26, 1899, Doctor Prout and Doctor Berkeley found
Anopheles larve mingled with those of Culex in a tub of water in a yard at the
Sanitary Office. Aside from this and one other instance, Anopheles were always
found breeding in roadside puddles and ditches. Nuttall, Cobbet, and Strange-
ways-Pigg, in England, found Anopheles larve nine times with Culex in ponds,
and also took them with Culea in ditches in which the water scarcely flowed, in
LARVAL HABITATS 219

water-logged boats, and in stone troughs, and in fact found them fourteen times
altogether with Culea and ten times with fish. Grassi and Ficalbi state that
Anopheles maculipennis is most frequently found in flat land in Italy, the larve
requiring clear water rich in vegetable food. Austen found in Freetown that
Anopheles larve occurred in stagnant puddles varying from a foot to several feet
at the sides of the streets, but many were met in the still water in little bays at
the side of slowly running shallow ditches. Whether the water was clear or
muddy seemed to make no difference, but green alge were nearly always present,
and in some puddles tadpoles were numerous. Veazie, of New Orleans, finds
Anopheles larve in the ponds out in the suburbs and in the swamps back of the
city. Colonel Gorgas, in the Havana campaign, found that the most efficient
work was done by his malaria brigade along the small streams, the irrigated
gardens and similar places in the suburbs. Anopheles bred principally in the
pools and puddles well protected with grass, and were abundantly found in the
small holes made by the footsteps of cattle and horses, which observation has
been frequently repeated elsewhere. F.C. Pratt, of the Bureau of Entomology,
has found them breeding in temporary standing water between rows of corn in
lowlands in North Carolina.

As a matter of fact Anopheles larve may breed in almost any standing water.
Smith, in answer to his own question “where does Anopheles breed?” says
“ Everywhere.” He has found the larve in trap-pails in his back yard, and
states that he has found no pool so insignificant and no stream so rapid but that
somewhere in it Anopheles can breed. He has found the larve of A. quadri-
maculatus on the salt marsh, and he has taken a larva of A. punctipennis in a
stream that was so foul that it resembled an open sewer. He says:

“ Small creeks through meadow land, the ditches and gutters or drains along
railroad and other embankments, and the shallow overgrown edges of ponds or
swamp areas are favorite breeding places. Pools containing grassy or other
vegetation are nearly always infested, and ponds with lily pads, dock, saggittaria
and other plants of a similar character, are danger points. The larve need only
amere film of water, and this being found over a leaf or at a grassy edge, protects

them from the usual natural enemies. . . . no other mosquito has as wide a
range of breeding places as have the species of Anopheles.”

James and Liston, in their admirable study of Anopheles in India, state also
that it is almost impossible to find a collection of water in which Anopheles may
not occasionally be found. Unless every collection of water is systematically
searched, important breeding-places may be overlooked. It is the opinion of
these writers that each species has a particular kind of breeding-ground that it
prefers above any other, a fact which has been noted by other observers in other
parts of the world. Calodiazesis barberi, for example, in the United States, and
Anopheles eiseni in Central America, breed in collections of water in tree-holes,
frequently far away from human habitations. James and Liston point out that
at Jalpaiguri two species of Anopheles were common; A. rossi bred in the small
shallow, muddy puddles and pools near and among the native huts; A. nigerri-
mus bred at some distance from the village in the deep natural pools of a swampy
marsh. Neither of these larvee was found in the breeding-places of the other.
220 MOSQUITOES OF NORTH AMERICA

This principle, they state, extends to all the species of Indian Anopheles, and
they point out an excellent example in three species found in an isolated bazaar
at Mian Mir. Here there were three species, A. cwlicifacies, A. fuliginosus, and
A. rossi. “This bazaar is surrounded by an irrigation channel about four feet
wide and three feet deep. At the upper end of this water-course and about ten
yards from it are a number of broad shallow muddy pools. At the lower end
of the water-course and about thirty yards from the bazaar is a swampy piece
of land covered with thick trees and shrubs, and containing a number of deep
clear pools in which water plants and weed had grown.” The adults of all three
species were present in the houses of the bazaar, but in the irrigation channel
only the larve of A. culicifacies were found, while in the shallow, muddy pools
only the larve of A. rossi, and in the deep, clear pools under the trees only the
larve of A. fuliginosus. Each of these species, therefore, had selected a par-
ticular kind of breeding-place. In another part of Mian Mir still another species
of Anopheles was found breeding in the earthenware vessels of water. This
species was A. stephensi, and it was not found breeding elsewhere.

The Sergents in Algeria studied with great care the subject of breeding-places,
but there is little to add to what is given above. They call attention to the fact
that in this country of the Arabs the spring, without which a community of
people can not exist, is at the same time the indirect cause of the unhealthiness
of the region in serving as a breeding-place of Anopheles.

We have mentioned the breeding of two species in collections of water in tree-
holes, frequently far away from human habitations, but have not mentioned in
this connection the accumulations of rain-water at the bases of the leaves of
certain bromeliaceous plants in the tropics. A number of species of mosquitoes
breed in such accumulations, and among them there is at least one Anopheles.
In a suggestive paper entitled “ Waldmosquitos und Waldmalaria,” Dr. A.
Lutz, formerly Director of the Bacteriological Institute of Sao Paulo, gives
an account of the possible influence of such an Anopheles upon the con-
struction of a railway. This railway was being built from Sao Paulo to Santos
in Brazil, through an elevated well-wooded and wild region in which there were
many mountain streams. Stagnant pools did not occur. During the con-
struction of an adjoining railway intermittent fever had prevailed among the
laborers, but after the line was completed it disappeared. During the construc-
tion of the new line many laborers were lodged in clearings in the forest along
the line. Intermittent fever soon appeared, especially in the lower portions, but
in the hot seasons rising to the top of the mountain. The fever was mild, but
relapses were frequent. Doctor Lutz personally investigated the conditions, and
himself spent a few nights on the spot. The first night he found an Anopheles
mosquito, afterwards described by Theobald as Anopheles lutzii.* He found
it abundantly in the mountain forest near the coast, but never far inland. He
made a careful search for the breeding-places, and by a process of elimination
finally focused his attention upon the epiphytic Bromeliaces. These were very

 

* A species was previously given the same specifi ‘
changed to A. crueit by Dyar & Knab. P SARE DY Des Cella, the present obe.-Was
CHOICE OF BREEDING PLACES 221

difficult of examination, since the plants for the most part grew upon the forest
trees thirty feet above the ground. Those that had fallen with the trees had lost
their water. Later, however, many plants were found in places which could be
reached, and in the water accumulations of their leaves were found breeding a
number of species of mosquitoes, and among these the larve of Anopheles cruzit.
He considers the species to be a typical forest insect breeding only in such places,
and that it is responsible for the malarial attack of a mild type from which the
railway constructionists had suffered. The genera of Bromeliacee most com-
monly met with are said to be Bresia, Nidularium, Billbergia, Aichmea and
Bromelia. In the water in these plants, he found bits of vegetation and a humus
formed from them, and living in it small crustaceans, tadpoles, larve of Culi-
cide and Chironomide. Among the other mosquitoes inhabiting this bromelia-
water he found Megarhinus violaceus which was feeding upon the other culicid
larve. The relation of Anopheles cruzii to this outbreak of malaria was not
positively established.

On the supposition that Anopheles punctipennis is not a carrier of malaria, the
control of malaria in certain regions of the United States, through the destruc-
tion of the Anopheles larve or breeding-places, may be simplified if a difference
in the character of the breeding-places of A. punctipennis and A. quadrimacu-
latus (the only other common inland species in the more northern United
States) can be ascertained. This consideration led Jordan and Hefferan (Joc.
cit.) to carry out the following observations :

“In the present instance it was found that the favorite breeding-places of A.
maculipennis * and A. punctipennis, although close together, were of quite dif-
ferent character, as shown by the following facts relating to the distribution in
Western Michigan.

“ Dipping for mosquito larve was carried out in the springs and spring-fed
pools of the northern ravines, along the river shore, in the bayou, and in rain-
water barrels of the village. In all of these places, with the exception of the
bayou, Anopheles larve were found in abundance at some time during three
consecutive summers. The distribution was more extensive in 1902, merely
because the early part of the summer was wet, and water stood longer in the
springs and ravines. In 1903 the early part of the summer was dry, so that by
the middle of August two springs and the river shore only were left as breeding-
places in the immediate vicinity of the village. In the river the larve of A.
maculipennis * are found regularly at certain places along the north shore,
where abundant food and quiet are ensured by the wreckage and masses of river
weed which lie a few inches below the surface of the water. Here, with the river
running almost due west, the larve are exposed to direct sunlight. They were
not found along the more shaded south shore. A curious instance of choice of
breeding-places occurred in the summer of 1904. A small stream running to
the river had, during the spring, a course of a mile or so down the ravine, but
by August 1 it had dried to a few pools of the following character: (a) River
inlet, 40 feet long and 7 feet wide, shaded by willows, bottom sand and mud,
no larve; (b) Ten feet above this inlet a pool 40 feet by 4 feet in area, some 15
inches deep, entirely without shade or vegetation, no larve ; (c) Only three feet
from this second pool another pool of clear water, 5 feet by 3 feet in size, and 6

 

* = Anopheles quadrimaculatus of this work.
222 MOSQUITOES OF NORTH AMERICA

inches deep, shaded in the morning. Duckweed abounds here, and a quantity of
green alge cover the sticks and stone of the bottom; the pool swarms with
Culex and Anopheles punctipennis larve; (d) Thirty-five feet above (c) is an
‘iron’ pool with a deposit of iron; it is about 9 feet by 9 feet, 10 inches deep,
partly shaded by bushes and a huge log. It contains no vegetation and no larve.
Of these four pools the smallest one, in the center of the row, is the only one con-
taining Anopheles larve. These larve are exclusively those of A. punctipenns,
while in the river only a few feet from here, A. maculipennis is abundant.

“ Another noticeable feature of the distribution is the entire absence of all
mosquito larvee from the bayou, although the water is currentless, the vegetation
abundant, and the light and shade favorable. It is probable that the duckweed
and lily pads cover the surface too closely in the shallow water near the shore.
As pool (c) above described became choked with duckweed later in the season,
the larve disappeared.

“The following table shows the undoubted selection of different breeding-
places by A. maculipennis and A. punctipennis:

ANOPHELES BRED FROM LaRvZ AND Pups,

 

 

 

A. maculipennis. A. punctipennis.
Males. Females. Males. Females.
Collected from spring-fed pools........-. 0 0 30 35
Collected from river......... ccc cece eee 46 47 1 4

 

 

 

“ The fact that the breeding-places are only a few feet apart renders especially
remarkable the specific preference displayed. The predominance of A. puncti-
pennis in the other two regions that were examined is in accord with the obser-
vations in Michigan. A. punctipennis shows a predilection for spring-fed pools,
and, in localities where these abound, is the chief species. Hirschberg and
Dohme observed a rather definite geographical distribution of the two species
in the vicinity of Baltimore, A. maculipennis being found on low ground in or
near large bodies of water, while A. punctipennis was found in small, clear
streams or springs on higher ground.”

Smith in New Jersey says of A. punctipennis, “ On the whole it breeds most
abundantly in clean water along the edges of ponds or swamp areas or in the
eddies of shallow streams.” Concerning A. quadrimaculatus, he says, “The
breeding places are similar, but this form also occurs in brackish water on the
salt marshes, hence has a somewhat wider range and adds the positive danger
of disease to the disadvantages of an undrained marsh.”

J. K. Thibault, Jr. (in litt.) states that at Little Rock, Arkansas, Anopheles
punctipennis is the most abundant species in the city and that it is scarce in the
country; but that A. quadrimaculatus is the more abundant mosquito in the
river-bottoms but is scarce in the city.

An interesting point has been brought out by Dutton in his report of the
malaria expedition to the Gambia (Liverpool School of Tropical Medicine—
Memoir X), to the effect that the number of mosquito breeding-places present
in compounds was found to vary with the social position of the occupier, and in
this statement he includes Anopheles mosquitoes. The following is taken from
his report:
ASSOCIATION WITH MAN 223

“Tn small compounds of the poorer natives, where one or two huts were
present, no breeding-places were found. These natives had no discarded bottles,
etc., in which water could collect, nor were wells or tubs or any article for the
storage of water present, sufficient water for the day being drawn from one of
the public wells. These compounds were exceedingly clean and tidy, and no
mosquitoes were found breeding in them. Excepting these, breeding-places
were found and increased in extent and number in proportion to the wealth and
position of the occupier of the compound, reaching a maximum on the premises
of the larger traders (natives and white), where innumerable facilities for the
development of mosquitoes were afforded. These breeding places included all
those domestic articles which are capable of containing a small quantity of
water after showers lasting over a week without being dried up, or are not dried
up between the frequent showers in the wet season. Such articles found were
broken bottles, either stuck on a wall or scattered over the compounds, iron pots,
old calabashes, tin-lined packing cases, cocoanut husks, fowl troughs, and old
tins of all sorts. There was found an extraordinary amount of such-like rubbish
in some of the factory compounds, the more specialized breeding-places included
tubs, used for the storage of rain-water or as wash tubs for bottles, or in which
water was placed for the preservation of the tub. Large barrels in which fibres
were soaked, garden tubs in which water was stored for gardening purposes,
old iron boilers for the collection of rain-water, improperly covered rain-tanks
formed other breeding-places. In some of the factories a small gutter six inches
across by four feet deep is let into the cemented floor of the yard around the
ground-nut store house. This gutter is kept full of water to prevent the en-
trance of the ground-nut insect into the store. These gutters swarmed with
mosquito larve. In some yards a small channel runs down the centre to drain
off rain water, and is generally covered over with a board. It was found that
some of these had become clogged up at intervals with sand and rubbish, so that
small pools of water collected along their course; these pools acted as breeding-
places for mosquitoes. An account of an examination of one of the larger Euro-
pean factories will illustrate to what extent mosquitoes are bred by the white
man in the tropics on his own premises. In the factory yard were six barrels
containing water, in some the water was very foul; in the garden were seventeen
tubs containing water for gardening purposes, and besides this number of tubs
there were eight wells, all uncovered. In all these articles mosquito larve were
present ; in the barrels in the yard the water swarmed with Culex and Stegomyia
larvee, and in the wells and tubs in the garden the larvae of Anopheles and Culex
were found in all of them in good numbers. Besides these breeding-places there
were many domestic articles scattered about in odd corners of the yard, which in
the wet season would also have acted as breeding-places.

“ Tt was observed that larve of A. costalis were frequently found in rain-tubs
and smaller articles containing water. Though many of these larve may have
been originally transferred to some of these articles along with the water drawn
from the well, yet the occurrence of batches of larve of the same age and in fair
numbers would tend to show that this species of mosquito avails itself of these
small collections of water in which to breed.

Stegomyia fasciata, in tubs and old bottles, ete.

Culex fatigans, « “and especially when the water was foul
A. costalis, tubs and barrels

Culex duttoni

Culex hirsutipalpts

Stegomyia pagens (rare), in ground-nut gutters.

“ The wash-tubs, garden-tubs, wells, and rain-barrels occurring in compounds
form the chief source of mosquito in Bathurst for at least six months of the dry
224. MOSQUITOES OF NORTH AMERICA

season, when all other breeding-places, artificial and natural, have ceased to
exist.”

ANOPHELES BREEDING IN SEA-WATER.

We have mentioned above a statement by Smith that Anopheles has been
found in the salt marshes, and this observation has been repeated by others.
Anopheles have been found breeding in salt or brackish water in many parts of
the world; in every case the habit has been found restricted to certain species.
An article was published by Dr. W. T. de Vogel, health officer of Samarang,
Java, in the Atti della Societa per gli Studi della Malaria for 1907, bearing
upon upon this question, and his observations are so important that we devote
considerable attention to them. De Vogel found that the investigations of
several Italian workers have negatived the idea that Anopheles can multiply in
pure sea-water and that they have shown that the maximum proportion of
sodium chloride in the water which Anopheles larve can stand is 1.87 per cent
according to Perrone, and 1.75 per cent according to Vivante. De Vogel,
having made some elaborate studies in regard to malaria at Samarang, found
as early as 1902 that Anopheles was breeding in a certain pool containing 2.8
per cent of chloride of sodium. Later he verified these results in several in-
teresting cases. One of these was the island of Onrust, a small coral island
situated two thousand meters from the mainland, and which contains no fresh
water whatever. The distance from the mainland is such that even if Anopheles
were brought from the mainland by winds they would not be numerous enough
to cause trouble. Nevertheless a marine station established on the island had
to be abandoned on account of the ravages of malaria among the workmen and
Dr. de Vogel believed that this was due to Anopheles breeding in the sea-water
upon the island itself.

De Vogel studied also the conditions in the Karimon Islands, a little archi-
pelago in the Java Sea, sixty-five kilometers from the coast. The first colonists
in this archipelago were convicts and were sent there to cut down the forests of
rhizopores. There were no buildings, and the convicts were forced to sleep on
the earth. The mortality was between two and three thousand in two years.
Later one of the officers named von Michalofski—a plain man but full of good
sense—succeeded in putting a stop to the excessive mortality by drying the sea-
water pools, removing a part of the forest, and raising the ground on which the
men slept. The success which followed these measures leads de Vogel to sup-
pose that the mortality had been caused by malaria, and this supposition is all
the more probable since, as he himself has verified, malaria is today rife among
the population of the islands.

There is on the island of Grand Marimon only a single permanent source of
fresh water which has only one restricted outlet. During the dry season there is
no mingling of fresh water with sea-water, so there exist during that season
many pools of dead sea-water peopled with Anopheles larve ; these pools contain
not less than three per cent of sodium chloride and must then be considered as
concentrated sea-water.
SEA-WATER POOLS AND MALARIA 225

Continuing his researches at Samarang, de Vogel found other pools of water
inhabited by Anopheles larve, in proximity to the sea. One of these places had
a surface of 20 to 30 square meters and a depth of from 10 to 30 centimeters.
It was connected with a pool of sea-water by a bamboo-pipe crossing the dike.
The pool is thus invaded by seaweeds, but the fish can not enter. This place
swarms with Anopheles larve, while Culex larve are not found there. In this
pool the percentage of sodium chloride is about 2.88, while in the water of the
neighboring swamps it varies between 2.44 and 2.76.

Other instances of the occurrence of Anopheles larve in concentrated sea-
water are given with careful descriptions and the author finally draws the fol-
lowing conclusions :

“1. There are species of Anopheles which can live very well in sea-water.

“2. These mosquitoes lay eggs which develop even in sea-water which has been
evaporated to half its original quantity.

“3. These larve in the gradually evaporating pools of sea-water can stand an
evaporation of the water to one-third of its bulk, but do not appear to transform
to adults if the concentration be greater than this.

“4. The larve coming from eggs laid in sea-water of high concentration can
accomplish their entire metamorphoses in almost the normal time. This is true
even when the water has such concentration that the development of larve
originally hatching in unconcentrated sea-water would be retarded by this salt
water.

In the opinion of de Vogel the bad reputation which the coral islands of the
East Indies have, is explained by his observations, since so many cases of malaria
are observed along the coast during the dry season when all the rivers and fresh-
water streams are dried up. Villages near the sea, in the middle of tidal pools,
have had during a period of ten years an average mortality of from 1 to 4 per
cent each year. In villages further away from the sea, where the ponds have
been abandoned or neglected and the sea-water, therefore, is isolated, there is a
mortality which varies from 8 to 10 per cent each year. The pools in these
regions during the dry season have a proportion of sea salt equal to that of the
ocean. In this dry season the death rate is greatest, and this is exclusively due
to the Anopheles breeding in the sea-water ponds.

“ The great mortality is surely due to malaria, since almost without exception
the cases of pernicious malaria or hemoglobinuria which are treated at Sama-
rang come from the south border of tidal pools. A quarter of Samarang called
Zeestrand was inhabited by well-to-do citizens of the city who had good health,
although surrounded by pools. Then, when on account of the banking of the
coast, these pools were left further from the sea, the locality became unhealthy
and the inhabitants were forced to quit the quarter because the death rate from
malaria reached terrible proportions. The empty houses of this quarter still
bear witness to past grandeur. The mortality of the indigenous population
which still remains there has been on the average during the last ten years 9.7
per cent per year.”

The difference in the malarial rate is not due to any change in the character
of the water itself. When the pools were tide-water pools fish and other life
had access and kept the mosquito larve in check, while in the now isolated pools
the Anopheles larve can develop unhindered.
226 MOSQUITOES OF NORTH AMERICA

De Vogel’s paper has been criticised in that he produced no direct proof that
the Anopheles breeding in the sea-water pools are the ones responsible for the
malaria attributed to them. Furthermore, the species indicated, Anopheles
rossii, has been shown repeatedly to be incapable of transmitting malaria, the
parasites failing to develop within it. But recent investigations by Major Car-
ruthers in the Andaman Islands confirm de Vogel’s conclusion that the Anoph-
eles breeding in the sea-water pools are responsible for malaria. The species,
however, is not Anopheles rossii, but A. ludlowti which greatly resembles it. The
question is clearly presented in a recent address by Surgeon-General C. P. Lukis,
Acting Sanitary Commissioner with the government of India, at Bombay, before
the General Malaria Committee. Speaking of the results of Major Carruthers,
he says:

“The first thing that struck him was the remarkable fact that a large num-
ber of villages were quite free from malaria, in spite of the fact that many of
them were surrounded by riceland, swamp or jungle, whereas others showed a
considerable amount of malaria, the spleen rate varying from 25 per cent. to
50 per cent. Eventually it was noted that what determined the healthiness or
unhealthiness of a village was its proximity to the sea. Villages near the sea
were invariably malarious ; those remote from the sea healthy. Even a distance
of half a mile from the sea was sufficient to insure the endemic index being 0
per cent. This distribution of malaria was shown by actual measurement to be
exactly coincident with the occurrence of a particular species of anopheles,
namely Pseudomyzomyia Ludlowu, which appeared to breed chiefly in salt
swamps and brackish water, and which was undoubtedly the chief malaria carrier
in the Port Blair Settlement.

“ Now so closely does this mosquito, on casual examination, resemble M. Rossii
that, with reference to these two species, Professor Eysel has remarked upon
the folly of too nice distinctions in regard to the species of anopheles and the
transmission of malaria. Yet the existence of two distinct, though closely re-
lated species of anopheles is the explanation why, in the Andamans, the prox-
imity to ricelands and swamps is innocuous, provided that these are at a dis-
tance from the sea.”

According to these observations, the proposed destruction of Anopheles by the
introduction of sea-water does not seem to be rational, at least with certain
species. At all events the specific identity of the Anopheles concerned must be
taken into account. It appears certain that while some species may breed either
in fresh or brackish water others occur exclusively in saline water. In certain
regions good tidal ponds prevent the breeding of Anopheles to some extent and
may in that affect the malarial rate. In others, where the species which breed
in salt or sea-water are present, and there are isolated stagnant pools, as has
been observed at Samarang and in the Andamans, such measures would have
little effect unless fish were admitted with the sea-water.

According to C. 8. Banks Anopheles ludlowii in the Philippines breeds in
both salt and fresh water. Banks gives an account of his observations in the
Philippine Journal of Science. In an earlier publication he had shown that
this species breeds in sea-water and claimed that it is a transmitter of malaria.
In his first paper he stated that this mosquito had never been found in the
Philippine Islands breeding in fresh water. Later, however, he took a trip to
SEA-WATER BREEDERS 227

the mountain province of Lepanto-Bontoe for the purpose of investigating an
epidemic of malarial fever. He fully expected to find that the responsible mos-
quito would prove to be a different species, but during his first stay in the
province he found what he considered Anopheles ludlowii in the dwellings,
while later he also found their larve breeding in greatest abundance in the
rivers and smaller streams of the vicinity. He spent over two weeks in the
neighborhood, and made a search for larve which included the rice fields
(flooded at that time of the year), the water tanks near the buildings, and all
probable breeding-places. He states that he found no other species of Anopheles.

It is evident that the observations of Mr. Banks are faulty and inconclusive.
From the observations previously cited it is to be seen that Anopheles ludlowu
breeds exclusively in saline water. The species which he found at Lepanto-
Bontoe and so identified was in all probability Anopheles rossi. However, as
this latter species is known to be ineffective as a malaria transmitter, and as other
species of Anopheles have a wide distribution in the Philippines, it is obvious
that his methods were inadequate. Moreover, it appears that many of the de-
terminations were made from larve and were therefore unreliable, as the
Anopheles larve are very similar and much more difficult to distinguish than
the adults.

Some interesting observations on the existence of Anopheles larve in sea-water
were made by Dutton in his malaria expedition to the Gambia in 1902 (Liver-
pool School of Tropical Medicine, Memoir X). The following account is taken
from pages 29 to 30 of his report:

“A garden tub in which mosquitoes had been breeding was emptied and
cleaned, and sea water, taken as the tide was coming in, placed in it, the other
tubs in the garden being covered with mosquito netting. In four days afterwards
a batch of small Anopheles larve was discovered in the water, which subsequently
hatched out into adult mosquitoes (A. costalis) seven days later. This experi-
ment was repeated with the result that first eggs of Anopheles and also Culex
appeared in one or two days after the tidal water had been placed in the tub,
and subsequently adult insects hatched out from them. From these experiments
it would thus appear that certain kinds of mosquitoes can breed in tidal water if
it is not disturbed, and subsequently when the dry season had fully set in, I
found larve in suitable tidal pools, namely, as J have already mentioned, in the
drains near the sluice gates in which tidal water had soaked in through the
gates. In this water, which contained 1038.5 parts of chlorine per 100,000 parts,
I found a few larve of A. costalis and large numbers of Culex halassios. On
another occasion, in December, I found these mosquitoes breeding in a small
hole from which shells had been taken, close to the edge of the water at the
mouth of Oyster Creek. The Culex were subsequently hatched out from this
tidal water, but the Anopheles larvee were nearly all infested with a fungus (not
identified) which gave them a woolly appearance, and I failed to hatch out any
of them. I observed A. costalis breeding in a similar salt-water pool during a
period in which neap tides occurred. The tidal water in an arm of the central
channel in Box Bar, running from the sluice gates to the cemetery, had become
converted into a series of small pools by partial evaporation of the water, though
at every tide some water leaks through the sluice gates into this channel, but
during this period it was not sufficient to replenish this small branch drain.
Anopheles larve were found in great numbers in these pools. It is interesting

16
228 MOSQUITOES OF NORTH AMERICA

to note, also, that at this time two of the largest pools which were situated
close by, and have been described as swarming with mosquito larve, had been
filled in with sand. Samples of water taken from various parts of the town were
examined for the amount of chlorine present in them, the result is given in the
following table.

 

Chlorine expressed
Chlorine per
“Sample of water. as percentage
100,000 parts. of NaCl.

 

1. Public well, New Town, no mosquitoes present

INC WAtEE. e605 6 ease eae RESTATE ie ieee 161.2 265
2. Public well, Lancaster Street, water rather foul,

Anopheles larve present in numbers .... ... 1148.0 1.89
8. Public well in Clifton Road, behind Hospital, no

larvae present... ... 6. ce cece ete eee teen ens 186.0 0.3

4. Water (tidal) found in drain near sluice gate,
Blucher Street, A. costalis and large quantities

 

of @. halassios present, .......6- eee teen ees 1088.5 1.71
5. Small well in private garden, Culex present, few

CNG chen Kalewwgee ced wo URE ONO eet eeaee 27.9 0.04
6. Small well in native compound, Victoria Street,

Culex larvee present ......... es cece cece eee 1145.0 1.88”

 

 

To refer briefly to the other records of Anopheles breeding in sea-water, this
habit was probably first mentioned by Grassi, who observed it at Metaponto,
Italy. Nuttall, Cobbet and Strangeways-Pigg captured larve six times in
brackish water. A. Clerc has experimented with larve of Anopheles maculi-
pennis; he found that larve placed in water with 44-46 grammes of salt to the
liter would die if very young, but the older larva developed and produced imagos.
Christophers and Stephens found Anopheles larve to occur at Accra in brackish
pools 0.6 per cent salt. Foley and Yvernault found that in Algeria Anopheles
‘chaudoyet breeds in saline water containing 40 grammes of salt to the liter.
Chatterjee found larve of what he called Anopheles rossi, but which it would
now seem were A. Judlowi#i, in brackish water in India. Gholap found another
Indian species, Anopheles stephensi, breeding in salt water.

In America several species of Anopheles have been found to breed in brackish
water, but none of them exclusively so. Chapin, in Rhode Island, found Anoph-
eles larve living in brackish water on the coast. Anopheles crucians has been
found to breed in brackish water in New Jersey and Louisiana, and we have
already mentioned that Smith has found larve of A. quadrimaculatus in New
Jersey under similar circumstances. It is worthy of note in this connection that
Anopheles crucians seems to thrive best in the vicinity of tide water and to occur
much less abundantly inland.

Anopheles albimanus, of tropical America, according to information furnished
by Mr. A. H. Jennings of the Isthmian Canal Commission, breeds in strongly
brackish water as well as in fresh water. The same may be said of Anopheles
tarsimaculata, a geographic form of A. albimanus, and of A. argyritarsis. This
last statement is made on the authority of Peryassi. The Brazilian observers
made a series of laboratory experiments to determine the degree of salinity in
which these larvae could develop to imagos. They found that in slightly brackish
MODE OF FEEDING 229

water imagos were produced in a normal manner. In a mixture of 19 per cent
of sea-water with fresh water only a very small proportion of larve transformed
to imagos. Beyond this the larve failed to pupate; with 20 per cent sea-water
some of the larve survived three days ; with 30 per cent all died after one day.

HABITS AND FOOD OF THE LARV/E OF ANOPHELES.

The early stages of Anopheles were first studied in the United States by the
senior author in 1899. Eggs were secured from gravid females captured, and
the full life round was studied and first described in an article entitled “The
Differences between Malarial and Non-malarial Mosquitoes” in the Scientific
American for July 7, 1900, pages 8-9, and subsequently in a bulletin of the
U. 8. Department of Agriculture. About the same time he found larve of
Anopheles along the borders of a small stream in Roland Park near Baltimore,
Maryland, and was under the impression at the time that he was the first Ameri-
can entomologist to find this peculiar larva; but it seems that 25 years earlier the
larva had been found by Dr. Charles Sedgwick Minot, of Boston, and the adult
was reared at that time. The identity of the insect was not suspected, however,
but Doctor Minot had preserved the early notes, and after the appearance of
Bulletin 25 recognized the larva and published an account of his early observa-
tions in the Journal of the Boston Society of Medical Sciences, volume v,
January, 1901.

The first reference to the early stages of Anopheles to be found in the litera-
ture is a paper by Joblot, published in Paris in 1754 under the title (translated)
“ Description of a New Fish which I found in the Water of the Basin of St.
Magloire of the Fauxbourg Saint-Jaques at Paris, which can be called an Aquatic
Caterpillar.” He figures the larva, which is recognizable as that of Anopheles.
Brauer gave a good figure and description of the larva as that of Dixa in 1883.
F. Meinert next published accurate descriptions and figures of the larvee of two
European species in 1886. Other descriptions and figures were published by
Ficalbi in 1899 and Giles in 1900. The different stages were described and
figured in 1900 by Grassi.

The eggs, elsewhere described, are laid loosely upon the surface of the water,
each egg lying upon its side, from forty to a hundred of them as a rule floating
rather close to one another.

The larva, also described in the systematic consideration of the genus, is
markedly peculiar in its structure. It habitually remains at the surface of the
water. It is without the breathing-tube so characteristic of the other mosquito
larve, and its body is held practically parallel with the surface and immediately
below the surface film, while portions of its head as well as its breathing ap-
paratus are practically out of the water. In addition to the protruding head and
the mechanism surrounding the spiracles the larva is held at the surface by
means of rosettes of scales, the so-called “stellate hairs,’ upon some of the
abdominal segments. These protruding parts interlock with the surface film,
hence the larva can not descend without an effort and it only does so to escape
danger. The larva’s head rotates upon its neck in a most extraordinary way, so
230 MOSQUITOES OF NORTH AMERICA

that the larva can turn it completely around with the utmost ease; it feeds
habitually with the under side of the head towards the surface of the water
whereas the upper side of the body is towards the surface. In this customary
feeding position, the mouth-parts are working violently ; the long fringes of the
mouth-parts cause a constant current towards the mouth and the particles float-
ing on the surface of the water in the neighborhood thus gradually converge to
the mouth opening and enter the alimentary canal. The spores of alge, bits of
dust, minute sticks, bits of cast larval skins, everything in fact which floats,
follow this course, and, watching the larva under the microscope, they can plainly
be seen to pass through the head into the thorax until they are obscured by the
opaque color of the larva’s back. This is the common method of feeding when
full grown; however, the larva will descend in the shallow water and mouth
over the slime on pebbles at the bottom. Occasionally a fragment, too large to be
swallowed with ease, clogs the mouth. Sometimes it enters the mouth and sticks.
In such cases the head of the larva revolves with lightning-like rapidity until
the top of the head is upwards, and the fragment is nearly always disgorged,
although sometimes it is swallowed with an evident effort.

As indicated, the larva feeds upon everything that floats. It is especially often
found in stagnant water on which there is more or less of an algal scum; there-
fore a very frequent food consists of algal spores, and the color of the larva is
influenced more or less by the character of the food, green alge making it green.
Daniels, in his African investigations found that the contents of the intestines
of the larve are mainly vegetable matter, in some cases entirely so. “ Occasion-
ally limbs of minute insects or crustaceans are found as well as scales of mos-
quitoes or other insects. On watching them feeding, it is seen that all minute
particles are drawn to the mouth, but many of them are rejected. This rejection
is somewhat arbitrary, as a particle at first rejected is often subsequently swal-
lowed. Amongst the bodies seen to be swallowed I have seen living minute crus-
taceans and young larve, both of anopheles and culices, but, as a rule, living
animal bodies either escape or are rejected.” Christophers and Stephens state
that in their observations in Sierra Leone the food of the Anopheles larvee seemed
to be an unicellular organism. James and Liston state that the food of Anoph-
eles larve consists chiefly of minute water animals which abound among alge
and other water plants. They believe that the larve can not subsist upon vege-
table diet alone and that the duration of the larval stage depends chiefly upon the
supply of animal food. When this is small in proportion to the number of larve,
they state, the stronger larve kill and eat the weaker. The cause for the dis-
crepancies in these observations undoubtedly lies, at least in part, in the fact that
different species were under observation. Thus we have found that the tree-hole
inhabiting larve of our Celodiazesis barberi are very largely predaceous and
prey upon other culicid larve associated with them. The species inhabiting
bromeliads have similar habits, as has been recorded for Anopheles cruzti by
Peryasst.
LENGTH OF EARLY STAGES 231

RESISTANCE TO DESICCATION.

One of the points of importance in considering the eggs and larve of the
malarial mosquitoes is their possible resistance of desiccation. Exact observa-
tions on this point are still needed. Instances of supposed resistance on the part
of larvee must be studied from every side with care before forming conclusions.
Nuttall and Shipley give an account of two observations made at Gainsborough,
where many fully developed larve and pup were encountered in ditches which,
according to persons living in the vicinity, had been filled with river water after
having been dry from four to seven days. It seemed to the authors at first that
the larve might have been carried in with the water from the river, as larvee were
also found there, but the larvee in the ditches were so numerous as to render this
explanation incompetent for a large part of them. In all probability the ditches
in question had not been completely dried out. The authors call attention to
the fact that Christophers and Stephens in Africa found that no large larve
Teappeared in a pool which had been dried up for two days and then refilled with
rain-water. The larve which did appear were very small, and issued from eggs
which apparently had resisted desiccation for the two days in question.

James and Liston point out that when Anopheles eggs are laid on water they
almost invariably hatch in 48 hours, but that when laid upon damp mud the
development of the embryo goes on and when water is added the larve hatch out
almost immediately. They point out that in Mian Mir Christophers found
that after the water in an drrigation canal or pool had been emptied out the
Anopheles st laid their eggs on the soft mud and that if water entered before
the mud had become completely dry young larve would almost immediately be
found. After giving the details of his observations, James and Liston state, “ It
will be seen therefore, that pools which are, to all intents and purposes, quite dry,
may contain numerous larve almost immediately after a shower of rain.”
Christophers also found that larve may remain alive on soft mud even after
exposure to the sun for several hors, but were killed when the mud had so far
dried as to lose its glistening surface.

The observers of the Instituto Oswaldo Cruz at Rio de Janeiro made experi-
ments with Anopheles albimanus and A. argyritarsis, the two species of greatest
economic importance in tropical America. When the larve were dried on filter
paper, in the laboratory, they were still alive after six hours. On moist mud
they remained alive six days.

LENGTH OF EARLY STAGES.

The duration of the early stages of Anopheles varies according to the tempera-
ture and food-conditions. With the heat the growth is faster; food supply also
governs the duration of the larval stage. In India Liston found that the larval
state might last but a week, but with a deficient food supply it might last for a
month. Foley and Yvernault record the development of Anopheles chaudoyet
from egg to imago within 13 days. The early observations made by one of us
(Howard) on Anopheles quadrimaculatus at Washington showed a minimum
larval period, in May and June, of sixteen days, and a pupal period of five days ;
eggs, three days—these periods undoubtedly being reduced later in the summer.

“~
232 MOSQUITOES OF NORTH AMERICA

-

NUMBER OF GENERATIONS.

The general impression is that, in temperate regions, there are several genera-
tions of Anopheles during a season and that they continue to reproduce while
conditions are favorable. Kulagin, in Russia, appears to have been the only one
who has investigated the question carefully and after observations through
several years he concluded that there is but a single generation annually, the
imagos issuing from pupe not laying eggs until the following year. It is well
known that the female Anopheles do not lay all their eggs at one time. Accord-
ing to Kulagin the egg-laying period is extended over the entire summer through
the fact that some of the Anopheles do not leave their hibernation quarters until
well into the summer. He points out that in the female Anopheles examined by
Koschewnikow late in July all showed a strongly developed fat supply and un-
developed ova and that the presence of the fat was a preparation for hibernation.
We have already mentioned that in this country Smith has found the hibernat-
ing Anopheles in similar condition.

The observations made by Kulagin in 1906 are very convincing. In that
year there was a very early spring in the province of Moscow; the temperature
rose very high in April and there were no cold days. As a result of these early
favorable conditions the hibernating mosquitoes left their shelters very promptly.
Oviposition followed with the same promptness. He found great numbers of
larve about the middle of April and these developed rapidly. The imagos
issued from the pupe during the last half of May, within a very short period.
From the end of May on, throughout June and July no Anopheles larve could
be found in spite of the most thorough search. Kulagin then points out that the
conclusion is inevitable that in that year the females which issued from pupx
about the middle of May were the ones to hibernate.

Observations made by one of us (Knab) on the mating habits of Anopheles
punctipennis are significant in this connection. This species has been observed
repeatedly, swarming in the manner described on another page, but in every
case observed this occurred well towards the end of the season.

Further observations are necessary to determine if all the species of Anopheles
of the temperate regions agree in the number of generations. As to the tropical
species, practically nothing is known as to the number of generations. Quite
probably in certain regions, where there is an abundance of water throughout the
year, breeding is continuous. In parts of India, where there is a long, well-
marked dry season, the behavior of the Anopheles appears to be much as in colder
climates, only that in this case the dry time is the resting period. Stephens and
Christophers state that in India estivating Anopheles, although they feed at
intervals, will not deposit eggs even if suitable deposits of water are present.

GEOGRAPHIC DISTRIBUTION OF MALARIA.

The distribution of malaria coincides in a way with the distribution of the
mosquitoes of the genus Anopheles; that is to say malaria does not originate in
localities where Anopheles does not exist; but on the other hand there exist
many localities where there are Anopheles where malaria is not to be found.
DISTRIBUTION OF MALARIA 233

Such localities or such regions are either those into which malaria has never
been introduced or those in which it has been absolutely stamped out. Also the
species of Anopheles present may be such as do not act as efficient hosts for
the malarial parasites, or, as has been already indicated on a previous page, the
proper species of Anopheles and of malarial organisms may not coincide. A

general consideration of the geographic distribution of the disease is given by
Shipley as follows:

“Roughly speaking, malaria is confined to a broad irregular belt running
round the world between the 4th isothermal line north of the Equator and the
16th line south. It is, however, said to occur occasionally outside these limits—
for instance, in Southern Greenland and at Irkutsk in Siberia; but until recently
the accurate diagnosis of the disease has been difficult, and too much reliance
must not be placed on these statements. The chief endemic foci of the disease
are along the banks and deltas of large rivers, on low coasts, and around inland
lakes and marshes. Malaria is common all round the Mediterranean region:
it was well known to,and its symptoms were clearly noted by, the early physicians
since the time of Hippocrates. They even recognized the difference between
the mild spring and summer attacks and the more pernicious effects of the
autumnal fever. In France there are several prominent malarial districts: the
valley of the Loire and its tributary the Indre, and the valley of the Rhone;
also the sea-coast stretching from the mouth of the Loire to the Pyrenees, and
again the Mediterranean sea-board. It occurs in Switzerland, and is found in
Germany along the Baltic coasts, and on the banks of the Rhine, the Elbe, and
other rivers, and in many other parts. Scarcely a province in Holland is quite
free from it, and it is found in Belgium and around Lake Wener, in Sweden.
It extends along the Lower Danube and around the Black Sea, and spreads
across Russia, being especially prevalent along the course of the Volga and
around the Caspian. From Europe it spreads over Asia Minor, and affects all
Southern Asia as far as the East Indies, but in Japan it is curiously rare. It
is also infrequent in Australia—where it is confined to the northern half of the
continent—and in many of the Pacific Islands; and it is unknown in the Sand-
wich Islands, New Zealand, Tasmania, and Samoa. In America it is more
common, and of a more severe type on the Atlantic sea-board than on the Pacific ;
in the last hundred years its northern limit is said to have retreated in the
centre of the continent, though some observers think it is creeping further north
in the Eastern States. Ina mild form it is known around the Great Lakes, and
in Canada and in New England; but it reaches a high degree of intensity in the
Southern States, Mexico, Cuba, and Central America, where it probably played
a greater part in ruining the projected Panama Canal than all the corrupt
financing of the speculators in Paris. It extends throughout the warmer parts
of South America, and is known in a virulent form all over Africa except the
extreme south.

“Tn Great Britain it used to flourish. The following extract from Graham’s
© Social Life of Scotland in the Highteenth Century ’ shows what a part it played
in the life of the Scottish peasant:

“¢ The one ailment to which they were most liable, and in which dirt had no
share, was ague. This was due to the undrained land, which retained wet like
a sponge, and was full of swamps and bogs and morasses in which “ green grew
the rushes.” Terribly prevalent and harassing this malady proved to the rural
classes, for every year a vast proportion of the people were prostrated by it, so
that it was often extremely difficult to get the necessary work of the fields per-
formed in many districts. In localities like the Carse of Gowrie, which in those
234 MOSQUITOES OF NORTH AMERICA

days abounded in morasses and deep pools, amongst whose rushes the lapwings
had their haunt, the whole population was every year stricken more or less with
the trouble, until the days came when drainage dried the soil, and ague and
lapwings disappeared.’

“In England it was once very prevalent. James I. died of ‘a tertian ague
at Theobalds, near London, and Cromwell succumbed at Whitehall to a ‘ bastard
tertian ague’ in 1658, a year in which malaria was very widely spread and very
malignant; and it is only within recent memory that the fen districts in Cam-
bridgeshire and Lincolnshire, Romney Marsh in Kent, and the marshy districts
of Somerset, have lost their evil reputation for ague. The older chemists in the
towns in the fen districts still recall the lucrative trade their fathers carried on
in opium and preparations of quinine with the fenmen during the first half of
last century ; but with the improved drainage of the fens this has all disappeared,
and at present cases of endemic malaria appear to be unknown in England,
though sporadic cases turn up at rare intervals. It was also very prevalent along
the estuary of the Thames, both on the Essex and Kentish marshes. Pip in
* Great Expectations’ says to his convict:

“¢T think you have got the ague.’ ‘I’m much of your opinion, boy,’ said he.
“It’s bad about here,’ I told him. ‘ You’ve been lying out on the meshes, and
they’re dreadful aguish.’

“ Treland, which appears at first sight peculiarly adapted for the disease, seems
to have been remarkably free from it. It may be that the strong antiseptic
quality of the peaty bog-water hinders the development of the larval mosquito.” *

According to Hirsch malaria in Europe extends northward to between 63°
and 69° north latitude. In the western hemisphere it is rarely found above 45°
north latitude. It is most common and severe in low-lying coast regions and
the deltas of large rivers, the rivers of tropical countries especially, are hot-beds ;
and this is true also of all bodies of water in such localities. As we approach the
equator we meet more rarely with the milder forms and more frequently with
the severe and often fatal estivo-autumnal variety. Craig gives a more detailed
consideration to America than does Shipley, and his paragraphs on North and
South America, Asia, and Africa are quoted:

“ North America.—In North America, malaria occurs rarely above the forty-
fifth parallel, but is often frequent and fatal in the Southern states and in the
West Indies, especially in Cuba, as well as in Central America. In the New
England and Middle Atlantic states the benign forms are present, but are
comparatively rare. The severe forms prevail along the low regions of the south-
ern coast line, and especially in the swampy regions of the Gulf states. These
infections are common and severe along the Mississippi River and its southern
branches, and they are present in many of the Western states, especially in the
river valleys of California where severe and fatal estivo-autumnal infections are
not uncommon. The regions about the Great Lakes are almost free from malaria
except in certain localities about Lake Michigan. Canada is the only country in
North America which appears to be almost entirely free from malaria.

“ South America.—In South America, severe types of the disease are common,
especially along the coast regions of Colombia, Venezuela, Guiana, Brazil,
Eucador, Peru and Chile. The whole Atlantic coast line of Central America is
severely infected with estivo-autumnal malaria, and in this region the most
pernicious forms are common.

o>

 

* Anopheles is prevalent in parts of Ireland. It {s worthy of remark that as early as 1828
Hallday, in his paper entitled ‘On some insects taken in the north of Ireland” (Zoological
Journal, ill, 1828, pp. 500-504), states that A. maculipennis occurs in profusion in the neighbor-
hood of Belfast throughout the summer and autumn.—H,, D. and K.
MALARIA AND ALTITUDE 235

“ Asia.—India, Ceylon, portions of China and Arabia, and the Islands of the
Malay Archipelago are infected with the malarial fevers. This is also true of
Asia Minor and the valleys of almost all the great rivers, such as the Indus and
Ganges. In Japan the benign infections are common, and even upon the lofty
table lands near the Himalayas malarial infections are often met with. The
Philippine Islands, until very recently considered as comparatively free from
malarial diseases, have been proved to be badly infected, a large percentage of
our soldiers returning from there showing infection with the tertian and estivo-
autumnal parasites.

“ Africa.—In Africa are some of the most dangerous lurking places of
malarial infections, the worst areas being those along the west coast and the
Senegal, Congo, and Niger Rivers, as well as the regions around the great lakes
and the jungles, and lake shores of Abyssinia. Madagascar, Reunion, and
Mauritius Islands present the pernicious varieties of the disease. Around
Delagoa Bay and along the east coast of Africa, estivo-autumnal fever is prev-
alent. Lower Egypt, the Soudan, the Nile delta, Tripoli, Tunis and Algeria,
all harbor these infections.”

Regarding the vertical distribution of malaria it may be said in a general way
that malaria decreases with the increased altitude above sea level. The govern-
ing factors are, on the one hand, the unfavorable effect of low temperatures on
the development of the malarial organisms, on the other hand, the absence in
many mountainous regions of conditions upon which the abundance of Anoph-
eles depends. Nevertheless malaria does occur at considerable altitudes in
various parts of the world, apparently going highest in the Andes of South
America. According to Treutlein, at La Paz, Bolivia, it reaches an altitude of
2564 meters. This author states that while endemic malaria, on account of the
conditions, unfavorable to mosquitoes, does not occur at La Paz it exists on the
plain of Potopoto, 100 meters lower, where Anopheles breed in some numbers.
Ziemann gives the following summary of the occurrence of malaria at high
altitudes :

“While, for example, in Ceylon malaria no longer occurs at 500 meters above
sea level, the writer still found malaria in Cameroon and also in the Manenguba
mountains at about 900 meters altitude; however no longer from 1200 meters
on in the grass land, and the distribution of malaria and of anophelines seemed
to agree pretty closely. Steuber still found malaria in German Hast-Africa at
Lake Nyassa at an elevation of 1560 meters. In the mountainous regions of
Usambara the conditions appeared to be similar to those of Cameroon in that
malaria there still occurred at 800 meters altitude. In the Himalaya mountains
it is said that malaria is still found at a height of 2000 meters, in the Andes of
Peru even to 2500 meters, in the high lands of Persia, on the other hand, only to
1500 meters. In the German mountains malaria rises to 400-500 meters, in
Italy to 600-1000 meters. Recently Grassi even found there an endemic malarial
focus, in the vicinity of Colico, at an altitude 2500 meters. In malarial regions
comparatively slight elevations above the malaria-infected plain are often
sheltered, which one can easily explain, with our present knowledge, by the
relatively small height of the flight of anophelines. Therefore the inhabitants
of malarial regions always withdrew by preference to the surrounding hills. It
is known that the shepherds of the Campagna about Rome passed the nights on
scaffoldings which were several meters above the ground.”

Edmond Sergent states that in Algeria, while Anopheles abound at all times

in altitudes of from 1600 to 1800 meters, malaria occurs in those altitudes only
236 MOSQUITOES OF NORTH AMERICA

in certain years. In these years of malaria it was found that the sirocco, a hot
wind from the desert, blew continuously for nine or ten days. Sergent reaches
the conclusion that usually the very low night temperatures in these localities
inhibit the development of the malarial plasmodii within the mosquito; the
continuous high temperature during the sirocco, however, brings about the de-
velopment of the parasites.

Recently Hehir, in India, has confirmed the observations of Hirsch that in
India and Ceylon malaria occurs up to altitudes of 2000 meters.

Referring again to the United States, it may briefly be stated that malaria
rarely exists in this country above an elevation of one thousand feet or in the dry
climates of certain of the western and southwestern States, except where irriga-
tion has been introduced. This is quite to be expected, from the well-known
habits of the species of Anopheles that carry the disease in this country. There
seems to be little doubt, moreover, that malaria has practically died out in many
localities where once it was rife. In the early settling of the Central and
Western States, malaria was one of the most serious obstacles in the path of the
pioneers, but with the gradual improvement of agriculture, with the cutting
down of the trees in swampy forests, increased value of land for agriculture and
the consequent reclamation of swamps, the disease has disappeared in many
wide-spread regions; yet Anopheles still retains its foothold in many of these
regions, although in vastly smaller numbers than in former years. Over other
large regions the disease, while vastly less in relation to the population, still
exists and is carried from one person to another by the reduced supply of
Anopheles. In such large regions there are often smaller areas, where, through
local breeding-places, a large supply of Anopheles is kept up and the disease
maintained at a higher rate through their instrumentality.

THE APPEARANCE AND DISAPPEARANCE OF MALARIA.

In the section on economic loss from mosquitoes we have referred to the fact
that the development of the United States in many sections has been retarded
for years by the prevalence of malaria. The army of pioneers pushing west,
stopping at various apparently favorable spots, clearing farms and settling for
a time at least to build homes, encountered malaria in many places. Some of
them were killed off or disabled by this disease, others, discouraged, were
driven back east, while others pushed further west. But in very many of the
localities where malaria was once existent in severe form, it has gradually
lessened more and more, until localities once extremely unhealthy are now among
the healthiest regions of the country. This means the gradual disappearance of
malaria under the influence of civilization. We shall briefly discuss this class of
phenomena from the viewpoint of the breeding places of malarial mosquitoes,
and will show by contrast that under other conditions advanced civilization
may bring malaria into localities in which it formerly did not exist.

DECREASE OF MALARIA FOLLOWING SETTLEMENT AND CIVILIZATION.
It has been shown in our discussion of the geographic distribution of malaria
that the disease formerly flourished in Great Britain, and it is well known that
LOCAL DECREASE OF MALARIA 237

its disappearance in that country had been due entirely to the improved drainage
of the marshes or fens. It is comparatively recently that the marshy and fen
districts have lost their malarious reputation. At present, however, cases of
endemic malaria appear to be unknown in England, although sporadic cases are
met with rarely.

The early conditions in certain of the United States were very similar, and
the improved conditions are due to the same cause. In the great agricultural
middle western States of Ohio, Indiana, Illinois, Michigan, and Wisconsin,
where malaria played such great havoc during their settlement through more
than the first half of the nineteenth century, there were great areas of swamp
land, and it is in those states that swamp reclamation as a whole has been
carried out on the largest scale. At the present time these great areas, once
breeders of Anopheles in extraordinary numbers, constitute the most fertile and
productive land in the whole region. How recently and how rapidly the change
has come about is indicated, for one locality in Michigan, by Jordan and
Hefferan (loc. cit.), and may be quoted:

“A. The Locality The observations were made in and about the village of
Eastmanville, in western Michigan, during the summers of 1902, 1903 and 1904.
A white settlement has existed at this point, upon the north bank of the Grand
River, twenty miles (river measurement) from its debouchement into Lake
Michigan, since about 1840. Prior to that date, and for some time afterward,
Indians of the Ottawa and Pottawatomie tribes had villages near this part of
the river. The population of the village, never more than a few hundreds, is at
present about 150.

“The soil of the district is clay, covered by a few feet of sand for the most
part, but occasionally cropping out. The country-side is almost entirely under
cultivation or in pasture land ; little or nothing remains of the marshes or of the
heavy timber which formerly covered the area. The north bank of the river,
upon which the village lies, rises with somewhat more marked declivity than the
south, which is sandy, the channel being here, for two miles, on the north shore.
The stream is at this point thirty rods wide; the vegetation of the shores is
characterized by low willows and wild rice. North from the river run several
ravines, dry in summer except for occasional spring-fed pools. Opposite the
village, and separated from the river by a strip fifteen rods wide, part sand and
part marshland, is a deep currentless bayou, mud-bottomed, spring-fed, ten rods
wide and two miles long. With the exception of a few rods, its shores are
timbered ; the vegetation is that of a spring-fed lake.

“B. Malarial History—tThis part of Michigan was in earlier times, accord-
ing to tradition, one of the worst malarial districts in a highly malarial state.
No records except the general State Reports for western Michigan are available
to show the former prevalence of malaria in Eastmanville, but the testimony of
all the older settlers is unanimous. Everyone in the district was a sufferer, and
everyone who came to the district expected to contract the disease. From the
strongest of the laboring men to the infant born on the mother’s ague day, the
entire population was subject to chills and fever.

“ Such conditions do not now exist. The Michigan State Board of Health
Reports contain interesting statistics regarding the decrease of malaria in Michi-

gan during twenty-three years:
238 MOSQUITOES OF NORTH AMERICA

“WrrExLy Reports oF DISEASES IN MICHIGAN.

“ PER CENT. OF REPORTS WHICH SHOWED INTERMITTENT FEVER.

 

TST Giwss eats 15% 1884 36% 1898
1878....... 82 1885 . 27 1899...
1879....... 82 1886.. . 24 1900...
1880....... 82 1887.. 24 1901
1881....... 82 1888 22
1882....... 71 1889 19

 

“Tn 1879, 1880 and 1881, intermittent fever was the most prevalent of all
diseases in Michigan; in 1881 the western division of the State, including the
locality described above, showed a greater prevalence of malaria than other
parts of the State, 90 per cent. of all weekly reports recording the disease as
under the observation of the physician making the report. But according to the
statements of local physicians the disease has been very infrequent in and about
Eastmanville for the last few years. One physician had observed during six
years but three cases presenting a typical malarial history ; one of these occurred
in the summer of 1889, one in 1902, and one in 1904. All three patients lived
on the bank of the river, at distances of several miles from one another.

“The question of course arises whether this decrease in malaria has been
paralleled by a decrease in the number of the malaria-carrying mosquitoes. In
the absence of data, no definite statement can be made regarding the number and
virulence of mosquitoes in the earlier years of the settlement, except the very
general one that they were much ‘more numerous’ than at present, and that
they were very large. They were felt as so real a pest that the farmers would
often leave the unscreened houses to sleep in the barns and haylofts, which were
not frequented by mosquitoes.”

The effect of drainage as a corrective of malaria was naturally noticed long
before the fact that Anopheles is the carrier of the disease was discovered, and
in the earlier works a number of such instances have been pointed out. We have
already referred to the extensive drainage of the fens in England, and of course
the sanitary benefit arising from this drainage was at once perceived. In his
excellent work on malaria and malarious diseases (New York, 1884), Sternberg
refers to the case of Boufaric in Algeria which was noted for its unhealthiness.
Successive importations of soldiers and colonists died off from malaria. Deep
drainage was resorted to, and the level of the ground-water was lowered less than
two feet. Too this measure was attributed the reduction of the mortality to about
one-third. He points out that the completion of the system of drainage in the
towns of Fairfield and New Milford, Connecticut, resulted in the steady and
rapid decrease of malarial diseases. He further shows that, according to Colin,
while the laborers engaged in drainage measures often suffer very severely from
malaria, the subsequent effect is to greatly increase the health of the locality.
He cites the instance of Staouéli in Algeria, where the reclamation by drainage
of the lands belonging to a Trappist convent cost, during the first years, the lives
of eight monks out of twenty-eight and of 27 soldiers out of 150 who were placed
at their disposal. The improvement in the health following the drainage, how-
ever, was very great, and in eighteen months there were but two deaths out of

a population of 152.
IRRIGATION AND MALARIA 239

It will be seen that these beneficial results—and the same experience has been
repeated in many other parts of the world—have been brought about through
the swamp drainage necessitated by the demand for more and richer agri-
cultural land and without regard to health conditions, except possibly in-
cidentally in a few instances. In this way, then, the improvement by agri-
culture has worked towards the arrest of malaria and the improvement of
health. There still remain in portions of the United States many very fertile
regions the agricultural and industrial development of which is only beginning
or has not yet been touched. We have pointed out that the tide marshes around
Puget Sound in Washington, which have been lying untouched until within
the last few years, are now about to be reclaimed through great immigrations of
new and desirable settlers, while in California, in the Sacramento-San Joaquin
delta, the same work is beginning; also that the immensely fertile delta regions
in Mississippi are attracting the attention of the government, and that it is prob-
able that this land, the most fertile land in the world, with possibly the exception
of the delta of the Nile, will not only be reclaimed for agricultural purposes, but
that incidentally these operations will change a malaria-ridden area into healthy
farms.

INCREASE OF MALARIA DUE TO CIVILIZATION AND ITS CONCOMITANTS.

But the advance of civilization does not always bring about these results. It
is obvious that extensive irrigation of desert lands will bring about conditions
allowing the breeding of enormous numbers of Anopheles mosquitoes, and will
ultimately result in the introduction of malaria into portions of the country
where it has not previously existed. This has been shown again and again in
some of the western States. The irrigation ditches of portions of California
breed Anopheles in great numbers. Into some of these localities malaria has
entered and has been rapidly spread by these pernicious insects. Expert horti-
culturists from the U. 8. Department of Agriculture going into these regions in
the course of their scientific investigations, and others, have been forced to
consult the Bureau of Entomology on the subject of anti-malarial measures.

Dr. J. P. Widney, a member of the California State Board of Health, gives
an account of the results of the introduction of irrigation into parts of California
(Report, Cal. State Board of Health, 1881). Doctor Widney divides the lands
under irrigation at that time into four general classes: (1) Uplands, like those
of San Gabriel, Pomona and Riverside, which have a firm soil, rather a gravelly
clay which remains moist but not water-soaked after irrigation; (2) river bot-
toms of sand or alluvium, as those of the Los Angeles and lower Santa Ana, with
a fair slope so that the water does not remain in pools and with a substratum
making under-drainage thorough; (3) the sandy bottoms of the San Gabriel
River, of much the same character as No. 2, but with a much less rapid surface
slope and much less thorough under-drainage; (4) the Cienaga lands, having
a heavy soil of the adobe type, occasionally springs and bogs, with natural ponds
of water, very wet in the winter. Doctor Widney discussed specifically the re-
lation of malaria to these four types of irrigated lands, and found that the lands
240 MOSQUITOES OF NORTH AMERICA

of the first-class are almost entirely free from even the slightest trace of malaria
and that the lands of the second class show its existence but not to a sufficient
degree to form a marked feature in the endemic causes of the disease ; the lands
of the third class he states showed the presence of malaria in a notably active
form, giving a well-marked type to the summer diseases, while those of the
fourth class developed with irrigation a very active form of malaria, the diseases
as a whole being largely of a pronounced malarial type and running often a very
severe course. While naturally totally unsuspicious, at that time, of the connec-
tion of mosquito-breeding places with the case, Doctor Widney comes to a very
just conclusion, as follows:

“The conclusion seems to be fairly just and legitimate, then, in the absence
of any other apparent cause, and from what we know of the close connection
between defective drainage and malaria, that in this case the relationship is that
of cause and effect. With thorough drainage, the places which, by all other
rules, should develop malaria, escape it almost entirely; without drainage, the
places which, by all other rules, should be free from it, develop it constantly and
actively. The whole history of irrigation in southern California goes to impress
this lesson: that, to escape malaria, drainage must go hand in hand with irriga-
ce ; that unless it does, the water which brings wealth brings also disease and

eath.

We have already pointed out that in tropical Africa, as shown by Dutton in
his investigations in Gambia, the number of mosquito breeding-places in com-
pounds varies with the social position of the occupier, and that civilized methods
of life are apt to increase the number of breeding-places of those species of
Anopheles most nearly domesticated. While with us Anopheles does not breed
to any appreciable extent in small receptacles, yet the activities of civilized life
increase the breeding facilities of mosquitoes in many ways. This helps in some
cases to account for the rapid spread of malaria in regions where it was before
unknown. For example the well-known malarial outbreak in Brookline, Massa-
chusetts, following the employment on the reservoirs of Italian laborers, some of
whom undoubtedly brought the malarial organisms in their systems into a
region where Anopheles quadrimaculatus was breeding. It is altogether likely
that the epidemic which spread through a large part of New England in the
latter portion of the last century can be accounted for in a similar way. De-
pendent as this disease is upon the Anopheles mosquitoes, the number of breed-
ing-places determines the spread of the disease when once introduced. It should
be remembered that the breeding-places brought about in increased numbers by
civilization include, in addition to irrigation, not only the purposely prepared
water receptacles and those accidentally brought about by domestic life, but col-
lections of water brought about by different industrial operations. We may
mention mill ponds which, where they have grassy borders and cause the back-
ing up of rapid streams for a long distance into fishless shallows and swampy
pools form admirable breeding-places for Anopheles. We may mention aban-
doned stone quarries and even those in active operation, which nearly always
cause considerable accumulations of fishless water, and soon, as we have often
seen, become inhabited by large numbers of Anopheles larve as well as the
YELLOW FEVER 241

larvee of other mosquitoes. The borrow-pits along the right-of-way of railroads
furnish ideal facilities, in many cases, for the breeding of mosquitoes including
Anopheles. We may mention also the numerous excavations large and small
made for one purpose or another which, if they have a firm soil, will accumulate
water and form breeding-places (artificial pools for watering stock are ex-
amples), and of course stagnant street and roadside gutters and the footprints
of cattle and horses in moist land and the plow furrows in clayey corn land in
wet seasons are Anopheles’ breeding-places, dependent absolutely upon civiliza-
tion. And we must not forget railroad embankments as obstructions to very
small streams of running water and as the cause of very extensive accumulations
of fishless waters often swarming with mosquito larve. Thus in very many
loealities it is not surprising that, with an entire lack of anti-mosquito measures,
the conditions of civilization have greatly increased the possibilities of serious
malarial troubles when the disease is once introduced.

With these facts in view, it is interesting to read such a paper as that by Dr.
C. V. Chapin on “ The Origin and Progress of the Malarial Fever now Prevalent
in New England ” (Providence, R. I., 1884), in which he traces the spread of
the disease from shore towns in Connecticut in 1860 gradually over a large part
of New England, long before the true method of spread was known. Here was
a typical case of a non-malarious region in which the Anopheles breeding con-
ditions described above had been continually increasing for years until, the dis-
ease once introduced into those Connecticut shore towns, found malaria-carriers
everywhere and its spread was thus assured. Some of these breeding-places are
even mentioned by Dr. Chapin without a realization of their true significance,
and in fact the first outbreak in Connecticut occurred near dams and millponds.

YELLOW FEVER.
THE SCIENTIFIC DEMONSTRATION OF THE CARRIAGE OF YELLOW
FEVER BY MOSQUITOES.

Physicians had been theorizing about the cause of yellow fever from the time
when they began to treat it. It was thought by many that it was carried in the
air; by others that it was conveyed by the clothing, bedding, or other articles
which had come in contact with a yellow-fever patient. There were one or two
early suggestions of the agency of mosquitoes, but practically no attention was
paid to them, and they have been resurrected and considered significant only
since the beginning of the present century. With the discovery of the agency of
micro-organisms in the causation of disease, a search soon began for some causa-
tive germ of yellow fever. Many micro-organisms were found in the course of
the autopsies, and many claims were put forth by investigators. All of these,
however, were virtually set at rest by Sternberg in his “ Report on the Etiology
and Prevention of Yellow Fever,” published in 1890. But a claim made by
Sanarelli in June, 1897, for a bacillus, which he found in 58 per cent of yellow-
fever cases and which he called Bacillus icteroides, received considerable cre-
dence. Wasdin and Geddings, of the United States Marine-Hospita] Service,
in 1899, reported that they had found this bacillus in a large percentage of
242 MOSQUITOES OF NORTH AMERICA

yellow-fever patients in the city of Havana. Their work, however, was not
carried to a satisfactory end and they stated that they had found no conclusive
evidence that this bacillus was responsible for yellow fever. About the same
time Archinard and Woodson, at New Orleans, obtained results which they con-
sidered confirmatory of Sanarelli’s claim. Afterwards it was shown by Reed
and Carroll that the organism in question was identical with the bacillus of hog
cholera and in no way concerned with yellow fever.

FINLAY’S WORK.

In 1881 Dr. Carlos Finlay, of Havana, proposed the theory that yellow fever,
whatever its cause may be, is conveyed by means of a certain mosquito (Culex
mosquito = Aédes calopus) from man to man, and not in the manner of ordi-
nary contagious or infectious diseases. His paper, published in the “ Anales de
la Real Academia de Ciencias médicas, fisicas y naturales de la Habana,” shows
that he had carefully studied the habits of house mosquitoes and had determined
all the factors in the life-history of Aédes calopus which have since been shown
to be essential in its réle of transmitter of the disease. It was this careful study
of the mosquito and the disease, conducted through many years in the most
favorable locality, in the city of Havana, that gave him a firm conviction that the
two were interdependent. On this account his theory has true scientific merit,
it was based on intensive study, and not, as had been the case with his prede-
cessors, on vague suspicions or flights of the imagination.

Subsequently Finlay published a number of important papers, in which his
views were modified from time to time. He thought out carefully the question
of immunization and concluded that this was brought about by mild infection,
through the bite of single mosquitoes. In one of his papers he published experi-
ments with 100 individuals, producing 3 cases of mild fever. None of the cases,
however, was under his full control, and as the possibility of other methods of
contracting the disease was not excluded his claims were not accepted. There-
fore, his theory, while it was received with interest, was not considered to be
proved.

DR. A. C, SMITH’S EXPERIMENT.

An interesting experiment, generally overlooked, was tried, based on the ideas
of Finlay of the mosquito dissemination of yellow fever, in the summer of 1897
and prior to the exact work of the United States Army Board in Havana, shown
in the following paragraph, by Past Surgeon A. C. Smith, of the then U. 8.
Marine-Hospital Service (now the U. 8S. Public Health and Marine-Hospital
Service). Doctor Smith screened all the windows and doors of the National
Quarantine Station on Ship Island, Gulf of Mexico, and no case of yellow fever
developed at the station, although he treated some thirty cases of the disease
brought there by infected vessels. We take this statement from a paper by Dr.
P. H. Bailhache, Surgeon U. 8. Public Health and Marine-Hospital Service,
read before the first anti-mosquito convention in New York, in 1903.
PROOF OF MOSQUITO ROLE 243

DEMONSTRATION BY THE UNITED STATES ARMY COMMISSION.

In 1900 the facts were determined by scientific methods. An American
army being at that time stationed in Cuba, a medical board was appointed by
Surgeon-General Sternberg for the purpose of investigating the acute infectious
diseases prevailing in the Island. The Board consisted of Walter Reed, James
Carroll, Jesse W. Lazear and Aristides Agramonte. Dr. Reed was the chairman
of the Board. In the course of the work yellow fever naturally received the main
share of attention. The claims of Sanarelli’s Bacillus icteroides were disproved,
and Reed and his associates began a careful and thoroughly scientific investi-
gation of the possibilities of mosquito carriage of the disease. The experiments
carried on by the Board were as perfect in their methods as it was possible for
scientific acumen and hard common sense to make them. Every possible element
of error seems to have been guarded against. The final and conclusive tests,
made during the autumn of 1900, were conducted with a spirit of earnestness,
self-sacrifice and enthusiasm, which affected every one connected with the work,
even in the most subordinate positions, private soldiers not only offering them-
selves for the presumably dangerous test, but insisting that they should be
accepted as subjects for experimentation. Dr. Reed, the master spirit of the
investigation, was, moreover, the man above all men for this work, no less in
his ability to compel the greatest confidence and enthusiasm, than in the abso-
lutely complete manner in which the experiments were conducted. While the
work was going on, criticism was invited and urged from Havana physicians,
from visiting surgeons, and from every one interested, but so perfect were the
plans that it seems impossible that any criticism could have been made.

An experimental sanitary station was established in the open, a mile from
Quemados. Two houses were built, tightly constructed, with windows and doors
protected by wire screens. In one of these houses soiled sheets, pillow-cases, and
blankets were used as bedding, and this bedding was brought straight from the
beds of patients sick with yellow fever at Havana. For sixty-three days these
beds were occupied by members of the hospital corps for periods varying from
twenty to twenty-one days. At the end of this occupation the men, who were all
non-immunes, were taken to quarantine for five days and then released. Not one
of them was taken ill. All were released in excellent health. This experiment
is of the greatest importance, as it demonstrates that the disease is not conveyed
by fomites. Hence the disinfection of clothing, bedding, or merchandise,
formerly supposed to have been contaminated by contact with yellow-fever
patients, is unnecessary; the disinfection work, which has been carried to the
extreme in cases of yellow-fever epidemics in our southern States, has been
perfectly useless.

In the other house, which was known as the “ infected mosquito building,”
were no articles which had not been carefully disinfected. The house contained
two rooms, and non-immunes were placed in both rooms. In one room, sepa-
rated from the other by wire-screen partitions only, mosquitoes which had bitten
yellow-fever patients were introduced. In the other room they were excluded.
In the latter room the men remained in perfect health; in the mosquito room

17
244 MOSQUITOES OF NORTH AMERICA

50 per cent of the persons bitten by infected mosquitoes (that had been kept
twelve days or more after biting yellow-fever patients) were taken with the
disease, and the yellow-fever diagnosis was confirmed by resident physicians in
Havana who were above all others familiar with the disease in every form.
Persons bitten by mosquitoes which had bitten a yellow-fever patient within
less than twelve days did not contract the disease. In another series of experi-
ments, seven persons were bitten by infected mosquitoes by placing the hand in
a jar containing the insects, and five of them, or 71 per cent, contracted the
disease.

It was also found that yellow fever was produced by the injection of blood
from the general circulation of a patient. Subcutaneous injections of two cubic
centimeters of blood were followed by the disease, and the definite conclusion
was reached that the parasite of yellow fever must be present in the general cir-
culation, at least during the early stages of the disease, and that yellow fever
may be produced, like malarial fever, either by the bite of the mosquito or by the
injection of the blood taken from the general circulation. From these results
this important corollary was reached, to quote Dr. Reed’s own words: “ The
spread of yellow fever can be most effectually controlled by measures directed
to the destruction of the mosquitoes and the protection of the sick against the
bites of these insects.”

One must be struck with the modesty of the men composing the Commission
when, without a single symptom of self-laudation, the results of this remarkable
experimental work, destined to revolutionize former ideas, were published under
the simple title, “ The Etiology of Yellow Fever; An Additional Note.” Re-
ferring again to the experimental patients it must be conceded that the heroism
exhibited by these persons is beyond praise. Speaking of John R. Kissinger, a
young Ohio soldier who was the first person bitten by infected mosquitoes, Dr.
Reed says:

“T can not let this opportunity pass without expressing my admiration of the
conduct of this young Ohio soldier who volunteered for this experiment as he
expressed it ‘solely in the interest of humanity and the cause of science, and
with the only proviso that he should receive no pecuniary reward. In my
opinion, this exhibition of moral courage has never been surpassed in the annals
of the Army of the United States.”

The next three cases were Spaniards, and all of these first four contracted the
fever. After that, no more Spanish subjects could be secured. They had
allowed themselves to be bitten largely through incredulity and for a money
reward. After the fever appeared they lost their interest in the cause of science
and preferred safety to money. Other Americans, however, immediately volun-
teered, and, while praising their courage in the highest degree, we must not fail
to point out here that the inspiration was derived from Dr. Reed himself. Noth-
ing but the most absolute confidence in this remarkable man could have gained
his subjects; and the confidence was justified, since this series of experiments,
the results of which has already been of inestimable value to humanity, was
completed without the loss of a single life as the direct result of the strictly ex-
RESEARCHES IN BRAZIL 245

perimental work. It is true that Dr. Lazear died of yellow fever during the
course of the investigation, but the bite by which he was inoculated was not
given in the course of the experimental work. Dr. Reed himself died three years
later; his death having been indirectly the result of his arduous labors on the
Board. Dr. Carroll died still four years later and his death, too, was probably
caused indirectly by the yellow fever which he contracted in 1900 in the course
of the experiments. Kissinger is reported, at the time of the present writing,
to be living in the State of Washington, and in very enfeebled health. Efforts
are being made to secure for him a well-deserved pension.

After the publication of the first note by the Board some incredulity was ex-
pressed, and the British Medical Journal stated of the experiments, “ At the
most they are suggestive.” After the publication of the additional note, however,
the medical profession accepted the conclusion of the Commission more gen-
erally. During this work, and for months subsequently, continued investi-
gations were carried on by members of the Board, searching for the causa-
tive organism of yellow fever, but it has not yet been found. It was discovered
that the disease could be conveyed not only by the puncture of the mosquito, but
by the injection of the blood serum of a yellow-fever patient into the system of a
non-immune. It was further discovered that this blood serum could be filtered
through a porcelain filter and yet retain its power to convey the disease. It was
Dr. Carroll’s theory that the cause of the disease is some micro-organism so ex-
cessively small as to fail to reveal itself to the highest powers of the microscope,
and this view has generally been accepted.

LATER WORK IN CUBA BY GUITERAS AND JOHN W. ROSS.

Additional experiments were carried on in 1901 by the Havana Board of
Health, under Dr. Juan Guiteras. In a number of cases the disease was experi-
mentally conveyed by the bites of infected mosquitoes. Later in the autumn and
winter of 1901, very careful experiments were carried on at Las Animas Hos-
pital by the Director of the Hospital, Surgeon John W. Ross, of the U. S. Navy,
and these experiments were made for the purpose of setting at rest the theory
still adhered to, by many, of the transmission of the disease by fomites. Certain
rooms in the hospital were made mosquito-proof and numerous bundles of bed-
clothes and bedding, which had recently been used in sickrooms and on the
persons of people ill with yellow fever, were placed in these rooms. Eight men,
recently arrived on the Island, 5 Spanish, 2 Italian and 1 English, were taken
as subjects for experimentation. They were placed under observation for 7 days,
then transferred to the experiment room, where they were kept for 7 days. They
were then kept under observation for 7 days longer, with the result that all
emerged from the experiment in good health.

WORK DONE IN BRAZIL BY THE SAO PAULO AND THE FRENCH COMMISSIONS.
In spite of the perfect scientific character and convincing nature of the work
done at Havana, the medical world was by no means unanimous in accepting
the conclusions. Among the first countries to take up the work was Brazil. Dr.
246 MOSQUITOES OF NORTH AMERICA

Emilio Ribas, Director of the Health Service of Sao Paulo, and Dr. Adolfo Lutz,
Chief of the Bacteriological Institute of the same city, repeated the experiments
in yellow-fever inoculation by means of the yellow-fever mosquito. A com-
mission, composed of Doctors L. Barreto, A. G. da Silva Rodrigues, and A. J.
de Barros, was created to carry on the work. Doctor Ribas and Doctor Lutz
were the first who were pierced by infected mosquitoes, but the results were
negative, undoubtedely because both men had lived for many years in the midst
of yellow fever and had become immune. With three other persons, however,
the Brazilian commission succeeded in January, 1903, in producing character-
istic yellow fever by having them bitten by infected Aédes calopus. These mos-
quitoes came from the town of Sao Simao, situated several hundred kilometers
away from Sao Paulo, and had been allowed to bite yellow-fever patients in
that town where there was at the time an epidemic of the disease. This ex-
periment was a strongly convincing one, for the reason that at the time there
were absolutely no cases of yellow fever in So Paulo and no one could point out
any other method of contagion than by the bite of these mosquitoes brought
from the yellow-fever locality.

In addition to these Brazilian results, the French government, in 1901, sent
a mission to Rio de Janeiro, composed of Messrs. Marchoux, Salimbeni and
Simond, under the scientific direction of the Pasteur Institute. This Commis-
sion brought about some very exact confirmatory results, and in the months of
May and June, 1903, succeeded in producing yellow fever in three cases by in-
oculation by infected Aédes calopus. The report of the Commission and the
subsequent papers by Marchoux and Simond, published by the Pasteur Institute
in several parts extending down to 1906, form a notable contribution to the his-
tory of yellow fever. Their opportunities were great, their methods were most
exact, and they confirmed in every respect the results obtained by the American
commission. Their conclusions, as published in the Annals of the Pasteur In-
stitute, in November, 1903, are sufficiently important to quote:

“(1) The serum of a patient is virulent on the third day of the illness.

“(2) On the fourth day the blood of a yellow-fever patient no longer contains
the virus, even when the fever is higher.

“(3) One-tenth cc. of virulent serum injected under the skin is sufficient to
produce yellow fever.

“(4) The virus of yellow fever placed upon an abrasion of the skin does not
give the fever.

“(5) In the serum of a patient the virus of yellow fever passes through a
Chamberland F filter without dilution.

“(6) Under the same conditions, it does not appear to pass through filter B.

“(7) The virulent serum kept from air at a temperature of from 24 to 30
degrees C. is inactive at the end of 48 hours.

“(8) In defibrinated blood kept under vaseline oil at temperature from 24 to
30, the microbe of yellow fever is still living at the end of five days.

(9) At the end of eight days defibrinated blood kept under the same con-
ditions no longer contains the active virus.

“(10) The virulent serum becomes inoffensive after a heating for 5’ to 55° C.

“(11) A preventive injection of serum heated for 5’ to 55° gives relative
immunity, which, followed by inoculation with a very small quantity of virus,
can become complete.
WORK OF FRENCH COMMISSION 247

_‘“(12) The injection of defibrinated blood, kept in the laboratory under vase-
line oil for eight days at least, gives a relative immunity.

e (13) The serum of convalescents is endowed with clearly preventive prop-
erties.

“(14) The immunity given by the serum of a convalescent is still appreciable
at the end of 26 days.

“(15) The serum of the convalescent appears to have therapeutic properties.

“(16) As proved by Reed, Carroll and Agramonte, yellow fever is produced
by the puncture of Stegomyia fasciata [=A édes calopus].

“(17) To be able to produce the illness with man, this mosquito must be in-
fected, previously, by absorbing the blood of a yellow-fever patient during the
first three days of the sickness.

“(18) The infected mosquito is dangerous only after an interval of at least
12 days after it has sucked virulent blood.

“(19) The punctures of two infected mosquitoes may bring about a very
severe case.

(20) The mosquito appears to be more dangerous in proportion with the
length of time which has elapsed after infection.

(21) The puncture of infected mosquitoes does not invariably give yellow
fever.

(22) When the bite of infected mosquitoes is ineffective this does not give
immunity against a virulent injection.

(23) In the region of Rio de Janeiro, as in Cuba, no other mosquito than
Stegomyia fasciata is connected with the transmission of yellow fever.

(24) Contact with a yellow-fever patient, with his belongings or his ex-
cretions is incapable of producing yellow fever.

“(25) Aside from the bite of infected Stegomyias, the only known method
of conveying the malady is the injection, into the system of a susceptible subject,
of blood coming from a patient and taken during the first three days of the
malady.

“(26) Yellow fever can assume a dangerous character only in regions in
which Stegomyia fasciata exists.

“(27) The prophylaxis of yellow fever depends entirely upon the measures
taken to prevent Stegomyia fasciata from puncturing the sick man and the
healthy man.

“(28) It is necessary to remember that the period of incubation of yellow
fever may be prolonged to thirteen days.

“(29) Stegomyia fasciata is frequently parasitized by fungi, by yeasts and by
Sporozoa. None of the parasites so far found have any relation to yellow fever.

“(30) We have not been able to find, either in the mosquito or in the blood,
the causative organism of yellow fever.”

Two years later Marchoux and Simond published a brief note in the Comptes
Rendus des Séances de la Société de Biologie (1905), on a possible hereditary
transmission of the virus of yellow fever in the yellow-fever mosquito. This
note, which created a great sensation at the time, and which still suggests a very
important factor in the possibilities connected with Aédes calopus and with
yellow fever, is here given in full. Similar results have never since been ob-
tained, and the observation must be deemed inconclusive to a certain degree
until verified by a series of similar experiments with similar results.

“ Since 1903 our attention has been directed to the fact that, in certain por-

tions of an endemic zone, it is sometimes difficult to find a case of recent date as
the origin of the new cases which appear at the time. No doubt existed that
248 MOSQUITOES OF NORTH AMERICA

such outbreaks were due to the presence of infected Stegomyias, and we were
obliged to admit that one or several of these mosquitoes had been carried in
some way from a distant point where patients existed and from whom they had
taken the virus. It is certain that this happened in a number of cases. Never-
theless we asked ourselves whether, under certain circumstances, eggs from in-
fected Stegomyias, in a locality where there had been an epidemic some months
previously, could not give birth to mosquitoes hereditarily infected.

“ Various experiments were made in 1903 to verify this hypothesis. We got
the eggs of Stegomyia which had punctured sick people in the first stage of the
disease. We raised the larve, and as soon as the perfect insect issued we made it
puncture a human subject.

“These experiments did not give us at that time any positive result. The
subjects who were pierced by such mosquitoes were susceptible to the disease,
for it could be given to them later by injections of fresh virulent serum.

“We began these experiments again in the month of February, 1905. Eggs
coming from a Stegomyia twenty days old, which we had caused to puncture
several of our patients in order to secure an intense infection, were collected and
the larve, issuing the fourth of February, were placed in a jar for rearing.
From the 16th of February the perfect insects began to emerge. These, isolated
in tubes from the time of emergence, were fed with glucose up to the second of
March. At this date, 14 days after the metamorphosis, two of these Stegomyias
punctured subject ‘ A,’ a Portuguese only a few days in Brazil and non-immune.
The subject showed no reaction following these punctures.

“ He was punctured again by one of these two mosquitoes (the second had
died in the interval) on the 10th of March, eight days after the first puncture.
Four days later, the 14th of March, he showed a typical attack, moderately
severe, of yellow fever. The character of the onset, the vomiting, the pains, the
progress of the temperature, the jaundice, the manner of convalescence, per-
mitted no doubt of the nature of the disease. Nevertheless, we tried to confirm
our diagnosis experimentally. After the attack we had this subject punctured
on two occasions by series of infected Stegomyias. He was absolutely immune
to these inoculations, as are all individuals recently immunized by a former
attack. Let us add that he was watched by us from his arrival in Brazil, and
that the conditions did not permit any contamination other than that through
the hereditarily infected mosquito which must have, by its bite, caused the attack
of yellow fever which he showed.

“This experiment seems to indicate that, in the conditions indicated, the
Stegomyia fasciata coming from a mother directly infected by a fever patient
are themselves hereditarily infected. It results from the different experiments
carried out on this subject, that the lapse of time necessary before the hered-
itarily infected mosquito may be capable of emitting the virus with its saliva is
longer than in the case where the virus has been taken directly by the mosquito
from the blood of a yellow-fever patient. This lapse of time was 22 days in our
experiment.

“ Tt results, likewise, from the experiments as well as from the epidemiological
facts, that this hereditary transmission can not be considered common, but rather
as an exceptional occurrence.

“ The mildness of the attack in this case leads one to believe that the passage
of the virus through a generation of Stegomyia is accompanied by a certain
degree of attenuation. It opens a new path towards researches in the direction
of vaccination against yellow fever.

“The knowledge of this method of propagation clears up one of the most
obscure points in the history of yellow-fever—that of the return of certain epi-
demics where no previous case sufficiently recent can be found to explain the
EXPERIMENTS IN TRANSMISSION 249

inoculation of the existing mosquitoes. Finally, the importance of the experi-
ments from the point of view of prophylaxis can not be disregarded.”

This case is so extremely important that more space must be devoted to it.
The year following the first announcement just quoted, fuller details were given
in the Annals of the Pasteur Institute for January, 1906, in which the symptoms
of the infected patient are carefully given, day by day, and the daily tempera-
ture is charted, leaving the case fairly open to the inspection and possible criti-
cism of yellow-fever experts. The investigators consider a light attack of
yellow fever as perfectly proved, and state that the absence of albumen, the
lowering of the temperature after forty-eight hours, and the rapidity of the
convalescence particularly show the mildness of the case. They consider that the
immunity to a subsequent attack, which they tested by later inoculations with
infected mosquitoes, is also strong evidence of the validity of the first attack,
and in fact confirms it rigorously. They call especial attention also to the fact
that the interval between the time of the first infective bite, 4 o’clock in the after-
noon on the 10th of March, and the appearance of the first symptoms of yellow
fever at midday on the 14th of March, being three days and twenty hours, or
ninety-two hours, is exactly the interval most commonly observed in experi-
ments in the transmission of yellow fever by the bite of Aédes calopus. They
point out that in the twenty-six experimental cases followed by positive results
at Havana and in Brazil eighteen cases showed symptoms of the fever in the
course of the fourth day following the bite.

They considered the possibility whether, in spite of their careful watch over
the subject, who as a matter of fact lived with one of them in the laboratory,
some chance circumstance had perhaps exposed him to inoculation other than
the experimental puncture of the hereditarily infected mosquito. But they
think that there was no chance that this could have occurred under the precise
conditions.

In the article just cited the French writers admit that it is impossible to draw
unassailable conclusions from an isolated case. However they elaborate upon
the importance of this discovery as accounting for the return of recently stamped-
out epidemics at a period which may be comparatively short but too long to
permit of its direct carriage by adult mosquitoes infected before the epidemic
was stamped out. They cite the return of the 1889 epidemic at Campinas as a
possible example. Reverting again to the benignity of the case produced by the
hereditarily infected mosquito, they ask if this was not due to an attenuation
of the virus which had passed through the egg and larval stages of the insect.
They state that among their experimental cases bitten by directly infected mos-
quitoes they found a certain proportion which were benign, and concluded that,
aside from individual resistance to the disease, there are conditions as yet un-
known which bring about an increase or an attenuation of the virus in the mos-
quito. They argued further that it is known that in countries where yellow
fever occasionally exists there are false epidemics—an illness known under the
name of inflammatory fever. It differs from yellow fever by the mildness of its
attack and by the absence of mortalities. One of these writers studied in 1882 a
250 MOSQUITOES OF NORTH AMERICA

slight epidemic of this affection among the soldiers in garrison in the island of
Salut in French Guiana. In a space of eight or ten days a third of the effective
force of this little garrison was attacked by the fever, which caused no deaths
and disappeared as suddenly as it came. The writers were struck with the
analogy existing between that outbreak and the case of yellow fever which they
had produced by an hereditarily infected mosquito. This inflammatory fever
is unknown except in countries in which yellow fever is endemic. Its epidemic
appearances have been often preceded or followed by certain and severe cases of
yellow fever. They think that if it shall be shown by future experiments that the
yellow-fever mosquito hereditarily infected is capable only of producing light
cases, it will be important to consider whether the so-called inflammatory fever
does not differ from yellow fever simply by this mode of infection.

The final conclusions of the French commisssion are published in their second
and third Memoirs, issued by the Pasteur Institute of Paris in January and
February, 1906. The conclusions of the second Memoir include the observations
just recorded, but the conclusions as a whole are so important that they may be
stated in detail :

“(1) The transmission of the virus of yellow fever is possible hereditarily in
Stegomyia fasciata. In the case, unique up to the present, in which this has been
observed, the eggs which gave birth to the hereditarily infected individuals of the
first generation had been laid by a mosquito which had been infected a suffi-
ciently long time previously from a yellow-fever patient.

“(2) The infection of Stegomyia fasciata hereditarily does not appear to play
a considerable part in the propagation of yellow fever. It is capable, neverthe-
less, of causing a recurrence of a recently stamped out epidemic, and it is there-
fore very important to take it into consideration in prophylactic organization.

“(3) Itis possible that the passage of the yellow-fever virus from one genera-
tion of the mosquito to another, through the egg, causes the attenuation of the
virus.

(4) The mosquito does not become infected by absorbing either the blood
coming from the hemorrhages common to patients in the second stage of yellow
fever or from the black vomit or from the dejections of the patients. The mos-
quito, even in captivity, absorbs these substances only when it is compelled by
hunger.

“(5) The larve of Stegomyia fasciata reared in water containing fresh bodies
of infected mosquitoes do not contract the infection and the adults which issue
from them are not virulent.

“(6) The infected mosquito kept at a temperature near 20° C. does not
appear to possess the infecting power.

(7) We have not succeeded in infecting mosquitoes from subjects during
the period of incubation of yellow fever.

“(8) The virus of yellow fever can be artificially transmitted from mosquito
to mosquito. We have not succeeded in causing several successive passages of
this kind.

“ (9) This mode of transmission is possible only under laboratory conditions.
Tt does not exist in nature. Healthy adult mosquitoes kept in contact with the
bodies of infected mosquitoes do not contract the infection and are incapable
of transmitting yellow fever.
IMMUNIZATION EXPERIMENTS 251

(10) Experiments in the endeavor to transmit the fever by other mosquitoes
than Stegomyia fasciata have uniformly given negative results.* It is very
probable that the yellow fever virus is adapted to the organization of this single
species to the exclusion of all other culicids.

“Were this not so, a biological phenomenon which is observed with most of
the species, the death of the female after the first egg-laying, would prevent the
virus absorbed by the individuals of these species, after piercing a patient, from
having the time to develop in their bodies in such a way as to render them
infectious.

“(11) Stegomyia fasciata escapes this rule. It is because the female is
capable of laying several successive batches of eggs that she acts as the inter-
mediary host of the fever. If she were to die regularly after her first laying, as
do so many other female Culicide, yellow fever would be unknown.”

Conclusion No. 8, which reads, “ The virus of yellow fever can be artificially
transmitted from mosquito to mosquito,” and the conclusion following it, indi-
cating that this method of transmission is possible only under laboratory con-
ditions, needs further explanation to those not familiar with the original paper.

A number of unsuccessful experiments in the transmission of yellow fever to
monkeys and other animals were tried in the search for an inoculation serum,
and for this purpose they carried 124 infected mosquitoes to France, 57 arriving
in living condition in Paris. They caused the mosquitoes to puncture an orang-
utan and a young chimpanzee, bringing about some elevation of temperature,
but they were unable to determine that this was due to a yellow-fever infection.
After having given periodically abundant injections of virulent human blood to
a horse, and finding difficulties in the way of preparing an active serum which
would not be dangerous, they attempted to cultivate a serum in the mosquito.
They considered that if the germ which causes yellow fever issues from the mos-
quito in the form in which it enters it, it was a legitimate hope that a direct
transmission from one mosquito to another might be secured. They took living
mosquitoes, infected the 12th of February, 1904, pulverized them with glucose
added to a little physiological water. This mixture, rapidly prepared on the 10th
of March, was immediately offered to a certain number of young Aédes calopus
which had fasted for two days. The insects immediately took this nourishment.
Sixteen days later, the 26th of March, three of these mosquitoes bita man. The
same individual was bitten by two more of these mosquitoes on the 28th. The
%th of April the patient felt uneasy ; the 8th he had a chill with pain in the limbs
and in the lumbar region; the thermometer, after having shown 39° the 8th of
April, 39.8° the 9th of April, returned to the normal on the 11th. On the 13th
there was a slight jaundice, with albumen in the urine—in fact, the man had
shown a clear case of yellow fever. The virus had then passed from one mos-
quito to another. The experimenters considered the significance of this experi-
ment as considerable, and believed that nothing would be easier than to procure
the virus in abundance in this way. They continued the work, starting with a

 

* jes experimented with in this way were Culex quinquefasciatus, Aédes scapularis,
Ades ae Lehane, Psorophora posticatus, and Psorophora ciliata.—H., D. & K. ’
+The French investigators still adhered to the belief that most mosquitoes deposit all their
eggs at once. We now know that a large proportion of mosquitoes lay their eggs in incomplete
batches at intervals and that, therefore, the yellow fever mosquito is by no means exceptional in

this respect.—H., D. & K
202 MOSQUITOES OF NORTH AMERICA

single infected mosquito. They crushed it up and fed it to 25 new insects, and
these latter, ground up in their turn, were distributed among 200 others. Of
these, 25 were devoted to a fourth experiment, while the major part of the others
were ground up in physiological water, and the liquid injected, after filtration
through a metallic sieve, into the veins of a kid. The result was negative. Ten
more were allowed to puncture a man, but without result. This lack of success
did not discourage them. They continued the work, and repeated the injections
into the kid, which thus received the extract of about two thousand mosquitoes.
Serum from this kid, tried fifteen days after the last inoculation, was shown to
be inactive. After the second passage the cultures were without doubt sterile,
but unfortunately without the investigators having perceived it, and this is, in
fact, the most serious obstacle to this kind of culture. With each passage it is
necessary to experiment with a man in order to determine the success or non-
success.

Very great praise is due to the French investigators for the care, persistence
and ingenuity of their experimental work. They made important discoveries,
strengthened and helped to fix the belief of the advanced medical profession, and
indicated important lines of work for future research.

THE LAREDO OUTBREAK OF 1903.

The establishment of the fact that yellow fever is transmitted by Aédes calopus
was followed by admirable mosquito extermination work in the city of Havana
by the United States Army authorities. The work was put in charge of Dr. W.
C. Gorgas, of the Army, and quickly produced the most beneficial results. Some
details concerning this work are given later in this volume among the examples
of successful anti-mosquito work.

In 1903 it became evident that yellow fever was epidemic in the town of
Laredo, Texas, and in the city of Nuevo Laredo, Mexico, immediately across
the Rio Grande from Laredo. It was not until the end of September that the
disease was definitely ascertained to be yellow fever, having been reported up to
that time to be dengue; but upon September 25 the public health officials took
charge of the situation and immediately began work based upon anti-mosquito
measures. From September 25 to November 30 there were 1050 cases of yellow
fever, of which 691 were Mexicans and 359 Americans. The number of deaths
was 103, 95 being Mexicans and 8 Americans. The measures adopted and at
once put into effect were practically those which had been instituted in Cuba,
and which consisted in isolation of patients, protection by mosquito bars, fumi-
gation of houses, and the oiling of water receptacles. We mention this Laredo
work as a demonstration additional to those of the mosquito results in Cuba and
Brazil, and as nothing else. Some of the conclusions reached by Surgeon G. M.
Guiteras in his report to Surgeon-General Wyman may be mentioned:

“1. The results obtained through the efforts to combat the yellow fever epi-
demic at Laredo go to demonstrate that the mosquito (Stegomyia fasciata) is

the only means of transmitting yellow fever and that the efforts to destroy the
same were productive of much good, greatly limiting the number of cases.
PUBLICATION 159 PLATE IX

 

1. Crane Lake, Saskatchewan, June, 1907.
Mosquito net for protection of face.

 

2. Destroying the vellow fever Mosquito by fumigation,
YELLOW FEVER OUTBREAK OF 1905 253

“2. The measure taken to prevent the reproduction of the Stegomyia fasciata
or other mosquitoes by oiling all water containers and deposits of stagnant water
were completely successful.

“3. It was demonstrated that to control an epidemic of yellow fever which has
gained considerable headway (and such is the condition usually met with) it is
necessary to have absolute power to enforce sanitary measures until such time
as the people are educated up to the importance of such measures.

“4, Inasmuch as the Stegomyia fasciata can only become infected by biting
the patient during the first three days of the disease it is of vital importance
that cases of fever be reported at the earliest possible moment so that they may
be screened and the mosquito prevented from biting them. Such being the case,
an efficient system of inspection is necessary, especially where there is a tendency
to hide cases.

“5. It is impossible to obtain good results without a mosquito-proof yellow-
fever hospital.

“6. The difficulties of handling an epidemic are increased when such outbreak
occurs on the frontier. Arrangements should, therefore, be entered into by
treaty with contiguous foreign countries, so that under such circumstances
sanitary measures may be carried out jointly by the countries interested for
mutual protection.

“, Insistent and continued efforts should be made through the public press
and other available means, to educate the people within the sphere of influence
of the Stegomyia fasciata, so that they will learn to protect themselves against
the invasion or possible spread of yellow fever in their midst by destroying the
means for the propagation of said mosquito, and by protecting themselves
against the mosquito by efficient screening.

“ Above all, to eradicate the existing fear in the medical profession, as well as
among the laity, of declaring the existence of yellow fever. If the first case pre-
senting the slightest suspicious symptoms of that disease were promptly made
public and the proper modern precautions taken there would be no danger of the
disease spreading. In fact, the public should be taught to acknowledge the ex-
istence of yellow fever in their midst with the same equanimity as in the case
of measles or scarlatina.”

The last of Guiteras’s conclusions was an exceptionally important one. All
through southern Texas that year the existence of yellow fever was systematically
hushed up, and it must be said, to the shame of the medical profession, that
members of that profession were concerned in the blinding of the public eye to
the existence of the disease.

An interesting fact concerning the Laredo outbreak is that at Fort McIntosh,
with a command of 111 officers and men, there were only five cases of yellow
fever, while in the town beside them over one thousand cases occurred. The
force was protected by leather helmets and leggings and mosquito head-nets, and
it was found that the five men who became infected had violated orders by visit-
ing the town without this protection.

THE NEW ORLEANS EPIDEMIC OF 1905.

In 1905 occurred the first opportunity (and let us hope it will be the last) to
demonstrate in the United States on a large scale the efficacy of anti-mosquito
work in the face of an epidemic of yellow fever. The disease was recognized and
acknowledged at a sufficiently early date to permit of much more satisfactory
254 MOSQUITOES OF NORTH AMERICA

results than had been obtained at Laredo, the scale of operations at the same
time being very much greater. The presence of yellow fever in the city of New
Orleans was first recognized about the 12th of July, 1905. The plan of cam-
paign, adopted by the Board of Health under Dr. Quitman Kohnke from the
beginning, was based on the recognition of the mosquito conveyance of the dis-
ease and was directed against Aédes calopus. Dr. Kohnke had, in fact, for some
time previously, been one of the foremost physicians in the South to preach
mosquito destruction. For more than two years he had been doing everything
in his power to secure the screening of the numerous cisterns, and to induce the
city to adopt other necessary measures, but without success. Available funds
to combat the epidemic were rapidly exhausted, and on the 12th of August the
Public Health and Marine-Hospital Service was put in charge of the situation
and provided with means. Dr. J. H. White, of the service, had complete com-
mand. By that time the increase in the new cases and deaths rendered it prac-
tically certain that the disease was as wide-spread as during the terrible epidemic
of 1878. There had been up to that time 142 deaths from a total of 913 cases,
as against 152 deaths from a total of 519 cases in 1878. The work for the rest
of the summer was continued with great energy under Dr. J. H. White, and the
measures were based almost entirely upon a warfare against the yellow-fever
mosquito. The disease began almost immediately to abate, and the result at
the close of the season indicated 460 deaths, as against 4046 in 1878, a virtual
saving of over 3500 lives.

The following table of deaths from yellow fever in New Orleans from 1847 to
1905 points out strikingly the value of this anti-mosquito work:

Comparative table of deaths from yellow fever in New Orleans during various
years.

 

 

 

 

 

Year
Month.
1847, | 1848. | 1853. | 1854. | 1855. | 1858. | 1867. | 1878. | 1905.
MOyes ce ss caucandeieenis slesgeck | eeeins 2" eecscscee| Sn g.e Sea. eM onaancnet [seawall oyna we Veceveetes
PBUGs goa saci HERERO EK oa olin ehceea 4 31 2 5 2 Bl nite d| eew'eas
July......... 14 33 | 1,521 29 882] 132 11 26 35
August -ee{ 965 200 | 5,138 532 | 1,286] 1,140} 255 | 1,025 236
September, .............. 1,100] 467} 982) 1,234 874 | 2,204 | 1,637 | 1,780 107
October sis. csiccs tee sivaceae 198 126] 147] 490 97 | 1,187 | 1,072 | 1,065 59
Nove) Der. «ease dy exe deas 12 20 28 181 19 224 108 147 28
December: csaecayavwewcan 10 |: wewns 4 7 q 15 26 D laseses
Months unknown......... 445 Aii| ed aves hile srarstanei oda cere ltacdeanecer til iatecsiaiess Talargctel| aeeiee
TOGA) «. é.04.0:% case siececoie 2,804 | 872 | 7,848 | 2,425 | 2,670 | 4,854 | 8,107 | 4,046 460

 

 

 

 

 

 

 

 

 

 

The epidemics of 1848, 1854, and 1855 are least comparable with that of 1905
because they immediately succeeded severe epidemics to which were due very
many immunes.

The population of New Orleans by the United States Census was 130,565 in
1850 ; 168,675 in 1860; 191,418 in 1870; 216,090 in 1880, and 287,104 in 1900.
ORGANISM OF YELLOW FEVER 205

Quite as conclusive as the New Orleans experience has been the result of the
work on the Isthmus of Panama. This work is also described in some detail
among the examples of remedial work.

THE DEATHS OF REED, CARROLL, AND LAZEAR.

The deaths of Lazear, Reed and Carroll, following the brilliant results of their
work, are inexpressibly sad. Dr. Lazear was a young man of great ability,
admirably trained, whose work, as Dr. Reed says, was characterized by “ a manly
and fearless devotion to duty such as I have never seen equaled.” He “seemed
absolutely tireless and quite oblivious of self. Filled with an earnest enthusiasm
for the advancement of his profession and for the cause of science, he let no
opportunity pass unimproved. Although the evening might find him dis-
couraged over the difficult problem at hand, with the morning’s return he again
took up the task, full of eagerness and hope.” His death was due to accidental
inoculation, by an infected mosquito, in the course of his researches at Havana.
When the Board resumed its work after his death in November, 1900, and es-
tablished the experiment station at Quemados, they named it in honor of their
comrade, Camp Lazear. Dr. Walter Reed, the inspiring genius of the investi-
gation, died suddenly November 23, 1902, with his health impaired by his
strenuous labors. He had reaped some of the honors following his monumental
work, but by no means all. His name will live as that of one of the great bene-
factors of the human race. Dr. Carroll, although he lived for a few years longer,
died September 16, 1907. At Havana, in 1900, he suffered the first experi-
mentally produced attack of yellow fever and it proved a severe one. His early
death was undoubtedly due to the effect of the disease. He lived just long
enough to see the substantial results which followed the great work with which he
had been so prominently connected. Personally, all three were of the highest
type, and each is mourned by a host of warm friends, as well as by the world
at large.

THE SEARCH FOR THE CAUSATIVE ORGANISM.

The experiments just recorded demonstrate beyond all doubt that the specific
agent of yellow fever inhabits the blood. A most prolonged microscopic search
was made, not only by Reed and Carroll, but by many other investigators, with
fresh and stained preparations of blood, taken at various stages of the disease
and during early convalescence. But all of this search was negative. Further
search was made in the bodies of infected mosquitoes dissected fresh, and also by
means of serial sections of the hardened insect, and no results worthy of men-
tion were obtained. The attention of Reed and Carroll was soon called by Welch
to the important observations of Loeffler and Frosch on the etiology of the foot-
and-mouth disease of cattle. In this disease the lymph, collected from the blebs
present in the mouth and feet of sick cattle, had been diluted and passed several
times through a porcelain filter, with the result that this strained and diluted
lymph injected into calves produced the disease as promptly as with others that
had been injected with the same quantity of unfiltered lymph. The German
authors decided that there were two possible explanations of this result: either
256 MOSQUITOES OF NORTH AMERICA

that the filtered lymph held in solution an extremely active toxin, or that the
causative organism of the disease was so small as to pass through the pores of a
filter through which even the smallest known bacteria could not pass. The
latter explanation was accepted. Reed and Carroll decided to make similar ex-
periments with yellow fever, and Carroll, returning to Havana in August, 1901,
succeeded in carrying out some very interesting experiments; in the course of
these it was shown that the filtered blood serum from a yellow-fever patient
carried the disease to non-immunes. The serum used for the inoculations had
been slowly filtered through a new Berkefeld laboratory filter. As soon as
possible thereafter the filter was sterilized by steam and tested as to its effective-
ness in preventing the passage of bacteria, with the result that it was found to
intercept Staphylococcus. The opinion of Reed and Carroll, after these experi-
ments, coincided with those of Loeffler and Frosch in the case of the foot-and-
mouth disease, and they were inclined to believe that the causative organism of
yellow fever is of extremely minute size (ultra-microscopic).

In 1902 a working party of the Yellow Fever Institute of the U. S. Public
Health and Marine-Hospital Service worked for some time at Vera Cruz,
Mexico, in the effort to find the causative organism of yellow fever. In their
report, published in March, 1903, they describe a protozoan parasite by the name
of Myxococcidium stegomyie which they stated was found with regularity in the
appropriate mosquitoes that had bitten patients affected with yellow fever.
These mosquitoes, after different periods of infection, had been killed, sectioned
and stained. It was the belief of certain members of the party that in this organ-
ism they had found the cause of the disease. This conclusion was opposed by
Carroll in a paper read at the Thirty-first Annual Meeting of the American
Public Health Association, held at Washington, October 26-30, 1903, after ex-
amination of much material. His conclusions were as follows:

“1. The fusiform stage of the so-called Myxococcidium stegomyie of Parker,
Beyer and Pothier (1903), is not connected in any way with the transmission
of yellow fever.

“2. This organism appears to be not a protozoan parasite, but a yeast fungus.
In its fusiform stage, the only form in which it was constantly present, it shows
the characteristic budding, staining affinities and vacuolation or spore formation
of a blastomycete, and it is found with considerable regularity in both male and
female mosquitoes that have purposely been fed on overripe banana to which a
pure culture of a wild yeast had been added in the laboratory.

“3. The organism has not hitherto been found in repeated examinations of
mosquitoes of the genus Stegomyia that have bitten yellow fever patients in the
early stages of the disease, when such insects had been fed only on blood, dry
sugar and water. This statement applies also to mosquitoes that are known to
have reproduced the disease in human beings.”

A second working party, sent out by the Public Health and Marine-Hospital
Service, went to Vera Cruz in April, 1903, and published its report in May, 1904.
In the meantime the French commission had endorsed Carroll’s conclusion.
The conclusions, bearing upon the subject, reached by the second expedition to
Vera Cruz, are as follows:

“ The cause of yellow fever is not known.
CAUSE A PROTOZOAN 257

_ “The Myzxococcidium stegomyie is not an animal parasite. Yeast cells some-
times simulate the coccidia in form and staining reaction.

“The infection of yellow fever is in the blood serum early in the disease.
No abnormal elements that bear a causal relation to the disease can be detected
in the serum or in the corpuscles with the best lenses at our command.

“The infective principle of yellow fever may pass the pores of a Pasteur-
Chamberland B filter.

“ Particles of carbon visible with Zeiss lenses pass through both the Berke-
feld and Pasteur-Chamberland B filters.

“ Because the virus of an infectious disease passes a Berkefeld or Pasteur-
Chamberland B filter it does not necessarily follow that the parasite which
passed the filter is ‘ ultramicroscopic, or that it may not have elsewhere another
phase in its life cycle of large size.

“The filtration of viruses may succeed or fail, depending upon the character
of the filter, the diluting fluid, the pressure, time, temperature, motility of the
particles, and other factors.

“ The period of incubation of yellow fever caused by the bites of infected mos-
quitoes is usually three days, sometimes five days, and in one authentic instance
six days and two hours; but when the disease is transmitted by such artificial
means as the inoculation of blood or blood serum the period of incubation shows
less regularity.

“Yellow fever may be conveyed to a nonimmune by the bite of an infected
Stegomyia fasciata; but the bites of Stegomyia which have previously (over
twelve days) bitten cases of yellow fever do not always convey the disease.

“ Fomites play no part in the transmission of the disease.

“The tertian and estivo-autumnal malarial parasites will not pass the pores
of a Berkefeld filter.”

The causative organism of yellow fever still remains unknown.*

Carroll, of the American commission, in almost the last paper before his
lamented death, and which forms the chapter entitled “Yellow fever” in
volume ii of Osler’s Modern Medicine, summarizes, on page 747, the arguments
which favor the protozoal character of the organism presumed to cause the
disease :

“ Notwithstanding all the efforts that have been put forth in that direction,
the specific organism of yellow fever still awaits recognition. The arguments
opposed to the idea that the invisible causative agent of yellow fever is a bac-
terium are: (1) it has never been recognized nor cultivated; (2) according to
the French Commission the blood of a patient loses its power to infect within
two days if exposed to the air, and within five days if air be excluded; (3) the
absolutely non-contagious and even non-infectious character of the disease under
conditions otherwise favorable but in the absence of the mosquito. The argu-
ments in favor of its being a member of the animal kingdom are: (1) its obliga-
tory parasitic existence in man and the mosquito, alternately ; (2) the necessity
for the lapse of a definite period, two weeks or more after the ingestion of the
blood, before the mosquito becomes capable of infecting; (3) the restriction of
the hosts to a single vertebrate and a single genus of invertebrates which points
to a definite cycle of development ; (4) the rapidity of development of the para-
site within its invertebrate host is governed by conditions of external tempera-

 

* Quite recently, claims of the discovery of the causative organism of yellow fever have been
published by Dr. Harald Seidelin (Zur Aetiologie des gelben Fiebers. Berl. klin. Wochenschr.,
no. 18, pp. 821-823, 1909 ; Protozoon-like bodies in the blood and organs of yellow-fever patients.
Journ. Pathol. & Bacteriol., vol. 15, pp. 282-288, 1911; The etiology of yellow fever. Yell. Fever

Bull., vol. 1, no. 7, pp. 229-258, plate. 1911).
258 MOSQUITOES OF NORTH AMERICA

ture in the same way as the rate of development of the malarial parasite in the
anopheles mosquito.”

The view of Carroll, that the causative organism of yellow fever is a protozoan,
ultra-microscopic in size and with its life-cycle partly in man and partly in the
mosquito, has been generally accepted by students of the disease.

THE YELLOW-FEVER MOSQUITO.
DOMESTICITY OF THE YELLOW-FEVER MOSQUITO.

Aédes calopus is inseparably associated with man in the tropics. It is essen-
tially a town mosquito and it is never found at a great distance from habitations.
It shows a very decided preference for human blood and must have blood for the
development of its eggs. These points were very clearly brought out by Mar-
choux, Salimbeni and Simond, of the French commission to Rio de Janeiro, and
they have since been verified by many observers. Both sexes inhabit houses and
when the requisite conditions obtain the entire life-cycle takes place indoors.
This is the only species of mosquito in which the male is attracted to man.
Finlay’s paper of 1881 shows that he already clearly understood the domestic
character of calopus. Ficalbi, in 1896, noted the domesticity and diurnal habits
of this mosquito, and that it does not bite at night. Goeldi states that in Para
it bites from sunrise until dark. A significant fact is the stealthiness of its
attack, always approaching from behind. It retreats upon the slightest alarm
but does not relinquish its efforts until it has accomplished its purpose. The
ankles and, when one is sitting at a table or desk, the under side of the hands and
wrists are the favorite points of attack. Of further significance is the fact that
it attacks silently while other mosquitoes announce their presence with the
piping or humming note. Doubtless sonifaction has been suppressed in this
species in the evolutionary process of adaptation to man.

On their 1905 journies many notes were made by both Busck and Knab bear-
ing upon the fact that the yellow-fever mosquito has become a strictly domesti-
cated species. The hiding habits of the adult, its general air of familiarity with
man, its habit of approaching from behind instead of from the front, its extreme
wariness, its habit of concealment in garments, working into the pockets and
under the coat lapels and collars and of crawling up under the clothes to bite the
legs rather than the exposed ankles, are all indications of familiarity with the
human species for many generations.

The habit of hiding, which has just been mentioned, seems very characteristic
of this species. It was already noted by Finlay in 1881 and its bearing upon
the dissemination of the species pointed out. In houses they will hide in dark
corners, under picture moldings, behind the heads of old-fashioned bedsteads
and in similar places. They will enter clothes closets and hide in the folds of
garments. From this habit, as Finlay states, they are especially apt to be packed
with clothing into trunks and carried on journeys. They have been known to
emerge alive after some days’ confinement of this character. Just how long
calopus will live under these conditions has not been determined.
FOOD OF AEDES CALOPUS 259

The domesticity of this mosquito will be apparent from the detailed account
of habits which follows. Nearly always it is found in houses or in their im-
mediate vicinity. Durham, at Paré and at Manaos, on the Amazon, found it a
house mosquito. He says of it: “ Never seen out in forest away from houses,
or in isolated huts situated away in forest. Not seen at Santa Anna, some
twenty-five miles north of Para, or Fazenda Natal, in Marajo.”

However, upon a number of occasions it has been found established at a dis-
tance from habitations. The Brazilian observers at Rio de Janeiro have paid
special attention to this question and Peryassti records its occurrence in the
forest at a distance of 500 meters from the nearest habitation. In the vicinity
of Rio de Janeiro both males and females of calopus were found in the woods,
away from houses, at Gavea, Corcovado, Paineiras, Furnas da Tijuca, Sylvestre,
and in some woods near Lagoinha. Once the larve were found in a pool at
Furnas da Tijuca, at a great distance from habitations, and on another occasion
at 100 meters from the Hotel do Sylvestre which is situated in an uninhabited
region. Such occurrences must nevertheless be considered rare, even under the
most favorable circumstances, such as those observed about Rio de Janeiro un-
doubtedly were.

The only other instance known to us in which calopus has been found at a
distance from human habitation, except on trains, ships and other conveyances,
is told by Mr. Herbert S. Barber, of the Bureau of Entomology. On July 30,
1904, while making a trip along the supposed northern boundary of the distribu-
tion of the yellow-fever mosquito, after dinner at Helena, Arkansas, he took a
walk into the wooded hills in the suburbs, a hundred feet above the river. Rather
more than a quarter of a mile after leaving the last house, in a sunny opening
in the woods, he was kneeling down and sifting the earth for small insects, when
a single female of calopus alighted on his hand and pierced his skin. He cap-
tured the specimen. He searched and could find no house within a quarter of a
mile, and there was no indication of any building having existed there before.
He himself is sure that the mosquito was there before he arrived. Could the
mosquito have flown this distance from the nearest house (there was no neigh-
boring breeding-place, so far as Mr. Barber could find)? Mr. Barber thinks
there was no possibility that the insect had come out from the town with him,
although he was perfectly aware of the propensity of this species to hide under
folds of garments, such as coat lapels.

The French investigators state that sleeping rooms are the preferred habitat
of calopus. They determined that this mosquito very rarely attempts to leave a
room and that it does so only when in search of a suitable place to deposit its eggs.

FEEDING HABITS.

The French commission found that both sexes normally frequent human
habitations and that they obtain the necessary food inside the house. The female
sucks blood when it is available, and, as will be shown further on, needs blood to
develop her eggs. In captivity the female has been kept alive a long time on a
diet of honey or other sweet substances. Ficalbi makes the following statement

18
260 MOSQUITOES OF NORTH AMERICA

which has been widely quoted: “A most remarkable peculiarity of this species
is that the male stings as well as the female and sucks the blood, producing a
puncture equally painful with that produced by the female.” It now seems well
established that the male does not suck blood. Taylor in referring to this point
states that “after a daily experience of over two years, with thousands of Steg-
omyia fasciata, we are in a position to state positively that the Havana male of
this species does not bite the human skin.” However it seeks the exposed por-
tions of one’s person, apparently to lap the perspiration, and produces a certain
amount of irritation. The male also feeds upon sugar and upon various liquids,
such as wine, beer or syrup.

Goeldi has observed an apparent connection between the existence of perspira-
tion and the attraction of the yellow-fever mosquito. He says that when one
perspires lightly on the neck, the ears, the face, and the hands calopus is at-
tracted very greatly. He states that the males are also attracted to any exposed
portion of the body covered with perspiration. He thinks that they come to
drink the perspiration, and if they do not actually puncture the skin it is simply
because they are unable to do so. He is inclined to think that their efforts to
perforate the skin produce some irritation.

The French investigators found that a female will bite 24 hours after emer-
gence from the pupa; Peryasst states that both fertilized and virgin females
have been induced to suck blood after 18 hours. Under natural conditions it is
rare that the female has not been fertilized before this time and it appears that
copulation stimulates the desire for blood. Finlay tried to induce females cap-
tured fresh from the pupa to bite, but in trials during two and three days he was
unsuccessful. The French commission determined that, nevertheless, virgin
females will bite. In an experiment with eight virgin females the first one
sucked blood after 54 hours. Finlay already noted that the fertilized females
are very greedy for blood and this observation has been confirmed by others.

Finlay observed that after a meal of blood calopus is very sluggish and flies
with difficulty; it seeks a hiding place where it remains quiescent during the
process of digestion. During this period the female often, for hours at a time,
moves its hind legs in a curious manner and Finlay supposed that during this
operation it anointed its body with a secretion from the anus. If the mosquito
has sucked enough blood for a full meal it will not return to bite for some time
but, on the contrary, will avoid the bare skin, as Finlay thinks, because the
warmth is disagreeable to it. He found that from two to four days were con-
sumed in the process of digestion and that afterwards the female again became
greedy for blood.

Peryasst records a minimum period of 24 hours for the digestion of a blood
meal. Finlay called attention to the important bearing on the transmission
of yellow fever of the fact that calopus normally sucks blood repeatedly. Thus
a female which he kept alive for 31 days sucked blood 12 times. By biting a
number of different individuals the chances of becoming itself infected and of
transmitting the disease are greatly increased. Finlay further thought that the
MODE OF ATTACK 261

higher temperature of persons stricken with fever might be an additional attrac-
tion for the mosquito.

The French commission found that calopus has a decided predilection for
the blood of man. It can, however, subsist upon the blood of any warm-blooded
animal, but it shows a more or less pronounced repugnance for any other warm-
blooded animal than man. Durham states that at Pard he has observed calopus
feeding upon “ dogs, on an agouti, and a bat,” but he does not indicate whether
this was in freedom or with mosquitoes in captivity. Neumann, in his experi-
ments on the transmission of Plasmodium precox to canary birds by means of
calopus, found that this mosquito showed a decided preference for mammalian
blood. In his experiments, conducted under the most favorable conditions,
from a total of 2573 female calopus, he was only able to induce 789 to suck blood
of canaries, or 30.7 per cent. With Culex, on the contrary, 64 per cent of the
females attacked the birds. When the experiment was made with rats the re-
sults were reversed and the calopus attacked at once while the Culex showed
Tepugnance.

Jt appears also that calopus discriminates between races and individuals. This
was already discussed by Finlay in the following manner:

“Finally, should be taken into account the preferences which mosquitoes
manifest towards certain races and individuals; one notes that the least tor-
mented race appears to be the African and the individuals most persecuted by
them are those of northern races who have recently come to the tropical regions
of America. It appears probable that this depends upon the thickness of the
skin and upon the condition of the capillary circulation of the skin; it is to be
assumed that these circumstances will affect the facility with which the female
mosquito can obtain the blood which it needs to complete its life-cycle.”

The French investigators made a number of experiments to show whether
calopus bites indifferently people of different races. They concluded that it
easily bites both the negro and the red-skinned races, but that it has a marked
predilection for the white race. If mosquitoes of the same age and at the same
temperature are placed upon individuals of the black-skinned, red-skinned and
white-skinned races, the white will be bitten most quickly. The red-skin is also
quickly attacked. Towards the negro, calopus shows some repugnance, and
almost never in the course of their observations did it decide to bite immediately,
and often a contact of ten to fifteen minutes was necessary before the proboscis
was inserted. They show also that among the individuals of the white race, this
mosquito has preferences, and attacks with the greatest avidity young, vigorous
individuals of fine skin and good color rather than anemic or aged persons.
When it is hungry, however, the mosquito will bite the first human being it
meets.

The stealthiness of attack has already been mentioned as a peculiarity of the
yellow-fever mosquito. This is brought out in an interesting manner by Parker,
Beyer and Pothier in the results of their investigations at Vera Cruz (Report of
Working Party No. 1, Yellow fever Institute, Bulletin 13, March, 1903) :

“The approach to attack of Stegomyia is extremely insidious, usually ap-
proaching an individual on the shady side and without warning. The perti-
262 MOSQUITOES OF NORTH AMERICA

nacity of this mosquito in returning to its victim after it has been repeatedly
driven off is almost characteristic. It has been noted repeatedly by us that
females escaping while being transferred from one jar to another would almost
unfailingly return after a few minutes and attempt to secure food from one of
us. On one occasion a marked female was driven off five times during one fore-
noon ; once she remained away nearly an hour, when her intended victim becom-
ing tired of further timekeeping, finally recaptured her. Having satisfied its
ss el for food it gives vent to a triumphant note and goes in search of a resting
place.

The French investigators determined that calopus would only drink blood that
it could itself extract from the body. When females were placed upon a patient
who was wet with a hemorrhage from the mouth they refused to feed upon this
blood and in case the mosquito was hungry it sought a place that was not daubed
with blood and fed by piercing the skin. When given the choice of cold blood
and sweet substances they preferred the latter. Otto and Neumann were able to
feed female calopus on a mixture of blood and salt solution ; the French investi-
gators think that this must have been done under very favorable conditions and
that it does not invalidate their own observations.

TIME OF ACTIVITY.

The yellow-fever mosquito in the West Indies is known often as “ the day
mosquito.” It is usually active and bites only during the daytime, although
where there is a light in the room it may also bite at night. Finlay, in his paper
of 1881, already called attention to the strictly diurnal habits of this species and
contrasted it with the exclusively nocturnal habits of the other house mosquito
of Havana, Culex quinquefasciatus. He thought that there must be a constitu-
tional difference in the two mosquitoes which accounted for the different habits
and this he concluded to be the greater resistance of calopus to heat. He placed
females of the two species in glass tubes and exposed them at midday to the
direct rays of the sun under identical conditions, the thermometer marking
42.25° centigrade, the relative humidity 31.75. The Culex died after five
minutes while the calopus remained unharmed after 15 minutes and continued
alive in its tube through a further 24 hours.

Working Party No. 1 of the U.S. Public Health and Marine-Hospital Service,
at Vera Cruz in 1902, found that the greatest activity of this mosquito is during
the daytime. They also observed them feeding upon members of the party at
night by artificial light. They found them to be especially voracious early in the
morning, about sunrise, and again late in the afternoon. Durham, in his studics
at Paré, Brazil, was also struck with the diurnal habits of calopus and calls it
“ solely a day gnat.”

“Tt is on the wing and will bite shortly after sunrise (about six a. m.) ; again,
a few have been observed biting about eight to nine a. m., after which there is a
pause till about eleven a. m., when again a few may be feeding. The time of
chief activity is in the middle of the day, from about twelve to two p. m., they
then bite freely, and are seen to copulate on the wing in numbers ; another pause

follows, though there may be a few about, but they do not cause trouble when
one is sitting at the microscope until about half-past three till about five p. m.
CALOPUS A DIURNAL MOSQUITO 263

After dusk or dark I have only once met with a specimen ; this was a male, feed-
ing 1n a sugar-basin rather before seven p.m. These statements are derived from
observations whilst working in the laboratory, and during a residence for a week
in the house of a gentleman, whose garden was liberally supplied with ant-guards
(perforated troughs filled with water, for preventing the access of the de-
structive ‘ Satiba ’ to the plants), each of which was full of developing larve and
pupe. Sitting in the verandah of this house it was easy to catch fifty to eighty
specimens without moving from one’s chair, in the early hours of the afternoon,
yet after sundown, not a single individual was met with.”

Dutton, in the malaria expedition to the Gambia, observed calopus and found
it strictly diurnal.

“The observation of Durham and others with regard to Stegomyia fasciata
was fully confirmed at Bathurst ; these mosquitoes only bite during the day, more
especially in the early part of the afternoon. None of this species were collected
in mosquito nets during the night.”

It has been the experience of one of the writers (Howard), sleeping in hotels
in the Southern States where the mosquito canopies were faulty, that when other
species of mosquitoes were not in the room he was undisturbed until the room
was lighted by the rising sun; then Aédes calopus began to bite furiously. Ac-
cording to E. G. Hinds, at Victoria, Texas, they seem most active from eight to
ten in the morning and from four to six in the afternoon, and are very active
just before a storm.

Carter states that calopus has not been found to feed in the dark nor in a
strong light, and that its feeding seems to depend more on the degree of light
than on the time of day. He says that if the place be fairly light, it approaches
its victim on the shadow side, thus especially attacking the ankles under a
writing table, or the hands under the head during a siesta. It does not bite out
of doors in ordinary bright daylight. Knowledge of these points is of much
practical value. Carter points out that by these habits is explained the com-
parative safety of daylight communication with towns infected with yellow
fever ; that is to say, entering a town only after ten a. m. and leaving by four p. m.
under pledge to go in only on sunny days and to enter no residence. The danger
of staying all night, he points out, is really the danger of the late afternoon,
early evening and morning hours, spent, of course, in houses.

Veazie, of New Orleans, in an early paper (New Orleans Medical and Surgical
Journal, 1901) says that this mosquito “ usually flies and bites in the daytime;
if a light is burning at night you will find an occasional one . . . [It] is quite
cunning in selecting the dark side of a person away from the light, and espe-
cially likes persons in dark clothing; old people, as they usually sit quiet, are
greatly annoyed in the daytime by them.” Taylor, of Havana, says of calopus,
“Tf hungry, it will bite freely at any hour of the day or night.”

Charles S. Banks has observed Aédes calopus in the Philippines and says:
“It is altogether a day flier, individuals being seen after dark only on the very
rarest occasions.”

Goeldi, originally of the opinion that calopus does not bite during the night,
was obliged after cumulative instances to admit that it may do so. Writing
264 MOSQUITOES OF NORTH AMERICA

between eight and eleven o’clock at night, in a room in his house or in his office
atthe Museum at Parad, with electric light, the windows open, he caught mosqui-
toes that settled upon his hands, biting him. Generally those which came at these
hours, certainly those from outside through the windows, were other species,
but from time to time, each time causing him a certain surprise, there appeared
also a female of calopus. In Rio de Janeiro he also noticed nocturnal bites by
this species, in a library on the lower floor of a house illuminated by gas, at about
the same hours. He noted that the room was papered with dark paper, and he
had always noticed that during the day he was more persecuted by calopus in
that room than in any other. He soon learned that the deep moldings of the
furniture were the chosen hiding places for a large number of calopus. He also
ascertained that females in captivity could easily be induced to bite at night.
He asserts, however, that the yellow-fever mosquito is a diurnal species, but
admits that it may happen that hunger drives some females, who during the day
have not succeeded in obtaining their meal of blood, to prolong their hunt to
unusual hours, especially when guided by a bright light in the room. Biting at
night is therefore an exception, and they bite only in the presence of artificial
light.

The French commission (Annales de l’Institut Pasteur, vol. 17, 1903, p. 691)
assert that Aédes calopus is essentially a nocturnal mosquito. According to
their deductions calopus will only bite in the daytime within the first few days
after leaving the pupa, and then only when driven by hunger. They maintain
that when the female has reached a certain age, at the most two weeks, it will
under no circumstances bite in the daytime. They say that the belief of other
authors, that this mosquito is diurnal and hardly ever bites at night, is an error
which must be destroyed. Still stronger than this categorical statement is the
third of their conclusions (1. ¢., p. 705), where, conceiriug the transmission of
yellow fever by calopus, they say : “ Que cette transmission n’a pas lieu en plein
jour pendant que le soleil est sur Vhorizon.” * This expression is preceded
by another, equally dogmatic: “ dans la nature la transmission s’effectue ordi-
nairement la nuit. Peut-étre méme cette régle est-elle absolue.” +

In these assertions the French commission have made a complete inversion of
values ; their “ rule ” is certainly the exception. The conclusions of the French
investigators are based upon insufficient and faulty data, as will be shown in the
following. Furthermore, it appears that they were influenced in formulating
their conclusions by the often repeated assertion that, at Rio de Janciro, persons
who visited the yellow-fever zone in the daytime only, remained free from
infection.

The assertions of the French investigators were discussed and fairly refuted
by Dr. Ivo Bandi, of Sao Paulo, immediately after their publication. Neverthe-
less, they have been widely accepted and in view of their great importance in
connection with yellow fever we are under the necessity of thoroughly analyzing
the French observations.

 

‘ fae That this transmission does not occur during the daytime while the sun is above the
horizon.”

+“ Under natural conditions transmission ordinarily occurs at night. It may be that this
rule {ts absolute.”
EXPERIMENTS ON BITING HABITS 265

The conclusions of the commission rest, at least in the main, upon the observa-
tions of one of the members who was detailed for this work. A room was pre-
pared to serve as both laboratory and sleeping room, arrangements made to pre-
vent the escape of mosquitoes, and here the observations were to be made under
the most natural conditions possible. “Lun de nous s’est astreint 4 habiter
cette piéce pendant la journée et la nuit, afin d’observer les Stegomyia fasciata
qui, soit isolément, soit par séries, y ont été introduits au cours des saisons
chaudes de 1904 et 1905, dans un but expérimental.” * (Ann. Inst. Pasteur,
vol. 20, 1906, p. 105.) We are further informed that the observer absented
himself from the room at meal-time only and that the observations were con-
tinued day and night, the first time during 18 days, the second time during 28
days. Clearly a continuous effort for such periods is beyond the power of the
ordinary man and the excessive fatigue resulting from such an attempt must,
as we shall see, seriously affect the character of the observations.

Seven separate experiments were made. Five of these were with series of from
6 to 8 mosquitoes and two of them were with single mosquitoes. Thus 42 is the
maximum that we can assume of mosquitoes used in these experiments. Five
of these experiments were cut short before the sixteenth day by the accidental
death of the mosquitoes. In the two remaining experiments, which were carried
beyond the sixteenth day, nine mosquitoes were employed. The results of these
two experiments are given in detail; of the others we are briefly told that the
results were similar, as far as the biting habits are concerned. “ Nous rap-
porterons en détail les deux derniéres comme étant les plus complétes.” (We
report in detail the two last as being the most complete.)

EXPERIENCE I.

Un lot de 8 Stegomyia fasciata femelles, nées et élevées au laboratoire, sont
mises en liberté dans la chambre 4 expérience, 24 heures aprés leur passage a
Vétat parfait. Pendant ces 24 heures elles sont restées enfermées en compagnie
de males et ont été vraisemblablement fécondées.

le jour: piqires nombreuses entre 9 heures du matin et 5 heures du soir.

2e jour: piqfires (1 ou 2 seulement) entre 3 et 6 heures du matin, a l’ob-
scurité. Piqtires nombreuses de 10 4 11 heures du matin.

3e jour: pigtires entre 1 et 5 heures du matin. ;

4e jour: piqdres entre 9 et 10 heures du matin. Piqfres entre 4 et 5 heures
du soir.

Se jour: piqtires 45 heures du soir. Piqtires 4 10 heures et $ du soir.

6e jour: piqtres entre minuit et 5 heures du matin. Une piqfre a 3 heures
du soir.

Ye jour: piqfires 4 5 heures 3 dusoir. Piqfires a 10 heures du soir.

8e jour: piqdres 4 2 heures du matin, a l’obscurité.

9e et 10e jour: pendant ces 2 jours, on a laissé les moustiques seuls dans la

re 4 expérience.
ae jour: inher entre 6 heures et 6 heures 4 du soir. Piqfires entre 10 et

11 heures du soir.
*“ One of us was obliged to inhabit this room day and night in order to observe Stegomyia

iata which, sometimes singly, sometimes in series, were introduced, during the hot seasons
eee OL and 1905, for experimental purposes.
266 MOSQUITOES OF NORTH AMERICA

12e jour: pas de piqtires.

13e jour: piqfires entre 10 et 11 heures du soir.

14e jour: piqfres entre 4 et 5 heures du matin.

15e jour: pas de piqfires.

16e jour: piqires dans la nuit, entre 1 et 6 heures du matin. II parait ne
subsister que 2 moustiques du lot mis en expérience.

1%e jour: piqtires 4 9 heures 4 du soir.

18e jour: ona vuce jour-la un seul moustique voler dans la piéce sans essayer
de piquer. Depuis ce moment, aucun des moustiques n’a été revu.

EXPeErIENceE II.

Un Stegomyia fasciata femelle a été laissé en liberté dans la chambre 4 ex-
périences le lendemain de son passage 4 l’état parfait. En méme temps, on a
introduit dans la chambre 2 St. f. males.

le jour: piqfires 4 2 heures 4 du soir.

2e jour: piqfres le matin entre 4 et 6 heures.

3e jour: pas de piqtire.

4e jour: pas de piqfire.

5e jour: pas de piqfire.

6e jour: piqfire le matin entre 1 et 6 heures, & Yobscurité. Pigqfire le soir
411 heures 4, a la lumiére.

Ye jour: pas de piqfire.

8e jour: pas de piqfire.

9e jour: pas de piqire.

10e jour: piqdres le matin entre 1 et 2 heures, 4 Vobscurité.

lle jour: pas de piqire.

12e jour: piqdre dans la nuit entre 2 et 5 heures du matin, 4 V’obscurité.

13e jour: pas de piqire.

14e jour: piqfire le matin, entre 4 et 6 heures.

15e jour: pas de piqtire.

16e jour: piqire entre 5 et 6 heures du matin.

1%e jour: piqfre 4 1 heure du matin.

18e jour: piqfre entre minuit et 6 heures du matin.

19e jour: pas de piqifire.

20e jour: pas de piqfire.

21e jour: pas de piqfire.

22e jour: piqire 4 11 heures du soir, a la lumiére.

23e jour: pas de piqfire.

24e jour: piqire 4 10 heures du soir, a la lumiére.

25e jour: pas de piqfire.

26e@ jour: pas de piqtire.

2%e jour: piqire dans la nuit, entre minuit et 6 heures du matin.

28e jour: pas de piqfire.

Le moustique a été vu le 28e jour pour le derniére fois.

 

These two experiments were begun with nine mosquitoes. In Experiment No.
I we find this statement:

“16th day: bites during the night, between one and six o’clock in the morn-
ing. It appears that there still exist two of the mosquitoes employed in the ex-
periment.” It is thus clear that the investigator, beyond the sixteenth day,
worked wih a maximum of three female Aédes calopus. Furthermore, soon
after, in experiment no. 1, we read: “18th day: one could see on this day but
a single mosquito flying in the room without attempting to bite. After this
event not one of the mosquitoes was seen.”
HABITS AND YELLOW FEVER CONTROL 267

Accordingly, from the eighteenth to the twenty-eighth day the observer draws
his conclusions from a single mosquito.

It appears necessary to deal with this subject in detail, for it involves questions
of methods of prophylaxis of yellow fever. Wrong deductions, based upon
inconclusive experiments, not alone because of the few mosquitoes employed but
also on account of the faultiness of the experiments themselves, can produce
the most serious consequences. The absence of accuracy in indicating the exact
time of biting, in the above experiments, is most regrettable and invalidates
them. This becomes at once apparent from the following extracts: Experi-
ment I. “2d day: bites (1 or 2 only) between 3 and 6 o’clock in the morning,
in darkness.” “3d day: bites between 1 and 5 o’clock in the morning.” “ 6th
day: bites between midnight and 5 o’clock in the morning.” “16th day: bites
in the night, between 1 and 6 o’clock in the morning.” Experiment II. “ 6th
day: bite in the morning between 1 and 6 o’clock, in darkness.” “12th day:
bite at night between 2 and 5 o’clock in the morning, in darkness.” “18th day:
bite between midnight and 6 o’clock in the morning.” “27th day: bite in the
night, between midnight and 6 o’clock in the morning.”

In the second experiment the mosquito bit twelve times, but, as the experi-
menter wishes us to believe that Aédes calopus becomes nocturnal after the sixth
to eighth day, we need consider only the bites from the sixth day on. In this
time the mosquito fed ten times. Five of these bites are indefinitely placed
between midnight and 5 or 6 o’clock in the morning; in other words the in-
vestigator was asleep during those hours. In the summer, at Rio de Janeiro, it
is already daylight at 5 o’clock, and from what we know of the habits of calopus
we do not hesitate in asserting that these bites were inflicted at daybreak. This
leaves five credibly nocturnal bites and four of these admittedly took place with
artificial light. Viewed in this manner the experiments may be said to be in
accordance with the general impression of the habits of calopus.

Goeldi devotes a special chapter to this subject and hotly attacks the assertions
of the French commission. “ How can the most illustrious doctors of the French
medical commission of the Institute Pasteur in Paris wish to prove, through
their faith in their full scientific responsibility, that these Stegomyias in Rio de
Janeiro ‘ont pique pendant la nuit, when here in Para, we, conscious of the
same full responsibility, in view of our positive assertions for years, must declare
the nocturnal bite as an exception?” The idea that calopus should change its
habits after the first blood meal Goeldi characterizes as an absurdity. All the
responsible investigators who have worked with mosquitoes in recent years dis-
agree with the point of view of the French investigators.

We must insist on this point on account of the danger which the French
doctrine carries with it. It may lead those entrusted with yellow-fever prophy-
laxis to abandon the safe methods and place their whole reliance upon protection

against nocturnal bites.*

 

* The Public Health and Marine Hospital Service of the United States has published quar-
antine regulations, for fruit vessels visiting ports at which yellow fever exists, which appear to
reflect the dogma of the French commission, These regulations were first published as
Circular No. 27, Bureau of P. H. and M. H. S. in 1907, but they have been recently newly
promulgated (Public Health Report, Washington, May 6, 1910, vol. 25, no. 18, pp. 604-607) and
given still wider publicity through the Journal of Tropical Medicine and Hygiene (August 15,
268 MOSQUITOES OF NORTH AMERICA

Simond, Aubert and Noe, in their work on the epidemic of yellow fever in
Martinique in 1908, carried away by this idea, insinuate at frequent intervals
that the transmission of yellow fever takes place only at night. At a certain
point, where they discuss the abundance of calopus during the hot months, they
formulate this doctrine as follows: “C’est en se basant sur cette considération
que la mission estiina dangereux, au mois de janvier, le retour des fonctionnaires
européens dans la ville, 4 moins qu’ils ne fussent astreints 4 se protéger la nuit
d’une maniére efficace contre les piqiires de Stégomyias.” * This is a complete
inversion of biological facts. Aédes calopus is a diurnal mosquito and nocturnal
bites, if they occur in darkness at all, are certainly rare exceptions. The erro-
neousness of the views of the French investigators is clearly brought out in their
remarks on the copulation of calopus. “ Deux fois seulement nous avons eu
Poccasion d’observer V’accouplement: il a lieu presque toujours dans la nuit et
& Pobscurité, d’ot la rareté des observations de ce genre.” {| The testimony of
many good observers is that where calopus is abundant copulation can be fre-
quently observed in the daytime. Goeldi, for example, says: “ teml-a visto mil-
hares de vezes e a vémos todos os dias” (“ we have seen it thousands of times
and we see it every day ”’).

 

1910, vol. 13, p. 253). Under “ Regulations to be enforced at foreign ports infected with
yellow fever ’’ we read the following :

“The vessel shall not lie where her crew will be exposed to the danger of ccntracting yellow
fever, and at ports where the vessels lie at wharves the vessel must be moved into the stream
or at least 200 meters from the wharf before sunset, and not returned to the wharf before
sunrise the following day..... "

It was difficult to believe that an American medical department which had been in close touch
with the work of our Army surgeons in Cuba, and afterwards conducted investigations on its
own account which were entirely confirmatory, should accept the French contention that Aédes
calopus bites only at night. It was therefore decided to make inquiry of the head of the
Public Health and Marine Hospital Service and in reply we received the following letter:

Treasury Department, Washington, January 26, 1911.
Dr. L. O. Howarp,

Chief of the Bureau of Entomology,
Department of Agriculture,
Washington, D. C.
My dear Dr. Howard:

I have been unable before this time to answer your letters of January 14 and 16, owing to
the extreme pressure of official business.

In regard to the activity at night of the yellow fever mosquito, and the idea as to this
activity, conveyed by the phraseology of paragraph 9 of the foreign fruit regulations, I have to
say that it is necessary for quarantine administrative reasons that some measure be devised to
hold on board between the hours of sunset and sunrise, the crews of vessels which are lying
in ports infected with yellow fever. In the day time the crew is under control while the vessel
is alongside the wharf. If the vessel should be allowed to remain at the wharf at night
the sailor man would be free to visit such dangerous surroundings as lighted music halls,
saloons, and other resorts, but removed to mid-stream, between the hours of sunset aud sunrise,
he cannot convenicntly reach such points. It is impossible to control the mosquito problem in
any foreign port, and therefore the only recourse is to attempt to control the man.

In regard to the activity of the mosquito at night, for the quarantins purpose above outlined,
I have to say ihrt in tke report dated May, 1904, of the Yellow Fever Working Perty, Part 2 of
the Yellow Fever Institute the statement is made (on page 100) in their summary and con-
clusions thet “ Stegomyia fasciata is a domestic insect. It is most active during the day but
will bite at night under artificial light.” In another part of this report it is stated that the
working party noticed that these mosquitoes were especially voiacicus in the morning about
sunrise. An officer of the service who has bad large experience in localities infected with yellow
fever, and especially in the work of eradicating mosquiroes, siates (hat the yellow fever mosquito
is very active during the twilight.

As a general rule, the majority of sallors on shore liberty will spend the greater part of their
time in presumably well lighted rooms, and if their shore liberty should st-1t at sunset and end
at sunrise, which times are specified in paragraph 9 of the fruit rezuletions, as the time when
shore liberty should be denied, said sailors would. in addition to the time above stated, be
ashore during twilight and sunrise, the times during which the mcsquito ts active without
artificiel light. In other words paragraph 9 of the fruit regulations does not conflict with the
opinions that the stegomyia is inactive in the darkness.

Respectfully, Water WYMAN,
Surgeon-General.

*““The mission bases itself upon this consideration when it judges it dangerous, in the
month of January, for the Huropean offictals to return to the town, at least if they are not com-
pelled to protect themselves at night in an efficient manner against the bites of the Stegompias.”

+ “ Twice only we have had occasion to observe copulation : tt occurs nearly always at night
and tn darkness, hence the rarity of observations of this character.”
CASE OF PETROPOLIS 269

Furthermore the French commission admit that in capturing mosquitoes that
came to bite in the daytime they obtained “un nombre trés considérable” (a
great number) of Aédes calopus. However they try to demonstrate, in accord-
ance with their contention, that these female calopus coming to bite in the day-
time were all individuals but a few days old. They adopt as a criterion of age
the condition of the vestiture and state that it is rare that a calopus more than
15 days old is not much denuded. In fact, under normal conditions, calopus
frequently retains its vestiture a long time. Denudation depends upon circum-
sances in the insect’s life and we can not accept it as a criterion of age.

We have already referred to the case of Petropolis, the inhabitants of which
were said to escape yellow fever in their diurnal visits to Rio de Janeiro. It may
almost be said that the French commissicn obliged the mosquitoes to respect the
itinerary of the boats to Petropolis and abstain from the molestation of the
passengers between their arrival at 9 a. m. and their departure at 4 p.m. We
see the case of Petropolis in an entirely different light. There have been no
epidemics of yellow fever at Petropolis for the simple reason that the average
night temperature is unfavorable to the development of calopus, as the French
commission themselves have shown. On this account Petropolis has been a
health resort of the wealthy, native and foreign, during the hot months.

As to the apparent impunity with which the inhabitants of Petropolis could
visit Rio de Janeiro during yellow-fever epidemics, this was probably due to a
variety of circumstances, not evident, but acting together. It will be safe to say
that most of the inhabitants of Petropolis who spent the business hours at Rio,
whether natives or foreigners, had previously lived elsewhere in Brazil. In the
course of such residence they could not have failed to have had yellow fever and
thus acquired immunity. On the other hand a large proportion of the employees
of the business houses at Rio were non-immune foreigners who were obliged to
live in the city for pecuniary reasons. It was among these that yellow fever was
most in evidence. With the immunes, as the French commission have shown,
immunity is strengthened and prolonged by the bites of infected mosquitoes and
there is no reason to doubt that this process was in operation with the business
men from Petropolis. That those who spent a single night in Rio became in-
fected was not the rule. The notoriety of such cases is to be explained by the
circumstance that the person attacked was generally a member of the foreign
diplomatic service. Customarily the diplomatic corps did not leave Petropolis
during the months of yellow-fever epidemic; if, by chance, one of them was
obliged to visit Rio and remain over a single night he probably became infected
in the early morning when calopus is most aggressive.

The fact seems to be well established that non-immunes from Petropolis, when
visiting Rio de Janeiro in the daytime, escaped infection. This is easily ex-
plainable in that most of the mosquitoes would already have obtained their meal
of blood before the arrival of the visitors from Petropolis, having had fully five
hours of daylight to accomplish their purpose. Such mosquitoes as would bite
later in the day would be mostly fresh individuals that had not obtained their
first meal and were therefore harmless. The members of the second American
270 MOSQUITOES OF NORTH AMERICA

commission to Vera Cruz, without mentioning the case of Petropolis, make some
remarks which are significant in this connection. “ We have noticed on several
occasions that they [4 édes calopus] are especially voracious early in the morning,
about sunrise. On several occasions a number of non-infected insects were let
loose in the laboratory and we observed that upon rising at sunrise they attacked
us viciously. It may be noted that this fact apparently explains the danger to
persons sleeping in an infected house and the comparative freedom from danger
in daylight communication with an infected town.” (Yellow Fever Institute,
Bull. 14, p. 92.)

LENGTH OF LIFE OF IMAGO.

In the course of laboratory experiments, it has been necessary for medical ex-
perimenters to keep the females of calopus, alive for a certain length of time and
they have been tried with different foods, just as were the females of Anopheles
at an earlier date. They have been fed upon bananas and upon other fruit, upon
honey, and upon molasses, and in this way have been kept alive for long periods.

The French investigators found that it was easy to keep calopus alive for two
months; however, beyond the fortieth day the mortality was considerable, re-
gardless of the method of feeding employed. This mortality was greater among
the males than among the females. Among the females kept in confinement
those that lived longest reached the age of 89, 90, 93, 97, 105 and 106 days.
These females had been first allowed to bite a person and were afterwards fed
with honey. They point out that calopus will die very quickly in a dry atmos-
phere. Guiteras, at Las Animas Hospital, kept five infected adults alive for 101
days, and one for 154 days. Goeldi has kept a female alive 102 days, feeding her
with blood and obtaining several deposits of eggs. He believes that the female
will live longer if fed only upon sweet substances. Theobald kept specimens
reared from the larva alive without food for two months.

The male is much shorter lived than the female. The French commission did
not succeed in keeping males alive more than 50 days. Goeldi has kept the
males alive, feeding them upon honey, for periods of from 28 to 72 days, the
longest lived one escaping at the end of 72 days. Undoubtedly life was prolonged
in these cases beyond the normal span by withholding the opportunity for the
male to perform its natural function, the fertilization of the female.

This brings us to the important question as to how long an infected yellow-
fever mosquito may be capable of conveying the disease. This point has not yet
been accurately determined. Reed and Carroll reported cases of yellow fever
caused by the bites of this mosquito at intervals varying from 12 to 57 days
after infection ; they are dangerous after the twelfth day, and thus for at least
45 days. Another insect under their examination lived until 71 days after
biting a yellow-fever patient, the dangerous interval in this case being 59 days
or over eight weeks.

Reed and Carroll dismiss the fear that the infected insects are likely to be
carried in boxes of clothing or trunks, as groundless, since their observations
indicate that when mosquitoes are deprived of moisture they die within a few
AEDES CALOPUS AND TEMPERATURE 271

days and that even when allowed to suck blood they will still die in a few days
if deprived of water.

INFLUENCE OF TEMPERATURE.

The French investigators pointed out that one of the most striking character-
istics of calopus is its extreme sensibility to differences in temperature and this
has been confirmed by many observations. They were impressed by the great
activity which the insect showed when the thermometer ranged in the vicinity
of 28° Centigrade (82° Fahrenheit), the temperature at which it displayed the
greatest energy. In contrast with this was the markedly reduced activity when
the temperature rose or fell a few degrees above or below that point. Beyond
39° C. (102° F.) the heat is fatal to it. If the thermometer goes below 15° or
16° C. (59° or 61° F.) it becomes sluggish and will not feed. At 12° to 14° C.
(54° to 57° F.) it becomes torpid, flies with difficulty and no longer stands
firmly on its legs. At temperatures of from 14° to 18° C. (57° to 64° F.)
calopus not only does not bite in freedom but refuses to bite when put in a glass:
tube and placed in contact with the skin. Only when the temperature inside the
tube is raised sufficiently by the heat of the hand does the mosquito bite. Ata
temperature of 14° C. twelve mosquitoes in tubes were placed in contact with
the arm and kept there for 15 minutes without showing any willingness to bite.
At 17° C. the result was the same. At 18° C. nine of these same mosquitoes bit,
one after five minutes, the remainder after seven and eight minutes. These in-
vestigators do not believe that in nature calopus will bite below 17° C.; they
found that it would bite readily between 22° and 25° C. (72° and 77° F.) but
that the temperature which suits it best is between 27° and 30° C. (81°-86°
F.). Reed and Carroll made some interesting observations on the effect of tem-
perature on biting with the yellow-fever mosquito. They may be quoted as
follows :

“ As regards the effect of temperature on the stinging of stegomyia fasciata,
the results of a number of observations made by us show that this mosquito will
bite at temperatures of 62° F. and above. At temperatures below this point, we
have not, as yet, succeeded in inducing even very hungry females to suck blood.
We may, therefore, say that observations thus far made appear to show that
stegomyia fasciata, while not breeding at temperatures below 68° F., will still
bite at a temperature as low as 62° F., but probably not at lower temperatures.

“Tf this insect is concerned in the propagation of yellow fever, it is now quite
apparent why an epidemic of this disease should fall to a low ebb in the city of
New Orleans during the month of November, with a mean temperature of
61.8° F., and practically cease in December, with a mean temperature of 55.3°
F. Acareful study of the charts herewith submitted, showing the monthly mean
temperatures of the cities of Havana and New Orleans and Havana and Rio de
Janeiro, together with the relative monthly mortality from yellow fever in these
cities, will prove of interest, we think, as showing better than laboratory ob-
servations the general effect of temperature upon the breeding and biting of
stegomyia fasciata. In the light of recent researches, we can now understand
that while yellow fever can, and does, prevail during the entire year in Havana
and Rio de Janeiro—although at a comparatively low ebb during the winter
months—it cannot propagate itself in New Orleans from December to May.”
272 MOSQUITOES OF NORTH AMERICA

Otto and Neumann have made experiments on the resistance of the adult
Aédes calopus to cold. These were made in Germany, with imagos bred in con-
finement. When calopus were placed outside the window with the temperature
at the freezing point they died very quickly. When exposed to a temperature of
4° ©. (39° F.) for one hour and then returned to the warm room they could
still be revived, but longer exposure killed them. However, calopus can survive
cool temperatures for a considerable time. Carter states that “ Guiteras placed
thirty-three mosquitoes in an ice-box at 46.5° to 50° F., without food or water;
three of them survived to the eighty-seventh day, when they were eaten by ants.”
Otto and Neumann, in a similar experiment, with a constant temperature of
7° to 8° C. (45.5°-48° F.) kept calopus alive to the eighty-second day. In this
experiment they employed 25 male and 25 female mosquitoes; they were fed
with sugar, honey and water, and part of the females had sucked blood. Ina
short time the insects became stiff and only moved very slowly; they nearly
always sat on the bottom of the jar, es if they could no longer retain their hold
on the glass sides. After three days fcur of the males died and none of the re-
maining 21 males survived the fifteenth day. On the contrary but very few of
the females died in the first two weeks and after 30 days about half of them still
remained alive; on the fiftieth day three were alive; after 61 days but two, and
after 71 days only one remained.

THE BITING OF CADAVERS.

An interesting observation made by Rosenau, Francis and Goldberger (Report
of Working Party No. 2) indicates that the yellow-fever mosquito may bite a
cadaver, and, if on a dependent portion, can draw blood. The two observations
made on this point were as follows:

“ Narciso Nadal (Case XX). A number of Stegomyie were applied twelve
hours after death, only one of which apparently obtained blood.

“Trinidad Martinez (Case XXII). A number of female Stegomyie fasciate
were applied one-half hour after death, and three insects succeeded in feeding
with blood.”

These authors point out that, as the work of the French commission has shown
that the blood of yellow-fever patients is not infective after the third day, the
danger of the carriage of infection by mosquitoes which have fed upon cadavers
must be very remote. The only chance of infection from such a source would
be in the case of the death of the patient within the first three days.

DISTANCE OF FLIGHT.

The distance of flight of the adult is a very important question. Calopus
seems to be a strong flier, as is evidenced by a series of experiments carried on
by Goeldi on the effect of a strong current of wind between two open windows,
or by air currents produced by a mechanical ventilator. He found that calopus
pays absolutely no attention to such currents, continuing its evolutions about
him and stinging precisely as though the air current made no difference to it.
This indicates that calopus would not easily be carried involuntarily by the
wind. Opposed to these assertions of Goeldi are the observations of Otto and
DISTANCE OF FLIGHT 273

Neumann at Rio de Janeiro, They state that a draft is undoubtedly disagree-
able to calopus. On this account they searched for it in vain in exposed situa-
tions accessible to wind, as for example the Monte da Providencia within the city.

It would seem that the yellow-fever mosquito does not fly very far and the fact
that it is very rarely found away from houses supports this view. Carter points
out that it probably never flies high, and that it is found by preference in the
lower stories of houses. The same writer in 1904 suggested that the problem of
flight be investigated as of importance in determining the anchorage of vessels
in yellow-fever ports. He say on this point:

“So far he knows of no direct observations on this subject, except those of
Goldberger at Tampico, and of Grubbs at Ship Island Quarantine. The latter
found Stegomyie aboard three vessels from Vera Cruz, two of which claim to
have lain a half mile from shore. He believed they came aboard at Vera Cruz.
The observations of Goldberger will be given later.

“ Although direct observaticns on this problem are few, yet there are certain
indirect ones, bearing, however, entirely on the aérial conveyance of the Stego-
myia infected with yellow fever. It is notorious that yellow fever is usually
conveyed but a short ways aérially, ‘across the street,’ or, more often ‘to the
house in the rear, which is about as far as it was expected to be thus conveyed.
This represents a maximum distance of about 75 yards. The two longest dis-
tances recorded in recent times of aérial conveyance, one of 225 meters (Mélier)
and one of 76 fathoms—456 feet (the writer) are entirely exceptional. So much
for the distances which the (infected) Stegomyia is conveyed—or rather usually
conveyed—aérially.

“ On the other hand it is known that vessels moored in certain districts of the
Havana harbor did not develop yellow fever aboard, except in those who had been
ashore, or unless they lay close to other vessels which were infected. This ex-
periment hus been made on so large a scale—with so many vessels and for so
many years—that we must accept as a fact that an infected Stegomyia was not
conveyed aérially from the Havana shore to those vessels, or, allowing for errors,
was very rarely so conveyed. This distance which had been found safe was some-
thing over 200 fathoms—1200 feet. The prevailing wind was generally slightly
on shore, but was not constantly blowing. Whether there is any difference in
the distance to which infected or non-infected mosquitos are conveyed, is, of
course, entirely a matter of surmise. There is no apparent reason why there
should be. Yet the infected Stegomyize have almost certainly become so in a
house; and with their very domestic habits must be found out of doors, where
they would be subject to conveyance by the wind, in much smaller numbers than
the uninfected insects, and consequently a lesser number of them would be con-
veyed aérially. Observation is needed on this subject—the distance (across
water) that Stegomyie are aérially conveyed. ui on

“ Goldberger, very ingeniously, suggests that on account of its diurnal flight,
the direction of the wind during the day only need be considered in estimating
this factor in their aérial conveyance, and states that at Tampico he failed to
find Stegomyie aboard vessels lying, for ten or fifteen days, about half a mile
from a place on shore where they were abundant, while numbers of Anopheles
albipes * and Culex pungens + were found. The wind was on shore during the
day and calm or off shore during the night. The importance of this point is
obvious, as on the coast, except when overborne by the trades, the direction of the
wind is very generally different by day and night.”

 

* Anopheles albimanus Wied.
+ Oulex quinquefasciatus Say.
274 MOSQUITOES OF NORTH AMERICA

It would seem as if in this discussion the possibility of the conveyance of mos-
quitoes to ships by means of lighters for the discharge of cargo could not be
omitted. This is the common method of exchanging cargo in many tropical
ports and furnishes a ready means of transferring mosquitoes from the shore to
the ship.

At an earlier date this question of distance of flight was considered by one
of us (Howard), and he endeavored to induce several surgeons in the U.S. Navy
to make observations. A series of notes were sent in by Surgeon A. H. Russell
of the Navy, who made some interesting observations. With a vessel anchored,
say a mile from shore, and constant boat parties going to and fro between the
vessel and the shore, there is always the chance that A édes calopus may be carried
under the coat lapels or even in the pocket of passengers. Therefore the occur-
rence of a few individuals on shipboard at this distance, and with constant
traffic going on, is inconclusive. Russell (in litt.) observed one instance, and
investigated all factors carefully, in which he apparently proved a flight from
shore to a vessel anchored a mile out, but it would be practically impossible to
eliminate all chances of error in such a case.

Bearing upon the question of the origin of calopus on board ships the obser-
vations of Durham at Para are significant.

“Tt is said by captains that mosquitoes only commence to come on board when
the lighters which are used for the discharge of the cargo are brought alongside.
Seeing that the anchorage for the large ships is some two miles below the city,
and the lighters lying about the neighbourhood of the city are brought to whart-
sides for discharge, they are a means of bringing city mosquitoes to the ships.
On examination, several of the large barges (which are covered with a rain-
proof metal cover) were found to harbour a certain number of the insects, both
S. fasciata and C. fatigans were found in the adult condition and a few larve
of the former in the bilge water ; but these lighters had recently been cleaned up
and painted; open lighters are also used, these were seen to contain abundant
rain water and tar and oily material from the coal for which they are used; no
larvee were found in them.

“ During my trip up to Mandos, indiscriminate collection of all and any mos-
quitoes that could be found on board was made. Although a number were col-
lected it was not until after anchoring at Mandos and the lighters came alongside
that the species S. fasciata was taken. It appears that the method of discharge
by means of lighters may be almost as risky for the importation of mosquitoes
infected in the city, as if the vessel was actually brought to the wharfside.”

Busck, on the occasion of his visit to Trinidad, made an observation which
bears upon the distance of flight of calopus. He states that at La Brea there is
a long pier, built by the asphalt company, near the end of which the superin-
tendent erected his house in order to be free from mosquito molestation. The ex-
periment was successful, and he lived in peace, until, later, another official, for
similar purposes, built a house in the middle of the pier. This apparently
afforded just the right interval for calopus to spread from the shore to the house
in the middle of the pier, and from that house to the one on the end of the pier,
and both houses became infested. The entire length of the pier was about 400
feet.
SEXUAL ACTIVITIES 275

Assistant Surgeon Grubbs, of the Public Health and Marine-Hospital Service,
in a paper entitled “ Vessels as Carriers of Mosquitoes,” published as Bulletin
No. 11 of the Yellow Fever Institute, which has been mentioned more fully on
another page of this volume, gives instances which seem to indicate that calopus
came aboard a schooner at Vera Cruz, the vessel lying half a mile from the shore;
that another vessel had the same experience. But the evidence is not analyzed
and the probability of the mosquitoes being brought to the ship by lighters,
which at that time were used at Vera Cruz for the interchange of cargo, is not
taken into consideration. In the first of the instances mentioned it is stated
that mosquitoes came aboard “ in large quantities.” Some of these were said to
be calopus, but it is not stated that all belonged to this species. It is possible
that Aédes teniorhynchus, a common coast species, may have been mistaken for
Aédes calopus.

MATING.

E. G. Hinds, of Victoria, Texas, in a report submitted to one of the writers
(Howard) in the autumn of 1903 shows that with this species mating begins
when on the wing. It may, and usually is completed while still flying, but the
female frequently alights during the act and before its completion. The com-
plete act requires but the fraction of a minute. According to this observer,
females partly or fully fed seem more attractive to males than those which have
not fed at all. Copulation sometimes, perhaps usually, occurs before either sex
has fed. Males often alight on the dark colored clothing of a person sitting
quietly and watch their chance to pounce upon a female coming to feed. The
time of the greatest activity of copulation seems to be between 4 and 6 p. m.
A male may mate with several females. More than one batch of fertile eggs may
be laid without intervening fertilization.

The French investigators found that temperature has a great influence on the
sexual activity of Aédes calopus. When the temperature rises above 25° C.
(77° F.) the males become very active and the females but rarely escape fertili-
zation. When the temperature ranges between 20° and 25° C. (68°—77° F.)
fertilization is still the rule and the proportion of unfertilized females is very
small, but below this the proportion of unfertilized females increases rapidly
with the reduction in temperature.

Goeldi points out that wherever many of these mosquitoes are together, the
males tend to congregate apart in little clouds of fifteen or twenty or more; they
show a marked tendency to gather over prominent objects, as the corner of a
table or other salient parts of furniture, while the females are flying all about the
room. He has noticed that they will settle themselves on the upper parts of mos-
quito bars while the females are flying around under the bed or in the immediate
vicinity. “These are lookouts, salient points for watching and observation,
whence the males direct themselves against any female that happens to come into
their area of dominion.” When a female approaches one of these groups of
males she is pounced upon, the male clasping the female from beneath. Goeldi
says “ He unites himself to her from the lower side and permits her to carry him
with a slow heavy flight for a few seconds (two or three only), and then again

19
276 MOSQUITOES OF NORTH AMERICA

separates himself.” He stated that the act is so fleeting that people note it with
difficulty, and he has always failed to kill specimens in the act except by smash-
ing them between his hands. He also says that they will copulate within the
narrow dimensions of a bottle or breeding cage, a fact that facilitates the
fecundation of females bred in captivity and thus enables the breeding of the
species for many successive generations. Goeldi confirms the observation of
Hinds that the same male has frequent connections in rapid succession with
various females which approach him. Peryassi also found that a male will
copulate with more than one female in succession.

The copulation of Aédes calopus has been observed by a number of other in-
vestigators. Nearly all of them agree that it takes place in the daytime, during
flight, face to face, and that it is of very short duration. Both sexes are ready to
mate soon after leaving the pupa.

One of us (Knab) has pointed out that Godeheu de Riville, a French naval
commander, in the third volume of the Mémoires de Mathématique et de
Physique, published in 1760, has described the copulation of what was with little
doubt this species, since he states that the species of mosquito he observed was
most active during the warmest hours of the day, that it was a domestic species,
and united with the female face to face. The observations were made on board
ship during a voyage from India. We quote from Knab’s article:

“ However, upon May 13, a lucky chance permitted him to observe what for
more than two months had been the object of his research. Seeing a pair of
mosquitoes united and hovering in a sun-beam, he gently approached them to
obtain a better look. Escaping him they flew to the rear of the cabin where,
after an irregular flight, they entered the canopy of the bed and alighting re-
mained suspended from the under side of the canopy-top. Here the light yellow
color of the cloth contrasted well with the dark bodies of the mosquitoes and this
proved to be the long desired opportunity. Waiting until they had become well
settled he approached cautiously. The female, recognized by the length and
stoutness of her body, sat in the ordinary position of mosquitoes ; she clung to the
fabric with her front and middle legs, the two hind legs elevated in a half-
circle above her wings. The male, on the contrary, had assumed a different
attitude. The smaller size of his body and the necessity of obtaining union with
the female, who did not seem inclined to incommode herself, left him apparently
less at ease. His two greatly elongated front legs alone held him to the top of
the canopy while with the other four legs he grasped the female. In spite of
their movements, the commander was able to study them well and settle all
doubts. An involuntary move on his part, caused by the rolling of the vessel,
startled the pair from its resting-place. Still united they tried to obtain a new
hold, but without success, and finally flew off and were lost to view, having prob-
ably separated.

“ From his observations Godeheu de Riville concluded that copulation in mos-
quitoes does not last long, takes place very quickly in comparison with other flies,
and appears to occur only in the air. He considers that the attitude assumed
does not permit them to alight, and that the one couple thus observed was a rare
exception. None of the many other couples which he attempted to observe more
closely came to a resting position.”
NECESSITY OF BLOOD AS FOOD 277

RELATION OF FOOD TO OVIPOSITION.

Finlay found that the female Aédes calopus could not develop its eggs without
having obtained blood. “Nearly all the females captured after having filled
themselves with blood, at the end of a few days lay eggs, while those which are
fertilized and have not been able to obtain blood die without ovipositing.” He
believed furthermore, as calopus does not lay all its eggs at once, that it needs
several blood meals to dispose of all its eggs.

Reed and Carroll confirmed the observations of Finlay and found that the
interval between a blood meal and oviposition may vary from two to thirty days.
“ As a rule, the eggs are laid within seven days; sometimes a second or third
meal of blood is taken before any eggs are laid.”

The French commission also found that in calopus blood food is indispensable
for the reproduction of the species. They found that whether the female sucked
blood before or after copulation the eggs would be deposited within a few days.
If a fertilized female is fed on sweet substances the eggs will not develop; if
afterwards, for example after 15 or 20 days, the female is fed blood the eggs
will then develop. In the latter case the interval between the blood meal and
oviposition will be about the same as when it has fed on blood soon after being
fertilized. In one of their experiments 10 females and 15 males were placed to-
gether in a cage on the same day that they had issued from pupw. Three of the
females were taken out 48 hours afterward and induced to suck blood. Of these
three females one deposited eggs after four days, the other two after six days.
After 18 days three of the females which had been fed only upon honey, and
which had not oviposited, were allowed to suck blood; they deposited eggs five
days after the blood meal. The four remaining females which had not been
allowed to suck blood died without depositing eggs. The French observers state
that the result is the same whether the females are allowed to bite man or some
other warm-blooded animal, but that it must be remembered that calopus shows
more or less repugnance towards any other animal.

Goeldi, at Para, made a series of experiments with similar results. One of his
conclusions is that blood food, in hastening the development of the eggs, shortens
the life of the mosquito. On the contrary a diet of honey prevents the develop-
ment of the eggs and thus prolongs life. He found that by feeding the females
with honey the power of depositing fertile eggs may be kept latent for long
periods. He determined, also, that unfertilized females would lay eggs when fed
with blood but that these eggs would not produce larve (pseudo-partheno-
genesis). Goeldi found that the interval between the first blood meal and
oviposition averaged 3.7 days=88 4/5 hours. The female, after having de-
posited all her eggs, dies, either immediately afterward or at the most within a
few days. The longest time that a female survived oviposition was 14 days.

Goeldi determined that the shortest interval between a blood meal and ovi-
position was two days, the longest interval seven days. He gives observations in
which eggs were laid one day after a blood meal, but in these cases the females
were captured and probably had already sucked blood. On one occasion, in an
experiment with captured females, eggs were laid after blood had been withheld
278 MOSQUITOES OF NORTH AMERICA

during an interval of 15 days or more. All 36 of the eggs deposited proved
fertile and had produced larve five days later. Goeldi supposed that in this ex-
ceptional case oviposition resulted from the effect of a previous blood meal. In
another experiment Goeldi fed a female exclusively with honey for 75 days with-
out obtaining eggs; she was then fed blood for 20 days. On the 20th day of the
blood diet a single egg appeared and six days later, or 102 days after the experi-
ment was begun, 85 eggs were deposited. Goeldi calls this the first batch of eggs
but it would seem as if there had been some oversight, for, 13 days after the
female was put on a blood diet a larva was found in the breeding cage. Goeldi
tried to determine the comparative effect of guinea-pig blood on oviposition.
Of two females fed with guinea-pig blood one laid seven eggs three days after
the first meal; the second female was given another ration and four days later
had laid no eggs. Goeldi remarks that these data are too insufficient to be con-
clusive, but he expresses the belief that it will be found that human blood is
much more effective than the blood of the guinea pig.

The French investigators pointed out that the ability of calopus to transmit
yellow fever depends upon the fact that it needs several blood meals to develop
all its eggs. The female continues to bite after having oviposited and, without
being fertilized again, deposits more fertile eggs, and this may be repeated a
number of times. They found that in captivity a single blood meal between
ovipositions was effective. They state that in freedom calopus, after having
deposited eggs, would often bite every 24 hours and sometimes even several times
within that period, and they call attention to the significance of these frequent
bites in the transmission of yellow fever. Among the females which have de-
posited eggs once there are some which survive a long time, and, while con-
tinuing to suck blood, do not lay more eggs. This, they think, is due to the fact
that the supply of spermatozoa in the receptacula seminis has been exhausted.
These females, in the opinion of the French investigators, are the most dan-
gerous on account of the probability of their living a long time and biting many
persons.

It has already been shown that calopus will only feed upon blood obtained by
piercing the skin. Otto and Neumann claim that they were able to feed female
calopus with a mixture of blood and salt solution placed upon cotton. The mos-
quitoes sucked the blood from the cotton without hesitation; afterwards eggs
were laid in the normal manner and larve hatched from these, but it appeared
that these larve lacked the usual vitality.

The French investigators made feeding experiments with human blood serum,
with red blood corpuscles separted by centrifugal action, and with blood clots,
and from none of the females so fed were they able to obtain eggs. When these
same females were afterwards allowed to suck blood they laid eggs. They con-
clude from this that calopus must have fresh blood in order to lay eggs.

OVIPOSITION.

Aédes calopus deposits its eggs separately in several lots, the separate lots being
disposed of at intervals of several days or more. The eggs may be laid near the
DISPOSAL OF EGGS 279

water, close to the edge, or upon the surface of the water. Finlay says they “ lay
their eggs singly or in rows of 9 to 15, separated or contiguous, sometimes upon
the water at others upon adjoining objects very close to the water level so that
a slight elevation of the water will submerge them.”

The second commission to Vera Cruz state that “ The eggs are sometimes laid
on the water, sometimes on the side of the vessel above the water line, and some-
times on a leaf floating on the water.”

The French commission state that the eggs are laid at the edge of the water or
upon it and that the latter is the commoner method. In accordance with their
assumption that calopus is nocturnal they assert that the eggs are generally laid
at night, but they admit that “numerous” captive females oviposited in the
daytime. They state that oviposition extends over several hours and that the
time required depends upon the temperature. They found a night temperature
of 27° to 28° C. (81°-82° F.) with a diurnal maximum of 29° to 30° C.
(84°-86° F.) most favorable in hastening oviposition. Under these conditions
the eggs may be laid 48 hours after a blood meal, while usually the interval is
from three to four days. When the nocturnal temperature is between 25° and
27° C. (77°-81° F.) the eggs are deposited on the fourth or fifth day; when it
ranges between 20° and 25° C. (68°—77° F.) oviposition occurs on the sixth day
and sometimes not until the seventh or eighth day. When the temperature is
below 20° C. at night and does not rise above 22° or 23° C. (72°— 73° F.) in the
daytime oviposition is retarded until the temperature rises to 26° or 27° C.
(79°-81° F.) and sometimes it will be prevented altogether.

Durham says of the disposition of the eggs that they “ are deposited close to
the edge of the water, if not sometimes actually on the surface of the containing
basin. At any rate, they readily adhere to this surface sufficiently firmly to pre-
vent detachment by a stream of water ; this is probably of use when the breeding
places (e. g.,a small tin or a roof gutter) is exposed to tropical rain.”

H. W. Henshaw, while living at Hilo, Hawaii, among other interesting ob-
servations made on this species, found that the females laid eggs every day
around his cottage in vessels prepared for them and that they invariably de-
posited them upon the moist sides of the containers, perhaps a sixteenth of an
inch above the surface, and never touching the water. Eggs removed from these
moist spots hatched within 30 minutes after having been placed in water
(in litt.).

This undoubtedly represents the mode of oviposition under natural conditions
as it corresponds with that of the nearly related tree-hole inhabiting species of
Aédes. The impression that calopus lays its eggs upon the surface of the water
appears to have been gained by observations with females in captivity. It is
probable that the smooth sides of the glass receptacle in which such captives are
kept is not a suitable surface for the attachment of the eggs.

The method of oviposition has been described by Agramonte:

“The mosquito alighted upon the water, which was in a small beaker inside
the jar, with legs spread wide apart. The abdominal segments being bent
forwards and downwards, she dipped her whole body until the last segment
280 MOSQUITOES OF NORTH AMERICA

touched the surface of the water ; then she rose, walked a few steps, and dipped
again. This she would do repeatedly (14 to 22 times), when she would remain
for a slightly longer time with the last abdominal segment touching the water,
and would allow a minute white egg to issue forth upon the surface. In this
way she laid at the rate of 3 eggs per minute, resting quietly after every sixth or
eighth egg for about 30 seconds when she would resume the process.”

There are many observations on the number of eggs deposited by one female.
It has already been shown that in this species the eggs are not laid at once but in
batches, at intervals, the last determined by the blood meals of the female. The
French investigators found that about half the females died without depositing
eggs a second time. Out of 100 females 30 laid eggs the second time and 21 laid
eggs from three to seven times. This last was the largest number of ovipositions
observed by them in a single female.

Taylor of Havana states that the number of eggs varies from 35 to 114; the
first American commission to Vera Cruz gives the number of eggs as from 40 to
150, but in neither case are details given. Goeldi thought that the maximum
number of eggs from one female ranges between 50 and 100 and on one occasion
there were some in excess of the last number. The French commission found
the maximum number of eggs from a single female 144.

Francis, in the report of the Working Party No. 2, records experiments with a
number of females at Vera Cruz. In one of his experiments a female laid 51
eggs on October 25th, 24 on November 7th, and 26 on November 8th, a total
of 101.

The French investigators found that generally the first batch of eggs is much
the largest, between 70 and 95; sometimes there are less and very rarely more.
The succeeding batches are smaller and do not go above a maximum of thirty.

Goeldi considered the death of the female after oviposition a certain index
that all the eggs had been laid. The French investigators point out that the
number of eggs varies considerably and that one can not draw conclusions with
such certainty. They found, on the one hand, that females after having de-
posited from 70 to 95 eggs remained alive for several months ; on the other hand,
they noted that females which had deposited but 30 eggs refused all food and
died after a few days or within a few hours. In one case a female which had
deposited 82 eggs died three days later, after having been fed ; dissection showed
that 30 partly developed eggs were present.

The French investigators found that there were small females which laid but
a small number of eggs. These females came from larvae which had developed
under unfavorable conditions. The number of eggs from such females did not
exceed 50 or 60 and sometimes it was even less. The season has a certain in-
fluence in this connection. Thus it was found at Rio de Janeiro that the pro-
portion of females which died after laying the first batch of eggs was con-
siderably less during the warm months than in the cool season.

Peryassi determined that in order to obtain a full complement of eggs it is
necessary to feed the female with blood repeatedly, at intervals of at least every
two or three days.
CONDITIONS AFFECTING EGGS 281

BREEDING HABITS.
THE EGGS.

The different stages of this mosquito are carefully described in the systematic
portion of this work. The eggs, as above described, are frequently laid in small,
irregular groups some distance above the margin of the water, and may remain
dry for long periods, hatching when reached by the water. They develop better
after having been dry for a period. Reed and Carroll state:

“The resistance of stegomyia’s eggs to external influences is worthy of note.
Drying seems to be but little injurious to their subsequent fertility. We have
found that eggs dried on filter paper, and kept for periods of from ten to ninety
days, will promptly hatch when again submerged in water. Dried eggs brought
with us from Havana, in February, were easily hatched during the month of
May, in Washington, furnished about 60 per cent. of the usual number of larve
hatched from fresh eggs. Freezing does not destroy the fertility of the eggs.
Although freezing with a mixture of salt and ice for thirty minutes has several
times seemed to prevent subsequent hatching; on one occasion a batch of one
hundred and fifty-five eggs, freshly deposited, which were frozen at a tempera-
ture of -17° C., for one hour, then thawed out at room temperature and placed in
the incubator at 35° C., began to hatch on the sixth day, the majority furnishing
active larve on the eighth day. In another observation, freshly deposited eggs,
frozen at -17° C. for half an hour on two successive days, began to hatch on the
third day as usual at incubator temperature. The resistance of stegomyia’s
eggs to drying for a period of three months would appear to demonstrate that
this genus of mosquito could survive the winter in Havana, without the presence
of hibernating females. Doubtless the genus is preserved in both ways. It is
probable that the same could occur in our extreme southern latitudes.”

The Brazilian investigators at Rio de Janeiro determined that the eggs will,
when dry, preserve their vitality unimpaired for five months. Eggs placed on
filter paper and kept in test-tubes developed after this period but beyond that
period they failed to hatch. Francis asserts that eggs hatched which he had
kept dry during six and a half months. Eggs sent to Theobald in England,
from Cuba, hatched after two months and a half. Itis to be supposed that under
natural conditions the eggs of calopus will survive out of water even longer than
the longest period achieved experimentally. It should be remembered that in the
majority of the species of Aédes the eggs do not hatch until the following year
and that a percentage, with some, and we believe with many species, remains
dormant until a second year.

Agramonte (a member of the American commission to Cuba), in a chapter on
mosquitoes and yellow fever appended to Berkeley’s “ Laboratory Work with
Mosquitoes” (New York, 1902), states that the duration of the egg-state varies
according to the season of the year, the temperature of the water and the
chemical conditions of the water. He shows that with the lye of wood-ashes, em-
ployed by laundresses in Cuba for the purpose of whitening the clothes, the eggs
hatch more quickly than in the dirty water of overflows and gutters, and yet the
latter contains more organic matter.

The duration of the egg-stage according to Agramonte is from fifteen hours
to three days. J. R. Taylor, of Las Animas Hospital, Havana, gives the dura-
tion of the egg-stage as 12 to 24 hours. The first American commission to Vera
282 MOSQUITOES OF NORTH AMERICA

Cruz gives 10 to 24 hours as the duration of the egg-stage. Goeldi gives the
minimum duration as three days. The French commission indicate a minimum
period of two days.

It appears that eggs which have been deposited out of the water hatch very
promptly when submerged, just as is the case with related species of Aédes.
When the eggs are deposited directly upon the water they require at least two
days to hatch. The discrepancies in the data of different observers can probably
be explained by these facts.

Eggs deposited on the surface of the water float, but they are easily sunk by
disturbing the water. Goeldi states that eggs invariably perish when submerged.
The investigations of the French commission show that this is not the case.
They found that hatching is somewhat retarded by immersion and that some-
times some of the eggs do not hatch, particularly if the temperature of the water
is rather low. Peryassi found that if eggs were submerged a day after being
laid, and the temperature was not below 26° C. or above 29° ©. (79°-84° F.),
they would hatch at the same time with those that floated. It would seem how-
ever that the eggs which are submerged soon after being laid generally perish.

The French investigators found that the eggs suffered when immersed in water
at low temperature for a considerable time. They were not only subject to the
attacks of various organisms under these conditions but the egg-shell was also
gradually softened and would finally allow the water to enter. Eggs which have
perished by prolonged immersion do not remain intact but split open. While
in hatching the egg splits transversely at about one-fourth from the larger end,
the dead egg splits open longitudinally. The French investigators conclude that
survival of the eggs is much more certain in a dry state than when submerged.

In Cuba, according to Reed and Carroll, the eggs begin to hatch in summer
temperature, as a rule on the third day. They record two days as the shortest
egg period. Presumably these observations were made with eggs deposited
directly upon the water.

The French commission found that a temperature of 27° to 29° C. (81°-
84° F.) was the most favorable and in it the eggs would hatch within two or
three days. Ata temperature of 25° to 26° C. (77°-79° F.) the eggs usually
still hatched with considerable regularity after four or five days. At high tem-
peratures the eggs from one batch hatch together, or at the most within a few
hours of each other. Below 25° C. hatching is irregular and only part of the
eggs hatch, and below 20° C. (68° F.) it ceases altogether. In temperatures
between 25° to 20° C. but a few larve appear and generally all the eggs remain
dormant until there is a rise of temperature.

The eggs will survive low temperatures down to the freezing point. While
ordinarily the chilling of the eggs is not fatal it nevertheless has a bad effect on
the entire development of the mosquito. In nature a drop of temperature to
below 20° C. in a single night will not only retard the hatching of the eggs but
also the development of the larvee. The French investigators further determined
that the eggs will withstand temperatures of from 20° C. to freezing for a con-
siderable time; if then subjected to a suitable temperature the eggs will hatch.
PUBLICATION 159
PLATE X

 

 

w

 

1. Covered rain-water tanks at New Orleans.

2, House at Pretoria, Transvaal, protected against ants by resting on
water-filled metal pans which are breeding-places of mosquitoes.

3, Mosquito-breeding tree-hole.
ADAPTATION IN BREEDING HABITS 283

However, if the eggs are kept in low temperatures for some months there will be
a considerable loss. In one case eggs which had been exposed to night tempera-
tures of from 10° to 20° C. (50°-68° F.) for 70 days were placed in a proper
temperature for hatching and only one-twentieth of them produced larve. The
French observers concluded from their results that eggs subjected to low tem-
peratures for some months will perish.

The Brazilian investigators made careful experiments with high, as well as
low, temperatures. Eggs taken from the water the day after they were laid were
placed for five minutes in an oven regulated to temperatures of from 37° to 47°
C. (99°-117° F.) ; when afterwards placed in water they hatched after 48 hours.
The larve from these eggs developed in a normal manner and the first imago, a
female, issued seven days after the hatching of the eggs. Exposed to a tem-
perature above 48° C. (118° F.) for five minutes the eggs failed to hatch for
the most part; the few that hatched only did so after from four to six days. At
49° C. (122° F.) and above the eggs would no longer develop.

Peryassii records the following experiments regarding the effect of cold on
the eggs. Eggs frozen in a mixture of salt and ice for 30 minutes failed to
develop. In another experiment 150 recently laid eggs were frozen for one hour,
and then, after being allowed to thaw out, were placed in an oven at a tempera-
ture of 35° C. (95° F.) ; they began to hatch on the sixth day. In still another
experiment eggs, also recently laid, were frozen for half an hour on two suc-
cessive days; they hatched on the third day.

Experiments were further conducted on the effects of varying degrees of
salinity of the water on the hatching of the eggs. Eggs would not hatch in pure
sea-water. Female calopus were induced to lay their eggs in a mixture of fresh
water with 30 to 35 per cent sea-water; these eggs hatched and the larve de-
veloped to imagos. With 40 per cent of sea-water the eggs hatched but the
larvee did not develop.

BREEDING-PLACES.

There seems to be a strong probability that Aédes calopus was originally a
tree-hole breeding mosquito. There are several arguments in favor of this con-
clusion. The mosquitoes which come closest to it in general habits are tree
breeders. Calopus itself will breed in tree-holes when such happen to be near
human habitations. Tree-hole breeding forms, like Aédes triseriatus, will breed
also, when there are human habitations near their original home, in rain-water
barrels and other domestic accumulations of water such as seem now to be the
normal breeding-places of calopus. The tree-hole breeding forms, like tri-
seriatus and mediovittata, are continuous breeders just as is calopus, whereas
the forms breeding in temporary puddles and swamps are more or less periodical
in their occurrence, depending to a great extent upon rainfall. The egg-laying
habits, as just described, are in accordance with this view. Originally, then, a
tree-hole species, calopus has so perfectly adapted itself to human civilization
that it has become a true domestic form and practically dependent for its ex-
istence upon the conditions that surround human habitations. This dependency
284 MOSQUITOES OF NORTH AMERICA

upon the human species is undoubtedly of ancient development. The preference
for human blood is well demonstrated, and, as has been pointed out, the work
done by several investigators seems to prove that calopus does not oviposit until
after having had a meal of human blood. Although Goeldi has shown oviposition
after a meal of guinea-pig blood, he considers human blood more efficacious
in bringing about ovulation.

We have already demonstrated that calopus is essentially a town mosquito.
The larvee are found practically exclusively in artificial receptacles about human
habitations. It may be said that the larve of calopus are never found in swamps,
in pools or in temporary puddles, even when these are in close proximity to
houses. Durham, who studied the species at Paré, makes the following state-
ment concerning the breeding-places. “Casual water in vessels, etc., in and
about houses such as buckets, tins, washtubs, rain gutters, ant-guards (per-
forated troughs to protect plants in gardens, and sugar, ete. in houses), larger
and deeper collections of water as casks or hogsheads full of rain water. Also
in bilge water of barges, lighters, and 8. S. Viking (Amazon Telegraph Co’s
ship, many years on the river). Not found in sewage collections as cesspools,
stable runnings, etc., although found in neighbourhood in cleaner waters. Also
not found in natural puddles in forest or streets, etc.” We are well aware that
there are a number of records of calopus larve occurring in street puddles and
in swamps, but it would seem that in these cases the larve were not bred and
most probably they were those of some other species of Aédes, many of which
greatly resemble calopus in general appearance.

In the tropics the large earthen jars in which drinking water is kept are the
most frequent and unfailing habitat of the larve. Rain-water barrels are abun-
dant breeding-places. In New Orleans and other southern cities, like Galveston
and Mobile, rain-water tanks, so abundant behind the houses, are probably the
source of the most abundant supplies of these mosquitoes. Reed and Carroll
state that in their search for the larve of this insect in Cuba they found them
in the following places: “ (1) In rain-water barrels; (2) in sagging gutters
containing rain water; (3) in tin cans that had been used for removing excreta
and which still contained a small amount of fecal matter; (4) in cesspools; (5)
in tin cans placed about table legs to prevent the inroads of red ants; (6) in the
collection of water at the base of the leaves of the agave americana; (7) in one
end of a horse trough that was in daily use.”

In New Orleans, in the epidemic of 1905, water-closet tanks were found to be
abundant breeding-places, and Surgeon White suggested that an ordinance be
made and enforced to cover these tanks with wire gauze. They were also found
breeding in the accumulation of water in the drain traps of stationary wash-
stands. Roof gutters, in New Orleans, were especially noticed on a number
of occasions, where they sagged, to contain large numbers of calopus larve.
Another interesting place where they were found breeding was in the urns in the
cemeteries. In the autumn of 1905, at New Orleans, Surgeon Richardson, of
the Public Health and Marine-Hospital Service, told one of the writers
(Howard) that at Laredo, Texas, in the outbreak of 1903, calopus was found
BREEDING HABITS 285

breeding in the lye barrels where ashes were mixed with water for the purpose
of making lye. He also noticed them the same season in the holy-water fonts in
churches. In New Orleans they were also noticed in the holy-water fonts, but
here, after this had been pointed out, wet sponges were substituted for standing
water. Moreover, in New Orleans it is the custom to keep wine cool by placing
it in the pools of water accumulating under the water tanks, and in these pools
the yellow-fever mosquito was found to breed extensively. In some houses in the
low quarter of the city water was found to accumulate under the houses, and
here also the yellow-fever mosquito bred. At San Antonio, Texas, in 1903,
Surgeon Mason, of the U. S. Army, informed one of the writers (Howard) that
he had found calopus breeding not only in such places as have just been men-
tioned, but in the water pans in the chicken yards and in the water receptacles
of an old grindstone in a yard.

In 1905 Messrs. Busck and Knab, in their respective journeys to the West
Indies and to Central America, made especial notes on the breeding-places of
this species. Both of these observers stated that calopus nearly always breeds in
clear water and very seldom in foul water. They always found it in artificial
receptacles except a few times in tree-holes near houses and in one case where
Mr. Knab, at Cérdoba, Mexico, found a larva of this species in a street gutter.
This larva probably came there by the emptying of some vessel. Goeldi was of
the opinion that the larva of calopus could only develop in clear water. Busck
has on two occasions found the larve in very foul water and the French com-
mission noted that it thrives in filthy water. However, the breeding in clear
water is the rule. Mr. Knab found that the house of the American Consul at
San Salvador was especially infested by this species. The larve throve abun-
dantly in the garden, in the small water-filled stone gutters which served to
protect the plants from the leaf-cutting ants. In a church in Grenada Mr. Busck
found calopus breeding abundantly in the holy-water font, and also in several
other churches in different West Indian islands. This fact was mentioned in
a paper presented by one of the writers (Howard) before the International Con-
gress of Sanitarians of the American Republics held in Washington in the
autumn of 1905, and was widely exploited by the newspapers. The matter was
taken up by an ingenious resident of Boston who forthwith invented a holy-
water font in which it is impossible for the yellow-fever mosquito to breed, the
water being allowed to issue from the font drop by drop from a faucet. Adult
mosquitoes were found to be abundant in churches where the larve were breed-
ing in fonts, and under these conditions such churches must always be sources
of great danger. In Trinidad Busck found that beer bottles were used as a
border ornament for the flower beds; the necks of the bottles were stuck into the
ground and in their slightly convex bottoms (turned upward) water had ac-
cumulated and calopus were breeding. In the broken bottles forming the cheval-
de-frise on the stone wall around the jail, he found that water had accumulated
and the yellow-fever mosquito was breeding. Knab, at Acapulco, found these
mosquitoes especially abundant in his hotel. In the patio there were beautiful
flowers protected from ants by water in shallow trenches ; in this water calopus
286 MOSQUITOES OF NORTH AMERICA

was breeding abundantly. Discarded bottles and tins about houses are favorite
breeding-places. Dutton, at Bathurst in Gambia, found many boats lying on the
beach containing collections of water, in some cases one or two feet deep. This
water almost universally contained mosquito larve of five species, the most
abundant being Aédes calopus.

Occasionally the larvee occur in water in holes of trees, but only when these are
in close proximity to human habitations. In a small grove of fruit trees in the
town of Tehuantepec, Mexico, Knab found the larve in water at the base of the
branch of a mango tree; there were numerous larve in the water-filled holes of
two other trees in the same grove. In the village of San Antonio, near Sonsonate,
Salvador, Knab again found larve of calopus in a hole in a large mango tree.
Jennings found larve of calopus in the hole of a tree, near buildings, at Ancon
in the Panama Canal Zone.

Goeldi, at Para, found the larve in water-bearing bromeliads, presumably
near houses, and in the still folded leaves of banana plants. Peryassti also
records the larve of calopus from bromeliads at Rio de Janeiro. H. W. B. Moore
of the British Guiana Museum has sent us specimens of calopus bred from
bromeliads at Georgetown. He has since found the larve again in similar situa-
tions and writes us in this connection: “The Bromelias from which I bred
calopus were not very far from dwellings. On August Monday (Bank Holiday)
I took a trip into a sparsely populated district where I have not yet collected, and
got more calopus larve in Bromelias. Is it not likely that Bromelias and other
such water-holding plants were the great natural breeding-places of calopus
before it took seriously to breeding in man’s receptacles? It is evident that it
is still one of their natural breeding-places, but they do not succeed as well there
as some other species.” We are inclined to consider the conditions indicated by
Mr. Moore as exceptional and due to the excessively moist climate of British
Guiana. Our belief that calopus originally bred in tree-holes is supported by
the fact that related species with similar habits breed mostly in holes in trees;
moreover it is very rarely that species of the genus A édes resort to bromeliads.

The Brazilian observers have found the larve of calopus in brackish water on
a wharf on the Ilha das Cobras in the bay of Rio de Janeiro, the water showing
a salinity of 35 per cent of sea-water.

BEHAVIOR OF LARV.

The larvee of calopus when suspended from the surface film, to take in air,
hang almost perpendicularly. They are very easily alarmed and then go quickly
to the bottom where they remain a considerable time. They can live under
water, without rising to the surface, for a long time and this is also true of many
other tree-hole inhabiting species of Aédes. When water is poured from a
receptacle inhabited by calopus larve these quickly seek the bottom and their
presence may not even be suspected although the vessels be in constant use.
They cling so closely to the bottom that unless the jars are tipped up so as to
empty them completely, which is not usually done, nearly all the larves remain
in the jars. :
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NATURE OF LARVAL FOOD 287

The first yellow-fever commission to Vera Cruz found that, on account of
this habit, the larve are not easily disposed of by pouring out the contents of a
barrel. ‘“ When the barrel or other container with thousands of larve is ap-
proached and slightly agitated, the insects disappear rapidly to the very bottom,
so that nearly all the water can be dipped from the barrel without removing
more than a few of the larve. The barrel may be turned upon its side, and it will
be found that about 80 per cent of the larve will stay in the few remaining
ounces of water.”

FOOD-HABITS OF THE LARVA.

It has been pointed out that the larva occur most frequently in the clear
water in rain-water barrels or in drinking-water receptacles in houses. The
water in such receptacles contains more or less animal matter, such as particles
of human skin or remains of insects, as well as vegetable refuse, and such
probably is generally the food of the larvee. The larve feed at the bottom, where
they mouth over the organic sediment, even when the water is very deep. Larve
in confinement may be observed chewing vigorously at dead insects or larval and
pupal exuvie.

C. 8. Banks has observed the larve in the Philippines and says: “They feed
largely upon the sediment contained in the dregs, which may be both animal
and vegetable in its character, but more frequently vegetable, as it is composed
of the bits of decaying nipa forming the roofs from which the rain water is
collected. The larve, in feeding, move forward over the bottom of the vessel,
taking in the particles of food with great rapidity and rejecting tiny morsels of
undesirable material in a constant stream.”

Goeldi found that the larvee of calopus are cannibalistic, and this has been
confirmed by the Brazilian observers at Rio de Janeiro, who state that the larger
larve devour the smaller ones. This habit probably accounts for the develop-
ment of the larve in very clear water, which has been so frequently noted.

An interesting fact is that the growth of these larve is greatly hastened by the
presence of a small amount of fecal matter in the water. Reed and Carroll, at
Havana, found that calopus bred in the tin cans used for carrying away human
excrement and throve remarkably under those circumstances.

Dupree and Morgan, of Baton Rouge, have also recorded the fact that by
adding fecal matter to the water they hastened the development until the life-
cycle was completed “in from six to eight days.”

The French commission to Rio de Janeiro found that the larve develop in
clear water, but also thrive in foul water. Water containing alimentary debris,
amylaceous or fatty material seems to suit them perfectly. These investigators
thought that rain water, on account of the microbes which it contains, seems to
be more favorable to their development than spring water. In the laboratory the
larvee were easily reared in water in which had been placed excremental pellets,
or grains of corn or wheat. They seemed to be less at ease in muddy water and
in water containing macerated dead leaves and vegetable debris, but they found
that the differences in the duration of the different stages of larval evolution in
288 MOSQUITOES OF NORTH AMERICA

these different kinds of water were not ordinarily very marked. They decided,
however, that the vigor and the strength and the size of the perfect insect which
resulted was in distinct relation with the larval food. Reed and Carroll found
that muddy water is unfavorable to the larve. “In water, however, which con-
tains much suspended soil—muddy water—the larve, in our experience, do not
flourish, but die off rather rapidly.”

DURATION OF EARLY STAGES.

Temperature has the greatest influence, not only upon the hatching of the
eggs, but also upon the subsequent development of the larve. The effects of
various temperatures on the early stages of calopus were carefully investigated
by the American commission in Cuba and by the French commission at Rio de
Janeiro and the results of both agree very closely.

The shortest period of development to imago observed by Reed and Carroll
during summer weather in Cuba was 94 days, divided as follows: incubation 2
days; larval stage 6 days; pupal stage 36 hours; but they believed that this was
quite exceptional. Their observations on the influence of temperature on de-
velopment are as follows:

“ We have just seen that at summer temperatures the time required for a com-
plete generation of this insect is from eleven to eighteen days. We may say that
at an average temperature of 75° F., or over, stegomyia multiplies abundantly.
Exposure to a cooler temperature, even for a short time daily, much retards the
development of this mosquito. Thus, a batch of fifty-one eggs kept at 35° C.,
but which were placed in a cool chamber at 20° C. for two hours daily during the
whole process of development, although furnishing a few larve at the end of the
third day, were not all hatched until the eleventh day. The first pups appeared
on the fourteenth day and the first mosquito on the nineteenth day; the whole
process being completed in twenty-seven days, instead of the usual fifteen or
eighteen days. The loss of insects was about 50 per cent. Eggs kept at a tem-
perature of 20° C. (68° F.) do not hatch, in our experience. Newly hatched
larve kept at this temperature develop very slowly and require about twenty
days to reach the pupal stage. Mosquitos developed under such conditions are
feeble, and but few arrive at maturity. Young larve kept at 10° C. (50° F.)
have failed to reach the pupal stage—although some growth takes place. In one
experiment more than 50 per cent, were dead at the end of two weeks, and none
survived the thirty-second day. Half grown larve and pupx exposed to a tem-
perature of 20° C., and even as low as 10° C., continue to develop slowly, but the
few insects which escape drowning have, as a rule, been of feeble strength and
have refused to bite. Although the reduction of the temperature to the freezing
point, or below, would not necessarily destroy the vitality of the eggs of this
genus of mosquito, it should be remembered that a reduction of temperature to
68° F., or below, for even a few hours of the twenty-four, will much retard the
development of the generation. Ata temperature less than 68° F. the eggs of
this insect have ceased to hatch.”

Under the most favorable conditions of food and temperature the larva de-
velops with great rapidity. When the conditions are very unfavorable larval
life may be prolonged indefinitely, the larve showing great resistance. Agra-
monte places the minimum period of development from egg to imago at ten
LARV/ IN BRACKISH WATER 289

days; Taylor of Havana, places it at nine days. As already mentioned, Dupree
and Morgan, succeeded in obtaining imagos after from six to eight days.

At Para, Goeldi conducted a number of experiments on the rapidity of de-
velopment of the yellow-fever mosquito. The duration of the entire cycle, from
the date of oviposition to the emergence of the imagos, showed a minimum of
twelve days and a maximum which was indefinite and almost unlimited, accord-
ing to the season of the year and the dearth or abundance of food. He ob-
served one case in which a male emerged only after fifty days, and other cases
where with the same number of days there were still larvee and pupe.

The French observers determined a distinct relation between temperature and
the rate of development. At Rio in the most favorable season, when the night
temperatures were from 26° to 27° C. (79°-81° F.) and the day temperatures
from 28° to 31° C. (82°-88° F.), they observed that some of the larve of
calopus reached the pupal stage seven days after the hatching of the eggs, and
the adult condition on the ninth day, and generally most of the larvee from the
same laying of eggs produced imagos about the tenth day. They found that
when this rapid breeding occurred it was necessary that the egg as well as the
larva should have had the right temperature and the egg a rapid incubation.
The temperature being lower the evolution naturally becomes longer, and at
Petropolis, with a night temperature lower than 22° C. (72° F.), they found
the larve taking from forty to sixty days to reach the pupal state, and from three
to five days longer before the perfect insect issued. Ordinarily, according to
their observations, the pupal stages last only from thirty to fifty hours. They
found that the larve do not perish at a temperature near the freezing point, but
they grew very slowly and took an indeterminate time to become adults.

The French investigators showed that the development of this species is
possible in brackish water, but that soapy water is very destructive to them.
They proved that in sea-water they perish quickly; that this is not true when
sea-water is mixed with fresh water. In one of their experiments a female,
placed in a tube containing five-sixths fresh water and one-sixth sea-water, laid
its eggs as under normal conditions. These eggs hatched at the end of four days,
and the larve, reared in a jar containing the same water, reached the pupal
condition on the eleventh day and the perfect condition on the thirteenth day.
The same result was reached when larve were placed in brackish water con-
taining one-fifth sea-water and four-fifths fresh water, but two young larve
placed in brackish water containing one-third sea-water perished at the end of
a few hours.

RESISTANCE OF LARVA TO ADVERSE CONDITIONS.

“The Brazilian investigators made an extensive series of experiments to de-
termine the effect of brackish water of different degrees of salinity. They found
that in a mixture of 30 per cent sea-water with 70 per cent fresh water the larvee
transformed to imagos {n a normal manner, although development was retarded.
They found larve of calopus in nature in brackish water containing 35 per cent
sea-water. With 40 per cent sea-water the larve still survived and a few pro-
290 MOSQUITOES OF NORTH AMERICA

duced imagos. With mixtures up to 8 and 9 per cent the larve developed nor-
mally but when the salinity was increased beyond this the larval period was
greatly prolonged. Under these conditions larve lived for 50 days without
transforming. One larva, in a mixture with 10 per cent sea-water, died without
transforming after having lived 92 days. Larvee well advanced are much more
resistant and when nearly full grown would still transform in highly saline
water. In a proportion of 50 per cent sea-water the larve generally survived
24 hours and those that were nearly full grown transformed to pupe. Beyond
this the larvee only transformed when they were within one or two hours of the
pupal stage and then only in mixtures up to 56 per cent sea-water. Of 50 larve
placed in a mixture of 60 per cent sea-water three survived to the third day.
The pupz, when placed in pure sea-water, always produced imagos in a normal
manner.

These experiments are of considerable economic importance, as they show that
the larve of calopus may, in nature, survive in water which has, through evapo-
ration, reached a high degree of salinity. If afterwards, through rains, the solu-
tion becomes again diluted the larvee may then develop to imagos.

Experiments were also made with solutions of pure salt (NaCl) and it was
found that the larve would not withstand solutions stronger than one per cent.
Only once a larva transformed to pupa in a solution of 1.5 per cent, but in this
case the larva was already full grown and ready to moult.

The Brazilian investigators also experimented with corrosive sublimate. In
the presence of 1/1000 the larva of calopus, on the average, died after one and
a half hours and the pupe but rarely produced imagos. With 1/2000 the larve
died, on the average, after 44 hours and the pupe produced imagos. With
1/10000 a very few larve developed to imagos, but this only happened when
they were in the last stage.

At Rio de Janeiro it was found that the tanks used for washing clothes were
favorite breeding-places of Aédes calopus. Both the French commission and the
Brazilian investigators experimented on the effect of soap in the water on the
larve.

In their experiments with soap the French investigators found that larve of
any age placed in a solution containing one-thousandth by weight Marseilles
soap died in five minutes. In solutions of one to five thonsand and one to ten
thousand, they lived for a time but finally died. In solutions of one to two
hundred thousand and one to two hundred and fifty thousand, they developed
normally. The larve bred normally in basins and tubs in which linen is cus-
tomarily washed, because, when the soapy water remains in the tubs for some
days, its alkalinity is greatly diminished. Peryassi experimented with common
Brazilian washing soap. He found that larve of any age, when placed in a
solution of one-thousandth by weight died in from six to seven minutes. Only
when the solution was weakened to 1/200000 or less did the larvw develop in a
normal manner.

In apparent contradiction to this extreme sensitiveness to alkalinity are the
observations of Agramonte, already mentioned, that the presence of wood ashes
RESISTANCE TO DESICCATION 291

hastens the hatching of the eggs, and of Jennings who has noted larve in
water containing wood ashes. In this latter case, at Cartagena in Colombia, the
larve were found in large numbers in an earthen pot containing a large quantity
of wood ashes in brackish water from a shallow well near the sea-coast. None of
the larvee produced imagos. In such cases the potash contents, which are
variable with different kinds of wood, must be taken into account and also the
fact, already pointed out, that after some time the water loses its alkalinity.

The degree of resistance to desiccation of the larve and pup of Aédes calopus
is important from the practical standpoint. The first yellow-fever commission
to Vera Cruz found that in that dry climate larve died very quickly when the
water containing them was poured upon the ground. In moister climates the
larve may, under favorable circumstances, live out of water a considerable time
and the pupz show great resistance to desiccation.

Peryassti records a series of experiments conducted on a large scale at Rio de
Janeiro. Placed upon filter paper none of the larve lived nine hours. When
placed upon the moist ground, according to temperature and evaporation, they
survived as much as 13 days, and, when again put in water, developed to imagos.
In the experiments with larve and pupe the following method was employed.
A determined number of larve or pup were put in a watch glass with a little
water and then emptied upon a cone of filter paper; this latter was then placed
upon two other layers of filter paper, to absorb all the water from the first ; then,
when the necessary time had passed, the paper with the larve was placed in a
glass of water so that the number of dead or surviving larve could be deter-
mined, as well as the time they required to return to a normal state. Tabula-
tions of the results are given and from these the following data are extracted.

Larvee dried up to three hours developed normally when returned to the water
and it is only beyond this that they began to suffer. In the course of the many ©
experiments the longest periods during which calopus larve survived were in
one case 8 hours and 20 minutes, and in another 8 hours and 55 minutes. It
must be noted that on the day on which these results were obtained it rained
copiously all day; the evaporation, in the shade, was 1.4 mm. and the relative
humidity 86.1. These results are based upon 64 experiments with 3685 larve.
The larve, when returned to the water, sometimes immediately resume their
activity, but most of them remain immovable for from 5 to 15 minutes. Gen-
erally the larve that did not recover within this time would die. Drying during
periods of from three hours to four hours and fifty minutes was survived by
from 72 to 98 per cent of the larve, and the number of these that reached the
imago state varied from 1.5 to 75 per cent. The time to transformation, after
being returned to the water, varied from 3 to 41 days. Experiments with drying
during 5 hours to 6 hours and 50 minutes gave the following results: The larve
survived in the proportion of 7.5 to 95.5 per cent; they produced imagos in from
2.5 to 62.5 per cent. The period to transformation varied from 3 to 42 days.
Experiments with drying for from 7% to 9 hours resulted as follows; the larve
survived in the proportion of from 4 to 97.77 per cent and produced imagos in
from 1.25 to 26.66 per cent; the variation in the time to transformation varied

20
292 MOSQUITOES OF NORTH AMERICA

from 3 to 32 days. The meteorological factor which most influences the larva
out of the water is evaporation; up to 2 mm. evaporation does little harm but
becomes injurious in proportion to its increase. Pupe dried upon filter paper
survive up to 9 hours and 30 minutes. Advanced pupe produce imagos after
drying of from 5 to 8 hours, and they would issue even while upon the filter
paper. Pups of any age produced imagos when placed upon the moist ground.
To determine the resistance of the larvee upon moist earth 55 experiments
with 3780 larvee were made. The practical conclusions are that the larve, after
being so kept for three days, will develop in a normal manner. One larva, kept
on moist soil for 14 days, under natural conditions, when returned to the water
transformed to imago after three days; this was the greatest endurance observed
by the experimenter. As in the previous drying experiments, the time of trans-
formation was affected, the larve producing imagos in from 3 to 39 days.

THE GEOGRAPHICAL DISTRIBUTION OF THE YELLOW-FEVER MOSQUITO.

As is pointed out incidentally in the consideration of the carriage of mos-
quitoes by conveyances, the yellow-fever mosquito, by reason of its habits,
being a domestic species, having a fairly long life in the adult stage, and having
the custom of hiding itself in the most ingenious ways, is particularly subject to
carriage for long distances on board vessels, in railway trains, even packed
securely away in baggage. It was in this way that the yellow-fever mosquito
was carried from America to Africa, or vice versa, according to the view of the
origin of the species which is adopted. It should be stated that in the old days
of sailing vessels on very long voyages, it was not only quite possible for the
yellow-fever mosquito to breed continuously in the more or less exposed water
supply of the vessels, but undoubtedly this was a common occurrence.

By such means this mosquito is distributed far and wide and during warm
summers is taken often far beyond the point where it is capable of maintaining
itself permanently. Thus there are two distributions for this insect, one in
which it is capable of breeding continuously, and another over which it spreads
during warm weather, to be annually exterminated by the cold, after breeding
for a certain number of generations. Owing to its domestic habits, the mos-
quito does not flourish except in the presence of fairly dense settlements. It can
breed anywhere where man is congregated and the temperature is sufficiently
high. Thus its permanent distribution is determined by the minimum tem-
peratures and its temporary distribution by the maximum temperatures of any
given region wherever it is sufficiently populated.

The permanent distribution is limited in a general way by the frost line.
Where frost does not occur, the species generally may breed permanently. We
have shown in the discussion of the influence of temperature that the species
does not thrive below a temperature of 80° Fahr., so that in a uniform climate
with a temperature much below 80° the species could not continue to exist.
Such climates, however, are rare, and in general when frost never occurs the
general temperature is high enough to permit the species to flourish. Besides
this, the species no doubt continues in particularly favored locations north of
CLIMATE AND DISTRIBUTION 293

this area, perhaps here and there and not always in the same place every winter.
From these foci the summer dispersal is no doubt much facilitated.

The temporary distribution is determined by the means of carriage that hap-
pen to be available. The insects do not fly far, as we have shown, but are readily
carried in conveyances. Thus the species may continue to exist for a time
wherever it may be carried while the temperature remains about 80°.

These facts have not been generally taken into account in discussing the distri-
bution of Aédes calopus, and so the temporary and permanent habitats of this
insect have not been separated. It is impossible to do so from records of cap-
tured specimens only, consequently these distributions can not be exactly
mapped.

When Theobald published the first two volumes of his Monograph of the
Culicide of the World, in 1901, he stated roughly that this insect, which at that
time was not known to him as the yellow-fever mosquito, ranged from 38° south
latitude to 38° north latitude, and his map upon page 292, vol. 1, indicated a
general distribution throughout eastern Australia, western New Guinea, all of
Celebes and farther India, southern Japan, eastern Hindostan, the Seychelles,
southeastern Africa, the African west coast, including Senegambia and Lagos,
Spain, southern Italy, the east coast of South America from British Guiana to
the La Plata River, Panama, Belize, all of Cuba, Jamaica, Haiti, Bermuda,
and all of the southern United States. In vol. iii of his monograph, published
in 1903, he adds certain other localities.

In No. 46, vol. xviii, of the public health reports of the Public Health and
Marine-Hospital Service, published November 13, 1903, and subsequently re-
vised to September 10, 1905, one of the writers (Howard) published a long list
of additional localities. All of these are covered by the general statement of the
distribution given above. All the exact localities observed by us will be found
under the heading of Aédes calopus in the systematic part of this work.

The foregoing consideration of the temperature conditions governing the
breeding of Aédes calopus explain why epidemics of yellow fever have occurred
on the Atlantic coast of North America even as far north as Montreal, and
may again occur, whereas no epidemic has occurred on the Pacific coast, nor
is it possible for one to occur. The summer temperature on the Atlantic coast
is for long periods at or above 80° both day and night, so that the mosquito, once
carried by ship or otherwise from regions of its permanent occurrence, may breed
in large numbers in our cities. It needs then only the introduction of cases of
yellow fever to start an epidemic.

On the Pacific coast, on the other hand, the nights are so cold that the mos-
quito can not survive. It is as regularly imported into Pacific coast ports as into
Atlantic ones. We have records of specimens taken at San Diego and San Fran-
cisco. It breeds permanently in all the west coast Mexican seaports and must be
frequently brought to the Californian coast. Yet it has never been known to
breed there. This seems at first sight strange, since the mean annual tem-
perature of southern California is much above that of eastern cities where epi-
demics have occurred. In San Diego and Los Angeles one sees tropical vege-
294. MOSQUITOES OF NORTH AMERICA

tation on every hand growing unprotected and severe cold is unknown. Yet the
nights are cold, even in summer, and it is to this condition, the low minimum
nightly temperatures, that the freedom from Aédes calopus, and consequently
from yellow-fever epidemics, is due.

ORIGINAL HOME OF AEDES CALOPUS.

The original habitat of this mosquito must clearly be identical with that of
yellow fever, for it is inconceivable that this parasite would have developed in
any other region than the original home of its obligatory host. Early history
points very strongly to the West Indies and adjacent main-land as that home.
Finlay, in a paper read February 19, 1902, before the Pan-American Sanitary
Congress, gave good evidence that yellow fever was endemic in America before
the arrival of the Spaniards. “As may be gathered from the contemporary
chronicles of Las Casas, Oviedo and Herrera, such endemic foci did exist in the
Island of Santo Domingo (Hispaniola) and on the coasts of Venezuela (Nueva
Andalusia) and Colombia (Castilla de Oro) ever since settlements were made
in those places by newly-arrived Spaniards.” The data have been so well pre-
sented in small compass by Marchoux and Simond that we can do no better
than quote them.

“Tt has been much discussed whether Christopher Columbus encountered
yellow fever on his first or on his second voyage. But whether the 39 men left
by the admiral in Santo Domingo fell victims to the disease during the summer
or after the battle of Vega-Real, matters little for the history of this disease.
It is certain that it existed in an endemic state in the Antilles and along the
coasts of the Gulf of Mexico before the discovery of America. It is equally
certain that if the Europeans did not bring yellow fever to the New Continent
they are the ones who, from Central America, have distributed it over the world.
There were amongst them the most numerous victims and the new towns which
were founded in the vast territory which today is the Republic of the United
States had to suffer attacks. In this country alone, more than 100 epidemics
were studied at different points and at different times.

“ From New Orleans the yellow fever spread over the entire lower basin of the
Mississippi and Missouri, even reaching Gallipolis [now Pittsburgh] and
Cincinnati on the Ohio. One can say that it touched all the towns of the east
coast from Florida to the northern frontier, and even to Quebec in Canada. On
the west coast it has been seen as far up as San Francisco. New York was
attacked for the first time in 1688 and had to suffer some twenty great epi-
demics. The yellow fever remained in an endemic condition from 1740 to 1860,
and this was the same with Philadelphia, Charleston and New Orleans. All
the towns of Louisiana, Mobile, Pensacola, Key West, St. Augustine, Savannah,
Baltimore, Norfolk and Boston were thus greatly tried. In fact, according to
what is known, it is in the United States that the yellow fever made its most
frequent incursions. If one estimates at 100,000 the number of deaths of which
it wag the cause, one certainly remains well below the truth.

“Jn South America it rapidly gained the Guianas and Brazil, and we see it
there from 1640. The coast of this vast country, from the Amazons to Rio de
Janeiro, constitutes a still persisting endemic center. From there it has made
frequent incursions to Santos, and sometimes into the states to the southward,
Santa Catharina, Rio Grande, reaching Montevideo and Buenos Ayres, and,
going up the rivers of the La Plata to Assumption in Paraguay. On the west
coast it has spread from Panama to Peru and even to Chili.
EARLY HISTORY OF YELLOW FEVER 295

“Ships, particularly the ships loaded with sugar, have transported this
terrible malady to Africa where we find it in the Canaries after 1701 and perhaps
even after 1510. Besides the Canaries it touched Madeira, the Cape Verde
Islands, Senegal, Gambia, the Bisoagos, Sierra Leone, the Ivory Coast, the Gold
Coast, Benin, Fernando Po, the mouth of the Congo and Angola with Saint
Paul de Loanda. It has caused several epidemics in the island of Ascension
and from this it was carried to St. Helena but without attacking the population
of theisland. At this day it persists as an endemic center in the Sudanese region
comprised between the Gold Coast, the Ivory Coast, the upper Senegal and the
upper Niger.”

After carefully considering the question of the original home of yellow fever,
Sir Rubert Boyce concluded that the disease, and therefore the mosquito, is
indigenous to America. His brief summary of the early history is given.

“There is every reason for supposing that yellow fever is one of the very old
diseases of mankind in the New World. It is stated that it was known to the
Aztecs under the name of matlazahualt, and according to Humboldt it existed
as early as the eleventh century.

“ Amongst old Spanish writers who refer to this disease may be mentioned
Oviedo, who in his ‘ Historia General de las Indias’ describes the great mor-
tality among the followers of Columbus in 1494. This mortality he attributes
to the humidity of St. Domingo, but in every probability it was yellow fever. So
bad were the reports which reached Spain, that Ferdinand V. had to send out
300 convicts to the island as there were no volunteers.

* Columbus in 1498, in writing to the King of Spain upon the sickness of his
men, attributed their illness to ‘ peculiarities in the air and water’ in the new
land. No doubt the peculiarity was the mosquito.

“Jn the sixteenth century yellow fever is said to have decimated the Mexi-
cans. But the first authentic history of an epidemic of yellow fever was fur-
nished by Jean Ferreyra de Rosa at Olinda * in Brazil in the year 1687.

“ Pére Dutertre, 1635, appears to have been the first to furnish details of the
symptoms and progress of the disease in the West Indies. He regarded it as a
new disease.

“ Pére Labat, whose name is well known in connection with yellow fever,
found on landing in Martinique in the year 1649, the disease raging in the
island, the monks of the religious order stationed there being severely afflicted.
The learned father stated that the disease was called ‘the Maladie de Siam,’ be-
cause in Martinique they supposed that it was imported from Siam by the ship
Oriflamme. As, however, this ship called at Brazilian ports on the voyage, it is
much more probable that either the crew became infected there or that infected
mosquitoes were carried away. According to Bancroft the disease existed in St.
Domingo in 1731. ‘Old writers upon yellow fever frequently refer to the West
Coast of Africa as being the original source of the disease.

“Thus Dr. Chisholm believed that yellow fever was first introduced into the
West Indies in 1793, when Grenada became infected from the remarkable ship
Hankey, which had come from Bulam in West Africa. On account of this sup-
posed origin of yellow fever it is sometimes called Bulam fever. Evidence, how-
ever, points the other way,—that in fact it was a very prevalent disease in the
New World, stretching from Mexico down through Central America to Brazil.
Brazil appears, then, to have been the centre from which it radiated out to the
West Indies. As I have stated before, the early Conquistadores suffered from it,
the Latin races of the Old World being therefore the first to make its acquaint-

 

* Now a suburb of Pernambuco.—Editors.
296 MOSQUITOES OF NORTH AMERICA

ance during the time they were occupied in pushing civilization into the then
newly discovered continent.

“In Cuba yellow fever was probably known as the Pest or Epidemic of
Havana as early as 1620. The first authentic description of the black vomit in
Havana was furnished by Dr. Thomas Romay in the year 1761.

“In the beginning of the eighteenth century the disease, from its appearance
in various parts of Spanish America under the name of vomito prieto, attracted
much attention, and it is particularly referred to by the historian Ulloa, who
resided for some years in that country. The word prieto appears to be the Portu-
guese or nearly obsolete Spanish term for black. In Spanish the word negro
is now universally substituted. A small pamphlet of sixty-two pages by a Dr.
Gastelbondo, written at Carthagena (S. A.) in 1753 and printed at Madrid in
1755, was probably the first work ex professo on the black vomit as it appeared
in South America. He gives his experience of the disease during forty years.
He says on the title page that he is about to write about a disease of frequent oc-
currence in that part of the world, mentions change of climate and mode of living
among some of the causes of the disease in new-comers, and says that the natives
of Carthagena, Vera Cruz, etc., were not subject to attacks of the true black
vomit fever, though liable to the ‘ Chapetonada,’ a disease resembling it in some
respects.”

It has been claimed by some that yellow fever is of African origin and was
imported into America through the slave trade. The most comprehensive argu-
ment in favor of the African origin of the yellow-fever mosquito is given by
Goeldi and on that account we give it here in full.

“T am well acquainted with the arguments of those authors who claim that
stegomyia is of American origin. They are based chiefly on the story of the
voyage of Christopher Columbus. Without disputing whether the disease which
killed a part of the crew of the caravels of the conquerors was indeed identical
with yellow fever, does this in itself amount to a positive proof that this dis-
ease did not previously exist on the coast of Africa? Most certainly not. At
most it might be objected that no historical documents exist relating to the
existence of stegomyia in Africa before Columbus. Further, from the absence
of any historic document about any given fact there never can be deduced the
non-existence of this fact. There are evidently many things which happened in
this sublunary world of which no human historian has left us a story and which
nevertheless are most certainly true.

“Let us examine this question a little more closely. Stegomyia fasciata is,
as we know, a mosquito which affects great cities, populous centers of the shore
and neighboring regions. Now, I ask where were these great cities which the
European invaders should have found along the Atlantic coast from the Antilles
even down to the Rio dela Plata? Where are those points where the indigenous
Americans were found in populous permanent residences? There were none,
and this in no wise surprises us, considering the habits and customs of the
Indians. The indigenous American was at all times that which he is today ;
endowed with the love of liberty, he never had the habit or even the tendency
to group and concentrate himself in really considerable collective residences.
His village consisted of a few dozen houses—in most cases not even one hundred
being found in a limited area. They were peasants rather than townspeople;
as with ants and bees, an increase of numbers always produced for them as a
consequence migration of groups, dismemberment—a new village was formed,
half a day, a day, or two days further up the river, further down the river,
further in the forest, and this in turn became disintegrated in view of the rest-
CLAIMS FOR OLD WORLD ORIGIN 297

less und nomadic character of the Indian long before it could have acquired any
considerable increment or dimensions, They are not properly sociable in their
dwelling places: if among them the social spirit exists it merely shows itself
at the time of feasts, of warlike enterprises or of great migrations, etc. During
transitory and passing occasions there are indeed agglomerations of people, but
inchoate, ready to break up, and their camps can not even be called temporary.
The occasion over, the multitude dissolves itself as by enchantment or before
re i of the wind. Now such conditions are not to the taste of Stegomyia
asciata.

“On the other hand, what do we find in Africa? One of the most striking
ethnological characteristics of the black people is precisely the social spirit
strongly developed. In the stories of all travelers we find at every moment ex-
pressions of surprise and admiration as to the grouping of houses, attaining
numerical dimensions so great as to prevent a rapid census. In that country
there are frequently found centers of ten, fifteen or twenty thousand inhabi-
tants, and yet these are barely called villages; in Africa the idea of a city is only
given consideration with such centers as possess a multiple of the above figures.
Here we have the condition of affairs that admirably meets that which stego-
myia wants and demands. It is the very best condition for its life requirements:
a hot and humid climate and very large groups of human beings.

“ All I wish to set down in brief words is that a careful comparison of the
ethnological situation there and here—and this certainly constitutes a factor
of the utmost importance in the matter—at once demonstrates the indubitable
advantage on the side of the African origin of Stegomyia fasciata.

“ Another series of considerations which in the highest degree tend to upset
the theory, so weak in its basis, of the American origin of Stegomyia fasciata,
are opened up as soon as we weigh the results obtained by a critical examination
of the partnership, Stegomyia fasciata—Culex fatigans. In a previous essay I
frequently and persistently pointed out that these two mosquitoes are inseparable
companions all over the world, and I demonstrated that, one a diurnal and the
other a nocturnal mosquito, they together formed a partnership admirably or-
ganized to take in daily cyclic rotation tribute from man in the tropical zone.

“Now it is worth while noting that the type specimen, the original which
served for the first description of Culex fatigans by Wiedemann in 1828, came
from the oriental Indies. This circumstance, if indeed by itself alone it does not
amount to proof, is nevertheless of no small symptomatic importance.

“Task this: Does this ominous partnership of Stegomyia fasciata and Culex
fatigans date from yesterday? Is it perhaps an accidental result in the tropical
part of the New World? I believe that it is of a date much further back, and
that we must find the locality where the pact was celebrated in some part of the
Old World, and that it was not accidental but the natural consequence of an
almost identity of common interests.

“T believe that there are good arguments indicating an Hthiopic-Indian
nativity of this alliance, and the more I examine it the more it seems desirable
to me that there should be a conscientious and critical investigation undertaken
into the question of an eventual parallelism between the distribution and dis-
persion in ancient and modern times, of the black human race on the one hand,
and of the two mosquito partners in their damnable offensive alliance on the
other hand.

“Tt is indispensable not to lose sight of the fact that he would be ill-advised
who would permit himself to be impressed and influenced one-sidedly and par-
tially by the aspect which things present today in this field. Do you wish an
example? It is not necessary to go far to find a most drastic one. Brazil today
is the greatest producer of coffee and undoubtedly is the country where the
298 MOSQUITOES OF NORTH AMERICA

greatest number of coffee trees have been planted. Now suppose for a moment
that there was a complete disappearance of all historical documents proving the
Asiatic origin of the coffee plant and of its introduction into Brazil via Cayenne,
who would imagine that the original country of this tree was Arabia? And is
it not an absolute fact that this very historical remembrance is becoming weaker
every day in popular knowledge here in Brazil with the increasing interval of
time separating us from the moment of introduction which nevertheless was
scarcely 200 years ago?”

One of the authors (Knab) has already pointed out some of the weaknesses in
Goeldi’s argument. He showed that Goeldi is in error where he denies the
existence of large cities in America at the time of its discovery. The vast
centers of population found by the Spanish conquerors in Mexico and Yucatan
are too familiar to need discussion. Even the Amazons themselves, if we can
believe the early explorers, had large towns upon their shores and supported a
considerable population. Moreover it must be remembered that Africa is for
the most part a dry, open country in which a mosquito with the habits of Aédes
calopus could hardly originate and find opportunities to adapt itself to man.
On the other hand in tropical America the ideal conditions exist which would
bring about the adjustment of such a mosquito to man. We find extensive
forests and plenty of moisture to support tree-hole breeding mosquitoes and
human settlements within these forests to furnish the blood supply. In fact
we find in this region a great variety of mosquitoes which have the tree-hole
breeding habit; among these are some which clearly show a predilection for the
proximity of man and may thus be said to be in progress of developing do-
mesticity in the manner it must have been done by calopus.

Had yellow fever existed in Africa prior to the discovery of America we would
surely have had some indication of it through the earlier explorers, but nothing
exists to warrant such a belief. The distribution of yellow fever in Africa, as has
been recently set forth anew by Boyce, is in itself significant. It has there been
confined to spots in a restricted area on the west coast, the part nearest America
and formerly most in communication with it through the slave trade. This is
well brought out by Prof. W. J. Simpson, in his discussion of the paper just
mentioned, by Boyce. It is hardly conceivable, had yellow fever been endemic
in Africa for a long time, that it could have failed to spread, not only over the
hotter parts of the continent, but even to the Hast Indies. Finally the experi-
ments of Marchoux and Simond, given on a previous page, which indicate a
certain repugnance to the black race, while not in themselves conclusive, in con-
nection with the foregoing, are at least significant.

DISTRIBUTION BY ARTIFICIAL MEANS.

It seems worth while to give some practical account, in the light of our present
knowledge, of the way in which the yellow-fever mosquito is distributed by the
presentation of specific cases. To illustrate shipboard carriage the story of the
case of the steamer Luzor and its journey in the spring of 1906 may be de-
scribed as follows:
DISPERSAL THROUGH TRANSPORTATION 299

In Public Health Reports, vol. 21, no. 23, published July 8, 1906, there is
an interesting report from Surgeon Wightman, of the Public Health and
Marine-Hospital Service, dated May 5th, in which he states that the steamer
Luxor left San Francisco February 9th and proceeded to Guayaquil via Mexican
and Central American ports, leaving Corinto, the last Central American port,
on March 7th. She also called at four South American ports north of Guayaquil.
No mosquitoes were seen on board in any of these ports except at Corinto, and
these did not stay with the vessel after leaving port. The Luzor reached the
quarantine station at Guayaquil at 9 a. m. on March 18th, passed inspection,
and passed up the river, anchoring a few hundred yards from the city. She
carried a cargo of lumber forward and aft; that aft was discharged, but forward,
near the forecastle, it remained on deck, was wetted with rain and formed a
hiding-place for mosquitoes. Large numbers of mosquitoes came on board.
Anopheles was recognized, but not Aédes calopus. The vessel remained four
days and five nights, leaving March 23d. She arrived at Pieta, Peru, at 11 a. m.,
March 24th, and the holds were fumigated lightly. No mosquitoes came on
board. She sailed that night for Callao, and a few active mosquitoes were seen
on board. The steamer arrived at Callao at 4 a.m., March 27th. All the crew
passed inspection, but were told to expect detention until the 29th. The work of
discharging the cargo, including the lumber on the forward deck, was begun.
March 27th, at 6 p. m., that is four days and fifteen minutes after leaving Guaya-
quil, a fireman was reported sick. The case was not reported to the authorities
until the 29th, when yellow fever was diagnosed and the patient removed to
a quarantine ship. The same night the second forecastle and second and third-
class quarters were fumigated and kept closed for 24 hours. The next morning
a second case developed, and April 1st the remaining portions of the vessel were
fumigated. April 4th a third case was reported, and a fourth case developed
April 7th. The whole vessel was fumigated throughout. April 8th the fifth
case developed. The first, third and fifth cases died, the last death occurring
April 11th. The vessel was ordered south to a colder climate by the Peruvian
authorities, and the subsequent history was good. None of the people aft were
infected.

Doctor Wightman concluded that the insects probably gained access to the
vessel in the covered lighters rather than by flying; that the fire room, usually
regarded by seafaring men as never infested with mosquitoes, is under grave
suspicion; that the futility of partial fumigation is plain—even the life-boats
should receive attention ; that there is danger of harboring these insects in deck
cargo, and that possibly calopus may be present on a ship without detection,
even when carefully searched for.

We have indicated, in the section on the carriages of mosquitoes by railroads,
ships and other conveyances, that the yellow-fever mosquito is frequently carried
in the summer time by railway trains and ships far beyond its permanent habitat,
and that even in these abnormal! locations such mosquitoes escaping from trains
or ships may, in the warm weather, find suitable breeding-places and produce
one or more generations of adults. This process is going on every summer in
300 MOSQUITOES OF NORTH AMERICA

the United States. Yellow-fever mosquitoes are being brought north of their
normal range, escape from their conveyances, find breeding-places, and breed,
and it is only necessary that a case of yellow fever be brought to them to enable
them to become infected and to start an epidemic. Thus in St. Louis in the
year of the Exposition (1904), train service from the south was especially
efficient, and loaded cars came quite to the Exposition gates. Yellow-fever
mosquitoes had probably escaped from these cars and bred on the Exposition
grounds, as they were found there in August by Mr. A. Busck, of the Bureau of
Entomology, who was stationed at the Exposition in charge of the exhibits of
the Bureau.

As has also been pointed out in the section on carriage of mosquitoes by con-
veyances, the yellow-fever mosquito has actually extended its permanent range
along the railroad running from Vera Cruz up to the City of Mexico by means
of railway trains, establishing itself at places where it did not formerly occur,
but in which, having the conditions of the moist tropical or moist Lower Austral
Zone, it has succeeded in establishing itself in a permanent way. One of the
writers’ (Howard) observations in 1905, as mentioned in the previous section
referred to, were confirmed by the Report of Working Party No. 1 of the Public
Health and Marine-Hospital Service, and the following quotation is from this
report:

“ Habitat.—This mosquito is widely distributed, probably more so than any
other species, being found throughout the tropical world and well up into the
temperate zone. At one time it was supposed to be a coast mosquito, but now it
is found to have spread along the commercial lines of communication to cities
in the interior that furnish receptacles for breeding places. Its acclimation to
the altitudes is gradual, as may be illustrated by the following example:

“ About twenty-eight years ago a railroad was constructed connecting Vera
Cruz with the City of Mexico. Some years later a competing line was built be-
tween these cities, but going through a different part of the country. Along the
line of the Mexican Railroad yellow fever was unknown in the interior. During
the construction of the railroad the disease prevailed among the employees until
the road reached the foothills ; it then disappeared. About nine years ago yellow
fever appeared in Cordoba at about an altitude of 3000 feet, and has since been
epidemic. Three years ago yellow fever appeared at Orizaba and this year
(1902) there was a severe epidemic in that city. Since the construction of the
railroad many cases of the disease had been received during sickness and con-
valescence, and many cases have developed among strangers going through Vera
Cruz to that city without the disease in any way affecting the general health of
the community, until three years ago.

“In the second instance, along the line of the Interoceanic Railroad we know
by actual observation that the Stegomyia fasciata has been ascending from
station to station until it has now reached Carasal at an altitude of about 3000
feet. Synchronously with the ascent of this mosquito yellow fever became epi-
demic in those places. El Palmar, the next station above Carasal, about 8 miles
distant, does not harbor any of these insects at the present time, and though
some cases were sent there from the latter station this last year, there was no
spread of the infection. Jalapa, a city of about 35,000 inhabitants, at an altitude
of about 4500 feet and about 20 miles above Carasal, does not harbor the Stego-
myia fasciata, and though cases have been sent to that place for years from Vera
Cruz and intermediate stations, there has never been any spread of the disease.
IMPORTATION OF AEDES CALOPUS 301

“Tt will be seen in these instances that the ascent of yellow fever and the
advent of the Stegomyia fasciata have gone hand in hand until they have now
reached an altitude of 4200 feet in the first instance and 3000 feet in the
second. This is the first authentic record we have of yellow fever reaching such
an altitude and is another proof that, the proper conditions supplied, the dis-
ease and the insect can be introduced and cause the same destruction of life as
in more tropical regions. The distribution of this insect in our southern States
has already been dwelt upon.”

In an interesting article on mosquito work in Khartoum, published in the
first report of the Wellcome Research Laboratories, Balfour states that calopus
breeds in Khartoum though not to any great extent. He believes that its preva-
lence is due to the steamers on the Blue Nile. Together with Culex quinque-
fasciatus, it has been found breeding in large numbers in the bilge water, tank
water and engine-room water of the river steamers. He believes that by this
means these two species have been introduced into the towns along the upper
Nile.

THE YELLOW-FEVER MOSQUITO IN EUROPE.

The yellow-fever mosquito appears to be well established in southern Europe.
Meigen’s description of Culex calopus was based on a specimen from Portugal—
probably the city of Oporto—and shows that the species was established there
before 1818. Ficalbi, who redescribed the insect under the name Culex elegans
reports it from Pisa, Leghorn (Livorno), Florence and Naples, and the islands
of Sicily and Sardinia. He was well aware of its habits and stated that it is
not generally distributed and noted its absence from Sienna and Ravenna. Theo-
bald reports it from Gibraltar, from Poros in Greece and Larnaka in Cyprus.
We have specimens from Naples and Malaga. In Europe, as elsewhere, the cli-
matic conditions previously set forth will limit its permanent habitat.

There can be little doubt that the yellow-fever mosquito was brought to
Europe by the early Spanish conquerors, perhaps by Columbus himself. The
long voyage, necessitating a large water supply, kept in a primitive way, gave
ample opportunity for the mosquito to propagate en route. We have an excel-
lent description of such a case in the account of Captain Godeheu de Riville,
already mentioned on a previous page.

Under modern conditions the danger of introduction of the yellow-fever mos-
quito into other parts of Europe is very greatly reduced. The rapidity of the
voyage is more than offset by the lack of breeding facilities on modern ships.
Nevertheless the introduction of Aédes calopus, and with it of yellow fever, into
the more northerly portions of Europe, has occurred repeatedly within compara-
tively recent times. As recently as 1908 there was a small outbreak of yellow
fever at the French port of Saint Nazaire with eleven cases, seven of which
terminated fatally. The ship “ La France” had been en route from Martinique
from September 11 to 24 and no cases had developed on board. As the pre-
scribed period of nine days since leaving port had been passed the ship was
admitted without quarantine. Soon after unloading began yellow fever ap-
peared among the crew; a journalist, who had visited the ship, and a seaman of
302 MOSQUITOES OF NORTH AMERICA

a nearby ship were also stricken. Yellow-fever mosquitoes were found on the
ship but apparently there were none on shore and the disease did not spread.

A short account of the importations and outbreaks of yellow fever which have
occurred in past years in Europe is published by Dr. J. M. Eager in a series of
pamphlets of the Yellow-Fever Institute (U. S. Marine-Hospital Service) Bul-
letins Nos. 3, 4, 5 and 8. All are traced to vessels coming directly from the
West Indies or South America. In many instances (all of those in Great
Britain) the cases were confined to members of the crews of the vessels, the
climatic conditions having been unfavorable to the propagation of the disease
and the necessary species of mosquito absent. In the cases where there was an
outbreak, as in ports in Italy and southern France, these are exactly comparable
to the outbreaks that have occurred in former years in the northern cities in the
United States. They were summer outbreaks, ceasing on the appearance of
winter, and started by the carriage of infected mosquitoes, or the arrival of
persons in the infective stage of the disease at a suitable season from regions of
permanent establishment.

Some recent very interesting observations have been made in the actual carry-
ing of living calopus from Brazil to Europe, and the conditions under which
they will exist in two portions of Europe have been studied.

Otto and Neumann, in their account of their expedition to Brazil under the
auspices of Hamburg merchants, to study the sanitary conditions of the Bra-
zilian ports, brought back with them to Hamburg living adults of calopus which
they fed on the journey from a canary and from white rats. On arrival at Ham-
burg they found that even in the summer time calopus is not able to breed in
the open air for a full generation, although they succeeded in breeding them at
an artificial temperature of 27° C., and also in the ordinary temperature of the
houses. They found that cold killed them rapidly. At zero (C.), they died
instantly ; at 4° they lived only an hour, and lived for 82 days at a temperature
of from 7° to 9°. They found that eggs preserved dry did not hatch after eight
days. When they were kept at 27° they would still, at the end of twelve days,
give birth to larva. As with the eggs, the perfect insects live longest at an
even temperature of about 27°.

Marchoux and Simond brought calopus adults with them from Brazil to
France. They took 20 females and 20 males, isolating them in rearing tubes
immediately after their transformations on the 15th of February some time
before their departure from Rio. During the voyage they were fed on glucose.
On arrival in France the 5th of May, 17 females and 9 males were alive. In
France they reared five generations at the ordinary temperature, the eggs of the
last hatching in September. The larve of this last generation lived until the
middle of October without transforming. Some of them, however, gave perfect
insects a little later, and these were kept until the 10th of November by feeding
on glucose. One female of this generation, taking a meal of blood, laid 60 eggs
which did not hatch. All adults died early in November.

This experiment, carried on through six months of the warm season of the
French climate, showed that the yellow-fever mosquito can breed for four or
DENGUE AND MOSQUITOES 303

five generations in France under conditions that exist about houses, but the
German experiments show that it is unlikely that this species can produce even
a generation under the natural conditions of the climate at Hamburg.

DENGUE.

This disease frequently appears in epidemic form throughout the tropics and
subtropical regions. It is marked by sudden appearance, acute fever, short
duration and comparative benignity, fatal cases being extremely rare. Dengue
has been confused with influenza and various febrile diseases and its existence
as a disease entity has even been denied. However, it is now generally recog-
nized as a specific disease. Considering the fact that dengue has been com-
paratively little studied, its mosquito-born character may be said to be fairly
well established. Ashburn and Craig point out that attention has been directed
repeatedly to the resemblance between dengue and yellow fever and that it is
well founded in fact. Craig has recently shown, as will be seen in the following,
that, like yellow fever, this disease is caused by an organism of ultra-microscopic
size, almost certainly a protozoan and closely related to the causative organism
of yellow fever.

Harris Graham, of Beirut, in 1902, was the first to point out that dengue is
not contagious, but is due solely to the agency of mosquitoes. In a second paper,
in 1903, he specified the common house-mosquito of the tropics (Culex quin-
quefasciatus) as the responsible species and this has been experimentally con-
firmed by some of the later investigators.

Graham was led to investigate the possibility of mosquito agency in the
propagation of dengue through the fact that at Beirut, where there was a very
extensive epidemic, mosquitoes were excessively abundant, while certain high
and dry mountain villages where there were no mosquitoes remained free from
the disease. From the previous history of the disease he made the following
deductions:

“There is great multiplicity of evidence to show that it does not spread to any
extent when carried away from certain low-lying regions, which are its favorite
abode. Epidemics in Cuba, Jamaica, Hast Indies, Réunion, Martinique, and
Madagascar, all seem to show that, in spite of the most active communication,
dengue cannot spread to any extent when carried into dry and high places in the
interior. These epidemics have shown time and again that people come down
from these higher and drier places, contract the disease, and then have it break
out on them in their homes to which they have returned, and there lie smitten
with it for several days without the other inmates of the household catching it.”

Graham went to work to prove experimentally the transfer of dengue by mos-
quitoes. A mother suckling her child became ill with dengue. As soon as the
diagnosis was made, wire screens were put in all the windows of the house, and
the mosquitoes in the interior were all destroyed. These precautions were con-
tinued until the 10th day after recovery. The infant did not cease to nurse and
remained constantly in its mother’s arms, yet it did not take the disease. In
another case one of four children was attacked by the disease. The room was
304. MOSQUITOES OF NORTH AMERICA

kept free from mosquitoes for 13 days. Its three brothers continued to play
with it during the day and to sleep with it under the same bed-covering, and
none of them contracted the sickness. In a third experiment the head of a
family contracted the disease in the city and was willing to submit to Graham’s
instructions to protect his wife and children. The same method was followed as
in the previous experiments. The rooms were kept as free from mosquitoes as
possible for 17 days, and although the man had a severe attack, lasting five days,
none of his family were taken ill. Several other experiments had to be aban-
doned because, through carelessness, mosquitoes had gained access to the rooms.

Graham then sought more positive proof and tried to inoculate the dengue
fever by the bite of infected mosquitoes. Four persons volunteered for the ex-
periment. “In each case several mosquitoes were taken from the netting of
patients sick with the fever and put inside the netting of the candidate for the
disease, he sleeping night after night with the mosquito in the netting.” The
four volunteers were placed in a house where, for a long time, there had been no
sickness. They were forbidden to leave the house, or to receive any visitors.
Three of them came down with the dengue in from 4 to 6 days. The fourth one
passed about 15 nights with the infected mosquitoes without developing the dis-
ease; but three years before he had had a violent attack of dengue and it would
seem had been thus made immune. Still Graham was not entirely satisfied that
this experiment would be accepted as conclusive. He therefore conducted an-
other experiment which eliminated as far as possible the chances of error.

“In a city where so infectious a disease was raging I still felt that these three
men might have received the contagion in some other way. In order to avoid
this objection mosquitoes were taken from inside the netting of a dengue patient
and carried up to a village on the mountain slope where as yet no case had
occurred. After visiting my patient for the infected mosquitoes I changed my
clothing and took a bath before mounting my horse to ascend the mountain.
In this village, about 3000 feet above the sea, there are almost no mosquitoes.
It is dry and very healthy. I easily found two young men in different parts of
the village who consented for a consideration to take their chances of having the
dengue. One of them, after sleeping four nights under the netting with the
mosquitoes, was taken with a severe typical attack of dengue. The other had
his initial chill after having passed five nights in the company of the mos-
quitoes. These men continued to sleep under the mosquito nettings I had pre-
pared for them until some time after they were well, all the mosquitoes in the
netting having been killed to avoid infection of other people. No other cases of
dengue occurred in this village during the summer that I could learn of, al-
though I made the most careful inquiry.”

Bancroft, in Australia, suspected the transmission of dengue by the yellow-
fever mosquito, Aédes calopus. Ashburn and Craig experimented on the mos-
quito-transmission of dengue at Fort William McKinley near Manila. Their
experiments with Aédes calopus resulted entirely negatively. With Culex quin-
quefasciatus they succeeded in producing a typical attack, the mosquitoes em-
ployed by them having been reared from the eggs and allowed to bite a patient
with a well-marked case of dengue.
DENGUE CONTROLLED THROUGH MOSQUITOES 305

The idea that Aédes calopus is concerned in the transmission of dengue has
been revived again recently by J. Legendre. He describes an epidemic of dengue
at Hanoi during July, August, and September, extending lightly into October,
with an occasional isolated case in November. The role of Aédes calopus in
the transmission of dengue appeared justified to him, on account of the fact
that the epidemiology is an exact reproduction of that of yellow fever. He states
that A. calopus bit frequently during the duration of the epidemic and that other
culicids were rare during the same period. He argued that the malady stopped
at a time when the Aédes calopus became rare. Moreover other biting insects,
possibly capable of transmitting the disease, were absent. He offered no experi-
mental evidence but the assemblage of facts appeared to him quite sufficient
to attract serious attention. To the argument of Legendre the criticism must be
made that his general observations can not be accepted against the positive work
of Graham and of Ashburn and Craig. It must be pointed out that wherever
Aédes calopus is abundant Culex quinquefasciatus is nearly always equally so,
relieving the former at night; it would be very strange if such a widely dis-
tributed mosquito were absent from Hanoi. Furthermore many of Legendre’s
observations on the habits of Aédes calopus do not apply to that species and this
makes it practically certain that most of the mosquitoes present belonged to other
species, probably mostly Culex quinquefasciatus. The mosquitoes mentioned by
him as being so abundant early in the season are undoubtedly species of Aédes,
similar in habits to those which develop with us in the snow water of early spring
and which we have discussed in the chapter on habits of mosquitoes in general.

E. H. Ross gives convincing evidence that mosquitoes are a necessary factor
in the transmission of dengue. He shows that in Egypt, since the towns of
Port Said and Ismailia have been rid of mosquitoes they have escaped the epi-
demics of dengue which have invaded the rest of the country.

“Dengue fever used to be very prevalent in Port Said, as in other parts of
Egypt, up to the year 1905. An epidemic of the disease occurred in the town
during the summer of 1904, and in the spring of 1905. This epidemic was part
of an infection of all the towns of Egypt, and was most severe. The hospitals
were full of cases, and patients actually contracted the disease in them. In
Port Said almost everyone suffered from an attack, and the place was regarded
as fever-stricken and unhealthy. The town was full of mosquitoes, including
two species of Anophelines, Culex fatigans and Stegomyia spp., in abundance.
These mosquitoes were breeding in cess-pools under the houses, in basement
cellars flooded with sewage, garden fountains, barrels containing water, and
were a veritable pest day and night, summer and winter.”

In May, 1906, a campaign against mosquitoes was launched and with the mos-
quitoes dengue has disappeared also.

“ During the early part of that year, before the mosquito work began, dengue
fever made its appearance as usual. Thirteen cases were treated in the hospital
alone during April and May, and then as the mosquitoes disappeared the dis-
ease stopped and has not recurred since. In September, 1906, a severe epidemic
raged throughout Egypt, beginning at Assouan and running tife in Cairo and
Alexandria. It appeared in all the other towns, but Port Said and Ismailia re-
mained free from it, no case occurring at either place. During the autumn of
306 MOSQUITOES OF NORTH AMERICA

1907 it again passed through Cairo and other parts of Egypt, but again Ismailia
and Port Said escaped. Formerly the wards of the hospital in this town were
full of cases of ‘fever’ during the summer months, but now the beds are used
for other cases, which no longer contract fever although the mosquito nets have

been removed.”

Balfour shows that much the same conditions govern the spread of dengue in
the Sudan. Thus an epidemic made its appearance in 1906 at Halfa, Port
Sudan and elsewhere. Khartoum, however, did not have a single case of dengue
and Balfour points to the scarcity of mosquitoes at this place, particularly of
Culex quinquefasciatus, as the probable reason.

An hematozoan, which he compared to the Plasmodium of malaria, was
found by Dr. Graham and considered by him to be the causative organism.
Other observers have failed to find this organism and have on that account re-
jected his observations and conclusions. However, as we have seen above, his
observations and deductions on the mosquito-transmission of the disease are
confirmed by a number of workers. Bancroft considered that the causative
organism of dengue is similar to that of yellow fever in respect to its ultra-
microscopic size.

Craig has recently discussed dengue in connection with yellow fever and with
the so-called pappataci fever, this last being transmitted by a minute biting fly
of the genus Flebotomus, family Psychodide. He shows the close relationship
of the three diseases and points out that they are most probably due to very
similar organisms, ultra-microscopic in size and in all probability protozoan.
The substance of Craig’s discussion, based upon the investigation by Ashburn
and himself, follows herewith.

“ After a thorough examination of the blood of numerous patients with
dengue we concluded that it did not contain any visible organism either bacterial
or protozoal in nature, which could be considered as the cause of the disease.
Our attempts at securing blood cultures also resulted negatively and in order to
determine whether the cause of this fever was present in the blood we were
forced to attempt the production of the disease by the inoculation of the blood
from dengue patients into healthy individuals. As the disease is one which in
the young and robust is not dangerous to life, we felt justified in making such
experiments, and had no difficulty in procuring volunteers for this purpose.

“We first undertook to study the effect of the intravenous inoculation of
unfiltered dengue blood. Eleven men were inoculated, and in seven a typical
attack of the disease developed, while one case was doubtful. . . .

“These experiments proved beyond question that the cause of dengue is
present in the blood of infected individuals, as the intravenous inoculation of
such blood in healthy men is capable of producing a typical attack of the disease.

“ As our examinations had proved that it was impossible to demonstrate a
parasite in the blood we concluded that it must belong to the class of so called
ultramicroscopie organisms and in order to determine this point we inoculated
two healthy individuals with filtered blood from dengue patients, with the re-
sult that severe attacks were produced in both men. In our filtration experi-
ments we employed a Lilliput filter which was tested and controlled each time it
was used, and the filtration was done under 730 millimetres pressure. After
filtration a control test was made of the filter by using a bouillon suspension of
Micrococcus melitensis, the filtrate then being incubated for two weeks, and
FILARIA PARASITES 307

examined every day. The filter we used retained this organism, so that it may
be stated that the virus of dengue passed through the pores of a filter which
prevented the passage of an organism measuring 0.4 micra in diameter. The
blood from the dengue patients was defibrinated and diluted with an equal
amount of normal salt solution, and the filtrate was introduced intravenously.

“Tn both of the men inoculated with the filtrate the attack was of severe
character, and we regarded these two cases of dengue, produced by the intra-
venous injection of filtered dengue blood, as the most typical cases of the severe
type of the disease which we observed. These experiments proved that the
organism causing the disease is probably ultramicroscopic in size, and this con-
clusion explains the uniformly negative results obtained in the search for the
parasite.

“We concluded that an organism was present in the filtrate, rather than a
toxine, because of the length of the period intervening between inoculation and
the appearance of clinical symptoms, and also because one of the men was in-
oculated with the filtered blood of an experimental case of dengue produced by
the intravenous injection of unfiltered blood from a naturally infected dengue
patient.” ...

“ Owing to the subsidence of the epidemic we were unable to continue our
mosquito experiments, which are therefore incomplete, but, taken in connection
with those of Graham, prove that this disease may be transmitted by the mos-
quito. We felt justified in concluding that this method of transmission is the
only natural one which has been proved by experiment, and which agrees with
the epidemiology of the disease.

“We were further able to show experimentally that natural immunity exists
against this disease, and that it is not contagious. We exposed eight healthy
men to fomites, the men experimented with living in mosquito proof tents with
patients suffering from dengue, throughout the entire course of the disease.
They slept in their beds, wore their underclothing and pajamas, and ate and
drank from the same table furniture, but none of them developed the disease.

“ Our conclusions regarding the etiology of dengue were partly to follows:

“1. No organism, either bacterium or protozoan, can be demonstrated in
either fresh or stained specimens of dengue blood with the microscope.

“2. The intravenous inoculation of unfiltered dengue blood into healthy men
is followed by a typical attack of the disease.

“3. The intravenous inoculation of filtered dengue blood into healthy men
is followed by a typical attack of the disease.

“4. The cause of the disease is, therefore, probably ultramicroscopic.

“5. Dengue can be transmitted by the mosquito, Culex fatigans Wied. and
this is probably the most common method of transmission.

“6. No organism of etiological significance occurred in bouillon or citrated
blood cultures.

“1, The period of incubation in experimental dengue averages three days
and fourteen hours.

“8 > Certain individuals are absolutely immune to dengue, as proved by our
experiments. . . edi ee

“9. Dengue is not a contagious disease, but is infectious in the same manner
as is yellow fever and malaria.”

FILARIASIS.

Under this name is understood the presence in the blood or other body fluids
(the lymph and urine) of nematode worms belonging to the family Filariide.
These worms are present in man and in other vertebrates in two stages, as adult

21
308 MOSQUITOES OF NORTH AMERICA

worms and as larve or so-called microfilarize. The adult filarize are found in
the lymphatic vessels or in the connective tissues in various parts of the body.
The two sexes are usually associated, coiled about each other, and sometimes
several are coiled together. The larvee to which the female worm gives birth
find their way, in large numbers, into the blood and sometimes into the urine.
Man is the host of several species of Filaria, and, as in the case of the malarial
organisms, more than one of these may be present in the same individual.

Only one species of Filaria is of marked pathological importance. This is
Filaria bancrofti, also frequently designated as Filaria (or Microfilaria) noc-
turna or Filaria sanguinis-hominis. The presence of this parasite does not
necessarily produce sickness; in fact it is well known that the filarie are often
present without the host showing any symptoms and they are only detected when
the blood is examined. However, a series of pathologic conditions are produced
by the presence of filaris in man, which, while they are seldom directly fatal, in-
capacitate to a greater or less degree. Manson, who is probably the best
authority on filariasis, gives as the result of the parasitism of Filaria bancrofti
in man the following filarial diseases:

“ Abscess; lymphangitis; varicose groin glands; varicose axillary glands;
lymph scrotum; cutaneous and deep lymphatic varix; orchitis; chyluria; ele-
phantiasis of the leg, scrotum, vulva, arm, mamma, and elsewhere; chylous
dropsy of the tunica vaginalis; chylous ascites; chylous diarrhoea, and probably
other forms of disease depending on obstruction or varicosity of the lymphatics,
or on death of the parent filarie.”

Filariasis is a widely distributed disease in tropical and subtropical regions
and is especially common on the west coast of Africa, in South China, certain
parts of India and some of the islands of the Pacific. In certain islands of the
Society and Tonga groups, according to some observers, fully 70 per cent of the
population are afflicted with filariasis. In America it is very prevalent in the
West Indies. Dr. Mario G. Lebredo, in a recent paper, states that in the city of
Havana he found 17.82 per cent of filaria infection. He points out its dangerous
character and that there is reason to fear its general spread unless effective con-
trol measures are adopted. In the United States cases are occasionally found
in the Southern States and isolated cases occur further north, but it can not be
considered endemic. The forms of the disease appear to vary considerably ac-
cording to locality and on this account the belief has been expressed that more
than one species of Filaria is included under the name Filaria bancrofti.

TRANSMISSION BY MOSQUITOES.

The suggestion that mosquitoes are probably the carriers from man to man
of at least one of the parasitic worms of the genus Filaria, in one stage or
another, apparently was made about the same time by Bancroft, in Australia,
and Manson, in China. The evidence was first gained by Manson about 1878,
who thus became the discoverer of the first recognized transfer of a disease or-
ganism by mosquitoes. Manson found that mosquitoes which feed upon filarial
blood become infected and that the filarie undergo a metamorphosis within the
FILARIA EMBRYOS IN BLOOD 309

body of the mosquito. The actual mode of transmission from the mosquito to
man remained unknown for a long time and gave rise to a variety of conjectures.
It has been determined only within the last few years. as we shall see farther on.
The relation of the human parasites of this genus to mosquitoes has been es-
tablished for several species, although there seems to be some confusion from the
difficulty of always identifying with certainty the larval filarie. The species
concerned are: Filaria bancrofti, F. perstans, F. demarquayi and F. philip-
pinensis. With other species of Filaria investigations and experiments with
mosquitoes have been entirely negative and these are supposed to have some
other blood-sucking arthropod for an intermediate host. In addition to certain
human filariz the transmission by the mosquito has also been proved for Filaria
immitis of the dog.

THE FILARIAL WORMS.

The adult filarie are long, thread-like, transparent worms. The female is con-
siderably larger than the male. In Filaria bancrofti the female measures from
85-90 mm. (33-4;% inches) in length by 0.24-0.25 mm. in diameter; the male
measures about 40 mm. (1f in.) in length and 0.1 mm. in diameter.

The adults of Filaria bancrofti, as already stated, live in the lymphatics or in
the connective tissues of different parts of the body of human beings; the two
sexes are often side by side, or a number of individuals are associated, and they
are capable of living there for a long time. When present in the lymphatic
vessels they may produce serious pathologic conditions, caused, according to
Manson, by obstructing at certain points the flow of the lymph. This accumu-
lates and dilates the vessels and lymphatic spaces, and this mechanical dis-
tension is accompanied by an irritation of the vessels and of the surrounding
connective tissue. It causes frequently very great swelling, and sometimes
results in the extraordinary deformities of different parts of the body known as
elephantiasis arabum. It seems, however, that these effects do not appear until
long after the infection and it is well known that in elephantiasis the filarie
are no longer present. Dr. Lebredo particularly points out the abundance of
the parasites in children and the large number of cases in which marked symp-
toms of the disease are absent.

The female Filaria, enclosed in the lymphatic vessels, is viviparous and gives
birth to an immense number of microscopic embryos. These embryos are eel-
shaped, enveloped in a loose sheath, and are very active. They spread in the
lymph and then with it into the blood, and it is in the blood that they are com-
monly observed

PERIODICITY OF FILARI/E.

The embryos of Filaria bancrofti are usually in abundance in the blood of the
peripheral circulation only during the night, or during sleep; during the day,
or when the patient is awake, they can not be found. There seems to be no good
explanation of this periodicity, nor is it absolutely exact, but it appears to con-
310 MOSQUITOES OF NORTH AMERICA

stitute a very curious adaptation of the parasite to the nocturnal habits of the
mosquito which serves as an intermediary host.*

Manson discovered the periodicity of the embryos. He placed a patient whose
blood contained filarie in a room where mosquitoes were plentiful. After the
patient had gone to bed a light was placed beside him, and the door left open for
the mosquitoes to enter. Later, when many mosquitoes had entered, the light
was put out and the door was closed. In the morning mosquitoes filled with
blood were captured, and the blood in their stomachs was examined and found
to contain more filarie than an equal quantity of blood taken directly from the
patient. Since then the periodicity of the filarial embryos in the peripheral
circulation has been abundantly verified. In fact, as with one species of Filaria
the embryos appear at night while with another they are only in evidence in the
daytime and with still others there is no periodicity apparent, this phenomenon
is largely relied upon for determination of the parasite. The periodicity is, to a
certain degree at least, determined by the habits of the host. In the case of
Filaria bancrofti the appearance of the embryos in the peripheral circulation
seems to be determined by the decreased action of the heart during sleep, rather
than by the time of day. Mackenzie succeeded in reversing the time of appear-
ance of the filarie by inducing his patients to sleep by day and keeping them
active at night. Manson found that when a patient sleeps alternately, sometimes
by night, sometimes by day, the periodicity of the filarie disappears altogether.

In the case of Filaria perstans and F. demarquayi there is no marked peri-
odicity, and the absence of periodicity is given as one of the characteristics of
F. philippinensis. The African Filaria diurna, which is believed by Manson and
others to be the embryo form of Filaria loa, is present in the peripheral circula-
tion only in the daytime. Numerous experiments with mosquitoes of a great
variety of species, to determine the transmitter of Filaria diurna, have all proved
negative and, while a number of diurnal blood-sucking insects have been sus-
pected, the actual transmitter remains unknown. Fiilleborn and Rodenwaldt
in their investigations with filarie of dogs from Italy found that there were two
forms (one of them probably Filaria immitis) one of which showed periodicity
while the other did not.

EVOLUTION IN THE MOSQUITO.

Later Manson ascertained that when these embryos are taken into the stomach
of the mosquito they cast their envelope, penetrate the wall of the stomach and
thus enter the general body cavity. The embryos then make their way into the
muscles of the thorax and lodge within the muscle bundles. They now loose
their activity and shorten and thicken very appreciably. It is only after they
have become fixed and immovable that they actually begin to grow. According
to Looss and others, when the larval filarisee have reached a length of about 0.24
mm., and 0.03 mm. thickness, they begin to show signs of returning activity.

 

* Recently the question of the cause of the periodicity of the filarlal embryos has been very
ably discussed by Dr. Ernst Rodenwaldt, based on the investigations of Fiilleborn and himself.
The subject is a complex one and we recommend to those sufficiently interested the perusal of the
original paper.
DEVELOPMENT IN MOSQUITO 311

The movements, however, to the end of the ripening stage of the larva remain
slow and very circumscribed. Generally the larve are found in extended
position in the muscle fibers, these latter disintegrating into a fine granular sub-
stance which serves as nourishment for the larve. A variable proportion of the
larve die during this stage.

When the larve have reached a certain size (given by various investigators as
from 1.006 to 1.8 mm.) they leave the muscles and return to the general body-
cavity. They now are very active and generally make their way to the anterior
end of the mosquito, penetrating from the thorax into the head and from thence
into the labium. Occasionally filarie go astray and get into the abdomen; they
have also been found in the hollows within the legs and palpi.

Lebredo gives the following synopsis of the filarial development within the
mosquito :

“1. The insect sucks the blood of a patient infected with filaria.

“2. The embryo loses its sheath in the stomach of the mosquito, ecdysis.

“3. Migration from the stomach to the thorax. This migration always takes
place through the gastric wall, since both orifices of the gastric dilatation are
completely closed when the stomach is full. The embryo leaves its sheath in the
gastric contents or caught in the wall of the stomach, where it is left at the
moment of exit.

“4, The embryo rests in the thorax, and goes through the following trans-
formations:

“ (a) Narrowing and invagination of the tail.

“ (6) Invagination continues and the embryo grows shorter and wider.

“(c) Widening and shortening continue, and the invaginated portion forms
a hyaline appendix.

“ (d) Period of growth and formation of the three lobes.”

Then follows the escape of the fully developed larva into the general body-
cavity. This is the period of its greatest activity which generally results in its
gaining the interior of the labium. Then the larva awaits the next step in its
evolution, the transfer to its vertebrate host.

It has been frequently observed that the proportion of embryo filarie con-
tained in the blood within the mosquito’s stomach is much greater than in the
same quantity taken directly from the circulation. Various explanations have
been offered, but Fiilleborn has shown that this difference is only an apparent
one, being due to the dehydration of the blood within the mosquito’s stomach.
At the same time this thickening of the blood makes it viscid and this serves,
as it were, to hold the sheath when the embryo moullts, as it does at this time.

The time necessary for the development of the larval filaria to its final active
condition is variable. Manson first gave a period of seven days but no such rapid
development has been observed by others and he himself admits that there may
have been an error in his observation. James, in India, states the period to be
from 12-14 days; Bancroft, in Australia, never saw them before the 16th or
1%th day, and the period was extended to 35 days in cold weather. The govern-
ing factor is evidently the temperature. Looss found that in the Egyptian
winter some of the larvee were not fully developed until the 41st day after the
312 MOSQUITOES OF NORTH AMERICA

infection of the mosquito. Lebredo made extensive experiments with filaria
and mosquitoes in Havana. He found that from August through October the
filarial larve developed in 15 days; from December to January from 19 to 23
days were necessary. These differences were found to co-ordinate very well with
the temperatures shown by meteorological records. Fiilleborn, in Germany,
found that the filarie failed to develop within the mosquito at ordinary room
temperature ; but he obtained satisfactory results by keeping the mosquitoes in
an artificially heated room.

Filaria immitis of the dog differs somewhat from Filaria bancrofti in its
mode of evolution in the mosquito for it undergoes development within the
Malpighian tubes instead of in the thoracic muscles. The larve, when fully
developed, pierce the closed distal ends of the Malpighian tubes and in this way
get into the general body-cavity and from there into the head and finally the
interior of the labium. The development of Filaria immitis requires about ten
days ; Grassi and Nod, and also Fiilleborn, found that after that period the larve
had reached the labium.

MODE OF TRANSMISSION TO THE VERTEBRATE HOST.

Manson followed the evolution of the larval filariz within the mosquito only
to development within the thoracic muscles. Upon these observations he based
a theory to the effect that the mosquitoes falling into the water disintegrated
rapidly after death and liberated the parasites, and that the water containing
them, when drunk by human beings, carried the parasites once more into the
human body. Manson was undoubtedly influenced in the formulation of this
theory by the, at that time, general belief that the female mosquito was very
short-lived and died immediately or soon after disposing of her eggs. Later
Bancroft, finding that the female mosquito remained alive a long time, felt that
the filaria must have other means of reaching its ultimate host and the necessity
for some other explanation. He suggested two ways in which he thought man
might become infected. One of these was by accidentally swallowing the in-
fected mosquito; the other that while the mosquito is biting, the filaria, under
some stimulus, re-entering the digestive tract when the mosquito bit, made its
way along the proboscis, finally penetrating the human tissues.

Studies published in 1900, by Low, by James, and by Grassi and Noé, arrived
very near the truth. In fact these latter authors succeeded in producing, as they
believed, in the case of Filaria immitis of the dog, an infection by means of the
bites of filaria-bearing mosquitoes. They further produced convincing evidence
that the filarie left the mosquito when it sucked blood, and thus they were the
first to demonstrate the direct transfer of filarie by mosquitoes. No experi-
ments with Filaria bancrofti and man had ever been attempted on account of
the serious consequences of filarial infection.

The discovery by the above-mentioned investigators, at nearly the same time,
that the larval filariz, upon leaving the thoracic muscles of the mosquito, for the
greater part made their way to the proboscis, and there remained, head foremost,
for an indefinite period, pointed to direct transfer by the mosquito’s bite.
MODE OF INFECTION 313

Low, whose paper was published first, stated that the filarie reached the
human host “ not along the salivary duct as is the case with the malarial para-
site, for this channel is manifestly too minute to accommodate a body relatively
so gigantic as the filaria ; not along the wsophagus or pharynx, as Bancroft sug-
gested ; but by making an independent passage through the base of the labium,
and pushing forwards along the proboscis between labium and hypopharynx
amongst the stylets.” Low was correct in his statement that the filarie do not
leave the mosquito by the salivary ducts or cesophagus but he was mistaken, as
we shall see, in the manner of their escape. The error was due to faulty inter-
pretation, as his own illustrations, from his microscopic preparations, show.

James, a little later in the same year, as the result of experiments in India
with filaria-bearing mosquitoes, announced that he had found the ripe larve
inhabiting the labium. Throughout his paper he employs the term “ labrum ”
instead of labium, but reference to his figures shows that this is a lapsus and that
he had found the true condition. In consequence he accepted the doctrine of the
transmission of filarie direct by the mosquito, which he had up to then opposed.
He procured further evidence by observing the behavior of filarie, taken from
the mosquito, when placed in water and in blood. He found that those larve
which had been placed in water soon became slower in their movements, and,
after two and a half hours were dead. Those placed in blood retained their
activity undiminished for a long time and lived fully seven hours.

In papers published still later in the same year Grassi and Noé verified that
the ripe filarial larve inhabit the interior of the labium and there wait until
the mosquito bites to migrate to their ultimate host. They supposed that when
the labium was doubled upon itself in the act of biting a tension of this organ
was produced which caused it to rupture along the dorsal groove and liberate the
filarie. They believed that they had detected a labium thus ruptured among
their preparations.

Finally, in 1901, the true method of escape of the filariee from the labium was
indicated by Annett, Dutton and Elliott, although they were unable to demon-
strate it. These authors studied carefully the mouth-parts of the mosquito and
found that dorsally at the tip of the labium and connecting the labelle there is
a delicate membrane and that this is the weakest point in the labium. They
showed that the filarize most probably made their exit at this point, not only
because it is the weakest, but also because the path of the filarie lay in this
direction and they were often found in the anterior portion of the labium.
The membrane in question has been termed, in honor of one of these investi-
gators “ Dutton’s membrane.”

That this last explanation is the correct one was not demonstrated until 1905,
when Dr. Mario G. Lebredo, of Havana, published the results of his investiga-
tions. Lebredo was not only able to show that the filarial larvae escape by pierc-
ing the delicate membrane at the tip of the labium, but also that this does not
happen when the mosquito sucks water, sweets or vegetable juices—a suggestion

which had been previously made but generally rejected.
314. MOSQUITOES OF NORTH AMERICA

Lebredo shows by his experiments that it is the heat from the body of the
prospective host that stimulates the filariz to leave the proboscis of the mosquito.

“ A mosquito is selected in which the filariee have reached their final stage of
development, and are lodged in the labium. It is best to select an insect 28 to
30 days, or more, after infection. After removal of the wings and legs the insect
is placed alive upon a slide and irrigated with a very weak salt solution. No
cover-glass is employed. Under the microscope it is possible to see, through the
transparent walls of the labium, the actively moving worms within that
structure.

“Tf no pressure is used, these movements may be watched for hours without
observing the escape of a single worm.

“ Usually all the sete are enclosed within the labium, thus preventing a clear
view of the movements of the filaria. In order to obviate this difficulty I press
very lightly with the side of a needle upon the base of the proboscis, and then
with the point of a needle inserted between the sete and the labium, I pry them
further apart. The filarie can now be distinctly seen actively moving and
agitating the two tracheal tubes. The worms occupy usually the proximal third
of the labium ; sometimes they extend further out.

“The slide is now placed near the flame of a Bunsen burner. This must be
done very carefully in order to avoid fatal over-heating to the insect and the
parasite. Watching the preparation, an unusual activity in the movements of
the filarie is now to be seen, and the cephalic end particularly becomes agitated
as if seeking a point of exit. This cannot be found laterally because of the
chitinous covering, and the filaria advances toward the anterior extremity of
the labium. If the liquid is allowed to cool, the movements become slower and
even cease altogether. Upon warming carefully again, and adding more tepid
fluid, the movements are revived until the worms reach the point of the labium.
If now the application of heat is stopped, we find that the worms appear to feel
around with their cephalic extremity, but fail to break out.

“T am sure that there is no natural orifice at the terminal end of the labium,
because if there were, the filaria, having reached this point, would find no ob-
stacle to its exit. And, furthermore, a careful study of the extremity fails to
discover any orifice.

* * * * * * * *

“Tf the heat is kept up carefully and steadily we can see the embryo seeking

the point, making pressure there, and finally perforating the cuticle at a certain
oint.

ee This perforation is made quite suddenly, for we see the cephalic end jump
out, as it were; the rest of the worm following slowly by serpentine movements.
As soon as it reaches the fluid the serpentine movements continue, but the worm
ceases to be able to advance. This remarkable difference in the results obtained
by the movement indicates that the soft tissues at this stage are the natural
element of the worm, and that it is prepared to move on into the human tissues
directly from the mosquito. In water, on the other hand, the filaria not only
cannot live, but cannot even move from place to place.

“Tn their exit the worms follow the regular order in which they occur in the
labium and head. We have seen two worms making their exit at the same time.

“ Occasionally, after two embryos have been started out, it has been necessary
to warm the liquid again in order to bring other worms down from the head to
the labium. Of course, after the first embryo has broken out, the others find
their way out with greater readiness.”
FILARIA TRANSMITTERS 315

Finally, the last step in the process of filarial infection remained obscure
until 1908, when it was made known by Fiilleborn. This is the mode of entry of
the worms into the body of the vertebrate host. It was supposed that the filariz
gained access to the body directly through the wound inflicted by the mosquito
and while it is engaged in sucking. This Fiilleborn disproved, both by careful
direct observation and by long series of preparations of skin with the parasites
in the act of penetrating.

“ According to the suppositions of most authors the place at which the filarie
enter the skin is through the channel made by the puncture of the mosquito.
At this point the entrance of the filarix can not well take place during the process
of sucking, for between and besides the piercing sete the filarie can not pene-
trate because the stylets form a compact bundle which tightly plugs the channel
of the puncture. It is possible that they sometimes choose this prepared passage
after the mosquito has taken flight, for during the act of sucking, which only
lasts a very short time, it appears that, as a rule, they do not enter the skin at
all; in my experiments I only found them in the skin when there had been an
interval, not too short, between the act of sucking and the cutting away of the
skin (involving the killing of the filarie). But that the filarie certainly do
not need the perforation made by the mosquito to get into the depths of the
skin is apparent from the fact that I also found them in the skin when no mos-
quito puncture had taken place and they were simply placed upon the skin of
the experimental animals; they evidently behave similarly to the Ankylostoma
larve, a supposition which Eysell has also expressed.”

MOSQUITOES THAT TRANSMIT FILARIASIS.

The full development of the filarial larvae, and consequently their transmis-
sion, can only take place with certain species of mosquitoes. In others the
embryos are either digested or eliminated through the digestive tract, or they
undergo a partial metamorphosis and then die.

In the case of Filaria bancrofti a number of species of mosquitoes are effective
hosts, but in an unequal degree. The most important transmitter of this para-
site is evidently Culex quinquefasciatus, the common house-mosquito of the
tropics. This is the species which has been used by Bancroft in Australia under
the name Culez ciliaris, by Manson in China and by Low in Santa Lucia under
the name Culex fatigans, and by Lebredo at Havana as Culex pipiens. There is
every reason for believing that these observers all had this same mosquito, which
is so widely distributed and abundant throughout the tropical and subtropical
regions. James, in India, found Anopheles rossti, and a second undetermined
species of the same genus, to be efficient hosts; the same was found to be true
with Anopheles costalis by Annett, Dutton and Elliott in West Africa. For
Italy and Spain Anopheles maculipennis, A. bifurcatus, A. pseudopictus and
Culex penicillaris are reported as transmitters. The identification of this last
mosquito seems open to doubt. Other species of mosquitoes in which Filaria has
been found to develop are Anopheles annulipes, A. albimanus, A. minutus, A.
nigerrimus, Aédes calopus, Mansonioides uniformis and Mansonia pseudo-
titillans (?=titillans). James, in his experiments, found that Filaria bancrofti
developed partially in Culex microannulatus and Aédes scutellaris.
316 MOSQUITOES OF NORTH AMERICA

Ashburn and Craig have followed the development of Filaria philippinensis
in Culex quinquefasciatus but got only negative results with Aédes calopus.
There appears to be some doubt that this Filaria is a valid species but Looss con-
siders it distinct.

Fiilleborn, in his experiments in Germany, used Anopheles maculipennis and
Aédes calopus. He found that Filaria bancrofti, F. perstans and F. demarquayt
underwent partial development in the Anopheles and then perished. One Aédes
calopus showed a developmental stage of Filaria demarquayi in the thoracic
muscles. With Filaria immitis of the dog Fiilleborn found that Anopheles
maculipennis became practically always infected. Aédes calopus became in-
fected in the proportion of one to five. Nevertheless he found this latter species
the more satisfactory for experimentation because, in the high temperature
necessary for the development of the filarie, the Anopheles suffered great

mortality.

SUGGESTED RELATIONS OF MOSQUITOES WITH OTHER
DISEASES.

While it seems reasonable to suppose that mosquitoes, together with other
biting insects, may be responsible for the transfer of certain diseases which do
not necessarily require a secondary host for complete development, such rela-
tion has never been proved. They have been accused or suspected of being im-
portant agents in the transfer of leprosy, in the carriage of bubonic plague, of
tropical ulcer and other skin diseases, of Malta fever, of the horse sickness of
South Africa, and of other maladies, even of cancer. Some of these diseases
have never been satisfactorily investigated. With others it has been shown that
they are transmitted in other ways. Thus bubonic plague is now well known tu
be transmitted by the bite of certain fleas and Malta fever is acquired through
the consumption of the milk of goats affected with this disease.

EFFECT OF MOSQUITO BITES.

The bite of nearly all mosquitoes causes some irritation but this varies in
degree with different species and with the individual bitten. It is by no means
always the largest mosquito which inflicts the most painful bite. Very serious
results have been attributed to mosquito bites. However, beyond a doubt, when
serious results follow these are due, not to the bite itself, but to the scratching
indulged in by the victim. In such cases it is the infection from the finger nails
which causes the trouble and this may indeed be serious. In sensitive persons
the inclination to scratch is well-nigh irresistible ; it will, however, be found that
if one exercises self-control in this respect the effect of even the severest bite will
pass very quickly.

Réaumur thought that a poisonous fluid was secreted by the mosquito and
that its purpose was to cause the blood to flow more readily when it bites. Later
observers either accepted this statement or denied the existence of such fluid,
stating that the swelling following the bite was caused by the irritation of the
puncture without the aid of a poison. Dimmock (1881) convinced himself that
POISON OF MOSQUITO-BITE LT

@ poisonous saliva was introduced. He noticed that if the mosquito punctures
the skin without entering a blood vessel, although it may insert its proboscis
for nearly its full length, no poisonous effect is produced upon the skin, but
when the proboscis strikes blood and the insect draws it, the subsequent swelling
and poisonous effects are obvious. He argued that these effects indicate a con-
stant outpouring of some sort of poisonous fluid during the blood-sucking
process.

Miall (1895) maintains that it can not positively be said whether poison is
injected into the wound or not. His statement is, “‘ No poison gland has hitherto
been demonstrated, and there is some reason to believe that the irritation of the
wound is slight in cold weather and only becomes intense during great summer
heat.” But in our chapter on the anatomy of mosquitoes we have shown that
Maclosky has demonstrated a differentiation in the salivary glands, one of each
set being modified to secrete the poison. Fritz Schaudinn is inclined to believe
that the mosquito bite is poisonous not because of any poisonous secretion of the
salivary glands, but because of toxins produced by plant parasites in its
esophageal diverticula.

The purpose of the mosquito poison has been the subject of some conjecture.
The old Réaumur hypothesis, that it causes the blood to become more liquid and
more readily sucked up by the mosquito, has had its adherents. Osten Sacken
and Miall, however, believe that it is probable that the piercing mouth-parts of
the mosquito were originally acquired for the purpose of sucking the juices of
plants, and Maclosky advances the idea that the chief food of mosquitoes is not
animal blood but the proteids of plants, and that probably the poison injected
may prevent the coagulation of proteids and so promote the process of suction.

Prof. John B. Smith was inclined to believe in the Réaumur hypothesis, that
the poison prevents the clotting of the blood in the stomach of the mosquito.
He says:

“A mosquito bites, primarily to obtain food; there is neither malice nor
venom in the intent, whatever there may be in the act. Theoretically there
would seem to be no reason why there should be any pain from the introduction
of the minute lancets of the insects, and the small amount of blood-letting is
usually a benefit rather than otherwise. Unfortunately, however, in its normal
condition the human blood is too much inclined to clot to be taken unchanged
into the mosquito stomach; hence, when the insect bites, a minute droplet of
poison is introduced, whose function it is to thin out the fluid and make it more
suitable for mosquito digestion. It is this poison that sets up the inflammation
and produces the irritation or swelling. If we make a puncture wound with a
fine needle, a small droplet of blood will exude which will almost at once harden
into a clot, and if we attempt a little later to break that clot, we will find it tough
and hard to disintegrate. If we allow a mosquito to bite until it is fully gorged
and then smash it, we find that the blood from the gorged abdomen is much
more fluid and spreads out thin. If we further allow it to dry, there will be no
clot ; but a thin spread of material which is brittle and breaks readily into frag-
ments.

“The pain is caused entirely by the action of the poison in breaking up the
blood, and as the first act of a biting mosquito is to introduce this poison into
the wound, the pain and inflammation will be the same, whether the insect gets
318 MOSQUITOES OF NORTH AMERICA

its meal or not. In fact, it has been said that if a mosquito be allowed to suck
its fill and then fly, the bite will not itch, and there is just a basis of justification
for this. The poison introduced will act upon just so much blood, and if that be
absorbed with the poison by the insect, little or nothing will be left in the
wound. If, however, the mosquito be killed as soon as the poison is introduced,
the latter will have to be absorbed by the human system and the disintegrated
blood mass with it. This is the basis of fact behind the popular belief that a bite
does not hurt if you allow a mosquito to complete its meal and withdraw the
lancets naturally.”

The popular belief referred to by Smith in this last sentence seems to have a
basis of exact observation, and such an observation was originally made by Hum-
boldt in the early part of the last century. Humboldt states that when one lets
a mosquito suck its fill there is no swelling and no pain. He often tried the ex-
periment on himself, in the valley of the Rio de la Magdalena, on the advice of
the natives. He wondered whether the insect only injects the poison at the
moment when it is frightened away, or whether it sucks back the poison when
it is allowed to suck as much as it will. He inclined to the latter opinion, for
when he allowed Culex cyanopterus * to peaceably bite the back of his hand, he
noticed that the pain, which was very strong in the beginning, diminished as the
insect continued to pump up the blood and that it ceased absolutely at the
moment when the sucking was finished. One of the writers is inclined to be-
lieve from his own experience that when a mosquito is allowed to drink her fill
there is less irritation than when she is frightened away by an ill-advised slap.

RELATIVE SUSCEPTIBILITY.

The amount of irritation caused by the poison of mosquitoes varies greatly
with different individuals. This was already pointed out by Humboldt and
other early writers. Some people suffer severely from their bites, while others
are not at all affected. This is a matter of common observation. We have
already shown in quoting from Réaumur severe instances of the irritation caused
by the bites of many of these insects, which caused the limbs to swell until
amputation was seriously considered. Réaumur also brings out the point of
relative susceptibility. He found that not only are peasants with sun-burned
and work-hardened skin bitten as often as ladies with delicate skin, but he states
that he has observed that among ladies with whom he happened to be in the
country, some were attacked while others with equally fine skin were not at-
tacked. Arguing then that certain skins are distasteful to mosquitoes he con-
sidered that there must be some means of rendering all skins distasteful. He
advocates experimenting with different liquids for this purpose and especially
decoctions of such plants as the mosquitoes seem to avoid, as he had noticed
them to leave some plants immediately after alighting on them. Smith’s obser-
vations on this point are interesting:

“ Susceptibility to mosquito poisoning varies enormously. Some persons do

not even notice ea ete biting under ordinary conditions, though they may be
honestly unaware of their exemption. I remember enjoying a drive with a man

 

* Probably the species described by Humboldt as Oulew cyanopennis (Voyage aux Reg.
equinoct. a p. 340 (1819) ) : we have not been able to identify it. wees .
EFFECT OF BITE 319

who told me of his sufferings from mosquito bites while a specimen was deliber-
ately filling itself from his lower lip, not in the least disturbed by the talk. Mr.
Brehme does not notice marsh mosquito attacks at all; but he bolts green-head
flies. Mr. Brakeley captures perturbans by looking at his ankles occasionally
and bottling any specimens he may see there. It is only when he sees them that
he knows they are present and yet perturbans is a hard biter!

“On the other hand, I have met many persons to whom even a single bite
was a torture and who were in positive agony during a stay along shore. In such
persons puffy swellings appear and cover an area an inch or more in diameter
from a single bite. When bites are at all numerous the suffering is intense and
the appearance pitiable. Between these extremes all intergrades are found; but
I have never found a man yet, who, in a mosquito region, had not at times been
driven out by mosquitoes.

“ Personally the insects bother me, but the pain is usually temporary and, if I
refrain from scratching, a matter of a few minutes only. And this brings up the
matter of species; for a man may be exempt as against one species and not
another. Boatmen and others along shore, who never know whether mosquitoes
are present in their own territory, suffer severely and swear loudly when they get
within range of the inland mosquitoes ; and the contrary is equally true.

“ Nowadays I scarcely mind sollicitans at all, and cantator does not worry
me much. C. pipiens is more troublesome and its bites sometimes cause distinct
swellings ; but I can sleep through any attack save that of Anopheles. This has
a different song and a different manner of attack, and somehow I do not feel at
ease near it. I will awaken at any time to a specimen buzzing about, where I
would not mind any species of Culex. These are, of course, personal character-
istics, and may not apply to any other individual. The case is cited merely to
show that there is a difference between the virus of the species and between the
susceptibility of individuals.

“ There is also a difference in the manner of attack. Some species hover about
for a long time, selecting a place to puncture; others dart in at once, giving
scarcely any notice of their arrival; some fly at the least disturbance, while
others can scarcely be driven off when once they have tasted blood. . . .”

There can be little doubt that people become inoculated against this poison.
Persons living in mosquito-ridden localities as a rule suffer less than those who
come there from more favored regions, and it seems likely that after a severe
case of mosquito poisoning the inoculating effect may last for a long time. An
instance of this was sent us in 1900 by the late lamented Edward Everett Hale,
who wrote:

“JT think I am an instance of inoculation by mosquitoes’ virus. More than
fifty years ago I went into the Maine woods, going to Katahdin. The first after-
noon we were out hardly an hour, but at night, when we went into camp, I
counted sixty well defined mosquito bites on my right hand alone. Now from
that time to this I have hardly been troubled by mosquitoes. I dislike their song
at night, and if I saw one on my hand I should kill it, but after the moment of
the sting I never remember that I have been bitten.”
ECONOMIC LOSS FROM MOSQUITOES.
LOSS FROM MALARIA.

The senior author, in a publication of the U. 8. Department of Agriculture
entitled “ Economic loss to the people of the United States through insects that
carry disease,” has discussed the effect of malaria as follows:

“ The west coast of Africa, portions of India, and many other tropical regions
have always, at least down to the present period, been practically uninhabitable
by civilized man, owing to the presence of pernicious malaria. The industrial
and agricultural development of Italy has been hindered to an incalculable
degree by the prevalence of malaria in the southern half of the Italian peninsula,
as well as in the valley of the Po and elsewhere. The introduction and spread of
malaria in Greece is stated by Ronald Ross, and with strong reasons, to have
been largely responsible for the progressive physical degeneration of one of the
strongest races of the earth.

“In the United States, malaria, if not endemic, was early introduced. The
probabilities are that it was endemic, and it is supposed that the cause of the
failure of the early colonies in Virginia was due to this disease. It is certain
that malaria retarded in a marked degree the advance of civilization over the
North American continent, and particularly was this the case in the march of
the pioneers throughout the Middle West and throughout the Gulf States west to
the Mississippi and beyond. In many large regions once malarious the disease
has lessened greatly in frequency and virulence owing to the reclamation of
swamp areas and the lessening of the number of the possible breeding places of
the malarial mosquitoes, but the disease is still enormously prevalent, particu-
larly so in the southern United States. There are many communities and many
regions in the North where malaria is unknown, but in many of these localities
and throughout many of these regions Anopheles mosquitoes breed, and the
absence of malaria means simply that malarial patients have not entered these
regions at the proper time of the year to produce a spread of the malady. It has
happened again and again that in communities where malaria was previously un-
known it has suddenly made its appearance and spread in a startling manner.
These cases are to be explained, as happened in Brookline, Mass., by the intro-
duction of Italian laborers, some of whom were malarious, to work upon the
reservoir; or, as happened at a fashionable summer resort near New York City,
by the appearance of a coachman who had had malaria elsewhere and had re-
lapsed at this place. In such ways, with a rapidly increasing population, malaria
is still spreading in this country.

“To attempt an estimate of the economic loss from the prevalence of malaria
in the United States is to attempt a most difficult task. Prof. Irving Fisher, in
one of his papers before the recent International Tuberculosis Congress, declared
that tuberculosis costs the people of the United States more than a billion dollars
each year. In this estimate Professor Fisher considered the death rate for con-
sumption, the loss of the earning capacity of the patients, the period of in-
validism, and the amount of money expended in the care of the sick, together
with other factors. In making these estimates he had a much more definite basis
than can be gained for malaria. The death rate from malaria (as malaria) is
comparatively small and is apparently decreasing. Exact figures for the whole

320
MALARIA A CHECK ON PROGRESS 321

country are not available. From a table comprising 22 cities it appears that two-
thirds of the deaths from malaria in the United States occur in the South—one-
third only in the North. The death rate from malaria by States is available only
for the following registration States : California, Colorado, Connecticut, District
of Columbia, Indiana, Maine, Maryland, Massachusetts, Michigan, New Hamp-
shire, New Jersey, New York, Pennsylvania, Rhode Island, South Dakota, and
Vermont, all of which are Northern States. For these States the census reports
from 1900 to 1907, inclusive, give the following death rates:

DeaTHs DUE TO MALARIA IN THE REGISTRATION STATES.
1900-1907.

 

Number of Number of

deaths from deaths from
Year.| malaria per |,rotal deaths Total deaths

 

100,000 popu- /f70™ malaria. Year. ques Gone from malaria.
lation. lation.
1900 7.9 2434 1904 4.2 1391
1901 6.3 A7O1 1905 3.9 1821
1902 5.4 1738 1906 3.5 1415
1903 4.3 1410 1907 2.8 1166

 

 

 

 

 

 

“ Estimating, from the preceding table, the average annual death rate due to
malaria, at 4.8 per 100,000 population, and considering that the registration area
includes only 16 of the Northern States (assuming fairly, however, that the
death rate in the other Northern States is the same), it seems reasonably safe to
conclude that the death rate from malaria for the whole United States must
surely amount to 15 per 100,000. It is probably greater than this, since the
statistics from the South are city statistics, and malaria is really a country
disease. Thus it is undoubtedly safe to assume that the death rate for the whole
population of the United States is in the neighborhood of 15 per 100,000. This
would give an annual death rate from malaria of nearly 12,000 and a total num-
ber of deaths for the 8-year period 1900-1907 of approximately 96,000.

“ But with malaria perhaps as with no other disease does the death rate fail to
indicate the real loss from the economic point of view. A man may suffer from
malaria throughout the greater part of his life, and his productive capacity may
be reduced from 50 to 75 per cent, and yet ultimately he may die from some en-
tirely different immediate cause. In fact, the predisposition to death from other
causes brought about by malaria is so marked that if, in the collection of vital
statistics, it were possible to ascribe the real influence upon mortality that
malaria possesses, this disease would have a very high rank in mortality tables.
Writing of tropical countries, Sir Patrick Manson declares that malaria causes
more deaths, and more predisposition to death by inducing cachectic states pre-
disposing to other affections, than all the other parasites affecting mankind to-
gether. Moreover, it has been shown that the average life of the worker in
malarious places is shorter and the infant mortality higher than in healthy

laces.
Pe But, aside from this vitally important aspect of the subject, the effect of
malaria in lessening or destroying the productive capacity of the individual is
obviously of the utmost importance, and upon the population of a malarious
region is enormous, even under modern conditions and in the United States.
It has been suggested that the depopulation of the once thickly settled Roman
Campagna was due to the sudden introduction of malaria by the mercenaries of
Scylla and Marius. Celli, in 1900, states that owing to malaria about 5,000,000
acres of land in Italy remain—not uncultivated, but certainly very imperfectly
322 MOSQUITOES OF NORTH AMERICA

cultivated. Then also, in further example, in quite recent years malaria entered
and devastated the islands of Mauritius and Réunion, practically destroying for
a time the productiveness of these rich colonies of Great Britain and France.

“ Creighton, in his article on malaria in the Encyclopedia Britannica, states
that this disease ‘ has been estimated to produce one-half of the entire mortality
of the human race; and inasmuch as it is the most frequent cause of sickness
and death in those parts of the globe that are most densely populated, the esti-
mate may be taken as at least rhetorically correct.’

“Ts it possible to make any close estimate of the ratio between the number of
deaths from malaria and the number of cases of the same malady? No per-
fectly sound basis for such an estimate is apparent. In the English translation
of Celli’s work on ‘Malaria According to the New Researches,’ published in
London in 1900, it is stated that the mortality from malaria in Italy from 1887
to 1898 varied from 21,033 in the first-named year to 11,378 in the last-named
year, and the mean mortality for the period is assumed to be about 15,000. In
1896 a count of the patients in the hospitals in Rome was made, and the mor-
tality rate of 7.75 per thousand of the actual patients was established. Calculat-
ing then on this basis, and at this rate, the number of cases per year for Italy was
placed at about 2,000,000. According to this estimate, and with the average
mortality for the United States of 12,000 as above indicated, the approximate
number of cases for the United States would be about 1,550,000. It seems
obvious, however, that Celli, in using the basis of hospital patients only, must
have underestimated the number of cases for the Kingdom, since of the people in
the country suffering from malaria the proportion entering the hospital must be
relatively small. Therefore the death rate from malaria of malarial patients
in the hospital must be greater than the death rate from malaria of the people
who suffer from this disease in the whole country. In fact, so great must this
discrepancy necessarily be that it would not seem at all unlikely to the writer
if the number of persons suffering from malaria in Italy were in reality nearer
3,000,000 than 2,000,000.

“The same argument will hold for the United States, and more especially so
since as a rule malaria in this country is of a lighter type than in Italy; in fact
an estimate of 3,000,000 cases of malaria in the United States annually is prob-
ably by no means too high. It will not be an exaggeration to estimate that one-
fourth of the productive capacity of an individual suffering with an average case
of malaria is lost. Accepting this as a basis, and including the loss through
death, the cost of medicines, the losses to enterprises in malarious regions
through the difficulty of securing competent labor, and other factors, it is safe
to place the annual loss to the United States from malarial disease under present
conditions at not less than one hundred millions of dollars. Celli has shown that
in Italy the great railway industries, for example, feel the effect of malaria
greatly. According to accurate calculations one company alone, for 1400 kilo-
meters of railway and for 6416 workmen in malarious zones, spends on account
of malaria 1,050,000 francs a year. The same writer states that the army in
Italy from 1877 to 1897 had more than 300,000 cases of malaria.

“The loss to this country in the way of retardation of the development of cer-
tain regions, owing to the presence of malaria, is extremely great. Certain
territory containing most fertile soil and capable of the highest agricultural
productiveness is practically abandoned. With the introduction of proper
drainage measures and antimosquito work of other character, millions of acres
of untold capacity could be released from the scourge at a comparatively slight
expenditure. These regions in the absence of malaria would have added millions
upon millions to the wealth of the country. Drainage measures are now being
initiated by the United States. Parties of engineers are being sent by the
MALARIA AND AGRICULTURE 323

Government to make preliminary drainage surveys in the most prominent of
these potentially productive regions. The following statement concerning the
effect of malaria on the progress of this work has been made to the writer by
Dr. George Otis Smith, director of the United States Geological Survey :

“<Tn one of the Southern States 11 topographic parties have been at work
during the past field season. The full quota for these parties would be 55 men,
but I believe that something over 100 men have been employed at different times
during the season. While I have not exact figures before me, I feel warranted
in the statement that at least 95 per cent of these employees have been sick, for
periods ranging from a few days up to two weeks, in the hospital. Many of them
have been able later to return to work, but at least 30 per cent had to leave the
field permanently. By reason of this sickness the efficiency of the parties was
reduced, at a very conservative estimate, by 25 per cent.

“¢Tn my recent visit in this field I found one man sick in each of the parties I
saw and one man who had just returned from the hospital leaving the field for
good. A similar state of things was reported from the other parties. I regard
the sickness as practically all of a malarial nature, as extreme care was taken
in all the camps to use nothing but boiled water except in a few instances where
artesian water from great depths was available. In all the camps the tents have
been screened, and in every case where the topographer has lived for any time
“on the country ” there has been infection. As illustrating the value of the
precautions generally taken by our camp parties, I might cite the fact that last
year in West Virginia with 30 men living in camp, with typhoid fever prevalent
in the neighborhood, no cases developed, while with 6 men living on the country
where the same care could not be taken regarding the water supply, two cases of
typhoid developed.’

“Tn estimating the weight of Doctor Smith’s statement, it must be borne in
mind that the men of his field parties are exceptionally intelligent and prepared
to take all ordinary precautions.

“Throughout the region in question malaria is practically universal. The
railroads suffer, and at the stations throughout the territory it is practically im-
possible to keep operators steadily at work. This reduction in efficiency in the
surveying parties and in the local railroad officials is moreover probably very
considerably less than the reduction in the earning capacity of the entire popu-
lation, which, however, is necessarily scanty.

“Tn an excellent paper entitled ‘The relation of malaria to agricultural and
other industries of the South, published in the Popular Science Monthly for
April, 1903, Prof. Glenn W. Herrick, then of the College of Agriculture of
Mississippi, after a consideration of the whole field, concludes that malaria is
responsible for more sickness among the white population of the South than any
disease to which it is now subject. The following forcible statement referring
to the States of Louisiana, Mississippi, Alabama, Georgia, and South Carolina
is in Professor Herrick’s words:

“ ¢ We must now consider briefly what 635,000 or a million cases of chills and
fevers in one year mean. It is a self-evident truth that it means well for the
physician. But for laboring men it means an immense loss of their time to-
gether with the doctors’ fees in many instances. If members of their families
other than themselves be affected, it may also mean a loss of time together with
the doctors’ fees. For the employer it means the loss of labor at a time perhaps
when it would be of greatest value. If it does not mean the actual loss of labor
to the employer it will mean a loss in the efficiency of his labor. To the farmers
it may mean the loss of their crops by want of cultivation. It will always mean
the noncultivation or imperfect cultivation of thousands of acres of valuable land.

22
324 MOSQUITOES OF NORTH AMERICA

It means a listless activity in the world’s work that counts mightily against the
wealth-producing power of the people. Finally it means from two to five million
or more days of sickness with all its attendant distress, pain of body, and mental
depression to some unfortunate individuals of those five States.’

“ Referring to the Delta region in Mississippi, which lies along the Mississippi
River in the western part of the State of Mississippi, extending from the mouth
of the Yazoo River north nearly to the Tennessee line, Herrick says that it is
the second best farming land in the world, having only one rival, and that is the
valley of the Nile.

«<Still,” says Herrick, ‘this land to-day, or at least much of it, can be bought at
ten to twenty dollars an acre. Thousands of acres in this region are still covered
with the primeval forest, and the bears and deer still roaming there offer splendid
opportunities for the chase, as evidenced by the late visit of our Chief Executive
to those regions for the purpose of hunting. Why is not this land thickly
settled? And why is it not worth from two to five hundred dollars an acre? If
it produces from one to two or more bales of cotton to an acre, and it does, it
ought to be worth the above named figures. A bale of cotton to the acre can be
produced for thirteen dollars, leaving a net profit of twenty to forty dollars for
each bale, or forty to eighty or more dollars for each acre of land cultivated,
Moreover, this land has been doing that for years, and will do it for years to
come, without the addition of one dollar’s worth of fertilizer. Land that will
produce a net profit of forty to eighty dollars an acre is a splendid investment
at one, two, or even three hundred dollars an acre. Yet this land does not sell
in the market for anything like so much, because the demand is not sufficient,
for white people positively object to living in the Delta on account of malarial
chills and fevers. A man said to me not long ago that he would go to the Delta
that day if he were sure that his own life and the lives of the members of his
family would not be shortened thereby. There are thousands exactly like him,
and the only reason that these thousands do not go there to buy lands and make
homes is on account of chills and fevers. But there is a time coming, and that
not far distant, when malaria in the Delta will not menace the would-be in-
habitants. When that time comes it will be the richest and most populous
region in the United States.’ ”

At the beginning of this chapter are mentioned the ravages of the disease
in India and Africa. The situation in these countries is well summed up by
Prof. A. E. Shipley in a paper on malaria,* from which we quote:

“Tt has been said that one-half the mortality of the human race is due to
malaria. This may very well be an exaggeration, but there can be little doubt
that, of all the ills that flesh is heir to, malaria is the most deadly, and exercises
the most profound influence on the distribution and activities of man. It will
be seen later that the disease is most rife where the densest populations are found,
and the mortality of such closely crowded area as India gives some idea of the
enormous loss of life and the widespread suffering caused by this disease. In
1892, out of a total population in India of 217,255,655, the deaths from all
causes reached the figure of 6,980,785. Of these, 4,921,583 were ascribed to
‘fever’ All these fevers were not, of course, malarial, but comparison with
other statistics leads to the belief that a high percentage of them was caused by
malaria. Major Ross states that in 1897 over 5,000,000 deaths in the same
country were recorded as due to ‘fever,’ and that out of a total strength of
178,197 men in the British army in India, 75,821 were treated in the hospitals
for malaria. Fifty years ago the loss from malaria amongst the European popu-

 

* Pearls & Parasites, by Arthur DB. Shipley, London, 1908. (The chapter on malaria covers
pages 129 to 154.)
EPIDEMICS OF YELLOW FEVER 325

lation of India was 13 per thousand. With improved methods of living and
more skillful treatment this has been reduced to 7 per thousand ; but the native,
who is slow to change his ways, and usually averse to modern methods of treat-
ment, still retains a very high fever death-rate—over 18 per thousand. .. .

Apart from the mortality due to this disease, the amount of suffering and
the decline in human power and activity which it entails deserve careful atten-
tion. Compared with the number of patients, the number of deaths is by no
means large. In round numbers, out of every thousand soldiers in the British
army in India in 1897, 420 men were attacked by malaria, but only one in a
thousand died; even in the ‘most malarious’ districts the death-rate only
amounted to 6 per thousand. In Sierra Leone, a district much more fatal than
any in India, the average death-rate of the white troops, based on hospital records
extending from 1892 to 1898, is estimated by Major L. M. Wilson at 42.9 per
thousand, whilst that of the coloured troops is 5.9 per thousand. On the other
hand, the European troops show an annual number of cases of 2134 per thou-
sand, and the non-European troops one of 1056 per thousand. These figures
probably under-estimate the amount of fever amongst the troops. It must be
remembered that many soldiers who have slight attacks of fever do not present
themselves at the hospital, whilst of those who do a considerable number are
only detained for slight treatment, and are never entered on the hospital books,
and so are not recorded on the returns.

“From the statistics quoted above, it appears that of our soldiers in India
three out of every seven suffer from an annual attack of malaria sufficiently pro-
nounced to be recorded on the medical books, whilst our soldiers on the west
coast of Africa have an average of at least two attacks a year, and a considerable
number of them die. There is no reason to believe that the civil population of
India or West Africa is in any degree more exempt from the disease than the
military, but the statistics in the latter case are more readily accessible.

“ Malarial fever, when it does not kill, leaves great weakness behind; and all
who have watched malaria patients, or patients who are already recovering from
an attack, cannot fail to have noticed the listlessness and want of interest in
their surroundings and the lack of inclination to work that they all show. Apart
from the mortality, the disease probably levies a heavier tribute on the capacity
of the officers and officials who administer the British Empire than does any
other single agency.”

LOSS FROM YELLOW FEVER.

In the publication already mentioned the senior author has discussed the effect
of yellow fever on the welfare of the United States as follows:

“ Yellow fever has prevailed endemically throughout the West Indies and in
certain regions on the Spanish Main virtually since the discovery of America.
Barbados, Jamaica, and Cuba suffered epidemics before the middle of the
seventeenth century. There were outbreaks in Philadelphia, Charleston, and
Boston as early as 1692, and for a hundred years there were occasional outbreaks,
culminating in the great Philadelphia epidemic of 1793. Northern cities were
able, by rigid quarantine measures, to prevent great epidemics after the early
part of the nineteenth century, but from the West Indies the disease was
occasionally introduced and prevailed from time to time epidemically in the
Southern States. In 1853 it raged throughout this region, New Orleans alone
having a mortality of 8000. The last widespread epidemic occurred in 1878,
chiefly in Louisiana, Alabama and Mississippi, but spreading up the Mississippi
Valley as far as Cairo, Ill., and attacking with virulence the city of Memphis,
Tenn. In this year there were 125,000 cases and 12,000 deaths. In 1882 there
326 MOSQUITOES OF NORTH AMERICA

were 192 deaths at Pensacola; in 1887, 62 deaths in the Southern States; in
1893, 52 deaths; in 1897, 484; in 1898, 2456 cases with 117 deaths; in 1903,
139 deaths were recorded, mostly at Laredo, Tex., and in 1905 there was a
serious outbreak at New Orleans and in neighboring towns, including one
locality in Mississippi, in which 911 deaths were recorded for the whole country.

“The actual loss of life from yellow fever during all these years, when com-
pared with the loss from other diseases, has been comparatively slight, but the
death rate is perhaps the most insignificant feature of the devastation which
yellow fever epidemics have produced, and the disease itself has been but a small
part of the affliction which it has brought to the Southern States. The disease
once discovered in epidemic form, the whole country has become alarmed; com-
merce in the affected region has come virtually to a standstill; cities have been
practically deserted ; people have died from exposure in camping out in the high-
lands; rigid quarantines have been established; innocent persons have been
shot while trying to pass these quarantine lines; all industry for the time has
ceased. The commerce of the South during the epidemic of 1878, for example,
fell off 90 per cent, and the hardships of the population can not be estimated
in monetary terms. With such industrial and commercial conditions existing
from Texas to South Carolina, many industries at the North have suffered, and,
in fact, the effect of a yellow fever summer in the South has been felt not only all
over the United States, but in many other portions of the world.

“ All these conditions, as bad as they have been, do not sum up the total loss to
the national prosperity during past years. Cities like Galveston, New Orleans,
Mobile, Memphis, Jacksonville, and Charleston, subject to occasional epidemics,
as they have been in the past, have not prospered as they should have done.
Their progress has been greatly impeded by this one cause, and thus the in-
dustrial development of the entire South has been greatly retarded.”

ENDEMIC DISEASES AS AFFECTING THE PROGRESS OF
NATIONS.*

“ In referring to the spread of malaria in Greece, the relation of this disease to
the rise and fall of national power has been touched upon in an earlier para-
graph. The subject is one of the widest importance and deserves a more ex-
tended consideration.

“ The following paragraphs are quoted from Ronald Ross’s address on Malaria
in Greece, delivered before the Oxford Medical Society, November 29, 1906:

“Now, what must be the effect of this ubiquitous and everlasting incubus
of disease on the people of modern Greece? Remember that the malady is
essentially one of the infancy among the native population. Infecting the child
one or two years after birth, it persecutes him until puberty with a long succes-
sion of febrile attacks, accompanied by much splenomegaly and anemia.
Imagine the effect it would produce upon our own children here in Britain.
It is true that our children suffer from many complaints—scarlatina, measles,
whooping cough—but these are of brief duration and transient. But now add
to these, in imagination, a malady which lasts for years, and may sometimes
attack every child in a village. What would be the effect upon our population—
especially our rural population—upon their numbers and upon the health and
vigour of the survivors? It must be enormous in Greece. People often seem to
think that such a plague strengthens a race by killing off the weaker individuals ;
but this view rests upon the unproven assumption that it is really the weaker
children which can not survive. On the contrary, experience seems to show that

 

* Quoted from Howard, L. O., Economic loss _to the ros of the United States through
Insects that carry disease. U. 8. Dept. Agr., Bur. Wnt., Bull. 78, pp. 86-38, 1909.
MALARIA IN GREECE 327

it is the stronger blood which suffers most—the fair, northern blood which nature
attempts constantly to pour into the southern lands. If this be true, the effect
of malaria will be constantly to resist the invigorating influx which nature has
provided: and there are many facts in the history of India, Italy, and Africa,
which could be brought forward in support of this hypothesis.

“We now come face to face with that profoundly interesting subject, the
political, economical, and historical significance of this great disease. We know
that malaria must have existed in Greece ever since the time of Hippocrates,
about 400 B. C. What effect has it had on the life of the country? In pre-
historic times Greece was certainly peopled by successive waves of Aryan in-
vaders from the north—probably a fair-haired people—who made it what it
became, who conquered Persia and Egypt, and who created the sciences, arts, and
philosophies which we are only developing further to-day. That race reached
its climax of development at the time of Pericles. Those great and beautiful
valleys were thickly peopled by a civilization which in some ways has not been
excelled. Everywhere there were cities, temples, oracles, arts, philosophies, and
a population vigorous and well trained in arms. Lake Kopais, now almost
deserted, was surrounded by towns whose massive works remain to this day.
Suddenly, however, a blight fell over all. Was it due to internecine conflict or
to foreign conquest? Scarcely; for history shows that war burns and ravages,
but does not annihilate. Thebes was thrice destroyed, but thrice rebuilt. Or
was it due to some cause, entering furtively and gradually sapping away the
energies of the race by attacking the rural population, by slaying the new-
born infant, by seizing the rising generation, and especially by killing out the
fair-haired descendant of the original settlers, leaving behind chiefly the more
immunised and darker children of their captives, won by the sword from Asia
and Africa? ...

“«T can not imagine Lake Kopais, in its present highly malarious condition,
to have been thickly peopled by a vigorous race ; nor, on looking at these wonder-
ful figured tombstones at Athens, can I imagine that the healthy and powerful
people represented upon them could have ever passed through the anaemic and
splenomegalous infancy (to coin a word) caused by widespread malaria. Well,
I venture only to suggest the hypothesis, and must leave it to scholars for con-
firmation or rejection. Of one thing I am confident, that causes such as malaria,
dysentery, and intestinal entoza must have modified history to a much greater
extent than we conceive. Our historians and economists do not seem even to
have considered the matter. It is true that they speak of epidemic diseases, but
the endemic diseases are really those of the greatest importance. .. .

“©The whole life of Greece must suffer from this weight, which crushes its
rural energies. Where the children suffer so much, how can the country create
that fresh blood which keeps a nation young? But for a hamlet here and there,
those famous valleys are deserted. I saw from a spur of Helikon the sun setting
upon Parnassus, Apollo sinking, as he was wont to do, towards his own fane at
Delphi, and pouring a flood of light over the great Kopaik Plain. But it seemed
that he was the only inhabitant of it. There was nothing there. ‘Who,’ said a
rich Greek to me, ‘ would think of going to live in such a place as that?’ I doubt
much whether it is the Turk who has done all this. I think it is very largely the
malaria.

“Tn considering carefully this suggestive argument of Major Ross does it not
appear to indicate the tremendous influence that the prevalence of endemic
disease must exert upon the progress of modern nations, and does it not bring
the thought that those nations that are most advanced in sanitary science and
preventive medicine will, other things being equal, assume the lead in the
world’s work? Who can estimate the influence of the sanitary laws of the
328 MOSQUITOES OF NORTH AMERICA

Hebrew scriptures upon the extraordinary persistence of that race through
centuries of European oppression—centuries full of plague years and of terrible
mortality from preventable disease? And what more striking example can be
advanced of the effect of an enlightened and scientifically careful attention to
the most recent advances of preventive medicine upon the progress of nations
than the mortality statistics of the Japanese armies in the recent Russo-Japanese
war as compared with the corresponding statistics for the British army during
the Boer war immediately preceding, or for the American Army during the
Spanish war at a somewhat earlier date?

“ The consideration of these elements of national progress has been neglected
by historians, but they are nevertheless of deep-reaching importance and must
attract immediate attention in this age of advanced civilization. The world
has entered the historical age when national greatness and national decay will
be based on physical rather than moral conditions, and it is vitally incumbent
upon nations to use every possible effort and every possible means to check
physical deterioration.”

LOSSES FROM MOSQUITOES ASIDE FROM THE CARRYING
OF DISEASE.
Entirely aside from the loss occasioned by mosquitoes as carriers of specific
diseases, their abundance brings about a great monetary loss in other ways.

REDUCED VALUE OF REAL ESTATE.

Possibly the greatest of these losses is in the reduced value of real estate in
mosquito-infested regions since these insects render absolutely uninhabitable
large areas of land otherwise available for suburban houses, for summer resorts,
for manufacturing purposes, and for agriculture. The money loss becomes
most apparent in the vicinity of large centers of population. The mosquito-
breeding areas in the vicinity of New York City, for example, have prevented the
growth of paying industries of various kinds, and have hindered the proper de-
velopment of large tracts to an amount which it is difficult to estimate in dollars
and cents and which is almost inconceivable. The same may be said for other
large cities near the sea-coast, and even of those inland in low-lying regions.

The development of the whole State of New Jersey has been held back by the
mosquito plague. This point has been insisted upon by Dr. John B. Smith, in
his excellent article entitled : “‘ The general economic importance of mosquitoes,”
in the Popular Science Monthly for April, 1907, and he has put it so strongly,
and he is so familiar with the New Jersey conditions, that we quote from his
article as follows:

“There is no exaggeration in the statement that the elimination of the mos-
quito would add ten millions to the taxable value of real estate in two years. [In
the vicinity of New York City?] Let me illustrate: New York City is a highly
desirable place of residence in winter; but less so in summer, and there are
thousands of residents of New York City who are well able to afford a summer
home within an hour or two from town, and who are quite willing to pay for it.
New Jersey has many places ideal in situation and accessibility, and one such
place developed rapidly to a certain point and there it stood, halted by the mos-

quitoes that bred in the surrounding marsh lands. Country club, golf, tennis
and other attractions ceased to attract when attention was necessarily focused
THE SALT-MARSH MOSQUITOES 329

on the biting or singing pests that intruded everywhere, and the tendency was to
sell out. But the owners were not ready to quit without a fight, and an improve-
ment society was formed which consulted with my office and followed my advice.
In one year the bulk of the breeding area was drained, mosquitoes have since
been absent almost entirely ; one gentleman, not a large owner, either, told me
his property had increased $50,000 in value, and new settlers began to come in.
This year one of the worst breeding areas of the olden day was used as a camping
ground and 100 new residences are planned for next year.

“New Jersey has miles of sea coast that is unequalled for summer resorts.
All but a few points are practically abandoned as uninhabitable. Barnegat Bay
and its surroundings constitute a fisherman’s paradise, and again and again
settlements have started, done well for a season and have been abandoned. Those
who came one year never came again, and many who came for a month stayed
only a day.

“ The only thing that prevents a continuous line of summer resorts along the
entire shore line is the mosquito pest, and were that removed there would be a
scramble to get land.

“We may take the result on Staten Island as an example. This Island, now a
part of Greater New York, is geographically a portion of New Jersey, separated
from the mainland by a narrow stream or ‘kill,’ on both sides of which salt
marsh flats extend for a mile or more to the highland. The southern and
eastern shore is a continuation of the New Jersey coast line from the mouth of
the Raritan River, and like it has a number of indentations more or less bordered
by salt marsh areas. On all these marshes mosquitoes bred in uncounted
millions and spread throughout the island. Result: several square miles of
most desirable territory for suburban residences entirely unsettled. There are
two shore resorts, South Beach and Midland Beach, feeble imitations of Coney
Island in some directions, but more desirable in others, that just maintained
themselves despite their attractions. During the day conditions were tolerable
along shore, but as soon as the sun was low in the horizon trouble began, and as
it became dusk the fight began, and pleasure seekers sought shelter behind
screens or started for home.

“ This past summer, under the supervision of Dr. A. H. Doty, state quarantine
officer, the salt marshes have been drained in the manner advocated by me, and
the beginning was made on the eastern and southern shores, where Midland and
South Beach are situated. I need hardly say that very few believed in good
results, and scepticism was general even in circles where we might have expected
material support. But we got the needed money, secured a contractor within
our estimate, and the eastern and southern shore work was done before the breed-
ing season set in.

“ Result: there have been very few mosquitoes of any kind, and practically no
marsh mosquitoes along this shore during the entire season. Visitors stayed
longer and came more frequently to both beaches, which enjoyed a season of
unparalleled prosperity, taxing the full capacity of the transportation companies.
As the season advanced, the drainage work extended farther and farther away
from the populated sections, permanent residents began to notice that nobody
was putting in screens, and that screened porches were never used. On the golf
links games could be carried on while the light lasted, and outdoor dinners
and suppers became the rule at the Country Club. When it was fully realized
that there was practically no mosquito pest, and the improvement in the char-
acter of the drained territory was obvious, there was a change in public senti-
ment. Plans were made for extending the attractions at the beaches, and many
thousands will be put into new amusement enterprises during the present winter.
Land values stiffened and very little was offered for sale.
330 MOSQUITOES OF NORTH AMERICA

“Two industrial enterprises decided to locate on the marsh area on the west
of the island, and these are expected to employ, respectively, 4000 and 6000
men, most of whom will undoubtedly settle near-by. These enterprises will
result in actually reclaiming a large section of the marsh, which is something
that mosquito drainage does not and was not intended to accomplish.”

A much earlier case of a similar nature to those described by Doctor Smith
has been elsewhere mentioned by one of us. Not far from a large town on the
north shore of Long Island Sound, prior to 1900, there was a stretch of land
lying in such a way that it afforded a large number of excellent cottage and
villa sites. But mosquitoes were so numerous there that even domestic animals
could not be kept in a healthy condition and, as a resident of a nearby village
expressed it, “ the sole population consisted of a few smoke-dried fishermen and
their dogs.” In this locality, by the enterprising work of one man, a company
was formed, the land was bought, the mosquito breeding-places were practically
abolished, summer residences were built, and the company realized many thou-
sands of dollars in the course of two years.

LOSS TO AGRICULTURE.

Agricultural regions have suffered from this cause. In portions of the North-
western States it has been necessary to cover the work-horses in the fields with
sheets during the day. In the Gulf region of Texas at times the market value
of live stock is greatly reduced by the abundance of these insects. In portions of
southern New Jersey there are lands eminently adapted to the dairying industry,
and the markets of New York, Philadelphia and the large New Jersey cities are
at hand. In these localities herds of cattle have been repeatedly established, but
the attacks by swarms of mosquitoes have reduced the yield of milk to such an
extent as to make the animals unprofitable, and dairying has been abandoned
for less remunerative occupations.

The conditions of the thoroughbred race horses at the great racing center,
Sheepshead Bay, Long Island, was so impaired by the attacks of mosquitoes as
to induce those interested to spend many thousands of dollars, a few years ago,
in an effort to abate the pest.

Smith, by way of example, calls attention to the indirect damage to the cran-
berry crop through mosquitoes. It seems that in New Jersey, about the time
when cranberries ripen, the country may become covered with swarms of mos-
quitoes from the salt marshes, and under such conditions it is impossible to get
pickers for the crop. He says that gangs of Italians have been brought down
from Philadelphia, and have begun to work in good spirit, but that by noon of
the same day they have been so badly bitten that they have had to give up the
work and return to the city. Such conditions do not occur every year, nor do
they last through the season, but they are of sufficiently frequent occurrence as
to make cranberry culture most uncertain since the farmer hesitates to start
the crop when he may be compelled to see the berries rot on the ground because
he can not get laborers who can stand the plague of the mosquitoes.
RECLAIMABLE LANDS 331

COST OF SCREENING.

In the economic loss caused by mosquitoes there should be included the outlay
for protective measures. All over the United States, for these insects, and for
the house fly as well, it has become necessary to screen habitations. The cost
of screening houses alone must surely exceed ten millions of dollars per annum,
especially if we add the expense of screening rain-water tanks in the Southern
cities.

THE VALUE OF RECLAIMED LANDS.*

“The general value of lands reclaimed from swamps is obvious. Practically
all of Holland has been reclaimed from the sea. Large areas of the most valu-
able farming land in the world have been reclaimed from nonproductive swamps.
To the nonproductiveness of swamp land must be added the great danger that
exists in its continuance through the invariable presence of disease-bearing mos-
quitoes. The drainage of swamps not only destroys unlimited breeding places
of mosquitoes, but vastly increases the value of the land for farming purposes
and for other utilitarian uses. Hither reason amply pays for the operation. The
late Prof. N.S. Shaler, in his report to the North Shore Improvement Associa-
tion, showed that fields gained by marsh drainage possess the greatest fertility
and their endurance to cropping without manuring exceeds that of any other
agricultural land except possibly arid regions which are irrigated. The range
of crops is great and includes all ordinary farm and garden crops except in some
places Indian corn. Reclaimed swamp lands are especially adapted for truck
farming, because it is easy to maintain the level of under-ground water where
the roots of the plants can reach it. Professor Shaler shows that the larger part
of the best irrigable land in Holland, and much of that in Belgium, northern
Germany and eastern England has been gained from what was originally tidal
fields. He estimates not less than 10,000 square miles in those countries to have
been redeemed in this way.

“ The only large example of diked and improved marshes in the northeastern
United States is at Green Harbor, Mass., where 1,200 acres have been won to
tillage, about one-half being used for hay fields and the other for different crops.
The result obtained in the farming of this land is excellent. Asparagus has
produced large crops continuously for more than twenty years without the use
of any fertilizer.

“ Prof. Milton Whitney, Chief of the Bureau of Soils, of the United States
Department of Agriculture, some years ago drew up the following statement at
the request of the writer, concerning the value of reclaimed swamp land:

“Swamp lands, by virtue of their position, become the repository of highly
fertile material washed from the uplands by the rains. As a general rule, the
immediate surface of any soil is the most fertile portion of that soil, resulting
from the fact that this surface material is in physical condition, and most ex-
posed to the action of the weather, the sun, rains, and air. This surface is the
first portion removed during rains, and is the portion carried down into the
swamps and deposited. When erosion goes on at such a rapid rate that both the
surface and the underlying raw soil are washed away, the resulting bottom land
deposit is frequently sterile. Witness the mud flats and swamps along the
Sacramento River, in California, which have been covered with mud from the
hydraulic mines of the Sierra Nevadas. Here large areas have been ruined by
the mud, and will not become fertile until the weather has acted upon the
material long enough to make the soil an acceptable medium for plant growth.

* Quoted from Howard, L. O., Preventive and remedial work against mosquitoes. U. 8S. Dept.

’

Agr., Bur, Bat., Bull. 88, pp. 53-62, 1910.
332 MOSQUITOES OF NORTH AMERICA

Fortunately, most of our lowlands and swamps receive only the more gentle
washing or the most fertile materials from the uplands.

“* Swamp lands contain an unusual amount of organic matter, and for that
reason are easy to maintain in proper tilth, light to work, and warm. From
their low position, water is generally abundant, or easy to obtain for irrigation
by pumping or diversion from nearby streams.

“« Swamp lands and tide marshes are considered the most valuable of lands
in the world’s older countries. Their inherent fertility is recognized, and the
ease with which they are cultivated and irrigated is greatly appreciated. In
England for two hundred years the tide lands have been under reclamation,
and to-day over 1,000,000 acres are in a ‘ matchless state of fertility.’

“Tn Holland extensive areas have been reclaimed from the sea. The greater
part of the country lies at or below the level of the sea, and is reclaimed from
a jungle of swamps and savannas. Holland to-day represents one of the most
successful attempts at swamp reclamation. Lakes have been drained by diking
and pumping, and plans are now on foot to drain the Zuyder Zee, an arm of
the ocean.

“¢ Tn our own country, swamp reclamation has been carried out on a large
scale in the Middle Western States. Ohio, Indiana, Illinois, Michigan, and
Wisconsin have great areas of productive land once swamp but now the most
fertile and reliable land in those States. The tide marshes around Puget
Sound, in Washington, have been lying untouched until within the last few years,
but the recent great influx of Scandinavians has resulted in a movement
toward the reclamation of these lands, and excellent farms are being established.

“¢In California one of the greatest areas of swamp peat land in the world
lies in the Sacramento-San Joaquin Delta. Over 1,500,000 areas of peat from
6 to 40 feet thick are ready for reduction in productive capacity, and to-day large
areas are being reclaimed. Yields of 500 bushels of potatoes, 6000 pounds of
asparagus, 60 bushels of barley and oats have been common, and with proper
farming such yields should continue to be common.

““¢ Wherever properly reclaimed swamp lands are found their fertility is
recognized ; almost without exception they are more fertile than surrounding
uplands. They are frequently used in special crop production, such as in grow-
ing celery, asparagus, cranberries, or onions, but in dairying or general farming
they are unexcelled as permanent pasture or hay land. The consensus of
opinion in districts where swamps have been reclaimed and farmed for many
years is that there is no more valuable portion of the farm than the swamp,
properly reclaimed.’

“ There is much swamp land in the United States within easy reach of the best
markets. New Orleans is surrounded by swamps, but here the problem of rec-
lamation is rendered exceedingly difficult owing to the vast area involved and
the periodic invasion by the Mississippi River in front, and Lakes Borgne and
Pontchartrain in the rear. The city of New York is in the immediate neighbor-
hood of vast areas of swamps and marshes, and even the partial drainage of this
land is being productive of admirable results. The great value of stable land
in the vicinity of New York for manufacturing purposes is uncontested, and even
the partial drainage of the breeding places of salt-marsh mosquitoes in portions
of New Jersey adjacent to New York has resulted, aside from limiting the mos-
quito supply, in the increase in value of the lands to the owners. After the first
ditching the crop of salt hay nearly doubles. The operations carried on con-
jointly between the city of Brooklyn and the town of Sheepshead Bay, a few
years ago, is indicative of the remunerative results to be obtained by simple and
beneficial operations. The contents of the ash barrels of the city of Brooklyn
were conveyed out into the salt marshes upon specially constructed trolley tracks
MARSH-LANDS FOR AGRICULTURE 333

and in large metal tanks. The tanks were so made that upon reaching the
terminus they were taken up by machinery, carried out by an overhead trolley
line, and by machinery dumped at a given spot. In this way some hundreds
of acres of salt marsh were covered with a 12-foot layer of the contents of the
ash barrels of Brooklyn. The layer was packed down by water and contained so
much organic matter that almost immediately grass and sun flowers began to
grow. At the end of the second year enough soil had formed so that Italians had
begun to plant cabbages and other vegetables.

“The Government is taking up the subject of reclamation of swamp lands
through its Reclamation Service, and extensive surveys are being made by the
United States Geological Survey. Under the United States Department of
Agriculture appropriations have been made for some years to enable the Secre-
tary of Agriculture to investigate and report upon the drainage of swamps and
other wet lands and to prepare plans for the removal of surplus waters by
drainage.

“A number of interesting and important publications have already been
issued by the United States Department of Agriculture, two of which are of
general interest, namely, Circular No. 74, Office of Experiment Stations, Ex-
cavating Machinery Used for Digging Ditches and Building Levees, by J. O.
Wright (pp. 40, figs. 16) ; and Circular No. 76, Office of Experiment Stations,
The Swamp and Overflowed Lands of the United States, by J. O. Wright (pp.
23, pl.1). The first of these publications described the use and construction of
different classes of dredges, including dipper, clam-shell, rotary, roller, scraper,
elevator, and hydraulic dredges, and drag boats; first cost and cost of operation
of dredges ; machines for building levees; machine for tile ditching. The second
gives an estimate of the area of swamp lands in the different States, its owner-
ship, present value, cost of reclamation, and probable value when reclaimed,
and discusses the state laws relating to drainage. It is shown in the latter
circular that there are in the United States 119,972 square miles of swamp lands,
an area which, collected together, would be as large as England, Ireland, Scot-
land and Wales together, or larger than the six New England States, New York
and the northern half of New Jersey. It would make a strip 133 miles wide
reaching from New York to Chicago. Not all of this swamp land, however, is
suited for agriculture, but from the data collected by the Office of Experiment
Stations of the United States Department of Agriculture, it seems certain that
in the eastern portion of the United States there are 77,000,000 acres that can be
reclaimed and made fit for cultivation by the building of simple engineering
structures. It is a noticeable and significant fact that 95 per cent of this entire
area is held in private ownership. The following paragraphs taken from this
Circular No. 76 express the desirability of such drainage from the monetary
point of view in very forcible terms:

“<There is no question as to the fertility of swamp or overflowed land, and
when it is protected by embankments to keep out the overflow and is relieved
of the excess of water by proper drainage its productiveness is unexcelled. In
nearly every one of the States large areas of similar lands have been reclaimed
by draining and embanking and have proven to be the most productive farm
lands in the districts in which they are located. Illinois, Indiana, Iowa, and
southern Louisiana have taken the lead in work of this kind, and in no other
part of the country do we find more profitable or higher-priced farms than in
those States. Along the Atlantic coast sufficient work has been done to indicate
that the vast extent of salt marsh reaching from Maine to Florida can by
proper methods be won to agriculture, and when reclaimed the soils are especially
adapted to market gardening.
334 MOSQUITOES OF NORTH AMERICA

“To ascertain why these lands have been allowed to remain so long in their
present state we must look to some cause other than their lack of fertility, as
this has been fully established by chemical analyses of the soil and by hundreds
of productive farms that have been made from such lands.

“< Tn the early settlement of our country the farms were located on what were
considered the most desirable tracts, determined by accessibility, natural water
supply, and the fertility of the soil. As civilization extended westward the home
seeker selected the rolling prairie that needed little or no drainage, so that the
swamps and overflowed lands were passed by, and only recently has an imperative
demand arisen for their reclamation. The desirable farming land is practically
all occupied or held for speculation, and to meet the needs of our steadily in-
creasing population it is necessary for this swamp land to be drained and put
to proper use. Its nearness to market and its great fertility make it very de-
sirable for small farms.

“¢ Can these lands be drained, what will it cost, and how can the work best be
done are questions of vital interest to the American people. After considering
what has been done to reclaim the marshes of Holland, two-fifths of which lie
below the level of the sea, and the difficulties that have been overcome in draining
the fens of England, it would be a reflection on the skill and intelligence of the
American engineer to proclaim the drainage of our swamp lands impossible.
On the contrary, the engineering problems are simple, as most of these lands
are several feet above sea level and have natural creeks or bayous that need only
to be improved by straightening, widening, and deepening to afford outlets for
complete drainage. In case of some of the river bottoms and the salt marsh
along the coast it is necessary to build levees to prevent overflow and to construct
internal systems of drainage with sluice gates or pumps to discharge the water
from within, and by the use of modern machinery this work is neither difficult
nor expensive. Levees can be built and ditches excavated with suitable dredges
at a cost ranging from 7 to 16 cents per cubic yard. Large works in swamps
where the land is overflowed are readily and cheaply constructed in this manner.

“As to the cost of draining these lands, and whether or not it will pay, we
have but to refer to the numerous works of this kind that have been completed.
In those States where large areas of swamp land have been thoroughly drained
by open ditches and tile drains the cost ranges from $6 to $20 per acre, while
in places where tile drainage was not required the average cost has not exceeded
$4 per acre. Judging from the prices which prevail in a large number of
these districts where work of this kind is being carried on, it is safe to estimate
that the 77,000,000 acres of swamp can be thoroughly drained and made fit for
cultivation at an average cost of $15 per acre. The market value of these lands
in their present shape ranges from $2 to $20 per acre, depending upon the
location and prospect of immediate drainage, with an average of probably $8
per acre. Similar lands in different sections of the country that have been
drained sell readily at $60 to $100 per acre at the completion of the work, and in
many instances, when situated near large cities, they have sold as high as $400
per acre. To determine whether or not it will pay to drain these lands we have
but to consider the following figures:

Cash value of 77,000,000 acres after thorough drain-

age at $60 per ACTE ....... cc cece cece ees $4,620,000,000
Present value of this land at $8 per acre.$ 616,000,000
Cost of drainage at $15 per acre........ 1,155,000,000

Value of land and cost of draining................. 1,771,000,000
Net increase in value........... cece eee $2,849,000,000
PUBLICATION 159 PLATE XI?

 

Operations of filling in salt marshes, Sheepshead Bay, Long Island, with the

garbage-can contents of Brooklyn.
PRODUCTIVITY OF SALT-MARSH LAND 339

“These figures, though large, are not fanciful, but are based on results ob-
tained in actual practice in different sections of the country where work of this
kind has been done. An extended investigation shows that in every case where
a complete system of drainage has been planned and carried out the land has
increased in value many fold. In some instances, however, much time and
money have been wasted because the work was undertaken without any well-
defined plan or it was not sufficient to afford adequate and complete drainage.

“«The reclamation of swamp and overflowed lands is no longer an experi-
ment ; it has become a highly profitable business when based on correct principles.
The methods of drainage practiced in different parts of this country and in some
of the foreign countries are being carefully considered, and many experiments
are being made to determine the best and most economical methods of draining
land, and the information thus collected is being classified and the results com-
pared and general rules deduced, which, if followed, will in all cases bring
highly beneficial results. The comparative cost of the different methods of
doing the work and the most satisfactory way of providing funds are also being
duly considered.

“ “Were this 77,000,000 acres of swamp and overflowed land drained and made
healthful and fit for agriculture and divided into farms of 40 acres each, it
would provide homes for 1,925,000 families. Swamp lands, when drained, are
extremely fertile, requiring but little commercial fertilizer, and yield abundant
crops. They are adapted to a wide range of products and in most instances are
convenient to good markets. While an income of $15 to $20 per acre in the
grain-producing States of the Middle West is considered profitable, much of the
swamp land in the East and South would, if cultivated in cabbage, onions, celery,
tomatoes, and other vegetables, yield a net income of more than $100 per acre.

“<Tn addition to the immediate benefits that accrue from the increased pro-
ductiveness of these lands, a greater and more lasting benefit would follow their
reclamation. The taxable value of the Commonwealth would be permanently
increased, and healthfulness of the community would be improved, mosquitoes
and malaria would be banished, and the construction of good roads made
possible. Factories, churches, and schools would open up, and instead of active
young farmers from the Mississippi Valley emigrating to Canada to seek cheap
lands they could find better homes within our own borders.

“¢ Holland, two-fifths of which lies below the level of the sea, has been re-
claimed by diking and draining, and now supports a population of 450 per
square mile. Her soil is no better than the marshes of this country, and her
climate not so good as that of the Southern States, yet we have within our
border an undeveloped empire ten times her area.

“¢There is no good reason why this condition should longer continue, and
it is to be hoped that the American people will soon take steps to abate this
nuisance and make these lands contribute to the support and upbuilding of the
nation.’

“Tn an important article by Mr. H. C. Weeks, in the Scientific American Sup-
plement for January 5, 1901, on the subject of drainage work, the following in-
teresting statements are made: : MG .

“¢ Cages exist, however, of persons being unwilling to be convinced, and con-
tinuing their opposition even after a successful reclamation, as are seen in the
official records of Massachusetts, while examinations by the State have shown a
great improvement in the sanitary and agricultural conditions. In the instance
of Green Harbor, in that State, it is shown that the death rate of the reclaimed
districts averages lower than the general death rate of the State, that there is a
steady increase in summer visitors, and that many houses are being built. The
testimony of persons of wide knowledge and ample experience in the science and
336 MOSQUITOES OF NORTH AMERICA

art of agriculture is adduced, showing the good results in that field, and yet it
fails to silence opposers. Besides mentioning the remarkably heavy crops of
hay, much preferred by his horses to the best from the uplands, also the excellent
crops of strawberries and vegetables raised in these lands, one such qualified
observer gives his experience as to asparagus in such convincing words that they
are quoted in full: ‘ While visiting the Marshfield Meadows on April 19, 1897,
I found asparagus already up, very nearly high enough to cut. I was surprised
at this, for my own asparagus had just appeared above the surface of the ground,
although growing on land so warm that I am usually first to ship native aspara-
gus to Boston market. I was also surprised at the size of the stalks, they being
much larger than the first set of stalks that appear on my land. When I consider
the fact that the land on which this asparagus was growing has produced large
crops every year for twenty years without fertilizers of any kind, and still pro-
duces better crops than my land, which has had $600 worth of fertilizers to the
acre applied to it during the last twenty years, it convinces me that this land, for
garden purposes, surpasses any which I have ever examined. .. .

“< We realize, in a measure, the great value of the material which nature has
for ages been storing up for man’s future use, if he be wise enough to avail him-
self of it.’

“The drainage work done by other countries has given many practical ex-
amples of beneficial results from the mosquito standpoint, and from other points
of view as well. The details have very recently become available, through the
kindness of the United States consul at Milan, Italy, of very extensive drainage
operations carried on near Milan, which involved the reclamation of nearly
80,000 acres of land. These details may be found in the Scientific American
Supplement No. 1637, May 18, 1907, pages 26233 to 26235. The work cost
$3,200,000, and the annual cost of operation is estimated at $16,000. The
beneficial results are summarized as follows:

“¢41, In both Mantua and Reggio this tract, comprising 77,867 acres, culti-
vable only for a sparse crop of poor hay and, on account of the vapors arising
from its stagnant swamps, dangerous for pasturage during practically all the
year, has been made cultivable, in one year, for wheat, grapes, fruits, and hay,
and rendered good for cutting into farms on which people can erect homes in
safety.

«2. The market values, not only on the 78,000-acre tract but on all con-
tiguous territory, even to the outer bounds of the affected provinces, have leaped
to figures equal to two or three times those prevailing before the opening of the
Bonifica, i. e., from $120 to $250 or $300 per acre.

“3, Farm labor, which formerly expressly avoided these provinces, and made
difficult the harvesting of the extensive crops, has been attracted there by the
changed conditions; while on account of the demand created by the active de-
velopment of the drained tract, wages have not been knocked down by the plenti-
tude of supply.

“¢4_ Live-stock maladies are under better control.

“5. The public health has been afforded a sure and scientific protection.’

“SALT MARSH LANDS IN NEW JERSEY.

“So much work has already been done in New Jersey that, as repeatedly
pointed out in this work, the value of the operations already carried on in that
State is very great, if only as an indication of what can be and should be done
elsewhere. The whole question of the New Jersey salt marsh and its improve-
ment has been considered by Dr. John B. Smith in Bulletin No. 207 of the New
Jersey Agricultural Experiment Station. In this work he gives a consideration
of the location of the salt-marsh area, the kinds of salt marsh, the vegetation on
eo

PUBLICATION 159

PLATE XIII

 

DRAINING THE SALT MarsH, Hackensack MEApows, NEW JERSEY, 1908.

1. The Manahan ditching spade.

3. Dragging out sod with ditching spade.

2.
4,

The ditching spade in use.

A long ditch dug with the ditching spade.
NEW JERSEY SALT-MARSHES 337

the marshes, the present value of the marshes, their actual value, effect of drain-
age on crops, the needs of salt grass and black grass, and a general consideration
as to how the marshes may be reclaimed and who is to pay the expense.

“Tt appears that the present value of the marshes is very small. As a matter
of fact, they are either not taxed at all or at such a low rate as to add little to the
income of the taxing body. Some of the owners have never paid any taxes, and
in some of the townships there is no record of ownerships in the assessor’s hands
and therefore no notices can be served. It is pointed out, as an evidence of the
recognized worthlessness of such land, that none who work on them consider in
the least the results of interference with natural drainage; railroads build em-
bankments across them, and pay no attention to the water courses except large
creeks. The result is that the marsh often becomes water-logged, and a good
salt-hay meadow is turned into a quagmire, and not even the owner protests.
Railroads cut sods from the meadows without inquiry as to the ownership of the
land, and holes of all sizes are scattered over the meadow, most of them uncon-
nected with tide water, leaving stagnant pools in which mosquitoes breed.

“ He points out that all salt marsh, of what he names the third type, which is
that area above mean high tide and more or less completely covered with vegeta-
tion, may be made to produce an income of from $10 to $40 per acre annually,
and that there are many hundreds of acres that do produce such incomes.

“Jn considering the effect of drainage upon crops he gives a number of in-
teresting instances, three of which are quoted:

«<The Newark meadow has an area of about 3500 acres, and hay has been cut
on parts of it for many years. Before the 90’s it was generally cut by men who
wished to use it as food for stock or as bedding, and some ditches were cut by
those who noticed that well-drained land produced much better crops than such
as were either too dry or water-logged. After the 90’s a number of banana
houses opened in Newark and created a demand for salt hay to use in layering
the ripening fruit. This demand led to the cutting of more territory around the
edges of the marsh, and $5 a ton was paid for the crop. With the introduction
and increase of the glass industry the demand for hay, to be used as packing, in-
creased steadily, and yet greater areas were cut; and in order to get at these
areas the cutting was done in the winter, after the meadow was frozen solid, for
at no other time could the product be carted off. And this was the condition
of affairs in 1904, when the mosquito drainage was done by the city, but under
the supervision of the writer. It might be said here that this drainage work was
not looked upon with any favor by owners and haymakers, the latter especially
protesting vigorously. One man threatened to smash the ditching machine, and
yet another promised to shoot the first man that set a spade into his property.
The work went on, nevertheless, and altogether nearly 400,000 feet of ditches
went into this 3500 acres.

“¢ The results are as follows: On the Hamburg section, where in 1903, on an
area nearly one mile square, about 100 tons of hay were taken off during the
winter, 250 tons were carted off in 1904, only one year later. The meadow has
hardened up right along, and in 1907 nearly the entire area was cut by machine,
and a crop of 800 tons, valued at $7.50 per ton, is harvested. Yet a worse place
was the area, about one by three-fourths of a mile, known as the Ebeling tract,
little more than a sunken meadow before 1904, from which no more than 30 tons
of usable grass were obtained. After the ditching the meadow began to rise
and improve, and at present writing is at least seven inches above its 1903 level,
and correspondingly improved in texture. The crop has increased from 30
tons to 600 tons, not quite so good as the other, but worth an average of $7 per
ton. Other areas which had theretofore produced nothing are now being cut.
338 MOSQUITOES OF NORTH AMERICA

The total cut in 1903 was between 1000 and 1200 tons; the 1907 crop will come
close to 3000. And that is not the limit of productiveness.

“< Forty years ago the Elizabeth marshes,-containing about 2200 acres, were
quite generally cut over and good crops of hay were obtained. There was con-
siderable ditching done, but it was not kept up, and as the marsh was crossed and
cut up by the railroads without regard to the drainage system, matters became
gradually worse; the meadow rotted, the black and salt grass was replaced by
sedges and other useless stuff, and less and less was cut each year until, for a
decade past, little or nothing has been cut from the area west of the Central Rail-
road. Where as much as 5000 tons had once been harvested, less than a thousand
tons were harvested in 1903. In 1906 ditches were cut in the southeastern sec-
tion of the meadow in the course of the mosquito work, and an area on which
hip boots were needed in that year can now be safely traveled dry shod. Where
we found sedge and useless grasses over two-thirds of the area in 1905, on that
same proportion we now have good salt and black grass. In another year, if
the ditches are not interfered with, the sedge will be practically out. The
balance of the area was ditched early in 1907, all the work being completed early
in July. Shallow depressions that have been water covered and mosquito
breeders for twenty years are now dry and covered with the salt-marsh flea-bane.
The grass which was ten to twelve inches high last year is now twenty to twenty-
eight inches high and much more dense. For the first time in nearly twenty
years hay is being again cut in areas west of the railroad and in the area between
Great Island, Elizabethport and the Central Railroad.

“Tn draining the Shrewsbury River marshes in 1904, the same sort of opposi-
tion from hay producers was encountered that we met on the Newark marshes,
and it was objected that the ditches cut up the land and made work harder.
Nevertheless, the work was done and the result is a crop just double—mostly
from longer, thicker grass. Before 1904, two tons per acre was considered a good
crop; now, good and bad together, it averages four tons, and local conditions
furnish a market that pays $10 per ton.’

“Tn his annual report for the year 1908, Doctor Smith states that his investi-
gations showed that a very small part of the salt-marsh area produces as great
a crop as it should, and that what is produced does not bring as good a price as
it should. The market for salt hay is slight, due in part to the character of the
crop and partly to the uses to which it is put. Since the crop is not certain it
can not be relied upon, and the price varies with the size of the harvest. Salt hay
is used largely for packing, and the amount demanded depends upon business
conditions. In 1907 there was a very large crop of hay, but there was a business
depression at the same time which brought about so low a price as to scarcely
repay harvesting. He shows that salt hay is altogether too valuable to be used
for packing material alone, and that if an annual crop could be expected it could
be used to supplement upland hay in feeding horses and cattle. The drainage
work done by Doctor Smith under the state mosquito law will put the meadows
into such shape that the amount of hay produced will be increased without in-
crease of cost except in harvesting, and will enable the production of dependable
crops. He states that on July 21, 1908, he had the opportunity of seeing, at
Stratford, Conn., an area of about 1500 acres of salt marsh, drained and partly
diked and reclaimed. The largest part of the acreage was devoted to raising
salt hay of the best quality, for which good prices were received. On the diked
marsh 100 acres had been kept free from salt water since 1904. On this terri-
tory strawberries, asparagus, onions, and celery were being raised, and, while
the asparagus was not of the best quality and the strawberry plants were in no
way unusual, the onions and celery were of the best—in fact the celery was so
good that most of the market gardeners in that vicinity preferred to get their
supplies from this source.
MOSQUITO MIGRATIONS 339

“Doctor Smith points out that there are many hundreds of acres along the
shores of Barnegat Bay, and especially along its upper portion, where a very
small amount of diking will serve to keep out salt water and fit the land for
certain truck crops. He also shows that along a large portion of the Barnegat
Bay line cranberry plants grow annually to the very edge of the salt-marsh line,
but that these could not be improved because there was no -way out across the
marsh for surface water. With the ditching going on, this land will become
available in large part at least and will allow the owners to derive a revenue
from land which is at present practically nonproductive. Of course taxes will
then be oo and the income of the townships in which this land lies will be
increased.’

INFLUENCE OF WIND ON THE DISPERSAL OF MOSQUITOES.

The majority of mosquitoes do not appear to fly very far. Those of the genus
Anopheles are seldom found more than a half mile from their breeding-places.
The evidence as to mosquitoes being carried by winds is unsatisfactory and more
or less conflicting ; this is doubtless due partly to the fact that species of differ-
ent habits are involved and partly to the unscientific character of the observa-
tions. It must also be remembered that the records are sure to be shaped in
accordance with the preconceived ideas of the observer. The common house mos-
quitoes are seldom found far away from their breeding-places. The salt-marsh
mosquitoes, however, migrate, possibly sometimes aided by the wind, but, as
recent evidence shows, more probably flying into the wind. The more careful
observations on mosquito behavior show that for the most part mosquitoes will
not fly when there is a strong breeze. Possibly the only exceptions are the mos-
quitoes of the northern prairies, where the low night temperatures oblige them
to be active during the day in spite of the constant high wind. Full accounts of
two remarkable mosquito migrations, observed by the Hon. J. D. Mitchell, of
Victoria, Texas, are given on pages 22 to 24 of “ Mosquitoes” (Howard).
These are of sufficient interest to quote in full:

“T have witnessed, in my life, two migrations of mosquitoes, that will always
be fresh and vivid in my memory.

“Where the Colorado River empties into Matagorda Bay, a marsh is formed
over the lowlands, by a raft in the river; this marsh contains about eighteen
square miles, and is a magnificent breeding-place for mosquitoes.

“ T used to ranch it on the peninsula-like body of land, formed by Carancahua
Bay on the east, Matagorda Bay on the south, Keller’s Bay and Creek on the
west, and the Calhoun County north line on the north (refer to coast maps
of Texas). The distance between my.ranch property and the marsh above
described is, by bay route, about forty miles ; the way the crow flies, about thirty-
five miles. My ranch was situated on Carancahua Bay, near the north end of
land.

“The first migration occurred in October, 1879. There had been an overflow
from the upper country, which filled the aforesaid marsh, but the balance of that
section was very dry and needing rain, and there were no mosquitoes. A fairly
strong easterly wind had been blowing for three days ; on the evening of the third
day the mosquitoes arrived, flying high, about fifty feet, and looking like a cloud
or mist over Carancahua Bay. At the ranch they set everything on fire that had
blood in it, and all work was suspended by unanimous consent. Cattle and
horses rounded-up milled continuously ; all work stock was turned loose as quick

23
340 MOSQUITOES OF NORTH AMERICA

as possible and they went to the round-ups at full speed, and little or nothing was
done for nearly five days ; by this time the main body had passed, though plenty
remained to make everything uncomfortable for about two weeks. This migra-
tion was from east to west and the line was about three miles wide—above and
below this there were no mosquitoes.

“Migration No. 2 occurred in October, 1886. They came from the same
marsh before described—this migration confined itself to the Matagorda Bay
shore line, reaching inland about half a mile; there were as many mosquitoes
in this limit as there were in the three miles of migration No. 1. They clouded
the sky, bent down the grass with their weight, and made all driftwood and
ground the same color. All stock left the shore and went north outside of the
line of marsh. The wind was light and from the south, and did not affect the
mosquitoes in their flight, which was westward ; the main flight was low, ten or
twelve feet high and always in the same direction. With three other men I rode
into the swarm to a large pile of drift and trash and set it on fire, and stood in
the smoke for some time watching them. They passed sometime during the
third day, leaving very few stragglers behind. By inquiry, I traced both of
these swarms from the marsh before described to fifteen or twenty miles west
of my ranch, a total distance, air line, of fifty or sixty miles.

“ No. 1 crossed Trupalacios Bay, where it was five miles wide, and Carancahua
Bay, where it was one mile wide. No. 2 holding to the shore line, crossed
Trupalacios Bay, three miles, Carancahua Bay, at Pass, 300 yards, Keller’s Bay,
oe half mile, Cox’s Bay, one and a half miles, and Port Lavaca Bay, four
miles.

When Dr. John B. Smith began his work in New Jersey nothing exact was
known of the breeding habits of the salt-marsh mosquitoes, or of their powers of
migration. The fact of their ability to migrate was denied by nearly all ento-
mologists. Doctor Smith’s early work resulted in the determination of the life-
history of Aédes sollicitans, and his later work, that in 1903-4, resulted in a
complete demonstration of the migratory habits of A. sollicitans, A. cantator and
A. teniorhynchus. He was led to investigate the matter carefully on account
of the fact that anti-mosquito operations carried on in certain New Jersey towns,
on the theory that the entire mosquito supply was bred locally, were unsuccessful ;
furthermore, the salt-marsh mosquitoes were found far inland and in numbers
too large to have been carried by trains ; and lastly, experiments indicated that
they would not breed in fresh water. The controlling argument was the pres-
ence in overwhelming numbers of adult salt-marsh mosquitoes where no trace
of their larve could be found. Doctor Smith had previously watched sollicitans
carefully on many occasions and had found that it flies quite readily against even
a brisk wind, and makes good progress. He placed himself several times in an
alley in the direct line of the wind and watched the mosquitoes come sailing
against it without apparent effort. He had driven, as have many of us, over
infested roads at quite a rapid pace, and had found that the mosquitoes hovering
over the horse and about the carriage had no difficulty in keeping up. He had
been in a steam launch which was followed by a mosquito swarm for more than
five miles across an open stretch of water.

In order to understand the sudden appearance of great numbers of mosquitoes
on the salt marshes and their subsequent migration a knowledge of the breeding
DISTANCE OF FLIGHT 341

habits of these mosquitoes is essential. These are discussed in another part of
this work (p. 146).

Dr. Smith’s method of investigating the migrations of the salt-marsh mos-
quitoes was to station observers on the marshes before the larvee matured. Care-
ful search was made for several miles back in order to prove that none of these
mosquitoes were there. Then the appearance of the first brood of adults on the
salt marshes was noted early in the season. They were watched for a day or two
slowly advancing until they reached the first ridge of mountains. A second
brood, maturing during the last days of June, 1903, was watched in the same
way, and the early days of July brought inland the greatest swarm of mos-
quitoes he had even seen. They reached New Brunswick July 2d and included
the three species above mentioned. One of.Dr. Smith’s assistants, Mr. Viereck,
was, at the same time, observing at Cape May, and watched the peninsula filling
with sollicitans bred at the shore. Away from the shore he could not find the
larvee, while the adults swarmed. He noted that after continuous south wind
the marshes became practically free from mosquitoes, whereas a few days later
blood-filled specimens with developing or developed ovaries returned to the
marshes from the upland. This, he thought, was a return migration for ovi-
position, all the specimens being worn. Dr. Smith now has no hesitation in
stating that these salt-marsh species may migrate inland for 40 miles.

Flights to sea are apparently not infrequent, although they have been but
seldom recorded. According to Dr. Smith salt-marsh mosquitoes are not un-
common 5 miles out, and have been reported 15 miles out.

Dr. H. R. Carter, discussing this subject in 1904, thinks that salt-marsh mos-
quitoes are “ quite frequently carried considerably over a mile by light, steady
breezes, long continued.” He records the occurrence of a great swarm of salt-
marsh mosquitoes in the Gulf of Mexico, many miles from land, as follows:
“The writer has personal knowledge of the flights of myriads of mosquitos
(Culex solicitans as he remembers) which were carried by wind fifteen or
eighteen miles from the Louisiana marshes across Chandeleur Sound to vessels
in the sound and to Chandeleur Island. In both cases the wind had blown
moderately and steadily for two or three days from the marshes.”

Dr. Alfred G. Mayer, the Director of the Marine Laboratory of the Carnegie
Institution at Tortugas, Florida, found that the Tortugas Islands are occasion-
ally invaded by swarms of migratory mosquitoes. He investigated the conditions
on the seven islands carefully in 1908 with reference to possible breeding-places
of mosquitoes and he describes these as follows:

“The seven Islands of the Dry Tortugas, Florida, are composed exclusively
of wave-worn and wind-blown fragments of shells and other calcareous remnants
of marine animals and plants which once lived in the water surrounding the
keys. These particles form a loose, coarse, soil which does not permit the
growth of mangroves, and which is so porous that no puddles or standing pools
of water are to be seen even immediately after the most copious tropical rains.
There are no enclosed lagoons or areas of relatively stagnant salt-water as in

many other keys of the Florida-Bahama region, and all parts of the Islands are
dry and elevated from 3 to 9 feet above sea-level. The islands are covered with
342 MOSQUITOES OF NORTH AMERICA

bay cedar bushes, cactus, and coarse grasses, and it is certain that there are no
natural breeding places for mosquitoes within the group.

“On Garden Key Stegomyia [Aédes calopus] breeds within the numerous
cisterns of Fort Jefferson. No mosquito larve have ever been seen during ten
years of observation in the cisterns of the light-house on Loggerhead Key ; this
being doubtless due to the purity of the water which is collected upon slate roofs
and runs at once into the concrete cisterns.

“The iron cisterns of the Carnegie Institution Laboratory, also on Logger-
head Key, are covered with kerosene oil, and no mosquitoes breed within them.
All tin cans and garbage on Loggerhead Key are towed daily out to sea and cast
over-board.

“JT mention these details merely to show that mosquitoes can breed only on
Garden Key, Tortugas, the other Islands of the group affording no suitable places
for this purpose.”

Dr. Mayer informs us that no mosquitoes other than Aédes calopus breed
upon the Tortugas and that the nearest breeding-grounds for other species are
upon the Marquesas Keys which are the lands nearest to the Tortugas group, and
lie 40 nautical miles to the eastward of Loggerhead Key. The Marquesas are
low-lying mud flats covered by a dense growth of mangrove bushes and Dr.
Mayer states that myriads of mosquitoes breed there during the summer season.
“ On damp, but rainless days, when the sky is over-cast, and the wind blows from
Marquesas toward the Tortugas, mosquitoes in considerable numbers suddenly
appear upon Loggerhead Key. They also drift upon the Tortugas during damp
moonlight nights, but it is remarkable that when the wind shifts and blows from
some direction other than that from the Marquesas the mosquitoes disappear
from Tortugas in a few hours.” At our request, Dr. Mayer has secured a speci-
men of one of these mosquitoes which he secured in 1910. It proved to be
Aédes niger, the Antillean form of Aédes teniorhynchus which extends over to
Florida. The last-named species is the one for which the migratory habit is
best established. Dr. Mayer even thought that mosquitoes occasionally crossed
from Cuba, a distance of 90 miles, but such a distance is considerably in excess
of anything observed by others. It must be considered that Dr. Mayer’s state-
ments, as well as those of others, are based upon the assumption that the mos-
quitoes are carried by the wind or fly with it. This is by no means demonstrated.

Other observers have found that these mosquitoes fly against the wind. One
of us (Knab) has observed that in Saskatchewan the most abundant mosquito
of that region (Aédes spenceri) flies against a strong wind. Mr. A. H. Jennings
has informed us that in his investigations in Panama he found that Anopheles
invariably flew against the wind. With reference to Prof. Mayer’s belief that
mosquitoes fly from Cuba to the Tortugas, a distance of 90 miles, we could
only accept this in the presence of convincing proof. Investigations will have to
be carried on much more thoroughly before any conclusion can be reached re-
garding the origin of the mosquitoes found in the Dry Tortugas.

In August, 1909, many newspapers contained accounts of the appearance of
a swarm of mosquitoes in the Gulf of Mexico, sixty miles from the nearest land,
and on August 24 a sheet of marine data from the U. S. Hydrographic Office was
received at he Bureau of Entomology, filled out by Captain Young of the steam-
DISTANCE OF FLIGHT 343

ship “ Concho,” Key West to Galveston, as follows: “Civil data Aug. 6, 09;
Ship’s time 10 a. m.; Latitude 28.40; Longitude (Greenwich) 92.30; Cloud of
mosquitoes large, lazy and hungry. Wind N. E. Moderate at the time. The
above mosquitoes were about 60 miles from the nearest land. I never before ex-
perienced mosquitoes over 5 miles from land, and only a few times even at that
distance.” No specimens of the mosquitoes were received, but in view of Mr.
Mitchell’s observations quoted above, there seems no reason to doubt the explicit
record of Captain Young to the Hydrographic Office of the United States gov-
ernment.

Grubbs, in a paper previously quoted, in the course of his investigations of
vessels as carriers of mosquitoes, at the Gulf Quarantine Station, concludes from
evidence submitted that in seven cases of sailing vessels in the Gulf of Mexico
mosquitoes came aboard ; in two instances two miles from shore, in one instance
ten miles from shore, in three instances fifteen miles, and in one instance twenty
miles. Among these mosquitoes there were no malarial or yellow fever forms,
all belonging to species of Aédes.

The following paragraphs are taken from a letter received in 1903 from
Surgeon A. C. H. Russell, United States Navy, of the U. S. F. 8S. “ Newark,”
written at Port of Spain, Trinidad. These paragraphs contain an important
contribution to the subject under discussion:

“ At Montevideo, Uruguay, while the ‘ Newark’ and the ‘ Detroit’ were at
anchor more than two miles from the shore, mosquitoes in considerable numbers
were frequently blown on board by the land breeze. I send you a specimen of
these mosquitoes, which I caught in my cabin last June. The land breeze which
brought them off was moderate in force. [The species proved to be Anopheles
annulipalpis Arrib.]

“ At Ilha Grande, Brazil, mosquitoes were blown or flew on board the ships
at anchor more than a mile from shore. .. .

“ While the ‘ Detroit’ was at target practice in June, 1903, off the English
Banks, River Plate, nine miles from Flores Island and fourteen or fifteen miles
from the mainland of Uruguay, a moderate breeze blew mosquitoes on board in
swarms during several days and nights. The insects were most numerous at
night. The opposite shore of the river was from sixty to a hundred miles away.
These mosquitoes were small, delicate and black colored. Unfortunately no
specimen of them was caught and preserved.

“ Lieutenant Commander J. H. Hetherington, U. 8. N., states that, while he
was attached to the U. S. Coast and Geodetic Steamer ‘ Gedney’ in the spring
of 1884, the ship went out one morning early to take soundings on a shoal to the
eastward and southward of Galveston, Texas. Just after anchoring at the shoal
about 9 o’clock a. m., a heavy squall of rain passed over the ship from the west-
ward, After it had rained hard for a few minutes the weather became clear and
warm. As soon as the rain ceased, it was seen that the ship was infested with a
dense swarm of large, black or dark looking mosquitoes that were unusually
voracious and immediately attacked every one. In a few hours they had entirely
disappeared. The ship was at that time about 27 miles from land.

“The mosquitoes ordinarily noticed on board ship in Galveston Harbor were
of a light brown color, and smaller than those which came with the squall above
mentioned. . ;

“ Manson states in his work on tropical diseases that ships anchored a mile
from shore are safe from infection by mosquitoes. The experience of our ships
344 MOSQUITOES OF NORTH AMERICA

at Montevideo and at Ilha Grande shows that this distance does not afford such
protection and that the crew of a ship in any port, of the harbor of Rio for
example, is liable to be infested by mosquitoes.”

Of course Manson meant infested by Anopheles or other disease-bearing mos-
quitoes. Surgeon Russell found Anopheles only in one case; and its presence
on board ship about two miles from shore can not be accepted as proof that
the mosquito had flown this distance.

It is evident from the foregoing that the mosquitoes concerned in migrations,
in the strict sense of that term, are the coast species of Aédes. In the regions
we have under consideration in this work the species concerned are Aédes
teniorhynchus, A. niger, A. sollicitans and, along the northern portion of the
Atlantic coast, Aédes cantator. It appears from the observations of H. J. Quayle
that on the California coast Aédes quaylei and Aédes squamiger behave in a
similar manner.

Only the females are concerned in these migrations and there is little reason
to doubt that their object is to obtain food. It is probable that those females
which obtain blood and survive accidents return to the salt marshes to deposit
their eggs. It is doubtful, however, that in these migrations the wind is a neces-
sary factor or even that, in most cases, it has an important influence. In other
words we must consider those cases in which large swarms of mosquitoes are
said to have been carried a considerable distance by the wind as problematical.

The following observations, in so far as they relate to one of the so-called
house mosquitoes, which have entirely different habits from those already con-
sidered, are of some interest. We quote directly from “ Mosquitoes in Hawaii ”
by D. L. Van Dine:

“The writer has not observed evidences of migration among the species of
mosquitoes occurring in these Islands. Invariably the source of mosquitoes in-
festing any district has been found to be nearby natural and artificial collections
of water, usually artificial collections in the immediate vicinity. Mr. [H. W.]
Henshaw, in speaking of invasions of mosquitoes, says in a letter to the writer:

“So far as my own observations extend such accidental invasions of mos-
quitoes are rare in these Islands, the insects here as a rule being extremely local.
Nevertheless that such accidental dispersal of the pests in the Islands does
actually occur is proved by an instance in point which came under my personal
observation in June, 1899, at Pahala, Kau (Island of Hawaii). Mr. C. M.
Walton, the then manager of the plantation, informed me that prior to the visi-
tation of the pests about to be described, mosquitoes were practically unknown
about the village; if found at all it was in such small numbers as to cause no
annoyance, and mosquito-nets were unknown.

“ In the spring of 1899 there was an unusual quantity of waste water from the
mill and this ran down to the flats about a mile below and there formed a series
of small ponds aggregating a considerable expanse of shallow water. Not long
after the formation of the ponds swarms of mosquitoes made their appearance
about the mill and in all the dwellings, evidently brought there by the strong
trade winds which blew directly from the ponds. At the time of my visit the
mosquitoes (Culex pipiens *) put in an appearance about dusk and soon ren-
dered life a burden and sleep impossible except under nets which every house-
holder had been compelled to provide for every bed.

 

* The mosquito under consideration Is Culew quinquefasciatus, Say.
MOSQUITOES AND TRANSPORTATION 345

“ A few days later I visited the Kapapala Ranch, distant from Pahala about
four miles in an air line and about five miles from the ponds in question and
there found a similar state of affairs. Mr. Julian Monserratt, manager of the
ranch, told me that the invasion occurred at the same time as at Pahala prior to
which no mosquitoes had been seen at or near the ranch headquarters where,
indeed, there was no possible breeding place for them.

“ Unquestionably the clouds of mosquitoes originated in the same ponds below
Pahala and were carried by the trade winds not only to Kapapala but for miles
over the surrounding country in the direct track of the breezes. At Pahala, at
least, the colonization has proved to be permanent as here, as elsewhere on cane
plantations where water flumes are in use, leaky flumes form small pools at many
points along their track which make ideal breeding places for mosquitoes. .

“Mr. Henshaw has since informed the writer that the ponds mentioned are
quite exposed and unsheltered by vegetation, and agrees with the writer that had
the ponds been surrounded by trees or had vegetation intervened to which the
insects could have clung for shelter, the distribution would not, probably, have
been so widespread.”

It is doubtful that the trade wind played the réle in the dispersal of these
mosquitoes attributed to it by Mr. Henshaw. It should be noted that Culex
quinquefasciatus is nocturnal and it is well known that the trade wind dies down
at night. The mosquito’s greatest activity therefore occurs at the time when the
air is calmest. It does not follow from Mr. Henshaw’s account that he actually
saw the mosquitoes being carried by the wind; he found the mosquitoes and
concluded that the wind had brought them. This last criticism will also apply
to a very large part of the previously quoted observations.

CARRIAGE OF MOSQUITOES BY SHIPS, RAILROADS, AND
OTHER CONVEYANCES.

Just as is the case with many insects now cosmopolitan and which have been
taken from their original home to other parts of the world through the opera-
tions of commerce, mosquitoes are carried not only from one part of a given
country to another in carriages, in railroad trains and on river boats, but they
have been, and are yet, to a more limited extent perhaps, carried from one
country to another by ocean vessels. It seems reasonably well established that
Hawaii had no aboriginal mosquito fauna and that the mosquitoes found there
were brought over in sailing vessels many years ago ; these could only have main-
tained themselves during a long voyage by breeding in the water supply of those
vessels. In this way it is a practical certainty that the yellow fever outbreak in
Philadelphia in 1793, and the other less grave epidemics in northern cities pre-
ceding and following that notable occurrence, were brought about by the arrival
in these ports, at the proper season of the year, of sailing vessels from the West
Indies carrying Aédes calopus. Perhaps these mosquitoes were already infected,
or breeding in the water supply of the vessels, biting yellow-fever patients on
board at the proper period, and afterward healthy individuals, would perpetuate
the disease. Such a vessel tying up to a wharf might emit many infected mos-
quitoes which, biting persons on land, and subsequently breeding in numbers in
water barrels or other accumulations of fresh water on or near the wharves,
346 MOSQUITOES OF NORTH AMERICA

would start an epidemic which would progress gradually inland from the water
front, as was the case in Philadelphia and in other places. The same method of
travel accounts also for the European outbreaks. The shortening of sea voyages
by the introduction of steam has, in a way, increased the possibility of mosquito
carriage from one place to another; but, in another way, it has lessened this
possibility, since the water supplies of ships are of late years, as a rule, so kept
that mosquitoes can not breed in them.

The natural geographical distribution of the yellow-fever mosquito, now well
known to coincide with the tropical and subtropical life zones, does not limit its
possibilities in this direction. As is shown in the section on the geographic dis-
tribution in the United States the yellow-fever mosquito is often found in mid-
summer or late summer breeding north of its permanent range, only to die out
there with the winter. This can be only when it is carried north by artificial con-
veyances during the summer, flying out and breeding for a generation or so
where proper breeding-places are at hand. Thus, in August, 1904, it was found
to be breeding on the grounds of the Exposition at St. Louis. The yellow-fever
mosquito is particularly adapted to such carriage. In the late summer of 1908
one was found in Washington, D. C., in all probability brought up from the
South on a through train over one of the southern railroads.

One of the writers (Howard) has often gone to bed in a sleeping car at New
Orleans and suffered all night from mosquitoes which were carried along with
the train. Mr. J. O. Martin, an entomologist and good observer, in September,
1901, coming to Washington on the train from New Orleans, noticed that at
nightfall the train stopped in a swamp just outside of New Orleans, and mos-
quitoes came in through the open windows in very large numbers. Mr. Martin,
knowing what had been written about the carriage of mosquitoes by railroad
trains, noticed carefully the rest of the journey and states that a considerable
proportion of the mosquitoes which entered the train just outside of New
Orleans were still in the train on its arrival in Washington.

A number of instances have been published where mosquitoes were introduced
into new localities by the rearrangement of trains and the putting on of night
trains on railroads where there had previously been no night service. Some of
these are mentioned in “ Mosquitoes ” (Howard). One of these instances relates
to the introduction of mosquitoes into the City of Mexico. Since its publication
the writers have been informed by Prof. A. L. Herrera, of the City of Mexico,
that the statement that mosquitoes were first brought to the City of Mexico from
Vera Cruz on the completion of the railroad from the gulf to the city, is in-
correct, but that they first made their appearance in the City of Mexico in 1885,
on the completion of the Mexican National Railroad, having been brought down
from the valley of the Rio Grande at Neuvo Laredo. Prof. Herrera further
stated that during the summer time almost every train from the north brings
many mosquitoes down to the City of Mexico. These escape from the cars, take
advantage of the abundant breeding-places and soon multiply excessively. This
statement was made in 1902. Since that date the admirable sanitary work in
the City of Mexico, under the direction of Dr. Liceaga, has greatly reduced the
mosquito breeding-places of that city.
SPREAD TO NEW HABITATS 347

In regard to steamships the same general facts hold. Mr. Busck has found
the yellow-fever mosquito on a steamer a day out from Jamaica, and he also
found it on board a Ward Line steamer in New York harbor.

An excellent and suggestive paper on “ Fruit Vessels, Mosquitoes and Yellow
Fever,” was read before the Louisiana State Medical Society at New Orleans,
April 28, 1903, by Dr. Edmond Souchon, then president of the Louisiana State
Board of Health, and afterwards printed in the Journal of the American Medical
Association for June 13, 1903. Careful collections were made of the mosquitoes
arriving at New Orleans on board fruit vessels from Central American ports,
and these mosquitoes were determined in Washington at the Bureau of Ento-
mology. This paper, while indicating a great improvement over old conditions,
still, at the same time, showed how in previous years yellow fever had been
brought to New Orleans.

The habit of Aédes calopus of seeking dark and protected places for hiding is
well known to everyone who has observed it. It will crawl into pockets, under
coat lapels, and under turned-up trouser-ends, or it will hide in the folds of
garments hung in closets or upon the walls of a bedroom. Having these habits,
it is extremely liable, as Finlay already pointed out in 1881, to be transported
from one place to another in trunks. Garments folded in New Orleans and
packed loosely into a trunk may give out calopus hundreds of miles away.

The gradual spread of the yellow-fever mosquito from lower altitudes to
higher ones in Mexico has been pointed out in the general consideration of the
habits of this insect, but it should be here stated that while this species breeds
naturally throughout the moist tropical regions near the Gulf of Mexico and
near the Pacific, its carriage to higher altitudes on the railroads running up
from Tampico and Vera Cruz is an almost daily occurrence. Through this
constant carriage on railway trains the species has become established at higher
altitudes where the conditions are suitable. Thus, at Cordoba it established
itself at first in the immediate vicinity of the railway station and gradually
spread upward from this center year after year until now it may be found breed-
ing in the center of the town, at a considerable distance from the station. The
same thing occurred still higher, at Orizaba (4200 feet). It has established
itself at Carasal on the Inter-Oceanic Railway. It also occurs at points on the
railway from Tampico to Monterey (1600 feet) and it has been found in the
summer time at Saltillo—much higher than Monterey. It is doubtful whether,
had the railroads not been constructed, the yellow-fever mosquito would have
ever become established at many of these elevated inland localities.

Mr. C. P. Lounsbury, government entomologist of the Cape of Good Hope, is
authority for the statement that the railroads in Cape Colony have been re-
sponsible for taking mosquitoes to many inland towns which before the introduc-
tion of train service were quite free from this pest.

Skuse, writing of Culex quinquefasciatus, considers that it was introduced into
Australia from Europe by sailing vessels and says: “ As the railway lines ex-
tend so this mosquito reaches portions of the country often hitherto exempt from
it, and it has been, and is being, communicated to other places along the coasts
by water traffic ” (Proc. Linn. Soc. N. 8. W., ser. 2, vol. 3, 1889, p. 1718).
348 MOSQUITOES OF NORTH AMERICA

Not only by sailing vessels, steamships, and railroad trains are mosquitoes
carried without flying. Grassi has stated that he counted 200 specimens of
Anopheles on the inside of a stage coach during a drive lasting two hours through
the plains of Capaccio, and the same observer also, by the way, has recorded the
capture of Anopheles in a railway carriage traveling from Florence to Berlin.
Mr. J. K. Thibault, Jr., of Scott, Arkansas, in a letter to the senior author, states
that in his region mosquitoes are constantly being transported over the country
by buggies, covered wagons, and even, in the case of Aédes cyanescens, on the
backs of horses. He has known Anopheles quadrimaculatus and Culex abomi-
nator to be quite frequently carried forty miles in a day, and as they will not
leave a vehicle while it is in motion, it will be seen that they may travel even
greater distances. One of the writers has never suffered more severely from the
attacks of mosquitoes than in a night drive in Louisiana in the autumn of 1907.
The stage in which he was driving for a number of miles in company with Mr.
W. D. Hunter, of the Bureau of Entomology, seemed filled with most vicious
mosquitoes which made no attempt to leave the vehicle, but remained in it from
the banks of the Mississippi River to the point of destination.

Goeldi, in his “ Os mosquitos no Par4,” expresses the belief that the steamers
on the river Amazon are responsible for a wholesale carriage of the yellow-fever
mosquito and for its general introduction into all of the small towns far up the
river; he attributes to this source the introduction of yellow fever at Yquitos,
Peru, which is practically the head of navigation.

Balfour, at Khartoum, found that the steamers plying on the Nile were all
badly infested with mosquitoes, both Aédes calopus and Culex quinquefasciatus
breeding on them in abundance. Not only were these mosquitoes a source of
great annoyance to everyone on board, but by these steamers the towns along the
route were constantly restocked with mosquitoes.

“ For a long time it was difficult to control the breeding places on the steamers,
but in the autumn of 1904 the Director of Steamers and Boats issued more
stringent regulations to engineers and native reises, and the result was soon
apparent. Steamer after steamer arrived free from mosquito larve, Khartoum

North became a more comfortable place of habitation, and the wells in the river
zone of Khartoum were less frequently re-infected.”

The section of the Report of Working Party No. 1, Yellow Fever Institute,
Public Health and Marine-Hospital Service, which relates to the transportation
of mosquitoes by ships is of much interest, since it gives the result of actual ship
examinations at Vera Cruz and indicates how the insects are carried. It is
quoted in full:

“This subject was not studied in detail on account of lack of facilities, but
sufficient information was gathered to make it worth mentioning. The only
time we found mosquitoes actually breeding on board a vessel was in the instance
of the American schooner John H. Crandon. This schooner had arrived from
Mobile, Ala., with a cargo of lumber twenty days previous to our examina-
tion. Water and provisions had been taken on at Mobile. The examination
was made on account of a case of yellow fever occurring among the crew. The
wooden tanks were examined and found to contain larve of Stegomyia by thou-
sands. The iron water tanks were examined, but owing to their depth and small
MOSQUITOES ON BOARD SHIP 349

openings none were found. Iron water tanks, as a rule, are more securely
covered and are given more attention than the wooden containers. The two or
three barrels, placed in front of the galley and forecastle, are more frequently
infested and in every instance perference was given them in the examination.
The box of the carpenter’s grindstone offers another favorite place for the
breeding of this insect. An examination of the cabins was made to determine
the presence or absence of adult insects. In the room from which the man
with yellow fever was taken, the insects were found in abundance, both normal
and blood fed, resting in the shady corners on dark objects hanging around the
room. Considerable effort is necessary to detect mosquitoes when they are few in
number ; each cabin should be gone over systematically, passing the hands in the
corners and gently shaking the hanging articles until every object above the
floor has been gently disturbed. The forecastle and galley of this schooner,
immediately behind the breeding barrels, harbored the insect in abundance.

“The steamship William Cliff is of interest in connection with the trans-
ference of mosquitoes by vessels as well as furnishing data relative to the period
of incubation and spread of malaria among a crew where all outside influences
were removed.

“This vessel sailed from Liverpool, England, on May 29, 1902, with the fol-
lowing itinerary :

Arrived. Port. Sailed.
JUNC: Wess sccviccawe<as St. Thomasisicci0ncsaeees soa eeds June 12
SUNG: LO ec Petes Gewese e COLO Me sesh sonideesoerenace peaueaua aed dunes June 16
TUBS: 19). os secancarc nose aie os RATVESCOM: wceineccisce cee a ware ied wiaresd June 20
JUNE: 2553 scersemcatcatsinoear stares RAM DLCO: aijicsites -cicseies ceecdcdtesae sive eres June 26
JUNC 21 6: saseewanuiee s Vera: Crutinsics ssceaie casees sewaneces July 1

“ Until arrived in Tampico no sickness had occurred on board; while leaving
that port one man was taken sick with a vague chill, and illy defined pains. Two
days later, June 28, four of the crew were taken sick with pronounced chills,
pains in the head, extremities, and back, and high fever. The following day,
June 29, four more including the captain, were taken sick in like manner; on
June 30, two more were taken sick.

“On June 29, the blood of two of the cases was examined for the plasmodium
malaria with negative results. Their absence was accounted for by the large
doses of quinine administered prior to the examination. On July 1, two new
cases were examined; in one the tertian parasite was obtained, the other was
negative.

“The disease clinically was of the tertian type, about half-intermittent, the
balance remittant. All, with one exception, responded readily to quinine. The
exception resisted the quinine for three days. An examination of the ship was
made to determine the genera and species of mosquitoes on board. Of these
there were three genera and four species in abundance, as follows:

“Anopheles argyrotarsis, Culex fatigans, Culex tentorhynchus, Janthinosoma
Lutz.

“ All the varieties mentioned were found in the forecastle and after wheel-
house, the crew’s quarters being aft instead of forward. The cabins failed to
show the presence of mosquitoes on the examination of June 30, nor were any
noted previous to that time. ;

“ Anopheles argyrotarsis were present in Vera Cruz, though in very small
numbers; so scarce, that up to that time only one specimen had been taken.
This mosquito is also native to Tampico and Colon. According to the history
of the crew, which on such subjects is very unreliable, they stated that while at
Tampico they had not been molested by mosquitoes, while at Colon all hands
suffered severely from bites. The character of the fever is extremely suggestive
350 MOSQUITOES OF NORTH AMERICA

of a Colon infection, the tertian type being comparatively rare, both in Tampico
and Vera Cruz. Another point that makes Colon infection seem positive is the
period of incubation that invariably takes place after primary malarial infection.
This period has been variously stated to be from one day to several weeks. Our
own observations (Parker—report to Surgeon-General, October, 1901) on this
point are limited to a single observation that included three crews, one of a
steamship and two of schooners at Jacksonville, Fla., during the fall of 1901.
In this instance the three vessels arrived at Jacksonville from northern ports at
about the same time, and lay at a badly infected part of the town. Cases of
malaria appeared simultaneously on all three boats fourteen days after arrival.

“Dr. D. D. le Favre (Roussky Vratch, October 19, 1902), in an experiment
on himself, showed that the actual period of incubation of malaria in one in-
stance was twelve days.

“Those long periods of incubation in the malignant tertian and quotidian
aaa account for many infections that have been classed as being yellow

ever,

“Tt is a well-known fact, which one of us (Parker) has experienced, that
steamers lying in Habana Harbor become badly infested with mosquitoes, which
insects remain on board the steamship during the voyage to Progreso and thence
to Vera Cruz, appearing at night in the cabins in considerable numbers.

“Tt will be seen, then, that there is considerable evidence to support the
assertion that these insects are constantly being transferred from one locality
to another through the medium of ocean commerce. In this distribution the
iron ship, on account of its concealed water tanks, acts in the nature of a
mechanical host, while wooden vessels, on account of the loosely covered deck
containers, not only act as a mechanical host, but under favorable conditions, as
in calm or gentle weather, or lying at anchor, furnish the proper medium for
the propagation especially of domestic species.

“ Passed Assistant Surgeon Grubbs, U. 8. Public Health and Marine-Hospital
Service, has collected data at the Gulf Quarantine Station relative to the trans-
ference of mosquitoes by vessels. In a total of 82 vessels inspected to determine
the presence of these insects, he found Stegomyia fasciata in the adult stage on
three wooden vessels, all from Vera Cruz. One of the vessels was the John H.
Crandon mentioned above.”

Surgeon Grubbs’s paper above referred to (Bulletin No. 11, Yellow Fever
Institute) is interesting as giving the results of an effort to get exact information
on this point. It is quoted as follows:

“ At the present time, when evidence is pointing with more and more clear-
ness to the mosquito as the sole means of transmitting yellow fever, nothing is
of greater interest to the quarantine officer than to decide to what extent and
under what circumstances these infecting insects may be carried by vessels.

“This subject may be approached in three different ways: First, by observa-
tions on the length of time after leaving infected ports vessels may develop
yellow fever ; second, by experiments with mosquitoes under artificial conditions
made to simulate as much as possible those of nature; and third, by actual ob-
servation of vessels arriving from ports at the time infected or where the presence
of the Stegomyia fasciata render them liable to infection.

“ While it will require data obtained by all these means and extending over a
long period to arrive at any conclusions sufficiently accurate to allow them to
influence quarantine procedure, still I believe the last method of observation
cited will throw more light on the subject than the first two.

“Tt is for this reason that every vessel arriving at Gulf Quarantine Station
from Stegomyia-infected ports has, since the Ist of July last, been carefully ex-
MOSQUITOES AND VESSELS 351

variety, where and when they came aboard, and under what conditions.

Gulf Quarantine Station is an especially good point for these observations,
from the fact that it is 10 miles from the mainland, and because vessels bound
here do not pass near land, and so but rarely take on mosquitoes en route, and
even these, as will be seen, are always the marsh-bred varieties of Culea. Be-
sides, the examination of at least a thousand mosquitoes on Ship Island has
convinced me that there are no Stegomyia here.

“Each vessel inspected was carefully searched, the inspector being armed
with a cyanide killing bottle, and in addition the captain was asked the following
questions :

Le i Here any mosquitoes on board on your outward voyage, consisting
ays

“2. If so, did they come aboard before departure from home port or at sea,
and under what circumstances ?

“3. Were there any mosquitoes on board at your destination or on homeward
voyage ?

“4, If in port—

(a) How far were you from shore?
(b) Prevailing wind and weather?
“5. If on homeward voyage (consisting of
(a) Were they from port?
(b) re they come aboard at sea, on what day, and how far were you from
and!
(c) Were there wigglers in any of your tanks at any time?

“ During the five months from June 1 to November 1 observations were made
on 82 vessels, all arriving from ports where the Stegomyia is believed to exist
in quantities. Of these 78 were sailing vessels and 4 were steamers.

“Of these 82 vessels, 65 claimed to have had no mosquitoes aboard at any
time during the voyage or at port of departure, and their absence having been
confirmed by search, we can dismiss them from consideration and pass to the
remaining 17.

“ Five of these had mosquitoes on board at their ports of departure, 2 being
rid of them as soon as they were well at sea, while 3 others carried them two days
and were then no more troubled, except one schooner on which they reappeared
in quantities five days before she reached port, when she was 20 miles from shore.

“ Nine sailing vessels, having no mosquitoes on board before sailing, had them
appear at sea, in one case from the water casks in which the captain found larve.
But in the other cases they doubtless came from land which was at the time
distant—20 miles in one case, 15 miles in three cases, 10 miles in one case, and
2 miles in the last two instances. In all these vessels the mosquitoes found on
board on arrival at this station were the common varieties of Culex, there being
no Anopheles or Stegomyia among them.

“ Stegomyia fasciata were found on board and were identified in the remain-
ing three cases, as follows:

“The schooner Susie B. Dantzler arrived from Vera Cruz, Mexico, on July
16, 1902, after a voyage of fifteen days. The captain stated that mosquitoes
came aboard in large quantities at Vera Cruz, although he lay a half mile from
shore and there were variable winds with squalls and rain all the time. The
number of the insects decreased on the voyage but were always in evidence, and
we caught four or five of them here. No larve were found in any of the tanks,
and as the captain had repeatedly examined them without result in his efforts
to be rid of the mosquitoes, I believe the insects found on board here came all

the way from Vera Cruz.

amined to ascertain if mosquitoes were present on board, and, if present, their

of

 

 

days) —
302 MOSQUITOES OF NORTH AMERICA

“The schooner Hleanor arrived from Vera Cruz on July 17, 1902, thirteen
days out. She had no mosquitoes on board before reaching Vera Cruz, but there
quantities came on board. Her moorings were half a mile from shore and the
winds were variable. The captain stated that he could not get rid of the insects
after sailing, although the number decreased very much and there were no
larve in any of the tanks. At the time of her inspection here we caught and
identified a number of Stegomyia.

“The brigantine John H. Crandon arrived at the station July 27, 1902,
twenty-two days from Vera Cruz, where she had one case of yellow fever on
board. At that port she lay a half mile from the sea wall, three-eights of a mile
from an infected prison, and within 200 yards of an infected vessel. Stegomyia
fasciata were found on board by Acting Assistant Surgeon Hodgson before she
sailed, as well as larve in the tanks. All during the trip there were mosquitoes
in abundance, and a veritable plague of Stegomyia was found on board on her
arrival here. There was a constant buzz in the forecastle, and anyone entering
was sure to be attacked by several mosquitoes. Specimens were caught in almost
every protected part of the vessel, and all were found to be Stegomyia fasciata.
The captain had emptied several water barrels because he found they were breed-
ing mosquitoes, but the water remaining had no live larve, although many old
moults were seen. As breeding was surely going on in the tanks during a part
of the voyage at least, it would be impossible to say how long any particular
mosquito had been aboard or if any of them had been brought here from the
infected port.

“ Summary.—The above facts may be summed up as follows:

Vessels having no mosquitoes on board at any time............ 65
Vessels having mosquitoes on board in port of departure...... 5
Vessels on which mosquitoes (Culex) appeared en route....... 9
Vessels arriving with Stegomyia fasciata on board............ 3

“ Three and a half per cent, then, of all vessels brought Stegomyia on a voyage
averaging seventeen days.

“ Conclusions.—From but one season’s observations at a single quarantine
station we can not assume to draw any hard and fast conclusions regarding the
probability of Stegomyia, infected or not, being carried by vessels. Nevertheless,
I think we may conclude, first, that mosquitoes can come aboard vessels under
favorable conditions when the vessel is not over 15 miles from shore; second,
that Stegomyia can be carried from Mexican or West Indian ports to those of
our Gulf States; third, that they can board a vessel lying at anchor a half mile
or less from shore, being conveyed by the open lighters used or flying aboard, and
finally, that a vessel moored a short distance from land may become infected with
yellow fever, our old beliefs to the contrary notwithstanding.”

MOSQUITOES IN THE COURTS OF LAW.

So far as known to the writers, it has only been since the disease-bearing
function of mosquitoes has become rather generally accepted that these insects
have appeared in courts of law. Three rather interesting cases are mentioned
below, without any definite statements as to dates and other very exact details,
for the purpose of calling attention to an interesting phase of practical
entomology.

About 1900, in a southern town, there was a great deal of malaria and
especially among the operatives of certain large cotton mills, the motive power
of which was supplied by two large dams. The proprietors of the dams deemed
MOSQUITOES AND PROSECUTIONS 303

it possible that the trouble was caused by the pollution of the dam water by the
sewage of a State institution nearby, and complained to the health officer. It
seemed that the health officer was the attending physician at the State institu-
tion, and, resenting the implication concerning the sewage of the institution and
being familiar with the fact that mosquitoes carried malaria, he claimed that
the trouble was due to the breeding of Anopheles mosquitoes in the mill dams
or in the back waters caused by the dams. He therefore secured an order from
the State Board of Health, demanding the abolition of the dams in the interest
of health. This order was resisted by the proprietors of the mills and the case
was brought before the courts. The proprietors speedily informed themselves
on the subject of the etiology of malaria, reading all the latest publications on
the subject. They then cleaned up the margins of the dam, presented a copy of a
recently published book on mosquitoes to each of twelve physicians of the town,
and offered a reward of $50 each for every Anopheles larva that could be found
in the dams. The physicians all made search and no larve were found. Where-
upon, each physician was summoned as an expert witness in the trial. In the
meantime an expert entomologist was engaged to come to the town to examine
the conditions at the dams and to find the breeding-places of Anopheles in the
surrounding country. This expert found no Anopheles in the dams, but he
found the mosquitoes breeding practically everywhere throughout the com-
munity, with the exception of the dams. He found unused springs, chance pools
and puddles swarming with Anopheles larve. He often found them (since it
was at wet season) breeding in water standing in the furrows in the corn fields,
the soil being a strong clay.

At the first trial, expert testimony was brought forward to the effect that
the mosquitoes probably bred in the marshes at some distance back of the dams,
and that these marshes could not be drained so long as the dams remained. The
case was adjourned and before the time of the next court the proprietors of the
dams had bought certain portions of this back land and had successfully drained
it, showing that the existence of the marshes was not necessarily due to the ex-
istence of the dams. Ultimately, the case was nolle prosequt, and the dams re-
main today.

Another interesting case occurred in a town near Boston. A member of the
Board of Health, greatly interested in the subject of malaria and malaria mos-
quitoes, found Anopheles breeding extensively in certain stone quarries, particu-
larly in the abandoned portions of the quarries which had been worked. The
proprietors of the quarries were sued, with the idea of forcing them to fill up the
abandoned portions of the quarries, and the case came to trial in Boston before
atreferee. Expert testimony was heard and the judge finally announced, before
hearing all of the testimony which was prepared, that he had no doubt from
what he had already heard that the quarries were breeding malaria mosquitoes
and that their existence constituted a menace to the health of the people living
nearby ; but, that he would not decide in favor of the prosecution for the reason
that such a decision would constitute a dangerous precedent, and that it would
render all owners of excavations or mill dams or similar necessities to industry
354. MOSQUITOES OF NORTH AMERICA

liable to prosecution on what might be in some cases grounds that would be
trivial compared with the magnitude of the interests involved.

The third case occurred about 1903, in Texas. The plaintiff alleged that the
defendant, a certain railway, had constructed a large water tank or pool near
his premises, that the water in the tank became stagnant (caused by decaying
vegetation, etc.), producing poisonous vapors, gases, and disease-bearing germs,
which, escaping from said pool, reached and permeated the premises of the
plaintiff, causing foul odors and sickness. The evidence showed that since the
construction of the pool, mosquitoes were more numerous in plaintiffs home
than before. The railway surgeon testified that malaria was caused solely by mos-
quitoes, and that large bodies of water, such as the defendant’s pool, would not
produce as many mosquitoes as smaller and shallower bodies of water, and,
therefore, that the malaria of which the plaintiff complained was probably
derived from other sources than the railway water tank. Thus, the mosquito
aspect was only the collateral issue in the case, introduced curiously enough by
the defendant and not by the plaintiff. The trial was by jury and a verdict was
rendered for the plaintiff, largely owing to the submittal to the jury by the
judge of the issue of malarial poison caused by noxious and poisonous vapors.

PROTECTIVE AND REMEDIAL WORK AGAINST MOSQUITOES.

For many centuries humanity has endured the annoyance of mosquitoes with-
out making an intelligent effort to prevent the annoyance, except for smudges,
preparations applied to the skin, and removal from localities of abundance. And
it is only within comparatively recent years that wide-spread community work
against mosquitoes has been undertaken, this having resulted almost directly
from the discoveries concerning the carriage of disease by these insects.

As obvious a procedure as it might seem to be, the abolition of mosquito
breeding-places is a comparatively new idea. The treatment of breeding-places
with oil to destroy the larval forms is, however, by no means recent. As early
as 1812, the writer of a work published in London entitled “ Omniana or Horae
Otiosiores ” suggested that by pouring oil upon water the number of mosquitoes
may be diminished. It is stated that in the middle of the 19th century kerosene
was used in France in this way, while in the French quarter in New Orleans oil
was placed in water tanks before the Civil War, the idea having possibly come
from France to New Orleans or vice versa.

Another early recommendation of the use of oil was given by an anonymous
writer in the Magazin Pittoresque, vol. 15, pp. 178-182 (1846) in an article
on the “ Mosquito and Its Metamorphoses.” The phraseology translated into
English is as follows: “When one has recognized that the ponds or ditches
existing close to houses are swarming with the larve of mosquitoes, one can
immediately destroy this dangerous race by spreading on the surface a little oil,
which extends in a very thin film and prevents the little insects from coming
up to breathe. This proceeding is especially easy to put into practice upon the
irrigating tanks in gardens, since it is in such places that the greatest number
of mosquitoes develop.”
EARLY CONTROL WORK 395

Again, quite recently, Mr. John P. Fort, of Athens, Georgia, has written to
one of us (Howard) that about the year 1854 his father, Dr. Thomlinson Fort,
was physician to the penitentiary at Milledgeville, Ga., a place of about two
thousand people; this had become infested with mosquitoes so as to cause much
complaint. Dr. Fort had the matter investigated, and it was found that the
mosquitoes originated in the tan-vats of a tan-yard in the penitentiary, and in a
large cistern attached to the livery stable in the city. He ordered oil to be put
upon the water in the tan-vats, and the mosquitoes were destroyed.

In 1892, some exact experimentation was undertaken by Howard, in Green
County, New York, which indicated the amount of kerosene necessary for a given
water surface, and the duration of efficiency. These experiments also showed
that adult mosquitoes are captured by the kerosene film; that is to say, adult
females alighting on the surface of the water for the purpose of depositing eggs,
or for drinking, are destroyed by the kerosene before the eggs are laid. The
account of these experiments, published in “ Insect Life,” vol. 5, No. 1, pp. 12-14
(September, 1892), attracted much attention among persons interested and re-
ceived extended newspaper notices. From this it resulted that practical work on
a larger or smaller seale was carried on with success, by H. E. Weed, at the
Mississippi Agricultural College; by Dr. John B. Smith, on Long Island; by
Prof. V. L. Kellogg on the campus of the Stanford University of California;
by Rev. John D. Long, at Oak Island Beach, Long Island Sound; Mr. W. R.
Hopson, near Stratford, Conn.; Mr. R. M. Reese, in Baltimore; Mr. W. C. Kerr,
on Staten Island; M. J. Wightman, at an Atlantic coast resort, and by Dr. St.
George Gray, in the British West Indies. The publication of the extensive
mosquito article in the bulletin on house-hold insects (No. 4, n. s., Division of
Entomology, U. S. Department of Agriculture, 1896) by Howard and Marlatt,
intensified this interest, and was productive of other successful work.

With the discovery of the disease-bearing relation of mosquitoes, first with
malaria and next the yellow fever, public interest in their destruction became in-
tensified, and large-scale remedy work was done at many points. Bulletin No.
25, n. s., Division of Entomology, U. S. Department of Agriculture (1900), by
Howard, devoted considerable space to the subject of remedies, and indicated
in the main those remedies which are of use today and are to be recommended
upon a sound basis of practical experimentation. It is probably unfortunate
that the writer of this bulletin laid so much stress upon the use of petroleum as
to obscure in a way the much more vital measures of thorough drainage and the
complete abolition of breeding-places; but the idea that was prominent in his
mind at the time the bulletin was written was “ Let us stop mosquito breeding
at once in an economical way, and then let us take our time in more expensive,
more elaborate, and more radical measures.” The same criticism can be made
and the same partial, though by no means satisfactory, explanation urged in the
case of Howard’s book “ Mosquitoes,” published in the spring of 1901; but both
bulletin and book served a good purpose, and together undoubtedly helped to
start, to a great measure, the anti-mosquito work which has since been carried on

in the United States.
24
356 MOSQUITOES OF NORTH AMERICA

Practically beginning with 1901, there has been a rather rapid increase in
anti-mosquito work by individuals and communities, but this work has not
progressed with anything like the rapidity demanded by the distressing con-
ditions of many localities and in fact of great areas. Yet, it is probably accurate
to state that more intelligent work of this kind has been done in the United
States than in any other country. This is probably due to the greater prevalence
of mosquitoes in the United States than in any other highly civilized country,
but the well-known practical character of the American people is also an element.

During the summer of 1900, Mr. W. J. Matheson carried on some admirable
anti-mosquito work at his large place at Lloyd’s Neck, Long Island. This work
was most thoroughly done and was most successful, no mosquitoes breeding in
localities where they had previously swarmed to such an extent as to render them
almost uninhabitable. In the autumn of 1900, there was a migration of salt-
marsh mosquitoes to Lloyd’s Neck from salt marshes bordering on Center Island.
Mr. Matheson induced the practical owners of Center Island to take up extensive
work during the summer of 1901, and this work was carried through in a very
perfect manner by Mr. H. C. Weeks, engineer in charge, and was described in the
“ Century Magazine ” for July, 1902. In the summer of 1901 was also begun
by far the largest piece of work as yet undertaken. It originated on the northern
shore of Long Island in the regions between Hempstead Harbor and Cold Spring
Harbor, and was carried on under the auspicies of the North Shore Improvement
Association, a group of wealthy and prominent residents of this part of the
Island. The work during the summer of 1901 included an almost microscopic
survey of the region and the preparation of a map showing the breeding-places
of the several kinds of mosquitoes. It included also the preparation of reports
by entomological experts, a report by Professor Shaler, of Harvard University,
on marsh areas and related subjects; an account of the work done on Center
Island during 1901; and engineering reports, including recommendations for
treatment, by Mr. H. C. Weeks. A volume was published in the spring of 1902
entitled “ Reports on Mosquitoes, with Map” (New York, Press of Styles and
Cash), which will form a very sound basis for thorough ocean-shore community
work for some time to come. Following the survey of the work by the North
Shore Improvement Association, in 1901, there were carried on by private in-
dividuals and by the Association, in 1902, certain remedial and preventive opera-
tions. One of the most interesting of this series was performed on the estate of
Mr. W. D. Guthrie. By means of a dyke and a sluice gate a large marsh area
was drained out, and the breeding of the salt-marsh mosquitoes was stopped.
A stretch of 75 acres of land was reclaimed, the soil was disintegrated and
properly treated, with the result that cabbages, turnips, and celery were grown
at the close of the summer of 1902.

The year of 1902 was also marked by the first effort to secure anti-mosquito
legislation from one of the United States. The State Entomologist of New
Jersey, Doctor John B, Smith, backed by an intelligent public sentiment, tried
to secure the passage of a bill by the State Legislature during the winter of
1901-2, appropriating ten thousand dollars for the purpose of investigating
PUBLICATION 159

1. School children finding mosquito breeding-places, Worcester, Mass.

2. Mosquito class-work, Worcester, Mass.

PLATE XIV

 
COMMUNITY WORK 357

the possibilities of the wholesale destruction of the salt-marsh mosquito and
other kinds of mosquitoes. The bill passed one branch of the Legislature, but
failed in the other branch. The Governor of the State, however, was able in
other ways to provide Doctor Smith with a limited sum to carry on researches.
In this work he discovered a number of most interesting and vitally important
facts concerning breeding habits of the salt-marsh mosquitoes, indicating that
the breeding-places of this species are more or less circumscribed, and that the
matter of control is by no means as expensive as would appear at first sight, and
it was these discoveries that eventually led to the passage of the law which will
be mentioned later.

Admirable community work was taken up during 1901-2 by other New
Jersey towns, notably South Orange, Elizabeth, Montclair, Monmouth Beach,
and Summit. Independent work was begun in greater New York, under Doctor
Lederle, and mapping mosquito breeding-places within city limits was begun.
Independently, the health officers of Brooklyn, Jamaica, and Bronx Borough
began efficient work, while the summer resorts of Arverne and Woodmere re-
duced the mosquito supply by intelligent operations. At Willets Point intelli-
gent and efficient work was carried out on a small scale. In Massachusetts in-
teresting and important work was done at Brookline and at Worcester. In
Brookline, the Board of Health first considered the work in August, 1901, and
in September all the breeding-places of the malaria mosquito and of the other
mosquitoes were treated. In 1902, all pools, ponds, ditches, and other breeding-
places, including catch-basins, were located on the town map. The approximate
areas were determined and the number of catch-basins ascertained. Breeding-
places of Culex and Anopheles, respectively, were determined, and also the places
where both kinds were breeding—this being done in order to ascertain the proper
intervals for treatment; that is, whether every two weeks or every three weeks.
Public dumps and other places where accidental receptacles of water might be
found were also located on the maps. Light fuel oil was used on all breeding-
places. The public dumps proved to be very important in the work, since many
accidental receptacles, like bottles, cans, wooden and tin boxes, and the like, were
found to contain larva. Where these were breakable, they were simply broken;
when not, they were carried and dumped into pools to assist in filling these.

This Brookline work was so thorough that the community was greatly relieved
from the mosquito pest, although in the autumn some low meadows near the
town, where drainage work had been postponed, were found to be breeding mos-
quitoes in great numbers.

At Worcester, the work was of the most interesting kind. Dr. William Mc-
Kibben and Dr. C. F. Hodge started the crusade. Breeding-places were mapped
and photographed and public lectures were given. The school children of the
several grades were interested and were organized into searching parties. Many
breeding-places were filled up and others were treated with kerosene. A strong
point was made in Worcester, by those engaged in the crusade, of the prevalence
of malaria in many places in the city. The relation between the mosquito breed-
ing-places and the houses where there were malaria patients was effectively
358 MOSQUITOES OF NORTH AMERICA

pointed out, a map was prepared showing the exact distribution of malaria
in the city, and photographs were made showing the character of the breeding-
places of the malaria mosquito. It is probable that these Worcester efforts to
interest the school children were the first made in this direction, although the
idea was carried out to a much greater extent later in San Antonio, Texas, under
Doctor Lankford, as will be pointed out on subsequent pages. Other work,
during the summer, was carried on at Pine Orchard and Ansonia, Connecticut ;
at Old Orchard Beach, in Maine; and on the campus of the Michigan Agri-
cultural College, in Michigan. Strong efforts were made during the summer
to start work at Baltimore, but for a time the City Council refused to make
appropriations. At Atlanta, Ga., the Sanitary Department used a large amount
of kerosene in the stagnant pools and swampy places around the city, and warned
the citizens to watch their rain barrels and keep their gutters open. A great
many pools of water were drained, and in the negro quarters of the city the
sanitary inspectors were constantly on the lookout for standing water in buckets
and other chance receptacles. The matter was taken up with the County Com-
missioners and the area of preventive measures was extended toward the close
of the season. In Savannah some work was done and the number of mosquitoes
reduced very considerably. Oil was used diligently by the sewer-cleaning forces
and was placed in the catch-basins. So great was the relief that many people in
Savannah for the first time used no mosquito-bars. At Talladega, Alabama,
under the direction of Doctor B. B. Simms, anti-mosquito work was commenced
early in the season and was carried out systematically and thoroughly. No place
that could possibly prove a breeding-place was overlooked. The application of
kerosene was repeated several times during the year. St. Louis took up the work
early in July, and the Municipal Assembly made an appropriation for supplies.
The Health Department, however, was hampered for lack of men and little
work was done.

Such were the early steps in the mosquito crusade in this country. Many other
communities have taken up the work since 1902. Some, through inefficient
work, have allowed their efforts to lapse, and have become more or less indiffer-
ent. Others have gone ahead and have spent considerable sums of money in
their mosquito fight.

In the early days of mosquito warfare there was great indifference combined
with incredulity as to the danger from mosquitoes, even among the medical
profession, and particularly in the South. This indifference and incredulity,
however, have now, for the most part, passed away. Boards of health very
generally appreciate the desirability of anti-mosquito work, and as rapidly as
town councils can be induced to appropriate the necessary funds, the work is
going ahead.

Excellent anti-mosquito work, backed by rather modest funds, has been
carried on during the past few years in Honolulu, under the direction of the then
Entomologist of the Hawaiian Agricultural Experiment Station, Doctor D. L.
Van Dine. In Porto Rico some work is being done, as well as in the Philippines,
under the United States government. In Cuba and in Panama the work has
SCREENING OF HOUSES 359

been of a standard character, and the operations at these points will be more
fully mentioned in subsequent paragraphs.

In other parts of the world many striking examples of value of anti-mosquito
work have been shown comparatively recently, and several of these will be de-
tailed later.

In the pages that follow the aim has been to give a full consideration to the
subject of remedies and preventives, discussing not only those which have been
found to be of the greatest value, but also others of lesser or even no value, since
an expression of opinion concerning all may well be considered desirable. A
large part of the following information has been published by the senior author
under the title “ Preventive and Remedial Work Against Mosquitoes ” as Bull.
88, U. S. Dept. Agr., Bur. Ent., 1910. For a condensed summary of the best
remedies the reader is referred to Farmers’ Bulletin 444 of the U. S. Depart-
ment of Agriculture, which may be had for the asking.

PROTECTION FROM BITES.
SCREENS AND CANOPIES.

Such obvious measures as the screening of houses, the use of netting for beds
and the wearing of veils and gloves after nightfall in badly infested regions,
need no consideration in detail. But even in such an apparently simple matter
as house screening certain points must be taken into consideration. It may
be incidentally stated that with proper treatment of breeding-places screening
is unnecessary. The expense to which the people of the United States go for
screens against mosquitoes and flies is enormous, and has been estimated at
$10,000,000 annually.

In screening a house, as Doctor John B. Smith has pointed out in his Bulletin
No. 216 of the New Jersey Agricultural Experiment Station, the attempts fre-
quently fall far short of protection:

“ Adjustable, folding, or sliding screens are never tight, and when the insects
really want to get indoors they work their way patiently between the two parts
of the screen or between its frames and the window. But even a well-fitted
screen either sets tightly into the frame or, running like a sash, may offer leaks
when a window is only partly opened. . . . There is abundant opportunity for
the insect to get in between the net and lower cross bar; in fact, there is no real
protection at all. Where the netting is fixed to the outside of its frame, so that
there is no space between it and the lower part of the sash, the insects neverthe-
less find their way in between the window sashes. . . . It has been already said
that the mosquitoes will, in certain seasons, attempt to make their way through
the screens, and they have less trouble with wire netting than with any other
because the meshes are even in size and the strands smooth. Some of the fabrics
used for nettings, especially of the cheaper grades, have the threads so fuzzy that
it is simply impossible for the mosquitoes to make their way through, and they
rarely even try it except where there is a tear, or where the threads have been
spread apart leaving an unusually large opening. Where an onslaught is made
on wire netting it can be checked by painting lightly with kerosene or oil of
citronella. I have tried both and found them successful.”

In addition to these mechanical difficulties it often happens that the cellar
and attie windows of houses are not screened. This is a great mistake, since
360 MOSQUITOES OF NORTH AMERICA

mosquitoes will enter these windows and pass the winter in both cellars and
attics. They also descend unused chimneys, so that fire-places require screening.

With regard to bed canopies there is reason for the greatest care. There
should be ample material to admit of a perfect folding of the canopy under the
mattress, and the greatest care should be taken to keep the fabric well mended.
It often happens in mosquito regions that little care is taken of the bed nettings
in the poorer hotels, and it is necessary for perfect protection that a traveler in
the Southern States should carry with him a pocket housewife and should care-
fully examine his bed netting every night, prepared to mend all tears and
expanded meshes.

Veils and nettings for camping in the tropics are absolute necessaries. Light
frames are made to fit helmet-like over the head and are covered with mosquito
netting. Similar frames readily folded into a compact form are made to form
a bed covering at night, and every camping outfit for work in tropical or
malarial regions should possess such framework and plenty of mosquito netting
as an essential part of the outfit.

An illustrated advertisement in Ross’s “ Mosquito Brigades ” shows a folding
hood mosquito net especially for the use of travelers when taking rest. This is
64 feet long, 4 feet wide, and 2 feet high. It is a frame arrangement which can
be opened by the traveler so as to envelop himself when he is lying down. The
frame is easily carried in the hand, being only 40 inches long by 4 inches in diam-
eter when folded. There is also given an illustration of a small, compact mos-
quito house for use by travelers while writing, reading, or taking their meals. It
is large enough to contain two persons seated, and is constructed with a frame
which is earily portable. The frames are manufactured by White & Wright,
surgical instrument makers, 93 Renshaw Street, Liverpool. No doubt other
apparatus of the same kind is manufactured and to be purchased at large out-
fitting establishments, such as the Army and Navy Stores in London.

Some attention has been paid to the subject of the size of the mesh of screens
with especial reference to the yellow-fever mosquito. Working Party No. 2 of
the Public Health and Marine-Hospital Service, at Vera Cruz, conducted a few
experiments to determine the question of the size of the mesh. Their experi-
ments were conducted by placing screens with a varying number of meshes to
the inch over breeding-jars and putting bananas, syrup and other food on the
other side so as to tempt the hungry mosquitoes to pass through. The fruit
and other food was placed in a jar which was inverted over the mosquito breed-
ing-jar, and a piece of gauze or netting was inserted between the two jars so
that the mosquitoes would have to pass through the meshes in order to appear
in the upper jar. As a result it was found that both males and females passed
through a netting containing sixteen strands or fifteen meshes to the inch, but
could not pass twenty strands or nineteen meshes to the inch. It therefore be-
came evident to these observers that the large-meshed mosquito bars ordinarily
used in Vera Cruz would not offer proper protection and that window screening
must also be of a finer mesh than is sometimes employed.
SIZE OF MESH 361

Goeldi refers to this screen question, both in regard to the yellow-fever mos-
quito and to the common rainwater-barrel mosquito, in connection with some
very interesting observations about the range of variation in the size of the
individuals of the same species, a fact which is frequently noticed with other
insects but to which special attention has not been called elsewhere with
mosquitoes.

“Frequently I have observed, both in Stegomyia fasciata and in Culex fati-
gans, alongside of individuals of normal stature, individuals very much smaller
—veritable dwarfs. This observation may be made on specimens captured in
freedom as well as on those in captivity, in this last case the phenomenon re-
peating itself rather frequently. There are sometimes born individuals, both
males and females, so small that they easily pass through the mesh of wire
gauze much closer than the mesh of ‘ Grassi’s gauze’ which today is produced
on a large scale in Italy with a view to the prophylaxis against Anopheles and
malaria (Grassi, himself, recommends a gauze that shall not have less than nine
meshes in 14 centimeters of distance, which corresponds to little linear squares
1.7 mm. to theside). The government of the State of Para imported from Italy,
for my experiments, a gauze under this name which had but six threads to 14
centimeters of linear extension, corresponding to squares of 24 mm. along one
side. I refer particularly to this last brand, which I consider sufficient as a rule,
for application to hospitals, to impede the invasion of mosquitoes from outside,
but which I found, nevertheless, insufficient for the walls of my cages destined
for experiments on mosquitoes like Stegomyia fasciata and Culex fatigans in
captivity.

“Tn general, the phenomena of macrosomia and microsomia in plants and
animals are related directly with greater or less abundant nutrition, and I do
not believe that the quoted dwarf race of Stegomyia and Culex is to be explained
in any other way than by a sparse alimentation and a delayed development in
the larval stage. On this point I have at hand experiments in proof: Larve
bred in clear water—that is to say, relatively poor in assimilable substances—
gave me imagos of small stature. Furthermore, it is yet to be shown that I am
deceived in my opinion that the frequency of dwarf individuals captured in
freedom is not notably greater at certain periods, assuming almost the character
of arule. Thus this year, in the last weeks of October and in November, before
we entered fully upon the rainy season, I got the impression that the females
of dwarf dimensions were particularly numerous. I doubt that this is the work
of a mere accident: it is very possible that the frequency of dwarf individuals,
normally possible during the whole year, may be periodic and represent a case,
somewhat diminished, of what is called in entomology ‘ dimorphism of seasons.’
Theoretically there can be no serious obstacle in accepting the argument that in
the height of the dry season, with the growing lack of water, the conditions of
life for the larvee become more difficult, thus favoring the generation of mos-
quitoes below the normal dimensions. Impoverished water and reduced food
may really, as we have seen above, oblige the larva to take two or three times
the period normally necessary for its development and to acquire the necessary
growth for its metamorphosis. I have the feeling that hibernation, in the sense
in which this word is accepted in zoologic literature, may well for the tropical
and equatorial Culicide find its expression in two ways: (1) Delayed develop-
ment of the larve; (2) Dwarfed stature of the imagos.”

Note by Translator—Doctor Goeldi enters into a long explanation as to hiberna-
tion, evidently for the benefit of equatorial readers who might accuse him of the mal-
use of technical terms. He refers to the phenomenon of “seasonal lethargy” and
endeavors to trace a connection between the circumstances favoring the development
of the perfect insects in parallelism with the “ periodicity of yellow fever.” His final
paragraph is as follows:
362 MOSQUITOES OF NORTH AMERICA

“Tt would be a mistake to believe that these dwarf individuals of Stegomyia
are less aggressive and sanguinary than those of normal stature. They behave
in a precisely similar manner ; their bites are not less painful, as I have had fre-
quent occasion to prove.”

A study of the question of mosquito bars or canopies, both for indoors and
out-of-doors, has been made by Dr. F. Arnold, the District Medical Officer of
Health, Northern Transvaal, and he has published an interesting article on the
subject in The Transvaal Agricultural Journal for October, 1907, pages 13-15.
He illustrates the mesh of different nettings purchased in Pretoria, labeling a
netting with a mesh 1 mm. in width as good, one of 2 mm. as doubtful, and one
of 3mm. as bad. These nettings were tested by stretching them over the mouths
of three large pill-boxes, and in each pill-box was put a known number of live,
uninjured mosquitoes. The boxes were placed on a chair alongside his bed,
where they remained all night, with the idea that by placing the mosquitoes
near a sleeper they would be anxious to get at him, and the natural conditions
existing in a bedroom would be imitated; that is, there would be a mosquito
and a sleeper separated by a net. The conclusions coincided with those above
indicated. Doctor Arnold continues his directions in the following words:

“In this country the bell-shaped bedroom mosquito net is almost always
used ; box-shaped nets are rarely seen. In Eastern countries the box-shaped net
is generally used fixed on to a large four-posted bed; such an arrangement has
the great advantage that the net can be drawn tight and there is within it so
large a space for the sleeper that his limbs, if uncovered, are not likely to come
in contact with the net.

“ Frequently the bell net has too small a ring at the top and the netting is not
sewn on to the calico which closes the ring, but is gathered-up above it by a
running thread ; such an arrangement causes folds to be formed in the net above
the ring and through the grooves of these folds mosquitoes enter freely. Again,
the net is often allowed to hang loose on the bed or it is drawn over the whole
bedstead on to the ground. When hanging loose it affords very little protection,
for it will, during the night, certainly come in contact with the face, arms, etc.,
which will be bitten through the net. If placed right over the bedstead then its
lower margin must be heavily-weighted with a long and continuous sand bag,
and every care must be taken to drive away mosquitoes which may be sleeping
on the dark under side of the mattress; in out-lying districts white ants would,
in one night, make short work of net and sand bag if lying on a mud floor.
How, then, should a net be made and arranged ?

“ Proceed as follows: Obtain a ring of wood or iron, in diameter two and a
half to three feet ; close it with a piece of stout calico; on this calico, around the
circumference of the ring, sew the mosquito net very carefully, using netting
of the mesh shown as No. 1. Suspend the net to the ceiling in the usual way.
Next arrange the bedding as is done on board ship; that is to say, take the
upper sheet, blanket and counterpane and fold the margins inwards at the sides
and at the foot; all the bedding which will cover the sleeper will then lie on
the top of the under sheet. Now tuck the mosquito net under the mattress all
round, drawing it tight. On going to bed draw out the net at one side, creep
in under it, and carefully tuck it back under the mattress. The sleeper is now
in a cage; it does not matter how much he kicks about the net will remain true,
and, provided that a fair-sized bed is used, there is not much risk of an unclothed
part of the body touching the net. For use on the veld many kinds of stretchers,
etc., have been devised. The writer has used a folding stretcher which carries
SIZE OF MESH 363

four thin upright rods. Through eyes in the upper ends of these rods runs a
cord, and over the whole structure is placed a box-shaped net. The net sold
with the stretcher has its lower margin weighted ; it is intended that this lower
margin should lie on the ground. But this is a theoretical arrangement. First,
one rarely gets a flat piece of ground free of grass and stones whereon to place
the stretcher ; secondly, a sudden gust of wind causes the hanging net to ‘ ride-
up’ on the feet of the stretcher; and, lastly, a stone or grass lifts up the lower
margin of the net.

“The net, etc., should be arranged as follows:—Take a large, long blanket,
? ft. x 5 ft., fold it lengthways, and lay it on the stretcher to serve as a mattress.
Arrange the blankets which will cover you just as the top-bedding is arranged
for an in-door bed. Tuck in the net carefully all round under the blanket-
mattress, taking especial care to cross the folds of the net round the upright rods.
Crawl in under the net and close it in the usual way. The stretcher used by the
writer, when opened for use, measures six and a half by two and a half feet, and
stands fifteen inches above the ground. The whole outfit (stretcher, rods and
net) weighs 26 lbs. and can be packed into a canvas sack measuring three feet
by thirteen inches.”

The Medical Department, of the U. 8. Army, is now advising the Quarter-
master-General’s Department that, in the belief of the experts of the Office of
the Surgeon-General, screens with 16 meshes to the inch will exclude the yellow-
fever mosquito and the malarial mosquitoes. Col. J. R. Kean has given us
this information, and states that this opinion is based upon some very careful
experiments made by Doctor Juan Guiteras in 1908. Colonel Kean writes
further that Dr. Charles F. Craig, of the Medical Corps, U. S. Army, reports
that a 16-mesh to the inch gauze was always successful in excluding Anopheles
mosquitoes in the Philippines, and he was stationed at Camp Stotsenburg where
these mosquitoes were exceedingly abundant. Since it is known that certain of
the anopheline mosquitoes of the Philippines are smaller than species found
in the United States, the Surgeon-General of the Army has directed that the
Board for the study of Tropical Diseases investigate the question further.
Doctor Guiteras’s report to Colonel Kean has been sent to us, and we print it
as follows:

“The bronzed wire gauze of 16 threads to the inch that was sent to me by you
for trial as to its efficiency in barring the passage of stegomyia mosquitoes, has
been subjected to a series of experiments in our laboratory at Las Animas
Hospital.

“T should state that we had heretofore acted under the impression that an
18 wire mesh was required ; that we had never employed in this hospital any but
the 18 wire mesh, and that this opinion was in part based on experiments that
had been made by Dr. Rosenau of the Public Health and Marine-Hospital
Service. I do not think, however, that Dr. Rosenau gave his experiments as

conclusive.

“The following equipment was used for our experiments :

“ A large cage or wooden frame, closed in with wire gauze made of 18 threads
tothe inch. The cage had a double door, and measured 2.10 meters long by 1.50
meters wide, and 1.93 meters high.

“ An ordinary wooden tub measuring 0.40 meters in diameter, and covered
with bronzed wire gauze of 16 threads to the inch.

“ A small cage measuring 0.54 meters by 0.26 meters by 0.34 meters, con-
sisting of a frame covered with wire gauze of 18 threads to the inch. This long
364 MOSQUITOES OF NORTH AMERICA

cage was divided across by a double partition consisting of 2 pieces of 16 mesh
gauze separated by a space 2 centimeters wide. Each compartment was pro-
vided with an opening for the hand.

“ The experiments were made exclusively with the stegomyia mosquito. They
were commenced on the Ist of June of this year.

“On the 1st of June, 100 stegomyias, male and female, were let loose in the
large cage where they found dry food (sugar), but no water. In the cage was
placed the tub, three-quarters filled with rain water, and closed with 16 mesh
gauze. After six days all the mosquitoes in the cage had perished, evidently for
want of water. No mosquitoes had passed the 16 mesh gauze. No eggs were
found in the water, and no larve developed there.

“On July 4th, 200 stegomyia mosquitoes, male and female, were let loose in
the same cage. On the 9th there were only two insects left alive. On the 10th
these two were dead. No mosquitoes, eggs or larve were found within the tub
or in the water. This experiment was, in every respect, a repetition of the first.

“Tn the small cage the experiment was four times tried of placing three
unfecundated females on one side, and three males on the other. Both groups
were provided with food and water, and the females were occasionally allowed
to bite. These females had been obtained from pup that had been kept iso-
lated, each one in separate bottles, so that all possible contact with the male
could be excluded. The double partition in the cage prevented the possibility
of contact through the partition. The males and females never passed through
the partition and the females were not fecundated.

“The experiment was also repeatedly tried of keeping males and females
together on one side of the partition, and food and water on the other side.
Banana, sugar, molasses were tried separately. At times also the hand was kept
in the empty compartment for periods of from 30 to 40 minutes. If no water
was allowed on the side occupied by the mosquitoes they promptly died. Other-
wise they endured long, but were never able to pass across, nor could we ever
see any evidences that they made any attempt to push themselves across.

“ Another series of experiments were made by darkening one side of the cage
with a dark cloth. The mosquitoes were placed sometimes on the dark side, and
sometimes on the uncovered or light side. These insects were allowed food and
water during the experiment. They never passed through the partition.

“It is my opinion that we may conclude from these experiments that the
stegomyia calopus can not pass through the wire gauze sent for trial. The gauze
is a 16 wire mesh; that is, it presents 16 wires or threads to the linear inch.”

Dr. Samuel T. Darling, Chief of Laboratory of the Board of Health, Depart-
ment of Sanitation, Isthmian Canal Commission, in a paper entitled “ Studies
in Relation to Malaria,” Washington, Government Printing Office, 1910, gives
the results of certain observations upon the size of mesh of wire screen. He finds
that at the Isthmus a 16-mesh screening answers the purpose against malarial
mosquitoes, but that against the yellow-fever mosquito, while practically safe,
it is not absolutely so. Out of several hundred mosquitoes, 8 species were able
to make their escape through a 16-mesh screen, as follows:

 

; Bamber of

Stegomyia calopus: “beaaped.,
IML OB: heitee diacchitisdes a cciaaparelatecd. eit veces aibon vee wianerahe adeno eetees 10
POM AI ES! z. 5 sci: voce: aise wees <geaita wp aietione seacaianas Ea ieee eae 6
Culew cubensis, Male. ..... ccc cece eee veneer seceneenee sae
Oulen rejector, Male. iodc4 sons cx UawW se NOR 4s sXe oa aS 5-8 BES 1
Oulex extricator, female. ....... cc cece eee cere eee eeteeees 1
Aedes angustivittatus, female... .. cc cece ccc e cece eee eeeenes 1

Uranotenia lowti, female... .. 6... ccc ee eee eee eeeeees 1”
PROTECTIVE LIQUIDS 365

SCREENING BREEDING-PLACES.

What we have said in regard to the size of mesh to be used in window screens
and canopies applies equally well to screens over possible breeding-places to
prevent the breeding of mosquitoes or the issuing of mosquitoes which have bred
therein. In cities like those in the Gulf States, where the rain-water supply is
conserved in large tanks, screening is necessary and is now enforced, Galveston
and New Orleans perhaps being the first to make this an important health
measure. But rain-water barrels everywhere must also be screened in the same
way, except where fish are used to kill the early stages of mosquitoes. In out-
of-the-way places, however, where it is difficult to get good screens or where the
expense of screening is seriously to be considered, a cheap cover may be made
for well-mouths or water barrels, such as described by Dutton in his Report of
the Malaria Expedition to the Gambia and which he states was devised by
Doctor Forde.

“This cover consists of a large iron hoop obtained from discarded barrels,
to which is fastened all round a piece of stout calico or sacking free from holes,
in such a manner that a good deal of sag is left in the material. After water is
obtained from the well the hoop is thrown over the mouth, and the calico
catching on the rim of the well completely closes the entrance and is kept taut
by the weight of the iron hoop. This cover is so simple, and, however carelessly
applied, must so effectually close the entrance of the tub against mosquitoes,
that I think it is well worthy of extensive use in the town. Dr. Forde has lately
informed me that these covers are now being made in Bathurst, and are sold to
the natives for the sum of four pence.”

PROTECTIVE LIQUIDS.

A number of different substances have been in use to rub upon the skin or to
put near the bed as a protection from mosquitoes. Spirits of camphor rubbed
upon the face and hands, or a few drops on the pillow at night will keep away
mosquitoes for a time, and this is also a well-known property of oil of penny-
royal. The use of oil of peppermint, lemon juice and vinegar have all been
recommended for use as protectors against mosquitoes, while oil of tar has also
been used in bad mosquito localities. A mixture recommended by Mr. E. H.
Gane, of New York, is:

Castor oil 1 oz.
Alcohol 1 oz.
Oil of lavender 1 oz.

The oil of citronella has come into very general use in the United States in
the past few years. The odor is objectionable to some people but not to many
and it is efficacious in keeping away mosquitoes for several hours. A mixture
recommended by Mr. C. A. Nash, of New York, composed of

1 oz. oil of citronella

1 oz. spirits of camphor

4 oz. oil of cedar
has been the most efficacious mixture tried by the writer. Ordinarily a few
drops on a bath towel hung over the head of the bed will keep Culex pipiens
away for a whole night. Where mosquitoes are very persistent, however, a few
366 MOSQUITOES OF NORTH AMERICA

drops rubbed on the face and hands will suffice. This mixture in the experience
of the writer has been efficacious against all mosquitoes except Aédes calopus,
the yellow-fever mosquito. This mosquito begins to trouble the sleeper at day-
break and by that time the efficacy of the mixture has largely passed, and one
is apt to be in his soundest sleep. If, however, one could arrange to be awakened
just before day-break and apply the mixture, returning for the last nap, it is
probable that it would be efficacious.

Fishermen and hunters in the north woods will find that a good mixture
against mosquitoes and black flies can be made as follows:

Take 24 lbs. of mutton tallow and strain it.

While still hot add: 4 lb. black tar (Canadian tar).

Stir thoroughly and pour into the receptacle in which it is to be contained.
When nearly cool stir in 8 oz. of oil of citronella and 14 02. of pennyroyal.

Oscar Samostz, of Austin, Tex., recommends the following formula:
1 oz. oil citronella.
4 oz. liquid vaseline.

Apply freely to exposed parts.

Mr. B. A. Reynolds, of the Bureau of Entomology, has used successfully in
New Orleans 20 minims of oil of citronella to the ounce of vaseline or lanoline,
preference being given to the latter.

Doctor Durham, of the English Yellow Fever Commission to Pard, Brazil,
told the writer that he and the late Doctor Myers found that a 5 per cent solution
of sulphate of potash prevented mosquitoes from biting, and that they were
obliged to use this mixture while at work in their laboratory in Brazil to pre-
vent themselves from being badly bitten.

An anonymous correspondent of “ American Medicine,” who signs himself
F. A. H., says:

“T would advise the use of the oil of cassia, for the odor is not offensive to
human beings and it is an irritant poison to all kinds of insects. Besides, its
power remains for a long time after it has dried.”

Pure kerosene has been used for this same purpose. An excellent example
of its practical use came to the writer in a letter from Dr. W. H. Dade, an
Army Surgeon, writing from the Philippine Islands under date of November
15,1901:

He stated that during November, 1900, while traveling up the Cagayan
River on the steamer Raleigh, they were bothered greatly by mosquitoes, both
during the day and night, Culex and Anopheles both being present and breed-
ing in fire buckets along the sides of the vessel. The buckets were teeming with
larve. They did not seem to have thought of putting kerosene in the buckets
in order to stop the breeding, but at the suggestion of Doctor Dade a rag was satu-
rated with kerosene, the face, hands and feet were smeared with it and the rag
was put where it could be conveniently reached. When aroused from sleep by
mosquitoes another application was made. “ Those who had not used these
means before seemed perfectly surprised at the splendid immunity gained. The
odor and the greasy feeling imparted were the only drawbacks to its use.”
PYRETHRUM POWDERS 367

Doctor Dade continued to experiment with this remedy after his return from an
unsuccessful attempt to capture General Aguinaldo, and found that the addition
of one part oil of bergamot to sixteen of kerosene imparted an odor scarcely ob-
jectionable, and at the same time added sufficient body to the kerosene to pre-
vent evaporation in less than six to eight hours. After that, when the soldiers
had to leave the post, and after it became impracticable to carry cans with them
in the field for a long or protracted march, this mixture was used with the result
that the list of malarial patients was noticeably shortened. The oil of bergamot
was hard to obtain and is too expensive to be used wholesale, but the soldiers
rarely objected to the odor of kerosene and the bergamot was not continued.

In moist tropical regions where one perspires profusely, the oily mixtures
on the skin considered under this heading are transient in their effects. Under
these circumstances they should be applied rather liberally to the clothing,
particularly about the neck and wrists.

SMUDGES AND FUMIGANTS.
Hunters and campers have been in the habit of using almost anything that
will make a dense smoke as a smudge to drive away mosquitoes. In Bermuda,
fresh cascarilla bark is burned for this purpose, and elsewhere other green bark

and vegetation. For household use, however, a number of different substances
have been tried.

PYRETHRUM OR CHRYSANTHEMUM.

For many years finely ground powders known as pyrethrum powder, chrys-
anthemum powder, Persian insect powder, or Dalmatian insect powder, have
been used to kill insects. They became famous for their insecticidal effects long
before their composition was known. Their use seems to have originated in
Asiatic countries beyond the Caucasus Mountains. The powder was sold at
high price by the inhabitants and was brought by merchants to Russia and
western Huropean countries. The nature of the powder was kept a secret until
the beginning of the last century, when an Armenian merchant, Mr. Jumtikoff,
learned that the powder was obtained from the dried flowerheads of certain
species of composite plants of the genus Chrysanthemum (Pyrethrum) growing
abundantly in the region now known as Transcaucasia. The son of Mr. Jumti-
koff began to manufacture the article on a large scale in 1828, and since then the
pyrethrum industry has steadily grown and now the export in dried flowerheads
from that part of the country is very important.

The species grown commercially in the Transcaucasian region is Chrysan-
themum roseum. The species grown in Dalmatia is C. cinerariefolium, and the
crop in Dalmatia, Montenegro and Herzegovina is now the principal source of
the powder in commerce. Thirty years ago it was considered the most valuable
export of Dalmatia. The best powders are made from the dried flowerheads of
these plants. The essential principle resides in the oleoresins, which are
fugitive, so that the strength of the powders disappears with age or exposure.
Powders imported from Europe are not so strong as powders made in this
368 MOSQUITOES OF NORTH AMERICA

country from imported dried flowerheads brought over in bulk. For this reason
it was, many years ago, deemed very desirable to establish a pyrethrum-growing
industry in the United States, and in 1881 the United States Entomological
Commission imported and distributed the seeds of the two species above men-
tioned to a number of correspondents in different parts of the country. The
total success was inconsiderable. Further experiments another year met with
comparative failure. About this time more extensive plantations were made in
California and an insect powder was made by the Buhach Producing and Manu-
facturing Company, of Stockton, California, which, being American grown and
freshly ground, came into use, and is still being produced and sold under the
proprietary name of “ buhach,” the word being supposedly derived from a Sla-
vonic word “buha,” meaning flea. An article by the late D. W. Coquillett on
the production and manufacture of this powder will be found in Bulletin No. 12,
Division of Entomology, United States Department of Agriculture, 1886, pp.
7 to 16.

Formerly most of the insect powders sold in the shops in this country had
pyrethrum powder as a basis. It is now difficult to get a pure and thoroughly
efficient powder. There is often adulteration. Frequently the powder made
from the dried flowerheads is adulterated with powder made from the stems, or
with other adulterants. Under the U. 8. Insecticide Act of 1910 it is now re-
quired that the manufacturers of insect powders indicate on the label the com-
position of the powder, unless made of the flowerheads of the following three
species: 1. Chrysanthemum (Pyrethrum) cinerariefolium (Trev.) Bocc.; 2.
C. (P.) rosewm Web. & Mohr.; 3. Chrysanthemum marshallii Aschers (syn-
onym: Pyrethrum carneum M. B.).

Pyrethrum powders are usually used dry and are puffed or blown into crevices
frequented by insects, or puffed or blown into the air of a room in which there
are mosquitoes or flies. The burning of the powder in a room at night is a
common practice. The powder is heaped up in a little pyramid which is lighted
at the top and burns slowly, giving off a dense and pungent smoke with an
odor very much like that of the Chinese punk used to light firecrackers. Often
the powder is moistened and moulded roughly into small cones, and after dry-
ing it burns readily and perhaps with less waste than does the dry powder.
Of late years in mosquito countries a number of mosquito pastilles have been
sold, and many of these are moulded from powders that contain more or less
pyrethrum. ‘The efficacy of the burning pyrethrum in a close room is almost
perfect. It will not actually kill all the mosquitoes, but will stupefy them and
cause them to fall to the floor where they may be swept up and burned. With
the windows open, however, and constant currents of fresh air blowing through
the room, this fumigation is not especially effective, and it is necessary for pro-
tection to sit in the cloud of smoke.

The pungent odor of burning pyrethrum is not disagreeable to most people,
but to some it is disagreeable, and with certain susceptible individuals it pro-
duces headache. It is apparently possible, however, to volatilize the oil without
producing the actual smoke. Mr. H. W. Henshaw informs us that a few years
CAMPHOR-PHENOL 369

ago a man in Hawaii patented an appliance for producing this volatilization
which is all that can be wished for. The powder is placed on a brass or other
metal screen above the chimney of a kerosene lamp, the idea being to dissipate
the vapor of the volatile oil. According to Mr. Henshaw the effect of this
method is most remarkable. “Besides being very economical in powder there
is only a very slight odor perceptible and that is not at all unpleasant. The
effect on the mosquitoes is immediate and all that can be wished for. They
simply clear out.” Another method of burning the powder that has often been
employed by the writer consists in puffing it from an insufflator into a burning
gas jet. This is a simple method where gas is used for illuminating purposes
and produces a vapor that suffocates all mosquitoes and other insects that may
be in the room.

While pyrethrum has been mainly used as a means of clearing living-rooms
of mosquitoes, and has ordinarily been burned in the rooms while they were
occupied, it has also come into use in the extensive fumigation of houses in cases
of epidemics of yellow fever, in the effort to rid houses of mosquitoes and to
destroy all mosquitoes hibernating in cellars, attics, or disused rooms of resi-
dences, as well as similarly hibernating mosquitoes in barns and outhouses.
While reasonably effective for such purposes it does not seem to be as effective
as some of the other substances to be mentioned later and at the same time it is
more expensive.

As to the quantity to be used, the regulations of the Board of Health of New
Orleans, adopted May 25, 1903, specify the burning of 4 ounces of pyrethrum
powder to 1000 cu. ft. of space, but the President of the Board, Dr. Edmond
Souchon, a little less than a year later wrote to the U. 8S. Marine-Hospital
Service that this quantity was found insufficient for thorough work, and that 1
pound of the powder to every 1000 cubic feet of space is necessary. Ag a matter
of fact, however, the New Orleans Board of Health abandoned pyrethrum about
that time on account of the fact that the fumes do not kill mosquitoes but simply
stupefy them, so that they have to be brushed up and burned. Not willing to
run the slightest chance of having mosquitoes survive by escaping destruction
after being stupefied, the Board decided to use sulphur fumes in preference.

Nevertheless, on account of the fact that the fumes are not noxious to human
beings, there still remains a decided use for pyrethrum in everyday work in
mosquito-inhabited regions.

MIMMS CULICIDE OR CAMPHOR-PHENOL.

During a yellow fever outbreak in New Orleans, in the summer of 1905, a Mr.
Mimms, a chemist of New Orleans, invented a mosquito fumigant which was
experimented with rather extensively and found to give good results. It was
made of equal parts by weight of carbolic acid crystals and gum camphor. The
acid crystals were melted over a gentle heat and poured slowly over the gum,
resulting in the absorption of the camphor and a final clear, somewhat volatile,
liquid with rather an agreeable odor. This liquid is permanent and may be
kept for some time in tight jars. In fumigation work 3 oz. of this mixture is
370 MOSQUITOES OF NORTH AMERICA

volatilized over a lamp of some kind for every 1000 cubic feet of space. A
special apparatus for the purpose has been perfected by Doctor H. A. Veazie,
of New Orleans, but a simple apparatus may be made from a section of a stove-
pipe, cut so as to have 3 legs and outlets for draft, an alcohol lamp placed be-
neath and a flat-bottomed basin on top. The substance is inflammable but the
vapor is not explosive. The vapor is not dangerous to human life except when
very dense, but it produces a headache if too freely breathed. One of the
writers (Howard), in New Orleans on the 8th of November of the epidemic year
(1905), in company with Doctor J. H. White, in charge of the Public Health
and Marine-Hospital Service operations in the city during the epidemic, Doctor
Rupert A. Blue, Doctor Richardson, Doctor H. A. Veazie, and several other
assistant surgeons in the service, took part in the fumigation of a room contain-
ing about 1200 feet of space. A number of specimens of Culex quinquefasciatus
were flying about the room. There were 2 boxes, each about 1 foot long with
gauze sides, containing 4 dozen or more live mosquitoes each ; there was a large
tube, 2 inches in diameter, and possibly 14 feet in length, the mouth of which
was covered with mosquito bar and which lay on its side on the mantle piece and
contained several live mosquitoes. About 6 ounces of the mixture were vola-
tilized and the room was kept closed, without any effort to artificially stop
cracks, for exactly one hour. Upon re-entering and airing the room, all mos-
quitoes were found to be dead and a cockroach was also found dead on the floor,
having come up from between the cracks. The vapor is lighter than air, and the
mosquitoes in the room, previously unnoticed, soon after fumigation sought the
lower air strata of the room, gradually descending towards the floor and towards
the windows which were on one side of the room only. Sheets of manila paper
had been spread before each window and on these sheets, at the end of the hour,
were found dead all the mosquitoes to be found in the room.

An account of experiments with this mixture, containing details of apparatus,
etc., by Past Assistant Surgeon Berry, of the U. S. Public Health and Marine-
Hospital Service, is published in the Public Health Reports for February 2,
1906, vol. 21, No. 5, pp. 83 to 89. The conclusions reached by Doctor Berry
are as follows:

“4. Culicide in the proportion of 4 ounces per 1000 cubic feet used for 2 hours
with apparatus similar to that used by us kills Culex pungens, Stegomyia, and
Anopheles maculipennis and temporarily stuns the house fly.

“2. In the proportion of 3 ounces to 1000 cubic feet it does not always kill the
Anopheles maculipennis.

“3. Culicide takes fire spontaneously if heated sufficiently. It is therefore
necessary to keep the liquid at a certain distance from the flame; it is also better
to have more than one basin in a large space, and about 8 ounces is the maximum
quantity to use in one pan. All large cracks must be pasted up—the doors and
windows if loose fitting. Gummed paper spread under a window left light would
be of great benefit. (I concur with Passed Assistant Surgeon Goldberger as
to the closing up of large cracks, but more for preventing weakening of the
strength of the gas in the room by diffusion than from any belief that insects
might escape from the room.)
PYROFUME 371

“4, In the minds of intelligent operators, and used according to the methods
employed by us, it ranks next to sulphur as an insecticide in practical
fumigation.

“5. Culicide vaporizes and later cools, condensing on exposed surfaces again
as it cools. Whether in this way it injures articles of gilt and the like was not
investigated. In practical work the only articles removed from rooms were
food stuffs and animal pets and no complaint of injury was received. It gradu-
ally evaporates, leaving a persistent, though not disagreeable, odor.

“ As to the cost with the present high prices of the ingredients of Culicide,
the cost of fumigating a room with 4 ounces to 1000 cubic feet is 16 cents per
1000 cubic feet, as compared with sulphur of 7 cents, and pyrethrum of 50
cents, using 2 pounds of each of the latter per 1000 cubic feet. The estimate
does not take into consideration the alcohol used to evaporate the Culicide, but
this is not much more, if any, than that used to ignite pyrethrum or sulphur
pots. A further saving in favor of Culicide is that the apparatus can be easily
carried in the hands from place to place. Had sulphur been used in the in-
stances cited a wagon would have been necessary to transport the materials,
which were, in the case of Culicide, conveyed in street cars. The gang would
have had to be larger to move the many articles from a house necessary to be
removed in sulphur fumigation, to say nothing of the larger amount of pasting
to be done. Likewise at the end of the fumigation the time required to remove
apparatus from the room is much less. For this and other reasons, if the cost
of the labor is counted, I do not believe Culicide is much more expensive than
sulphur, and if the cost of the articles damaged by sulphur is considered, the
difference would be in favor of Culicide.”

This compound is known also by the name of camphor-phenol. Under this
name it has been experimented with by Passed Assistant Surgeon Francis. His
results, derived from a long series of tests with large numbers of mosquitoes,
indicate that it is unsatisfactory as a culicide. These were published in Public
Health Reports, vol. 22, no. 13, pages 346 to 348 (March 29, 1907). It was
found that the fumes penetrated very poorly and that large amounts of the com-
pound were necessary to obtain results. Evaporated in amounts of from 4 to 10
ounces per 1000 cubic feet of space it proved inefficient. When 8 ounces to 1000
cubic feet of space were evaporated it softened the varnish on furniture, so that
articles placed upon it adhered and were ruined. Furthermore the substance is
rather expensive to be used in large enough quantities to be effective.

PYROFUME,

Dr. J. H. McCormack, of Mobile, Alabama, has discovered that Pyrofume,
derived by a fractional distillation from pine wood, as a by-product in the manu-
facture of turpentine, is a valuable and good fumigant for mosquitoes. It is a
clear liquid of a straw color, has a pungent taste, and the odor of pine woods.
It is said to be harmless to mucous membranes, skin, fabrics, colors, polished
metal and painted wood work. A report of the experiments with this substance
by Passed Assistant Surgeon Francis, of the U. 8. Public Health and Marine-
Hospital Service, is published in Public Health Reports, June 29, 1906, vol. xxi,
No. 26, pp. 711, 712. A summary of Dr. Francis’s experimental work follows:

“1, As compared with sulphur, pyrofume stands on an equal footing in price.

“2. Whereas the Federal regulations require two hours exposure to sulphur,
pyrofume is efficient against mosquitoes in one hour.

25
372 MOSQUITOES OF NORTH AMERICA

“3, While sulphur is injurious to metals, fabrics, paint, and colors, pyrofume
leaves them unehanged. . ;

“4, Pyrofume is suitable for fumigating the engine rooms and cabitis of
ships, and for cars and fine residences.

“5. In amounts necessary to kill mosquitoes it does not injure bananas.

“6. A person can walk about in a room full of fumes and can sleep without
discomfort in a room two hours after fumigation.

“¥, It requires only five minutes to fumigate a large room of 5000 cubic feet.

“8. The fumes are generated outside the room and conducted into it.”

The conclusions were favorable, but the substance has not been taken up
in the practical work of the Public Health Service on account of the fact that
special contrivances necessary for the best application of the substance have

not yet been perfected.

SULPHUR DIOXIDE.

The damage done by sulphur dioxide to household goods is the principal
objection to its use as a fumigant, but in the case of yellow-fever epidemics,
where absolutely thorough fumigation is necessary, it is the most reliable of all
substances to use. Jt was used practically exclusively in the anti-mosquito
work during the yellow-fever outbreak of 1905 in the city of New Orleans.
Houses suspected of containing yellow-fever infection were fumigated in the
most thorough way. Every effort was made to close all crevices in the rooms
fumigated. Heavy paper was pasted over all apertures, including cracks. This
gas is obtained by burning flours of sulphur or lump sulphur in a small pot,
fire being started with alcohol. It should be used on a bright day and pots and
polished metal and delicate things should be removed. It has been found that
two pounds of sulphur for each 1000 cubic feet of space will be perfectly
efficient against mosquitoes and other insects. Sulphur candles may be used
where available. For an excellent account of certain careful experimentation
with sulphur, see an article by Passed Assistant Surgeon Francis, of the U. S.
Public Health and Marine-Hospital Service, published in Public Health Re-
ports, March 29, 1907, vol. xxii, No. 13, pp. 346 to 348.

Writing of sulphur, Giles objects to pure sulphur fumigation on account of
the difficulty of burning it, and suggests a mixture of one part of nitre and
charcoal to eight of sulphur, the mixture being made up in pastilles weighing
four ounces each by means of a little gum water, dried in the sun. In India
he burned one of these pastilles for every thousand feet of space and found that
the effect was admirable, and that even in thatched buildings hardly a mos-
quito escaped. After fumigating, the floor of a bathroom in which hardly any
mosquitoes could be found was covered with dead mosquitoes, which indicates
not only the efficacy of the fumigant, but also the effectual ways in which the
Indian mosquitoes hide. He suggests that the fumigating should be done
towards the end of the hibernating season, and during the heat of the day,
when practically all of the mosquitoes are under shelter. He urges the adoption
of this method of fumigation in all government barracks, showing that each
pastille costs no more than one Lee-Medford cartridge, and that the annual bill
SULPHUR FUMIGATION 373

for invaliding men who have been educated to use the latter is so heavy that
it would be well to adopt any measure likely to diminish it.

In the course of the admirable work carried on in recent years in Rio de
Janeiro, and which has achieved such brilliant results, it has been found that
sulphur has given the best results in the disinfection of houses. Cruz has given
the following account of the method employed:

“The house to be disinfected was completely closed. Every opening or orifice
where gas might escape was sealed with gummed paper. The furniture, too,
after being thoroughly cleansed, is tightly closed. Metallic or gilded objects
are protected with a covering of vaseline. After the roof is covered over with
canvas the garrets are opened for the free access of sulphur gas. The canvas
is fastened to the walls with laths. Then sulphur is burned in the proportion of
10 to 20 grams per cubic meter, being deposited in several receptacles dis-
tributed about the house and kept clear of the floor. Each receptacle should not
contain more than 1 kilogram (2.2 pounds) in order to insure complete com-
bustion. In the vacant spaces under the roof the burning sulphur should be
placed in receptacles set into others containing water, to avoid danger of fire.
After all the receptacles are placed the workmen close up the only exit left open
and keep the house thus sealed for not less than 2 hours. The heated air and
that displaced by the sulphur gas escapes through the crevices of the roof, but
the mosquitoes are kept in by the canvas covering.”

In the admirable fight against the yellow-fever mosquito in New Orleans in
the summer of 1905, the following directions for fumigating with sulphur
dioxide were given out by the health authorities:

“ Remove all ornaments of metal, such as brass, copper, silver and gilt from
the room that is to be fumigated. All objects of a metallic nature, which can
not be removed, can be protected by covering the objects tightly with paper, or
with a thin coating of vaseline applied with a brush.

“ Remove from the room to be fumigated all fabric material after thoroughly
shaking. Open all drawers and doors of furniture and closets.

“The room should be closed and made as tight as possible by stopping all
openings in chimney, floor, walls, keyholes and cracks near windows and doors.

“ Crevices can be closed by pasting strips of paper (old newspapers) over
them with a paste made of flour.

“The sulphur should be placed in an iron pot, flat skillet preferred, and this
placed on bricks in a tub or other convenient water receptacle with about an
inch of water in the bottom. This is a precaution which must be taken to guard
against accidents, as the sulphur is liable to boil over and set fire to the house.

“ The sulphur is readily ignited by sprinkling alcohol over it and lighting it.

“ The apartment should be kept closed for two hours, and then opened up and
well ventilated.

“ Note.—To find the cubic contents of the room, multiply the length of the
room by the width, and this total by the height, and to find the amount of
sulphur necessary to fumigate the room divide the cubic contents by 500, and
the result will be the amount of sulphur required in pounds. :

“Take, for example, a room 15 feet long, 10 feet wide and 10 feet high, we
would multiply 15 x 10 x 10, equals 1500 cubic feet. Divide this by 500 and
you will have the amount of sulphur required, viz.: 3 pounds.”

After a rigid series of experimental tests, Rosenau, of the U. S. Public Health
and Marine-Hospital Service, concludes that sulphur dioxide is unexcelled as an
insecticide. He shows that very dilute atmospheres of the gas will quickly kill
374 MOSQUITOES OF NORTH AMERICA

mosquitoes, and that it is quite as efficacious when dry as when moist. He
shows that it has surprising power of penetrating through clothing and fabrics,
and that it will kill mosquitoes even when hidden under four layers of toweling
in one hour’s time and with very dilute proportions. He states that although
this substance has long been disparaged as a disinfectant because it fails to kill
spores, it must now be considered as holding the first rank in disinfection
against yellow fever, malaria, filariasis, and other insect-borne diseases.

MERCURIO CHLORIDE.

In the Public Health Reports, volume 24, No. 50, December 10, 1909,
pp. 1859-1861, Surgeon G. M. Guiteras, U. S. Public Health and Marine-Hos-
pital Service, has recounted a series of experiments with this substance, the use
of which was first suggested to him by G. F. Matzke, steward on the American
steamer “ Beecham,” who told Doctor Guiteras that he had used it in the cabin
of his vessel with success. Doctor Guiteras carried out a series of five experi-
ments in a room 12 feet high by 15 feet by 13} feet, having a capacity of 2385
cubic feet, sublimating the mercuric chloride in a porcelain evaporating dish
over an alcohol lamp. Mosquitoes in cages approximately containing a cubic
foot of space, covered with wire gauze, were exposed at varying elevations in
the room, and from 30 to 60 grams of mercuric chloride were sublimated at ex-
posures varying from two to three hours, at temperatures of from 77 to 88
degrees. Mosquitoes in the upper part of the room were invariably killed, while
some of those very near the floor escaped, most of the latter however being killed,
and the remainder never recovering perfectly, except in one experiment where
the temperature was only 77° F. Twenty-five grams of mercuric chloride were
found to be sufficient for 1000 cubic feet of space. He showed that about 20
minutes are consumed in sublimating 60 grams of the chloride; that brass work
is not tarnished, and that nickel-plated work and instruments are not tarnished
when wiped off immediately after fumigation. He further showed that painted
surfaces are unaffected unless the chloride is sublimated close to them and they
are not immediately wiped off. Moreover it does not affect colored silk, cotton
or woolen goods. The poisonous qualities of the substance, in Guiteras’s opinion,
do not constitute a real danger. When the room was opened after the experi-
ments, he found it filled with a thick mist, but the room was entered without
any especial precaution and the windows were opened. In a few minutes the
vapor was carried away, leaving a slight deposit on the surfaces within the room.
This was allowed to remain for two or three days, and the room was used in
the meantime without any bad results. The deposit, however, should have been
removed with a damp cloth, and with this ordinary care, the experimenter be-
lieves, there will be no danger in the use of the substance.

The advantages he considers to be, the facility of obtaining mercuric chloride,
the small quantity necessary, and the simplicity of its use; a good alcohol lamp
and a porcelain evaporating dish constitute all the machinery necessary, and its
use is certainly much more convenient than sulphur where the operators have to
FUMIGANTS 375

carry about heavy iron pots and barrels of sulphur. As to expense, he shows
that at one dollar per pound the 25 grams used per one thousand feet cost some-
what less than half a cent, whereas two pounds of sulphur per one thousand
cubic feet would cost six cents. Moreover, it is pointed out that in practical
work on a large scale the expense and trouble of hauling the disinfecting
equipment from one place to another would be greatly diminished. He con-
cludes that while mercuric chloride can not altogether take the place of sulphur,
it has a hitherto unrecognized effect, especially with reference to flies and
mosquitoes.
OTHER FUMIGANTS.

In the early anti-mosquito work in European cities different substances were
experimented with. Fermi and Lumbao, in their outlined experiments, recom-
mend chlorine gas. These writers advise that 4 or 5 spoonfuls of chloride of
lime be placed in a dinner plate and that from 5 to 10 cubic centimeters of crude
sulphuric acid be poured upon it. This liberates the chlorine gas which kills
the mosquitoes. The same writers claim that the vapors of chloral act rapidly,
killing mosquitoes in a few seconds. Celli and Casagrandi in their early ex-
periments in Italy recommended a substance called larycith III, which is prob-
ably a misprint for larvicide. This is dinitrocresol, a yellow aniline color,
which kills adult mosquitoes when burned in small quantities. Formaldehyde
gas was recommended in 1890, but has been found to have almost no insecticidal
value..

Doctor John B. Smith found that the powdered stramonium or jimson weed
(Datura stramonium) can be burned to advantage in houses. He recommends
8 ounces to fumigate 1000 cubic feet of space. He states that it should be made
up by the druggist with nitre or saltpetre, 1 part to 3 parts of Datura, so as to
burn more freely. He states that the fumes are not poisonous to human beings,
are not injurious to fabrics or to metals, and can be used with entire safety.
He suggests that it be burned in a tin pan or on a shovel. (See Bulletin 216,
New Jersey Agricultural Experiment Station, page 12.)

A long list of fumigants is given by Celli in his work entitled “ Malaria ac-
cording to the new researches,” and this list has received a critical review
which carries at the same time the results of certain experimental work by
Arthur J. Kendall, in Bulletin No. 1 of the Laboratory of the Board of Health,
Isthmian Canal Commission, Panama, 1906. Bulletin No. 2 of the same
service (1906) contains an account of experiments in practical culicidal fumi-
gation, also by Doctor Kendall.

The burning of dried orange peel has been recommended as a deterrent against
mosquitoes, but there seem to be no records of conclusive experiments, although
we have been assured of its efficacy by a Japanese physician visiting the United
States.

In the course of his experiments with different disinfectants against mos-
quitoes, Rosenau, of the Public Health and Marine-Hospital Service, in Bulletin
No. 6, of the Hygienic Laboratory (September, 1901), did his principal work
with the formaldehyde and sulphur dioxide. We have mentioned his con-
376 MOSQUITOES OF NORTH AMERICA

clusions with regard to the latter substance in a previous paragraph. Formal-
dehyde gas, on account of its germicidal use, was early suggested against mos-
quitoes when their importance in the réle of carriers of disease was ascertained,
so that exact experimentation was necessary. Rosenau’s results were as follows:

“ Formaldehyd gas is a feeble insecticide. Mosquitoes may live in a very
weak atmosphere of the gas overnight. It will kill them, however, if it is
brought in direct contact in the strength and time prescribed for bacterial dis-
infection. For this purpose any of the accepted methods for evolving the gas
is applicable, but the methods which liberate a large volume in a short time are
more certain than the slower ones.

“ Direct contact between the insects and the gas is much more difficult to
obtain in ordinary room disinfection against mosquitoes than against germs,
because the sense of self-protection helps the former to escape from the effects
of the irritating gas. They hide in the folds of towels, bedding, clothing, hang-
ings, fabrics, and out-of-the-way places where the formaldehyd gas does not
penetrate in sufficient strength to kill them. The gas is polymerized and de-
posited as paraform in the meshes of fabrics, which prevents its penetration, and
large quantities are lost by being absorbed by the organic matter of fabrics,
especially woolens. In our tests, whenever the insects were given favorable
hiding places, such as in crumpled paper or in toweling, they quickly took ad-
vantage of the best place for themselves and thus escaped destruction.

“ There is a striking analogy between the strength of the gas and the time of
exposure necessary to penetrate the fabrics in order to kill mosquitoes, and the
strength and time necessary to penetrate in order to kill the spores of bacteria.

“ Mosquitoes have a lively instinct in finding cracks or chinks where fresh
air may be entering the room, or where the gas is so diluted that they escape
destruction. They are able to escape through incredibly small openings. Some
of the smaller varieties, such as the stegomyia fasciata can get through a wire
screen having 12 meshes to the inch. Therefore, formaldehyd gas can not be
trusted to kill all the mosquitoes in a room which can not be tightly sealed.

“Tt is concluded, that to succeed in killing all the mosquitoes in a closed
space with formaldehyd gas, the following definite requirements are essential :
A very large volume of the gas must be liberated quickly, so that it may diffuse
to all portions of the space in sufficient concentration. The room must have
all the cracks and chinks where the insects may breathe the fresh air carefully
sealed by pasting strips of paper over them. The room must not contain heavy
folds of drapery, clothing, bedding, or fabrics in heaps, or so disposed that the
insects may hide away from the full effects of the gas.”

REMEDIES FOR MOSQUITO BITES.

It must have been the experience of most people that ordinarily little swell-
ing and irritation results from the puncture of a mosquito where there has been
no scratching or rubbing of the part. But individuals vary greatly in this
respect and it is undoubtedly true that not only do different species of mos-
quitoes vary in their effect but that different individuals of the same species may
also vary. The application of household ammonia has been found by many to
give relief and alcohol is also said to stop the irritation. Dr. E. 0. Peck, of
Morristown, N. J., finds glycerine a sovereign remedy. Touch the bite with
glycerine and in a few minutes the pain is gone. Dr. Charles A. Nash, of New
York City, marks the punctures with a lump of indigo and states that this
instantly stops the irritation, no matter whether the application is made im-
MOSQUITO TRAPS 377

mediately or after the lapse of a day or so. The most satisfactory remedy known
to the writer from his own personal experience has been moist soap. Wet the end
of a piece of ordinary toilet soap and rub it gently on the puncture and speedily
the irritation will pass away. Mr. Charles Stevenson, of Montreal, writing to
the Canadian Entomologist in September, 1901, stated that he had found
naphthalene mothballs to afford immediate relief from the bites of dangerous
diptera including mosquitoes and that a friend of his had used it successfully
on flea bites. He advises rubbing the mothball on the affected part for a few
minutes. Naphthalene is also recommended by Prof. Boges, Director of the
National Board of Health at Buenos Ayres.

Iodine is frequently recommended for this purpose, and a note in a recent
number of the Journal of Tropical Medicine and Hygiene recommends a modi-
fication in the shape of 30 to 40 grains of iodine to the ounce of saponated
petroleum, stating: “ A few drops rubbed in a mosquito bite or wasp sting allay
the pain instantaneously.”

Rev. R. W. Anderson, rector of St. Thomas and St. Denis, wrote us from
Wando, South Carolina, some years ago, that he has often found that by holding
his hand to a hot lamp chimney the irritation of mosquito punctures would be
instantly relieved.

APPARATUS FOR CATCHING ADULT MOSQUITOES.

In a paper entitled “ A Preliminary Account of the Biting Flies of India”
(Bulletin No. 7, Agricultural Research Institute, Pusa, India), Mr. H. Maxwell-
Lefroy, Imperial Entomologist, describes on pages 12 to 15 an apparatus which
he used to catch mosquitoes in his bungalow. In the U. 8S. Daily Consular
Trade Reports, Department of Commerce and Labor, Bureau of Manufactures,
March 3, 1909, page 10, Consul General William H. Michael, of Calcutta, men-
tions this apparatus, stating it to be an invention by Mr. Lefroy. In his account,
however, Mr. Lefroy does not claim it as an invention of his own.

He used a wooden box, lined with dark geen baize and having a hinged door;
the trap was 12 inches long, 12 inches broad and 9 inches deep; a small hole,
covered by a revolving piece of wood or metal was prepared in the top of the
box, and tin was placed on the floor inside. Owing to the habit of mosquitoes
to seek a cool, shady place in which to rest, such as a dark corner of the room,
or bookshelf, or something of the sort, they will enter this trap, which is put in
the part of the room most frequented by mosquitoes ; all other dark places being
rendered uninhabitable, so far as possible. Mr. Lefroy writes: “ My room being
open to the verandah, hordes of mosquitoes come in, and as the room is lined with
bookshelves there are many desirable sleeping places. The trap stands in a
shady corner, and a large number of mosquitoes enter it when they come home in
the morning; the rest are usually driven out of the bookshelves either with a
duster or a little tobacco smoke. Finding this desirable sleeping place un-
touched they go in; the door is then slammed and fastened. At the top of the
box is a small hole with a movable plate to close it; through this a teaspoonful
or less of benzene is introduced and the plate put back. After a little time all
378 MOSQUITOES OF NORTH AMERICA

the mosquitoes are dead. The box is taken to the verandah and opened there
till the fumes of benzene escape.”

In this way Mr. Lefroy caught 2336 mosquitoes in thirty-one days, a daily
average of 83.75; daily average of females 22.68. At the same time 23 of the
biting sand flies of the genus Ceratopogon were caught. He further states that
whereas the inmates were before disturbed with mosquitoes and sand flies, which
especially attacked the baby, the pest practically entirely ceased. All of the mos-
quitoes were not exterminated, but so large a portion were destroyed that the
inmates of the house suffered no more. Mr. Lefroy goes on to say: “I am not
prepared to recommend this as a universal remedy. It must be sensibly used; a
small amount of personal effort in teaching a servant is necessary at first. But
where mosquitoes are a plague, especially to little children, the housekeeper’s
thirst for the blood of the mosquito may rise to so great a pitch that she will
welcome this device and take a delight (as we do). in counting the corpses
daily.”

The idea of Mr. Maxwell-Lefroy’s apparatus was probably first announced
by Nuttall and Shipley (Journal of Hygiene, January, 1902, vol. 2, p. 73) in
the following words:

“ We are moreover inclined to believe that suitably constructed coloured boxes
or colour-traps might be of practical utility in and about houses infested with
mosquitoes. By periodically closing the boxes and sweeping out the contained
insects into a receptacle, or, possibly by rendering the interior of the boxes
sticky, a considerable number of mosquitoes might be destroyed.”

This idea was gained by Nuttall and Shipley in the course of their experiments
with boxes of different colors to ascertain the color most attractive to Anopheles
mosquitoes.

G. Blin (Bull. Soc. de Pathol. Exotique, vol. 1, pp. 100-103, 1908) records
certain experiments made in Dahomey, in 1905, with trap-holes (trous-piéges).
His procedure consisted in digging in the ground, near houses infested by mos-
quitoes, oblique holes where the mosquitoes would come to seek darkness and
protection from the heat. Then, during the day the mosquitoes were destroyed
with a little improvised kerosene-torch, such as a wisp of straw or a stick soaked
in kerosene.

Doctor Kiilz (Archiv fiir Schiffs- und Tropen-hygiene, 1909, v. 18, p. 645)
states that these experiments of Blin were the first trap-box or trap-hole experi-
ments, evidently overlooking the earlier work of Nuttall and Shipley.

An interesting home-made apparatus in common use in many parts of the
United States is very convenient and effective. It consists of a tin cup, or of a
can cover, nailed to the end of a long stick in such a way that a spoonful or so
of kerosene can be placed in the cup which may then, by means of the stick, be
pressed up to the ceiling so as to enclose one mosquito after another. When
pressed up in this way the captured mosquito will attempt to fly and be caught
in the kerosene. By this method perhaps the majority of the mosquitoes in a
given bedroom, certainly all those resting on the ceiling, can be caught before
one goes to bed.
LARVICIDES 379

What seems an excellent idea, and which can be put in practice under certain
conditions, in the way of catching adult mosquitoes, was described in the Mont-
clair (N. J.) Herald of July 29, 1910, in which it is stated that Mr. John T.
Lyman, of 183 Cooper Avenue, Upper Montclair, has a small vacuum carpet
cleaner which is run by the electric current obtained by removing an electric light
bulb and connecting the motor of the cleaner to the socket. Just before retir-
ing, it is said, Mr. Lyman runs the cleaner over the walls of the sleeping room,
not allowing it to touch the walls, but keeping it at a distance of several inches;
the result is that every mosquito, fly or other insect resting upon the walls is
sucked into the dust bag at the lower end of the machine. This work, it is said,
is accomplished in two minutes to each room, and Mr. Lyman and his family
tetire to rest undisturbed.

A similar apparatus was used in the spring of 1910 by Dr. E. F. Phillips, of
the Bureau of Entomology, against the house fly. He found that by using a
nozzle with a fairly wide opening, such as is used in cleaning carpets, the flies
were sucked in quickly and almost always before they could make an effort to
escape. Doctor Phillips states that when the flies get into the dust-bag there is
no chance for escape as they are covered with dust and soon die.

DESTRUCTION OF LARV£E.

In considering the destruction of larvee we will first take up those measures
which involve the use of what have come during recent years to be termed
“larvicides.” The dictionary definition of the word insecticide is “ One who or
that which kills insects, as insect powder”; therefore, a definition of larvicide
would be one who or that which kills larve. But in mosquito work it has come
to be applied to those substances which are applied to bodies of water in which
mosquito larvee are living, and which results in their destruction in one way or
another. These substances, for the most part, are either poisons or more fre-
quently oils which, forming a surface film, destroy the larvee when they come to
the surface tc breathe. Ronald Ross long ago pointed out the great desideratum
in this direction in the following words: “I have long wished to find an ideal
poison for mosquito larve. It should be some solid substance or powder which
is cheap, which dissolves very slowly, and which, when in weak solution, destroys
larvee without being capable of injuring higher animals. What a boon it would
be if we could keep the surface of a whole pond free from larve simply by
scattering a cheap powder over it, once in six months or so. It is very possible
that such a substance exists, but unfortunately we have not yet discovered it.”
(Mosquito Brigades, London, 1902, pp. 33 to 34.)

A great many experiments have been tried with poisonous substances in the
search for the desideratum described by Dr. Ross, but although it is now seven
years since he wrote this paragraph we still have not discovered it. As early as
1899 Celli and Casagrandi published an account of an elaborate series of labora-
tory experiments on the destruction of mosquitoes by various chemicals in a
paper entitled “ La Distruzione delle Zanzare,” published in the Annali d’Igiene
Sperimentale. These experiments resulted in little practical good, and one of
380 MOSQUITOES OF NORTH AMERICA

the best of the larvicides, namely, the petroleum products, was discredited by
the authors in question.

PERMANGANATE OF POTASH.

In the last few years many substances have been experimented with, both in
the United States and in other parts of the world, and there has been from time
to time a newspaper notice, or a series of newspaper notices, of some new sub-
stance which careful experimentation has shown to be of little or no service.
In this way the use of permanganate of potash received much advertising in 1900,
but, as one of the writers has elsewhere pointed out, as a result of careful ex-
perimentation it was found that small amounts of the chemical have no effect
whatever upon mosquito larve. They were, however, killed by using amounts so
large that, instead of using a handful to a 10-acre swamp, as had been stated in
the newspapers, at least a wagon load would have to be used to accomplish any
result. Moreover, after the use of this large amount and after the larve were
killed, the same water 24 hours later sustained freshly hatched mosquito larvee
perfectly, so that even were a person to go to the prohibitive expense of killing
mosquito larve in the swamp with permanganate of potash, the same task would
have to be done over again a few days later.

SULPHATE OF COPPER.

In 1904 a publication by the Bureau of Plant Industry of the U. S. Depart-
ment of Agriculture, on the use of sulphate of copper against alge and other
microscopic plant life, put certain newspaper men on the wrong track and a
number of articles were published making the erroneous statement that the De-
partment of Agriculture recommended sulphate of copper as a perfect remedy
against mosquito larve. So widely was this alleged discovery heralded that
careful experiments were at once made by the Bureau of Entomology, by Doctor
Smith, of New Jersey, by Doctor Britton, of Connecticut, and by other ento-
mologists, with the result that the substance was found to be of very slight
value as a larvicide, and of really no practical value whatever.

CERTAIN PROPRIETARY COMPOUNDS.

Several proprietary mixtures or mosquito compounds have been prepared and
placed on sale for the purpose of destroying mosquito larve. A number of these
have been brought or sent to one of the writers for experimentation but, consider-
ing the cost, none of them has been of as great practical value as petroleum.
In his report on the mosquitoes occurring in the State of New Jersey, 1904,
Doctor John B. Smith describes a number of experiments with substances of
this kind, notably with certain soluble carbolic acid and cresol preparations,
with chloro-naphthaleum, and with phinotas oil, and in his report for 1907 he
gives the results of certain experiments with a substance known as “ killarve.”
It is not necessary, however, to consider any of these substances in this con-
nection except to state that phinotas oil has met with considerable use, since it
forms a milky compound with water which settles through a poo] and destroys
PETROLEUM 381

not only mosquito larve, but all other animal life in the water. It is used in
cesspools and receptacles of that kind, and it has found wide application in the
anti-mosquito work on the Isthmus of Panama.

CACTUS PASTE.

We have already spoken of the use of certain substances for forming so dense
a covering over the surface of the water as to exclude mosquito larvae from access
to air, thus bringing about their destruction. A method of bringing about this
result is described by Consul Wm. H. Bishop, of Palermo, Sicily, in the Monthly
Consular and Trade Reports, No. 331, April, 1908, in which he quotes from an
account of the experiments made by the Chief of the Sanitary Service at Gaboon,
French Africa, with cactus as a substitute for petroleum in the extermination
of mosquitoes in warm climates. Beyond this account by Mr. Bishop, we have
no further information of this remedy :

“ The thick, pulpy leaves of the cactus, cut up in pieces, are thrown into water
and macerated until a sticky paste is formed. This paste is spread upon the
surface of stagnant water, and forms an isolating layer which prevents the
larve of the mosquitoes from coming to the top to breathe and destroys them
through asphyxiation. It is true that petroleum can do the same service, but
in warm climates petroleum evaporates too quickly and is thus of little avail.
The mucilaginous cactus paste, on the contrary, can hold its place indefinitely,
lasting weeks, months, or even an entire year ; and the period of the development
of the larvee being but about a fortnight, it has the most thorough effect.”

PETROLEUM.

This substance has been more extensively used in the United States than else-
where and it is better understood in this country. In choosing the grade of the
oil, two factors are to be considered. First, it should spread rapidly ; second, it
should not evaporate too rapidly. The heavier grades of oil will not spread
readily over the surface of the water, but will cling together in spots and the
coating will be unduly thick. The rapidity of spread of film is also important.
Ronald Ross, in his “ Mosquito Brigades,” pp. 34 to 35, makes the following
statement:

“ Mr. Hankins of Agra informs me that the addition of Amyl alcohol greatly
expedites the formation of the film; and it is very necessary to obtain a film
which makes its way between the stalks and leaves of water weeds.”

Early in the course of anti-mosquito work in the United States careful ex-
periments were made by Mr. W. C. Kerr, in the work of the Richmond County
Club, on Staten Island. He tried several grades of oil and found a low grade of
oil known as “ fuel oil ” to be best adapted to the work. Of the oils which he
tried, some contained too much residuum of a thick nature, which appeared as a
precipitate and could scarcely be pumped, some were too thick in July weather
and could not be pumped at all, while others were limpid, easily handled, made
a good uniform coating on the ponds, and were very effective. So long as oil
flows readily and is cheap enough the end is gained, provided it is not too light
and does not evaporate too rapidly. The grade known as light fuel oil was recom-
mended by one of the writers to the U. S. Army workers in Cuba, at the close of
382 MOSQUITOES OF NORTH AMERICA

the Spanish War, and was found to be effective. The price of oil of this kind
has varied from $2.25 per barrel to $3.00 per barrel, f. o. b., Philadelphia.

In his early Catskill Mountain experiments one of the writers ascertained
that about an ounce of kerosene to 15 square feet of surface space is about the
right proportion, and that such a film would remain persistent for 10 days, or
slightly longer. He noticed further that even after the iridescent scum had
apparently disappeared there was still an odor of kerosene about the water and
that adult mosquitoes avoided it.

In the work done by Mr. H. J. Quayle, near San Francisco, oiling was
done upon ponds that could not be drained, upon standing pools remaining
in creekbeds during the summer, and some was also done on marsh lands.
The oil used was a combination of heavy oil of 18-degrees gravity and light
oil of 34-degrees gravity, in the proportion of 4 to 1. This mixture made
an oil that was just thin enough to spray well from an ordinary spray nozzle,
and yet was thick enough to withstand very rapid evaporation. It was applied
by means of a barrel pump where this could be used, but in the creeks and other
situations, which could not be reached by horse and wagon, the ordinary knap-
sack pump was used. The price of the heavy oil at Burlingame, California, was
2 cents a gallon, and of the lighter oil 24 cents a gallon. Mr. Quayle found that
the duration of efficiency depended somewhat on the nature of the pool and its
exposure to winds, but in no case could it be counted upon as thoroughly effective
after a period of four weeks.

This period of four weeks brings up the question as to the frequency of appli-
cations of kerosene. The persistence of the oil will undoubtedly vary with the
temperature and with the character of the pool—whether exposed to the direct
rays of the sun, shaded by trees, or exposed to the wind. Three weeks will
probably be the maximum period of efficacy with light fuel oil. The army in
Cuba renewed the oil every two weeks.

The application of kerosene to the surface of the water can be made in several
different ways. If the oil is thin it may be simply poured upon the surface and
will spread itself. The spraying method, either with the barrel pump, by knap-
sack pump, or bucket pumps must be used for the heavier oils and where there is
much aquatic vegetation. One of the writers watched the oiling of ponds with a
spraying pump in a New Jersey town several years ago. The water treated was
all in small woodland ponds, and there was necessarily a great waste of kerosene.
The spray was diffused and became scattered over the vegetation on the borders
of the pond, a large share of it being wasted in this way, while the shore vegeta-
tion was killed. On small ponds the oil can be sprinkled to advantage out of an
ordinary watering pot with a rose nozzle or, for that matter, pouring it out of a
dipper or cup will be satisfactory. In larger ponds pumps with a straight dis-
charge nozzle may be used. A straight stream will sink and then rise and spread
until the whole surface of the pond is covered without waste. The English
workers in Africa advise mopping the petroleum upon the surface of the water
by means of cloths tied to the end of a long stick and saturated with kerosene.
The use of such a mop may be desirable, even where a straight discharge pump
CORN OIL 383

has been used, in order to commingle detached surface sheets of oil. In some of
his early work on Staten Island, Dr. Doty, the Health Officer of New York, used
a pump with a submerged discharge, throwing the oil out at the bottom of a pool
and allowing it to rise to the surface. It seems that the idea was to destroy the
insects feeding at the bottom more quickly, but as most mosquito larve rise
to the top to breathe, there is practically nothing to be gained by such a method.

The use of larvicides in tropical regions introduces certain new features which
complicate the problem of mosquito destruction to a certain extent. Colonel
Gorgas, and his corps of workers at Panama, have been using petroleum very
extensively, just as they did at Havana. They find, however, that at Panama the
rapid growth of vegetation prevents the oil from spreading uniformly and that
it can not make a thin uniform film over the surface of water in which vegeta-
tion grows. They find also that alge on the surface of the waters form with
the oil a dark scum, which collects at the bottom of shallow pools. This scum
later breaks up and floats about on the surface, rendering succeeding oilings
less efficacious, and necessitating the use of larger quantities of oil. They also
find that where vegetable debris collects in a large body of water it will be blown
about as a mass, its location changing with the wind. Mosquito larve also hide
in this vegetation, which protects them from fish. The wind blows the oil to
one side of the surface and, of course, where the film is not perfect the larve find
free places to breathe. It evaporates very rapidly in the tropics. During the
rainy season it is washed away very rapidly before it destroys all of the larve.
The bulk of the oil and the cost of transportation in rough territory for work
on a large scale are disadvantages. In such work they found that they must
constantly occupy themselves in removing vegetation before oil is applied, in
order to avoid using excessive amounts of oil. They found that new growths of
alge: developed very rapidly after the oil had united with the previous crop and
sunk to the bottom.

CORN OIL.

Some effort has been made to find if there are any other oils that may be used
to better advantage than petroleum. A suggestion was once made by Mr. W.
J. Matheson that corn oil might be used. This is a substance which is made
rather extensively in certain parts of the country and which, considering the
enormous crops of corn grown in western States, which in fact are so great that
sometimes in years of overproduction corn is burned as fuel, might reasonably
be supposed to be a cheap oil. This, however, is not the case and its price is
prohibitive as compared with ordinary grades of kerosene. Experiments under-
taken in 1900 indicated that corn oil does not spread readily. It gathers to-
gether in large patches on the surface of the water, and mosquito larve rising
to the surface and finding themselves under a patch of oil will simply wriggle
violently until they find the spaces between the patches where they can breathe
comfortably and live. In this experiment the object was not only to secure a
cheap and efficient oil, but to secure a persistent oil which will not evaporate,
and which will remain for at least several weeks over the surface of the water.
Its non-spreading qualities, however, as well as its price, removes it from prac-

tical consideration.
384 MOSQUITOES OF NORTH AMERICA

PHINOTAS OIL.

In the Panama work, as previously stated, phinotas oil is used, and has been
found to have the following advantages over crude oil: It acts as a poison and
kills the larve very rapidly. It brings the larve out of their hiding-places at
once, and is useful as an aid in the detection of the presence of mosquito larve.
It is found also that in continuous heavy rains the larye are killed by the
phinotas oil before the rain dilutes the treated water to any great extent. They
find, however, that phinotas oil has certain disadvantages: It kills fish in a
solution of 1 to 5000, and it loses its efficiency very soon after application, so
that eggs may be laid upon the treated water and the larve develop. Colonel
Gorgas points out that there is considerable variation in the quality of this
preparation, as shipped to the Isthmus. Some will kill larve quickly in a solu-
tion of 1 to 3000 parts of water, while other lots require for the same results 1
part to 1000.

THE IDEAL LARVICIDE.

Colonel Gorgas has published the following list of desiderata for the perfect
larvicide for use in the tropics, agreeing with the opinion expressed by Ronald
Ross when he returned from his first visit to Africa, that nothing as yet known
is perfectly satisfactory :

“ (a) Low ultimate cost.

“ (b) Ability to affect and kill mosquito larve promptly, the more rapidly the
better. It must be effective in moving water as well as in still water.

“(c) Ability to form a solution with water and to thoroughly diffuse and mix
with all the water of a small pond if applied only to one part thereof. Also the
substance must not lose it larvacidal properties for a week or more after its
application. The longer it will retain its larvacidal properties, after it has
been placed in the body of water, the more valuable it will be.

“(d) Ability to diffuse in water and through all parts of a body of water such
as in a pond containing grass, water lilies, other aquatic vegetation, and vege-
table débris.

“(e) Ability to kill green alge promptly.

“ (f) A concentrated larvacide is necessary so that one part of it to five thou-
sand or more parts of water will promptly kill mosquito larve and pupe.

“ (g) Non-poisonous to human life or animals when taken in a strength of 1
to 1000 and accidentally used as drinking water.

“(h) That it have the property of discoloring the water to which it is applied,
or of giving off sufficient odor to induce persons not to use water containing it
in solution for drinking purposes.

“ (i) That the odor, if present, be not so obnoxious as to make its presence in
water in ponds or streams near habitations undesirable.

“(j) That it shall have a safe flash test and be nonexplosive.
“(k) That it shall be sufficiently stable so that it may be kept ‘stand-
ardized.’ ”
LARVICIDE OF THE ISTHMIAN CANAL COMMISSION.
In his “ Studies in Relation to Malaria,” Dr. Samuel T. Darling, of the
Isthmian Canal Commission, gives the following account of experiments with
larvicides :
I. CG. C. LARVICIDE 3885

“ A number of experiments were carried out for the purpose of obtaining a
cheap and efficient preparation for destroying mosquito larve. Crude petroleum
oil was frequently too viscid to have a spreading power of the highest efficiency.
When mixed with crude carbolic acid, however, its spreading powers were in-
creased. From laboratory tests it was determined that crude petroleum for
surface use on pools should not be heavier than —° Baumé (American standard).

“Much of the crude carbolic acid supplied had been found upon analyses to
consist chiefly of inert neutral oils with a small proportion, 5 to 10 per cent,
of tar acids, and, as this crude acid was used extensively as a disinfectant, ex-
periments were conducted for the purpose of utilizing, if possible, this crude
carbolic acid as a disinfectant and larvacide. It was found that crude carbolic
acid, having a specific gravity not greater than 0.96 or 0.97, and containing
about 20 per cent of phenols or tar acids, when made into a soap, with common
resin and an alkali, yielded a product which was an ideal larvacide, having ex-
cellent diffusing and toxic powers, and at the same time was a very efficient
germacide. It diffused perfectly with water, forming a milky emulsion very
destructive to mosquito larve, and having a germicidal value of, or greater
than, that of pure carbolic acid of a Rideal-Walker coefficient of 1 to 2. In this
way a very valuable larvacide and disinfectant, miscible with water, was pro-
duced from a very inferior insoluble disinfectant.

“ The larvacidal powers, when tried with Culex and Anopheles larve, varied
slightly with the quality of the crude carbolic acid, but an average result is as
follows:

“Dilution 1 to 1000: Culex larve dead in five minutes
Anopheles larve, half grown, dead in five minutes.
Anopheles larve, full grown, dead in ten minutes.
“Dilution 1 to 5000: Anopheles larve, half and full grown, dead in five
minutes.
Culex larve, half grown, dead in three minutes.
“ Dilution 1 to 10,000: Culex larve, half grown, dead in sixty-four minutes.
Anopheles larve, young, dead in fifty-two minutes.
Anopheles larve, full grown, dead in one hundred and
thirty-five minutes.
“Dilution 1 to 15,000: Small Culex larve, dead in thirty-two minutes.
Anopheles larve, full grown, dead in one hundred and
twenty-three minutes.

“ Anopheline larve seem to be slightly more resistant than Culex larve, and
all pupe are more resistant to the effects of the larvacide than larve are.”

As the result of the experimental work with larvicides Colonel Gorgas and
his assistants have constructed a larvicide plant at Ancon, and in the monthly
report of the Department of Sanitation of the Isthmian Canal Commission for
August, 1909, it is stated that 14,600 gallons of larvicide were made at a cost
of $0.1416 per gallon. The method of preparing this larvicide is quoted from
this report :

“The method of making same is as follows: 150 gallons of carbolic acid is
heated in a tank to a temperature of 212° F.; then 150 pounds of powdered or
finely broken resin is poured in. The mixture is kept at a temperature of 212°
F., 30 pounds of caustic soda is then added and solution kept at 212° F. until
a perfectly dark emulsion, without sediment, is obtained. The mixture is
thoroughly stirred from the time the resin is used until the end.

“The resultant emulsion makes a very good disinfectant or larvacide. In
fact 1 part of it to 10,000 parts of water will kill anopheles larve in less than
386 MOSQUITOES OF NORTH AMERICA

half an hour, and 1 part to 5000 parts of water will kill anopheles larvae in from
five to ten minutes, or less. This property of killing larve rapidly is of great
importance in the Tropics, where continuous rainy periods make crude oil or
kerosene much less valuable as a larvacide than it is in northern latitudes having
less rainfall. Also the larvacide acts as an algecide, and thus destroys the food
and the hiding places of anopheles larve. As it takes up very little room, com-
pared with the area it can be spread over, the cost of distribution will be much
less than that of crude oil or kerosene—considering the large territory which
the antimalarial work covers, this item alone is of great financial advantage to
the department.

“Tests have recently been made to determine approximately how much of the
new larvacide will be needed per month (rainy season) for each district.

“ Although this larvacide will be used to a large extent, yet we shall con-
tinue to use crude oil for streams having a fair velocity, as such application gives
excellent results and is as economical as larvacide would be, as the oil is spread
in a very fine film automatically. In order to make the crude oil drip with con-
tinuous regularity, a piece of metal similar to that part of a flat-wick lamp
which holds the flat wick is fastened to the oil container. It is made somewhat
larger than the wick, so that the wick fits it loosely when saturated with the
grade of fuel oil we use. This metal wick chamber is fitted to the oil container
about 3 inches from its base. The space below the wick chamber is filled with
a solution of caustic soda or of larvacide. As the oil is attracted along the wick
by capillary attraction, it comes into contact with the larvacide or caustic soda
and is ‘cut, rendered thinner. This method of procedure prevents the wick
from being clogged by the thick fuel oil and enables the wick to drip the oil
desired.”

In the September, 1909, report, it is stated that the new larvicide was giving
very satisfactory results and would undoubtedly reduce the cost of anti-malarial
work, besides being more effective than crude oil in many places. It also has
some value as a destroyer of vegetation, thus making conditions less favorable
to mosquito breeding. In the October report satisfaction with its use is again
expressed, and it is stated that the fact that it kills the grass at the edges of the
ditches will be of importance in reducing the cost of anti-malarial work.

Mr. August Busck, of the Bureau of Entomology, U. 8. Department of Agri-
culture, has recently had an opportunity to witness the effectiveness of this
preparation and has furnished us the following account of its effects and manner
of application:

“ Friday I had a very excellent opportunity to observe the application and
result in the field, in one of the outlying districts, near Rio Grande on the
Isthmian Canal Zone. Here was about a mile and a half of a small slow-run-
ning stream, passing through a scattered native village and through thick brush,
which for some reason had been overlooked or neglected. This was literally
swarming with Anopheles larve and pupe everywhere along the grassy edges
and in the small pools caused by the native washerwomen, or by pigs, poultry
and horses. It was about as nasty a place as I have seen, producing thousands
of adults every day.

“ The local sanitary inspector, Mr. Trask—one of the most efficient—kindly
postponed action until I had been over the ground thoroughly, and then started
a man with a knapsack-pump, another with larvicide supply for the pump and a
foreman to oversee the job, from the head spring down along the stream; they
walked right along and sprayed with a 1 to 6 solution as they went, covering
POISONOUS PLANTS 387

the course in less than an hour. Within two minutes after the application on
any part of the stream all mosquito larve there were dead.

“T remained several hours afterwards, so as to be able to work alone, dipped
and looked carefully on knees and hands all along that stream, but not one live
larva was found, where hundreds could be taken in a single dip before.

“ A few hours after the application the water course was again quite clear and
could be used for drinking and washing as before.

“The vegetation did not appear to have suffered in any way, though that
might take longer to show. Most of the other water insects were dead, but a
considerable number of water beetles, Hemiptera and dragon-fly larve withstood
the treatment, and I have no doubt but that the percentage of the larvicide
solution can be so regulated that it would kill all the mosquitoes and not the
tougher predaceous insects.

“ There were no fish in the stream, so I can not say, from personal observa-
tion, how it would affect them, but Mr. Trask says they can endure considerable
of the larvicide without dying.”

DESTRUCTION OF LARV£E BY SENSITIZATION TO LIGHT.

Dr. Gunni Busck, of Copenhagen, has recently carried out novel experiments
in mosquito destruction :

“T have this fall tried to solve the question of killing mosquito larve by an
entirely different method, on the supposition that it might be possible, through
solutions of suitable coloring matter (Erytrosin, Rose Bengal, etc.), to sensitize
mosquito larva: so that they would be killed by the sunlight or mere daylight,
to which they are directly exposed under natural conditions, when they assume
their normal position for respiration at the surface of the water.

“Tt was shown by my experiments that it really is possible to thus sensitize
mosquito larve and that they die in thin solutions of the above mentioned
colors, if they are exposed to light, even if only diffused daylight, while they
remain alive, pupate and develop to adults in these same solutions, if they are
kept in darkness.

“Tt was however necessary to use more concentrated solutions of the colors
than I had anticipated, and as these colors moreover are rather expensive, the
method can at present in no wise compete with the oil methods. The experi-
ments will be continued and their scope widened this coming season.”

POISONOUS PLANTS.

Decoctions and emulsions of an African leguminous plant, Derris uliginosa,
have been recommended for larvicidal use, and experiments conducted by Bal-
four at the Wellcome Research Laboratories at Khartoum show that it has con-
siderable potency. It also kills fish, different species of Derris being well known
for this quality, so that even in regions where these plants are native they have
only a limited use as insecticides.

Recently Daniels (Tropical Medicine and Hygiene, Part 1, 1909, pp. 77-78,
120) has advocated the use of the “tuba root,” also belonging to the genus
Derris, which is used in the East Indies to poison fish, to destroy mosquito larvee.
The commonly employed species is Derris elliptica. Other plants are employed
in other parts of the world to stupefy fish and some of these might prove to be
effective against mosquito larve. Daniels says of Derris:

“The roots are crushed and thrown into the water, and the milky fluid from
the fresh roots, even in minute quantities, and much diluted, will destroy the
26
388 MOSQUITOES OF NORTH AMERICA

larve, and for small collections of fluid, cesspits, etc., is highly effective, and
though killing off most forms of animal life does not render the water as putrid
or offensive as the use of oils. When fish are present these would be destroyed,
and therefore this method is not advisable in larger collections of water.”

SALT.

During the 1905 outbreak of yellow fever in New Orleans an attempt was
made to destroy mosquito larve in the open gutters of the city by the use of
common salt. Dr. H. A. Veazie wrote us that the results were good where the
work was properly done. Shortly after operations were begun there was a flight
into the city of Aédes sollicitans from the salt marshes northeast of New Orleans.
Indignant citizens ascertaining from experts the name and habits of the species
jumped to the conclusion that salting the ditches had brought about suitable
breeding conditions for sollicitans and that the invasion of the city by that
species was a direct result of the work of the sanitary officials.

ABOLITION OF BREEDING-PLACES OF HOUSEHOLD MOSQUITOES.

In considering this question, just as in considering so many questions relating
to mosquitoes, a complication arises from the diversity of facts concerning the
life-histories of the different species of mosquitoes, facts discovered, for the
most part, within the past ten years. At the time of the publication of Bulletin
25, New Series, Division of Entomology, U. S. Department of Agriculture, in
1900, the habits of but a very few species of mosquitoes were known and the
generalizations drawn from the knowledge of these few species were altogether
too broad and must now be greatly modified. The breeding-places of different
species are quite peculiar. Those of the commonest household mosquitoes,
namely Culex pipiens in the North and Culex quinquefasciatus and Aédes
calopus in the South, correspond best with the generalizations formerly made,
breeding as they do in every receptacle of water about residences, and the
abolition of all such accumulations of water means their destruction. Where
the rain-water barrel or the rain-water tank are necessary they should be
screened. In New Orleans and other southern cities the boards of health are now
enforcing the screening of these receptacles. The screening should be done with
extreme care, a fine mesh screen being used and the fitting made very perfect.

About a given house the waste places in the immediate vicinity should be
carefully searched for tin cans, bottles, wooden or tin boxes in which water can
accumulate, and all such receptacles should be destroyed or carted away. The
roof-gutters of the building should be carefully examined, to make sure that
they are not clogged so as to allow water to accumulate. The chicken-pans in
the poultry yard, the water troughs for domestic animals, the water-cup of the
grindstone, are all places in which mosquitoes will breed, and in them water
should not be allowed to stand for any length of time. In the South the water
accumulating under water tanks should be treated or drained away. The
urns in the cemeteries at New Orleans have been found to breed mosquitoes
abundantly. The holy-water fonts in Catholic churches, especially in the South,
have commonly been found to breed mosquitoes; in some places sponges have
CONTROL OF DOMESTIC MOSQUITOES 389

been substituted for standing water, and other churches have adopted a closed
font, which allows the holy water to issue through a small spigot. In still other
churches salt has been put in the water to prevent the breeding of mosquitoes.

Even in the house mosquitoes breed in many places where they may be over-
looked. Where the water in flower vases is not frequently changed mosquitoes
will breed. They will breed in water pitchers in unused guest rooms. They will
breed in the tanks in water closets when these are not frequently in use. They
will breed in pipes and under stationary washstands where these are not fre-
quently in use, and they will issue from the sewer traps in back yards of city
houses during dry spells in the summer time, when sewers have not recently
been flushed by heavy rains. In warehouses and on docks they breed abundantly
in the fire buckets and water barrels.

In country houses in the South, where ants are troublesome and where it is
the custom to insulate the legs of the tables with small cups of water, mosquitoes
will breed in these cups unless a small quantity of kerosene is poured in. Where
broken bottles are placed upon the stone wall to form a cheval-de-frise, water
accumulates in the bottle fragments after rains and mosquitoes will breed there.
Old disused wells in gardens are frequent sources of mosquito supply even where
apparently carefully covered, and here the nuisance is easily abated by the occa-
sional application of kerosene. The same thing may be said of cesspools. Cess-
pools are frequently covered with stone and cement, but the slightest break in
the cement will allow the entrance of these insects. Breeding often goes on in
cesspools without the cause of the abundance of mosquitoes in the neighborhood
being suspected. One of the writers remembers, for example, on one occasion
walking through a New Jersey garden and noticing a covered cesspool with a
slight crack in the cement. He remarked upon the danger to the proprietor of
the estate, who replied that mosquitoes could not possibly gain entrance to the
water. Later in the evening, about dusk, the same spot was passed again and a
cloud of mosquitoes was seen issuing from the crack so abundantly that at a
little distance it seemed like a stream of smoke. A little kerosene put a stop to
further breeding.

Fountains and ornamental ponds are frequent breeding-places, and here the
introduction of fish, as indicated in another place, is usually all-sufficient. It
frequently happens, however, that the grass is allowed to grow down into the
edges of ornamental ponds and mosquito larve find refuge among the vegeta-
tion and so escape the fish. Broad-leaved water plants are also often grown in
such ponds, and where these broad leaves lie flat upon the surface of the water,
as they frequently do, one portion of a given leaf may be submerged so that
mosquito larve may breed freely in the water over the submerged portion of the
leaf, protected from fish by the leaf itself. It is necessary, therefore, to keep the
edges of such ornamental ponds free from vegetation and to choose aquatic
plants which will not afford mosquito larvee protection. In many small country
towns, even where there is a water supply, tanks are to be found under the roofs,
to supply bathrooms. Such tanks should be screened, since mosquitoes gain en-
trance to the tankroom, either through dormer windows or by flying up through
390 MOSQUITOES OF NORTH AMERICA

the house from below. About a large old house there are so many of these
chance breeding-places that only the most careful search will find them all.
Frequent change of water, or the use of kerosene, will render them all harmless.

PREVENTION OF SEWER BREEDING.

In community work in cities all of the points mentioned must be borne in
mind, and in the portions of the community where the residences are for the
most part detached villas, in the absence of swampy surroundings, the house-
holders are in the main responsible for the presence of mosquitoes. There are,
however, breeding places for which the town may be said to be responsible, and
these entirely aside from public fountains, reservoirs or marshes. It seems
unlikely that in any general sewerage system mosquitoes breed in the sewers
proper. That they do breed in the catch basins is well known. The purpose of
the catch-basin is to catch and retain, by sedimentation, sand and refuse which
would otherwise enter the sewer and obstruct it. Itis intended to be water-tight
and to hold a considerable body of water which stands in it up to the level of

 

6.—Type of catch basin in common use in back yards
of Wy cumiantes houses in which water stands permanently.

the outlet pipe. Such catch basins are very commonly used in back yards and at
the crossings of streets. The water is replaced only by rain or when street or
yard surfaces are washed. In dry seasons the period of stagnation may last
several weeks, certainly long enough for mosquito breeding. As a matter of
fact, mosquitoes in midsummer do breed in such basin-traps or catch-basins. In
the work against mosquitoes in Brookline, Mass., in 1901 and 1902, previously
referred to, Culex pipiens was found breeding abundantly in catch-basins, and
more than 1000 such basins were regularly treated with petroleum. It is a
matter of common observation in the city of Washington that during the usually
dry months of July, August and September, mosquitoes are very numerous
throughout the city, in quarters where there are no possible breeding-places
other than these catch basins, and more particularly the large catch basins of
the sewer outlets at the street corners.

The suggestion has been made that in cities it may, under certain circum-
stances, be possible for mosquitoes to breed in water accumulating in the under-
ground troughs of electric railways, but so far as known to the writers no exact
affirmative observations have been made. That there is abundant opportunity
for water to accumulate in these troughs and that it does so accumulate there
can be no doubt.
CONTROL OF MARSH MOSQUITOES 391

Referring again to the breeding of mosquitoes in catch-basins or sewer-traps,
it was shown as early as 1900 by Mr. T. Pergande, of the Bureau of Entomology,
that the common rainwater-barrel mosquito breeds in small sewer-traps in the
rear of houses in southeast Washington. He determined this point by putting
a gauze screen over the sewer-trap in his own yard and finding adult mosquitoes
under the screen, morning after morning. Of late years, in practically all the
city of Washington, and in fact, notably in the northwest section, where is to
be found the better class of residences, and where the general conditions are such
as to preclude the possibility of the breeding of mosquitoes in other places, sewer-
trap bred mosquitoes are very annoying, especially during the dry spells in
July, August and September. At one time the city catch-basins, located at
the corners of the streets, were flushed at least once in ten days, under the orders
of an efficient official in charge of sewers for the District of Columbia. This
procedure, if fully carried out, would prevent the breeding of mosquitoes in
these basins. The private catch basins, usually situated near the kitchen door,
are not under city control and are so constructed as to hold water indefinitely
and to permit the breeding of a lesser number of mosquitoes during a protracted
dry spell. It is easy to avoid this breeding by putting a small cupful of kero-
sene into the sewer trap at intervals of from ten days to two weeks. But the
difficulty arises that during the months in question, in the northwest quarter
of the city, many houses are closed for the summer, and the treatment of the
catch-basins on the premises of temporary absentees can only be accomplished
by someone in authority, as a sanitary inspector, for example. Malarial mos-
quitoes occasionally breed in these catch basins, as one of us (Dyar) found two
larvee of Anopheles in a small catch basin in the yard of his premises during
August, 1912. They were easily removed by flushing the drain.

REMOVAL OF BROMELIACEOUS PLANTS.

Sir Rubert Boyce, in his “ Mosquito or Man?,” calls especial attention to
the wild pines or Bromeliacex as breeding places of mosquitoes in the American
tropics, and to the extraordinary numbers in which these epiphytes occur in
certain localities. He states that one Saman tree, which was cleaned up for the
purpose of destroying mosquito breeding-places, yielded 26 ceart-loads of these
epiphytes whose total weight was 3.62 tons. He shows that each plant may hold
from ten to twenty ounces of water and that the total volume of water repre-
sented by these parasites of a single tree was probably equivalent to a good-sized
pond.

DRAINAGE MEASURES AGAINST NON-DOMESTIC SPECIES.

The drainage of swamp areas for agricultural or other industrial reasons
needs no argument nor treatment here. The value of reclaimed swamp land for
various purposes is treated somewhat in extenso in an earlier section, “ Value
of Reclaimed Lands.” The drainage of swamp areas primarily in order to im-
prove sanitary conditions and to reduce the annoying scourge of mosquitoes,
which in itself frequently prevents the proper development of neighboring
392 MOSQUITOES OF NORTH AMERICA

regions, is in operation and needs no argument. Drainage on a small scale for
the purpose of doing away with mosquitoes has been practiced for a long time.
In “ Mosquitoes,” p. 198, Howard shows how, by an expenditure of $40 for
drainage, in the summer of 1900, in a Maryland village, malaria was practically
abolished, although the previous summer there had been one or more cases in
every family in the district.

One of the editors of the Scientific American, Mr. Beech, has given a good
illustration of the good effect of drainage work prior to the general interest in
mosquito destruction, which is quoted (loc. cit., pp. 208-209) as follows:

“In the town of Stratford, Conn., where I have resided for the past forty-five
years, we have been greatly plagued by swarms of mosquitoes, so great, in fact,
that the ‘ Stratford mosquito’ became a well-known characteristic of Stratford.
We have in the southern part of our town, bordering on the sound, several acres
of marsh-land or meadow, which would become periodically overflowed with
water in the summer and a tremendous breeding-ground for mosquitoes, and
this plague to the town continued until about 1890-91, when a party from
Bridgeport, Conn., purchased a large section of the meadows and began to pro-
tect them by a dike, both on the north and south ends, which shut out the water.
In addition to this, numerous drain ditches were made which helped to carry
the water away. The result of this work made the land perfectly dry and spongy,
so that after a rain no pools collected on the surface of the meadow and the
creation of the mosquitoes was prevented. The transformation was so remark-
able that people outside the town would hardly believe that it had been effected,
and a year or two later the town voted a special appropriation of $2000 to the
party who undertook to build the dike and render the meadows mosquito-proof.
It had also the effect of placing on the market a large tract of land elevated from
the sound, for residences, and as many as twenty-five summer residences have
been built upon this land bordering on the sound, and the number is increasing
each year. They are free from mosquitoes, so that the operation shows the
economy and the benefit that will result by using some means for eliminating
the mosquito-breeding pools.”

A great deal of valuable drainage work has been done in the past few years in
salt-marshes of the North Atlantic coast, and there is one instance of this on the
Pacific coast. All had the direct idea of doing away with the salt-marsh mos-
quitoes, which have unusual powers of flight and are able to proceed inland for
many miles, thus annoying the inhabitants of a large extent of country. One
of the first operations of this kind was conducted by the wealthy owners of Center
Island off the north coast of Long Island, in Long Island Sound. This work
led to the somewhat extensive work under the organization known as the North
Shore Improvement Association, referred to elsewhere, and which included
simple operations over a considerable distance along the north shore of Long
Island. These operations took place in 1902-1903. Later, some excellent work
was done at Lawrence, Long Island, and the following account, taken from the
“Report of the [New York] State Entomologist,’ Dr. E. P. Felt, for 1905,
gives an excellent idea of methods and results:

“ A most striking illustration of this work is that given by Lawrence, L. I.,
which has amply demonstrated the feasibility of controlling the salt marsh mos-
oO

DRAINAGE OF SALT MARSHES 393

quitos by relatively simple and comparatively inexpensive ditching operations.
The annual expense is only about $1000 and the total expenditure on these
operations during the past four years does not exceed $10,000, in spite of the
fact that the village is situated upon a narrow neck of land with the extensive
salt marsh areas of Jamaica bay to the north and west and large marshes south
and east, all producing in former days millions of mosquitoes which invaded
the village in swarms with every favorable breeze. Some of these marshes extend
almost to the center of the village, which is so completely surrounded that a
journey of 24 miles in almost any direction will bring one to a salt marsh. More
unfavorable conditions for mosquito control could hardly be found, and before
this work was attempted mosquitos swarmed in the village in May and remained
in numbers most of the season. The second year swarms did not invade this
territory till June, and last year it was the first of July before they appeared.
Our investigations at the end of last July showed that there were practically
no mosquitos in the center of the village. It was our privilege to sit on a piazza
one evening when conditions were most favorable for mosquito activity. Though
it was cloudy with only a little breeze and rather warm, not one appeared.
Previous to this antimosquito work it was said that one could not sit on this
piazza without being covered by netting, and the owner even went to the
trouble of making a framework to hold netting suspended over individual chairs,
so that his family and guests could sit in comfort.

“This very desirable result has been brought about by a drainage system so
planned that the entire length of all ditches will be flushed by every tide.
The general practice is to run these ditches within about 200 feet of firm ground
and sometimes closer, making them 18 to 24 inches in width, from 2 to 3 feet
deep, with main ditches here and there to tidal channels. A few headland
ditches are run into the more dangerous swampy areas in baylike extensions of
the marsh. Such ditches require no surveying and cost only 14 cents a running
foot. A little experience enables one to lay them out properly and the tides make
the determining of levels extremely easy. It was very interesting to compare
the conditions between ditched areas and undrained marshes. The former were
so free from mosquitos that one could tramp upon them with practical im-
munity from bites, though occasionally a few mosquitos were seen on one’s
person. No larve were found and in fact there were very few places where
breeding was possible. Undrained marshes presented a very different condition.
Mosquitos swarming in adjacent woodlands made driving very uncomfortable,
and when on the marshes one was attended by considerable swarms of vicious
biters, even in midday. Here and there breeding pools were literally black with
young wrigglers. This contrast between drained and undrained areas would
doubtless have been much greater were it not for the fact that our inspection
was made during such a dry time that even undrained marshes presented com-
paratively few favorable breeding places.

“Experience at Lawrence has shown that deep ditches with perpendicular
sides are far more permanent than shallow ones with sloping sides. The attempt
to slope the bottom of the ditch so that all the water will drain out invariably
results in depressions which may become dangerous breeding places and the
drainage value of the ditch itself is much lessened. Sloping sides afford oppor-
tunity for the growth of grass and sedges with the result that the ditch soon be-
comes choked with vegetation. The deep perpendicular ditches described above
remain entirely free from vegetable growth, and with a little care in removing
sods and drifting matter will last for years. Some dug four years ago were in
perfect condition last July, though the grass growing along the sides overhung
and almost hid the ditch from view in places. An area of 25 feet on each side
is easily drained by such a ditch. The village now has 40 miles of marsh drains
394 MOSQUITOES OF NORTH AMERICA

which require more or less attention from three men during most of the open
season. They keep the ditches clear, supplementing their work by judicious
oiling here and there wherever mosquito larve are abundant and then have con-
siderable time available for perfecting the system and ditching more distant
marshes. Experience showed that a considerable number of salt marsh mos-
quitos bred on that portion of Jamaica bay northwest of the village were
brought in by southwest followed by northeast winds. This led to the extension
of ditching operations some 2 miles beyond the village limits. The work in the
immediate vicinity of Lawrence was done partly at public expense assisted by
contributions from owners benefited, though it was impossible to secure the co-
operation of persons owning the distant marshes, which latter were drained
entirely at village expense. The existence of such breeding areas is an imposi-
tion upon adjacent communities and it is only a question of time before public
opinion will demand a law either compelling owners to abate such nuisances or
else provide for their suppression at public expense. The money invested by
Lawrence in this work, a total of less than $10,000, has amply justified itself in
vastly improved conditions. The village and its vicinity have been entirely freed
from breeding places, though occasionally it is subject to late summer invasions
by hordes of mosquitos when favorable winds bring them from undrained
marshes. Even this will be obviated when the value of the work becomes more
generally appreciated and then the cost of the operations will be amply returned
in increased land values, to say nothing of the satisfaction accruing from the
absence of these dangerous and annoying pests.”

On the north shore of Long Island, in Connecticut, and especially in the
vicinity of New Haven, certain simple ditching operations have been carried on
which have resulted, at a comparative small expense, in a very considerable
reduction of the mosquito supply.

In California, in connection with work carried on by the California State
Agricultural Experiment Station, in 1905, some excellent work was done under
the auspices of the Burlingame Improvement Club, in San Francisco, under the
direction of H. J. Quayle, of the Experiment Station. The territory involved
is included in the upper portion of the San Francisco peninsula, extending from
south San Francisco on the north to San Mateo on the south, a distance of about
10 miles. The salt-marsh area included consisted of a narrow strip along the
San Francisco Bay shore, varying from } to 2 miles in width, and 10 miles long.
No part of the area was continually covered with water, and it is all above the
lowest high tide. The higher tides, however, particularly those accompanying
full moon, almost completely submerge the area and result in the development
of large broods of salt-marsh mosquitoes. The operations are described as
follows:

“The actual work of control was commenced February 27th, when a gang of
men was started to work at ditching on the salt marsh. This work was started
near the Blackhawk dairy, where the marshes begin north of Burlingame, it
being the intention to work northward toward San Bruno, and make the work
permanent as far as we would be able to go in a single season. However, the
work went rapidly and the troublesome areas north of Millbrae were not so
numerous as was figured, and consequently practically the whole area was
covered during the past season.

“The ditching in the Blackhawk area consisted in connecting the pools and
areas of standing water with the tidal creeks in order that they might drain
CALIFORNIAN SALT-MARSHES 395

more rapidly and before a brood of mosquitoes would have time to develop. The
largest of these ditches were 12 inches wide and about 15 inches deep, and these
served as main channels into which smaller laterals were cut. These laterals,
and, indeed, the greater part of all of the ditches, were but one spade wide, and
one or two spades deep, according to the depth of the pool to be drained. Only
where the pools were very large and a great quantity of water to run off in a
short time was it necessary to make larger ditches. By ‘a spade’ here is meant
the common California spade, which is about 6 inches wide and 10 inches high.
The Eastern drain spade has not yet found its way to California; undoubtedly
it would be preferable for the deeper ditches in this kind of work. In addition
to the well-defined pools there was a considerable area in the Blackhawk region
which was covered with but a few inches of water for a considerable time after
each high tide, and before the rains ceased in the spring water stood over this
area almost continuously. Such areas had to be treated by making a number
of parallel ditches from 50 to 75 feet apart, in order to permit of sufficiently
rapid drainage. Rather extensive ditching was done here to make the area safe
while the rains were still continuing, while later in the season, when the rains
ceased, it would have been safe with much less ditching. Small pools that were
far from tidal creeks were made safe by filling in rather than draining. The size
of the pool, and the length of ditch necessary to drain, will determine which of
the methods is to be followed. In this way the marsh area was gone over, doing
away with all the places where larve were found or were likely to be found, for
a distance of about a mile along the bay northward, where the diked area was
met with.

“ This part of the marsh presented a more difficult problem. The dike, having
been neglected for ten or twelve years, was in poor condition, and there were
several breaks in the upper end near Millbrae. The gates were not in working
order, and their floors were too high to drain the area enclosed.

“The breaks in the dike at the upper end permitted the water to back up at
the opposite side, and this, together with the fresh water from the hills, kept
the water level, at almost high tide, over a large part of the area. To make
matters worse, the dike, just after it was built, was in effective operation just
long enough to thoroughly dry the ground and cause it to crack. These cracks,
which are 4 or 5 inches wide and 2 or 3 feet deep, still exist, forming a complete
network over most of the area. Mosquitoes were found breeding in this area,
and it was next to impossible to get over the ground, even with waders. A con-
siderable part of the area was submerged to the depth of a foot or more, thus
concealing from view the cracks and tidal creeks, which one was likely to fall
into at any step, and which made any attempt at rapid progress somewhat dis-
couraging.

“ Tt was at once evident, under these conditions, that if the area was to be con-
trolled, the dike must be either cut through in a number of places in order to
allow a freer circulation of water, or the breaks must be repaired and the gates
put in operation, and the water kept out. The latter scheme was the one fol-
lowed, because it would be possible to make the area thoroughly dry, and thus
the results would be more certain. In attempting to operate the gates we were
made to appreciate the effect of a ten or twelve years’ coating of rust on the
large screws by which the gates were manipulated. After the gates were put in
operation the breaks in the dike were repaired and the weak places strengthened.
The largest break repaired was immediately joining the upper gate. This was
30 feet wide, and by the action of the water had worn down so that at high tide
there was a depth of 10 feet of water. A double wall of sheet piling about 6 feet
apart was sunk here and the space between filled in with earth. The other breaks
were repaired by sinking a single wall of sheet piling in the center and filling in
on both sides with dirt.
396 MOSQUITOES OF NORTH AMERICA

“ After these repairs were completed the gates were operated, opened at low
tide and closed at high tide, for a week, but at the end of this time there was
still much water in the area, because the gate floors were not low enough to lower
the water level sufficiently. This made it necessary to lower the gate floors and
add an extension to the gates to reach the lower level. This being done the gates
were again operated for several days, but it was found that, due to seepage of
water through the dike in many places, hand operating would have to be kept up
almost indefinitely. It was, therefore, necessary to replace these old-style gates,
operated by hand, by automatic ones, and these were, consequently, put in at
both the upper and lower gates, and the floors lowered 32 and 20 inches respect-
ively. These gates were made to swing on an axle at the top, the lower end being
free and easily moved by the pressure of the water, so that at low tide it was
opened by the pressure of water on the inside, and closed as the water from the
high tide rose on the outside.

“This tidal creek which served as an outlet for the lower gate had become
filled in to a depth of 2 or 3 feet during the period the gate was closed, and this
was cleaned out for 300 or 400 yards toward the bay in order to drain out the
area inclosed by the dike.

“With this work done upon the dike the area inclosed by it was treated in
much the same way as that outside, except that the network of cracks, already
mentioned, had to be filled in in many places, and several of the tidal creeks
deepened. The reward for all this work came later in the season when the area
was changed from a veritable breeding ground to the safest portion of the marsh.
Indeed, this area was the key to the situation, and the excessive abundance of
mosquitoes in this particular territory was without doubt due to this extensive
breeding ground.

“Tt is appropriate to mention here the connection of this work with the
reclamation of marsh lands. This tract of 500 or 600 acres, which had been
useful only for duck-hunting, is now thoroughly dry and could be put to agri-
cultural uses at very little additional expense. Such work has already been ex-
tensively taken up on the marshes below San Mateo, and it has been found that
a good crop of grain can be raised on such land in the second year of its cultiva-
tion, It is safe to predict that all the marsh land involved in the present cam-
paign will be under cultivation before many years, and because of its proximity
to the metropolis of the coast should be very valuable.

“ Besides the marshes already mentioned, permanent control work was done
on the marsh about Millbrae and northward to San Bruno, and also some drain-
age work at Coyote Point, opposite San Mateo. The work at these places was
much the same as that already described, and further details are unnecessary.

“ Tn addition to this permanent work there was some oiling done on the marsh
where the ditching and filling work were not rapid enough to keep ahead of a
developing brood. The total amount of oil applied, however, did not exceed 400
gallons, and most of this was applied to the large tidal creeks in the reclaimed
land opposite San Mateo. The remainder was applied to pools where wrigglers
appeared after a high tide, and, the brood being checked, we had until the next
high tide in which to make the pools permanently safe.”

During 1908, 200 acres of salt-meadow land on the shore of Little Neck Bay,
between Bay City and Douglaston, Long Island, were drained by simple ditching
measures. This work was done at the instigation of the Bay Side Park Associa-
tion and the Douglaston Civic Association, both associations forming a joint
committee to promote the extermination of mosquitoes. They went to the
WORK IN NEW JERSEY 397

Board of Health of Flushing and enlisted its aid under a new law which per-
mits the Board of Health to enforce the drainage of mosquito breeding-places.
The Board of Health issued its orders to the owners of the meadow lands, com-
manding them to drain their properties within ten days. The movement was
most successful, and by October 24, 1908, 75 miles of ditches had been dug on
the Flushing meadows, and the work was still going on.

The most extensive work of this character has been undertaken by the State
of New Jersey. One of the writers (Howard), in an address on “The Recent
Progress and Present Conditions of Economic Entomology,” delivered before
the Seventh International Zoological Congress, Boston, August, 1907, made the
following statement:

“ But the work done by Smith, in New Jersey, and that which he has under
way in his large-scale campaign against the mosquitoes of that State are of
suck a unique character that they force special mention. The mosquito destruc-
tion measures carried on by English workers, and especially by those connected
with the Liverpool School of Tropical Medicine, in different parts of the tropics
controlled by England, has been large-scale work of great value. That done by
the army of occupation in Cuba was of enormous value, so far as the city of
Havana was concerned, and an assistant just returned from the Isthmian canal
zone assures me that it is possible to sit now out-of-doors of an evening upon an
unprotected veranda anywhere in the zone without being annoyed by mosquitoes,
and without danger of contracting malaria or yellow fever.

“ These are all great pieces of work, but when we consider the condition that
exists in the State of New Jersey, and the indefatigable and successful work of
Smith in the handling of the most difficult problem of the species that breed in
the salt marshes, and of his persistent and finally successful efforts to induce the
state legislature of that wealthy but extremely economical State to appropriate
a large sum of money to relieve New Jersey from its characteristically traditional
pest—we must hold up our hands in admiration.”

Chapter 134, of the Laws of 1906 for New Jersey, which went into effect on
November 1, 1906, and the passage of which was largely due to the efforts of
Doctor Smith, is here quoted :

“An Acr to provide for locating and abolishing mosquito-breeding salt-
marsh areas within the State, for assistance in dealing with certain inland breed-
ing places, and appropriating money to carry its provisions into effect.

“Be Ir Enacren by the Senate and General Assembly of the State of New
Jersey:

i L It shall be the duty of the director of the State Experiment Station, by
himself or through an executive officer to be appointed by him to carry out the
provisions of this act, to survey or cause to be surveyed all the salt-marsh areas
within the State, in such order as he may deem desirable, and to such extent as
he may deem necessary, and he shall prepare or cause to be prepared a map of
each section as surveyed, and shall indicate thereon all the mosquito-breeding
places found on every such area, together with a memorandum of the method to
be adopted in dealing with such mosquito-breeding places, and the probable cost
of abolishing the same.

“2. Tt shall be the further duty of said director, in the manner above de-
scribed, to survey, at the request of the board of health of any city, town, town-
ship, borough or village within the State, to such extent as may be necessary, any
398 MOSQUITOES OF NORTH AMERICA

fresh-water swamp or other territory suspected of breeding malarial or other
mosquitoes, within the jurisdiction of such board, and he shall prepare a map of
such suspected area, locating upon it such mosquito-breeding places as may be
discovered, and shall report upon the same as hereinafter provided in section
eight of this act. Requests as hereinbefore provided for in this section may be
made by any board of health within the State, upon its own motion, and must
be made upon the petition, in writing, of ten or more freeholders residing within
the jurisdiction of any such board.

“3. Whenever, in the course of a survey made as prescribed in section one of
this act, it is found that within the limits of any city, town, borough or village
there exist points or places where salt-marsh mosquitoes breed, it shall be the
duty of the director aforesaid, through his executive officer, to notify, in writing,
by personal service upon some officer, or member thereof, the board of health
within whose jurisdiction such breeding points or places occur, of the extent and
location of such breeding places, and such notice shall be accompanied by a copy
of the map prepared as prescribed in section one, and of the memorandum stating
the character of the work to be done and its probable cost, also therein provided
for. It shall thereupon become the duty of the said board, within twenty days
from the time at which notice is served as aforesaid, to investigate the owner-
ship, so far as ascertainable, of the territory on which the breeding places occur,
and to notify the owner or owners of such lands, if they can be found or ascer-
tained, in such manner as other notices of such boards are served, of the facts set
out in the communication from the director, and of the further fact that, under
chapter sixty-eight of the laws of one thousand eight hundred and eighty-seven,
as amended in chapter one hundred and nineteen of the laws of one thousand
nine hundred and four, any water in which mosquito larve breed is a nuisance
and subject to abatement as such. Said notice shall further contain an order
that the nuisance, consisting of mosquito-breeding pools, be abated within a
period to be stated, and which shall not be more than sixty days from the date
of said notice, failing which the board would proceed to abate, in accordance
with the act and its amendments above cited.

“4, In case any owner of salt-marsh lands on which mosquito-breeding places
occur and upon whom notice has been served as above set out, fails or neglects
to comply with the order of the board within the time limited therein, it shall
be the duty of said board to proceed to abate under the powers given in sections
thirteen and fourteen of the act and its amendments cited in the preceding
section, or, in case this is deemed inexpedient, it shall certify to the common
council or other governing body of the city, town, township, borough or village
the facts that such an order has been made and that it has not been complied
with, and it shall request such council or other governing body to provide the
money necessary to enable the board to abate such nuisance in the manner pro-
vided by law. It shall thereupon become the duty of such governing body to act
upon such certificate at its next meeting and to consider the appropriation of the
money necessary to abate the nuisance so certified. If it be decided that the
municipality has no money available for such purpose, such decision shall be
transmitted to the board of health making the certificate, which said board shall
thereupon communicate such decision forthwith to the director of the Agri-
cultural Experiment Station or his executive officer.

“5. If, in the judgment of the director aforesaid, public interests will be
served thereby, he may set aside out of the moneys appropriated by this act such
an amount as may be necessary to abate the nuisance found existing and to
abolish the mosquito-breeding places found in the municipality which has de-
clared itself without funds available as prescribed in the preceding section.
Notice that such an amount has been set aside as above described shall be given
MOSQUITO LEGISLATION 399

to the board of health within whose jurisdiction such mosquito-breeding places
are situated, and said board shall thereupon appoint some person designated by
said director or his executive officer a special inspector of said board for the sole
purpose of acting in its behalf in abating the nuisance found to be existing, and
all acts and work done to abate such nuisances and to abolish such breeding places
shall be done in the name of and on behalf of such board of health.

“6. If in the proceeding taken under section four of this act the common
council or other governing body of any municipality appropriate to the extent of
fifty per centum or more of the money required to abate the nuisance and to
abolish the mosquito-breeding places within its jurisdiction it shall become the
duty of said director of the Agricultural Experiment Station to set aside out of
the moneys herein appropriated such sum as may be necessary to complete the
work, and in all cases preference shall be given, in the assignment of moneys
herein appropriated, to those municipalities that contribute to the work and in
order of the percentage which they contribute; those contributing the highest
percentage to be in all cases preferred in order.

“%, In all cases where a municipality contributes fifty per centum or more
of the estimated cost of abolishing the breeding places for salt-marsh mosquitoes
within its jurisdiction, the work may be done by the municipality as other work
is done under its direction, and the amount set aside as provided in section six
may be paid to the treasurer or other disbursing officer of such municipality for
use in completing the work; but no payment shall be made to such treasurer or
other disbursing officer until the amount appropriated by the municipality has
been actually expended, nor until a certificate has been filed by the director or
his executive officer stating that the work already done is satisfactory and suffi-
cient to obtain the desired result, and that the arrangements made for its com-
pletion are proper and can be carried out for the sum awarded.

“8. In all investigations made under section two of this act the report to be
made to the board of health requesting the survey shall state what mosquitoes
were found in the territory complained of, whether they are local breeders or
migrants from other points, and, in the case of migrants, their probable source,
whether the territory in question is dangerous or a nuisance because of mosquito
breeding, the character of the work necessary to abate such nuisance and abolish
the breeding places, and the probable cost of the work. Said board of health
must then proceed to abolish the breeding places found under the general powers
of such boards, but if it shall appear that the necessary cost of the work shall
equal or exceed the value of the land without increasing its taxable value, such
board may apply to the director aforesaid, who may, if he deems the matter of
sufficient public interest, contribute to the cost of the necessary work, provided
that not more than fifty per centum of the amount shall be contributed in any
case, and no more than five hundred dollars in any one municipality.

“9, All moneys contributed or set aside out of the amount appropriated in
this act by the director of the Agricultural Experiment Station in accordance
with its provisions shall be paid out by the Comptroller of the State upon the
certificate of said director that all the conditions and requirements of this act
have been complied with, and in the case provided for in section five payments
shall be made to the contractor upon a statement by the person in charge of the
work, as therein prescribed, attested by said director, showing the amount due
and that the work has been completed in accordance with the specifications of his
contract.

“10, For the purpose of carrying into effect the provisions of this act, the
said director of the State Agricultural Experiment Station shall have power to
expend such amount of money, annually, as may be appropriated by the Legis-
lature; provided, that the aggregate sum appropriated for the purposes of this
400 MOSQUITOES OF NORTH AMERICA

act shall not exceed three hundred and fifty thousand dollars. The Comptroller
of the State shall draw his warrant in payment of all bills approved by the
director of the State Experiment Station, and the Treasurer of the State shall
pay all warrants so drawn to the extent of the amount appropriated by the

Legislature.
“41. This act shall take effect November first, one thousand nine hundred

and six.
“ Approved April 20, 1906.”

This law was drafted only after the most careful observations by Doctor Smith
and his assistants, and after they had made themselves perfectly familiar with
the conditions existing in the salt-marsh area in New Jersey and with the exact
life-histories of the different species of mosquitoes involved, and also after pre-
liminary drainage work had been undertaken and carried to successful con-
clusion over part of the area without the assistance of State funds.

Doctor Smith had found that three species, of approximately similar habits,
develop in the salt marshes of New Jersey and migrate inland for long dis-
tances—up to 40 miles in some instances—thus making local work on the part
of inland communities by no means perfectly efficient. Citizens’ organizations
had, for example, done excellent work in the way of destroying household and
other fresh-water breeding mosquitoes, in South Orange, Summit, and other
inland towns ; but occasional inland migrations of swarms of salt-water species
necessitated the retention of house screens and discouraged the community
workers. The salt-marsh species, studied by Doctor Smith, are Aédes cantator,
A. sollicitans, and A. teniorhynchus. The former is the more northern and
earliest, forming the bulk of the specimens on the marshes north of the Raritan
River. South of that point cantator makes an early brood only and sollicitans
is the abundant species during the rest of the season until late fall when cantator
sometimes reappears. He found that teniorhynchus is never so common as the
others and is a midsummer species. All of these species lay their eggs in the
marsh mud, and Doctor Smith found that these eggs may retain their vitality
for three years, even if repeatedly covered with water. He found that every time
a marsh becomes water-covered some eggs hatch, and if the water remains long
enough the larve reach maturity.

To prevent these mosquitoes breeding in the marshes, a system has been
developed by which the force working under the State Entomologist makes deep
narrow ditches in the salt marshes by means of special machinery. These
ditches are 10 inches wide and generally 30 inches deep, the sides being per-
pendicular. The upper twelve or eighteen inches of the ordinary salt marsh is
peat or turf, and the water drains readily from it. Below this peat is sand, mud
or clay; and at 30 inches a depth has been reached which is below high-water
mark and below the point at which vegetation is likely to start. The ditches
are placed from 50 to 200 feet apart, depending upon the character of the marsh,
but more often 200 feet apart than less.

Anticipating the ultimate passage of a State bill, work of this character was
begun on the Shrewsbury River in 1902, and at the present time the marshes
on both shores are drained in their full length. In 1903-4, the marsh areas
COST OF DRAINAGE WORK 401

belonging to the cities of Elizabeth and Newark were drained at the expense of
the cities, and, in 1906, systematic drainage work was begun on the Hackensack
marshes and continued along the shores of Middlesex and Monmouth counties.
along both shores of the Raritan River, and along the numerous small rivers and
creeks running into the Newark and Raritan bays and into the Arthur Kill.

During the year 1906, and in the preceding experimental work 4900 acres
of marsh land were drained and 710,000 feet of ditches were put in. During
the season of 1907, 10,951 acres of territory were cleaned up and 1,505,524 feet
of ditching was put in. During the season of 1908, 6669 acres of marsh land
were dealt with, and 888,650 feet of ditching was made. Out of the 1909 ap-
propriation 2672 acres of marsh were drained with 329,800 feet of ditching.
This gives a grand total of 25,192 acres of marsh land, and 3,633,974 feet of
ditches. The drained area extends from the Hackensack at Secaucus to the
mouth of Toms River on Barnegat Bay, a distance of nearly 70 miles of shore
line.

In addition there are about 10 miles on Long Beach in which experimental
work was done among the sand hills, in the pockets where the marsh mosquitoes
bred whenever there was a storm or a storm tide to fill them. Here no ditches
could be made because the layer of turf was very thin and below it was sand. Nor
could outlets be obtained to tide water without the expenditure of disproportion-
ately large sums. The smaller depressions were filled with brush held in place by
a layer of sand, and this served to gather and hold the blowing sand in high
winds, causing a complete filling after a year or two. Ditches were dug and the
larger depressions were drained to a center, where a pond varying from 6 to 15
feet square was dug three or four feet deep and a large barrel sunk into the
center. This brought the level below that of the bay and kept water permanently
present: in fact there was an appreciable rise and fall of water with the tides and
the water drained naturally to these low points. The ponds were then stocked
with killies (Fundulus sp.). Some of these pools are now three years old and
the fish have multiplied. Altogether this plan has worked well and required
little looking after.

As to the amount expended up to the end of 1910, that under the State ap-
propriations totaled $58,500. About $10,000 has been spent in addition by
various municipalities and probably $75,000 would cover what has been spent
in the entire marsh-mosquito work in New Jersey. This includes also the cost
of administration since 1905.

The estimated cost for the total salt-marsh work in the State was $350,000
and up to date the proportionate cost of the work actually done is within the
amount estimated for the whole.

The work has been largely original in its character, from the beginning of
the observations upon the habits of the insects, through the development of
special machinery and the ascertaining of the important fact that this simple
and very rapid and economic form of drainage meets the requirement by stop-
ping the breeding of these annoying insects. One of the writers (Dr. Howard)
402 MOSQUITOES OF NORTH AMERICA

has visited the marshes, has seen the excellent results of the work accomplished,
and has watched the operation of digging the ditches.

A bit of work, excellent in its results and very economical in its cost, in the
way of the drainage of an upland marsh, is described by Doctor Smith in his
report for 1908. A new normal school was about to be constructed on Montclair
Heights, and there were swampy areas nearby which a committee of the State
Board of Education considered to be dangerous as mosquito breeding-places.
Doctor Smith caused an inspection to be made early in April, and found that
there was a danger point in which not only the ordinary pool mosquitoes but
malarial mosquitoes could develop. At a cost of $250, three thousand feet of
ditching was placed or improved and all the surface water was drained to a
culvert through a railroad embankment. The heavy rains of May gave excellent
opportunity for testing the effectiveness of the work and no mosquito breeding
was found there throughout the season.

THE PRACTICAL USE OF NATURAL ENEMIES OF MOSQUITOES.

Almost no practical use has been made artificially of the natural enemies of
mosquitoes except with fish. It is true that about 1898 Mr. Albert Koebele im-
ported into Hawaii from California a large number of western salamanders
(Diemyctylus tortosus Esch.), which were liberated in the upper part of the
Makiki stream in the hope of reducing the large number of mosquitoes breeding
in small pools and in the taro fields. He kept two of these salamanders for
several weeks in an open tank and they devoured all mosquito larve that oc-
curred there; and while hundreds of the newly hatched mosquito larve could
always be observed, none of them ever reached full growth. Whether these
salamanders have increased in Hawaii and at present form an element in mos-
quito control is not recorded.

It has been suggested to breed mosquitoes of the genera Psorophora and
Megarhinus, the larve of which are extremely voracious and feed upon the
larvee of other mosquitoes; but Psorophora itself in the adult condition is an
aggressive biter, so that to breed it for predaceous purposes is hardly to be con-
sidered ; in other words, the remedy might prove worse than the disease. How-
ever, Dr. Oswaldo Goncalves Cruz, Director-General of the Board of Health in
Rio de Janeiro, told one of the writers in November, 1907, while on a visit to
Washington, that Lutzia bigotii is used in Rio to destroy the larve of the yellow-
fever mosquito. The Lutzia larve are exclusively predaceous, and this species
is introduced in regions where the yellow-fever mosquito abounds, and its larvez
destroy the other larve.

For a long time fish have been used practically on a small scale. For example:

“Tt was stated a number of years ago in Insect Life that mosquitoes were at
one time very abundant on the Riviera in South Europe, and that one of the
English residents found that they bred abundantly in water tanks, and intro-
duced carp into the tanks for the purpose of destroying the larve. It is said
that this was done with success, but the well-known food-habits of the carp seem
to indicate that there is something wrong with the story.” (Mosquitoes, p. 161.)
PRACTICAL USE OF FISH 403

In the southern United States for many years intelligent persons here and
there have introduced fish into water tanks for this purpose. Mr. E. A. Schwarz
found in 1895 that at Beeville, Texas, a little fish was used for this purpose.
The fish was called a perch, but its exact specific character is not known. Prior
to 1900, Mr. F. W. Urich, of Trinidad, wrote the Bureau of Entomology that
there is a little cyprinoid, common in that Island, which answers admirably
for the purpose. In a letter to the Bureau of Entomology Mr. J. B. Fort, of
Athens, Georgia, writes that about 1854 his father, Dr. Tomlinson Fort, living
at Milledgeville, Georgia, found that mosquitoes were breeding extensively in a
cistern owned by certain livery-stable keepers. They refused to use oil upon
their cistern, and Mr. Fort was instructed by his father to catch some small fish
from a creek nearby and place them in the cistern. About a dozen or more
small fish were so placed and in a day or so all of the larvee were destroyed. This
instance is mentioned as indicating the early use of fish on a small scale in
cisterns.

In “ Mosquitoes ” (1901), Howard recommended the practical use of stickle-
backs, top minnows (Gambusia affinis and Fundulus notatus) and the common
sunfish or pumpkinseed, and these fish, especially the top minnows and the sun-
fish, were used with success in a number of instances in small ponds. An in-
stance has been described in a letter to the Bureau of Entomology by C. T.
Anderson, of Anderson, Washington County, Florida, who wrote that he had a
spring on his place that swarmed with mosquito larve in the summer time. He
got about a dozen top minnows and put them into the spring without telling the
rest of the family. In a day or two a member of the family remarked that there
were no wrigglers in the water. Mr. Anderson verified the observation, and
after many months was able to state that no mosquito larve had been seen since.

The common goldfish proves to be an excellent mosquito feeder and during
the summer of 1901 Mr. J. Kotinsky, of the Bureau of Entomology, conducted
a series of laboratory experiments with goldfish in an aquarium. He found they
were voracious feeders on mosquito eggs, preferring them to larve. He further
noticed that the fish, after taking several larvee into the mouth, would eject
some of them. Further, he found that in a large jar containing four goldfish and
many hundreds of mosquito larvee, a few of the larve succeeded in transforming
and emerging as adult mosquitoes. The food supply was evidently in excess of
the capacity of the fish.

At an earlier date than this Mr. H. W. Henshaw, of the Biological Survey of
the United States Department of Agriculture, was staying at Fruitville, near
Oakland, California. The house was badly infested with mosquitoes. He found
the source of supply to be a lily pond about 7 x 12 feet in size and fully 3 feet
deep, which was fairly swarming with larve. He got a half dozen goldfish from
San Francisco and put them in the pond. The following day they were so badly
bloated they could hardly swim, and in a few days there was not a single larva
left. The fish bred in the pond and from the time of their introduction there
was a very marked decrease in the number of mosquitoes in that locality.

27
404 MOSQUITOES OF NORTH AMERICA

Mr. Wm. Lyman Underwood, of the Massachusetts Institute of Technology,
in “ Science ” for December 27, 1901, describes an interesting experience with
goldfish:

“ About six years ago at my home in Belmont, near Boston, Massachusetts, I
constructed a small artificial pond in which to grow water-lilies and other aquatic
plants, and also to breed, if possible, some varieties of goldfish—though the latter
object was a secondary consideration. The advisability of making this pond
had been somewhat questioned on account of its close proximity to my house and
the fact that such ponds are likely to become excellent places for the propagation
of mosquitoes. Nevertheless, the plan was carried out and the pond was stocked
with goldfish taken from natural ponds in the vicinity where they had been
living and breeding, to my personal knowledge, for a number of years.

“The aquatic garden has proved a success and the goldfish have meantime
thriven and multiplied. Moreover, no mosquitoes attributable to the pond have
appeared and I have been unable to find any larve in it, although I have searched
repeatedly and diligently for them. I have always believed that the absence of
mosquito larvee from this pond was due to the presence of the goldfish, and I
have so stated in a paper ‘ On the Drainage, Reclamation and Sanitary Improve-
ment of Certain Marsh Lands in the Vicinity of Boston’ in the Technology
Quarterly, XIV, 69 (March, 1901), as follows: ‘In the water [of this pond]
are hundreds of goldfish that feed upon the larve of mosquitoes and serve to
keep this insect pest in check.’ . . . I took from the pond a small goldfish about
three inches long and placed it in an aquarium where it could, if it would, feed
upon mosquito larve and still be under careful observation. The result was as
I had anticipated. On the first day, owing perhaps to the change of environ-
ment, and to being rather easily disturbed in its new quarters, this goldfish ate
eleven larve only, in three hours; but the next day twenty were devoured in one
hour; and as the fish became more at home the ‘ wigglers’ disappeared in short
order whenever they were dropped into the water. On one occasion twenty were
eaten in one minute, and forty-eight within five minutes. This experiment was
frequently repeated, and to see if this partiality for insect food was a character-
istic of those goldfish only which were indigenous to this locality, I experimented
with some said to have been reared in carp-ponds near Baltimore, Maryland.
The result was the same, though the appetite for mosquitoes was even more
marked with the Baltimore fish than with the others. This was probably due to
the fact that they had been in an aquarium for a long time before I secured
them, and had been deprived of this natural food. I also tried the experiment
of feeding commercially prepared ‘ goldfish food’ and mosquito larve at the
same time, and found that in such a case the goldfish invariably preferred the
larvee.

“Tt is not as generally realized as it should be that goldfish will thrive in our
natural northern waters. In my experience they can easily be bred in any
sheltered pond where the water is warm and not fed by too many cold springs,
and for many years they have been breeding naturally in many small ponds in
the vicinity of Cambridge, Massachusetts.

“ When it is once understood that these fish are useful as well as ornamental
and comparatively hardy, it is to be hoped that they will be introduced into
many small bodies of water where mosquitoes are likely to breed, and thus be
employed as a remedy for mosquitoes sometimes preferable to kerosene.”

The year 1908 in the Island of Cyprus proved to be the most malarious year
since 1885. Careful examination of conditions was made by Dr. George A.
Williamson, whose report will be found in the Journal of Tropical Medicine and
TOP MINNOWS 405

Hygiene, September 15, 1909, pages 271-272. A careful search was made in
the marshes to the north and south of Larnaca, but no breeding-places of Anoph-
eles mosquitoes were found, and subsequent search showed that the malarial
mosquitoes were breeding in the tanks and wells of private houses. Here kero-
sene could not be used, and the use of goldfish was advised. Wherever the advice
was followed, the results were perfect. One well described by Williamson was
about twenty feet deep and had a wide mouth. This well contained Anopheles
larvee in enormous numbers, and of five persons living within its immediate
neighborhood four became infected with malaria. This well, not being in use,
was filled in, but a large tank which was near it was stocked with goldfish and
all Anopheles larvee were destroyed by them.

Sir Rubert Boyce, in his recently published volume “ Mosquito or Man?”
(London, John Murray, 1909), calls attention to the fact that in Barbados,
where it is a very common practice amongst the natives to keep one or two small
goldfish in the drinking-water barrel, the native residents, in reply to the ques-
tion as to why the fish were put in the barrels, stated that they had been taught
to do so by their parents or grandparents for the reason that if a maliciously
inclined neighbor should poison the water the goldfish would die, turn up and
float on the surface, thus indicating that the water was dangerous.

An excellent discussion of the relative value of the different small fish of the
Atlantic coast-region for practical use against mosquito larve has been pub-
lished by Mr. William P. Seal, a naturalist of many years experience in handling
fishes, and the following paragraphs, taken from this article, may be considered
as authoritative. (See Scientific American Supplement, May 30, 1908, vol. 65,
no. 1692, pp. 351-352.)

“ As a destroyer of Anopheles the writer has for several years advocated the
use of Gambusia affinis, a small viviparous species of fish to be found on the
South Atlantic coast from Delaware to Florida. A still smaller species of
another genus, Heterandria formosa, is generally to be found with Gambusia
and is of the same general character. The females are about one inch long, and
the males three-quarters of an inch. Both of these species are known as top-
minnows, from their habit of being constantly at the surface, and feeding there.
The conformation of mouth, the lower jaw projecting, is evidence of their top-
feeding habits. Both of these species are to be found in great numbers in the
South in the shallow margins of lakes, ponds, and streams in the tidewater
regions wherever there is marginal grass or aquatic and semi-aquatic vegetation.
They are also to be found in shallow ditches and surface drains where the water
is not foul, even where it is but the fraction of an inch deep. In fact, if any fishes
will find their way to the remotest possible breeding places of the mosquito, it
will be these. And they are the only ones, so far as the writer’s observation goes,
that can be considered useful as destroyers of Anopheles larve.

“ Gambusia is found in the Ohio Valley as far north as southern Illinois,
where the winter climate must be at least as severe as that of the coast of New

York and New Jersey. : a8 . ;

“ Dr, Hugh M. Smith, Deputy U. 8. Fish Commissioner, informed the writer
that he had examined the stomachs of several hundreds of Gambusia in the
Chesapeake Bay and Albemarle Sound waters, and had found the contents to be

principally mosquito larve. . . .
406 MOSQUITOES OF NORTH AMERICA

“While, as has been stated, all fishes have some measure of usefulness, if
only in the way of deterrent effect, there are only a few species likely to be found
in waters in which mosquitoes breed. The most important of these are the gold
fish (introduced), several species of Fundulus (the killifishes), and allied
genera, three or four species of sunfish, and the roach or shiner and perhaps one
or two other small cyprinoids. In addition there are a few sluggish and soli-
tary species like the mud-minnow (Umbra) and the pirate perch (Aphredo-
derus). The sticklebacks have been mentioned in this connection, but the
Atlantic Coast species, and probably the entire family, are undoubtedly useless
for the purpose, being bottom feeders, living in the shallow tide pools and gutters,
hidden among plants, or under logs and sticks at the bottom, where they find an
abundance of other food.

“Tn the salt marshes there are myriads of killifishes running in and out and
over them with each tide, while countless numbers of other and smaller genera,
such as Cyprinodon and Lucania remain here at all stages of the tide. So
numerous and active are all of these, that there is no possibility of the develop-
ment of a mosquito where they have access.

“ Of the killifishes two species, Heteroditus and Diaphanous, ascend to the
furthest reaches of tide flow, but it is a question as to whether they would
prove desirable for the purpose of stocking land-locked waters, since they are a
good deal like the English sparrow, aggressive toward the more peaceable and
desirable kinds. Even Cyprinodon, which would at first thought be a valuable
small species in this respect, is viciously aggressive toward goldfish and no doubt
all other cyprinoids. It is so characteristic of all the cyprinodonts, that they can
only be kept by themselves in aquaria. They are the wolves or jackals of the
smaller species.

“The writer has come to the conclusion, after many experiments in both
tanks and ponds, that a combination of the goldfish, roach, and top-minnow
would probably prove to be more generally effective in preventing mosquito
breeding than any other. The goldfish is somewhat lethargic in habit, and is
also omnivorous, but there is no doubt that it will devour any mosquito larve
that may come in its way, or that may attract its attention. The one great
objection is that they grow too large, and the larger will eat the smaller of them.
That is one of the drawbacks to goldfish breeding. There is no danger of over-
population, but there is of the reverse. Whether or not it is the same with the
roach, they are never excessively numerous, although no doubt the most abundant
and most widely distributed of the Cyprinide. They are largely the prey of
predaceous fishes, and never approach to the numbers of the killifishes. But at
all events they are not lethargic like the goldfish, being on the contrary one of
the most active of the family, and equally at home in flowing or stagnant water.
The roach is always in motion, back and forth, and around and about, on a never-
ending patrol.

“ The top-minnows would supply the deficiences of the other two species, and
in combination they should very thoroughly populate any waters not already
stocked with predaceous kinds, and exercise an effective control. One of the
great difficulties in the case is that there are dozens of kinds of insect larve
besides those of the mosquito, and other forms of life as well, which are natural
and possibly preferred food of the fishes, thus requiring an enormous population
to devour them all.

“The larvee of gnats, midges, ephemera, and other flies and insects which
breed in the water, as well as the many small crustceans, afford a menu of
delicacies that would stagger a gourmand. The above combination of mosquito
destroyers might be supplemented by two small species of sunfish, Enneacanthus
obesus and FH. gloriosus, which live among plants and would be a check on larvee
MOSQUITO-DESTROYING FISH 407

other than the mosquito. The black-banded sunfish, M esogonistius chetodon,
would also be desirable for this purpose, if they were not so difficult to obtain in
large numbers. One or both species of Enneacanthus can be found wherever
there are aquatic plants. The above-mentioned five species in combination seem
to be the most suitable for pond protection of all those which are known to
thrive in still water, and which in any degree possess the desired qualities. As
has been stated, the killifishes would probably be found to be undesirable. In
their natural habitat, the tidal streams and great expanses of small marsh, their
efficiency is unquestioned.

“There are many places at the seashore where there are swales or hollows
filled with grasses and bushes, which in periods of rainfall become breeding
places for the mosquito, especially of Anopheles. If these places are stocked with
fish, the result is that when they dry up the fish perish, and the operation must
be repeated after each filling.

“ The writer has suggested digging holes about four feet square down through
the turf into the sand stratum in the deepest part. Two feet is usually sufficient
to secure a constant water supply where the fish can exist until the hollow is again
tain-filled. Cyprinodon and Lucania would be desirable for such places, and
they are to be found everywhere in the ditches and tide pools on the flats.

“To add variety to the treatment of the subject, it might not be amiss to
suggest that there is a fish, Anablops, inhabiting the fresh waters of South
America, which seems to be specially adapted to this purpose. To quote: ‘ These
small fishes swim at the surface of the water, feeding on insects, the eye being
divided by a horizontal partition into a lower portion for water use, and a portion
for seeing in the air.’ ”

Acting largely upon Mr. Seal’s advice, Doctor John B. Smith, the State
Entomologist of New Jersey, with Mr. Seal’s help, in November, 1905, brought
Gambusia affinis and Heterandria formosa from North Carolina into New
Jersey, which were distributed as follows: 8000 in spring and natural drainage
rivulets flowing into the ice pond at Westville, N. J., 600 in a landlocked pond
near Delanco, 600 in a mill pond between Merchantville and Evesboro, 600 in
landlocked waters near Delair, and 400 in ponds of the Aquarium Supply Co.,
at Delair. In Doctor Smith’s report for the year 1906, it was stated that the
experiment was in large part a failure. Whether it was due to the destruc-
tion of the introduced fish by black bass, pike, yellow perch and sunfish, or
whether because of other enemies, or because of their dislike to their changed
conditions they found their way during the spring rains to rivulets flowing to
the Delaware River, or whether they escaped in other ways, could not be told.
In hie report for 1907, however, Doctor Smith states that the Gambusia was
found in large numbers in Teal’s Branch of Pond Creek, a small tributary of
Delaware Bay at Highbee’s Beach, by Mr. Henry W. Fowler, of the Academy of
Natural Sciences, Philadelphia, and Messrs. H. Walker Hand and O. H. Brown.
These gentlemen found it also very abundant in New England Creek, another
tributary of Delaware Bay just north. Doctor Smith states that Mr. Seal was
inclined to claim that this finding was the result of his work in 1905, but that
Mr. Fowler doubted this conclusion since the points where found were 90 miles
distant from points of introduction.

Although the opinions of Mr. W. P. Seal, here quoted, are authoritative, it
may not be out of place at this point to quote the interesting account by F. EH.
408 MOSQUITOES OF NORTH AMERICA

Lutz and W. W. Chambers, of their observations made in the interests of the
North Shore Improvement Association of Long Island, in 1902, published in
November, 1902, by the Association :

“The value of fish in this work cannot be overestimated, although too much
dependence is often put upon them. The fact that a pond is stocked is not
conclusive evidence that it is free from larve. Often the owner points with
pride to his fine large fish, when really they are so large as to be useless. Large
fish remain in the deep water, rarely coming ‘in shore’ where the larve stay.
Then, too, large fish are apt to go after larger morsels than mosquito larve. This
was shown, for example, in one of our tests made at Cold Spring. We put three
each of goldfish, silverfish, sunfish, and mud minnows in one of the fish hatchery
tanks.

“Two days later one of the mudminnows had died and another disappeared.
We then put a large number of larve into the tank, and after the lapse of an
hour took out the fish, killed them, and examined the contents of their stomachs.
The missing mudminnow was found in a large sunfish (44 inches), but no larve
were with it.

“Concerning the best kind of fish for our purpose we should recommend
silverfish. Sticklebacks proved quite unsatisfactory for us. The ordinary
‘mummie’ or top minnow (Fundulus) of this vicinity will live in fresh water,
but is the least valuable of the promising candidates.

“Tn a series of tests, under all sorts of conditions, if we give top minnows-a
value of one (1.0), the mudminnows (umbride) rank about 1.3, sunfish (24 to
4 inches long) 1.4; while goldfish and silverfish (2 to 3 inches long) are tie at
1.5. This last is to be expected, as the goldfish are simply a highly-colored
silverfish. However, silverfish have two advantages over goldfish. First, they
only cost about one-fourth as much (a cent and a half apiece), and secondly,
just as a cur is hardier than a high-bred dog, so silverfish are hardier than
goldfish.”

It should further be here stated that Britton has experimented with a young
pike (Lucius americanus) less than an inch in length and has found it to eat
Anopheles larve with avidity. (Rept. Conn. Exp. Sta., 1904, p. 308.)

For a discussion on the transfer of several species of mosquito-eating fish from
salt water into fresh water see a note by Eugene Smith entitled “ Fundulus and
fresh water,” Science, n. s., vol. 35, no. 891, Jan. 26, 1912, pp. 144-145. Pre
vious discussion of water changes as affecting Fundulus by F. B. Sumner

occurs in Science, vol. 34, no. 887, pp. 928-931.

FISH INTRODUCED INTO HAWAIL.

In the early part of 1903, Mr. D. L. Van Dine, Entomologist of the Hawaii
Agricultural Experiment Station of the U. S. Department of Agriculture,
brought up the question of introducing top minnows into Hawaii, since his in-
vestigations of the mosquito problem in the Islands indicated that no effective
natural enemies existed there. Dr. David Starr Jordan, to whom the problem
was referred, informed Mr. Van Dine that while these fish had never been trans-
ported for such a great distance, they were extremely hardy, and that the experi-
ment would be well worth while. The cost of the experiment, however, was
prohibitive at the time, and it was not until 1904, when a Citizens’ Mosquito
Campaign Committee was organized in Honolulu, that the requisite funds were
FISH BROUGHT TO HAWAIL 409

raised. Mr. Alvin Seale, an assistant of the U. 8. Bureau of Fisheries, was
chosen to do the work, and with an advance of $500 started in July, 1905, from
Stanford University to the southern United States. He proceeded to Seabrook,
near Galveston, Texas, where he found top minnows in large numbers. They
were swarming in all the stagnant waters at sea level, as well as in various
ditches, ponds, and standing pools. Mr. Seale found that mosquitoes were very
plentiful about Seabrook, but after careful study he convinced himself that they
did not breed at all extensively in the bodies of water containing the fish, but
in temporary and artificial breeding-places such as isolated pools, tubs, and tin
cans, not accessible to fish. Dr. Jordan had advised the collection of fish of the
following genera: Mollinesia, Adinia, Gambusia, and Fundulus, all members
of the family Peeciliide, the top minnows. Mr. Seale made careful examina-
tions of the stomach contents of the minnows of the genera recommended by
Dr. Jordan. These stomach contents were found to consist largely of larve of
various insects including those of mosquitoes, of the egg masses of mosquitoes,
of minute crustacea, and of some vegetation. The fish of the genus Gambusia
were found to be the best insect feeders. Careful experiments were made, using
10-gallon milk cans, in order to determine the conditions under which the fish
could be successfully transported to Hawaii. These experiments included ob-
servations on temperature of the water and on changing the water, and it
was ascertained that the best results could be obtained by transporting them
in water of the normal temperature. The three most abundant species,
Gambusia affinis, Fundulus grandis and Mollinesia latipennis were then
collected and about 75 were placed in each can, a 20-gallon tank full of
water being taken along as a supply reservoir. Mr. Seale left Seabrook on
September 4, 1905. On the journey the fish were fed sparingly every morning
at 8 o’clock on prepared fish food, finely ground liver or hard-boiled eggs. At
half-past nine half of the water in each can was drawn off from the bottom, thus
cleaning the cans by removing uneaten food and excrement. An equal amount
of fresh water was added. At noon the cans were aérated by means of a large
bicycle pump, a sponge being tied over the end of the hose to separate the air
into fine currents. At four in the afternoon, two gallons of water were drawn
off from the bottom and two gallons of fresh water put in, and the aération was
repeated just before bedtime. Careful tests of water at each place of changing
were made by experimenting with two fish. At El Paso, Texas, there was so
much alkali in the new water that the fish were killed; at Los Angeles and at
San Francisco, the water was good. Twelve fish died between Galveston and
San Francisco, and 15 between San Francisco and Honolulu. Honolulu was
reached on September 15, 1905, with a loss of only 27 out of approximately 450
fish. On arrival the fish were placed in the four breeding-ponds prepared for
them at Moanalua near Honolulu. The fish thrived in all of the ponds almost
equally well. They were protected by screens from predatory fish and from
being carried out to sea by freshets. In an official bulletin, issued July 25, 1907,
Mr. Van Dine reported that the fish had multiplied rapidly and that from the
few hundred introduced several hundred thousand had been bred and dis-
410 MOSQUITOES OF NORTH AMERICA

tributed. They had proved very effective destroyers of mosquito larve and also
of mosquito egg-masses. Later advices show that the good work is continuing
and that the experiment has been a great success.

FISHES IN THE WEST INDIES.

Girardinus peciloides, a small top minnow, occurs very abundantly in Bar-
bados, where it is known by the popular name “ Millions.” This fish is very
small in size, the full-grown females measuring about 1} inches in length, while
the male is much smaller. The female is dull in color, without conspicuous
markings, while the male is marked with irregular red splotches and has a
circular dark spot on each side. The fish is a rapid breeder and thrives and
multiplies in captivity, in water tanks, reservoirs and fountains, and garden
tubs in which aquatic plants are kept. They are much used in this way, both in
the towns and on the estates, to reduce the annoyance of mosquitoes. In 1905
this fish was introduced by the Imperial Department of Agriculture of the
British West Indies from Barbados into St. Kitts, Nevis and Antigua. In 1906
it was introduced into Jamaica, and in 1908 into St. Vincent, St. Lucia and the
city of Guayaquil in Eucador. An account of these introductions is given in a
pamphlet entitled “ Millions and Mosquitos,” by H. A. Ballou, issued in 1908
by the Imperial Department of Agriculture of the West Indies (No. 55). In
August, 1905, a number of fish were sent to Antigua in a kerosene tin. They
arrived in good condition and were kept in a tank at the Botanic Station until
they had sufficiently increased to be distributed. They were liberated in several
ponds and streams and increased so rapidly that the Country Board of Health
undertook the work of stocking all the ponds and streams of the Island. Three
years after the first introduction all of the more or less permanent water of
Antigua had been stocked, and Mr. Ballou states that many planters and others
have commented on the evident abatement of the mosquito nuisance in many
localities. At St. Kitts, the introduction was equally successful, but the local
government did not take up the distribution of the fish as in Antigua. In
Jamaica they were established with good results. Millions may be fed in
captivity on mosquito eggs and larve, on raw beef or hard-boiled eggs, upon
small insects of any kind, and even upon cornmeal. They are readily trans-
ported short distances in a kerosene tin, with no other preparation than a wire
netting arranged near the top to prevent the fish from being thrown out if the
water is splashed about.

The success of these West Indian experiments attracted the attention of the
sanitary authorities at the Isthmus of Panama, and some “ millions ” were in-
troduced into the Isthmus for the purpose of eating mosquito larve. Similar,
and perhaps also the same species, already occurred on the Isthmus, but, never-
theless, the experiment was an interesting one. Under date of March 12, 1910,
Colonel Gorgas, Chief Sanitary Officer, wrote one of us, as follows:

“ Yours of March 1st is acknowledged. We brought over some of the minnows
from the Barbados and have been breeding them here for the last year. We have
also found some Girardinus peciloides in the ponds and streams here that do
AFRICAN FISH 411

very well as eaters of larvae. I look with favor upon using these fish wherever
wecan. Itsaves considerable expense. When we get these fish in a suitable pond
all we have to do is to keep the edges clean from grass and refuse so that the

fish can get at them.”

It does not appear that the “ millions ” have been tested on a large scale in the
Canal Zone, and perhaps with the large scale topographic changes in progress
there this is impossible. Recently J. A. M. Vipan has shown that no far-reach-
ing results can be expected from the introduction of Girardinus peciloides on
the American mainland. Vipan states that the extraordinary abundance of
these fish in the island of Barbados is due to the fact that no other fresh-water
fish exist there to keep them in check. He points out that furthermore Girar-
dinus peciloides is already indigenous in some of the regions in which its in-
troduction has been attempted and that other species of fish exist there which
are equally efficient destroyers of mosquito larve. The reason why these fish
do not multiply in the same degree as in the small islands of the Antilles is that
they are preyed upon by other species of fish.

A BRAZILIAN FISH.

Excellent results are obtained in Rio de Janeiro, Brazil, by the use of a small
fish known as the “barrigudo” (Girardinus caudimaculatus) which feed on
the larve of mosquitoes most voraciously. In the great prophylactic work
carried on in that city under the public health service, it is placed in tanks and
other receptacles where it is impossible to use petroleum.

AN AFRICAN FISH.

Mr. J. Vosseler, in an article entitled “ Fische als Moskito-Vertilger,” pub-
lished in “ Der Pflanzer, Ratgeber fiir Tropische Landwirtschaft,” for June 13,
1908, vol. 4, No. 8, pp. 118-127, gives an interesting account of some experi-
ments with mosquito-feeding fishes in German Hast Africa. He brings out
the point that on account of the great physical and chemical differences in
the water inhabited by mosquito larve the selection of suitable species of fish is
made difficult by several restrictions. He states that the shallow shores of rivers
or large lakes can be excluded from consideration, since the young of most
species of fish living there frequent the shores in shoals, and prey upon the
various forms of animal life, mosquito larve included. Many water supplies,
however, contain salt and other chemicals, and are polluted from various sources,
even from the excrement of game coming to drink, while temporary collections,
such as pools, puddles, irrigation ditches, contain turbulent muddy water. The
level of the water in these different conditions is very variable, and the tem-
perature of the water goes through great variations within a single day; often
at the midday heat rising above the limit which most fishes can stand. A fish
which would withstand all these conditions would be very exceptional. In
considering the question of fish introduction, the capability of the species for
acclimatization, its power of enduring long transportation, and its ability to
multiply rapidly, even under adverse conditions, are of vital importance to
412 MOSQUITOES OF NORTH AMERICA

success. In his travels through southern Oran (Algeria) in 1892, Mr. Vosseler
found a widely distributed species occurring in thousands, not only in the springs
of salt or magnesia water in the oases and in the irrigation ditches, but also
in the highly polluted, badly smelling pools used to water camels, and in which
300 to 400 camels often waded in one day. He found the same species after-
ward in pure, fresh water, in hot springs, and in brackish water. He also found
that it inhabits the subterraneous waters of the desert and is probably brought
up by the boring of artesian wells. One of the officers of the garrison situated
in the midst of a salt basin without outlet pointed out to Mr. Vosseler that this
little fish eats mosquito larve, which explained the comparative absence of
mosquitoes in that locality. Mr. Vosseler attempted the introduction of these
fish into Germany and succeeded very well, in spite of inadequate preparation.
They began to lay eggs within a week of their arrival and became accustomed
to any animal food. They always prefer mosquito larve and small crustaceans.
The fish in question is Cyprinodon calaritanus. The female is 8 cm. long and the
male 5cm. The eggs are attached singly to water plants or stones at the rate
of one or two a day. Mr. Vosseler states that the excellent qualifications of the
species are shared by other members of the same family, and in German East
Africa at least two genera and five species are known to occur.

MR. THIBAULT’S OBSERVATIONS.

In considering the normal relation between mosquitoes and fish, Mr. James
K. Thibault, Jr., Scott, Arkansas, in a recent communication presents his views
and gives an interesting instance of mosquitoes breeding in the presence of fish,
which he considers typical of conditions in some localities :

“ Personally I do not think that mosquitoes ever breed in the presence of fish
if the water is open, allowing the fish free access to the larve, yet it is a matter
of common observation that under certain favorable circumstances some species
do breed regularly in streams where fish are abundant. Yet even where con-
ditions are favorable only a very few species seem to take advantage of it. So
far as my own observations go the only mosquitoes that regularly do so in this
locality are Anopheles quadrimaculatus and Culex abominator.

“ Conditions are favorable where the surface of the water becomes carpeted
with aquatic vegetation, which restrains the fish in their movements, yet allows
ample room and protection for the larve: of the above-named species. There is
a certain deep, slowly running bayou here that is the main breeding place for
quadrimaculatus and abominator at present while two years ago not a larva
could be found there at all. The explanation is simple and may be given as a
typical example of its kind. Two years ago launches passed through this bayou
daily, and all logs and drift were removed as soon as found, so that the water had
free passage and the pond weeds found no foothold, except very near the banks
where they were completely destroyed by stock. After the launches stopped pass-
ing through this bayou, logs soon accumulated and the pond weeds immediately
took possession, so that throughout the present season quadrimaculatus and
abominator have bred continuously and abundantly in this bayou.

“ It must be noted in passing that the larve, pupex, and freshly emerged adults
bred in such a location are invariably bright grassy green in color, which gives
them additional advantage of the fishes. This is not the case with larvae,
etc., found in other places.”
EUCALYPTUS 413

ALLEGED DETERRENT TREES AND PLANTS.

There are many statements scattered through the literature that there are
certain trees and plants in the neighborhood of which mosquitoes are never
found. Notable among these are the Eucalyptus trees and the castor bean plant.
Of recent years there have been many newspaper notes about other plants, and in
the Southern States the chinaberry tree is said to be repellant.

EUCALYPTUS.

The statement has often been made that the planting of Hucalyptus trees in
malarial regions will drive away malaria. This idea had become rather firmly
grounded before the discovery of the carriage of malaria by mosquitoes. It has
been said, for example, that the planting of Eucalyptus trees in the Roman
Campagna was followed by a noted improvement in the malarial conditions.
Eucalyptus oil has been used to keep mosquitoes from biting. Mr. Alvah A.
Eaton, of California, wrote to the Bureau of Entomology, Department of Agri-
culture, in 1893, that, in his opinion, where the blue gum grows no other remedy
against mosquitoes need be sought for. He further stated that, no matter how
plentiful mosquitoes may be, a few twigs or leaves laid on the pillow at night will
secure immunity. Another correspondent of the Bureau, Mr. W. A. Sanders,
wrote from California that he had planted Eucalyptus trees about his house 19
years previously and that they had reached a height of 140 feet. According to
his statement an irrigating ditch ran through the grove, but there was never a
single mosquito larva in the grove, although on both sides of the grove larve
were plentiful. On the other hand, Dr. A. Dugés, of Guanajuato, Mexico, wrote
the Chief of the Bureau on September 8, 1900:

“T have received your very interesting study of the mosquitoes of the United
States and thank you greatly for it. At the end of the book you speak of the
utility of Hucalyptus for driving away insects. I have had some experience with
these trees. The fresh leaves placed upon the pillow will attract mosquitoes.
Thinking that the mosquitoes loved this plant I had placed the branches further
away but without result. I have burned the leaves in my chamber, and the
cursed beasts have resisted the smoke.”

Eucalyptus trees of many species are now grown generally all through Cali-
fornia, and the idea that they drive away mosquitoes must be abandoned. Mr.
H. J. Quayle, in Bulletin 178 of the California Agricultural Experiment Sta-
tion, states that in the Burlingame section, not far from San Francisco, all of the
avenues are lined with Hucalyptus trees, and mosquitoes are most numerous
where these trees are most abundant. In 1901 he captured a pint cup of mos-
quitoes immediately under Hucalyptus trees. Coyote Point is covered with
Eucalyptus trees, yet the construction of a hotel on the point was abandoned on
account of the abundance of mosquitoes.

Edmond and Etienne Sergent, in their anti-malarial work in Algeria, had
occasion to study the question of Hucalyptus, and published their results, to-
gether with the results of their observations and experiments upon certain other
plants supposed to be deterrent to mosquitoes, in the Comptes rendus des Séances
de la Société de Biologie, November 14, 1903. With regard to Hucalyptus they
414 MOSQUITOES OF NORTH AMERICA

show that the railway station of Ouled-Rahmoun, formerly greatly troubled by
mosquitoes, was visited by them much less frequently after the cutting down of
great Hucalyptus trees which surrounded it. The station of Ighzer-Amokran,
which is isolated in the middle of a desert plain, is surrounded by a little grove
of Hucalyptus. Before the windows and doors were screened the rooms were
visited every evening by quantities of Anopheles. The traveling Kabyles who
stopped at this station would never sleep at midday under the foliage of the
Eucalyptus, for they said mosquitoes always came down on them. They went
under the oiives where they were never bitten.

RICINUS AND PAPAYA.

During the winter of 1901 a great deal was said in the newspapers about
the planting of castor oil plant (Ricinus communis) to ward off mosquitoes.
These notes were mainly based upon a consular report from Capt. E. H.
Plumacher, U. S. Consul at Maracaibo, Venezuela. In this report Capt.
Plumacher stated that his residence is surrounded by plantain and banana trees
and that he was troubled in the past by a great number of mosquitoes which
gathered in these trees. Following the example of old settlers, he planted castor
seeds which grew up in profusion, with the result that no mosquitoes were to be
found among the trees, although he kept the ground well irrigated. Capt.
Plumacher came to Washington the following year and called on one of the
writers April 18, 1901, bringing with him the seed of the particular variety of
the castor oil plant with which he had noted the result above stated. The seeds
were planted upon the U. 8. Department of Agriculture grounds in Washington
and observations indicated that mosquitoes were not at all deterred by the plants.

Some of the Venezuela seeds brought by Capt. Plumacher were sent to Mr. J.
Turner Brakeley, of Hornerstown, New Jersey. He planted them in the early
summer of 1901, and later in the summer observations were made with the
result that mosquitoes were found both on these Venezuelan plants and on other
castor oil plants. Mr. Brakeley wrote: “The castor oil plant is no good as a
skeetonal protection in New Jersey. It may be a protection against the Vene-
zuela mosquito, but it is no good where the blood pirates of New Jersey are
concerned.” In a report sent in from Progreso, Yucatan, September 17, 1903,
U.S. Consul Thompson makes the following statement:

“The belief is current among the natives of Yucatan that a few castor oil
plants growing in or near a dwelling will protect the inmates from mosquitoes
and certain other noxious insects peculiar to Yucatan. This belief has been to a
certain extent confirmed upon experiment by me personally. My dwelling at
one time seemed to be peculiarly acceptable to mosquitoes. I planted a row of
castor oil plants around the court yard and in a short time the mosquito was as
tare as he was formerly a frequent visitor. My plants were destroyed by the
cyclone and now the mosquitoes are as abundant as formerly.”

Giles published a letter sent to the “ Pioneer,” an Indian journal, in 1901,
in which the correspondent states that he had seen a recommendation of the
castor oil plant as a deterrent for mosquitoes, and in consequence had six plants
placed in pots in his room, The result was that the plants were thickly covered
OCIMUM 415

by the insects, which seemed “to be actually invigorated by the apparently
stimulating effect of their new quarters.”

The Sergents, in Algeria, experimented both with the castor oil plant (Ricinus
communis) and with papaya or pawpaw (Carica papaya) on account of the
reputation that these plants had as deterrents against mosquitoes. A pawpaw
about 90 cm. high and in good condition was enclosed in a mosquito bar of tulle,
oblong in form, with its axis directed perpendicularly to the window from which
the light came. In the end of the bar nearest the window they suspended a
raisin grape, as food for the mosquitoes, and a little vessel of water. Then at
the opposite end of the bar they put in four females of Anopheles maculipennis
and four females of Culex pipiens. They wished to see if the instinct which
attracts the mosquitoes toward the light and towards an apparent way of escap-
ing, and on the other hand the need of nourishment and water, would induce the
mosquitoes to pass the middle portion of the bar which was entirely filled with
large leaves of the pawpaw. At the end of four minutes one Anopheles and one
Culex had passed from one end of the bar to the other; at the end of ten minutes
another Anopheles and two Culex were seen to alight upon the pawpaw leaves
and they remained there many hours. The mosquito bar was left in place for
eight days. During this period the mosquitoes moved about freely and rested
frequently upon the leaves and branches, sometimes for hours.

An experiment exactly similar was carried on at the same time with Ricinus
communis, with the same results. When these experiments were concluded at
the end of eight days one Anopheles and one Culex were found dead in the paw-
paw mosquito bar, and in the Ricinus bar also one Anopheles and one Culez.
But in similar cages in another room during the same time with Carica and
Ricinus plants absent, six Anopheles out of twenty had died, and nine Culex
out of twenty-eight. The authors concluded that pawpaw and castor oil plants
are powerless against mosquitoes.

OCIMUM.

Another plant which is said to act as a deterrent is a lavender known as Oci-
mum viride, a perennial which grows from 3 to 6 feet in height and occurs from
Senegambia southwards to Angola. Mr. A. E. Shipley in the Tropical Agri-
culturist of February 2, 1903, pp. 555-556, states that Major Burdon, resident
of the Nupe Province, northern Nigeria, had given him the following account
of the plant:

“ A fragment of what turns out to be Ocimum viride was given me in August
last at Lokoja, Northern Nigeria, by Capt. H. D. Larymore, C. M. G., R. A.,
Resident of the Kabba Province. Capt. Larymore’s notice had been drawn to the

lant by a native living in a low-lying part of the native town at Lokoja, who had
told him that the natives suffered very little from the swarms of mosquitoes
which existed in that part, as they protected themselves from them by the use of
this plant.

ne bapt. Larymore made inquiries and obtained a few specimens of the plant,
which grows wild, though not very abundantly, in the neighbourhood of Lokoja.
These specimens he planted in pots and boxes and kept in and about his house.
The specimens I saw were about the size of a geranium.
416 MOSQUITOES OF NORTH AMERICA

“He informed me that the presence of one of these plants in a room un-
doubtedly drove the mosquitoes out, and that by placing three or four of the
plants round his bed at night he was able to sleep unmolested without using
a mosquito net. This is very strong testimony to the efficacy of the plant, for
the Louse in which Capt. Larymore was living is, as I had cause to know well in
former years, infested with mosquitoes.”

Mr. Shipley further states that E. M. Holmes, in “ Notes on the Medicinal
Plants of Liberia,” records that when chewed or rubbed the leaves of O. viride
give off a strong odor of lemon thyme, and mentions that Dr. Roberts, of Liberia,
entirely substituted the use of the plant for that of quinine in cases of fever of
all kinds, giving it in the form of an infusion.

Mr. Shipley’s article in the Tropical Agriculturist was reprinted in the
British Medical Journal and was quoted in many other periodicals and in conse-
quence many requests for seeds of Ocimum viride were received at the Royal
Botanical Gardens at Kew from many parts of the world. About this time a
report was received from Dr. W. T. Prout, at Freetown, Sierra Leone, and was
published by Sir William Thistelton-Dyer in the London Times for July 27,
1903, and in Nature, July 30,1903. Dr. Prout’s report included an account of
experiments made with the basil plant in relation to its supposed effect upon
mosquitoes and he states that these appear “to dispose conclusively of the
plants possessing any real protective value.” He showed that growing plants
have little or no effect in driving away mosquitoes, and are not to be relied upon
as a substitute for the mosquito-net. He showed further that fresh basil leaves
have no prejudicial effect upon mosquitoes when placed in close contact with
them, and further that while the fumes of burnt basil leaves have a stupefying
and eventually a destructive effect on mosquitoes it is necessary, in order to
_ produce this effect, to bring about a saturation of the air which renders it im-
possible for individuals to remain in the room. He thinks that cones made of
powdered basil would, when burned, have the effect of driving mosquitoes away,
and that the plant to that extent might be found useful. Goeldi, in Brazil, has
experimented with Ocimum minimum without the slightest beneficial result.

CHINABERRY TREES.

In spite of the statement that the chinaberry tree will protect against mos-
quitoes, observations have failed to show the truth of the statement, and in
mosquito regions people are quite as liable to be bitten while sitting under a
chinaberry tree as under any other tree. Nevertheless there is an observation
upon record which makes further experiments desirable. In the Public Health
Reports, volume xxi, No. 44, Nov. 1, 1901, Dr. G. M. Corput, Assistant Surgeon
U. S. Marine Hospital Service, gave the results of experiments, conducted by
tempting the mosquitoes to oviposit with cans of water hung in the branches of
a variety of trees, to determine if any of them had a repellant effect. He found
that in the can hung in the chinaberry bush there were no mosquito larve at any
time, although larve were found in all of the other cans.
AQUATIC PLANTS 417

A number of other plants have been mentioned from time to time in the news-
papers, some of them in a sensational manner. The New York papers, for
example, in the summer of 1906, contained numerous notices of the so-called
Phu-lo plant introduced from the Tonquin country in China by Baron de
Taillac. This plant was said to be valuable as a fodder for cattle, and to drive
away mosquitoes. An effort was made to determine the plant and Mr. W. E.
Safford searched the literature of oriental economic botany without finding any-
thing corresponding to it. He found that in the East Indies there is a Ver-
bascum or mullein called Phul, the seeds of which are supposed to be narcotic,
and the leaves used like those of tobacco. The leaves of this plant, although not
good for general forage, are eaten by camels and goats. Assuming that this is
the plant mentioned by the newspapers, there is nothing in the economic litera-
ture concerning its use as a mosquito deterrent.

PEAT.

An article in the London Times in 1908, written by an anonymous corre-
spondent, refers to the absence of mosquitoes in swamps and marshes with peat.
The writer says: “ Given marshy lands and no peat, mosquitoes abound; given
marshy land and peat, there are none.” This article was answered by Mr. F. V.
Theobald in Nature, October 15, 1908, pp. 607-608. Mr. Theobald showed that
he had found Anopheles nigripes and Anopheles bifurcatus breeding in the
water of peat cuttings in Wales and Somerset and on the far-famed Wicken Fen
numbers of Aédes cantans. He stated that mosquitoes are often very abundant
in the fens, even where the peat is dug. Besides the species above mentioned he
has found Anopheles maculipennis and Culiseta annulata in peaty water and
near peat piles in northern Wales.

WATER PLANTS.

Ordinary pools of stagnant water are often the source of thousands of mos-
quitoes, the larvee breeding with the greatest facility in such water. To some
persons the presence of alge and certain low forms of aquatic vegetation is
evidence of the stagnation of the water, and an algal scum is frequently asso-
ciated with the idea of mosquitoes in one’s mind. But, it is perfectly plain that
where the water covering of aquatic vegetation becomes extremely dense and
complete mosquitoes can not breed, since there is no opportunity for the larve to
come to the surface to breathe. It has often been a matter of surprise that
mosquitoes are not more numerous in Holland, where the country is traversed
by canals and dykes. Mosquitoes breed there, as elsewhere, in ponds and in
chance receptacles of water, but it is said that no larve are present in the water
of the canals. It is explained that this is so constantly agitated by the passage
of boats and by the wind that mosquitoes can not breed there, and that in the
smaller ditches and canals the surface of the water becomes so completely covered
with a continuous layer of minute aquatic vegetation early in the summer that
there is no opportunity for the extensive breeding of mosquitoes.
418 MOSQUITOES OF NORTH AMERICA

A short statement regarding the practical use of water plants occurs on pp. 1
and 2 of the 4th volume of Theobald’s Monograph of the Culicide of the World.
This statement may be quoted:

“Major Adie, I. M. 8. (‘ Ind. Med. Gaz., xxxix, June, No. 6, 1904), brings
considerable evidence to bear on the benefit of Lemna minor as a means of keep-
ing mosquitoes from laying their eggs on water. He shows that tanks covered
with this green flat weed never contain larve of Culicide, whilst others at the
same time of year are full of them.

“ As a test he ‘cleared certain areas near the banks of all Lemna and en-
closed them with light floating structures, which were fixed enough to resist the
winds—in fact made experimental pools. I was pleased,’ he says, ‘ to find in due
time plenty of Anopheles larve: in these pools. This seemed to prove that Lemna
acts as a mechanical obstruction to the process of egg-laying, and a very obvious
method of prevention occurred tome. Why not deliberately promote the growth
of Lemna minor in all unavoidable collections of water to prevent the propaga-
tion of mosquitoes ?”

“ This same green plant grows freely in England, and I have noticed a similar
occurrence here. A pond close to my house was frequented by numbers of the
larvee of Anopheles bifurcatus and A. maculipennis every year. Two years ago
its surface became smothered with Lemna minor, Linn., and Lemna arrhiza,
Linn., no Anopheline larve could then be found. As this was the only breeding
ground near, both species have practically died out.

“This small yet widely distributed genus of floating plants evidently has a
very marked effect upon the frequence of Culicid larve in natural and artificial
collections of water.

“The little Lemna arrhiza, or the Rootless Duckweed, occurs in Asia, Africa,
South America and Europe, and apparently has the same effect as the larger
ZL. minor.”

An early suggestion as to the practical use of water plants occurs in Mr.
William Beutenmiiller’s essay on the “ Destruction of the Mosquito and House
Fly,” published in Dragon-Flies vs. Mosquitoes (The Lamborn Prize Essays,
New York, 1890). Mr. Beutenmiiller states that Mr. L. P. Gratacap, of the
American Museum of Natural History, suggested the increase of fresh-water
algee as deterring the progress of mosquito larve in the water and as effecting
their destruction before they can rise to the surface of the water to breathe. Mr.
Beutenmiiller, considering the suggestion important, stated that he believed
“that the vast numbers of the fronds of Oscillatoria in the Central Park lakes
[in New York City] have had a deterrent effect upon the propagation of mos-
quitoes in those localities. The requisition here is a largely disseminated mass of
alge, which, in such rod-like forms as Oscillatoria, will float through the water
and by its intermixed and diffused stipes embarrass the development and move-
ments of the mosquito larve.” In fact, mosquito larve are frequently found in
the presence of alge and it is well known that Anopheles larvex thrive where alge
are abundant. One of us (Knab) has found larve of Culex tarsalis abundant
among a dense growth of alge and larve of Uranotenia under the same cir-
cumstances.

The value of duckweeds was considered by Dr. H. P. Johnson in an appendix
to Smith’s New Jersey Report for 1902, and by virtue of the actual small-scale
experiment tried, these observations are printed in full:
DUCK-WEEDS 419

“ While most forms of aquatic vegetation promote the breeding of mosquitoes,
the Lemnacea, or duckweeds, are unfavorable, and in many waters almost or
even wholly prevent it. These tiny plants consist merely of a floating frond,
resembling a miniature lily pad. It is circular or more frequently lobated and
three to six millimeters in diameter. From the under surface hang one or more
roots, which never fasten in the soil, but derive their nourishment from the
water. Its reproduction, mainly by division of the frond, is so rapid that in a
short time (usually before July 1st) it completely mantles quiet waters, notably
sheltered ponds and ditches, without perceptible flow. Its extraordinary abun-
dance, often covering whole acres of shallow water, makes it an efficient pro-
tection from mosquito breeding. Wherever this plant forms a complete covering
no larve have been found. Such places should never be treated with oil, for
nature has provided a far more lasting and equally effective protection. It is
probably impossible for a mosquito to lay her eggs on lemna-covered water.
Even should larve wander in from adjacent waters, they would be unable to
reach the surface for air, and would thus soon become asphyxiated. Larve of
Culex pungens, injected by means of a pipette beneath the lemna in the jar
.... died in less than an hour. Where the lemna mantle is not complete, but
presents interspaces of open water, larve of both Culex and Anopheles will
usually be found in small numbers only, for lemna waters are apt to harbor the
various predaceous water bugs in great numbers.”

To have any effect, the covering of Lemna must be complete and thick. The
most abundant breeding-place of Culex salinarius known to us is a large marsh
near Chesapeake Beach, Maryland, which was observed by one of us (Dyar)
to be well covered with Lemna in June, but at the time no deterrent effect had
been produced upon the breeding of the mosquitoes. Culex abominator, a
locally abundant species in the lower Mississippi Valley, according to the obser-
vations of J. K. Thibault, Jr., and others, breeds by preference in permanent
bodies of water thickly overgrown with duckweed. Recently it has been deter-
mined that this mosquito actually deposits its eggs upon the aquatic plants.
Anopheles larve would obviously be much more easily deterred by Lemna than
Culex larve, on account of their different habits of feeding. The Lemna, how-
ever, usually only acquires a luxuriant growth late in the summer, when the
breeding of mosquitoes is largely over, and also it never occurs abundantly in
temporary or semi-temporary pools which are the favorite breeding-places of
most of our mosquitoes.

Recent observations by Charles A. Bentley, at Bombay, India, show that duck-
weeds may be successfully employed under certain conditions, at least in the
tropics, but that their value has been very much overestimated. We quote his
remarks:

“The presence of water-weed in a tank, well or cistern is often a source of
danger, forming as it does an excellent shelter for mosquito larve. Some water
plants, notably duck-weed or Lemna and Azolla have been suggested as being
useful in preventing the breeding of mosquitoes. These suggestions do not
appear to have been based upon careful observation and experiment. In my
experience these plants are of little or no value in preventing the presence of
mosquito larve. But there is a weed which I have met with in Bombay and else-
where which under certain circumstances appears to be a useful preventive of
mosquito larve. This plant is the rootless duck-weed or Wolffia arhiza. It takes
the form of small bright green round grains without stem, roots or leaves. These

28
420 MOSQUITOES OF NORTH AMERICA

grains float on the surface of the water just like a scum of bright green seeds.
When it is growing in large amount so as to form a continuous layer on the top
of the water no mosquito larve can live and pools and tanks covered in this way
will be found quite free from larva. Anopheles larve placed in a bowl of water
covered with a layer of Wolffia arhiza immediately assume an almost vertical
position, hanging head downwards in a manner quite unnatural to them. After
a short interval they sink to the bottom dead. The larger the larvee the more
quickly they die, as young larve can pass their tails between the plant grains and
so get access to the air. Culex larve and Stegomyia larve are also destroyed,
but the latter live for several hours in the weed-covered water. Where the con-
tinuity of the layer of Wolffia arhiza is broken by the presence of grass or reeds
or large leaved weeds, mosquito larve are enabled to exist without difficulty, and
it would appear therefore that before this plant could be used with success as a
protection for tanks, the latter would have to be cleared of other growths. The
round tank at the Mint which is usually covered with a good growth of Wolffia
arhiza is free of mosquito larve, and so is the Nakhoda tank and several pools
near Parel.”

Recently the idea of cultivating such aquatic plants with practical ends in
view in regard to anti-mosquito work has been taken up in German colonies in
Africa. It is stated in the “ Monthly Consular and Trade Reports,” of the
Bureau of Manufactures, U. 8S. Department of Commerce and Labor, for
March, 1909, in a dispatch from Consul-General Richard Guenther, of Frank-
fort, that the director of fisheries at Biebrich, Dr. Bartmann, had found a duck-
weed-like plant of the genus Azolla to be especially well adapted to this use; and
at the instance of Dr. Bartmann experiments were made at the malaria station at
Wilhelmshaven. It was found that in a short time the growth of the plant
covered the experimental waters with a layer of about 6 centimeters ; this suffo-
cated all the mosquito larve below and prevented the parent insects from de-
positing eggs in the water. Consul-General Guenther states that several years
ago Director Bartmann communicated this method to the Mosquito-Destroying
Commission at Eltville on the Rhine, which has used it repeatedly with good
success.

One of the officials who took part in the question of mosquito extermination in
the German African colonies was far from enthusiastic regarding the practical
use of this plant, although it had been advertised on all sides in Europe and in
this country. In his opinion, it may possibly be of some use in special places,
but, so far as experiments have gone, it appears that the plants will not grow in
dense or even moderate shade and therefore they are of no use in the tropical
forests where there are large and small pools of water, the very places where it is
most needed. Moreover, the Azolla plants do not stand any great cold nor do
they stand short seasons, for which reasons their use is excluded from highland
and northern regions. Further, they will not grow in brackish water and can
not be utilized along sea-coasts, and, still further, in case of drouth they all
perish and thus necessitate the restocking of pools and swamps that have
been dry.

So positive were the statements published in the United States, as to the
value of the Azolla plant to prevent mosquito-breeding, that one species was
ORGANIZATION FOR MOSQUITO CONTROL 421

imported from Europe into the United States. Dr. John B. Smith, of New
Jersey, investigated the plant in its natural habitat in Holland and also experi-
mented with the introduced plants in New Jersey. His investigations, which
need not be quoted here, demonstrated that for a number of reasons, which have
been already indicated in the foregoing discussion, Azolla has no practical value.

ORGANIZATION FOR COMMUNITY WORK.

While in a large measure it is true that every individual householder prac-
tically breeds upon his own premises the majority of the mosquitoes that bother
him, still in a closely built city those bred by one’s neighbors must be taken into
consideration. In isolated country houses the character of the region about must
be considered by the individual who concerns himself with this work, so that
here also some sort of an organization is desirable, and even frequently necessary,
as in cases where swamp lands are to be drained or where occasional invasions
of migratory species, such as Aédes sollicitans, are to be feared. The control of
all sources of mosquito supply in case of fresh water or brackish swamp land is
usually too great a task for the individual, although on the large estates of great
proprietors such work has been done at individual expense. In any sort of com-
munity, however, organization is desirable, not only to carry out the actual work
but to produce and to emphasize a universal sentiment in favor of the mosquito
crusade—a sentiment so strong and so general that every individual will cheer-
fully take part in the work. The pioneers in this country who, in 1901 and 1902,
attempted to arouse such a public sentiment, had much difficulty in educating
the people and in securing funds, but lately it has been an easier matter. Many
communities, large and small, have taken up anti-mosquito measures, and such
large cities as New York, Baltimore, New Orleans, Nashville, have given the
question serious consideration in their city councils and in their boards of
health, and have entered upon measures of greater or less efficacy. Many smaller
towns have begun the crusade also, and those which have been especially active
have been communities of summer resort. One of the early attempts was the
formation of the North Shore Improvement Association of Long Island, which
undertook a mosquito campaign involving over twenty-five square miles of terri-
tory along the north shore of Long Island, the territory including several villages
and many country homes of wealthy people. Following the first year’s work of
this Association a national anti-mosquito society was formed to encourage just
this kind of work, and this society has published instructions and pamphlets of
information which are at the disposal of all communities desiring to enter upon
the task of freeing themselves from mosquitoes.

Theoretically community work should be done under official auspices, and
should be inaugurated by boards of health, but official action is slow, even in the
United States where there is, as a rule, less red tape than in older countries.
Moreover, official action in sanitary measures is often conservative as well as
slow. As already pointed out, the health question is not the only one involved.
Abundance of mosquitoes means enormous economic loss to a community, en-
tirely aside from the important question of health, and individual property
422 MOSQUITOES OF NORTH AMERICA

owners realize this more than do official bodies. It is only necessary to cite the
increased value of real estate at summer resorts where the mosquito scourge has
been wiped out, and the great value of reclaimed marsh land for manufacturing
sites in the immediate vicinity of great cities, or for agricultural purposes at a
greater distance from the great centers of population.

In community work, therefore, as well as in most other measures of reform,
the organization of private citizens has usually been the initial step. Many
communities have their own village or town improvement associations, and many
cities have their citizens’ associations constantly alert to discover needed reforms
and improvements and to bring them emphatically to the notice of their elected
representatives on the City Council and to the Mayor’s appointees on the Board
of Health. It is through the mosquito committees of such associations that very
much of the work in this direction has been agitated and inaugurated, and doubt-
less this method will continue most effectively for some time to come.

The first step in undertaking such work is to interest several responsible
persons whose names carry weight in the community, and then to raise a small
fund, either by appropriations from funds at the disposal of the improvement
society, or whatever it may be, or by private subscription. Then these persons,
forming a committee, should issue a circular to every householder, signed by the
whole committee, reciting very briefly the well-known facts concerning the
breeding-places of mosquitoes and the measures which should at once be taken
by householders. A good plan also would be to have a public lecture given by
some expert, well illustrated, to which all householders should be invited. An
excellent circular of the character just described was issued in the early summer
of 1901 as follows:

The Village Improvement Society of South Orange.
South Orange, N. J.

The breeding place of the mosquitoes, that may infest your house, may be
looked for within your own house or grounds, or in your immediate neigh-
borhood.

The mosquito lays its eggs only upon standing water and passes the first ten
days of its existence in the water.

Without standing water there can be no mosquitoes.

Dr. Howard says, “I feel sure that the cesspools in South Orange must be
responsible for a great deal of your mosquito supply.” Therefore:

Look to your cesspools,

cisterns,
watertanks,
and any barrels or other receptacles in which water may stand for a few days,
either inside or outside the house.

It is suggested that you at once do away with every unnecessary water
receptacle.

Put kerosene oil in your cesspools and on surface of necessary standing water,
once in three weeks.

Oil placed on surface should not affect the taste of water drawn from beneath
the surface, but when that is not considered advisable, water receptacles should
be screened with a fine mesh screen.
CONVINCING THE PUBLIC 423

The mosquito being not only a serious annoyance, but a constant menace to
health, its extermination becomes a matter of public concern.
The cooperation of every household is requested.

Please report to............ the location of any pools of stagnant water in
your neighborhood.

After the issuing of the circular or the holding of the public lecture, or both,
if the members of the committee are too busy, as they are likely to be, to engage
to any extent in the actual superintending work, an intelligent superintendent
must be chosen, who will familiarize himself with the biology of mosquitoes and
especially with the character of mosquito breeding-places in general. He should
at once be put to work upon a survey of the mosquito topography of the neighbor-
hood. It will be well for him to make a map upon which every breeding-place,
aside from the chance receptacles about houses, should be noted with the greatest
accuracy and care. Every house having an uncovered water tank or having
rain-water barrels should also be noted, and for each locality the most effective
as well as the most economical remedy should be recorded. If these remedies
demand any large-scale work estimates of the necessary expenditures should be
indicated.

Such a careful report and map having been prepared and placed in the hands
of the committee, the amount of funds necessary can readily be estimated, and
the expenditure of such sums as it is found possible to raise can be considered and
agreed upon. The work can then be easily carried on through the summer under
the direction of this superintendent, and of course the amount of the expenditure
and the number of employees will depend entirely upon the local mosquito-breed-
ing possibilities.

Some small communities will find that a full understanding of the problem
on the part of individual householders will bring about great relief as the result
of individual work, and that the only organization necessary will be perhaps the
signing of a pledge by individuals to take care of their own premises. In other
communities the matter will be a little more serious, but there will be some where
the employment of a single man for two or three days a week throughout the
summer will result in freedom from mosquitoes. Again, however, in larger
communities the enforcement of municipal regulations will be found to be neces-
sary before a desirable result can be obtained, and where the village is built upon
swampy land or is surrounded by swamps the expenditure of considerable sums
of money will be found to be imperative.

In every community, however, there will pretty surely be ultra-conservative,
recalcitrant and ignorant citizens—people who will not take the trouble to pre-
vent the breeding of mosquitoes on their own premises—people in fact who will
violently object to the entrance on their premises of an individual who will do
the work for them. Such cases are not numerous, but they are always difficult
to handle, and, in the absence of municipal action, moral suasion must be tried
in the most ingenious ways which the committee can devise. Sir Ronald Ross,
in his excellent work “ Mosquito Brigades,” in writing of such persons, puts it
very happily in the following words:
424 MOSQUITOES OF NORTH AMERICA

“ The qualities chiefly necessary [in a superintendent] are energy, persistence,
and an entire indifference to public or private opinion. The need of the first
two is obvious; that of the last requires some explanation. The self-appointed
superintendent will be at once astonished, and perhaps alarmed, at finding that
his philanthropic and wholly harmless efforts are met at the outset by a storm
of letters to the local press, demonstrating the absurdity and even immorality of
his intentions; proving that mosquitoes cannot be destroyed, that they spring
from grass and trees; that they can be destroyed, but that it is wicked to make
the attempt because they were created to punish man; that they do not carry
malaria, because malaria is a gas which rushes out of holes in the ground, and
rises as a blue mist over the country ; that they do not carry yellow fever, which is
due to the effect of the tropical sun on rotting vegetation ; that they do carry
malaria and yellow fever, but in such small quantities that they act beneficially
as unpaid vaccinators of these diseases; and so on.* It is possible to ignore all
such epistles, because, where they do not contradict each other, someone else is
sure to contradict them ; but an occasional letter in reply does good, and, to speak
practically but rather cynically, serves to stimulate the necessary public interest
in the work by keeping the letter-writers at such a pitch of exasperation that they
give the campaign a constant stream of gratuitous advertisement in the news-
papers. We are permitted to be cynical in a good cause.

“ Fortunately, operations against mosquitoes can be conducted on a large
scale without much reference to private opinions—fortunately, because the
inertia of the masses regarding new pathological discoveries is so great that were
we to depend upon converting them, nothing would be done for half a century.
For some inscrutable reason, the man in the street, though he would scarcely
think of contradicting a lawyer or an engineer on matters of law or engineering,
finds himself quite equal to exposing the absurdities of the whole Medical Faculty
on a medical matter.

“These operations require no sacrifices or co-operation on the part of the
general public. Most householders are glad enough to have their mosquito larve
destroyed, and their backyards cleaned up for nothing. The reader, therefore,
if he sees fit to start the work we are considering, may quietly proceed in it un-
disturbed by criticism, and may calculate upon receiving not only as much public
support as his work will require during its progress, but the thanks of his fellows
at its termination. Indeed, the majority of the public will not be slow to recog-
nise the value of his efforts, even if they do not understand the scientific reasons
which have induced him to make them.”

In community work, after making an effort to insure the absence of household
breeding, the attention of the superintendent should be devoted to chance pools
along the public roadway and to breeding-places in unused land. Drainage or
filling in are the best measures to adopt. The superintendent will find it ad-
visable to attempt first to extirpate those breeding-places from which the greatest
numbers of mosquitoes are issuing. In this way, he will the sooner bring about
an appreciable diminution of the number of the insects, and of course the sooner
this diminution is noticed by the citizens the sooner will popular sentiment
unanimously support the work. The less populous breeding-places may await
treatment until a later date.

Large-scale operations requiring a considerable expenditure of money must be
organized very perfectly as to detail. The first example of this large-scale work

 

* Note.—Dr. Ross states that he has “ seen every one of these statements, and many
others equally absurd, made at least half a dozen times in the British press.”
ROSS ON ANTI-MOSQUITO WORK 425

done in the United States was carried on in the most intelligent way by the North
Shore Improvement Association of Long Island, mentioned above. Here as an
initial step work was done by the superintendent and engineer, Mr. H. C. Weeks,
during the summer of 1901. Mr. Weeks completed the survey of the large terri-
tory and estimated the cost of all operations. Another survey was made by two
biologists, Prof. C. B. Davenport and Mr. F. E. Lutz, of the Cold Spring
Harbor Laboratory, then of the Brooklyn Institute of Arts and Sciences, and
now of the Carnegie Institution. These gentlemen positively identified all
breeding-places. Still another survey was made by the late Prof. N. S. Shaler,
of Harvard University, who advised concerning the best methods of reclaiming
the salt marshes included in the territory, where certain species of mosquitoes
breed. Upon the basis of these surveys and reports the Association began in
1902 its active work of extermination.

The following is a summary, by Sir Ronald Ross, of the aims of anti-mosquito
work, and it is so admirable that it is quoted in full:

“ Summary of objects :—

“(1). We do not propose to exterminate mosquitoes in any entire continent.

We propose only to deal with them in the town in which we live, and in tts
suburbs.

(2). We do not propose to get rid of every mosquito even in this town.

We aim only at reducing the number of the insects as much as possible.

“(3). We do not think it possible to drain or otherwise treat every breeding
place in the town.

We aim at dealing with as many as possible.

“(4). We cannot exclude mosquitoes which may just possibly be blown into
the town from miles away.

We content ourselves with preventing the insects breeding in the town itself.

“Summary of methods :—

“(1). We start work at once with whatever means we can scrape together.

(2). We operate from a centre outwards.

“(3). We clear houses, backyards, and gardens of all rubbish ; empty tubs and
cisterns containing larve, or destroy the larve in them by means of oil.

(4). We show people how to do these things for themselves, and how to pro-
tect tubs and cisterns by means of wire gauze.

“(5). When we have cleared as many houses as we determine to deal with, we
clear them over again and again.

“(6). We fill up or drain away all the pools, ditches, old wells, and puddles we
can—especially those which contain most larve.

“(7). Such pools as cannot be filled up or drained are deepened and cleared
of weeds, if they contain larve. ;

“(8). Streams and water courses which possess larvee are ‘ trained?

(9), Where we can do nothing else we destroy the larvae periodically with oil,
or by brushing them out with brooms, or by other means.

“(10). We endeavour to interest our neighbours in the work, and to educate
the town into maintaining a special gang of men for the purpose of keeping the
streets and gardens absolutely free of stagnant, mosquito-bearing water.

“ Motto._Our motto should be one which I think will shortly become the
first law of tropical sanitation, namely—No Stagnant Water.”

After concluding an account of his own personal work at Lloyds Neck, Long

Island, and of the work done by the North Shore Improvement Association, Mr.
426 MOSQUITOES OF NORTH AMERICA

W. J. Matheson, speaking before the First Anti-Mosquito Convention in New
York, December 16, 1903, concluded that the work carried on had demonstrated
that, with the exception of the salt-marsh mosquitoes, the mosquito nuisance
can be controlled and abated in almost any locality where intelligent cooperation
can be secured and a systematic inspection made of the premises for the purpose
of destroying the breeding-places. Extermination, in his opinion, will ex-
terminate just as far as the intelligent land owner is willing to carry it, but
that it can not be done once and for all any more than weeding a garden or the
cropping of a lawn can be done once and for all. He concludes his paper with
the following words:

“ So far as my experience goes, it has been demonstrated that mosquitoes can
be as completely exterminated in any locality as dirt can be swept from a build-
ing, or as weeds from a walk, with the possible exception of the Culex Sollicitans,
and with the exercise of no more intelligence and much less labor than is required
in the performance of many domestic duties. My experience would lead me to

conclude that if mosquitoes continue to exist in any locality, it is because the
people are too indifferent to the annoyance to take the trouble to be rid of it.”

THE IMPORTANCE OF INTERESTING CHILDREN.

Under the general head of “ Remedies ” we have mentioned the efforts made
by Professor Hodge, in Worcester, Massachusetts, to interest the school children
of the city in the search for mosquito breeding-places. This must have been in
1901-2. But, the most serious and productive effort seems to have been made at
San Antonio, Texas, a year or so later, at the initiative of Dr. J. 8. Lankford,
of that city.

In November, 1903, there were a few cases of yellow fever in San Antonio
which caused several deaths, and a consequent interruption of commerce that
cost hundreds of thousands of dollars. In the effort to allay the panic, the
existence of yellow fever was denied, not only by persons having business in-
terests in the city, but by many medical men as well. Very many adults not
only denied the existence of the fever in the city, but denied the relation between
the mosquitoes and the fever. Perhaps the majority of the adults seemed too
old to learn; and to the enlightened physicians it appeared impossible to begin
education at the wrong end of life.

The Chairman of the Sanitary Committee of the School Board (Doctor Lank-
ford) grasped the happy idea that if the children were properly educated, sani-
tary matters in the future would be much better attended to. He suggested to
the Board that it would be valuable to educate all of the school children of the
city in prophylaxis and make sanitarians out of them all. The School Board
heartily approved of the proposition, and the campaign was at once begun to
educate the children on the subject of insects as disease carriers. The best
recent literature on the subject was procured and furnished to the teachers,
and a circular letter was sent to them outlining a proposed course and offering a
cash prize for the best model lesson on the subject. Teachers became deeply
interested. A crude aquarium, with mosquito eggs and larve was kept in
every school room, where the pupils could watch them develop; and large
WORK IN GERMANY 427

magnifying glasses were furnished in order that they might study to better
advantage. The children were encouraged to make drawings on the black-
board of mosquitoes in all stages of development; lessons were given and compo-
sitions were written on the subject. Competitive examinations were held, and
groups of boys and girls were sent out with the teachers on searching expeditions
to find the breeding-places. Rivalry sprung up between the ten thousand public
school children of the city in the matter of finding and reporting to the health
office the greatest number of breeding-places found and breeding-places de-
stroyed. Record was kept on the blackboards in the schools for information as
to the progress of the competition, and great enthusiasm was stirred up. In
addition to these measures, a course of stereopticon lectures was arranged, group-
ing the pupils in audiences of about one thousand, from the high school down,
and, in Doctor Lankford’s words,

“It was an inspiring sight to watch these audiences of a thousand children,
thoughtful, still as death, and staring with wide-open eyes at the wonders re-
vealed by a microscope. It seemed to me that in bringing this great question
of preventive medicine before public school children we had hit upon a power
for good that could scarcely be over estimated.”

The result of this work, it is pleasing to say, was a decided diminution of
mosquitoes in San Antonio. There was some opposition among the people,
but on the whole the movement was very popular. One result of this work
was that, while previously there had been from fifty to sixty deaths a year from
malaria, this mortality was reduced seventy-five per cent the first year after this
work was begun, and in the second year it was entirely eliminated from the
mortality records of San Antonio.

In organizing community work against mosquitoes, the school children here-
after must be counted upon as a most important factor. Almost every child is
a born naturalist, and interest in such things comes to them more readily than
anything else outside of the necessities of life. They are quick witted, wonder-
fully quick sighted, and as finders-out of breeding-places they usually can not
be approached except by adults of special training. One of the first steps that a
community should take, is, therefore, to arouse the interest of the children in
the public schools.

SOME RECENT WORK IN GERMANY.

The city of Leipzig quite recently has begun a crusade against malaria under
the direction of the City Council. The following account of this work was sent
in by U.S. Consul 8. P. Warner, and is published in the “ Monthly Consular and
Trade Reports,” for June, 1909:

“ So many cases of malaria have recently occurred in those sections of Leipzig
which are adjacent to any one of the four rivulets which flow through the city
that the city council has decided to adopt stringent measures to exterminate the
mosquitoes (Anopheles) that spread the disease.

“Tn order that the work of extermination may be thoroughly and systemat-
ically carried out the city council has notified all housekeepers in the infected
sections of the city to carefully examine their houses or apartments for mos-
quitoes and to destroy any that may be found. Every household in the districts
428 MOSQUITOES OF NORTH AMERICA

concerned has been furnished by the city council with a large circular, which, in
addition to information as to the cause and spreading of malaria, contains advice
as to the best means of destroying the malaria mosquitoes.

“ Certain dates have been specified between which the houses are to be searched
and the mosquitoes destroyed. At the expiration of the time specified inspectors
appointed by the city council will visit each house and apartment and make
careful examinations to see that the work of exterminating the mosquitoes has
been properly carried out. Those who fail to comply with the regulations
promptly and thoroughly will be subject to a fine of about $7.50.”

WORK ALONG RIVER FRONTS.

Communities living along navigable rivers may have good anti-mosquito work
hampered by the constant reintroduction of mosquitoes from boats landing at
their river fronts. This point has been especially noted in the course of the
excellent work done under the direction of Dr. Andrew Balfour at Khartoum on
the Blue Nile. The following passage is taken from the First Report of the
Wellcome Research Laboratories, pages 21-22:

“ At an early period the steamers were found to be largely infected, especially
with the larve of Stegomyia fasciata, and to a less extent by those of Culex
fatigans. Anophelines, either as larve or imagines, have never been met with;
but up-country, as will be noted later, the adults are frequently to be seen on
board, and may remain as passengers for a considerable period. At first it was
decided to use lime for the steamer bilges, but this was said, erroneously I be-
lieve, to act upon iron and to be unsuitable. Consequently crude petroleum was
recommended, though not so good nor so easily applied. Along with this the
periodical emptying of the bilge and fumigation with the sulphur squibs de-
scribed by Colonel Giles were advised, the latter to get rid of the adult insects.
Unfortunately in the case of the steamers familiarity had evidently bred con-
tempt, for, at first, despite the co-operation of the Director of the Steamers and
Boats Department, little energy was displayed by the engineers in charge, and
the preventive measures were largely ignored, and in some instances even
ridiculed. This was the more to be regretted as there is no doubt that mos-
quitoes can be banished from all the steamers if a little care and trouble were
taken. Mr. Beadnell, of the Geological Survey, carried out these simple methods
on the S. S. ‘ Nubia,’ and practically cleared her of mosquitoes, so that for the
first time he was able to sleep below in comfort. A great improvement also
resulted in the case of the gunboat ‘ Zafir, in which I went to Dueim and found
to be simply swarming with adult Culices and their larve, while these measures
absolutely prevented any mosquitoes breeding out on board the 8. S. ‘ Amka’
during a period of nearly two months, the greater part of which was passed in
regions swarming with these winged pests. Latterly, I am glad to say, the
engineers have been impressed with the necessity of doing all in their power to
aid the brigade. This is the more necessary as it is easy for the steamers to in-
fect the town and thus spoil much of the work done and render it futile.”
EXAMPLES OF MOSQUITO CONTROL.

It is proposed in this section to describe briefly some of the most striking
examples of successful warfare against mosquitoes that have been carried out
since 1900 and bring them together into one consecutive account. Of many of
them the details are not well known, on account of the inaccessibility of the
documents of record.

WORK IN HAVANA DURING THE AMERICAN OCCUPATION,
1901-2.

One of the most striking examples of clean, efficient anti-mosquito work is
that done by the American troops in Havana at the close of the Spanish War,
under the direction of the Army Medical Corps, and under the especial direction
of Col. W. C. Gorgas, U.S. A. In the statements which follow, Colonel Gorgas’s
published writings have been freely used.

Yellow fever had been endemic in Havana for more than 150 years, and
Havana was the usual source of infection for the southern United States. By
ordinary sanitary measures, improved drainage and similar means, the death
rate of the city was reduced from 100 per thousand in 1898 to 22 per thousand
in 1902. But these measures had no effect upon yellow fever, this disease in-
creasing as the non-immune population increased, and in fact in 1900 there was
a severe epidemic.

Aédes calopus was proved to be the carrier of yellow fever early in 1901, and
then anti-mosquito measures were immediately begun. Against adult mos-
quitoes no general measures were attempted, although screening and fumiga-
tion were carried out in quarters that were or had been occupied by yellow-fever
patients. It was found that calopus bred principally in the rain-water collec-
tions in the city itself; that Culex quinquefasciatus bred everywhere, and that
Anopheles albimanus bred principally in the suburbs in pools and puddles well
protected by grass. Two mosquito brigades were started: one to take care of
calopus, and the other of Anopheles.

The work of the so-called “ stegomyia brigade” was confined to the built-up
portions of the city. The city was divided into about thirty districts, and to
each district an inspector and two laborers were assigned, each district contain-
ing about a thousand houses. The mayor of Havana issued an order requiring
all collections of water to be so covered that mosquitoes could not have access,
a fine being imposed in case the order was not obeyed. The water supply of
Havana was very hard, and it was customary for every family to collect rain-
water in barrels. As the majority of the people in the large tenement houses
were poor, and as each family had a rain-barrel, the Health Department covered
these barrels at public expense, leaving a small screen opening through which the
water could enter and placing a spigot at the bottom through which it could be

429
430 MOSQUITOES OF NORTH AMERICA

drawn. Every house in Havana, on the average, has a cesspool, the liquid con-
tents generally seeping into the soil. The inspector on each visit had from four
to six ounces of petroleum poured into the cesspool, and where this was not
accessible it was poured into all closets connected with the cesspool. All recep-
tacles containing fresh water that did not conform to the law were emptied,
and, on a second offence, destroyed. If the owner was an old offender, he was
prosecuted under the law and fined.

The result of this work of the so-called “ stegomyia brigade” was that, while
in January, 1901, there were 26,000 fresh-water receptacles containing mosquito
larve, in January, 1902, there were less than 400 such receptacles containing
larvee ; mosquitoes had rapidly decreased, and were entirely absent in many parts
of the city. The result of this work, thoroughly done, was to wipe out yellow
fever in Havana.

The “anopheles brigade” was organized for work along the small streams,
irrigated gardens and similar places in the suburbs, and numbered from fifty to
three hundred men. No extensive drainage, such as would require engineering
skill, was attempted, and the natural streams and gutters were simply cleared of
obstructions and grass, while superficial ditches were made through the irrigated
meadows. Among the suburban truck gardens Anopheles bred everywhere in the
little puddles of water, foot-prints of cattle and horses, and similar depressions
in grassy ground. Little or no oil was used by the “ anopheles brigade,” since it
was found in practice a simple matter to drain these places. At the end of the
year it was very difficult to find water containing mosquito larve anywhere in
the suburbs, and the effect upon the malarial statistics was striking. In 1900,
the year before the beginning of the mosquito work, there were 325 deaths from
malaria; in 1901, the first year of mosquito work, 151 deaths; in 1902, the
second year of mosquito work, 77 deaths. Since 1902 there has been a gradual,
though slower decrease, as follows: 1903, 51; 1904, 44; 1905, 32; 1906, 26;
1907, 23.

WORK AT THE ISTHMUS OF PANAMA.

The United States government has very properly used the services of Colonel
Gorgas, who was in charge of the eminently successful work at Havana, by
appointing him Chief Sanitary Officer of the Canal Zone during the digging of
the Canal. In 1904 active work was begun, and Colonel Gorgas was fortunate
in having the services of Mr. J. Le Prince, who has been chief of his mosquito
brigades in Havana, and therefore was perfectly familiar with anti-mosquito
methods. In Panama, as in Havana, the population had depended principally
upon rain-water for domestic purposes, so that every house had cisterns, water-
barrels and such receptacles for catching and storing rain-water. The cities of
Colon and Panama were divided up into small districts with an inspector in
charge of each district. This inspector was required to cover his territory at
least twice a week and report upon each building with regard to the breeding-
places of mosquitoes. Al] the cisterns, water-barrels and other water receptacles
in Panama were covered, and in the water-barrels spigots were inserted so that
WORK IN PANAMA 431

the covers would not have to be taken off in drawing water. Upon first inspec-
tion, in March, four thousand breeding-places were reported in Panama alone.
At the end of October less than four hundred receptacles containing larve
were recorded ; this gives one a fair idea of the reduction in the number of mos-
quitoes in the city. These operations were directed primarily against the yellow-
fever mosquito, and involved the other species that inhabit rain-water barrels.
Against the Anopheles in the suburbs the same kind of work was done which was
done in Havana, with excellent results.

The same operations were carried on in the villages between Panama and
Colon. There are some twenty of these villages of from five hundred to three
thousand inhabitants each. The result of the whole work has been the elimina-
tion of yellow fever, and the very great reduction of malaria. The remarkable
character of these results can only be judged accurately by comparative methods.
It is well known that during the French occupation there was an enormous
mortality among the European employees and that this was a vital factor in the
failure of the work. Exact losses can not be estimated, since the work was done
under seventeen different contractors. These contractors were charged one
dollar a day for every sick man taken care of in the hospital of the Canal Com-
pany. Therefore it often happened that when a man became sick his employer
discharged him to avoid the expense of hospital charges. There was no police
patrol of the territory and many of these men died along the line. Colonel
Gorgas has stated that the English consul who was at the Isthmus during the
period of the French construction was inclined to think that more deaths of
employees occurred outside of the hospital than in it. A great many were found
to have died along the roadside while endeavoring to reach the city of Panama.
The old superintendent of the French hospital stated that in one day three of
the medical staff died from yellow fever, and in the same month nine of the
medical staff. Thirty-six Catholic sisters were brought over as female nurses,
and twenty-four died of yellow fever. On one vessel eighteen young French
engineers came over, and in a month after their arrival all but one had died.

With the mosquito relation well understood, not a single case of yellow fever
was contracted during the first two years under Doctor Gorgas, although there
were constantly one or more yellow-fever cases in the hospital, and although
the nurses and doctors were all non-immunes. The nurses never seemed to
consider that they were running any risk in attending yellow-fever cases night
and day in screened wards, and the wives and families of officers connected with
the hospital lived about the grounds knowing that yellow fever was constantly
being brought into the grounds and treated in nearby buildings. Americans,
sick from any cause, had no fear of being treated in the bed immediately ad-
joining that of a yellow-fever patient. Colonel Gorgas and Doctor Carter lived
in the old ward used by the French for their officers, and Colonel Gorgas thinks
it safe to say that more men had died from yellow fever in that building than in
any other building of the same capacity at present standing. He and Doctor
Carter had their wives and children with them, which would formerly have been
considered the height of recklessness, but they looked upon themselves, under
432 MOSQUITOES OF NORTH AMERICA

the now recognized precautions, as safe almost as they would have been in
Philadelphia.

The existence of endemic foci of yellow fever at points in constant communi-
cation with the Canal Zone, and the consequent danger of reintroduction of the
disease, has made it necessary to maintain vigorous mosquito control. Aside
from the comparatively simple control work against house-mosquitoes, a far
more difficult and extensive campaign has been prosecuted against Anopheles.
This has proved highly profitable through the resultant reduction in malaria
and the consequent increased efficiency in the canal workers and saving of
hospital expenses. The great difficulties imposed by the climate and topography
of the region in this work against Anopheles were further increased by the opera-
tions in the construction of the canal which unavoidably created, at least tem-
porarily, numerous breeding-places for mosquitoes.

No figures of actual cost of the anti-mosquito work either in Havana or in the
Panama Canal Zone are accessible to us, but it is safe to say that it was not
exorbitant and that it was not beyond the means of any well-to-do community
in tropical regions.

WORK IN RIO DE JANEIRO.

One of the most difficult problems of its character was that of freeing Rio de
Janeiro from its reputation as a great yellow-fever center. The difficulties
were very great, and the amount of money required for efficient work was
enormous. Rio de Janeiro has a population of more than 800,000 people; it
extends over an area of 430 square miles; it is very irregular in its topography,
varying in altitude from 1 to 460 meters above the sea level; it had at the time
82,396 houses, and, as in all great centers of population, the inhabitants of many
of the houses, if not resisting the efforts of the sanitary authorities, surely did
not facilitate them.

Work was begun in April, 1903, under the direction of the Public Health
Service, but the organization effected was of a temporary character and needed
the passage of new laws by Congress, which were enacted in January, 1904, and
resulted in the reorganization of the hygienic service of Brazil. A service for the
stamping out of yellow fever was created. One million six hundred and fifty
thousand dollars was appropriated annually for this work. The service estab-
lished included one medical inspector, ten sanitary inspectors (physicians), one
administrator, one customs inspector, one accountant, seventy medical students,
nine subchiefs, two hundred overseers, eighteen guards of the first class, eighteen
guards of the second class, and one thousand workmen; and in addition to this
personnel, the assistance of the Public Health Service corps of inspectors was
called upon.

The city was divided into zones, according to the density of the population,
and in these zones the work was divided into two sections: (1) Isolation and
sanitation; (2) the policing of the infected districts. Under the first section,
yellow-fever patients were removed to the pest house, residents were isolated,
and houses were disinfected. The second, the sanitary police force, visited every
RIO DE JANEIRO CAMPAIGN 433

building in the city, destroyed the early stages of mosquitoes, and abolished or
screened standing water where possible. One force worked in buildings, and
another in vacant lots, streams, marsh lands, etc. The following paragraphs
relative to this work are quoted from an address made by Doctor Oswaldo Cruz

before the Latin-American Medical and Sanitary Congress held in Rio de
Janeiro, August 1 to 10, 1909.

“Yellow-fever cases were made known to the sanitary inspectors by the
reports of medical assistants, of the head of the family in which a case occurred,
or by any one to whom the facts of the case were known, in accordance with the
requirements of the law. The sanitary service being advised, a competent group
of inspectors and authorities were at once dispatched to the locality, having with
them a physician. The latter ascertained if the case was one for isolation treat-
ment (whether under or over four days after the onset of the disease), and if
the case required isolation the same was carried out either in the dwelling house
or in the hospital, hospital treatment being resorted to only when the dwelling
was unsuited to isolation treatment or when the patient wished it. In such cases
the patient was taken to hospital in a vehicle closed against the entrance of mos-
quitoes and the house was disinfected in accordance with the system below out-
lined. In the case of isolation in the home the physician chose a roomy quarter
of the house with door opening into another secluded part of the house and with
windows. If there were more than one door, the others were temporarily closed.
The patient was kept under a netting enveloping the bed upon which he lay
during the time permanent quarters were being arranged. The doors and win-
dows of the room to be isolated and of the rest of the house as well were sealed
to prevent the exit of mosquitoes existing there, the windows of the isolated
room being fitted with wire screens in such a way as not to interfere with ventila-
tion, all other openings to the outside or to other parts of the house being sealed
with cloth or paper. The only door to be used in the use of the room must be
specially fitted with a double door drum, provided with an arrangement which
does not permit of both doors being opened at the same time. This apparatus
prevents the entrance and exit of mosquitoes, and after the room is thus prepared
the door and windows are closed and camomile is burned in the room 3 to 4 hours
in the proportion of 10 grams per cubic meter of space. The room is then well
ventilated and is ready to receive the patient. The rest of the house is well
calked and isolated from the room in which the patient is placed and disinfected
with sulphur gas, as below indicated. During this operation a sanitary inspector
remains in the room with the patient and stops the entrance of any gas which
may possibly find its way through some overlooked crevice. During the prepa-
ration for disinfection the sanitary authorities make a thorough inspection and
destroy any mosquito larva they find, pick up or destroy any vessels lying about
which might serve as a receptacle for mosquito-breeding water and close water
boxes against the same danger. The patient remains in isolation for seven days,
after which isolation may terminate, if the family so wishes. The infected
district is then treated as above indicated; that is, by disinfection, sanitary
policing, and medical supervision. Disinfection is carred on in two ways, one
force working from the center toward the outer limits of the district and the
other from the boundaries of the district inward. The area of infection being
determined over as large an area as possible, these two sections separate, one of
which begins immediately with the house in which the case of yellow fever
occurred, the other beginning at those houses which might possibly have been in-
fected at the greatest possible distance from the case in isolation. The purpose
434. MOSQUITOES OF NORTH AMERICA

of such a system was to destroy all mosquitoes which might have carried infec-
tion within the district.

“While the disinfecting force is thus at work the police division, under the
direction of a physician and of students who direct the different sections, operates
throughout the infected district, making every effort to destroy all mosquito
larvee and to prevent the possible breeding of mosquitoes outside as well as inside
the houses. Where larve are likely to exist in stagnant water or refuse of any
sort, petroleum mixed with creoline, lysol, or similar products is thrown over the
water or refuse in sufficient quantity to kill the larve instantly. Where it is im-
possible to use petroleum, as in the case of tanks and boxes for household use, a
small fish, the ‘ barrigudo’ or ‘ Girardinus caudimaculatus’ is placed in large
numbers in the water. This fish destroys the larvae of mosquitoes most vora-
ciously. Larve in the drains are destroyed by the use of Clayton gas, which is
pumped into the sewer, which has been previously divided into compartments.
Simultaneously with the disinfection the sanitary inspectors make daily in-
spection of the suspected district, examining every inhabitant supposed not to
be immune, that is, children under 5 and all foreigners of less than 5 years’ resi-
dence in Rio. These are subjected to the closest vigilance, being placed in
isolation at the least tendency to rising temperature. Reports are made in
writing, those to whom this duty falls being required to fill out daily a bulletin
sent out by the medical inspector to the chief of each district. In this report
must be given the record of any who work outside the district or who for any
reason absent themselves therefrom, a record of their condition being also kept
by the physician in the district in which they work or are temporarily resident.
When any inhabitant absents himself from the district the record must show his
address, where he will be subjected to vigilance on the part of the authorities
there, If the person under vigilance evades the attention of the physician and
withdraws without giving notice, the owner of the house in which he lived is
fined, he himself is apprehended by the sanitary police, fined, and subjected to
renewed vigilance.

“ The vigilance in each district extends over a period of one month after the
appearance of the last case. To give an idea of this service we will note the
figures covering the prophylactic campaign in the infected district about the
cotton factory, ‘ Fabrica das Chitas,’ in 1906. The inspection was carried out
by 18 doctors, who examined daily all suspected persons, in all, 7966 persons, of
whom 2989 were not immune. Sixty cases were reported, of which only 19
proved to be yellow fever, and the district was declared entirely freed of infection
after six months. With the combination of the three systems there is no doubt
about cleaning up effectively any district in which yellow fever may appear.
In normal conditions the police service is carried out with equal painstaking,
especially in the districts where infection last appeared. When, after some time,
there seems no longer to be danger of new infection, the inspectors allow water
to stand in several marked spots most favorable to mosquito breeding. These
pools are then carefully watched, and examined at frequent intervals. This is a
sure way to indicate the presence of the mosquito and is a trap for those about to
spawn. They are thus most easily destroyed. In many zones of the city these
traps revealed the presence of no mosquitoes whatever.”

The actual results which followed this admirable work are shown by a table
indicating the death rate from yellow fever in Rio from 1872 to date, and which
indicates that perfect success has been reached.
CONTROL WORK IN MEXICO 435

MorraLiry From YELLow FEVER IN Rio DE JANEIRO FROM 1872 To AucusT, 1909.

. Deaths Year Deaths Year Deaths
chav arcscialar elise onesie 102 S85 icclongweeeoieas TA4D
ABTS: eicassesates ices s 3659 US86) eu sad kanes. 1449
VB TE. so cccsalets cei cciese asc 829 TBST sissewverendvactvscesins 137
ABTS ei kek Redman 1292 USS S) cre csagueievessraaieitd TAT
TSG ssicscs fooectuncteretstay 3476 VERGE oS ee kuc screen tv dees 2156
LET siopsnctsut eeakancistaresays 282 SOO is crsaareubeawaave 719
TBTS sshescanssicerae steer 1176 WS 9A, ase aces wtcieeren oped 4456
BTS) snicoe testament: 974 TBD scree, ce aeietnennete 4312
1880) ocnmpevaunatecs. 1625 DOOR spans date apavsliereraiere 825
TBSD a sseeeves cece ive 257 TS OAT | revo sos Grcestaasertes 4852
1882 estes geiaucs 89 U8 9S 3 cutewenu arses 818
TBS 8) sciecerece ie iscarnauceais 1608 1896) seessaweeeywates 2929
WBS: oo csce sy cst Yenc Soctoreye 863 1897 sseeasccueuwcs 159

 

WORK IN VERA CRUZ AND MEXICO GENERALLY.

The President of the Superior Board of Health of the Republic of Mexico,
Dr. Eduardo Liceaga, was one of the first to grasp the importance of the mos-
quito discoveries of the American Army Board, and one of the first to make an
effort to turn them to account. As elsewhere, he met with conservatism and a
certain amount of disbelief, but it was not long before he succeeded in establish-
ing an anti-mosquito service for practically all of the towns in which yellow fever
appeared to be endemic, and devoted especial attention to the larger sea-ports
most frequently entered by foreign vessels. In 1893 the disease appeared in epi-
demic form in several cities of the Gulf States of Mexico and spread to some
interior cities as well, such as San Luis Potosi and some in the State of Nuevo
Leon. By the aid of strong executive orders on the part of President Diaz, the
Superior Board of Health was able to take action in all of the States except one,
and was able to arrest the epidemic. The plan of campaign was based upon the
mosquito doctrine, and the measures involved the isolation of patients, the
thorough disinfection of dwellings by sulphur dioxide, the drainage of swamps,
covering of drinking-water reservoirs, and the use of petroleum.

In the course of this work and that which followed, taking Vera Cruz to be
the oldest and most permanent focus of yellow fever in the Mexican Republic,
and assuming that all the epidemics had found their origin in that place, the
principal attention of the Superior Board of Health was devoted to that city.
The town was divided into four districts, each of which was placed under the
charge of an experienced physician, and each of these had first-class sanitary
agents. Subordinate to these latter, second-class agents were appointed, and a
certain number of laborers were added. As a result of this effective ogarniza-
tion, Carroll, writing his chapter on yellow fever for Osler’s Modern Medicine at
the close of 1906, was able to make the following statement: “ In Mexico yellow
fever has been eradicated from its endemic focus at Vera Cruz through the
able efforts of Eduardo Liceaga, the President of the Superior Board of Health,
whose complete grasp of the problem and whose enlightened and energetic action
has added support to the mosquito doctrine, and would have controlled the dis-
ease absolutely if the same means of enforcement were available in Mexico as in

Cuba in 1901.”
29
436 MOSQUITOES OF NORTH AMERICA

The later developments of the work in the Mexican Republic under Doctor
Liceaga’s leadership have been remarkable. In the American Journal of Public
Hygiene, new series, volume vi, No. 1 (February, 1910), is published Doctor
Liceaga’s “ Annual Report on Yellow Fever in the Mexican Republic, from Au-
gust 16, 1908, to date,” a paper read before the American Public Health Asso-
ciation at Richmond, Va., October, 1909. The following paragraphs concluding
this report will give an idea of the excellent results which have followed the
work of the sanitary officials in Mexico:

“The campaign against Yellow Fever, which commenced in the Mexican
Republic in the year 1903, has continued uninterrupted up to this date, without
even suspending it during the Winter months as is done in other countries ; that
the war on the mosquitoes is so efficacious that there are none left in Veracruz,
and consequently, there are no stegomyas, as demonstrated by the reports ren-
dered by the physician of the Public Health and Marine Hospital Service of the
United States, who is resident in that Port.

“The cases which have been observed in Merida and surrounding villages,
arise from the existence in that city of over thirty thousand water tanks which
could not be so easily and securely watched as those of Veracruz.

“In the entire section which was formerly devastated by Yellow Fever we
continue to canalize the deposits of standing water and to fill up the hollows, as
well ss to spread oil on all those ponds which cannot be otherwise filled in or
covered.

“We continue to fumigate the dwelling houses, workshops, schools, etc., in
which we have encountered either cases of Yellow Fever or any suspected cases.

“We continue the surveillance over the passengers who travel by rail in any
part of the region which formerly suffered from Yellow Fever, and this service
is especially active along the line of the Tehuantepec Railroad.

“In the ports of Coatzacoalcos, on the Gulf Coast and Salina Cruz on the
Pacific, it is nearly four years since a single case of Yellow Fever was observed.”

WORK IN JAPAN.

Work in Japan, under Surgeon Major Tsuzuki, as early as 1901, confirmed
experimentally the malarial relations of Anopheles, and later a large-scale ex-
periment was carried on among the Japanese troops occupying Formosa, which,
on account of its large scale, served to set at rest any doubts which had previously
existed as to the value of mosquito protection. Portions of Formosa are mala-
rious, and the following table indicates the conditions existing among the troops
from 1897 to 1900, before there had been any control work in the modern sense:

 

 

The number | The number | Ratio of pa- Ratio of

of patients of deaths tients death
Per cent Per cent
1897 41,825 267 272.485 1.739
1898 84,752 270 249 394 1,938
1899 29,371 284 221.263 2.189
1900 830,224 272 222.414 2.002

 

 

 

 

 

From the 21st of September, 1901, to the 28th of February, 1902, work based
on the mosquito theory was carried on by order of the Governor of Formosa,
JAPANESE ARMY WORK 437

on the advice of Doctor Koike, Surgeon-General, as shown in following quota-
tion. This account of the experiment is taken from an address by Dr. K.
Tamura, Delegate from Japan to the Eleventh Annual Meeting of the Military
Surgeons of the United States Army, June 7, 1902:

_ “Half the second company, first battalion of infantry at Kirun, Formosa, 115
in number, was employed from the day of their landing at Kirun, and we gave
it the name of ‘ Protected troops” This troop was thoroughly provided with
means of protection from mosquito bites. They were confined in the casern
from half an hour before sunset, to half an hour after sunrise, the casern having
been specially made to prevent mosquitoes entering, and they wore gloves and
coverings of the head, specially made for that purpose, when on service at night.
“The results of these new methods for the prevention of malaria were abso-
lutely good. Another half of the second company (called by us comparison
troop) and all the other companies of the battalion (called by us unprotected
troop) had a great many malaria patients, but the protected troop had none.
“The table of the numbers of patients is as follows:

 

 

 

 

 

Average, | Numberof | Ratio of
number of umber o io o
men patients patients
Per cent
Protected troop...... 114.49 0 0
Comparison troop.... 104.34 34 82.59
Unprotected troop.... 646.36 285 44.09

 

 

 

“The experiment of Grassi in Italy shows that 5 cases of malaria were ob-

served among 112 persons, and Celli observed 11 cases in 203 persons, but our
case shows none in 114 persons.

“The news spread rapidly in the whole island and all the troops despatched
there became very cautious regarding. the bites of mosquitoes. c
itself gave good results, and the number of patients and deaths decreased dis-
tinctly last year, compared with the preceding years.

This caution

 

 

Number of | Number of Ratio of Ratio of

patients deaths patients death
Per cent Per cent

From 1897 to 1900, average. 34,043 27,325 242.514 1.947
MOOV issris cars sensuee a oOo ges 22,438 14,500 173.211 1.149

 

 

 

 

 

“ Now it is very clear that the prevention of Malaria is secured by guarding
against mosquitoes, and we believe that Formosa will become a healthy island

within a few years.”

In the recent war between Russia and Japan, the Japanese gave the world an
example of field sanitation hitherto unequaled in history, a vivid account of
which will be found in an article “ The Real Triumph of Japan,” by Dr. Louis
Livingston Seaman, formerly Surgeon-Major, U. S. Volunteers (New York,
1906), from which the following facts are drawn:

Longmore’s tables, based on the records of the battles of the last 200 years,
show that there has rarely been a conflict of any long duration in which there
438 MOSQUITOES OF NORTH AMERICA

have not been four deaths from disease to one from bullets. In the Spanish-
American War there were fourteen deaths from disease to one from battle.
Japan in her war with China, in 1894, lost three from disease to one from
bullets; but from February, 1904, to May, 1905, in her war with Russia four
were lost in battle to one only from disease, the exact figures being 52,946 lost
in battle and 11,992 lost from disease, and the significant fact must be added
that of the total sick only 3.51 per cent were sick with infectious diseases. There
were only 1257 cases of malaria in the whole army, six hundred thousand strong,
in the eighteen months duration of the war, whereas in 1894, in the war with
China, there had been 41,734 cases of malaria.

“ At the outset of the campaign the purifying of cities occupied was begun and
attention was paid to mosquito breeding-places. One of the orders issued was
that the waste water of the barracks should be connected with the town gutters.
Incidentally it may be noted that all articles sold publicly were required to be
covered to protect them from flies. In the book of health instructions issued to
soldiers occurred the paragraph, ‘ Malaria is spread by mosquitoes; therefore
protect yourself from them as much as possible.’ The soldiers had their camp
kettles with them, they were furnished with water boilers, and all water had to
be boiled before being drunk. They were furnished with mosquito bars, and
every man was enveloped in a bar during the mosquito season.

“The occurrence of 1257 cases of malaria in an army six hundred thousand
strong must be contrasted with a telegram sent from General Shafter at Santi-
ago on August 8th during the Spanish-American War, which read ‘ At least
seventy-five per cent of the command has been down with malarial fever from
which they recover very slowly... .””

It should be noted that Major Seaman was disappointed not to find mosquito
nettings in the main hospital in Tokio and that he states that this hospital was
inferior in this and certain other respects to the second and third reserve hos-
pitals in Manila. He states that at some of the hospitals netting was added as
the mosquito season approached, but it is only fair to infer that at this main hos-
pital the Japanese surgeons knew what they were about and were certain that
the absence of the mosquito bars involved no danger to the patients.

WORK IN ALGERIA.

In 1902 an anti-malarial campaign was begun in Algeria, under the auspices
and at the expense of the Pasteur Institute of Paris. The work was begun in
a small way, and the service was afterwards extended and supported by the
Algerian government, and it is still being carried on. Drs. Edmond and Etienne
Sergent were assigned to the work, and in 1903 published an account of the early
demonstrations. The investigators propounded to themselves the following ques-
tion: Is it possible, under the conditions existing in Algeria, to defend a group
of Europeans from malaria? They decided to use no prophylactic measures
whatever except the destruction of Anopheles. The management of the East
Algerian Railroad placed at their disposal one of the stations of that line.
This station, which was called Alma, was a hot-bed of malaria. Nine agents
ALGERIAN WORK 439

had been stationed there between the 1st of July, 1894, and the 1st of
December, 1901. All of them were seriously ill with malaria, and the first eight
left their positions on account of malarial fever by the advice of their physicians.
The ninth was the man in charge at the time, who was very thoroughly infected.
The families of these agents, concerning which there were no statistics, were all
and always feverish, according to the best information. It seems that there did
not exist a person who had ever lived in this station a single summer without
contracting malaria. At the time when the work began, 26th of June, 1902, there
were thirteen people living in the station; among them nine had been there a
year or more and were malarious; four had arrived during the winter and had
never had malaria. In the neighborhood of the station there were two families,
one of Arabs and one of French. All members of these two families were
malarious and refused to be protected, and therefore constituted a constant
source of infection for the Anopheles. It was the same way with the travelers
who came to the station to wait for trains leaving in the evening or at night.
Most of them were Arabs coming from nearby places notoriously unhealthy.
The conditions of the problem, then, were severe. It was necessary to protect
from the bite of infected Anopheles four persons not previously exposed, and
nine others already malarious, the latter from reinfection. The measures under-
taken were to protect this group of people from adult Anopheles and to destroy
the Anopheles larve. This was done in the usual way. The openings to the
building, doors, windows and chimney, were screened. Breeding-places were
searched for and all found were treated with kerosene. On leaving the station
at night, veils and gloves were used, but in spite of this watchfulness it was not
certain that all of the inmates invariably observed this precaution. The
results were excellent. The numbers of the mosquitoes were greatly reduced by
the work against the early stages; the building was almost entirely protected—
so much so that but nine Anopheles succeeded in gaining entrance. At the end of
the season not one of the four new people had shown the slightest symptom of
malaria, a condition which it is safe to say had not occurred before in that
locality, and the others, although having some fever, showed no indication of
reinfection.

This was only an initial experiment, to prove what could be done, and the
results were placed before the Governor-General of Algeria and the members of
Congress as well as the departmental and communal authorities. The expenses
incurred amounted to 304.80 francs. The governmental efforts since that time
seem to have been very considerable. In 1904 malaria was pandemic in Algeria,
but through increased knowledge and extended repressive measures, as the report
for 1908 shows, the situation in that year was very much better than in 1904.
The work included conducting demonstrations to instruct the people, in widen-
ing each year the territory covered, and in organizing anti-malarial campaigns
in different localities by the physicians, engineers, etc., stationed in those
localities. Propagandic work of all kinds is going on, including placards in the
railway carriages and elsewhere, and teaching anti-malarial measures in all the
schools. Later reports indicate an awakening of the country that can not fail to
be productive of great good.
440 MOSQUITOES OF NORTH AMERICA

WORK IN ISMAILIA.

Another striking example of excellent work of this kind is found in the report,
published in 1906, on the suppression of malaria in Ismailia, issued under the
auspices of the Compagnie Universelle du Canal Maritime de Suez. Ismailia
is now a town of 8000 inhabitants. It was founded by DeLesseps in April, 1862,
on the borders of Lake Timsah, which the Suez Canal crosses at mid-distance
between the Red Sea and the Mediterranean. Malarial fever made its appear-
ance in very severe form in September, 1877, although the city had up to that
time been very healthy, and increased, so that since 1886 almost all of the in-
habitants have suffered from the fever. In 1901 an attempt to control the dis-
ease was made on the mosquito basis, and this attempt rapidly and completely
succeeded, and all traces of malaria disappeared from the city after two years
of work. The work was directed not only against Anopheles mosquitoes, but
also against other culicids, and comprised, besides the usual measures, the drain-
age of a large swamp. The initial expense amounted to 50,000 francs, and the
annual expenses since have amounted to about 18,300 francs.

The results may be summarized about as follows: Since the beginning of
1903 the ordinary mosquitoes have disappeared from Ismailia. Since the
autumn of 1903 not a single larva of Anopheles has been found in the protected
zone, which extends to the west for a distance of one thousand meters from the
first houses in the Arabian quarter and to the east for a distance of 1800 meters
from the first houses in the European quarter. After 1902 malarial fever
began to decrease obviously, and since 1903 not a single new case of endemic
malaria has been found in Ismailia.

WORK IN ITALY.

The senior author has prepared the following consideration of the anti-
malarial work in Italy and this has for the large part appeared recently in the
Atti della Societa per gli Studi della Malaria, vol. 12, pp. 85-87, 1911:

“The marvelous work which has been done in the way of the reduction of
malaria in the Italian peninsula, largely under the direction of prof. Angelo
Celli, of the University of Rome, must meet the hearty admiration of the entire
world. The reports which have been published and the articles which have been
written about it, enthusiastic as most of them have been, still fail to produce
upon the minds of the readers the effect that a study of the actual conditions on
the spot brings about. We have introduced this information in this place for the
reason that effective as this work has been it has not been directed against mos-
quitoes themselves, but has been carried on almost entirely by two other methods
—mechanical protection and quininization. It was the good fortune of one of us
(Howard) to visit the Campagna, near Rome, in the summer of 1902 when the
work was practically in its infancy. The protection of the railroad stations and
of the peasants’ houses had begun, but the Campagna in those days was almost
deserted, agriculture was at a standstill, the peasants emaciated, their skins the
color of saffron, and the children from their emaciation and the characteristic
protuberant abdomens were pitiable objects. The whole of Italy was practically
malarious, and specially in its southern part and in the islands the mortality
ran from 0.400 to 3.000. By the work that has been done, in the same regions
SUCCESS IN ITALY 441

the mortality now runs from 0.050 to 0.800. In North Italy, in Piedmont and
Liguria, malaria is now practically non-existent, and the same may be said for
the province of Marche. In the Campagna itself, the mortality runs from 0.010
to 0.050, or at least this was the condition in 1908, and affairs have improved
since then. Again, it was Howard’s good fortune to visit the Campagna with
Celli in May, 1910. The metamorphosis in the intervening eight years was
simply miraculous. The Campagna has become populous; new buildings are
going up on every hand ; the peasants are robust, well fed, and obviously healthy ;
the children are fat, rosy, and full of life ; agriculture of the most intensive kind
is going on everywhere; and capital has come down from North Italy and the
price of land is rapidly increasing. Anopheles, however, is still breeding there,
and can be seen in the irrigating and draining ditches. The whole country is
reclaimed swamp, interspersed with small hills, with a tufa subsoil and volcanic
tock beneath. Mechanical measures first undertaken to protect the buildings
and huts with wire screens gradually reduced the percentage of infection with
malaria from 65 per cent to 12 per cent. Beyond this point for a time it seemed
impossible to reduce the disease, and then the quininization was begun.

“ Government supplies of quinine were placed at points in the custom-houses
where it could be readily had; poor people were given it for a time free; and
it was made palatable for the children by giving pellets under proper dosage a
heavy coating of chocolate, so that often babies cried for their medicine. Every
possible means was used for advertising and for distributing. Conspicuous signs
were posted along the roads and at the places of distribution. Small articles for
sale in boxes contained the government directions concerning quinine, and even
the covers of cheap cigarette packages were, and are, used for this purpose.

“Tn fact, a degree of ingenuity has been shown in this advertising which is
worthy of the most ingenious Yankee advertising agent. The cigarette package
cover bears the following statements (literally translated) :

“¢ OFFICIAL QUININE

- a preventative and curative remedy of unquestionable efficacy against malarial
ever.
“¢ OFFICIAL QUININE is sold to the public at very moderate prices by phar-
macists, drug-stores, and by private agencies that are licensed.
“Tt is sold at a special rate
by the

‘Maggazino di deposito’ of Turin to charity organizations, to the city, to
public and private persons who are obliged by law to furnish it gratuitously to
the poor and laborers.

“* Official quinine for gratuitous admimstration
to the poor and laborers is prepared by the Central Military Pharmacy of Turin
in tablets of 20 centigrams each, sugared in the form of candy.

“* Official quinine for sale to the public

is prepared by the Central Military Pharmacy of Turin in tablets of 20 centi-
grams each, enclosed in small tubes of 2 grams each.’

“ Tt results from the universal use of quinine in the prescribed doses that the
percentage of malaria has been reduced to less than 4 per cent, and this per-
centage is maintained, although the mechanical protective means have been
practically abandoned. The straw huts are no longer screened, and of the houses
only the upper-story bedrooms. Door-screens have been abandoned. The whole
country is full of life and energy, and the richness of the soil is so great that in
a comparatively few years the Campagna will be supporting an enormous
population.
442 MOSQUITOES OF NORTH AMERICA

“ Celli and his colleagues and supporters have the respect and affection of all
the inhabitants of the Campagna, and the wonderful work which their eminent
knowledge and great energy have accomplished is a model for other nations.”

The Italian Society for the Study of Malaria, under whose auspices this
magnificent work was done, was founded in July, 1898, by Angelo Celli, Giustino
Fortunati, and Leopoldo Franchetti. In “ Malaria, Internationales Archiv,”
for October, 1908, Professor Celli reviews the work of the Societa per gli Studi
della Malaria, and gives a summary of its results in these ten years which should
be published here:

“1. Has confirmed and perfected the new mosquito-malarial theory of Ross;

“2. Has contributed new facts to the etiology, pathology, clinic, and therapy
of the malarial infection;

“3. Has thoroughly studied the epidemiology of malaria according to the new
theory, disclosing the agreements and lacune which have yet to be filled up ;

“4. Has improved the prophylaxis of malaria and has introduced into practice
the new mechanical prophylaxis based on the defense of the habitation and the
person from the bites of mosquitoes. This being a relatively expensive prophy-
laxis, the Society has occupied itself with improving the antiplasmodic pro-
phylaxis, making use largely of state quinine both for the most radical treat-
ment possible and for the prophylaxis of malaria;

“5. Thence it has promoted and defended legislation in state quinine and in
its gratuitous distribution to all the workers and to the poor living in malarial
localities—a legislation which has been already adopted by other nations ;

“6. In order to render possible this prophylaxis and to prolong the treatment
as long as possible, it has had prepared the quinine in its most agreeable form—
namely that of comfits and chocolates, the latter containing tannate of quinine,
which has little taste and is better tolerated by children, and by those adults who
cannot tolerate the ordinary quinine salts ;

“7, With the propaganda of the facts and popular hygienic education, it has
helped to organize the new national campaign against malaria ;

“8. The results have been that since 1902, when the law on state quinine was
promulgated, while the consumption of quinine has been yearly increasing, the
mortality from malaria has, on the contrary, diminished almost three-fourths
throughout Italy (from 16,000 to about 4000 deaths yearly) ; and in the Army,
Custom-House offices and in some Communes, where the new laws have been
better applied, the morbidity from malaria has greatly diminished ;

“9. With the above-mentioned prophylaxis, eventually combined with the
mechanical one, people can finally live and dwell in places which formerly they
had to fly from, owing to the danger of malarial fevers ; and consequently to-day
one can better and more regularly carry out the hydraulic and agrarian sani-
tation.

“10. Our Society has endeavoured also to improve the execution of this, and
of the relative laws, because by means of the agricultural and agrarian trans-
formation of the land and colonization, rather than by the destruction of mos-
quitoes (a thing impossible to be done by us on a large scale), one can and must
proceed to the definite liberation of the territory from malaria.”
INDIA 443

WORK IN OTHER PARTS OF THE WORLD.

Active and well-organized anti-malarial work is being carried on in many
places in the tropics. An effort has been made to establish an anti-malarial
league in Greece which has the support of wealthy people and of the nobility of
several countries, but, aside from Italy, in practically none of the well-settled
countries in temperate regions has any work of importance been done, even in
regions whose development is distinctly held in check by this disease.

IN INDIA.

The government of India has never been able to carry out broad concerted
measures, although most important investigations have been carried on in that
country. It was decided to convene a conference to examine the whole question
and to draw up a plan of campaign for the consideration of the general govern-
ment and of the local governments. This conference assembled at Simla on
October 11, 1909. In the resolution which brought about the call it is pointed
out that the actual death-rate in India from malaria is five per thousand ; that
this represents about 1,130,000 deaths, and, as mortality in malarial fever is ordi-
narily low, a death-rate of even five per thousand indicates an amount of sick-
ness, much of it preventable, which clearly calls for the best efforts that govern-
ment can make to diminish it. An editorial in the Journal of Tropical Medicine
and Hygiene for September 15, 1909, in speaking of this resolution and the pro-
posed conference, anticipates that nothing will come out of the movement. It
says, “'To those, however, who have read many similar resolutions, and have,
perhaps, acted on committees of the sort, the solemn rigmarole, with its char-
acteristic touch on the ‘ prohibitive costs of attempts to extirpate the mosquito,’
implies no more than an expedient to stave off the dreaded day when public
opinion will force the Government of India to act instead of talk on this really
and literally vital question.”

The report of the conference as given in Nature, November 5, 1909, indicates
that many important addresses were made, including one by Colonel Leslie, the
Sanitary Commissioner of the government of India, and others by such well-
known workers as Major James and Captain Christophers of the Indian Medical
Service. Colonel Leslie advocated quinine prophylaxis. Major James intro-
duced a discussion upon the distribution of malaria in India and advocated a
general investigation in every province, similar to that which Captain Christo-
phers made in the Punjab. Quite in the line of prophecies of the editorial in
the Journal of Tropical Medicine and Hygiene, Major White, of the Indian
Medical Service, stated that he considered the recommendations of past malaria
conferences are costly, and almost prohibitively so if undertaken annually, and
contended that more should be done with the propagation of fish which prey
upon mosquito larve. At the termination of the conference various conclusions
and recommendations were drawn up under the following main headings :

(1) Scientific investigation ; (2) The agency by which investigation should
be made; (3) Practical measures, including (a) extirpation of mosquitoes, (b)
quinine treatment and prophylaxis, (c) education, and (d) finance.
444 MOSQUITOES OF NORTH AMERICA

THE UNITED STATES.

In the United States, it is sad to relate, almost nothing has been done in the
way of an active campaign against malaria alone, even in restricted localities.
It is true that extensive work has been done against mosquitoes, but in the most
of these cases the incentive does not seem to have been to better the health of the
people or to stamp out malaria. We have shown that in the New Jersey work
the item of personal comfort is concerned and that of the enhanced value of real
estate and the enhanced taxable value of land to the community, but the main
fight there is conducted against mosquitoes that have no relation to disease.
We have shown also that the fight against mosquitoes in the marsh lands back
of Brooklyn was financed by a wealthy man whose immediate motive was to keep
his race horses in better condition by preventing the annoyance of them by mos-
quitoes. In different communities there have been intelligent and up-to-date
citizens who have made strong efforts to start anti-malarial campaigns, but they
have not succeeded, through indifference on the part of city councils or other
bodies controlling public funds. Many health officers themselves have seemed
indifferent on this subject. In some localities citizens’ associations, civic im-
provement societies and women’s clubs have made efforts to improve the situa-
tion. Good work was done by such an organization in South Orange, New
Jersey, and instances of this kind are scattered here and there at very long in-
tervals over the country, but these efforts as a rule were spasmodic and only
temporary in their effects.

One of the best pieces of work with a direct anti-malarial bearing that has
been carried on in this country and that was begun at an early date was
started on Staten Island under Doctor Doty, the health officer of the port of
New York. The following account is largely taken word for word from a letter
received from Doctor Doty, but it can not be directly quoted on account of occa-
sional necessary alterations of the verbiage of a personal letter.

Staten Island, lying in New York harbor, had had a rather unenviable reputa-
tion on account of the great number of mosquitoes present and the continued
presence of malaria. It was largely on account of the latter condition that
Doctor Doty began his investigation in 1901. He soon found that there were
two factors to deal with, namely the inland mosquitoes and the salt-marsh
mosquitoes.

In the extermination of the inland mosquitoes, the section of Staten Island
which was known to contain many cases of malaria both in the acute and
chronic forms was selected for experimental work. This section consisted of a
basin of lowland about a mile square containing about one hundred small
dwelling houses some distance apart. Within its boundaries were a large num-
ber of stagnant pools varying in size from ten feet in diameter to an acre or
more in area. A house-to-house visit showed that at least 20 per cent of the
inhabitants of this district were suffering with some form of malaria, and in
the immediate vicinity of every house were found typical breeding-places in the
shape of old tinware, rain-water barrels, cisterns, cesspools and ground depres-
sions, many of which contained larve. For the purpose of detecting the pres-
WORK ON STATEN ISLAND 445

ence of adult Anopheles, glass tubes fitted with cotton plugs were distributed
among the occupants of these houses with the request that the mosquitoes found
in the house at night be captured and placed in the tubes. In the collections
were found many Anopheles. These were particularly numerous in tubes com-
ing from a small group of houses. In one of the latter was found a family con-
sisting of five persons all of whom showed the acute or chronic form of malaria.
Doctor Doty himself secured live mosquitoes from the interior of this house.
On the first evening five were captured, and all but one were Anopheles. On the
second evening twenty-two were collected, and of these more than one-half were
Anopheles. In a house on the opposite corner was found a patient suffering
from an acute attack of malaria.

In the beginning considerable difficulty was found in detecting the breeding-
places of the Anopheles, but this became easier as the inspections became more
thorough. For instance, in a group of two or three houses close together a num-
ber of Anopheles were captured, but their breeding-place could not be found for
some time. Finally in the back yard of one of the houses, overgrown with weeds,
was discovered a large metal receptacle with numerous Anopheles larve and
with many adults in the immediate vicinity. This receptacle was almost en-
tirely covered by underbrush. After this experience, the men employed learned
to make the closest possible search.

The island was then divided into small districts which were visited by a mos-
quito corps consisting of five men, one of whom was a sanitary police officer con-
nected with the New York City Department of Health. The equipment of the
mosquito corps consisted of a large wagon provided with spades, rakes, hose,
scythes and petroleum oil. A house to house inspection was made in each dis-
trict. House owners or tenants were required to remove from about the premises
all receptacles which might act as breeding-places, or to protect them. Rain-
water barrels and cisterns were covered with wire netting, all roof gutters were
repaired, and pools of water were covered with petroleum. In certain instances
orders were sent to the owners of property containing depressions in the soil to
fill these in or drain them. If these orders could not be enforced, the mosquito
corps returned every ten days or two weeks and applied more petroleum. Copies
of a circular of information were delivered so far as possible to each house on
Staten Island by police officers, and this educational campaign brought about
valuable cooperation on the part of the public.

In 1905 the details of this work were presented to the Department of Health
of the city of New York, and the city government granted an appropriation for
the drainage of the swamp land along the entire coast of the island. With the
aid of this appropriation, ditching was carried on somewhat in the same manner
in which it has been carried on in New Jersey. Down to the present time,
between eight hundred and one thousand miles of ditches have been dug. The
swarms of mosquitoes soon practically disappeared, window screens were dis-
carded, and meals were served upon the verandas of the hotels.

With the malarial and other inland mosquitoes, the work was carried on in
the manner above described, not only in the built-up portion of the island, but
446 MOSQUITOES OF NORTH AMERICA

also in the open spaces between the small and scattered settlements. During
the past two years cases of malaria on Staten Island are becoming very
rare and for the past year Doctor Doty has been unable to secure any Anoph-
eles, whereas in the beginning of the investigation they were found almost
everywhere on the Island. The statistics of the Department of Health indicate
the decrease of malaria from 1905 on. Prior to 1905 malaria was not regularly
reported, but the number of cases was surely very much greater than that re-
ported in that year. Since 1905, however, they are stated to have been as follows:
1905, 33 cases ; 1906, 54 cases ; 1907, 4 cases ; 1908, 6 cases ; 1909, 5 cases.

The work of exterminating malarial mosquitoes has been necessarily slow,
as the area involved is considerable, the Island being about 16 miles long and
four to six miles wide, with large areas between the various towns. The popula-
tion probably is over eighty thousand inhabitants.

The expense of the operations down to 1910 was about $50,000 ; this of course
includes the expense of the extensive drainage operations in the salt marshes.
Doctor Doty, in addition to being the Health Officer of the port of New York,
is a Commissioner of Health of New York City, and carried out this work in his
capacity as a municipal officer and not as a State official.

There were some earlier and very much smaller pieces of work, which have
previously been described by one of us.

Dr. W. N. Berkeley, in the Medical Record of January 26, 1901, gave an
interesting account of a malarial outbreak in a small town near New York City
during the summer of 1900. Around a large pond in the vicinity of the town four
or five cases had developed in August. The first case was that of a coachman
who had caught malaria elsewhere and had relapsed. From his quarters
in a long row of stables on one side of the pond the infection had been passed
along to other stablemen and servants on the same side, to the distance of a
quarter of a mile from the original site; a quarter of a mile in another direc-
tion, across the pond, one other case appeared in a small child. Dr. Berkeley went
to the town and discovered that Anopheles quadrimaculatus was fairly abundant
in every bedroom of that area in which proper search was made. The breeding-
places seemed to be segregated pools at the end of the pond (the pond itself con-
tained fish) and post-holes and excavations. These last were numerous, as many
buildings were going up. The following practical measures were adopted: (1)
Extermination of all the Anopheles found in houses by a party of men sent out
for the purpose, followed by a systematic introduction of screens in windows
and doors; (2) filling in of the smaller breeding-places and the drainage of
the pond; (3) the protection of every malarious patient by netting and other-
wise from the bite of mosquitoes, so long as he had malarial parasites in his
blood. The results were as prompt as they were gratifying. Not a single new
case of malaria developed ; Anopheles disappeared entirely from houses where
it had been common, and Cwlea was greatly diminished in numbers.

It will thus appear that, considering the economic loss existing in the United
States through malaria, nothing like the competent work has been done that
should have been done within the territorial limits of the United States them-
MOSQUITO EXTERMINATION SOCIETY 447

selves. The United States government has done admirable work in Cuba, for
another people, and it has done excellent work in the Isthmian Canal Zone, but
in its own home territory it has done nothing. State governments have done
almost nothing, if we except the drainage work done in New Jersey. Malaria
campaigns have been local and on the whole very unsatisfactory.

The same comparative indifference holds in other countries, and often even
where work is begun under good auspices and with excellent indications, it has
failed of securing the best results. Major C. E. P. Fowler, R. A. M. C., in his
report on malarial investigations in Mauritius, 1908, points out that on that
Island the great fault has been in non-attention to small details, as for instance
in dealing with neglected surface water such as is found in the small ditches
along roadsides, in field drainage channels and in holes in the ground, and fail-
ure in keeping up the larger work already carried out. He states that no
forethought seems ever to have been expended on keeping the work already car-
ried through in proper working order. Where drains or ditches had been laid
down only a few months previously he found them time after time choked with
vegetation and forming excellent breeding-places for Anopheles. The same
thing applied to rivers: the government had cleared them, but it seems to have
been nobody’s business to keep them clear. According to this report, there seems
to be a general impression among all classes of people, not only in Mauritius, that
to carry on anti-malarial work means the outlay of vast sums. People prefer to
sit idle and complain that they have not the means to carry out the work. He
shows that a few gangs of men can do a great deal in the way of ridding a district
of breeding-grounds, and that their employment does not imply a heavy outlay.

It is true that even where work is not directed specifically against malaria, but
against the mosquito nuisance, the breeding-places of Anopheles are for the most
part disposed of, and they are prevented from breeding, together with the other
species of mosquitoes, and for this reason a little space will be devoted to some
of the productive efforts which have been made in the United States aside from
those which have already been considered at some length.

In the early days of anti-mosquito work in this country, 1901 and 1902, the
rather rare citizens who appreciated the situation and who did their best to stir
up their communities to organized effort should be mentioned, as far as this has
not been already done. Among them we have specifically in mind, Dr. Albert F.
Woldert, of Philadelphia, and later of Texas; Dr. Henry Skinner, of Phila-
delphia; Dr. H. A. Veazie and Dr. H. G. Beyer, and a little later Dr. Quitman
Kohnke, of New Orleans; Major Barton, of Winchester, Va.; Dr. W. S. Thayer,
of Baltimore ; Mr. Spencer Miller, of South Orange, N. J.; Dr. W. F. Robinson,
of Elizabeth, N. J.; Dr. J. W. Dupree, of Baton Rouge. We have found it un-
necessary to mention any entomologists in this list, and of course since those
early days nearly every economic entomologist has become an apostle. After
1902 the ranks became greatly increased and at the present time conditions are
being bettered, although still there is no large well-organized campaign directed
solely against malaria.
448 MOSQUITOES OF NORTH AMERICA

An important step forward was taken in 1903 in the formation of the Ameri-
can Mosquito Extermination Society, in which W. J. Matheson, of New York,
the president, and Henry Clay Weeks, also of New York, the secretary, were
the leading movers. This Society, in which nearly all persons actively interested
in the mosquito crusade became interested, was started for the purpose of
educating the public, bringing about legislation, and of securing cooperation
and interchange of ideas. It held its first anti-mosquito convention December
16, 1903, in New York City. The convention was called to order by Mr.
Henry Clay Weeks, as acting chairman, who made some introductory remarks,
after which officers were elected. The following papers were read:

“ How a State Appropriation may be Spent,” by John B. Smith.

“ What a Rural Community can do,” by Walter C. Kerr.

“ The World-wide Crusade,” by L. O. Howard.

“ Does Extermination Exterminate Mosquitoes? ” by W. J. Matheson.

a on Extermination Work at Morristown, New Jersey,” by John

aflin.

“The Extermination and Exclusion of Mosquitoes from our Public Insti-
tutions,” by P. H. Bailhache, Surgeon, U. S. Public Health and
Marine-Hospital Service.

“ Government Antimosquito Work,” by Dr. J. C. Perry.

“The Sphere of Health Departments,” by Dr. E. J. Lederle.

“The Hxactness of Proofs of Transmission of Malaria by Mosquitoes,” by
Dr. W. N. Berkeley.

“The Long-Distance Theory,” by Spencer Miller.

if ee oie of Reclaimed Swamp Lands for Agricultural Uses,” by Milton

itney.

imoetet Work in Havana,” by Col. W. C. Gorgas, U. S. A.

“ How the Law should Aid,” by Paul D. Cravath.

“ New York State’s Part in Mosquito Extermination,” by E. P. Felt.

“ What the General Government should do,” by F. C. Beech.

“ Mosquito Engineering,” by Henry Clay Weeks.

s a es of the Department of Health, New York City,” by Henry C.

eeks.

Following this meeting, a somewhat elaborate organization was perfected,
including a general advisory board and an advisory board of entomologists.
The proceedings of the convention were published in pamphlet form and were
distributed free of charge. A mosquito brief was published as a folder giving
mosquito information. In November, 1904, Bulletin No. 1, of the Society was
published, which contained in condensed form an account of the work which had
been done in the meantime. Bulletin No. 2 contained a report of the presi-
dent and secretary to the Executive Council, published September 26, 1905,
and in 1906 was also published a year-book for 1904-1905 which contained the
proceedings of the second annual convention of the organization. These pro-
ceedings contained a number of valuable addresses, some of which may be
mentioned :

“ Diversities among New York Mosquitoes,” by E. P. Felt.

“ Mosquito Extermination in New Jersey,” by John B. Smith.

“ Extermination and Dissection of Mosquitoes,” by M. J. Rosenau, of the
U. 8. Public Health and Marine-Hospital Service.
MINOR WORK 449

. Mosquito Extermination in New York City,” by Thomas Darlington.
: The Mosquito Question,” by Quitman Kohnke.
The Relation of Mosquito Extermination to Engineering,” by Cornelius
C. Vermeule.

The society continued its work, and justified its organization. In 1907,
however, it was deemed by the officers of the society that the objects of its exist-
ence could well be taken over by the National Drainage Association, which had
been recently formed and which placed among its most prominent motives
the idea of securing government action in reclaiming the marshes and swamps
of the country. It was decided that the society should retire from its field of
work and leave the same to the national government, to State, and other author-
ities, and to individuals.

In 1903-1904 work against mosquitoes was undertaken by the State Ento-
mologist of Connecticut, Dr. W. E. Britton, who made careful mosquito surveys
over the whole State and who published in his annual report for 1904 a careful
and well-illustrated article devoted to showing how the mosquito nuisance can
be abated. Since that time some active work has been taken up. In 1906 the
Board of Health of Millburn township in New Jersey secured the services of Mr.
Weeks, and published a pamphlet entitled “ The Mosquito Nuisance in Millburn
Township and How to Abate It.”

At Worcester, Mass., an interesting crusade was begun early under the direc-
tion of Dr. William McKibben and Prof. C. F. Hodge. In Michigan work was
carried on upon the campus of the Michigan Agricultural College. In Connecti-
cut work was earlier done at Pine Orchard and Ansonia, as well as at Bridge-
port, Branford, Fairfield and Hartford; and in Maine at Old Orchard Beach.
Excellent work was also done at a very early date at Lawrence, Long Island,
largely against malarial mosquitoes, under the auspices of the Board of Health
working with an appropriation of $1000 and with a privately contributed fund
of $1678.54. A small crusade was also carried on at an early date under the
auspices of the civics committees of the Twentieth Century Club at Richmond
Hill, Long Island. In the Southern States the Boards of Health at Atlanta
and Savannah began work in 1903 and certain regulations were enforced. At
Talladega, Ala., work was also begun in the same year. The excellent work done
at Morristown, N. J., under an improvement society in 1903 should not be
forgotten.

The foregoing examples show what it is possible to do in the way of abating
the mosquito nuisance and we trust the recounting of them will stimulate many
to undertake the work. The matter is generally surprisingly easy when once
the problem is well understood. The most important point to determine first of
all is the exact species of mosquito concerned, for each species requires radically
different treatment, as will have been evident to the reader from the fore-
going. The principal object of the present work, therefore, is to elucidate, as
far as at present is possible, the differences between all the known species in our
region, not only the noxious species, but the far more numerous relatively
harmless kinds, as well as the few actually beneficial ones. To this subject the
following volumes are devoted.
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INDEX.

 

Abdomen of mosquito, adult female, 67-69

Abdomen of mosquito, adult male, 69-71

Abdomen of mosquito larva, 88-91

Abdomen of mosquito pupa, 102

Abdominal segments of mosquito, 67

Abdominal vestiture of mosquito, 74

Ablabesmyia pilosella, swarming habits, 128

Abundance of mosquitoes, 132-135

Acartomyia zammittii. (See Aédes zam-
mittii.)

Acetabula of labium of mosquito, 41

Achromaticus, parasites of bats, 189.

ae sulcatus, enemy of mosquito larve,
164.

Acini of salivary glands of mosquito, 77

Acini of salivary glands of mosquito, histol-
ogy, 81-82

Activity, time, in mosquitoes, 118

Adinia, enemies of mosquitoes, 409

Aichmea, water in plant, breeding place of
mosquitoes, etc., 221

ae larva, modifications of structure,
9

.Aédeomyia, male genitalia, 70

Aédeomyia, shaft of antenna, 27

Aédeomyia, spermatheca, 79

Aédeomyia squamipennis, scales of femora,
74

Aédeomyia squamipennis, vestiture of wings,
73

Aédes, ciliation, lateral, of abdomen of male,
69

Aédes, claws, 64, 65

Aédes eggs, hibernation and hatching, 144-
145

Aédes eggs readily obtained in captivity, 185

Aédes, eighth segment and its tergal and ster-
nal plates in female, 68

Aédes, food of larve, 151

Aédes, food preferences, 107

Aédes, habits of larve, 146-147

Aédes, hatching of eggs of species breeding in
tree-holes, 145

Aédes, humpbacked appearance, 205

Aédes larve, attitude at surface film, 153

Aédes larve, feeding modes, 153

Aédes larve, habits of species which breed in
hollow trees, 147

Aédes larve in drinking water in small hotels
in South, 152

Aédes larve, prey of Corethra, 169

Aédes larve, prey of Psorophora, 151

Aédes larve, structural modifications, 93

Aédes larve, when to find them, 184-185

Aédes larve, where to find them, 184

Aédes, longevity, 119

Aédes, male genitalia, 70, 71

Aédes, mating habits, 129-130

Aédes, observations on larve by De Geer, 23

 

Aédes, observations on life-history by Klee-
mann, 23-24

Aédes, palpi, 53

Aédes, shaft of antenna, 26

Aédes, some species not easily determined
from adults alone, 181

Aédes, time of activity, 118

Aédes, tip of abdomen, cerci, 68

Aédes, wing vestiture, 72-73

Aédes abfitchii, longevity, 119

Aédes albonotata, male genitalia, 70

Aédes angustivittatus, escape from 16-mesh
wire screen, 364

Aédes atropalpus, breeding of two successive
generations in captivity, 114, 132, 185

Aédes atropalpus, habits of pupa, 155

Aédes atropalpus, time of activity, 118

Aédes calopus (see also Yellow-fever mos-
quito, Stegomyia fasciata and Stegomyia
calopus).

Aédes calopus biting corpses, 114

a ee breeding places, abolition, 388-
oO

Aédes calopus, cannibalistic habits, 152

Aédes calopus, carriage by railroads, 346, 347

Aédes calopus, carriage by ships and steam-
ers, 345-346, 347, 348-352

Aédes calopus, claws, 65

Aédes calopus, food difference of sexes, 113

Aédes calopus, food habits, 106-107

Aédes calopus, fungous disease, 158

Aédes calopus, hatching of eggs, essentially a
“tree-hole ” species, 145

Aédes calopus, host of Filaria demarquayi,
316

Aédes calopus, host of gregarines, 160

Aédes calopus, host of Herpetomonas algeri-
ense, 161

Aédes calopus, host of nematode parasite,
Mermis, 163-164

Aédes calopus in Havana, 429-430

Aédes calopus larve in receptacles of drink-
ing water, 152

Aédes calopus larve, locomotion, 153

Aédes calopus larve, prey of Lutzia bigotii,
167

Aédes calopus larve, prey of Megarhinus sep-
tentrionalis, 169

Aédes calopus, longevity, 119

Aédes calopus, male genitalia, 70

Aédes calopus, mating habits, 126

Aédes calopus, musical note, 116

Aédes calopus not proven to be a carrier of
dengue fever, 304-305

Aédes calopus on Tortugas Islands, 342

Aédes calopus, original home, 294-298

Aédes calopus originally probably a tree-hole
breeding species, 288, 286

489
490

Aédes calopus, position of sexes during copu-
lation, 121, 122, 128

Aédes calopus, possible hereditary transmis-
sion of virus of yellow fever, 247-249

Aédes calopus, spread to new habitats, how
effected, 345-352

Aédes calopus, time of activity, 118

Aédes calopus, transmitter of filariasis, 315

Aédes calopus, transmitter of yellow fever,
Finlay’s work, 242

Aédes calopus, yeasts found therein, 158-159

a pees eggs and their hatching,
1

Aédes canadensis larve, appearance after
heavy summer rains, 144

Aédes canadensis, time of activity, 118

Aédes cantans, abundance on Wicken Fen, 417

Aédes cantator, distribution and seasonal ap-
pearance in New Jersey, 400

Aédes cantator, effect of bite, 319:

Aédes cantator, migratory habits, 340-341, 344

Aédes curriei, claws, 65

Aédes cyanescens, transportation in convey-
ances and on backs of horses, 348

Aédes fitchii, longevity, 119

Aedes ast, swarming and mating habits,

Aédes fluviatilis larve inhabiting sea-water
and fresh water, 150

Aédes fulvithoraz, claws, 65

Aédes fulvus, thoracic vestiture and integu-
mental spots, 73

Aédes fuscus, claws, 65

Aédes fuscus eggs and their hatching, 144

Aédes fuscus larve, appearance after heavy
summer rains, 144

Aédes fuscus, male genitalia, 70

Aédes fuscus, palpi, 53

Aédes mediovittata, tree-hole breeding spe-
cies, habits, 283

Aédes nemorosus, food preferences, 107

Aédes nemorosus, occurrence of larve in mid-
winter, 154

aa form of Aédes teniorhynchus,

2

Aédes niger, migratory habits, 342, 344

Aédes quaylei, migratory habits, 344

Aédes riparius, time of activity, 118

Aédes scutellaris, partial development of Fi-
laria bancrofti therein, 315

Aédes sollicitans, distribution and seasonal
appearance in New Jersey, 400

Aédes sollicitans, effect of bite, 319

Aédes sollicitans, host of Agamomermis culi-
cis, 162-163

Aédes sollicitans in wild cherry blossoms, 111

Aédes sollicitans larve inhabiting sea-water
and fresh water, 150

Aédes sollicitans larve, prey of shore birds,
179

anne Joni, migratory habits, 340-341,

Aédes sollicitans, mistaken inference from
occurrence in New Orleans, 388

Aédes sollicitans, prompt hatching of eggs
after immersion, 144

Aédes sollicitans, stomach contents, 114

Aédes sp., respiratory system of larva, 89-91

 

INDEX

Aédes spenceri, flight against wind, 342

Aédes spenceri, food habits, 107

Aédes spenceri, frequenting willow catkins,
112

Aédes spenceri, longevity, 119

Aédes spenceri, swarming and mating habits,
130-131

Aédes squamiger, migratory habits, 344

Aédes squamiger, wing vestiture, 73

Aédes stimulans, longevity, 119

Aédes stimulans, time of activity, 118

Aédes stimulans visiting flowers of Smilax
herbacea and BS. hispida, 111

Aédes sylvestris, claws, 64, 65

Aédes sylvestris, male genitalia, 70

Aédes sylvestris sucking nectar from flowers
of Solidago canadensis, 8. juncea, and 8.
lanceolata, 111-112

Aédes teniorhynchus, distribution and sea-
sonal appearance in New Jersey, 400

Aédes teniorhynchus, migratory habits, 340-
341, 344

Aédes teniorhynchus, salivary and poison
glands and ducts, 49-50

Aédes triseriatus, host of mites, 173

Aédes triseriatus larve, locomotion, 153

Aédes triseriatus larve, prey of Calodiazesis
barberi, 151

Aédes triseriatus, tree-hole breeding species,
habits, 283

Aédes varipalpus, copulatory attitude, 128

Aédes walkeri, male genitalia, 70

Aédes willcocksi, swarming of males, 129

Aédes zammittii larve occurring in sea-wa-
ter, 150

Aédes zammittii, mating habits, 131

Aédogonium, food of Anopheles quadrimacu-
latus larve, 150

Aigialitis semipalmata, enemy of mosquitoes,

AXquatorial band of corpuscle with Plasmo-
dium malarie, 191

4ischna as an enemy of mosquitoes, 167

4ischna heros as an enemy of mosquitoes, 166

AMstivation and hibernation of mosquitoes,
119-120

Aistivo-autumnal malaria, caused by Plasmo-
dium falciparum, 189, 191

Agamodistomum martiranoi, parasite of Ano-
pheles maculipennis, 162

Agamomermis culicis, parasite of mosquitoes,
162

Agamomermis sp., parasite of Culex nemora-
lis, 162

Agouti, host of yellow-fever mosquito, 261

AGRAMONTE on oviposition of yellow-fever
mosquito, 279-280

Agriculture and malaria, 323-324

Agriculture, loss from mosquitoes, 330

Agrionid larva capturing Culex larva at sur-
face of water, 167

AIKEN, Rev. JAMEs, on diurnal habits of Ano-
pheles, 211

Air cavity in cephalothorax of mosquito
pupa, 99-100

Air, ingorgement by mosquito at ecdysis, 104-
105

Alary muscle of mosquito, 77
INDEX

Alcohol, amyl, as diluent for petroleum used
as mosquito larvicide, 381

Alcohol, oil of lavender, and castor oil as pro-
tection against mosquito bites, 365

Aldrov_nda vesiculosa, enemy of mosquito
larve, 156

Alge as deterrents to development of mos-
quito larve, 418

Algez, food of Anopheles larve, 148, 230

Alge, spores as food of mosquito larve, 150

Alimentary canal and appendages of mos-
quito, histology, 80-83

Alimentary canal of mosquito, 75-79

Altitudes, high, and malaria, 235-236

Amblystoma opacum, enemy of Chaoborus,
176-177

Ammonia as remedy for mosquito bites, 376

Anablops, enemy of mosquitoes, 407

Anal cell of mosquito wing, 61

ae Oe a a enemy of mosquitoes,

Anaz junius, enemy of mosquitoes, 166

Animal enemies of mosquitoes, 159-179

Animal refuse, food of mosquito larve, 151

Animals, unicellular, food of Anopheles lar-
ve, 230

ANNETT, DuTToN and ELLiorr on swarming
of male Anopheles, 129

Anopheles adults, attractiveness of colors
thereto, 378

Anopheles adults, resting position, 205

Anopheles, estivation, 206-207

Anopheles, a male with abnormal mouth-
parts, 49

Anopheles, anatomy, internal, 75-83

Anopheles and courts of law, 352-354

Anopheles, bacterial enemy, 158

Anopheles, behavior towards certain colors,
216-218

Anopheles biting corpses, 114

Anopheles breeding in sea water, 224-229

Anopheles, breeding places, 218-224

Anopheles “ brigade ” in Havana, work, 430

Anopheles, cannibalistic habits, 152

Anopheles, carriage by winds, 214

Anopheles, carriage in stage coaches and rail-
way trains, 348

Anopheles, claws, 65

Anopheles, discovery by Grassi that this
genus alone transmits malarial parasite,
196

Anopheles, distance of flight, 212-216

Anopheles, diurnal and nocturnal habits, 209-
211

Anopheles, early stages, length, 231

Anopheles, effect of attack, 319

Anopheles eggs and their disposal, 143

Anopheles eggs, resistance to dessication, 231

Anopheles, empodium and claw, 67

Anopheles, feeding habits of female, 207-209

Anopheles, femora, 62

Anopheles larve, food, 148

Anopheles, food of larve, 229-230

Anopheles, flight against wind, 342

Anopheles, flight, distance, 212-216

Anopheles, generations, number, 232

Anopheles, habitats of larve of various spe-
cies, 148

33

 

491

Anopheles, habits of adults, 204-232

Anopheles, habits of larve, 229-230

Anopheles, habits of larve inhabiting brome-
liads, 148

Anopheles, hibernation and estivation, 119,
120, 206-207

Anopheles, hiding places, 118

Anopheles, hosts of Distomum, 162

Anopheles, immunity to malaria of individu-
als of various species, 204

Anopheles in Algeria, 438-439

Anopheles in Cyprus, 404-405

Anopheles larva, individual killed by Vorti-
cella, 161

Anopheles larva, modifications of structure,
91-92, 94

Anopheles larve as affected by larvicide of
Isthmian Canal Commission, 385

Anopheles larve, cannibalistic tendencies, 167

Anopheles larve, enemies in Mauritius, 170

Anopheles larve, enemies of Culex larve, 167

Anopheles larve, feeding, locomotion and
resting, 153

Anopheles larve, food, 150, 152, 229-230

Anopheles larve, habits, 229-230

Anopheles larve, hosts of intestinal worm,
163

Anopheles larve, prey of Gyrinide, 164-165

Anopheles larve, prey of Psorophora ciliata
larve, 168

Anopheles larve, prey of Ranatra fusca, 165

Anopheles larve, resistance to dessication,

231
Anopheles larve, suggestions for rearing
them, 184

Anopheles larve thriving among alge, 418

Anopheles larve, where to find them, 184

Anopheles, last tarsal joint, 63

Anopheles, lateral ciliation of abdomen of
male, 69

Anopheles, length of early stages, 231

Anopheles, longevity, 119

Anopheles, male genitalia, 70

Anopheles, mouth-parts of adult, 49

Anopheles, mouth-parts of larva, adaptation
to predaceous habit, 95, 96

Anopheles, musical note, 116, 211-212

Anopheles, nocturnal and diurnal habits, 209-
211

Anopheles, note or hum, 211-212

Anopheles, number of generations, 232

Anopheles, ormmatidia cf young pupa, 87

Anopheles on Staten Island, 445-446

Anopheles, palpi, 51-53

Anopheles, period between feeding and possi-
ble transmission of Plasmodium, 194

Anopheles, position of sexes during copula-
tion, 121, 128

Anopheles, prey of Lucius americanus, 408

Anopheles, resistance to dessication, of eggs
and larve, 231

Anopheles, respiratory trumpets of pupa, 102

Anopheles, salivary and poison glands and
ducts, 49-50

Anopheles, salivary pump, 50

Anopheles, scales and hairs, 71, 72

Anopheles, scutellum, 60
492

Anopheles, semidomestic and wild species,
205-206

Anopheles, shaft of antenna, 26

Anopheles, size of screen mesh for protection,
363

Anopheles, species that carry malaria, 202-204

Anopheles, spermatheca, 79

Anopheles, stridulating apparatus, 115

Anopheles supposed to be host of Distomum
globiporum, 162

Anopheles, swarming of males, 129

Anopheles, tarsi, 63

Anopheles, thoracic vestiture and integumen-
tal spots, 73

Anopheles, time of activity, 118

Anopheles, vestiture of abdomen, 74

Anopheles, vestiture of wing, 62

Anopheles visiting flowers of Mentha aqua-
tica, 111

Anopheles, wild and semidomestic species,
205-206

Anopheles albimanus abundant in settled re-
gions, 207

Anopheles albimanus breeding in brackish
water, 228

Anopheles albimanus, carriage by wind, 214

Anopheles albimanus, carrier of estivo-au-
tumnal and tertian malaria, 202, 204

Anopheles albimanus, carrier of filariasis, 315

Anopheles albimanus, feeding habits of fe-
male, 209

Anopheles albimanus found on vessels half
mile from shore, 273

Anopheles albimanus in Havana, 429, 430

Anopheles albimanus, resistance of larve to
dessication, 231

Anopheles albimanus, semidomestication, 205-

Anopheles albimanus, time of appearance at
night, 210

Anopheles albipes, diurnal habits, 211

Anopheles algeriensis, carrier of malaria, 204

Anopheles algeriensis, host of mites, 174

Anopheles annulipalpis at sea, 343

Anopheles annulipalpis, carriage by wind, 214

Anopheles annulipes, carrier of filariasis, 315

Anopheles annulipes, carrier of malaria, 202

Anopheles argyritarsis breeding in brackish

water, 228

Anopheles argyritarsis, carrier of malaria,
202, 204

Anopheles argyritarsis, feeding habits of fe-
male, 209

Anopheles argyritarsis, resistance of larve to
dessication, 231

Anopheles argyritarsis, time of appearance
at night, 210 .

Anopheles argyrotarsis [sic],
ships, 349-350

Anopheles barberi (see also Calodiazesis bar-
beri).

Anopheles barberi, male genitalia, 70

Anopheles barbirostris, carrier of malaria,
204

Anopheles barbirostris, “ wild” species, 206

Anopheles bellator, male genitalia, 70

Anopheles bifurcatus breeding in water of
peat cuttings, 417

carriage by

 

INDEX

Anopheles bifurcatus, carrier of filariasis, 315

Anopheles bifurcatus, carrier of malaria, 202

Anopheles bifurcatus deterred from breeding
by growth of Lemna arrhiza and L.
minor, 418

Anopheles bifurcatus, hibernation as larva,
120, 154, 207

Anopheles bifurcatus, mating habits, 129

Anopheles brasiliensis, diurnal habits, 210

Anopheles chaudoyei breeding in saline wa-
ter, 228

Anopheles chaudoyei, length of developmen-
tal period, 231

Anopheles claviger, discovery of malarial par-
asite in stomach, 196

Anopheles cohwsa, carrier of malaria, 202

Anopheles cohesa = Anopheles listoni, 202

Anopheles costalis breeding in sea water, 227-
228

Anopheles costalis, breeding places, 223

Anopheles costalis, carrier of filariasis, 315

Anopheles costalis, carrier of malaria, 202

Anopheles coustani, carrier of malaria, 202

Anopheles crucians breeding in brackish wa-
ter, 228

Anopheles crucians, carrier of estivo-autum-
nal but not of tertian and quartan ma-
laria, 203

Anopheles crucians, diurnal habits, 210, 211

Anopheles crucians, host of mites, 173

Anopheles cruzii, breeding places, 220-221

Anopheles crugii, carrier of malaria, 202

Anopheles cruzti, habits and food of larve,
230

Anopheles culifacies, carrier of malaria, 202

Anopheles culifacies, distance of flight, 213,
214

Anopheles culifacies, habitats of larve, 220

Anopheles culifacies, resting position of adult,
205

sae «tha culifacies, secretive habit of adult,
20

Anopheles eiseni, larval habitats, 219

Anopheles eiseni, undomesticated species,
206, 207

Anopheles formosaénsis, carrier of malaria,
202

Anopheles formosaénsis = Anopheles listoni,
202

Anopheles fuliginosus, carrier of malaria, 202
Anopheles fuliginosus, distance of flight, 218,
214

Anopheles fuliginosus, domesticity as com-
pared with other species, 206

Anopheles fuliginosus, larval habitats, 220

Anopheles funesta, carrier of malaria, 202

Anopheles grabhamii, claws, 65

Anopheles grabhamii, wing vestiture, 72

Anopheles hispaniola, carrier of malaria, 204

Anopheles hispaniola, resting position of
adult, 205

Anopheles intermedium, carrier of malaria,

Anopheles intermedium, time of appearance
at night, 210

Anopheles jesoénsis, carrier of malaria, 202

ane ee jesoénsis = Anopheles sinensis,
INDEX

Anopheles jeyporensis suspected of carrying
malaria, 202

Anopheles listoni, carrier of malaria, 202

Anopheles listoni, carrier of pernicious ma-
laria only, 203-204

Anopheles listoni, synonyms, 202

Anopheles ludlowit breeding in sea-water
pools, a carrier of malaria, 226-228

Anopheles ludlowii reported, probably eron-
ae as breeding in fresh water, 226-

Anopheles lutzii (cruzii), breeding places,
220-221

Anopheles maculipennis, abnormal mouth-
parts of a male, 44

Anopheles maculipennis, behavior towards
certain colors, 216-217

Anopheles maculipennis breeding in salty
water, 228

Anopheles maculipennis, carrier of all three
kinds of malaria, 202, 203

enna maculipennis, carrier of filariasis,

Anopheles maculipennis confined to Old
World, 6

Anopheles maculipennis deterred from breed-
ing by growth of Lemna arrhiza and L.
minor, 418

Anopheles maculipennis, early occurrence in
Ireland, 234

Anopheles maculipennis, host of Agamodis-
tomum martiranoi, 162

Anopheles maculipennis, host of Crithidia
fasciculata, 161

Anopheles maculipennis, host of Filaria ban-
crofti, F. perstans, and F. demarquayi,
316

Anopheles maculipennis, host of Filaria im-
mitis, 316

Anopheles maculipennis, host of hydrachnid
mites, 172-173

Anopheles maculipennis, host of mites, 174

Anopheles maculipennis, host of spirochete,
160

Anopheles maculipennis in peaty water and
near peat piles, 417

Anopheles maculipennis, larval habitats, 219

Anopheles maculipennis, mating habits, 129

Anopheles maculipennis, name incorrectly
used for American species, 6

Anopheles maculipennis, pitch of hum com-
pared with that of Culex pipiens, 212

Anopheles maculipennis unaffected by paw-
paw or castor-oil plants, 415

Anopheles maculipennis, yeast parasitic
therein, 158

Anopheles malefactor not known to carry
malaria, 204

Anopheles martini, carrier of malaria, 202

Anopheles mediopunctatum, time of appear-
ance at night, 210

Anopheles minutus, carrier of filariasis, 315

Anopheles nigerrimus, carrier of filariasis,
315

Anopheles nigerrimus, larval habitats, 219

Anopheles nigripes breeding in water of peat
cuttings, 417

 

493

Anopheles nimba, resting and flying position
of adult, 205

Anopheles occidentalis formerly known as
Anopheles maculipennis, 6

Anopheles paludis, carrier of malaria, 202

Anopheles paludis, host of mites, 173

Anopheles pharoensis, swarming of males,
129

Anopheles pseudomaculipes, carrier of ma-
laria, 202
Anopheles pseudomaculipes, time of appear-
ance at night, 210
eam IES pseudopictus, carrier of filariasis,
15

Anopheles pseudopictus, carrier of malaria,
204

Anopheles pseudopunctipennis, carrier of ma-
laria, 204

Anopheles punctipennis, cannibalism of lar-
ve, 167

Anopheles punctipennis, color preferences,
218

Anopheles punctipennis, diurnal habits, 210-
211

Anopheles punctipennis, does it carry ma-
laria?, experiments and data, 202-203

Anopheles punctipennis, host of mites, 173

Anopheles punctipennis, larval habitats, 219,
221-222

Anopheles punctipennis, swarming habits,
126-128

Anopheles punctipennis, swarming period as
bearing on number of generations, 232

Anopheles pursati, carrier of malaria, 202

Anopheles quadrimaculatus breeding in
brackish water, 228
Anopheles quadrimaculatus breeding in

places inaccessible to fish, 412

Anopheles quadrimaculatus, cannibalism of
larve, 167

Anopheles quadrimaculatus, carriage in ve-
hicles, 348

Anopheles quadrimaculatus, carrier of ma-
laria, experiments, 202-203

Anopheles quadrimaculatus, carrier of ter-
tian and quartan but not of estivo-au-
tumnal malaria, 203

Anopheles quadrimaculatus, food of larve, 150

Anopheles quadrimaculatus formerly known
as Anopheles maculipennis, 6

Anopheles quadrimaculatus, host of mites,
1738, 174

Anopheles quadrimaculatus in small town
near New York City, 446

Anopheles quadrimaculatus, larval habitats,
219, 221-222

Anopheles quadrimaculatus, lengths of egg,
larval, and pupal periods, 231

Anopheles quadrimaculatus, pitch of hum
compared with that of Culex pipiens, 211

Anopheles quadrimaculatus, prey of Emesa
longipes, 172

Anopheles quadrimaculatus, prey of Ery-
themis simplicicollis, 167

Anopheles quadrimaculatus, resting position
of adult during hibernation, 205

Anopheles quadrimaculatus sitting,
tangled, on spider web, 176

unen-
494

Anopheles rossi breeding in brackish water,
227, 228

Anopheles rossi, carrier of filariasis, 315

Anopheles rossi, distance of flight, 213, 214

Anopheles rossi, domesticity, 206

Anopheles rossi, larval habitats, 219, 220

Anopheles sinensis, carrier of tertian and
quartan malaria only, 204

Anopheles sp., carrier of filariasis, 315

Anopheles stephensi breeding in salt water,
228

Anopheles stephensi, distance of flight, 213

Anopheles stephensi, larval habitats, 220

Baas Med superpictus, carrier of malaria,
2

Anopheles superpictus, resting position of
adult, 205

Anopheles tarsimaculata breeding in brackish
water, 228

as tarsimaculata, carrier of malaria,
2

Anopheles tarsimaculata = geographic form
of Anopheles albimanus, 228

Anopheles theobaldi, carrier of malaria, 204

Anopheles turkhudi, carrier of malaria, 202

Anopheles turkhudi, eggs, 143

Anopheles vincenti, carrier of malaria, 202

Anophelines, histology of salivary glands, 81,
82

Ant, disgorged food eaten by mosquito, 109-
110

Antenne of mosquito adults, 26-36

Antenne of mosquito larva, 84-85

Antenne of mosquito pupa, 101

Antenne, scale covering of certain joints in
mosquito, 74

Antennal sense-organ in Culicids, 29-34

Anterior cross-vein of mosquito wing, 61

Ante-scutellar space, vestiture, in mosquito,
73

ee ee vociferus, enemy of mosquitoes,

7

Anus of mosquito adult, 76

Anus of mosquito larva, 90

Aorta of mosquito, 77

Aphredoderus, enemy of mosquitoes, 406

Apodemes of rostrum of mosquito larva, 85-
86

Appendages, basal, of male genitalia of mos-
quito, 70

Appendages of “ ninth segment ” of mosquito
pupa, 102

Aquatic animalcules, food of mosquito larve,
150

Aquatic birds as mosquito destroyers, 178-
179

Arctic mosquitoes, abundance and ferocity,
185-139

ARNOLD, Dr. F., on mosquito bars or canopies
for indoors and out-of-doors, 362-363

Asexual cycle of malarial organism, defini-
tion, 189

Ashes, wood, effect on eggs of yellow-fever
mosquito, 281, 290-291

Asilide, reported enemies of mosquitoes, 172

“ Aspiratory vesicles” of Giles in mosquito,

78
Attraction of mosquitoes to sounds, 116-117

 

INDEX

Atypical fever, name for disease caused by
Plasmodium falciparum, 191

AuBERT, Not and Stuonp. (See Simond, Au-
bert and Noé.)

“Auditory capsule” in antenna of mosqui-
toes, 34

Auxiliary vein of wing of mosquito, 60, 61

Axillary cell of wing of mosquito, 61

Axillary cords of mosquito, 58

Azolla, deterrent to mosquito larve, 420-421

Bacillus icteroides and yellow fever, 241-242

Bacillus icteroides identical with bacillus of
hog cholera, 242

Bacillus icteroides, supposed connection
with yellow fever disproved, 243

Bacteria, are they exterminated from water
containing mosquito larve?, 152

Bacteria, food of mosquito larve, 150

Bacterial enemies of mosquitoes, 157-159

Batrour, Dr. ANDREW, on conveyance of
Aédes calopus and Culex quinquefascia-
tus by steamers, 348

Batrour, Dr. ANDREW, on mosquito-control
work along Blue Nile in Egypt, 428

Bamboo, water-filled ends, breeding places of
mosquitoes, 149

Banana, food of yellow-fever mosquitoes, 270

Banana, water in folded leaves, breeding
place of Aédes calopus, 286

Bancroftia, claws, 65

Bancroftia eggs and their disposal, 144

Bancroftia, fourth tarsal joint, 63

Bancroftia larva, modifications of structure,
93, 94, 95

Bancroftia larve, where to find them, 184

Bancroftia, male genitalia, 70

Bancroftia, palpi, 53

Bancroftia, vestiture of mesonotum, 74

Bancroftia fascipes, palpi, 53

Bancroftia fascipes, vestiture of wing, 73

Bancroftia signifer eggs and their disposal,
143

Bancroftia signifer, hibernation as larva, 120,

Bancroftia signifer larve, prey of Ca@lodi-
azesis barberi, 151

BANKS, CHARLES S., on diurnal habits of yel-
low-fever mosquito, 263

Bangs, C. S., on food-habits of larve of
Aédes calopus, 287

BARBER, HERBERT S., discovery of an Aédes
calopus in woods, 259

“ Barrigudo.” (See Girardinus caudimacula-
tus.)

Basal cross-vein of mosquito wing, 61

Basil plant (see also Ocimum viride).

Basil plant, alleged deterrent to mosquitoes,
416

Bat, Pipistrella europa@i, host of Lecithoden-
drium ascidia, 162

Bed nettings against mosquitoes, 360

Batrachian enemies of mosquitoes, 176-177

Batrachians, protozoan parasites, 159

Bats, enemies of mosquitoes, 179

Bats, hosts of Achromaticus and Polychromo-
philus, 189

Bats, hosts of yellow-fever mosquito, 261
INDEX

Brtcu, Mr., on good effect of drainage work
in freeing land from mosquitoes, 392

Beneficial functions of mosquito larve, 152

BENTLEY, CHaRLEs A., on utilization of duck-
weeds as deterrents to breeding of mos-
quitoes, 419-420

Bergamot oil as protection against mosquito
bites, 367

Berry, Past ASSISTANT SuRGEON, on Mimms
Culicide as a fumigant against mosqui-
toes, 370-371

BrEYER, POTHIER and PARKER.
Beyer and Pothier.)

Bibiocephala, mouth-parts, 46

Bibio, first spiracle and epimerum, 57

Bibio, mesoepisternum, 58

Bibliography of mosquitoes, 451-488

Billbergia, water in plant, breeding place for
mosquitoes, etc., 221

Binucleata, 189

Bird enemies of mosquitoes, 177-179

Birds and malaria, researches of Dr. Ronald
Ross, 195-196

Birds, bosts of Proteosoma, 189, 196-197

Birds, malarial disease transmitted by Culex
quinquefasciatus, 202

Birds, protozoan parasites, 159-160

BisHor, Wo. H., on cactus paste as mosquito
larvicide, 381

Bites of mosquitoes, effect, 316-319

Bites of mosquitoes, relative susceptibility of
different persons thereto, 318-319

Black-spot areas of rostrum of mosquito
larva, 85

Bladderwort, Genlisea ornata, enemy of mos-
quitoes, 156

Bladderworts (Utricularia), enemies of mos-
quitoes, 156

BLancuarp, nomenclature of the species of
Plasmodium, 189

Blepharocera, mouth-parts, 47

Blood injections, yellow fever produced ex-
perimentally thereby, 244

Boats as carriers of mosquitoes, 345-352

Bombylius, structure of hypopharynx, 40

“ Bourses ventriculaires ” of mosquito, 77

Boyce and Lewis on increase of bacteria in
water containing mosquito larve, 152

Boyce, Siz Rusert, on original home of yel-
low fever, 295-296

BRAKELEY, J. TURNER, on Mosquitoes and cas-
tor-oil plant, 414

Breeding house for bats, to encourage their
work against mosquitoes, 179

Breeding of mosquitoes in sewers, preven-
tion, 390-391

Breeding places of mosquitoes, 146-150

Breeding places of household mosquitoes, abo-
lition, 388-390

Bresia, water in plant, breeding place for
mosquitoes, 221

Bromeliads, destruction, in control of mos-
quito larve, 391

Bromeliads, water in plant, breeding place of
Aédes calopus, 286

Bromeliads, water in plant, breeding place of
Anopheles cruzii, etc., 220-221

(See Parker,

 

495

Bromeliads, water in plant, breeding place of
mosquitoes, 147, 148

Bubonic plague, carriage by fleas, 316

Bubonic plague, suggested carriage by mos-
quitoes, 316

Burpon, Magor, on mosquitoes and Ocimum
viride, 415-416

ee JoHN, on mosquitoes in Alaska,

Buscx, Aveust, on effectiveness of mosquito
larvicide used by Isthmian Canal Com-
mission, 386-387

BUTLER, CAPTAIN, on abundance of mosqui-
toes, 133-134

Butterfly chrysalis, host of mosquito, 109

Cacao-husks, water therein, breeding place
of mosquitoes, 149

Cactus paste as mosquito larvicide, 381

Cadavers bitten by yellow-fever mosquito, 272

“Cafifi” (probably Culicoides) as a pest in
regions of upper Orinoco and Magdalena
rivers, 15

CaN mosquitoes breeding therein, 147,

Camphor phenol as fumigant against mos-
quitoes, 369-371

Camphor spirits, oil of citronella, and oil of
cedar as protection against mosquito
bites, 365

Canaries, transmission thereto of Plasmo-
dium precoz, 261

Cancer, suggested carriage by mosquitoes, 316

Cannibalistic habits in mosquito larve, 152

Caprimulgide as mosquito destroyers, 177-178

Carbolic acid as mosquito larvicide, 380

Carbolic acid, resin and caustic soda emul-
sion as mosquito larvicide, 385-387

Carica papaya. (See Pawpaw.)

Carp, reported practical use as enemy of mos-
quitoes, 402

CARROLL and REED. (See Reed and Carroll.)

CARROLL, death, due to effect of yellow fever
contracted previously, 255

CARROLL on Myzxococcidium stegomyie and its
supposed relation to yellow fever, 256

CARROLL on the organism producing yellow
fever, 257-258

Carrollia, abdomen, shape in female, 68

Carrollia, male genitalia, 71

Carrollia, species breeding in water
broken ends of bamboo, 149

Carter, Dr. H. R., on distance of flight of salt-
marsh mosquitoes, 341

CarTER on distance of flight of yellow-fever
mosquito, 273

Carter on effect of temperature on yellow-
fever mosquito, 272

Cassia oil as protection against mosquito
bites, 366

Castor oil, alcohol and oil of lavender as pro-
tection against mosquito bites, 365

Castor oil plant, alleged deterrent to mos-
quitoes, 414-415

Catch basins of sewers as breeding places for
mosquitoes, 390-391

Cattle, hosts of Anopheles, 208

in
496

Caustic soda, resin and carbolic-acid emul-
sion as mosquito larvicide, 385-387

Ceanothus americanus, flowers visited by un-
determined culicid, 111

Cedar oil, spirits of camphor and oil of citron-
ella as protection against mosquito bites,
365

CELLI, advocacy of extensive use of quinine
for malaria, 200

CreLtI, map showing comparative mortality
from malaria in Italy, 1900 and 1908, 201

CELLI on work of Italian Society for the
Study of Malaria, summary, 442

Cellia pharoensis—= Anopheles pharoensis,

Cells of mosquito wing, 60-61

Ceratopogon, capture in trap for adult mos--
quitoes, 378

Cerci of female mosquito, 67, 68

Cerci, vestiture, in certain mosquitoes, 74

Cervical sclerites of mosquito, 55, 57

Cervicum of mosquito, 57

Chetura pelagica, enemy of mosquitoes, 178

Chagasia fajardoi, eggs, 143

CHAMBERS, W. W., and F. E. Lurz.
Lutz, F. E., and W. W. Chambers.)

Chaoborus, development of eye in larva, 88

Chaoborus, mouth-parts of larva, modifica-
tion to predaceous habit, 95

Chaoborus, palpi, 52

Chaoborus, predaceous habits of larve, 169

Chaoborus, wing vestiture, 72

Chaoborus punctipennis larva, enemy of Cu-
lex pipiens larva, 169

“ Chapetonada” disease, 296

Charcoal, nitre and sulphur, burning to fumi-
gate against mosquitoes, 372-373

CHarmoy, D’EMeErReEz bE, on natural enemies
of malarial mosquitoes in Mauritius, 170

Cherry, wild, blossoms visited by Aédes sol-
licitans, 111

Chigoe (Sarcopsylla penetrans), reference to
account by Humboldt, 14

Cuitp, description of antennal sense organ
in Corethra culiciformis and Culex pi-
piens, 29-34

CHILD, observations on sensitiveness of danc-
ing male mosquitoes to sound vibrations,
36

Chimney-swallow, Chetura pelagica, enemy
of mosquitoes, 178

Chinaberry trees, alleged deterrents to mos-
quitoes, 416

Chinch bugs, habits of those dying from at-
tack of Sporotrichum, 157

Chironomide of genus Culicoides the “ j¢éjen”
of Spanish-American countries, 10

Chironomid, infection by Entomophthora,
158

Chironomid larve living in water in brome-
liaceous plants, 221

Chironomid, mention of early account of life
history, 21

Chironomus larve, prey of Tanypus larve,
169-170

Chironomus, prey of Culex nigritulus, 109

Chitinized prolongations of wing veins of
mosquito, 61

(See

 

INDEX

Chloral vapors as fumigant against mosqui-
toes, 375

Chlorine gas as a fumigant against mosqui-
toes, 375

Chloro-naphthaleum as mosquito larvicide,
380

Chordeiles virginianus, enemy of mosquitoes,
177

Chordeiles virginianus minor, enemy of mos-
quitoes, 177-178

CHRISTOPHERS on diverticula of mosquito,
78

CHRISTOPHERS on flight of Anopheles, 213-214

CHRISTOPHERS and STEPHENS. (See Stephens
and Christophers.)

Chrysanthemum  cinerariefolium,
tion, 367-368

Chrysanthemum marshallii, source of pyre-
thrum powder, 368

Chrysanthemum powder.
powder.)

Chrysanthemum roseum, cultivation, 367-368

Cicada, host of mosquitoes, 108

Cinchonization against malaria, 199-200

Circular to householders regarding mosqui-
toes, 422-423

Citronella oil and lanoline as protection
against mosquito bites, 366

Citronella oil and vaseline as protection
against mosquito bites, 366

Citronella oil, oil of pennyroyal, black tar and
mutton tallow as protection against mos-
quitoes and black flies, 366

Citronella oil, spirits of camphor and oil of
cedar as protection against mosquito
bites, 365

Civilization and its concomitants as causing
increase in malaria, 239-241

Civilization as effecting decrease in malaria,
236-239

Cladophora, food of Anopheles quadrima-
culatus larve, 150

Clasp-filaments of male genitalia of mosquito,

cultiva-

(See Pyrethrum

Claw or claws of mosquito, 64-66

Claws, tarsal, of female mosquito, structure
as correlated with copulatory position,
121, 128

Clear or colloid-like type of salivary-gland
acinus in mosquito, 82

Cuirron, Capt. A. T., on mosquitoes of Alaska,
138-139

Climate (see also Temperature).

Climate and the distribution of the yellow-
fever mosquito 292-294

Clypeus of mosquito adult female, 42

Clypeus of mosquito adult, structure, 36-37

Clypeus of mosquito larva, 84

Clypeus of mosquito pupa, 102

ee scale vestiture in some mosquitoes,

Cocoanut husks, water therein, breeding place
of mosquitoes, 149

Celodiazesis, food of larve, 151

Calodiazesis barberi (see also Anopheles bar-
veri).

eat barberi, claw and empodium,
INDEX

Celodiazesis barberi, food of larve, 151, 230

Celodiazesis barberi, habits of larve, 230

Ceélodiazesis barberi, enemy of Aédes triseria-
tus and Bancroftia signifer, 151

Celodiazesis barberi larve, prey of Megar-
hinus septentrionalis, 151

Celodiazesis barberi, larval habitats, 219

Celodiazesis barberi, predaceous habit of
larva, 96

Celodiazesis barberi, probable hibernation as
larva, 154

Collecting adult mosquitoes, 180

Collecting, mounting and rearing mosqui-
toes, 180-185

Colloid-like type of salivary-gland acinus in
mosquito, 82

Colon of mosquito, 75, 76

Colors, behavior of Anopheles with relation

thereto, 216-218

Community work, early, against mosquitoes,
356-359

Conveyances of various kinds as carriers of
mosquitoes, 345-352

Copper sulphate. (See Sulphate of copper.)

Copulatory attitude of mosquitoes, 121

Cordilura hemorrhoidalis, enemy of mos-
quitoes, 171

Cordulia as enemies of mosquitoes, 166

Corethra, enemies of Aédes, 169

Corethra, mouth-parts of larva, modification
to predaceous habit, 95

Corethra culiciformis, antennal sense-organ,
29-32

Corethrella, mouth-parts of larva, modifica-
tion to predaceous habit, 95

Corethrine, predaceous habits of larve, 169

Corethrineg, prey of Scatophaga stercorarius,

1

Corethrine, wing vestiture, 72

Corixa, enemy of mosquitoes, 165

Cornea of main eye of mosquito, 88

Corn oil as mosquito larvicide, 383

Corn, unripe ears, food of Anopheles, 209

Corpses bitten by Aédes calopus and Ano-
pheles, 114

Corrosive sublimate, effect on larve of yellow-
fever mosquito, 290

Costal cell of wing of mosquito, 60, 61

Costal vein of wing of mosquito, 60, 61

Courts of law and mosquitoes, 352-354

“ Cousin,” French name for mosquito, 10

Cowan, quotation from Ammianus Marcel-
linus on lions versus mosquitoes in Meso-
potamia, 8

Coxee of mesothorax of mosquito, 58

Coxe of metathorax of mosquito, 59

Coxe of prothorax of mosquito, 57

Coxe, vestiture, in mosquito, 74

Crab-hole mosquito larve, 149

Crab-hole mosquitoes not annoying to man, 1

Crabro quadrimaculatus, enemy of Culex, 171

Craig on dengue, pappataci fever and yellow

. fever, 306-307

Craia on geographical distribution of ma-
laria, 234-235

Crayfish, enemies of mosquito larve, 176

Creicuron on loss from malaria, 322

 

497

Cremastogaster difformis, disgorged food
eaten by mosquito, Harpagomyia splen-
dens, 49, 109-110

Crescentic bodies of Plasmodium falciparum,
192

Cresol preparations as mosquito larvicides,

Crithidia fasciculata, parasite of Anopheles
maculipennis and Culex, 161

“Crop” of insects, 77-78

“Crop ” of mosquito, 76

Cross-veins of mosquito wing, 60-61

Crow, sexual phases in parasite Hiemopro-
teus, 159

Crustaceans, food of fishes, 406

Crustacea, small, living in water in bromeli-
aceous plants, 221

Crustacea, aquatic, food of Culex pipiens and
C. nigritulus larve, 150

Cruz, Dr. OSwALpo, on campaign against yel-
low fever in Rio de Janeiro, 433-434

Cruz, Dr. OswaLpo, on sulphur dioxide fumi-
gation against mosquitoes, 373

Culex breeding in crab-holes not blood-
suckers, 110

Culex, breeding places, 218-219, 223

Culez, claws, 64

Culex eggs and oviposition, 140

Culex eggs not readily obtained in captivity,
185

Culex fed on syrup by Réaumur, 113

Culex, hibernation and estivation, 119

Culez, hiding places, 118

Culex, host of Crithidia fasciculata, 161

Culex, humpbacked appearance, 205

Culex larva, modifications of structure, 93

Culex larve as affected by larvicide of Isth-
mian Canal Commission, 385

Culex larve captured at surface of water by
agrionid larve, 167

Culex larve, effect on bacteria in water, 152

Culex larve, habits, 147

Culex larve, habits of those occurring in
bromeliads, 148

Culex larve in drinking water in small hotels
in South, 152

Culex larve, modes of feeding, 153

Culex larve, prey of Anopheles, 167

Culex larve, prey of Lutzia, 151

Culex larve, prey of Psorophora ciliata, 168

Culex larve, prey of Ranatra fusca, 165

Culex larve that feed anchored at bottom,
153

Culex larve that inhabit water in crab-holes,

Culex larve, where to find them, 184

Culex, lateral ciliation of abdomen of male,
69

Culex, location of egg-mass, 142

Culex, longevity, 119

Culex, male genitalia, 70, 71

Culex on ships, 351-352

Culex, palpi, 53, 54

Culex, position of sexes during copulation,
121, 128

Culex, prey of Crabro quadrimaculatus, 171

Culex, prey of Cuban nighthawk, Chordeiles
virginianus minor, 178
498

Culex pupa, description, 100-102

Culex, respiratory trumpets of pupa, 102

Culex, some species not easily determined
from adults alone, 181

Culex, species breeding in water in broken
ends of bamboo, 149

Culex, shaft of antenna, 26

Culex, time of activity, 118

Culex, tip of abdomen, cerci, 68

Culex, wing vestiture, 72

Culex abominator breeding in places inac-
cessible to fish, 412

Culex abominator, carriage in vehicles, 348

Culex abominator, host of mites, 173-174

Culex abominator larve abundant in Lemna-
covered water, 419

ee eee phytophagous habits,
1

Culex annulatus, comparison of mosquitoes
from Batavia therewith, 10

Culex te (See Uranotaenia argyro-
pus.

Culex bisulcatus, palpi, 54

Culex cantans, abundance, 132

Culex chloropterus, reference to original de-
scription, 13

Culex ciliaris of Bancroft = Culex quinque-
fasciatus, 315

Culex ciliatus, studies of mouth-parts, 37-44

Culex cubensis = Culex quinquefasciatus, 6

Culex cubensis, escape from 16-mesh wire
screen, 364

Culex cyanopterus as a pest, 15-16, 18

Culex cyanopterus (cyanopennis?), poison of
bite, 318

Culex cyanopennis, reference to original de-
scription, 13

Culex detritus (C. pipiens?), swarming, 124

Culex duttoni, breeding places, 223

Culex dyari, male genitalia, 71

Culex elegans, synonym of (Culex) Aédes
calopus, 301

Culex erythrothoraz, food habits, 107

Culex extricator, escape from 16-mesh wire
screen, 364

Culex extricator, food, 110

Culex fatigans (see also Culex quinque-
fasciatus).

Culex fatigans, breeding places, 223

Culex fatigans = Culex quinquefasciatus, 6,
106, 126, 315.

Culcez fatigans in Egypt, 428

Culex fatigans, macrosomia and microsomia,
361-362

Culex fatigans, universal association with
yellow-fever mosquito, 297

TEE PEDO reference to original description,

Culex halassios breeding in sea-water, 227-

Culex hirsutipalpis, breeding places, 223

Culex jenningsi egg-mass, 142-143

Culex jenningsi eggs, disposal, 144

Culex latisquama, antennal structure, 27-28

Culex latisquama, claws, 64

Culex latisquama, palpi, 54

Culex lineatus, Humboldt’s notes on distri-
bution, 13

 

INDEX

Culex lineatus, reference to original descrip-
tion, 13

Culex maculatus, reference to original de-
scription, 13

Culex melanurus, empodium, 67

ne aioe hibernation as larva, 120,
1

Culex melanurus, male genitalia, 71

Culex melanurus not a blood-sucker, 110

Culex microannulatus, partial development
of Filaria bancrofti therein, 315

Culex mosquito — Aédes calopus, 242

ee sey host of Agamomermis sp.,

Culex nemoralis male sucking human blood,

Culex nigritulus, food habits, 109

Culex nigritulus, food of larve, 150, 151

Culex penicillaris, reported transmitter of
filariasis, 315

Culez phytophagus, plant-feeding habits, 110

Culex pipiens, abnormal mouth-parts of a
male, 49

Culex pipiens, abnormal palpi of a female, 54

Culex pipiens, abolition of breeding places,
388-390

Culex pipiens, abundance, 132

Culex pipiens, antennal sense organ, 32-34

Culex pipiens, case of extraordinary abund-
ance, 135

Culex pipiens, claws, 64

Culex pipiens, Culex pungens a synonym, 6

Culex pipiens, early abundance in England, 8-
9

Culex pipiens, effect of bite, 319

Culex pipiens effecting fertilization of Lope-
zia coronata, 111

Culex pipiens, egg-laying process, 140-141

Culex pipiens, food habits, 106

Culex pipiens, food of larve, 150, 151, 184

Culer pipiens, host of Herpetomonas alger-
iense, 161

Culex pipiens
therein, 161

Culex pipiens, life history, studies by Réau-
mur, 22-23

oe pene mouth-parts of adult, studies,

7-

Culex pipiens, number of eggs in egg-mass,

142

larva, vorticellids found

Culex pipiens, prey of Chaoborus punctipen-
nis, 169

Culex pipiens, life-history observations by
Kleemann, 23-24

Culex pipiens of Lebredo=Culex quinque-
fasciatus, 315

Culex pipiens, palpi, number of joints, 51-52

Culex pipiens, phytophagous habits, 111

Culex pipiens, pitch of hum compared with
that of Anopheles quadrimaculatus, 211

Culex pipiens, pitch of hum compared with
that of Anopheles maculipennis, 212

Sule DEntEN respiratory system of larva, 89-

Culex pipiens, semidomestication, 205

Culex pipiens, songs and their production,
114-115

Culex pipiens, spermathece, 79
INDEX

Culex pipiens, structure, studies by Réau-
As mur, 22-23
ulex pipiens, swarming and mati i

121-123, 124, 125, 126 cee

Culex pipiens unaffected by pawpaw or cas-
tor-oil plants, 415

Culex pungens destroyed by fumigation with
Mimms Culicide, 370

Culex pungens, name formerly used to in-
clude Culex pipiens, Culex restuans and
Culex quinquefasciatus, 6

Culex quinquefasciatus, abolition of breed-
ing places, 388-390

Culex quinquefasciatus breeding in water in
steamers, 301

Culex quinquefasciatus, carriage by railroads
and vessels, 347, 348, 349

Culex quinquefasciatus, carrier of dengue
fever, 303-307

weer ee REE, carrier of filariasis,

Culex quinquefasciatus, Culex pungens a syn-
onym, 6

Culex quinquefasciatus destroyed in fumi-
gation with Mimms Culicide, 370

Culex quinquefasciatus, food difference of
sexes, 113

Culex quinquefasciatus, food habits of adult,
106-107

Culex quinquefasciatus, food of larve, 151

Culex quinquefasciatus found on vessels half
mile from shore, 273

Culex quinquefasciatus, host of Filaria phil-
ippensis, 316

Culex quinquefasciatus in Havana, 429

Culex quinquefasciatus in Hawaii, 344-345

Culex quinquefasciatus, mating habits, 126

Culex quinquefasciatus, noctural habits, 262

Culex quinquefasciatus, number of eggs in
egg-mass, 142

Culex quinquefasciatus, time of activity, 118

Culex quinquefasciatus, transmitter of ma-
laria in birds, 106, 196, 202

Culex rejector, escape from 16-mesh wire
screen, 364

Culex restuans, Culex pungens a synonym,
6

Culex restuans, food of larve, 184

Culex rufus, studies of mouth-parts, 37-44

Culex salinarius larve abundant in Lemna-
covered water, 419

Culex salinarius, prey of Megarhinus septen-
trionalis, 169

Culex sp., prey of Megarhinus septentrionalis,
169

Culex spp., swarming of males, 129

Culex teniorhynchus, carriage by ships, 349

Culex tarsalis, abnormal palpi of a female, 54

Culex tarsalis larve abundant among dense
alge, 418

Culex territans, egg-laying process, 141

Culex territans, host of mites, 173

Culex territans larva, attitude at surface
film, 153

Culex territans not a blood-sucker, 2, 110

Culex territans, number of eggs in egg-mass,
142

Culez tigripes, enemy of Anopheles, 170

 

499

Culicide, adaptation of mouth-parts to pre-
daceous habit, 95-97

Culicide, Mimms, as fumigant against mos-
quitoes, 369-371

ae larve, dead, food of Anopheles larve,

5

Culicid larve in water in bromeliaceous
plants, 221

Culicines, histology of salivary glands, 81, 82

Culicini, claws, 64-65

Culicini, color of pups, 103

Culicini, eyes of adult, 25

Culicini, fifth tarsal joint, 63-64

Culicini, membranous cushion of tarsi, 66

Culicini, mesonotum, 60

Culicini, mouth-parts of larva, adaptation to
predaceous habit, 96-97

Culicini, paddles of pupa, 103

Culicini, prothoracic lobes, 59:

Culicini, reduction in apical abdominal seg-
ments of male, 69

Culicini, portion of head bearing antenne, 36

Culicini, tibiae, 62

Culicoides, the “cafifi” mentioned by Hum-
boldt probably of this genus, 15

Culicoides, the “ jéjen” of Spanish-American
countries, 10

Culiseta, antennal structure, 28

Culiseta, claws, 65

Culiseta, egg-mass, 142

Culiseta eggs and oviposition, 140

Culiseta, habits of larve, 147

Culiseta, infuscation of wing-membrane, 62

Culiseta, longevity, 119

Culiseta, male genitalia, 70, 71

Culiseta, palpi, 53

Culiseta, tip of abdomen, cerci, 68

Culiseta, wing vestiture, 72

Culiseta annulatus, abnormal palpi of female,

Culiseta annulatus, appearance of larve and
pups in winter, 154

Culiseta annulatus, conflicting observations
on food habits, 108

Culiseta annulatus, effect of larve an bac-
teria in water, 152

Culiseta annulatus, hibernation, 120

Culiseta annulatus, hibernation of male, 119

Culiseta annulatus in peaty water and near
peat piles, 417

Culiseta annulatus, mention of Dufour’s
work on digestive and reproductive sys-
tems, 75

Culiseta annulatus, musical notes of male
and female, 116

Culiseta annulatus, plant-feeding habits, 110

Culiseta consobrinus —=Culiseta inornatus,
126

Culiseta inornatus, antennal structure, 28

Culiseta inornatus, copulatory attitude, 128

Culiseta inornatus, mating habits, 126

Cushion, membranous, of tarsi of mosquito,

Cybister desjardinsi, enemy of Anopheles
larve, 170

Cycle of Golgi, definition, 189

Cycle of Ross, definition, 189
500

Cyclops, food of Culex pipiens and C. nigri-
tulus larve, 150

Cyprin doré, fish enemy of Anopheles larve,
170

Cyprinodon, enemies of mosquitoes, 406, 407

Cyprinodon calaritanus, enemy of mosqui-
toes, 411-412

“ Daisy ” form of Plasmodium malariae, 191

DanieLs on use of “tuba root” (Derris el-
liptica) to destroy fish and mosquito
larvee, 387-388

Daphnia, food of Culex pipiens and C. nigri-
tulus larve, 150

Dagtine, Dz. SAMUEL T., on experiments with
larvicides by the Isthmian Canal Com-
mission, 384-385

Darxine, Dr. SAMUEL T., on size of screen for
pavtestion against various mosquitoes,

4

Darwin on insectivorous plants, 156

Datura stramonium. (See Jimson weed.)

“Day mosquito,” name often given yellow-
fever mosquito, 262

Deinocerites, antennal structure, 28-29

Deinocerites, cerci, gonapophyses,
lobes, 68

Deinocerites, claws, 65

Deinocerites larve, habits, 149

Deinocerites larve, where to find them, 184

Deinocerites, male genitalia, 71

Deinocerites, mouth-parts, 49

Deinocerites not blood-suckers but flower-
feeders, 109

Deinocerites, palpi, 54

Deinocerites, shaft of antenna, 27

Deinocerites, shape of abdomen and sternite
of eighth segment in female, 68

Deinocerites cancer, antennal structure, 28

Deinocerites cancer, claws, 65

Deinocerites cancer, eighth sternite and cerci,

sternal

Deinocerites cancer, mating habits, 126

Deinocerites cancer, palpi, 54

Deinocerites melanophylum, claws, 65

Deinocerites pseudes, cerci and gonapophyses,
68

Deinocerites pseudes, claws, 65

Deinocerites pseudes, sternite of eighth seg-
ment in female, 68

Deinocerites pseudes, palpi, 54

Deinocerites troglodytus, antennal structure,
28

Deinocerites troglodytus, claws, 65

Deinocerites troglodytus, palpi, 54

Dempwotrr, control work against malaria,
199

Dengue, 303-307

Dengue, organism probably an ultra-micro-
scopic protozoan, 306

Dermestid beetle larva mistaken for mosquito
Jarva, 22

Derris elliptica, use in destroying mosquito
larve and fish, 387-388

Derris uliginosa, decoctions and emulsions as
mosquito larvicides, 387

Desert mosquitoes, habits of larve, 146-147

 

INDEX

Dessication, resistance of eggs and larve of
Anopheles thereto, 231
Dessication, resistance of larve of yellow-
fever mosquito thereto, 291-292
Dr Vocet, Dr. W. T., on Anopheles breeding
in sea water, 224-225
Diaphanous, enemies of mosquitoes, 406
Diemyctylus tortosus, enemy of mosquito
larve, practical use, 176, 402
een studies of mouth-parts of mosquito,
7.
Dinanamesus, antennal structure, 29
Dineutes indus, enemy of Anopheles larve,
170
Dinitrocresol as a fumigant against mosqui-
toes, 375
Dinomimetes, antennal structure, 28-29
Dinomimetes, palpi, 54
Dinomimetes, postnotum, 60
Dinomimetes, shape of abdomen and ster-
nite of eighth segment in female, 68
Dinomimetes epitedeus, cerci and gonapophy-
ses, 68
Dinomimetes epitedeus, palpi, 54
Dinomimetes epitedeus, sternite of eighth
segment in female, 68
Dionea muscipula, insectivorous structure
and function, 156
Diplax berenice, enemy of mosquitoes, 166
Diplax (probably rubicundula), infection by
Entomophthora, 158
Diplaz spp., enemies of mosquitoes, 166
RE es pictus, enemy of mosquitoes,
7
Diplocystis, parasite of mosquitoes, 160
ee perhaps parasite of mosquitoes,
7
Disease, carriage by mosquitoes, 186-188
Disease, carriage by mosquitoes, early ideas,
186-188
Disease, endemic, as affecting the progress of
nations, 326-328
Dispersal of mosquitoes, influence of wind
thereon, 339-345
“Distomum ” forms parasitic in mosquitoes,
supposedly larval form of Lecithoden-
drium ascidia, 162
Distomum parasites of Anopheles, 162
Distomum globiporum, parasite of snail
(Limnea ovata) and fish, 162
Distomum globiporum supposed to be parasite
of Anopheles, 162
Diverticula of esophagus of mosquito, 75, 76,
77-79
Diverticula of esophagus of mosquito, func-
tion at ecdysis, 105
Diva larva described and figured by Brauer
in reality an Anopheles, 229
Dizxa, mouth-parts of larva, 95
Dog, host of Aédes calopus, 261
Dog, host of Filaria immitis, 316
Dolichopodid flies capturing mosquito larve,
170
aia ee in Anopheles mosquitoes, 205-
Dorsal vessel or heart of mosquito, 77
Dorsum of thorax of mosquito, 55
INDEX

Double benign tertian form of malaria, ex-
planation, 192-193

Double quartan fever, explanation, 193

Dy£ on yeasts found in mosquitoes, 158-159

Dytiscidz, enemies of mosquito larve, 164

Dytiscus marginalis, enemy of mosquito
larve and pupe, 164

wer ern as mosquito destroyer, 178-

Duckweed, rootless.
and Wolffia arhiza.)

Duckweeds as deterrents to mosquito larve,
418-421

Ducés, Dr. A., on mosquitoes and Eucalyptus
trees, 413

DuruHam, observations concerning mosquitoes
on shipboard, 274

DurHaM on breeding places of yellow-fever
mosquito, 284

eee on diurnal habits of Aédes calopus,

DurHam on domesticity of yellow-fever mos-
quito, 259

DurHAmM on oviposition of yellow-fever mos-
quito, 279

Dutron, ANNETT and ELLIOTT.
Dutton and Elliott.)

daa on Anopheles larve in sea-water, 227-

Dutton on association of Anopheles with
man, 222-224

Dutton on diurnal habits of yellow-fever
mosquito, 263

“Dutton’s membrane,” 313

Dragonflies, enemies of mosquitoes, 165-167,
170

Dragon-fly larve resistant to Isthmian Canal
Commission larvicide, 387

Drainage as a corrective of malaria, 238-239

Drainage measures against mosquitoes, Cali-
fornia, 394-396

Drainage measures against mosquitoes, Law-
rence, L. I., 392-394

Drainage measures against mosquitoes, Little
Neck Bay, Long Island, 396-397

Drainage measures against mosquitoes, New
Jersey, 397-402

Drainage measures against mosquitoes, New
Jersey, cost, 401-402

Drainage measures against mosquitoes, Strat-
ford, Conn., 392

Drainage measures against non-domestic mos-
quitoes, 391-402

Drainage, National Association, 449

Drainage work, value, 331-339

(See Lemna arrhiza

(See Annett,

Ecdysis of imago of mosquito, 103-105

Economic loss from mosquitoes, 320-339

Educational work regarding mosquito con-
trol, 421-424, 426-428

Egg burster of first-stage mosquito larva, 97

Egg follicles in ovaries of mosquito, 79

Egg follicles in ovaries of mosquito, histology,
83

Eggs and oviposition of mosquitoes, 140-145

Eggs of mosquitoes, how to obtain them, 185

 

501

Eighth segment of abdomen of mosquito
larva, 88-89

Electrocution of mosquitoes, 116-117

Elephantiasis arabum, 309

ELLiorr, Dutton and ANNETT.
Dutton and Elliott.)

Emesa longipes, enemy of Anopheles quadri-
maculatus and other mosquitoes, 172

Empidide#, predaceous habits, 170-171

Empodium of mosquito, 67

Empusa culicis, enemy of mosquitoes, 157

Empusa grylli, effect on grasshoppers, 157

Endemic disease as affecting the progress of
nations, 326-328

Endogenous cycle of malarial organism, defi-
nition, 189

Enemies, natural, of mosquitoes, 156-179

Enemies, natural, of mosquitoes, their practi-
cal use, 402-412

Enneacanthus gloriosus, enemy of mosqui-
toes, 406-407

Enneacanthus obesus, enemy of mosquitoes,
406-407

Entomophthora, destruction of mosquitoes
thereby, 157-158

Entomophthora spherosperma, enemy of mos-
quitoes, 157

Ephemera larve, food of fishes, 406

Ephemerid larve, enemies of mosquito larve,
167

Epicranium of pupa of mosquito, 100

Epimerum of mesothorax of mosquito, 58

Epimerum of metathorax of mosquito, 59

Epimerum of prothorax of mosquito, 57

Epipharynx of female mosquito, 38-39

Epipharynx of male mosquito, 43

Epipharynx of mosquito larva, 85, 86

Epipharynx of mosquito pupa, 100

Episternum of mesothorax of mosquito, 58

Episternum of metathorax of mosquito, 59

Bpisternum of prothorax of mosquito, 55-57

Epistom. (See Clypeus.)

Epitheca, enemies of mosquitoes, 166

Eptesicus fuscus, enemy of mosquitoes, 179

Ereunetes pusillus, enemy of mosquitoes, 179

Eristalis, structure of hypopharynx, 40

Hrythemis simplicicollis, enemy of Anopheles
quadrimaculatus, 167

Erytrosin, use in sensitizing mosquito larve
to light, 387

Eucalyptus, alleged deterrent to mosquitoes,
413-414

Eucorethra, mouth-parts of larva, modifica-
tion for predaceous habit, 95

Eucorethra underwoodi, predaceous habits of
larve, 169

Exogenous cycle of malarial organism, defi-
nition, 189

Eye, accessory, of mosquito, 83

Eyes of mosquito adult, structure, 25-26

Eyes of mosquito larva, 87-88

Eyes of mosquito pupa, 100

Eyes, vestigial, of mosquitoes, 25-26

Eylais, enemies of mosquitoes, 172-173

Eylais perhaps parasite of mosquitoes, 174

Eyseii on ecdysis of imago of mosquito, 103-
105

(See Annett,
502

Fecal matter, food of mosquito larva, 151

“Fan-shaped plate, anterior,’ of mosquito
larva, 92

Fat-body of mosquito, 79-80

Fat-body of mosquito, histology, 83

Feeding adult mosquitoes in captivity, 185

Feeding mechanism in mosquitoes, 76, 78-79

Feeding modes of mosquito larve, 152-153

Fext, Dr. E. P., on drainage of salt marshes
at Lawrence, L. I., benefits, 392-394

Female gametes or macrogametes, 190

Femora of mosquito, 62

Fermi and Tosini, experiment in malaria con-
trol in Asinara, 198-199

Fevers and mosquitoes, discussion of their
possible relation by Humboldt, 14-15, 16-
17

FIcALBI on supposed blood-sucking habit of
male yellow-fever mosquito, 109, 259-260

Fifth vein of mosquito wing, 61

Filaria, parasites of man, 308

Filaria bancrofti, mosquitoes that transmit
it, 315-316

Filaria bancrofti, parasitic worm producing
filariasis, transmission by mosquitoes,
808, 309

Filaria bancrofti, partial development
Anopheles maculipennis, 316

Filaria bancrofti, periodicity, 309-310

Filaria demarquayi, parasite of man, trans-
mission by mosquitoes, 309, 310

Filaria demarquayi, partial development in
Aédes calopus and Anopheles maculipen-
nis, 316

Filaria diurna believed by Manson to be em-
bryo form of Filaria loa, 310

Filaria diurna, periodicity, 310

Filaria immitis, evolution in mosquito, 312

Filaria immitis, parasite of dog, transmis-
sion by mosquito, 309, 310, 312, 316

Filaria loa, F. diurna perhaps a synonym, 310

Filaria nocturna = Filaria bancrofti, 308

Filaria perstans, parasite of man, transmis-
sion by mosquitoes, 309, 310

Filaria perstans, partial development in Ano-
pheles maculipennis, 316

Filaria philippensis, development in Culex
quinquefasciatus, 316

Filaria philippensis, parasite of man, trans-
mission by mosquitoes, 309, 310

Filaria sanguinis-hominis = Filaria
crofti, 308

Filarie, periodicity, 309-310

Filarial worms, evolution in mosquito, 310-
312

Filarial worms, life history, pathologic con-
ditions produced, 309

Filariasis, 307-316

Filariasis, distribution of disease, 308

Filariasis, mode of transmission to verte-
brate host, 312-315

Filariasis, mosquitoes that transmit it, 315-

16

in

ban-

Filariasis, transmission by mosquitoes, 308-
309

Filth in out-houses, food of Anopheles, 209
Fintay, Dr. Cantos, on discrimination of
Aédes calopus between races and indi-
viduals of man, 261

 

INDEX

Fintay, Dr. Cantos, on original endemic foci
of yellow fever, 294

Fintay, Dr. Cartos, work on Aédes calopus
and yellow fever, 242

Fin.tay, Dr, Carros, on oviposition of yellow-
fever mosquito, 279

Finuay, Dr. CaRtos, on relation of food to ovi-
position in Aédes calopus, 277

“Tins ” of pupa of mosquito, 99, 102

Fire alarm caused by swarms of mesquitoes,
124

First marginal cell of mosquito wing, 61

First posterior cell of mosquito wing, 61

First tarsal joint of mosquito incorrectly
termed “ metatarsus,” 63

First vein of mosquito wing, 60, 61

Fish and mosquitoes, Mr, Thibault’s observa-
tions on normal relation, 412

Fish, enemies of mosquitoes, 156

Fish, host of Distomum globiporum, 162

Fish in Brazil that destroys mosquitoes, 411

Fish in German Hast Africa that destroys
mosquitoes, 411-412

Fish in West Indies that destroy mosquitoes,
410-411

Fish, introduction into Hawaii to destroy
mosquitoes, 408-410

Fish, introduction into New Jersey to destroy
mosquitoes, 407

Fish, introduction into Panama Canal Zone to
destroy mosquitoes, 410-411

Fish killed by decoctions and emulsions of
Derris uliginosa, 387

Fish killed by Derris elliptica, 387-388

Fish, practical use as enemies of mosquitoes,
402-412

Fish, prey of Simulium (erroneously called
mosquitoes), 108

Fish, protozoan parasites, 159

Fish resistant to Isthmian Canal Commis-
sion larvicide, 387

Flabelle of mosquito larva, 85-86

Flagellate Protozoa that parasitize mosqui-
toes, 159, 161

Flaps of respiratory tube of mosquito larva
and their mechanism, 88, 90

Fleas, agents in transmission of bubonic
plague, 316

Flebotomus, carrier of pappataci fever, 306

Flexor plates of membranous cushion of mos-
quito tarsi, 66

Flies, black, protective mixture for fisher-
men and hunters, 366

Flies that capture mosquito larve, 170

“ Flight bladders ” of mosquito, 78

Flight of Anopheles, 212-216

Flowers, visitation by mosquitoes, 110-113

“ Flugblasen ” of mosquito, 78

Flushing of catch basins to prevent breeding
of mosquitoes, 391

Flycatchers, enemies of mosquitoes, 178

Fly, house, as affected by fumigation with
Mimms culicide, 370

Follicular tubes of ovaries of mosquito, 79

Follicular tubes of ovaries of mosquito, his-
tology, 83

Fomites, dengue fever not conveyed thereby,
307
INDEX

Fomites, yellow fever not conveyed thereby,
248, 245

Food habits of adult mosquitoes, 106-114

Food of mosquito larve and suggestions for
rearing, 183-185

Food “ reservoir” of insects, 77-78

Foods, vegetable, used to prolong life of blood-
sucking mosquitoes in laboratory, 114

Fore-gut of mosquito, 75-76

Fore-gut of mosquito, histology, 80-81

Formaldehyde gas as a fumigant against
mosquitoes, 375-376

Fourth posterior cell of mosquito wing, 61

Fourth vein of mosquito wing, 61

Francis, Dr. SAMUEL W., on mosquitoes and
malaria, 188

Francis, GOLDBERGER and ROoSENAU.
Rosenau, Francis and Goldberger.)

FRANCIS, PASSED ASSISTANT SURGEON, on pyro-
fume as a fumigant against mosquitoes,
371-372

FrencH CoMMISSION (see also Pasteur Insti-
tute and Institute Pasteur).

Frencw COMMISSION, experiments on biting
habits of yellow-fever mosquito, 264-269

FrENcH ComMISSIoN on oviposition of yellow-
fever mosquito, 278

FrencH ComMission on relation of food to
oviposition in Aédes calopus, 277, 278

FRENCH COMMISSION, work on mosquito réle
in yellow fever, 246-252

Frogs, enemies of mosquitoes, 176-177

Frogs, hosts of mosquitoes, 108

Fruit, food of yellow-fever mosquito, 270

Fruit juices, food of Anopheles, 209

Fruit, ripe, food of mosquitoes, 108

Fuel oil. (See Kerosene and Petroleum.)

Fulcrum in Musca, 39

FULLEBORN on mode of entry of filarie into
body of vertebrate host, 315

Fumigants and smudges against mosquitoes,
867-376

Fundulus grandis, introduction into Hawaii
to destroy mosquitoes, 409-410

Fundulus notatus, practical use as enemy of
mosquitoes, 403

Fundulus sp., use against marsh mosquitoes
in New Jersey, 401

Fungoid growths, probable food of Aédes
larve, 151

Fungous enemies of mosquitoes, 157-159

Fungus on Anopheles costalis larve, 227

(See

Gambusia afinis, enemy of Anopheles, 405

Gambusia afinis, introduction into Hawaii to
destroy mosquitoes, 409-410

Gambusia affinis, practical use as enemy of
mosquitoes, 403, 407

Gametes, definition, 190

Gecko lizard, enemy of mosquitoes, 177

Genitalia of female mosquito, 67-69

Genitalia of male mosquito, 69-71

Genlisea ornata, enemy of mosquito larve,
156

Giemsa process for staining slide prepara-
tions of malarial parasite for diagnosis,
191

Gies on flower-frequenting habits of Culi-
cide, 111

 

503

Gites on stalked infusorian parasite of mos-
quito larve, 161

Gills, tracheal, of mosquito larva, 89

Girardinus caudimaculatus, enemy of mos-
quitoes, 411

Girardinus peciloides, enemy of mosquitoes,
410-411

Glands, salivary, of mosquito, 77

Glands, salivary, of mosquito, histology, 81-
82

Glycerine as remedy for mosquito bites, 376

Gnat larve, food of fishes, 406

Gnats. (See Mosquitoes.)

Goatsuckers, enemies of mosquitoes, 177

GODEHEU DE RIVILLE’s observations on copula-
tion of Aédes calopus, 276

GOELDI, arguments in favor of African origin
of yellow-fever mosquito, 296

GoELDI on biting habits of yellow-fever mos-
quito, 263-264, 267, 268

GoELvri on food difference of sexes in mos-
quitoes, 113

GorELp1 on food preferences of Culex quinque-
fasciatus and Aédes calopus, 106-107

GoELDI on mating of yellow-fever mosquito,
275-276

GoELDI on note of yellow-fever mosquito, 116

GoELpI on relation of food to oviposition in
Aédes calopus, 277-278

GorLpI on size of mesh for screens against
rainwater-barrel and yellow-fever mos-
quitoes, 361-362

GOLDBERGER, RosENAU and FRANCIS.
Rosenau, Francis and Goldberger.)

Goldfish, practical use as enemies of mosqui-
toes, 403-405, 406, 408

Gomphus, enemies of mosquitoes, 166

Gonapophyses of female mosquito, 67

Goreas, CoLONEL, on disiderata for the per-
fect larvicide for use in the tropics, 384

Gor@As, COLONEL, on Girardinus peciloides
as enemy of mosquitoes, 410-411

Goreas, CoLoNEL, on larvicide of Isthmian
Canal Commission, its preparation and
application, 385-386

Grabhamia willcocksi = Aédes willcocksi, 129

GRAENICHER on phytophagous habits of Aédes
sylvestris, 111-112

GraHAM, Harris, proof of mosquito réle in
transmission of dengue fever, 303-304

Granular type of salivary-gland acinus in
mosquito, 82

Grass and sedges in marshes, mosquito larve
that extract air from roots, 149

Grasses, green, food of Anopheles, 209

Grasshoppers, actions of those dying from at-
tack of Empusa grylli, 157

Grassi, discovery that malarial parasite is
restricted to Anopheles mosquitoes, 196

Grassi, large-scale practical demonstration
of mosquito réle in malaria, 197

Gray, Sv. GrorcE, on egg-laying process in an
African mosquito, 141-142

GREEN on eggs and oviposition of Megarhinus
immisericors, 143 ;

Gregarine, parasites of insects and mosqui-
toes, 159, 160

Grusrs, SURGEON, on mosquitoes on ships,
350-352

(See
504

GuIrTeRAS, Dr. JuAN, on size of mesh for pro-
tection against yellow-fever and other
mosquitoes, 363-364

Guireras, Dr. Juan, work in Cuba on mos-
quito réle in yellow fever, 245

GUITERAS, SuRGEON G. M., on Laredo yellow-
fever outbreak of 1908, 252-253

Gyrinide, enemies of mosquito larve, 164-
165

Habitats peculiar to different mosquito larve,
148-150

Hemagogus, prothoracic lobes, 59

Hematozoan comparable to Plasmodium
found in cases of dengue fever, 306

Hemogregarinide, certain species that are
parasites of mosquitoes, 159

Hemogregarinide, parasites of cold-blooded
and warm-blooded animals, 159

Hemoproteus danilewskyi, parasite of birds,
transmission by mosquitoes, 159-160

Hemoproteus noctue, blood-parasite of owls,
transmission by Culex pipiens, 159

Hemoproteus, parasite of crow, 159

Hemosporidia, 188

Hemosporidia, parasites of insects, mam-
mals and birds, 159

Hate, Rev, Epwarp EVERETT, on inoculatory
effect of mosquito poisoning, 319

Half-moon bodies of Plasmodium falciparum,
192

Hawipay on mating habits of Anopheles bifur-
catus and A. maculipennis, 128-129

HALL, CHARLES F., on arctic mosquitoes, 137

Halteres of mosquito, 59

Halteres of pupa of mosquito, 101

Halteridium of birds, studies of MacCallum,
196

Harpagomyia splendens, food habits, 49, 109-
110

Harpagomyia splendens, mouth-parts, 49

Harpagones of male genitalia of mosquito, 69-
71

Harpes of male genitalia of mosquito, 69-71

Head of mosquito adult, 25-54

Head of mosquito larva, 84-88, 91

Head of mosquito pupa, 100

Head vestiture of mosquito, 73

Hearing in mosquitoes, 33-36

Hearing power of mosquitoes and their songs,
114-117

Heart of mosquito, 77

Heat as remedy for mosquito bites, 377

HEFFERAN and JorpAan. (See Jordan and Hef-
feran.)

Heizmannia scintillans, structure of eyes, 25

Heliconia, flower-spathes, eggs of Wyeomyia
therein, 145

Heliconia, mosquitoes breeding therein, 147,

Hemiptera resistant to Isthmian Canal Com-
mission larvicide, 387

HensHaw, H. W., on abundance of mosqui-
toes, 134

Hensuaw, H. W., on oviposition of yellow-
fever mosquito, 279

 

INDEX

HensHaw, H. W., on volatilization of pyreth-
rum powder to drive away mosquitoes,
368-369

Heptaphlebomyinz, subfamily based on so-
called “ seventh vein,” 61

Herpetomonas algeriense, parasite of Aédes
calopus and Culex pipiens, 161

Herpetomonas culicis, parasite of mosquitoes,
161

HERRICK, Pror. GLENN W., on the relation of
malaria to agricultural and other in-
dustries of the South, 323-324

Heterandria formosa, enemy of Anopheles,
405, 407

Heteroditus, enemies of mosquitoes, 406

Hibernation and estivation of mosquitoes,
119-120

Hibernation of mosquito larve, 154

Hiding places of mosquitoes, 118

eae E. W., on abundance of mosquitoes,

Hind-gut of mosquito, 75, 76

Hind-gut of mosquito, histology, 81

Hinps, E. G., observations on mating of yel-
low-fever mosquito, 275

Hinps, W. E., on larval habits of Psorophora
ciliata, 167-169

Hirundinide as mosquito destroyers, 178

H pa erythrogastra, enemy of mosquitoes,

Histology of alimentary canal and append-
ages of mosquito, 80-83

Hogs, hosts of Anopheles, 208

Honey-feeding mosquito, 49

Honey, food of yellow-fever mosquito, 270

Pere flowers, probable food of Anopheles,

Hooke, Ropert, account of life-history and
biting of mosquito, 20-21

ee obliterata, enemy of mosquitoes,

“ Hornitos,” little rooms used by Orinoco
Indians as refuges from mosquitoes, 14

“ Horns, respiratory,” of mosquito pupa, 99

Horse sickness of South Africa, suggested
carriage by mosquitoes, 316

Howarp, L. O., on attraction of mosquitoes to
sounds, 116-117

Howarp, L. O., on campaign against mosqui-
toes in New Jersey, 397

Howanrp, L. O., on economic loss from malaria,
320-324

Howarp, L. O., on endemic disease as affect-
ing the progress of nations, 326-328

mone L. O., on loss from yellow-fever, 325-

Howarp, L. O., on mosquito-control work
against malaria in Italy, 440-442

Howarp, L. O., on record of male Culex ne-
moralis sucking human blood, 109

Howarp, L. O., on the value of reclaimed
lands, 331-339

Household mosquitoes, abolition of breeding
places, 388-390

HUMBOLDT, observations on mosquitoes of the
eo Orinoco and Magdalena rivers, 10-

Humeral cross-vein of mosquito wing, 61
INDEX

Horst on air-cavity in cephalothorax of mos-
quito pupa, 99-100

Hurst on pupa of Culex, 100-102

Hurst on transformation of mosquito larva
to pupa, 98

Hydaticus exclamationis, enemy of Anopheles
larve, 170

Hydrachnide, enemies of mosquitoes, 172-173

Hydra fusca, enemy of mosquito larva, 161

Hydra viridis, enemy of mosquito larve, 161

Hydrangea arborescens, flowers frequented by
Megarhinus septentrionalis, 113

Hydras, fresh-water, enemies of mosquito
larve, 161-162

ae a perhaps parasite of mosquitoes,

Hydrometira, enemy of mosquitoes, 165

cube eae enemies of mosquito larva,

Hydrophilus obtusatus, enemy of mosquito
larve, 164

ae organ of anopheline mosquitoes,

4

Hydryphantes perhaps parasite of mosqui-
toes, 174

Hypocranium of mosquito larva, 86-87, 91

Hypopharynx of female mosquito, 39-40

Hypopharynx of male mosquito, 43

Hypopharynx of mosquito larva, 87

Hypopharynx of mosquito pupa, 100

Tleum of mosquito, 75, 76

Immunitas non sterilans, cases in malarial
countries, 194

Immunity, apparent, of certain persons in-
fected with malaria, 197

Immunity to yellow fever, 269

Indigo as remedy for mosquito bites, 376-377

Inflammatory fever, relation to yellow fever,

249-250

Infusorian, stalked, parasite of mosquito
larve, 161

Ingorgement of air by mosquito at ecdysis,
104-105

Inoculating effect of mosquito poisoning, 319

Insect enemies of mosquitoes, 164-172

Insects, dead, food of mosquito larve, 151

Insects, protozoan parasites, 159

InsTITUTE PasTEUR (see also Pasteur Insti-
tute and French Commission).

INSTITUTE PasTeuR at Rio de Janeiro on
spider, Salticus, as enemy of mosquitoes
and flies, 175

Integumental spots on Anopheles and Aédes
fulvus, 73

Iodine and saponated petroleum as remedy
for mosquito bites, 377

Iodine as remedy for mosquito bites, 377

Iridoprocne bicolor, enemy of mosquitoes,
178

Irregular fever, name for disease caused by
Plasmodium falciparum, 191
Irrigation and malaria, 239-241

JacoBson, Epwarp, on food habits of mos-
quito, Harpagomyia spiendens, 109-110

JAEGER, account of mosquitoes and Simuliide
in southern Russia, 18-19

 

505

James and Liston on breeding places of In-
dian Anopheles, 219-220

JamMrEs and Liston on comparative domes-
ticity between species of Anopheles, 206

James and Liston on flight of Anopheles, 213

JAMES and Liston on resistance of eggs and
larve of Anopheles to dessication, 231

JAMES, CAPTAIN, on food habits of Culex quin-
quefasciatus, 106

Janthinosoma larve, habits, 147

Janthinosoma larve, prey of Psorophora, 151

Janthinosoma, male genitalia, 70

Janthinosoma lutzii, carriage by ships, 349

“Jéjen” (Chironomide of genus Culicoides)
as a pest in regions of upper Orinoco and
Magdalena rivers, 10-18

JENNINGS, ALLAN H., on mosquito-eating habit
of Cuban nighthawk, 177-178

Jimson weed and nitre, burned powdered, as
a fumigant against mosquitoes, 375

Joblotia, antennal structure, 29

Joblotia, claws, 66

Joblotia, fifth tarsal joint, 63-64

Joblotia, food of larve, 151

Joblotia, head vestiture, 73

Joblotia larva, modifications of structure, 94

Joblotia, male genitalia, 70

Joblotia, mouth-parts of larva, adaptation to
predaceous habit, 96

Joblotia, prothoracic lobes, 59

Joblotia, vestiture of clypeus, 37

Joblotia digitatus, claws, 66

Joblotia digitatus eggs and their disposal,
148, 145

Joblotia digitatus larve in water of cocoanut
and cacao husks, 149

Joblotia digitatus larve, prey of Megarhinus,
151

Joblotia digitatus, palpi, 54

Joblotia trichorryes, claws, 66

Jounson, Dr. H. P., on value of duckweeds as
deterrents to mosquito larvae, 418-419

JOHNSTON on antennal sense organ in mos-
quitoes and its function, 33-34

Johnston’s organ, 29-34, 36

JoRDAN and HEFFERAN on breeding places of
Anopheles quadrimaculatus and A. punc-
tipennis, 221-222

JorpaNn and HEFreRAN on color preferences of
Anopheles punctipennis, 218

JorDAN and HEFFrERAN on malarial decrease in
Michigan following settlement, 237-238

KELLoce on development of mouth-parts in
Diptera (Simulium, etc.), 46-49

Kerosene against mosquito larve, early rec-
ommendations, 354-355

Kerosene against mosquito larve in sewer
traps and catch basins, 390-391

Kerosene as protection against mosquito
bites, 366-367

Kerosene, frequency of application to water
necessary to prevent breeding of mosqui-
toes, 382

Kerosene, methods of application as mosquito
larvicide, 382-383

Kerosene, use in catching adult mosquitoes,
378
506

“ Killarve ” as mosquito larvicide, 380

Killdeer. (See Oxyechus vociferus.)

Killifishes (see also Fundulus).

Killifishes, enemies of mosquitoes, 406

Kine, A. F. A., theory as to transmission of
malaria by mosquitoes, arguments there-
for, 194-195

Kingbird, Tyrannus tyrannus, enemy of mos-
quitoes, 178

Kinosuita on Anopheles and malaria in For-
mosa and Japan, 203-204

Krrpy and Spence, accounts of mosquito
abundance, 9-10

Kissincer, JouHn R., a volunteer for experi-
ment in transmission of yellow fever by
bite of infected mosquito, 244

KLEEMANN, observations on life-history of
mosquitoes (Culex pipiens and Aédes),
23-24

Kwyas on Godeheu de Riville’s observations on
copulation of Aédes calopus, 276

Kwas on mating-habits of mosquitoes, 121-126,
126-128, 130-131

KNAB on mosquitoes as flower-visitors, 110-
113

Kocu, Rosert, investigations of malaria, 196-
197

Kocu, malaria-control work in German New
Guinea, 199

Labelle of female mosquito, 41

Labelle of male mosquito, 43

“Labial plate” of mosquito larva, 87

Labium of female mosquito, 41-42

Labium of male mosquito, 43-44

Labium of mosquito larva, 87

Labium of mosquito pupa, 100, 101

Labrum and appendages of mosquito larva,
84, 85-86

Labrum of female mosquito, 37-39

Labrum of male mosquito, 43

Labrum of mosquito pupa, 100

Lamella, lower, of labrum in mosquitoes, 44

LANpDoIS on musical notes of Culiseta annu-
latus, 116

LANDoIs on sound-production in mosquitoes,
114-115

Lands, reclaimed, value, 331-339

Lanoline and oil of citronella as protection
against mosquito bites, 366

Laredo outbreak of yellow fever in 1903, 252-
253

Larve of mosquitoes, food, 150-154

Larve of mosquitoes, habits, 146-150

Larve of mosquitoes, importance in specific
determination, 181

Larve of mosquitoes, when to find them, 184-
185

Larve of mosquitoes, where to find different
genera, 184

Larvicide for mosquitoes, disiderata for the
ideal substance, 384

Larvicide used against mosquitoes by Isth-
mian Canal Commission, 384-387

Larvicides against mosquitoes, 379-388

Larycith III as a fumigant against mosquli-
toes, 375

“ Lateral comb” of scales of Culex larva, 91

 

INDEX

Lateral lobe of mesonotal scutum of mosquito,

Lateral lobes of mesonotum of mosquito, 58

Lavender oil, castor oil, and alcohol as pro-
tection against mosquito bites, 365

Laveran, discoverer of malarial parasite in
human blood, 195

Laverania, generic name used for Plasmo-
dium falciparum by some authors, 192

Laverania malarie = Plasmodium  falci-
parum, 189

Law courts and mosquitoes, 352-354

Lazear, death from yellow fever during in-
vestigations of U. S. Army Commission,
255

LEsBREDO, Dr. Mario G., on mode of transmis-
sion of filaria from mosquitoes to human
beings, 313-314

Lesrepo, Dr. Mario G., synopsis of filarial de
velopment within mosquito, 311

Lecithodendrium ascidia, parasite of bat,
Pipistrella europai, 162

Legislation against mosquitoes in New Jer-
sey, 397-400

Legs of mosquito adult, 62-67

Legs of mosquito pupa, 101-102

Legs, scales, in mosquito, 74

Lemna arrhiza (see also Wolffia arhiza).

Lemna arrhiza and L. minor as deterrents
against mosquito larve, 418

Lemnacee, (See Duckweeds.)

Leon on salivary pump of Anopheles, 50

Lepiselaga, prey of Monedula signata, 171

Hepes suggested carriage by mosquitoes,

Lesticocampa, claws, 66

Lesticocampa, food of larve, 151-152

Lesticocampa, habits of larve inhabiting
bromeliads, 148

Lesticocampa, head vestiture, 73

Lesticocampa larve, enemies of mosquito
larve, 167

Lesticocampa larve, where to find them, 184

Lesticocampa, male genitalia, 70

Lesticocampa, mouth-parts of larva, adapta-
tion to predaceous habit, 96

Lesticocampa, palpi, 54

Lesticocampa, prothoracic lobes, 59

Lesticocampa, scales of legs, 74

Lesticocampa dicellaphora, claws, 66

Lesticocampa lampropus, 66

Lewis and Boyce. (See Boyce and Lewis.)

peas auripennis, enemy of mosquitoes,

Libellula luctuosa, enemy of mosquitoes, 166
Libellula pulchella, enemy of mosquitoes, 166
er res semifasciata enemy of mosquitoes,
ea larve, enemies of Anopheles larve,
1
Liceaaa, Dz. Epvarpo, on compaign against
yellow fever and mosquitoes in Vera
Cruz and Mexico generally, 435-436
Life-cycle of malarial organisms, 189-194
Lighters as means of conveying mosquitoes
from shore to vessels at anchor, 274-275
Light, sensitized mosquito Jlarve killed
thereby, 387
INDEX

Limatus, claws, 64

Limatus, food of larve, 151

Limatus, larve in water of cocoanut and
cacao husks, 149

Limatus durhamii, cannibalistic habits, 152

Limatus durhamii, claws, 66

pe ovata, host of Distomum globiporum,

Limnobates, enemy of mosquitoes, 165

Limnobia, palpi, 53

Lions versus mosquitoes in Mesopotamia, 8

Lispa sinensis, enemy of mosquito larve, 170

Lizard, gecko, enemy of mosquitoes, 177

Lizards, hosts of mosquitoes, 108

Lobes, subapical or subbasal, of side pieces of
male genitalia of mosquito, 69-71

Lobipes lobatus, enemy of mosquitoes, 179

Locomotion of mosquito larve, 152-154

Locusts, reported enemies of mosquitoes, 172

Longevity of mosquitoes, 118-119

Lopezia coronata, fertilization effected by
Culex pipiens, 111

Loss, economic, from mosquitoes, 320-339

Losses from mosquitoes aside from the carry-
ing of disease, 328-339

Low on mode of transmission of filarie to
vertebrate host, 313

Low and Sampon. (See Sambon and Low.)

Lucania, enemies of mosquitoes, 406, 407

Lucius americanus, enemy of mosquitoes, 408

LuccER on census of mosquito stages in rain-
water barrel, 134

LUNDBECK on mosquitoes in Greenland, 136-
137

Lutz, F. E., and W. W. Cuamsers on relative
value of different fishes as mosquito de-
stroyers 407-408

Lutzia, beneficial habits of larve, 152

Lutzia eggs and oviposition, 140

Lutzia, food of larve, 151

Lutzia, habits of larve, 147

Lutzia larve, enemies of mosquito larve, 167

Lutgia larve, where to find them, 184

Lutzia, longevity, 119

Lutzia, male genitalia, 71

Lutzia, mouth-parts of larva, adaptation to
predaceous habit, 97

Lutzia, position of egg-mass, 142

Lutzia bigotit egg-mass, position and colora-
tion, 142

Lutzia bigotii, empodium, 67

Lutzia bigotii larve, enemies of Aédes calo-

~ pus larve, practical utilization, 167

MacCatuum, studies of Halteridium in birds,
196

Macrogametes, definition, 190

Macrosomia in mosquitoes, 361-362

Mailing specimens of mosquitoes, 181

Malaria, 188-241

Malaria, a check on progress, 321-322

Malaria and agriculture, 323-324

Malaria and irrigation, 239-240

Malaria and mosquitoes in Algeria, 438-439

Malaria and mosquitoes in India, 443

Malaria and mosquitoes in Ismailia, Suez
Canal, 440

Malaria and mosquitoes in Italy, 440-442

34

 

507

Malaria and mosquitoes in Japan and For-
mosa, 436-438

Malaria and mosquitoes in Leipzig, Germany,
427-428

Malaria and mosquitoes in small town near
New York City, 446

Malaria and mosquitoes on Roman Cam-
pagna, Sambon’s and Low’s experiment,
197-198

rn and mosquitoes on Staten Island, 444-

Malaria and sea-water pools, 224-227
Malaria, appearance and disappearance, 236-
241

ae at Brookline, Mass., and its cause,

Malaria at high altitudes, 235-236

Malaria, decrease following settlement and
civilization, 236-239

Malaria, disappearance and appearance, 236-
241

Malaria, distribution, geographic, 232-236

Malaria, distribution, vertical, 235-236

Malaria, economic loss therefrom, 320-325

Malaria, geographical distribution, 232-236

ee geographical distribution in Africa,
5

ee geographical distribution in Asia,

Malaria, geographical distribution in North
America, 234

Malaria in birds, researches of Dr. Ronald
Ross, 195-196

Malaria in Africa, 325

Malaria in Delta region of Mississippi, 324 “~~

Malaria in Greece, 326-328

Malaria in India, 324-325

Malaria in Italy, comparison of 1900 and 1908,
201

Malaria in Italy, loss therefrom, 321-322

Malaria in United States, deaths therefrom,
320-821

Malaria in United States, history, 320

Malaria in United States, loss therefrom, 320-
324

Malaria, increase due to civilization and its
concomitants, 239-241

Malaria, mosquitoes that carry it, 202-204

Malaria on shipboard, 349-350

Malaria, scientific demonstration of trans-
mission, 194-202

Malaria, spontaneous recoveries, 194

Malaria, vertical distribution, 235-236

Malarial diseases of birds, transmission by
mosquitoes, 106

Malarial organisms, 188-194

Malarial organisms, how to diagnose the spe-
cies, 190-191

Malarial organisms, life-cycle, 189-194

Malarial organisms, some points still await-
ing elucidation, 193

Male gametes or microgametocytes, 190

Malignant tertian fever, name for disease
caused by Plasmodium falciparum, 191

Mallard, Anas platyrhynchos, enemy of mos-
quitoes, 179

Malpighian tubules of mosquito, 77

Malpighian tubules of mosquito, histology, 82
508

Malta fever acquired through consumption of
milk of affected goats, 316

Malta fever, suggested carriage by mosqui-
toes, 316

Mammals, protozoan parasites, 159

Mandibles of mosquito adult, 40

Mandibles of mosquito larva, 86, 91

Mandibles of mosquito pupa, 100, 101

Man, host of Plasmodium, 189

Man in relation to mosquitoes, 186-319

Mansonia egg-mass, 142

Mansonia eggs and oviposition, 140

Mansonia, habits of larve, 149

Mansonia, habits of pupe, 155

Mansonia larva, mode of feeding, 153

Mansonia larva, modifications of breathing
apparatus, 93

Mansonia larve, where to find them, 184

Mansonia, male genitalia, 70, 71

Mansonia, respiratory trumpets of pupa, 103

Mansonia, spermathece, 79

Mansonia, tip of abdomen, cerci, 68

Mansonia, wing vestiture, 73

Mansonia arribalzage, egg-mass, 142

Mansonia arribalzage, habits of larva, 149

Mansonia fasciolatus egg-mass, 142

Mansonia fasciolatus, habits of larva, 149

Mansonia fasciolatus, palpi of female, 54

Mansonia fasciolatus, wing vestiture, 73

Mansonia perturbans, claws, 65

Mansonia perturbans, effect of bite, 319

Mansonia perturbans egg-mass, 142

Mansonia perturbans, habits of larva, 149

Mansonia perturbans, host of mites, 173

Mansonia perturbans, time of activity, 118

Mansonia pseudotitillans (?=titillans),
transmitter of filariasis, 315

Mansonia titillans, eighth segment and ter-
gite of female, 68

Mansonia titillans, habits of larve, 149

Mansoniu titillans, wing vestiture, 73

Mansonioides, hosts of mites, 173

Mansoniodes uniformis, spermathece, 79

Mansonioides uniformis, transmitter of filari-
asis, 315

Manson on forms of filariasis, 308

MARCELLINUS, AMMIANUS, account of lions
versus mosquitoes in Mesopotamia, 8

MaxrcHoux and Simonp on original endemic
foci of yellow fever, 294-295

MarcHoux and Srmonp on yellow fever and
its transmission, 246-249

“Marguerite ” form of Plasmodium malarie,
191

Marshes, drainage in control of mosquitoes,
391-402

Martin, purple. (See Progne subis.)

Mating-habits of mosquitoes, 120-132

MatTuHEson, W. J., on possibilities of mosquito
extermination, 426

Maxille of female mosquito, 40-41

Maxille of male mosquito, 43

Maxille of mosquito larva, 86, 91

Maxille of mosquito pupa, 100, 101

Maxillary palpi of female mosquito, 41

Maxillary palpi of male mosquito, 43

Maxillary palpi of mosquito larva, 86, 91

Maxillary palpi of mosquito pupa, 100

 

INDEX

Maxim, Hiram §., on attraction of male mos-
quitoes to sounds, 117

MaxweEL.-Lerroy, H., on apparatus for catch-
ing adult mosquitoes, 377-378

Mayer, A. H., experiments regarding sup-
posed auditory function of antenne in
mosquitoes, 34-36

Mayer, Dr. ALFRED G., on migratory swarms
of mosquitoes invading Tortugas Islands,
341-342

McATEE, W. L., on Anopheles quadrimacula-
tus sitting, unentangled, on spider web,
176

McAtTEes, W. L., on shorebirds as mosquito de-
stroyers, 179

McCoox, Dr. H. C., on spiders as enemies of
mosquitoes, 175

Megarhinus, beneficial habits of larve, 152

Megarhinus, chitinized prolongations of wing
vein, 61

Megarhinus, claws, 65

Megarhinus eggs and their disposal, 143

Megarhinus, enemies of other mosquitoes, 402

Megarhinus, femora, 62

Megarhinus, food habits of adults, 109, 113

Megarhinus, food of larve, 151

Megarhinus, habits of larve, 151

Megarhinus, habits of larve inhabiting brom-
eliads, 148

Megarhinus, habits of larve of tropical spe-
cies, 151

Megarhinus, head vestiture, 73

Megarhinus larva, modifications of structure,
93, 94-95

Megarhinus larve,
larve, 167

Megarhinus larve, predaceous habits, 169

Megarhinus larve, where to find them, 184

Megarhinus, lateral ciliation of abdomen of
male, 69

Megarhinus, length of pupal period, 155

Megarhinus, male genitalia, 70

Megarhinus, mesonotum, 60

Megarhinus, mouth-parts of adult, 49

Megarhinus, mouth-parts of larva, adapta
tion to predaceous habit, 96, 97

Megarhinus, palpi, 53

Megarhinus, second vein, 61

Megarhinus, shaft of antenna, 27

Megarhinus, species breeding in water in
broken ends of bamboo, 149

Megarhinus, swarming of males, 131

Megarhinus, time of activity, 118

Megarhinus, vestiture, 74

Megarhinus hermorrhoidalis, eggs and their
disposal, 143

Megarhinus immisericors, eggs and their dis-
posal, 143

Magy rae moctezuma, swarming of males,

enemies of mosquito

Megarhinus septentrionalis, enemy of Celodi-
azesis berberi, 151

Megarhinus septentrionalis, food of larve, 151

Megarhinus septentrionalis frequenting flow-
ers of Hydrangea arborescens, 118

Megarhinus septentrionalis, predaceous
habits of larvee, 169

Megarhinus septentrionalis, host of mites, 173
INDEX

Megarhinus septentrionalis, hibernation as
larva 120, 154

Megarhinus septentrionalis,
males, 132

M eae aue septentrionalis, time of activity,

Swarming of

Megarhinus solstitialis, time of activity, 118

Megarhinus violaceus, prey of culicid larve,
a in water in bromeliaceous plants,

MEINERT on mouth-parts of Diptera, 45-46

MEINERT on palpi of Diptera, 52-53

Membrane of mosquito wing, 62

Menolepis, habits of larva, 149

a ee sclerite ” or plate of mosquito larva,

Mentha aquatica, flowers visited by Ano-
pheles, 111

Mentum of mosquito larva, 86-87

Mercuric chloride as a fumigant against
mosquitoes and flies, 374-375

cent parasite of Aédes calopus larva, 163-
16

Merozoits, definition, 190

MERRIAM, FLORENCE A., on insect food of eaves-
or cliff-swallow, 178

Mesoepisternum. (See Episternum of Meso-
thorax.)

Mesogonistius chetodon, enemy of mosqui-
toes, 407

Mesonotum of mosquito, 60

Mesonotum of mosquito, vestiture, 73-74

Mesopleurum of mosquito, 58

Mesosternum of mosquito, 59

Mesotergum of mosquito, 57-58

Mesothemis longipennis, enemy of mosqui-
toes, 166

Mesothorax of mosquito adult, 57-59

Mesothorax of mosquito pupa, 101

Metanotum, so-called, of mosquito.
Postnotum.)

Metatarsus, so-called, of mosquito, 63

Metatergal bridge of mosquito, 57

Metathorax of mosquito, 59

Methylene blue as remedy for malaria, 194

MI4LL on northern mosquitoes, 138

MIALL on poison of mosquito-bite, 317

Micrococcus melitensis, 306

Microfilarie, larval worms of Filaria, 308

Microfilaria nocturna = Filaria bancrofti, 308

Microgametes, definition, 190

Microgametocyte, definition, 190

Micro-organisms in fore-gut of mosquito, 81

Micropalama himantopus, enemy of mosqui-
toes, 179

Microscope-slide mounts for mosquitoes, 182-
183

Microsomia in mosquitoes, 361-362

“ Microthorax ” of mosquito, 57

Midge larve, food of fishes, 406

Mid-gut of mosquito, 75, 76

Mid-gut of mosquito, histology, 81

Migrations of mosquitoes, 339-344

“Millions.” (See Girardinus peciloides.)

Mimms culicide. (See Culicide, Mimms.)

Minnow, mud. (See Umora.) :

Minnows, top, practical use as enemies of
mosquitoes, 403, 408

(See

 

509

Missionaries, sufferings from mosquitoes in
South America, 10-13, 15, 16, 18

MitcHett, Hon. J. D., on two remarkable
mosquito migrations, 339-340

Mites, enemies of mosquitoes, 172-175

Mixed infections of Plasmodium, 193

Mochlonyz. (See Corethra.)

Molasses, food of yellow-fever mosquito, 270

Mollinesia latipennis, introduction into Ha-
waii to destroy mosquitoes, 409-410

Monedula signata, enemy of yellow-fever and
other mosquitoes and Lepiselaga, 171

Monkeys, hosts of Plasmodium, 189

Mosquito adult, ecdysis, 103-105

Mosquito adult, habits, 106-139

Mosquito adult, structure, 25-74

Mosquito bites, effect, 316-319

Mosquito bites, protection against them, 359-
376

Mosquito bites, relative susceptibility of dif-
ferent persons thereto, 318-319

Mosquito bites, remedies, 376-377

Mosquito-control campaigns, absurd argu-
ments against them, 424

Mosquito-control campaigns, convincing the
public of their desirability, 422-424

Mosquito-control campaigns in Germany, re-
cent work, 427-428

Mosquito-control campaigns, interesting the
young, importance, 426-427

Mosquito-control campaigns, interesting the
young in San Antonio, Tex., 426-427

Mosquito-control campaigns, interesting the
young in Worcester, Mass., 357-358

Mosquito-control campaigns, motto, 425

Mosquito-control campaigns, organization,
421-429

Mosquito-control campaigns,
methods, 425

Mosquito-control campaigns, summary of ob-
jects, 425

Mosquito-control, examples, 429-449

Mosquito-control work in Algeria, 438-489

Mosquito-control work in Egypt, along river
fronts, 428

Mosquito-control work in Havana during
American occupation, 1901-2, 429-430

Mosquito-control work in Ismailia, Suez Ca-
nal, 440

Mosquito-control work in Italy, 440-442

Mosquito-control work in Japan and Formosa,
436-438

Mosquito-control work in Panama Canal Zone,
430-432

Mosquito-control work in Rio de Janeiro, 432-
435

Mosquito-control work in small town near
New York City, 446

Mosquito-control work in United States, 444-
449

Mosquito-control work in Vera Cruz and Mex-
ico generally, 435-436

Mosquiro EXTERMINATION SocIETy, papers
read at conventions, 448-449

Mosquito, habits of adult, 106-139

Mosquito “ hawks,” 165

Mosquito larva, color diversity in different
forms, 94-95

summary of
510

Mosquito larva, modifications of structure,
91-97

Mosquito larva, structure, 84-98

Mosquito larve, destruction, 379-391

Mosquito larve that do not come to surface
of water, 149

Mosquito, larval stages, number, 97

Mosquito larvicide, disiderata for the ideal
substance, 384

Mosquito, name of places, 133

Mosquito pupa, 99-105

Mosquito, yellow fever.
mosquito, Stegomyia fasciata,
myia calopus and Aédes calopus.)

Mosquitoes, adults, apparatus for catching
them, 377-379

Mosquitoes, anatomy, gross, 75-80

Mosquitoes, anatomy, internal, 75-83

Mosquitoes and fevers, discussion of their
possible relation by Humboldt, 14-15, 16-
17

Mosquitoes and filariasis, 308-309

Mosquitoes and fish, Mr. Thibault’s observa-
tions on normal relation, 412

Mosquitoes and malaria in Algeria, 438-440

Mosquitoes and malaria in India, 443

Mosquitoes and malaria in Ismailia, Suez
Canal, 440

Mosquitoes and malaria in Italy, 440-442

Mosquitoes and malaria in Japan and For-
mosa, 436-438

Mosquitoes and malaria in small town near
New York City, 446

Mosquitoes and malaria on Roman Cam-
pagna, Sambon’s and Low’s experiment,
197-198

Mosquitoes and malaria on Staten Island, 444-
446

(See Yellow-fever
Stego-

Mosquitoes and prosecutions, 352-354

Mosquitoes, apparatus for catching adults,
377-379

Mosquitoes, arctic, abundance and ferocity,
135-139

Mosquitoes, arctic and northern, habits of
larve, 146

Mosquitoes as flower-visitors, 110-113

Mosquitoes, biology, early accounts, 20-24

Mosquitoes, breeding places of household spe-
cies, abolition, 388-390

Mosquitoes, carriage by ships, railroads, and
other conveyances, 345-352

Mosquitoes, deterrent trees and plants—so
alleged, 413-421

Mosquitoes, early accounts, 8-19

Mosquitoes, early accounts of biology and
structure, 20-24

Mosquitoes, early control work, 354-359

Mosquitoes, economic loss therefrom, 320-

9

Mosquitoes, food habits, necessity for exact
data, 185

Mosquitoes, histology, 80-83

Mosquitoes in courts of law, 352-354

Mosquitoes in marshes, control, 391-402

Mosquitoes, increase in number of discovered
species, 1-5

Mosquitoes, influence of wind on dispersal,
339-345

 

INDEX

Mosquitoes, legislation against them in New
Jersey, 397-400

Mosquitoes, losses therefrom aside from the
carrying of disease, 328-339

Mosquitoes, males with complete mouth;parts,
109

Mosquitoes, migrations, 15

Mosquitoes, natural enemies, their practical
use, 402-412

Mosquitoes, necessity for exact data regard-
ing food habits, 185

Mosquitoes, northern and arctic, abundance
and ferocity, 135-139

Mosquitoes, northern and arctic, habits of
larven, 146

Mosquitoes, organization for
work against them, 421-428

Mosquitoes, personnel, paid and voluntary, in
present investigation, 2-7

Mosquitoes, practical importance of knowl-
edge of habits, 1-2

Mosquitoes, predilection for certain animals,
106

Mosquitoes, prevention of breeding in sewers,
390-391

Mosquitoes, previous general publications
thereon, 1

Mosquitoes, protection from bites by liquids,
365-367

Mosquitoes, protection from bites by screen-
ing breeding places, 365

Mosquitoes, protection from bites by screens
and canopies, 359-364

Mosquitoes, protection from bites by smudges
and fumigants, 367-376

Mosquitoes, protective and remedial work,
354-449

Mosquitoes, record of male sucking human
blood, 109

Mosquitoes, relation to man, 186-319

Mosquitoes, remedies for bites, 376-377

Mosquitoes, résumé of investigations under
Carnegie Institution, 2-5

Mosquitoes, structure, early accounts, 20-24

Mosquitoes, suggested relations with various
diseases, 316

Mosquitoes, terms applied to them in Spanish-
American countries, 10

Mosquitoes that do not suck blood, 109-114

Mosquitoes that transmit filariasis, 315-316

Mosquitoes that transmit malaria, 202-232

Mosquitoes versus lions in Mesopotamia, 8

“ Mosquitos” (Simuliide) as a pest in the
regions of the upper Orinoco and Magda-
lena rivers, 10-18

Mothballs as remedy for bites of mosquitoes,
fleas, etc., 377

Moulting of mosquito larva, 97-98

Mounting mosquito adults, 180-181

Mounting mosquito larval skins, genitalia,
etc., on microscope slides, 182-183

“Moustique,” application of term, 108

“ Mouth brushes ” of mosquito larva, 91

Mouth of mosquito, 75

Mouth-parts of culicid larva, adaptation to
predaceous habit, 95-97

Mouth-parts of mosquito and other Diptera,
views of authors as to homology, 44-50

community
INDEX

Mouth-parts of mosquito larva, 84-87

Mouth-parts of mosquito pupa, 100-101

Mucus gland and duct of reproductive system
of mosquito, 79

Mucus gland of reproductive system of mos-
quito, histology, 83

Musca, fulcrum, definition, 39

Muscide, infection by Entomophthora, 158

Mutton tallow, black tar, oil of citronella and
oil of pennyroyal as protection against
mosquitoes and black flies, 366

Myiochanes virens, enemy of mosquitoes, 178

Mysxococcidium stegomyie and yellow fever,
256-257

Myxococcidium stegomyia, yeast parasite of
Aédes calopus, 159

Myxosporidia, protozoan parasites, 159

Naphthalene moth balls as remedy for bites
of mosquitoes, fleas, etc., 377

Nasturtium officinale, larve of Anopheles bi-
furcatus hibernating among leaves, 154

NATIONAL DRAINAGE ASSOCIATION, 449

Nations, progress as affected by endemic dis-
ease, 326-328

Natural enemies of mosquitoes, 156-179

Naucoris, enemies of mosquito larve, 165

Nemocera, biting, called “ tipulaires ”
Humboldt, 10

Nemocera, palpal joints, number, 51

Nematode parasites of mosquitoes, 162-164

Nepa, enemies of Anopheles larve, 170

Nepa, enemies of mosquito larve, 165

Nepenthes, liquid secreted by plant as habitat
of mosquito larve, 148

Netting for bars or canopies, size of mesh for
protection from mosquitoes, 362

Nettings against mosquitoes, 360, 362-363

Newt or salamander, Diemyctylus tortosus,
enemy of mosquito larve, 176

Nidularium, water in plant affording breed-
ing place for mosquitoes, etc., 221

Nighthawk, Cuban. (See Chordeiles vir-
ginianus minor.)

Nighthawks, enemies of mosquitoes, 177-178

Ninth segment of abdomen of mosquito fe-
male, 67

Ninth segment of abdomen of mosquito larva,
89

by

Nitre and powdered Jimson weed, as a fumi-
gant against mosquitoes, 375

Nitre, charcoal, and sulphur, burning, to
fumigate against mosquitoes, 372-373

Not, AuBert and Stmonp. (See Simond, Au-
bert and Noé.)

Nomenclature of malarial organisms, 189

Nosema stegomyie, parasite of yellow-fever
mosquito, 160-161

Notonecta, enemy of mosquito larve, 165

NutTTaLt and Surpiey on attraction of mos-
quitoes to sounds, 117

NourraL, and SureLtey on behavior of Ano-
pheles towards different colors, 216-218

Nurra.. and SHIPLEY on musical note of Ano-
pheles, 116, 211-212 .

Nourrat, and Suiprey on salivary pump in
Anopheles, 50

 

511

NutTTaLu and SHIPLEY on sound produced by
Anopheles, 211-212

NutTTaL, and Surpriey on traps for catching
adult mosquitoes, 378

Occipital region of head in mosquito, 42

Occiput, scales, of mosquito, 73

Ocelli of mosquito pupa, 100

Ocimum minimum, experiments, 416

Ocimum viride, alleged deterrent to mosqui-
toes, 415-416

Csophageal diverticula of mosquito, 75, 76,
71-79

CGisophageal diverticula of mosquito, func-
tion at ecdysis, 105

Cisophageal nerve-ring in mosquito, 42

Césophageal pump of mosquito, 42

Csophagus of mosquito, 42, 75, 76

Oil (see also Kerosene and Petroleum).

Oil, crude, use as mosquito larvicide on
streams having fair velocity, 386

Olfactory organ, supposed, of antenna of mos-
quito larva, 84

Ommatidia of eyes of mosquito, 87

Odcyst, definition, 190

Odkinete, definition, 190

Orange peel, burned dried, as a fumigant
against mosquitoes, 375

Oscillaria, food of Anopheles quadrimacula-
tus larvee, 150

Oscillatoria, deterrent effect on propagation
of mosquitoes, 418

OsterHouT, Dr. Pau, on dolochopodid flies
that capture mosquito larve, 170

Ovarian tube of mosquito, histology, 83

Ovaries of mosquito, 79

Ovaries of mosquito, histology, 83

Oviduct, orifice, of female mosquito, 67

Oviducts and common oviduct of mosquito,
79

Oviposition of mosquitoes, 140-145

Oviposition of mosquitoes as correlated with
shape of abdomen and appendages, 67-68

Owls, Hemoproteus noctue a blood-parasite
transmitted by Culex pipiens, 159

Oxyechus vociferus, enemy of mosquitoes, 179

PacKkarp, A. S., on Labrador mosquitoes, 137

“ Paddles ” of mosquito pupa, 99

Palatum of mosquito larva, 85, 86

Palpi, maxillary, of mosquitoes, 50-54

Palpi, scale covering in mosquito, 74

Panorpide, reported enemies of mosquitoes,
172 ;

“ Panse” of mosquito, 77

Pappataci fever, transmission by Flebotomus,
306

Paraptera of mesothorax of mosquito, 58-59

PaRKER, BEYER and PoTuHIerR on stealthiness
of attack of yellow-fever mosquito, 261-
262

Parthenogenesis in macrogametes of Plasmo-
dium, 190

PasteuR INSTITUTE (see also Institute Pas-
teur and French Commission).

PasteuR INSTITUTE, French Commission’s
work on yellow fever and mosquitoes in
Brazil, 246-252
512

“ Patagia ” of prothorax of mosquito, 55

Paunch of mosquito, 77-78

Pawpaw plant, alleged deterrent to mosqui-
toes, 415

Peat, alleged deterrent to mosquitoes, 417

Pecten of respiratory tube of mosquito larva,
88, 93

Pennyroyal oil, oil of citronella, black tar and
mutton tallow as protection against mos-
quitoes and black flies, 366

Pericardial cells of mosquito, 77, 83

Perch, pirate. (See Aphredoderus.)

“ Perch,” practical use as enemy of mosqui-
toes, 403

Permanganate of potash as mosquito larvi-
cide, 380

Pernicious fever, name for disease caused by
Plasmodium falciparum, 191

Pernicious malaria caused by Plasmodium
falciparum, 189

Perspiration, attractiveness to yellow-fever
mosquito, 113

Petrochelidon lunifrons, enemy of mosqui-
toes, 178

Petroleum (see also Oil and Kerosene).

Petroleum as mosquito larvicide, 381-383

Petroleum as mosquito larvicide, disadvan-
tages to its use in tropical regions, 383

Petroleum, saponated, and iodine as remedy
for mosquito bites or wasp stings, 377

Pettit, R. H., on destruction of mosquitoes
by Entomophthora, 157

Pewee, wood. (See Myiochanes virens.)

Phalarope, northern. (See Lobipes lobatus.)

Phalarope, Wilson. (See Steganopus tri-
color.)

Pharyngeal opening of mosquito larva, 87

Pharynx of mosquito adult, 39, 42, 43, 75-76

Pharynx of mosquito larva, 85

Phinotas oil as mosquito larvicide, 380-381,
384

Phebe, Sayornis phebe, enemy of mosquitoes,
178

“Phu-lo” plant, alleged deterrent to mos-
quitoes, 417

Phul plant, properties and uses, 417

Pike, Lucius americanus, enemy of Ano-
pheles, 408

Pipistrella europwi, host of Lecithodendrium
ascidia, 162

Pisobia bairdi, enemy of mosquitoes, 179

Pisobia maculata, enemy of mosquitoes, 179

Pisobia minutilla, enemy of mosquitoes, 179

Pistia, mosquito larve that extract air from
its submerged roots, 149

Pitcher-plant mosquito (see also Wyeomyia
smithii).

Pitcher-plant mosquito, food of larve, 151

Pitcher-plant, Sarracenia purpurea, larve of
mosquitoes found therein, 184

Plants and trees alleged to be deterrent to
mosquitoes, 413-421

Plants, enemies of mosquitoes, 156

Plants, poisonous, as mosquito larvicides, 387-
388

Plasmodiide, parasites of insects, mammals,
and birds, 159, 189
Plasmodium. 189

 

INDEX

Plasmodium, hematozoan near it found in
cases of dengue fever, 306

Plasmodium, how to diagnose the species, 190-
191

Plasmodium of monkey and other animals—
can it be transmitted to man?, 193

Plasmodium, parasites of man, monkeys, and
squirrels, 189

Plasmodium, probability of a fourth spécies,
192

Plasmodium, races resistant to quinine, 194

Plasmodium falciparum, causative organism
in pernicious, tropical, or estivo-autum-
nal malaria, 189

Plasmodium falciparum, characteristics as
seen under microscope, 191-192

Plasmodium falciparum, parthenogenesis of
macrogamete, 190

Plasmodium falciparum, various names for
disease caused by it, 191

Plasmodium malarie, causative organism in
regular quartan fever, 189

Plasmodium malarie, characteristics as seen
under microscope, 191

Plasmodium malarie, parthenogenesis
macrogamete probable, 190

Plasmodium precoz—=Plasmodium _ falci-

in

parum, 189
Plasmodium precoz, transmission to canary
birds, 261 ~

Plasmodium vivax, causative organism in be-
nign tertian fever, simple or double, 189

Plasmodium vivax, characteristics as seen
under microscope, 192

Plasmodium vivax, parthenogenesis of mac-
rogamete, 190

Plate of ninth segment of abdomen of mos-
quito larva, 89

oe trimaculata, enemy of mosquitoes,

Pleura of thorax of mosquito, 55

Pleure, vestiture, in mosquito, 74

aa membrane of abdomen of mosquito,

7

Pleural suture of mesothorax of mosquito, 58

Pleural suture of metathorax of mosquito, 59

Pleural suture of prothorax of mosquito, 57

Piiny, reference to mosquitoes’ “voice” and
to “stings” of Hymenoptera versus Dip-
tera, 8

Plover, Zgialitis semipalmata, enemy of mos-
quitoes, 179

Plover, ring-necked.
palmata.)

Plover, semipalmated.
palmata.)

“ Pneumatic sacs ” of Giles in mosquito, 78

Peciliide. (See Minnows, top.)

Poison glands and ducts of mosquito, 49-50

Poison ivy. (See Rhus toxicodendron.)

Poison of mosquito bite, 316-318

Poison of mosquitoes, discussion by Hum-
boldt, 18

Pollywogs and mosquitoes, 177

Polychromophilus, parasites of bats, 189

Posterior cross-vein of mosquito wing, 61

Packorn sclerite of mesothorax of mosquito,

(See Zgialitis semi-

(See gialitis semi-
INDEX

Fee plates of metathorax of mosquito,

Postnotum of mesotergum of mosquito, 57-58

Postnotum of mosquito, 60

Postnotum of mosquito, vestiture, 74

Postscutellum. (See Postnotum.)

Potassium permanganate. (See Permangan-
ate of potash.)

Potatoes, boiled, food of mosquitoes, 108

PotuirrR, Beyer and PARKER. (See Parker;
Beyer and Pothier.)

Poultry, hosts of Culex pipiens and C. quin-
quefasciatus, 106

Prairie mosquitoes, habits of larve, 146

Predaceous mosquito larve, 151-152

Predaceous mosquito larve inhabiting bro-
meliads, 148

Predaceous mosquito larve inhabiting water
in broken ends of bamboo, 149

Predaceous mosquito larve, mode of captur-
ing prey, 153-154

Prescutum of mesotergum of mosquito, 57

Proboscis, scale covering in mosquito, 74

Proboscis of mosquito, early accounts of
structure and mechanism, 20

Proboscis of mosquito, structure, 37-50

Proepimerum. (See Epimerum of pro-
thorax.)

Progne subis, enemy of mosquitoes, 178

Progress of nations as affected by endemic
disease, 326-328

Prosopolepis, prothoracic lobes, 59

Protergal lobe or plate of mosquito, 55

Prosternum of mosquito, 57

Protective and remedial work against mos-
quitoes, 354-449

Proteosoma, flagellate bodies, 106

Proteosoma, parasites of birds, 189

Proteosoma, parasite of birds and mosqui-
toes, studies by Koch, 196-197

Prothoracic lobes of mosquito, 59-60

Prothoracic lobes, in mosquito, vestiture, 73

Prothorax of mosquito, 55-57

Protococcus ?, food of Anopheles larve, 150

Protozoa, flagellate, food of Culex nigritulus
larva, 151

Protozoa, food of mosquito larve, 150

Protozoan parasites of mosquitoes, 159-161

Protozoan, ultra-microscopic, probable cause
of yellow fever, 257-258

Prout, Dr. W. T., on mosquitoes and Ocimum
viride, 416

Proventriculus, its homologue in mosquito,
75, 76

Pseudomyzomyia ludlowit.
ludlowii.)

Psorophora, beneficial habits of larve, 152

Psorophora, claws, 64-65 ;

Psorophora eggs, disposal and hatching, 144

Psorophora, eighth segment and its tergal
and sternal plates in female, 68

Psorophora, enemies of other mosquitoes, 167,
402

Psorophora, food of larve, 151

Psorophora, habits of larve, 147

Psorophora larve, when to find them, 185

Psorophora larve, where to find them, 184

Psorophora, length of pupal period, 155

(See Anopheles

 

513

Psorophora, male genitalia, 70

Psorophora, mouth-parts of larva, adaptation
to predaceous habit, 96-97

Psorophora, scales of legs, 74

Psorophora, tip of abdomen, cerci, 68

Psorophora, wing vestiture, 73

Psorophora ciliata, cannibalistic habits of
larvee, 168-169

Psorophora ciliata, enemies of Anopheles and
Culex larve, 167-169

Psorophora ciliata, femora, 62

Psorophora ciliata, mouth-parts of larva,
adaptation to predaceous habit, 97

Psorophora ciliata, structure of thorax, 55-59

Psorophora discolor, larva, mode of feeding,
breathing by means of gills, 153

Psorophora discolor, wing vestiture, 73

Psorphora (Janthinosoma) sayi, mouth-parts
of larva, 97

Psorophora signipennis, wing vestiture, 73

Pulvilli absent in Culicide, 67

Pumping organ of pharynx of mosquito, 75, 76

Pupal period of mosquito, 155

Purifying effect of mosquito larve upon wa-
ter, 152

Pyloric dilation of mosquito, 75, 76

Pylorus of mosquito, 75, 76

Pyrethrum carneum, synonym of Chrysan-
themum marshallii, 368

Pyrethrum powder as smudge against mos-
quitoes, 367-369

Pyrofume as fumigant against mosquitoes,
371-872

Quartan fever caused by Plasmodium ma-
lariw, 189, 191

Quarts, H. J., on drainage of California salt-
marshes, 394-396

Quinine as remedy for malaria, 194

Quinine, a substance similar to it supposedly
injected into human blood by mosquito,
188

Quinine, experiments in its use as remedy for
malaria, 199-200

Quininization. (See Cinchonization.)

Quotidian fever, name for disease caused by
Plasmodium falciparum, 191

Rachionotomyia ceylonensis, scutellar spine,
60

Railroads and other conveyances as dis-
tributors of yellow-fever mosquito, 299-
301

Railroads as carriers of mosquitoes, 345-352

Rain puddles, muddy, larve of mosquitoes
found therein, 148

Rana pipiens tadpoles not enemies of mos-
quito larve, 177

Ranatra, enemy of Anopheles larve, 170

Ranatra, enemy of mosquito larve, 165

Ranatra fusca, enemy of mosquito larve, 165

RASCHKE on respiratory system of mosquito
larvee, 89-91

Real estate, reduced value in mosquito-in-
fested regions, 328-330

Rearing methods in studying mosquitoes, 183-
185

Rearing mosquitoes, 181-182
514

RéavuMuUR on egg-laying process in Culex
pipiens, 140-141

Receptacula seminis of mosquito, 79

Reclaimed lands, value, 331-339

Rectal “ glands,” so-called, of mosquito, 76

Rectal papille of mosquito, 75, 76

Rectum of mosquito, 75, 76

ReeED and CaRRoLy on breeding places of yel-
low-fever mosquito, 284

ReEeEpD and CaRRou on effect of temperature on
biting by yellow-fever mosquito, 271

REED and CargoLs on eggs of yellow-fever mos-
quito, 281

ReeEpD and Carrott on food-habits of larve of
Aédes calopus, 288

REED and CaRRoLy on relation of food to ovi-
position in Aédes calopus, 277

ReEep and CarRoLu on temperature as affecting
development of yellow-fever mosquito,
288

Reep, death as a result of health impaired by
yellow-fever researches, 255

Reep on heroism of John R. Kissinger, who
volunteered for experiment in trans-
mission of yellow fever by bite of an in-
fected mosquito, 244

Reeds, mosquito Jarve in swamp water iso-
lated by leaves, 149

Remedial and protective work against mos-
quitoes, 354-449

Reproductive system of mosquito, 79

Reproductive system of mosquito, histology,
83

Reptiles, enemies of mosquitoes, 177

Reptiles, protozoan parasites, 159

“ Reservoir-stomach ” of mosquito, 78-79

Resin, carbolic acid and caustic-soda emul-
sion as mosquito larvicide, 385-387

Respiration in mosquito pupa, 99

Respiratory organs of mosquito larva, 89-91

Respiratory organs of mosquito pupa, 101

Resting of mosquito larve, 152-154

REyYNoLpDs, JOSEPH, on measures taken to pro-
tect crew of Cambridge from malaria in
Sierra Leone, 188

Rhamnus frangula, flowers fed upon by Cu-
lex pipiens, 111

Rhunchomyia, frontal tubercle, 36

Rhus toxicodendron, rendezvous of males of
Megarhinus septentrionalis, 132

Ricinus communis. (See Castor-oil plant.)

Riparia riparia, enemy of mosquitoes, 178

Roach, enemy of mosquitoes, 406

Robber flies (Asilide), reported enemies of
mosquitoes, 172

Roots of grass and sedges in swamps, mos-
quito larve that breathe air therefrom
and do not come to surface, 149

Rose Bengal, use in sensitizing mosquito
larve to light, 387

Rosenavu, Francis and GoLpBercer on biting
of cadavers by yellow-fever mosquito,
272

Rosrenau on formaldehyde gas as a fumi-
gant against mosquitoes, 375-376

“Rosette” form of Plasmodium malarie, 191

Ross, E. H., on breeding habits of Aédes
zammittii, 150

 

INDEX

Ross, E. H., on mosquito réle in transmis-
sion of dengue fever, 305-306

Ross, JouHn, on arctic mosquitoes, 136

Ross, Joun W., work in Cuba on mosquito
réle in yellow fever, 245

Ross, Ronabp, on amyl alcohol as diluent for
petroleum used as mosquito larvicide,
381

Ross, Ronap, on dispersal of mosquitoes, 214-

Ross, Ronatp, on ideal larvicide for mosqui-
toes, 379

Ross, RonaLp, on malaria in Greece, 326-328

Ross, RonaLp, on objects and methods of anti-
mosquito work in communities, 425

Ross, Ronaxp, on public attitudes toward
community work against mosquitoes,
423-424

Ross, Ronan, studies in development of ma-
larial parasite in Anopheles mosquitoes,
195-196

Rostrum of mosquito larva, 85

RusseELt, A. C. H., on swarming of mosquitoes
at sea, 343-344

Sabethes, femora, 62

Sabethes, male genitalia, 70

Sabethes, palpi, 52

Sabethes, prothoracic lobes and bristles, 60

Sabethes, scales of legs, 74

Sabethes, vestiture of postnotum, 74

Sabethes cyaneus, claws, 66

Sabethid larve, where to find them, 184

Sabethini, abdomen in female, 69

Sabethini, antennal structure, 29

Sabethini breeding in water of cocoanut and
of its husks, 149

Sabethini, claws, 66

Sabethini, color of pupe, 103

Sabethini, eggs and egg-laying, 145

Sabethini, expansion of apical abdominal
segments of male, 69

Sabethini, eyes, structure, 25

Sabethini, femora, 62

Sabethini, increase in size of compound eyes
in larva, 97

Sabethini, larve, modifications of structure,

Sabethini, middle tarsi, 63

Sabethini, mesonotum, 60

Sabethini, mouth-parts of larve, adaptation
to predaceous habit, 96

Sabethini, paddles of pupa, 103

Sabethini, portion of head bearing antenne,
structure, 36

Sabethini, postnotum, 60

Sabethini, prothoracic lobes, 59-60

Sabethini, shape of pupae, 103

Sabethini, tibie, 62-63

Sabethini, time of activity, 118

Sabethini, vestiture of postnotum, 74

Sabethini, vestiture of prothoracic lobes, 73

Sabethinus, food of larve, 151

sae iggaaed larva, modifications of structure,

Sabethinus, mouth-parts of larva, adaptation
to predaceous habit, 96
INDEX

Sabethinus, species breeding in water in
broken ends of bamboo, 149

Sabethinus, vestiture of postnotum, 74

Sabethinus undosus, claws, 66

Salamander or newt, Diemyctylus tortosis,
enemy of mosquito larve, 176, 402

Salamanders as enemies of mosquito larve,
176-177

Salamandra maculosa, enemy of mosquito
larve, 177

Salivary duct in mosquito, 44

Sey glands and ducts of mosquito, 49-50,

Salivary glands, histology, 81-82

Salivary pump in Anopheles, 50

Salivary “ reservoir ’”’ of Macloskie, 50

Satmon, E. P., on mites as enemies of mos-
quitoes, 172

Salt as mosquito larvicide, 388

Salticus, enemy of mosquitoes and flies, 175

Salt-marsh lands in New Jersey, drainage
and improvement, 336-339

Salt-marsh mosquitoes, habits of larve, 147

saint cai mosquitoes, migratory habits, 340-

Sampon and Low, experiment with mosqui-
toes and malaria on Roman Campagna,
197-198

Sandpiper, Baird. (See Pisobia bairdi.)

Sandpiper, least. (See Pisobia minutilla.)

Sandpiper, pectoral. (See Pisobia maculata.)

Sandpiper, semipalmated. (See Hreunctes
pusillus.)

Sandpiper, stilt.
topus.)

Sandpipers as enemies of mosquito larve, 179

Sarcopsylia penetrans. (See Chigoe.)

Sarracenia, mosquito larve in contained
liquid, 148

Sarracenia purpurea, mosquito larve in leaf-
cups or pitchers, 148, 184

Sayomyia. (See Chaoborus.)

Sayornis phebe, enemy of mosquitoes, 178

Scales of mosquito, 71-74

Scales of mosquito wing, 61-62

Scatophaga stercorarius, enemy of Corethri-
ne, 171

Scatophagid, Cordilura hamorrhoidalis, en-
emy of mosquitoes, 171

Scavenger mosquito larve inhabiting brome-
liads, 148

Scavengers among mosquito larve, 151

Schizogonic cycle of malarial organism, defi-
nition, 189

Schizonts, definition, 190

Scutirrner on feeding habits of female Ano-
pheles, 207-208

Scuwakrz on abundance of mosquitoes, 133 _

Scorpion flies (Panorpidz), reported enemies
of mosquitoes, 172

Screening against mosquitoes, cost, 331

Screening breeding places of mosquitoes, 365

Screens and canopies against mosquitoes, 359-
364

Screens, size of mesh with especial reference
to yellow-fever mosquito, 360-362, 363-364

Scutellum of mesotergum of mosquito, 57

Scutellum of mosquito and its lobes, 60

(See Micropalama himan-

 

515

Scutellum, vestiture, in mosquito, 74

Scutum of mesotergum of mosquito, 57

Seat, Wit11AM P., on relative value of vari-
ous small fish as enemies of mosquitoes,
405-407

Sea-water, mosquito larve occurring therein,
149-150

Sea-water pools and malaria, 224-227

Second marginal cell of mosquito wing, 61

Second posterior cell of mosquito wing, 61

Second vein of mosquito wing, 60, 61

Sedges and grass in marshes, mosquito larve
that extract air from roots, 149

Sending mosquito specimens by mail or ex-
press, 181

Sense-organ in antenna of Culicids, 29-34

Sensitization to light, destruction of mos-
quito larve thereby, 387

Sensory cone of antenna of mosquito larva, 84

SERGENT, EpMonp, and SERGENT, ETIENNE,
experiments in cinchonization for ma-
laria, 199-200

SERGENT, EpMoNnpD, and SERGENT, ETIENNE,
work against mosquitoes and malaria in
Algeria, 438-439

Sete of pupa of mosquito, 102

Sete of sternites of mosquito abdomen, 69

Settlement as effecting decrease in malaria,
236-239

“ Seventh vein ” of Theobald, 61

Sewer breeding of mosquitoes, prevention,
390-391

Sexual cycle of malarial organism, definition,
189

Shaft of mosquito antenna, structure, 26-29

Shiner. (See Roach.)

SHipLry and NUTTALL.
Shipley.)

SHIPLEY and Wison on stridulating appa-
ratus of Anopheles, 115

Surptey, A. E., on geographical distribution
of malaria, 233-234

Suipetey, A. E., on malarial ravages in India
and Africa, 324

Ships as carriers of mosquitoes, 345-352

Ships as carriers of yellow-fever mosquito,
298-299

Shore birds as mosquito destroyers, 179

Shrimps, fresh-water, enemies of mosquitoes,
176

Shrimps, salt-water, enemies of salt-marsh
mosquito larve, 176

Side-pieces of male genitalia of mosquito, 69-

(See Nuttall and

71

Silverfish, practical use as enemies of mos-
quitoes, 408

Smmonp, AUBERT and No& on supposed noctur-
nal habits of yellow-fever mosquito, 268

Srmonp and MarcHoux. (See Marchoux and
Simond.)

Simuliide called “mosquitos” in Spanish-
American countries, 10

Simuliide, plague to live stock in southern
Russia, account by Jaeger, 18-19

Simulium, enemy of fish, 108

Simulium, enemy of mosquitoes, 171

Simulium, mouth-parts, 45-49

Simulium, palpi, 53
516

Siphon, respiratory, of mosquito larva, 88, 91

Siphons, respiratory, of pupa of mosquito, 99,
101, 102-103

Sixth vein of mosquito wing, 61

SKUSE on spread of Culex quinquefasciatus
along railroads and by vessels, 347

Slide mounts for mosquitoes, 182-183

Smilax herbacea and 8. hispida, flowers vis-
ited by Aédes stimulans, 111

Situ, A. C., experiment in control of yellow
a by screening against mosquitoes,
242

SmirH, GEorGE OTIs, on malaria as a check
a field work of U. S. Geological Survey,

23

Smitu, JouHn B., on breeding places of Ano-
pheles, 219

SmirH, JoHN B., on breeding places of Ano-
pheles punctipennis and A. quadrimacu-
latus, 222

SmitH, JoHNn B., on drainage of New Jersey
salt-marshes and its value, 337-338

Situ, JOHN B., on poison of mosquito bite,
317-318

SmirH, Joun B., on reduced value of real
estate in mosquito-infested regions, 328-
330

SmiTH, JoHN B., on relative susceptibility of
persons to mosquito poisoning, 318-319

SmirH, JoHN B., on screening houses against
mosquitoes, 359

SmitH, JoHNn B., work against mosquitoes in
New Jersey, 397-402

Smoke as repellent against mosquitoes, 14, 17,
18

Smudges and fumigants against mosquitoes,
367-376

Snail (Limnea ovata), host of Distomum
globiporum, 162

Snakes, hosts of mosquitoes, 108

Snoperass, R. E., study of thorax of Psoro-
phora ciliata, 55-59

Soap, effect on larve of yellow-fever mos-
quito, 290

Soap, moist, as remedy for mosquito bites,
377

Solidago canadensis, 8. juncea and S. lanceo-
lata, flowers visited by Aédes sylvestris,
111-112

Songs and hearing power of mosquitoes, 114-
117

Sounds, attraction of mosquitoes thereto, 116-
117

South America, geographical distribution of
malaria, 234

Sparrows, malarial disease, transmission by
Culex quinquefasciatus, 106

Spermathece and ducts of mosquito, 79

Spermatheca of mosquito, histology, 83

SPENSER, accounts of mosquitoes in “ Faerie
Queene ” and “ View of Ireland,” 9

Sphagnum swamps, mosquito larve found
therein, 148

Spiders, enemies of mosquitoes, 175-176

“Spinose” arrangement of scales of costal
margin of mosquito, 73

Spiracles of mosquito, 55, 67, 80

 

INDEX

Spirocheta parasite of Anopheles maculi-
pennis, 160
Spirocheta parasite of mosquitoes in India,

Spirocheta culicis, parasite of mosquito, 160

Spirogyra, food of Anopheles quadrimacula-
tus larve, 150

Sporoblasts, definition, 190

Sporogonic cycle of malarial organism, defi-
nition, 189

Sporotrichum, effect on chinch bugs, 157

Sporozoa in adult ovum of Anophelines, 83

Sporozoa, parasites of mosquitoes, 159, 188

Sporozoit of Plasmodium, possibility of he-
reditary transmission to egg of mosquito,
193

Sporozoits, definition, 190

Spots on integument of Anopheles and Aédes
fuscus, 73

Spring-hole mosquito, Culex melanurus, 154

Springs as breeding places for Anopheles in
Algeria, 220

Spurs of tarsal joints of mosquito, 63

Squirrels, hosts of Plasmodium, 189

Staining slide preparations of malarial para-
site, 191

Steganopus tricolor, enemy of mosquitoes, 179

Stegoconops, claws, 64

Stegoconops, hatching of eggs of species
breeding in tree-holes, 145

Stegoconops larve inhabiting sea-water and
fresh water, 150

Stegoconops, larval habits of species which
breed in hollow trees, 147

Stegoconops, palpi, 53

Stegoconops, species breeding in water in
broken ends of bamboo, 149

Stegoconops albomaculatus, claws, 65

Stegoconops albomaculatus, palpi, 53

Stegoconops capricorni, claws, 65

Stegoconops equinus, palpi, 53

Stegomyia “ brigade” in Havana, work, 429-
430

Stegomyia, untenability of generic concept, 6

Stegomyia calopus (see also Stegomyia fasci-
ata, Aédes calopus and Yellow-fever mos-
quito).

Stegomyia calopus, escape from 16-mesh wire
screen, 364

Stegomyia fasciata (see also Stegomyia cal-
opus, Aédes calopus and Yellow-fever
mosquito).

Stegomyia fasciata, breeding places, 223

Stegomyia fasciata in Egypt, 428

Stegomyia fasciata, macrosomia and mic-
rosomia, 361-362

Stegomyia pagens, breeding places, 223

Stellate hairs of Anopheles larva, 229

Stellate tufts of Anopheles larva, 91

STEPHENS and CHRISTOPHERS on anatomy, in-
ternal, of female Anopheles, 75-83

STEPHENS and CHRISTOPHERS on a prophylac-
tic method against malaria at Accra,
Gold Coast, 200-202

Sternum of abdomen of mosquito, 67

Sticklebacks, practical use as enemies of mos-
quitoes, 403, 408

Stigmata of air-cavity of mosquito pupa, 100
INDEX

STILEs on European forms of Agamomermis
infesting mosquitoes, 162

“Stings” of Hymenoptera versus Diptera,
comparison by Pliny, 8

Stock killed by “ mosquitoes” (Simuliide) in
southern Russia, 19

Stomach, so-called, of mosquito, 75

Stomorys, bite of Simuliide compared
thereto, 13
Stramonium. (See Jimson weed.)

Stridulating organ of Anopheles, 115

Subcostal cross-vein of mosquito wing, 61

Subintrant attacks of malignant tertian fever,
explanation, 193

Subcostal cell of wing of mosquito, 60, 61

Submarginal cell of wing of mosquito, 61

“ Submentum ” of mosquito larva, 87

“ Sucking stomach ” of insects, 77-78

Sulphate of copper as mosquito larvicide, 380

Sulphate of potash as protection against mos-
quito bites, 366

Sulphur dioxide as a fumigant against mos-
quitoes, 372-374

Sulphur, nitre, and charcoal, burning, to
fumigate against mosquitoes, 372-373

Sunfish, black-banded. (See Mesogonistius
chetodon.)

Sunfish, enemies of mosquitoes, 406

Sunfish or pumpkinseed, practical use as
enemy of mosquitoes, 403, 408

“Supernumerary ” cross-vein of mosquito
wing, 61

Swallows as mosquito destroyers, 178

Swamp and overtiowed lands of the United

States, area, present and potential value
and cost of drainage, 333-335
Swamp land, reclaimed, value, 331-339
Swarming habits of mosquitoes, 120-132

Tabanid, Lepiselaga, prey of Monedula sig-
nata, 171

Tachycineta thalassina lepida, enemy of mos-
quitoes, 178

Tachydromia macula, enemy of mosquitoes,
171

Tadpoles and mosquitoes, 177

Tadpoles living in water in bromeliaceous
plants, 221

Teniorhynchus. (See Mansonia.)

Tamura, Dr. K., on mosquitoes and malaria
in Formosa, 437

Tanypus, predaceous habits of larve, 169-170

Tanypus dyari larve, enemies of mosquito
larve, 170

Tar, black, oil of citronella, oil of pennyroyal
and mutton tallow as protection against
mosquito bites, 366

Tarsal joints of mosquito, relative length on
different legs and in different species, 63-
64

Tarsi of mosquito, 63 . :

“ Tasterschuppe ” of mosquito palpi, 51

Taytor on biting habits of yellow-fever mos-
quito, 263 :

Teeth of claws of mosquito, 64-66

Temperature (see also Climate).

Temperature as affecting development of yel-
low-fever mosquito, 288-289

 

517

Temperature as affecting eggs of yellow-fever
mosquito, 281-283

Temperature conditions governing distribu-
tion of Aédes calopus, 292-294

Temperature, effect on early stages and adult
of Aédes calopus, 302

Temperature, influence on sexual activity of
yellow-fever mosquito, 275

Temperature, influence on yellow-fever mos-
quito, 271-272

‘“ Tempraneros,” name used for mosquitoes
in Spanish-American countries, 10

Tenth segment of abdomen of female mos-
quito, 67

Tergum of abdomen of mosquito, 67

Tergum of metathorax of mosquito, 59

Terrapin, host of mosquitoes, 108

Tertian fever, benign, simple or double,
caused by Plasmodium vivax, 189, 192-
193

THEOBALD, Classification of scales in Culicide,
71-72

THEOBALD on abundance of mosquitoes, 132

THEORALD on phytophagous habits of Culi-
cide, 111

THEOBALD on plant-feeding habits of Culiseta
annulatus, 110

THEOBALD on practical uses of water plants
against mosquitoes, 418

THIBAULT, JAMES K., Jz., on mites as para-
sites of mosquitoes, 173-174

THIBAULT, JAMES K., JR., on normal relation
between mosquitoes and fish, 412

Third appendage of abdomen of female mos-
quito, 67

Third posterior cell of mosquito wing, 61

Third vein of mosquito wing, 60, 61

THOMPSON, CONSUL, on mosquitoes and castor-
oil plants, 414

THompson on labrum and adjoining parts of
mosquito larva, 85-86

Thoracic vestiture of mosquito, 73-74

Thorax of mosquito adult, 55-60

Thorax of mosquito larva, 88

Thorax of mosquito pupa, 101

“Thread bug,’ Emesa longipes, capturing
mosquitoes, 172

Tibie of mosquito, 62-63

“ Tibial scraper ” in mosquitoes, 63

Time of activity of mosquitoes, 118

Tipula, first spiracle and epimerum, 57

Tipula, mesoepisternum, 58

Tipula, palpi, 53

“Tipulaires,’ name used by Humboldt for
biting Nemocera, 10

Toads, enemies of mosquitoes, 176

Torus of antenna of mosquito, scale covering
in some species, 74 /

Torus of antenna of mosquito, structure, 26

Tosinrt and Fermi. (See Fermi and Tosini.)

Townsenp, C. H., on mosquitoes in Alaska,
138

Trachex of mosquito, 80

Tracheal gills of mosquito larva, 89, 90-91, 94

Tracheal system of mosquito adult, 80

Tracheal system of mosquito larva, 89-91

Traps for catching adult mosquitoes, 377-378

Tree-hole mosquitoes, 151
518

Tree-hole mosquitoes, hibernation as larve,
154

Trees and plants alleged to be deterrent to
mosquitoes, 413-421 *. _
Trees, hollows, habits of larve occurring
therein, 147,148 ~~ “|. . S
Trematode parasites of mosquitoes,*162
Triple q urtan‘fever, explanation, 193
Triton alpestris, enemy of mosquito larve,
2 176 on!
Triton cristatus, enemy of mosquito larve,
176 -
Trochanters of mosquito, 62
Tropical. fever, name disease caused by
Plasmodium: falciparum, 191 ;
», Tropical malaria caused by Plasmodium fal-
“"~ eipartim, 189
Tropical ulcer and other skin diseases, sug-
gested carriage by mosquitoes, 316
“Trumpets, respiratory.” (See Siphons, re-
spiratory.)
Trunks, Aédes calopus hiding and conveyed
therein, 347
Trypanosoma culicis, parasite of mosquitoes;
‘% belongs to genus. Herpetomonas, 161
“Tuba'root.” (See Derris elliptica.)
Tubdifex, prey of Tanypus larve, 169-170
Tyrannidz, enemies of mosquitoes, 178
Tyrannus tyrannus, enemy of mosquitoes, 178

UHLER on the practicability of artificially
_ breeding dragon flies to abate the mos-
quito nuisance, 166
Ulcer, tropical, and other skin diseases, sug-
gested carriage by mosquitoes, 316 -

Umbra, enemy of mosquitoes, 406, 408

Unci of male genitalia of mosquito, 69-71
Unverwoop, W.-L., on goldfish as enemies of
mosquitoes, 404 .

UnpErwoep, W.d., on predaceous habits of
larve of Eucorethra underwoodi, 169
UniTeD States Army CoMMISsIon, demon-

stration of mosquito réle in yellow fever,
243-245
Unitrep States Puslic HEALTH AND MARINE-
HOospiTaL SERVICE on habitat and artifi-
cial distribution of yellow-fever mos-
quito, 300-301
Unitrep States PusLtic HEALTH AND MARINE-
. HospiraL SeRyIcE on transportation of
_ Mosquitoes by ships, 348-350
Unitep States PusLic HEALTH AND MARINE-
‘Hospiran Service, regulations for fruit
vessels visiting yellow-fever ports, 267-
268 :

Unitep StaTES PuBLIc HEALTH AND MARINE-
HospitaL SEerVIcE, YELLOw Fever Insti-
TUTE, WORKING Party AT VERA CrUz, con-
clusions on yellow fever, its organism
and its transmission, 256-257

_Uranotenia, antennal structure, 28

“Uranetienia, claws, 65

Uranotania egg-mass, 142

Uranotenia, eggs and oviposition, 140

Uranotenia, habits of larve, 147

nee larva, attitude at surface film,

 

INDEX

Uranotenia larva, modifications of structure,
93, 94

Uranotenia larve abundant among dense
alge, 418

Uranotewnia, longevity, 119

Uranotenia, male genitalia, 70

Uranotenia, membranous cushion of tarsi, 66

Uranotenia, palpi, 52, 54

Uranotenia, second vein, 61

Uranotenia, spermatheca, 79

Uranotenia, tip of abdomen, cerci, 68

Uranotenia, wing vestiture, 72

Uranotenia argyropus, abundance, 132

Uranotenia geometrica, antennal structure,
28

Uranotenia lowii, antennal structure, 28

Uranotenia lowii, escape from 16-mesh wire
screen, 364

Uranotenia sapphirinus, antennal structure,
28

Uranotenia sapphirinus egg-mass, 142

Uranotenia sapphirinus, palpi, 54

Utricularia, enemies of mosquito larve, 156

Utricularia clandestina, enemy of mosquito
larve, 156

Vacuum cleaner, use for catching mosquitoes
and flies, 379

Van Ding, D. L., on mosquitoes in Hawaii, 344

Vascular system of mosquito, 77

Vascular system of mosquito, histology, 82-83

Vaseline and oil of citroneila as protection
against mosquito bites, 366

VEAZIE on diurnal habits of yellow-fever mos-
quito, 263

Veils against mosquitoes, 360

Veins of wings of mosquito, 60-61

Ventral brush of mosquito larva, 89

Ventral pleural plate of metathorax of mos-
quito, 59

Venus’s fly-trap (Dionea muscipula), insec-
tivorous structure and function, 156

Vera Cruz, Seconp CoMMISSION, on ovipo-
sition of yellow-fever mosquito, 279

VERA CRUZ, YELLOw FrveR Commission, on be-
ae of larve of yellow-fever mosquito,

Verbascum. (See Phul plant.)

Vermes, enemies of mosquitoes, 162-164

Vertex, scales, of mosquito, 73

Vestiture of mosquito, 71-74

VIERECK on Ranatra fusca as an enemy of
mosquito larvee, 165

“Vomito negro” name for yellow fever in
Spanish America, 296

“ Vomito prieto,” early name for yellow fever
in Spanish America, 296

“Vorratsmagen ” of mosquito. 78

Vorticella causing death of an Anopheles
larva, 161

Vorticellids found upon mosquito larva, 161

WAHLBERG on empidid and scatophagid ene-
mies of mosquitoes, 170-171

WAHLBERG on mating habits of northern mos-
quitoes (Aédes), 129-130

Warner, S. P., on crusade against malaria in
Leipzig, 427-428
INDEX

Wasp enemies of mosquitoes, 171

Wasp stings, remedy, 377? a

Water beetles resistant to larvicide of Isth-
mian Canal Commission, 387

Water, brackish, breeding’ of yellow-fever
mosquito therein, 289-290

Water charged with animal refuse and fecal
oo mosquitoes that breed therein,

a

Water cress. (See Nasturtium officinale.)

Water, drinking, supposed purity of that in
which Culex or Aédes larve occur, 152

Water, fresh, mosquito larve occurring
therein 149-150

Water fowl, probable hosts of Culex erythro-
thoraz, 107

Water from snows, habits of mosquito larve
found therein, 146

Water in broken ends of bamboo, mosquitoes
breeding therein, 149

Water in bromeliads, habits of mosquito
larve found therein, 147-148

Water in cocoanut and cacao husks, mosqui-
toes breeding therein, 149 ie

Water in crab-holes, mosquito larye found
therein, 149

Water in hollow trees, habils of mosquito
larve found therein, 147

Water in salt-marshes, habits of mosquito
larve found therein, 147

Water isolated by leaves of reeds, mosquitoes
breeding therein, 149 .

Water, permanent bodies, habits of mosquito”
larve occurring therein, 147

Water plants deterrent to mosquito larve,
417-421

Water, saline, mosquito larve occurring
therein, 149-150

ee spring, mosquito larva living therein,

54

Water, temporary deposits on arid or semi-
arid plains, habits of larve found therein,
146-147

Watermelon, food of mosquitoes, 108

Weaver, A. Dr P., on attraction of mosquitoes
to sounds, 116-117

SS H. C., on value of drainage work, 335-

Whip-poor-will (Antrostomus vociferus), en-
emy of mosquitoes, 178

“Whirligig beetles.” (See Gyrinide.)

WHITE, GILBERT, on swarming habits of Ne-
mocera, 125

WauitnEy, MirTon, on value of reclaimed
swamp land, 331-332

Wipney, J. P., on irrigation and malaria, 239-
240

Witucocks, F. C., on aerial dances of male
mosquitoes, 129

Wituiston on palpi of Diptera, 51

Willow catkins frequented by Aédes spenceri,
112

Willow catkins frequented by mosquitoes, 111

Wing processes, notal, of mesothorax of mos-
quito, 58

Wing processes,
mosquito, 58

Wing processes,

pleural, of mesothorax of

pleural, of metathorax of

 

mosquito, 59

519

Wing, shape, of mosquito, 62

Wing veins of mosquito, 60-61

Wing vestiture of mosquito, 72-73

Wings of mosquito, 60-62

Wings of pupa of mosquito, 101

Wind, influence on dispersal of mosquitoes,
339-345

Wolffia arhiza (see also Lemna arrhiza).

Wolfia arhiza, deterrent to mosquito larve,
419-420

Wricut, J. O., on the swamp and overflowed
lands of the United States, 333-335

Wyeomyia, food of larve, 151

Wyeomyia, habits of larve, 149

Wyeomyia larve, mode of feeding, 153

Wyeomyia larve, where to find them, 184

Wyeomyia, mouth-parts of larva, 96

Wyeomyia, species from Trinidad and Pan-
ama, eggs and their disposal, 145

Wyeomyia circumcincta, claws, 66

Wyeomyia circumcincta, respiratory trum-
pets of pupa, 103

Wyeomyia codiocampa, abdomen, shape in
female, 68

Wyeomyia eloisa, male genitalia, 70

Wyeomyia smithii, adaptation of larve to
single habitat—the leaves of the pitcher-
plant, 148

Wyeomyia smithii, claws, 66

Wyeomyia smithit eggs and their disposal,
145

Wyeomyia smithii, food of larve, 151

Wyeomyia smithii, hibernation of larva, 120,
154

Wyeomyia smithii not a blood-sucker, 110

Wyeomyia-trinidadensis, claws, 66

Wyman, Watter, letter to L. O. Howard on
time of activity of yellow-fever mosquito,
268

| Yeast, Myzxococcidium stegomyie, and yellow

fever, 256-257

Yeasts, their réle in the bodies of mosquitoes,
158-159

Yellow fever, 241-303

Yellow fever and its transmission, work of

' Marchoux and Simond, 246-252

Yellow fever and mosquitoes in Panama, 431-
432

Yellow fever and mosquitoes in Rio de Jan-
eiro, 432-435

Yellow fever and mosquitoes in Vera Cruz
and Mexico generally, 435-436

Yellow fever, causative organism, search
therefor, 255-258

Yellow fever, deaths in New Orleans, 1847-
1905, 254

Yellow fever, deaths in Rio de Janeiro, 1872
to August, 1909, 434-435

Yellow fever, deaths in United States in dif-
ferent years, 325-326

Yellow fever in Europe, 301-303

Yellow fever, Laredo outbreak of 1903, 252-.
258 ;

Yellow fever, loss therefrom, 325-326

Yellow fever, micro-organism producing it
still undiscovered, probably too minute
to be seen by microscope, 245
520

Yellow fever, mosquito Tole, demonstration
by United States Army Commission, 243-
245

Yellow fever, mosquito Pole; Dr. A. C. Smith’s

: experiment, 242 >

Yellow fever, mosquito ° ‘role, Finlay’s work,
242°

Yellow fever, ‘mosquito réle, work in Brazil
by Sao Paulo ahd French Commissions,
245-252

Yellow fever, mosquito réle, work in Cuba
by Guiteras and John W. Ross, 245

Yellow fever, name in Aztec, 295

Yellow fever, names used in Spanish Amer-
ica, 296

Yellow “fever, New Orleans epidemic of 1905,

253-255

Yellow fever on shipboard, 348-349, 350-352

Yellow fever on upper Amazon, source, 348

Yellow fever, original endemic foci, 294-298

Yellow-fever outbreaks in north, explanation,
345-347

‘Yellow fever produced by active toxin in
filtered lymph or by ultra-microscopic
organism, 255-256

Yellow fever, scientific demonstration of car-
riage by mosquitoes, 241-255

Yellow-fever mosquito (see also Aédes calo-
pus, Stegomyia calopus and Stegomyia
fasciata).

Yellow-fever mosquito, 258-303

Yellow-fever mosquito, activity, time, 262-270

Yellow-fever mosquito, adult, length of life,
270-271

Yellow-fever mosquito, artificial means of
distribution, 298-301

Yellow-fever mosquito, behavior of larve, |

286-287
Yellow-fever mosquito, biting of cadavers, 272
Yellow-fever mosquito, breeding habits, 281-
292
Yellow-fever mosquito, breeding places, 283-
6

Yellow-fever mosquito, changes in scientific
name, 6

Yellow-fever mosquito, distance of flight, 272-
275

Yellow-fever mosquito, distribution by arti-
ficial means, 298-301

Yellow-fever mosquito,
graphical, 292-294

distribution, geo-

 

INDEX

Yellow-fever mosquito, diurnal habits, 262-270

Yellow-fever mosquito, domesticity, 258-259

Yellow-fever mosquito, duration of early
stages, 288-289

Yellow-fever mosquito eggs, conditions af-
fecting them, 281-283

Yellow-fever mosquito eggs, disposal, 278-280

Yellow-fever mosquito, feeding habits of
adult, 106, 259-262

Yellow-fever mosquito, feeding habits of lar-
ve, 287-288

Yellow-fever mosquito, flight, distance, 272-
275

Yellow-fever mosquito, food in relation to ovi-
position, 277-278

Yellow-fever mosquito, geographical distri-
bution, 292-294

Yellow-fever mosquito, geographical distri-
bution in North America, 3-4

Yellow-fever mosquito, host of Nosema steg-
omyie, manner of infection, 160-161

Yellow-fever mosquito in Europe, 301-303

Yellow-fever mosquito, influence of tempera-
ture thereon, 271-272

Yellow-fever mosquito larve, behavior, 286-
287

ae ae mosquito larve, food habits, 287-

8

Yellow-fever mosquito larve, resistance to
adverse conditions, 289-292

uae mosquito, length of life of imago,

771

Yellow-fever mosquito, mating, 275-276

Yellow-fever mosquito, original home, 294-298

Yellow-fever mosquito, oviposition, 278-280

Yellow-fever mosquito, oviposition, food in re-
lation thereto, 277-278

Yellow-fever mosquito,
205

Yellow-fever mosquito, successful rearing in
captivity, 132

Melia Fee Mosquito, time of activity, 262-

Youne, Caprain, on swarm of mosquitoes in
Gulf of Mexico, 342-343

semidomestication,

“ Zancudos,” name used for mosquitoes in
Spanish-American countries, 10
oe on development of eyes of mosquitoes,
7-88
ZIEMANN on occurrence of malaria at high al-
titudes, 235
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