^>;^. 
 ^^u 
 
 LIBRARY OF 
 
 1685-1056 
 

ENTOMOLOGY 
 
 FOLSOM 
 
DESCRIPTION OF FRONTISPIECE. 
 Protective Mimicry among Butterflies. 
 
 Fig. I. — Hcliconius ei'crate, one of the Helicoiiiinx, wliicli are iiaturally iiiiniuiic from 
 the attacks of birds. From Brazil. 
 
 Fig. 2. — Perhybris pyrrha, female (Pierinas), which is edible by birds but ))robably 
 secures immunity by means of its resembiaiice to such species as No. i or No. 4. 
 Brazil. 
 
 FiG. 3. — Perhybris pyrrha, male, to show the colorational basis from which the 
 mimetic pattern of the female has been developed; under surface on right. Brazil. 
 
 Fig. 4. — Mechanitis lysimnia (.Ithomiins), naturally immune, but nevertheless 
 sharing a common color pattern with Heliconiinas (No. i). Brazil. 
 
 Fig. 5. — Papilio merope, male, having three forms of females ( Nos. 7, 9 and 11), 
 which mimic, respectively, three species of Danainse (Nos. 6, 8 and 10). South 
 Africa. 
 
 Fig. 6. — Danais chrysippus, irnmune, mimicked by No. 7. South Africa. 
 
 Fig. 7. — Papilio merope, female, which mimics No. 6. South Africa. 
 
 Fig. 8. — Amauris niavius, " model " of No. 9. South .Africa. 
 
 Fig. 9. — Papilio merope, female, " mimic " of No. 8. South Africa. 
 
 Fig. 10. — Amauris ccheria, "model" of No. 11. South Africa. 
 
 Fig. II. — Papilio merope, female, "mimic" of No. 10. South Africa. 
 
 The figures are about one half the natural size. Compiled, largely from Trimen 
 and Weismann. 
 
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ENTOMOLOGY 
 
 WITH SPECIAL REFERENCE TO 
 
 ITS BIOLOGICAL AND ECONOMIC ASPECTS 
 
 JUSTUS WATSON FOLSOM. Sc.D. (Harvard) 
 
 INSTKICTOR IN ENTOMOLOGY AT THE UNIVEKSH Y OF ILLINOIS 
 
 lUitb jfive plates (One ColoreD) 
 
 PHILADELPHIA : 
 BLAKISTON'S SON & CO. 
 
 IOI2 WALNUT STREET 
 1906 
 
Copyright, 1906, by P. Blakiston's Son & Co. 
 
PREFACE 
 
 This book gives a comprehensive and concise account of 
 insects. Though planned primarily for the student, it is in- 
 tended also for the general reader. 
 
 The book was written in an effort to meet the growing 
 demand for a biological treatment of entomology. 
 
 The existence of several excellent works on the classification 
 of insects (notably Comstock's Manual, Kellogg's American 
 Insects and Sharp's Insects) has enabled the author to omit 
 the multitudinous details of classification and to introduce 
 much material that hitherto has not appeared in text-books. 
 
 As a rule, only the commonest kinds of insects are referred 
 to in the text, in order that the reader may easily use the text 
 as a guide to personal observation. 
 
 All the illustrations have been prepared by the author, and 
 such as have been copied from other works are duly credited. 
 
 To Dr. S. A. Forbes the author is especially indebted for 
 the use of literature, specimens and drawings belonging to the 
 Illinois State Laboratory of Natural History. 
 
 Permission to copy several illustrations from Government 
 publications was received from Dr. L. O. Howard, Chief of 
 the Bureau of Entomology; Dr. C. Hart Merriam, Chief of 
 the Division of Biological Survey, and Dr. Charles D. Walcott, 
 Director of the U. S. Geological Survey. Several desired 
 books were obtained from F. M. Webster, of the Bureau of 
 Entomology. 
 
 Acknowledgments for the use of figures are due also to 
 Dr. E. P. Felt, State Entomologist of New York; Dr. E. A. 
 Birge, Director of the Wisconsin Geological and Natural His- 
 tory Survey; Prof. E. L. Mark and Prof. Roland Thaxter, 
 of Harvard University ; Prof. J. H. Comstock of Cornell Uni- 
 versitv; Prof. C. W. Woodworth of the Universitv of Cali- 
 
VI PREFACE 
 
 fornia ; Prof. G. Macloskie of Princeton University ; Prof. \V. 
 A. Locy of Northwestern University ; Prof. J. G. Needham 
 of Lake Forest University ; Dr. S. H. Scnckler of Cambridge, 
 Mass. ; Dr. George Dimmock of SpringfiekJ, Mass. ; Dr. 
 Howard Ayers of Cincinnati, Ohio ; Dr. W. M. Wheeler of 
 the American Museum of Natural History, New York City; 
 Dr. W. L. Tower of the University of Chicago ; Dr. A. G. 
 Mayer, Director of the Marine Biological Laboratory, Tortu- 
 gas, Fla. ; James H. Emerton of Boston, Mass. ; Dr. and Mrs. 
 G. W. Peckham of Milwaukee, Wis. ; Dr. Henry C. McCook 
 of Devon, Penn. ; Dr. William Trelease, Director of the Mis- 
 souri Botanical Garden ; Dr. Henry Skinner, as editor of " En- 
 tomological News " ; the editors of " The American Natural- 
 ist " ; and W. Saville-Kent, of Wallington, England. 
 
 Acknowledgments are further due to the Boston Society of 
 Natural History, the American Philosophical Society and the 
 Academy of Science of St. Louis. 
 
 Courteous permission to use certain figures was given also 
 by The Macmillan Co. ; Henry Holt & Co. ; Ginn & Co. ; Prof. 
 Carl Chun of Leipzig; F. Diimmler of Berlin, publisher of 
 Kolbe's Einfiihrung; and Gustav Fischer of Jena, publisher of 
 Hertwig's Lehrbuch and Lang's Lehrbuch. 
 
CONTENTS 
 
 Chapter Page 
 
 I. Classification i 
 
 II. Anatomy and Physiology 27 
 
 III. Development 146 
 
 IV. Adaptations of Aquatic Insects 184 
 
 \'. Color and Coloration 193 
 
 \' I. Adaptive Coloration 216 
 
 VII. Origin of Adaptations and of Species 237 
 
 VIII. Insects in Relation to Plants 252 
 
 IX. Insects in Relation to Other Animals 276 
 
 X. Interrelations of Insects 307 
 
 XL Insect Behavior 345 
 
 XII. Distribution 366 
 
 XIII. Insects in Relation to Man 393 
 
 Literature 409 
 
 Index 467 
 
ENTOMOLOGY 
 
 CHAPTER I 
 
 CLASSIFICATION 
 
 At the outset it is essential to know where insects stand in 
 relation to other animals. 
 
 Arthropoda. — Comparing an insect, a centipede and a 
 crayfish with one another, they are found to have certain 
 fundamental characters in common. All are bilaterally sym- 
 metrical, are composed of a linear series of rings, or segments, 
 bearing paired, jointed appendages, and have an external 
 skeleton, consisting largely of a peculiar substance known as 
 chitin. 
 
 If the necessary dissections are made, it can be seen that 
 in each of these types the alimentary canal is axial in position : 
 
 Diagram to express the fundamental structure of an arthropod, a, antenna; al, 
 alimentary canal; b, brain; d, dorsal vessel; c.v, exoskeleton; /, limb; n, nerve chain; 
 s, suboesophageal ganglion. — After Schmeil. 
 
 above it extends the dorsal blood vessel and below lies the 
 ventral ladder-like series of segmental ganglia and paired 
 nerve cords, or commissures ; between the commissures that 
 connect the brain and the suboesophageal ganglion passes the 
 oesophagus. These relations appear in Figs, i and 163. 
 
ENTOMOLOGY 
 
 Fig 
 
 Furthermore, the sexes are ahnost invariably separate and the 
 primary sexual organs consist of a single pair. 
 
 No animals but arthropods have all these characters, though 
 the segmented worms, or annelids, have some of them — for 
 example the segmentation, dorsal heart and ventral nervous 
 
 chain. On account of these 
 correspondences and for other 
 weighty reasons it is believed 
 that arthropods have de- 
 scended from annelid-like an- 
 cestors. Annelids, however, 
 as contrasted with arthropods, 
 have segments that are essen- 
 tially alike, have no external 
 skeleton and never have 
 paired limbs that are jointed. 
 Classes of Arthropoda. — 
 Excepting the king-crab, tri- 
 lobites and a few other aber- 
 rant forms of uncertain posi- 
 tion, the members of the 
 series, or phylum, Arthropoda 
 fall into six distinct classes, 
 namely, Crustacea, Arach- 
 nida, Malacopoda, Diplopoda, 
 Chilopoda and I n s e c t a . 
 These classes are character- 
 ized as follows : 
 
 Crustacea. — Aquatic, as a 
 rule. Head and thorax often united into a cephalothorax. 
 Numerous paired appendages, typically biramous (Y-shaped) ; 
 abdominal limbs often present. Two pairs of antennae. Res- 
 piration branchial (by means of gills) or cutaneous (directly 
 through the skin). The exoskeleton contains carbonate and 
 phosphate of lime in addition to chitin. Example, cray- 
 fish. 
 
 scorpion, Buthus. Natural size. 
 
CLASSIFICATION 
 
 3 
 
 Arachnida. — Terrestrial. Usually two re,Q'ions, ccphalo- 
 thorax and abdomen; thoui^'h xarioiis Acarina lia\c but cjiie 
 and Solpngida have all three — head, thorax and abdomen. 
 Ceplialothorax unsegmented, bearing two pairs of oral append- 
 
 FlG. 3. 
 
 Pcripafus cafensis. Natural size. — After Moseley. 
 
 Fic 
 
 ages and four pairs of legs. Abdomen segmented or not, 
 limbless. Respiration tracheal, by means of book-leaf tra- 
 cheae, tubular tracheae, or both ; stigmata almost always abdom- 
 inal, at most four pairs. Heart abdominal in position. 
 Example, Buthiis (Fig. 2). 
 
 Malacopoda. — Terrestrial. 
 Vermiform (worm-like), unseg- 
 mented externally. One pair of 
 antennae, a pair of jaws and a 
 pair of oral slime papillae. Legs 
 numerous, paired, imperfectly 
 segmented. Respiration by means 
 of tubular tracheae, the stigmata 
 of which are scattered over the 
 surface of the body. Numerous 
 nephridia (excretory) are pres- 
 ent and these are arranged seg- 
 mentally in pairs. Two separate 
 longitudinal nerve cords, con- 
 nected by transverse commissures, 
 single genus. Pcripafus (Fig. 3), comprising many species. 
 
 Diplopoda. — Terrestrial. Two regions, head and body. 
 Body usually cylindrical, w'ith numerous segments, most of 
 which are double and bear two pairs of short limbs, which are 
 inserted near the median ventral line. Eyes simple, antennae 
 
 A diplopod, Spiroholus marginatum 
 Natural size. 
 
 Integument delicate. A 
 
ENTOMOLOGY 
 
 Fig. 5. 
 
 short, mouth parts consisting of a pair of mandibles and a 
 compound plate, or gnathochilarium. Genital openings sepa- 
 rate, anterior in position (on the second segment of the body). 
 Example, Spiroholus (Fig. 4). 
 
 Chilopoda. — Terrestrial. Two regions, head and body. 
 Body long and flattened, with numerous segments, each of 
 which bears a pair of long six- 
 or seven-jointed limbs, which are 
 not inserted near the median line. 
 Eyes simple and numerous (ag- 
 glomerate in Scutigcra) , antennae 
 long. A pair of mandibles and 
 two pairs of maxilla;. A single 
 genital opening, on the preanal 
 segment. Example, Scolopcndva 
 
 (I^^ig- 5)- 
 
 Insecta (Hexapoda) . — Pri- 
 marily terrestrial. Three distinct 
 regions — head, thorax and abdo- 
 men. Head with a pair of com- 
 pound eyes in most adults, one 
 pair of antennas and three pairs 
 of mouth parts — mandibles, max- 
 illae and labium — besides which 
 a hypopharynx, or tongue, is 
 present. Thorax with a pair of 
 legs on each of its three segments 
 and usually a pair of wings on 
 each of the posterior two seg- 
 ments ; though there may be only 
 one pair of wings (as in Diptera 
 and male Coccid<T) ; the pro- 
 thorax never bears wings. Ab- 
 domen typically with ten seg- 
 ments (seldom more) and without legs, excepting in some 
 larv.T (as those of Lepidoptera, Tenthredinida? and Panor- 
 
 A centipede, Scolopcndra h 
 About two thirds the maxi 
 length. 
 
CLASSIFICATION 5 
 
 pid;r)- Stigmata paired and segnientally arranged. A meta- 
 morphosis (direct or indirect) occurs except in Thysannra and 
 Collembola. 
 
 Relationships. — The interrelationships of the classes of 
 Arthropoda form an obscure and highly debatable subject. 
 
 Crustacea and Insecta agree in so many morphological 
 details that their resemblances can no longer ]je dismissed as 
 results of a vague " parallelism," or " convergence ' ' of devel- 
 opment, but are inexplicable except in terms of community of 
 origin, as Carpenter has lately insisted. 
 
 Arachnida are extremely unlike other arthropods but find 
 their nearest allies among Crustacea, particularly the fossil 
 forms known as trilobites. 
 
 Malacopoda, as represented by Pcripatus, are often spoken 
 of as bridging the gulf that separates Insecta, Chilopoda and 
 Diplopoda from Annelida. Peripatus indeed resembles the 
 chsetopod annelids in its segmentally arranged nephridia, 
 dermo-muscular tube, coxal glands and soft integument, and 
 resembles the three other classes in its tracheae, dorsal vessel, 
 lacunar circulation, mouth parts and salivary glands. These 
 resemblances, however, are by no means close, and Pcripatus 
 does not form a direct link between the other tracheate arthro- 
 pods and the annelid stock, but is best regarded as an offshoot 
 from the base of the arthropodan stem. 
 
 In speaking o'f annelid ancestors, none of the recent annelids 
 are meant, of course, but reference is made to the primordial 
 stock from which recent annelids themselves have been de- 
 rived. 
 
 Though Diplopoda and Chilopoda have long been grouped 
 together under the name Myriopoda, they really have so little 
 in common, beyond the numerous limb-bearing segments and 
 the characters that are possessed by all tracheate arthropods, 
 that their differences entitle them to rank as separate classes. 
 Chilopoda as a whole are more nearly related to Insecta than 
 are Diplopoda, as regards segmentation, mouth parts, tracheae, 
 genital openings and other characters. 
 
ENTOMOLOGY 
 
 ScolopcndrcUa, now placed either among Diplopoda or else 
 in a class by itself, Symphyla, presents a remarkable combina- 
 
 FiG. 6. 
 
 Section of Scolopendrella immacitlata. b, brain; c, coxal gland; /, fore intestine; 
 li, hind intestine; in, mid intestine; n, nerve chain; o, opening of silk gland; od, 
 oviduct; oi', ovary; s, silk gland; u, urinary tube. — After Packard. 
 
 tion of diplopodan and insectean characters. Scolopendrella 
 (Fig. 6) and the thysamiran Cam pod ca have the same kind 
 of head, with its long moniliform antennae, and agree in the 
 general structure of the mouth parts ; 
 the number of body segments is nearly 
 the same, the legs and claws are essen- 
 tially alike, and cerci and paired abdom- 
 inal stylets are present in the two genera, 
 not to mention the correspondences of 
 internal organization. Indeed, it is 
 highly probable, as Packard maintained, 
 that the most primitive insects, Thys- 
 anura (and consecjuently all other in- 
 sects), originated from a form much like 
 Scolopendrella. A singular thysanuran. 
 Ana ja pyx vcsiculosus (Fig. 7), has 
 lately been discovered by Silvestri, who 
 regards it as being in many respects the 
 most primitive insect known, combining 
 as it does characters of Symphyla, Diplo- 
 poda and Canipodea. 
 The following diagram (Fig. 8) expresses very crudely one 
 view as to the annelid origin of the chief classes of Arthro- 
 poda. 
 
 Anajapyx vesiculosus. 
 Length, 2 mm. — After 
 Silvestri. 
 
CLASSIFICATION 
 
 The naturalness of the phyhim Arthropoda has been ques- 
 tioned by Kingsley and Packard. The latter author recently 
 divided Arthropoda into five independent phyla, holding that 
 
 Fig. 8. 
 
 INSECTA 
 
 CRUSTACEA 
 
 ARACHNIDA 
 
 CHILOPODA 
 DIPLGPGDA 
 
 MALACOPODA 
 ANNELIDA 
 
 Diagram to indicate the origin of Arthropoda. 
 
 " there was no common ancestor of the Arthropoda as a 
 whole, and that the group is a polyphyletic one." This icono- 
 clastic view, however, by emphasizing unduly the structural 
 differences among arthropods, tends to conceal the many deep- 
 seated resemblances that exist between the classes of Arthro- 
 poda. 
 
 Carpenter, in a most sagacious summary of the whole sub- 
 ject of arthropod relationships, has recently brought together 
 no little evidence in favor of a revised form of the old Miil- 
 lerian theory of crustacean origins. He traces all the classes 
 of Arthropoda back to common arthropodan ancestors with a' 
 definite number of segments and distinctly crustacean in 
 character; then traces these primitive arthropods back to 
 forms like the nauplius larva of Crustacea, and these in turn 
 
8 
 
 ENTOMOLOGY 
 
 to a hypothetical form Hke the trochosphere larva of recent 
 polychsete annelids. 
 
 Orders of Insects. — Linnaeus arranged insects in seven 
 orders, namely, Coleoptera, Hemiptera, Lepidoptera, Neurop- 
 
 FiG. 9. Fig. 10. 
 
 Campodea. Length, 
 3 mm. 
 
 Lepisma. Length, 
 10 mm. 
 
 tera, Hymenoptera, Diptera and Aptera. The wingless in- 
 sects termed Aptera were soon found to belong to diverse 
 orders and the name has now become so ambiguous as to meet 
 with little approbation. 
 
 From the Linnjean group Hemiptera, the Orthoptera were 
 set apart ; the old order Neuroptera, a heterogeneous and 
 unnatural group, has been split into several distinct orders, 
 and many other changes in the classification have been neces- 
 sary. 
 
 Without entering any further into the history of the sub- 
 ject, it is sufficient to say that increasing discrimination on the 
 
CLASSIFICATION 
 
 part of entomologists has been followed by a gradual increase 
 in the number of orders, until our present system has been 
 attained. 
 
 Owing to the incomplete condition ^''''- ^^• 
 
 of entomological knowledge, however, 
 the best system as yet proposed is but 
 tentative and more or less open to 
 objection. The most competent and 
 widely approved classifications are 
 those of Brauer and Packard, and 
 the system here adopted is essential!}- 
 that of Brauer, with certain important 
 modifications made by Packard. 
 
 In the course of the following syn- 
 opsis of the orders of insects it is 
 necessary to use some terms, as nicfa- 
 morphosis and thysannrifonii, in an- 
 ticipation of their subsequent defini- 
 tion. 
 
 I. Thysanura. — No metamorphosis. 
 Mouth parts mandibulate, either free 
 (ectognathous) or enclosed in the 
 head (entognathous). Wings inva- 
 riably absent. Thoracic segments simple and similar. Ab- 
 dominal segments ten, 
 with two to eight pairs 
 of rudimentary limbs 
 and two or three anal 
 cerci. Eyes aggregate, 
 compound or absent. 
 Antennae multiarticulate. 
 Integument thin. Ex- 
 amples, Cam pod ca (Fig. 
 9), Japyx, Machilis, 
 Some one hundred and seventy-five spe- 
 
 The snow flea, Acho- 
 lics nivicola. Length, 
 mm. 
 
 Fig 
 
 IS liorteiisis. Lengt 
 
 Lepisina (Fig. 10), 
 cies are known. 
 
lO 
 
 ENTOMOLOGY 
 
 2. Collembola. — Xo metamorphosis. Mouth parts entog- 
 nathous and typically mandibulate, with occasional secondary 
 suctorial modifications. Wings invariably absent. Thoracic 
 segments simple and similar or prothorax reduced. Body 
 cylindrical or globular; abdomen with six segments. Ventral 
 tube and furcula usually present, rarely rudimentary. Eyes 
 ocelliform or absent. Antennae of four segments in most 
 genera ; five or six in a few genera. Integument delicate. 
 Examples. Achorutes (Fig. ii). Sniinthurus (Fig, 12). 
 About seven hundred species have been described. 
 
 Fig. 
 
 Fig. 
 
 Hemimcrus falpoidcs. 
 Length, 11.5 mm. — After 
 Hansen. 
 
 Schistocerca americana. Slightly reduced. 
 
 Under the term Aptcrygota ( Apterygogenea, Brauer ; 
 Synaptera, Packard ) the Thysanura and Collembola, as primi- 
 tively wingless insects, are conveniently distinguished from all 
 other insects, or Pterygofa ( Pterygogenea, Brauer). 
 
 3. Orthoptera. — ^Metamorphosis direct. Mouth parts man- 
 dibulate. Wings two pairs as a rule, though not infrequently 
 reduced or absent; front wings coriaceous (tegmina) ; hind 
 
CLASSIFICATION I I 
 
 pair membranous, ample, closely reticulate, plicate along the 
 numerous radiating principal veins. Abdomen with ten or 
 eleven segments. Eight families : Forficulidas, Hemimeridse 
 (Fig. 13), Blattida?, MantidcC, Phasmidae (Fig. 240), Acri- 
 diidje (Fig. 14), Locustid;e, Gryllicke. Over ten thousand 
 species are known. 
 
 Some authors prefer to separate ForficulidcX from Orthop- 
 tera as a distinct order, for which Brauer and Packard pre- 
 serve the old term Dcrmaptera of Leach, while Comstock uses 
 Westwood's term Euplcxoptcra. 
 
 Hemimerida? consist at present of two African species 
 whose affinities appear to lie with Forficulida.% but deserve 
 further study. 
 
 4. Platyptera. — Aletamorphosis direct. Mouth parts man- 
 dibulate. Wings, if present, two pairs, delicate, membranous, 
 equal or hind pair smaller, and with the principal veins few 
 and simple. Integument usually thin. Nymphs thysanuri- 
 form. Two suborders. 
 
 Suborder Corrodentia. — Including three families, as fol- 
 lows : 
 
 Tcnnitidcc. — Eyes facetted. Antennje 9-31 jointed. 
 Mouth parts prognathous or hypognathous.^ Prothorax 
 large. Wings elongate, alike, membranous, delicate, with 
 indefinite reticulation and with a characteristic basal suture. 
 Abdomen elongate, with ten segments and a pair of short, 
 two-jointed anal cerci. Integument delicate. Social in habit. 
 Example, Tcniics (Fig. 273). Over one hundred species are 
 known. 
 
 Comstock places Termitid:e in an order by themselves, 
 Isoptera. 
 
 Emhiidcc. — Eyes facetted. Antennae 15-32 jointed. 
 Mouth parts prognathous. Thorax elongate, prothorax re- 
 duced. Wings (sometimes absent) elongate, membranous, 
 delicate, with few and feebly developed longitudinal and cross 
 veins. Abdomen elongate, with ten or possibly eleven seg- 
 
 ^ Progiiatlioiis, directed forward; liypognathoiis, directed downward. 
 
ENTOMOLOGY 
 
 OHgotoma michacU. Length, 10.5 mm. 
 McLachlan. 
 
 ments, and a pair of stout biarticulate cerci. Integument deli- 
 cate. Not social in habit. Examples, Emhia, OHgotoma 
 (Fig-. 15). Some twenty species, all from warm climates. 
 
 These insects are most 
 nearly related to Termit- 
 dse and Psocidje. 
 
 Psocidcu. — Eyes facet- 
 ted. Antenn?e 13-50 
 jointed. Mouth parts 
 hypognathous. Protho- 
 rax reduced. Wings 
 present, rudimentary or 
 absent ; front pair the 
 larger; veins few and ir- 
 regular. Abdomen with 
 nine or ten segments and 
 no cerci. Integument delicate. Example, Psociis (Fig. 16). 
 About two hundred species. 
 
 Comstock raises Psocidse to the rank of an order, for which 
 he employs, in a new sense, Brauer's term Corrodentia. 
 
 Suborder Mallophaga. — Wingless flattened insects, of para- 
 sitic habit. Head large. Eyes consisting of a few isolated 
 ocelli or else absent. An- 
 tennae 3-5 jointed. Mouth 
 parts prognathous. Pro- 
 thorax distinct ; mesotho- 
 rax often and metathorax 
 usually transferred to the 
 abdominal region. Ab- 
 dominal segments eight to 
 ten in number; no cerci. Parasitic upon birds and a few mam- 
 mals. Example, Menopon (Fig. 17). More than fifteen 
 hundred species have been described. 
 
 Packard's order Platyptcra originally included Perlid^e. 
 Brauer's order Corrodentia consisted of Termitidse, Psocidse 
 and Mallophaga; Perlidse being set apart as an order {Plecop- 
 
 PsocHS zTHOSus. Length, 5 
 
CLASSIFICATION 
 
 13 
 
 Fig. 
 
 tcra) and Enibiid?e being transferred doubtfully to Orthop- 
 tera. 
 
 Enderlein's recent and tborough studies confirm the view 
 that Termitida% Embiidaj, Psocidie and Mallophaga constitute 
 a single order. 
 
 5. Plecoptera. — ^ Metamorphosis direct. Antennas long, 
 multiarticulate. Mouth parts mandibulate. Prothorax large. 
 Wings two pairs, membranous, coarsely and complexly reticu- 
 late; ec|ual or else hind wings larger 
 and with an ample plicate anal area. 
 Abdomen with ten segments and usu- 
 ally a pair of long multiarticulate cerci. 
 Nymphs thysanuriform, aquatic; adults 
 unicjue in having tracheal gills. Ex- 
 ample, Ptcromircys (Fig. 18). A 
 single family, Perlida;, comprising two 
 hundred si)ecies. 
 
 6. Ephemerida. — Metamorphosis 
 direct. Antennae bristle-like. Mouth 
 parts mandibulate, but atrophied in 
 the adult. Prothorax small. Wings 
 membranous, minutely reticulate; hind 
 pair much the smaller, rarely absent. 
 Abdomen slender, with ten segments 
 ^nd three or two \'ery long multi- 
 articulate cerci. Integument delicate. Nymphs thysanuri- 
 form, aquatic. Example, Hcxagcnia (Fig. 19). Three hun- 
 dred species. 
 
 7. Odonata. — Metamorphosis direct. Antennae inconspicu- 
 ous, bristle-shaped. Mouth parts mandibulate. Prothorax 
 small. Wings four, elongate, subequal, similar, membranous, 
 minutely reticulate, with a costal joint, or nodus. Abdomen 
 slender, with ten segments. Nymphs thysanuriform, aquatic. 
 Example, Lihcllula (Fig. 20). About two thousand species 
 have been described. 
 
 8. Thysanoptera (Physopoda). — Metamorphosis direct. 
 
 A chicken louse, Menopc 
 Length, 2 mm. 
 
14 
 
 ENTOMOLOGY 
 Fig. i8. 
 
 Fig. ly. 
 
 Hexagenia variabilis. A, nymph; B, imago. Natural 
 
CLASSIFICATION 
 
 15 
 
 but including a subpupa stage. Mouth parts suctorial. Pro- 
 thorax long. Tarsus terminating in a bladder-like organ. 
 
 Fig. 20. 
 
 Libcllula pulchcUa. A, last nymphal skin; B, imago. Slightly reduced. 
 
 Wings present, rudimentary or absent, the two pairs narrow, 
 equal, similar, with few or no veins and fringed with long 
 hairs. Abdomen with ten segments. Minute insects. Ex- 
 
 Fig. 21 
 
 ample, Eutlirips (Fig. 21). About one hundred and fifty 
 species have been described. 
 
i6 
 
 ENTOMOLOGY 
 
 9. Hemiptera. — Metamorphosis direct (excepting male 
 Coccidse). Antennas usually few-jointed. :Mouth parts suc- 
 torial. Prothorax usually large. Wings usually present, 
 except in the parasitic forms. Eighteen thousand species. 
 Three suborders : 
 
 Suborder Heteroptera.— Wrings four, folded flat; front 
 membranous apically (hemelytra), 
 
 Fig. 22. 
 
 Benaciis griseus. Slightly reduced. 
 
 overlapping obliquely; hind wings membranous. Head not 
 deflexed. Example, Bcnacus (Fig. 22). About twelve thou- 
 sand species. 
 
 Suborder Homoptera.— Wings four, sloping roof-like, sim- 
 ilar and meml^ranous or front pair somewhat coriaceous 
 throughout. Head deflexed. Example, Cicada (Fig. 206). 
 Six thousand species. 
 
 Suborder Parasita. — Wingless. Eyes simple or none. 
 Thoracic segments intimately united; tarsus with a single 
 claw. Integument thin. Parasites upon mammals. Exam- 
 ple, Pediculus (Fig. 23). Some fifty species are known. 
 
 10. Neuroptera. — Aletamorphosis indirect. Antenna^ con- 
 
CLASSIFICATION 
 
 z;^. 
 
 spicuous. Mouth parts mandibulate. Fig. 23. 
 
 Prothorax large. Wings almost always 
 
 foijr, membranous, subequal or else hind 
 
 pair smaller, complexly reticulate, not 
 
 plicate. Larvae thy sanuri form or in 
 
 some cases cruciform, and aquatic or 
 
 terrestrial. Example, Chrysopa (Fig. 
 
 24). About six hundred species have 
 
 been named. 
 
 II. Mecoptera. — jNletamorphosis indi- 
 rect. ]\Iouth parts mandibulate, at the 
 
 end of a deflexed rostrum, or beak. 
 
 Prothorax small. Wings four, elongate, 
 
 membranous, naked, coarsely reticulate, 
 
 or else rudimentary or absent. Larvre 
 
 eruciform, caterpillar-like, with numerous prolegs, carnivo- 
 rous. Example, Bitfacus (Fig. 25). A 
 single family, Panorpid?e, comprising but 
 few known species. 
 
 12, Trichoptera. — Metamorphosis in- 
 direct. Antennae filiform. Mouth parts 
 of imago rudimentary or imperfectly 
 suctorial ; mandibles rudimentary or 
 absent. Prothorax small. Wings four, 
 
 membranous, hairy, veins moderate in number, cross veins 
 
 Head louse, Pediculus 
 capitis, female. Length, 
 2 mm. 
 
 Fig. 
 
 Chrysopa plorabiinda. 
 Slightly reduced. 
 
 few; hind pair almost always 
 the larger, with plicate anal 
 area. Larv?e suberuciform, 
 aquatic, usually case-forming. 
 Example, Molanna (Fig. 26). 
 Betw'een five and six hundred 
 species are known. 
 
 13. Lepidoptera. — Metamor- 
 phosis indirect. Mouth parts 
 suctorial, mandibles absent or 
 rudimentary (except in a few 
 3 
 
 Fig. 25. 
 
 hftaciis strigosu. 
 
 Natural size. 
 
i8 
 
 ENTOMOLOGY 
 
 generalized species). Prothorax small. Wings four, sim- 
 ilar, membranous, clothed with scales, veins moderate in num- 
 ber, cross veins few. Larvae cruciform (caterpillars), phy- 
 tophagous (almost never carnivorous), mandibulate. Some 
 fifty thousand species have been described. Two suborders, 
 not sharply separated from each other. 
 
 Suborder Heterocera. — Antenna? of various forms, but not 
 terminating in a distinct knob or club. Frenulum usually 
 
 Fig. 26. 
 
 Molanna cinerea. 
 
 diameters. — After Felt. 
 
 present. Chiefly nocturnal in habit. Example, Callosamia 
 (Fig. 236). 
 
 Suborder Rhopalocera. — Antennae simple, terminatmg m a 
 distinct club and without conspicuous lateral processes. Fren- 
 ulum absent. Diurnal normally. Examples, Papilio (Fig. 
 27), Anosia (Fig. 243, A). 
 
 14. Coleoptera. — Metamorphosis indirect. Mouth parts 
 mandibulate. Prothorax large, as a rule. Wings four ; front 
 pair horny (elytra), meeting in a straight line; hind pair mem- 
 branous, often folded. Larvae thysanuriform or eruciform. 
 Example, Hydrophilus (Fig. 28). About fifteen thousand 
 species. 
 
CLASSIFICATION 
 
 19 
 
 15, Diptera. — Metamorphosis indirect. Mouth parts typ- 
 ically suctorial, but modified for piercing, lapping-, rasping-, etc. 
 Prothorax small. One pair of wings (mcsollioracic), mem- 
 branous. transi)arcnt. with few \eins ; wings rudimentary or 
 absent, however, in most of the parasitic species; hind wings 
 represented by a pair of knobbed threads, or balancers. Lar- 
 vae cruciform, with the head frequently reduced to a mere 
 vestige with or without a pair of mandibles, and usually with- 
 
 FiG. 27. 
 
 B 
 
 Papilio troilus. A, larva; 
 
 larva suspended for pupation; C, chrysalis. 
 Natural size. 
 
 out true legs, though pseudopods may be present. Example, 
 Tipiila (Fig. 29). About forty thousand described species. 
 
 16. Siphonaptera ( Aphaniptera) . — Metamorphosis indi- 
 rect. Head small. Eyes simple or absent. Mouth parts 
 suctorial. Body laterally compressed. Thoracic segments 
 subequal. Wings absent or at most quite rudimentary. Lar- 
 vae with a head, mandibulate, apodous. Parasitic insects. 
 Example, Ctcnoccphalns (Fig. 30). One hundred and fifty 
 species. 
 
 17. Hymenoptera. — Metamorphosis indirect. Mouth parts 
 at the same time mandibulate and suctorial. Prothorax usu- 
 ally small. Wings four, similar, membranous, transparent, 
 
ENTOMOLOGY 
 
 with a few irregular veins and cells ; hind pair the smaller. 
 Females with an ovipositor, modified for sawing, boring or 
 
 Fig. 2^ 
 
 Hydro[>hilus triangularis. Natural size. 
 
 Stinging. Larvae eruciform, mandibulate, caterpillar-like, 
 with head and legs, or else maggot-like and apodous. Twenty- 
 five or thirty thousand species. Two suborders. 
 
 Fig. 29. 
 
 Tipula. A, larva; B, cast pupal skin; C, imago. Slightly reduced. 
 
 Suborder Terebrantia (Phytophaga, Sessiliventres) . — 
 
 Abdomen broadly attached to the thorax. Ovipositor modified 
 
CLASSIFICATION 
 
 for boring-, sawing or cutting. Larvns with complex mouth 
 parts and frequently abdominal legs. Phytophag-ous. Ex- 
 ample, Trcnic.v (h'ig. 31 ). 
 
 Fig. 31.. 
 
 Cat and dog flea, Ctciwccplialns canis. A, larva (after Klinckel d'Herculais) ; 
 B, adult. Length of adult, 2 nmi. 
 
 Suborder Aculeata (Heterophaga, Petiolata). — Abdomen 
 petiolate or subpetiolate ; first abdominal segment transferred 
 to the thorax. Ovipositor 
 often modified to form a 
 sting. Larvae apodous. Ex- 
 ample. Apis (Eig. 277). 
 
 Interrelations of the 
 Orders. — The modern clas- 
 sification aims to express 
 relationships, and these are 
 most clearly to be ascer- 
 tained by a comparative 
 study of the facts of anat- 
 omy and development. 
 
 The most generalized, or 
 primitive, insects are the 
 Thysanura. Sul)tracting 
 
 their special, or adaptive, peculiarities, their remaining charac- 
 ters may properly be regarded as inheritances from some 
 vanished ancestral type of arthropod. This primordial type, 
 
 Tremcx columha. A, imago; B, larva 
 (with parasitic larva of Tlialessa attached). 
 Natural size. — After Rilev. 
 
2 2 ENTOMOLOGY 
 
 then, probalily liad three simple and equal thoracic segments 
 differing but slightly from the ten abdominal segments ; three 
 pairs of legs and no wings; three pairs of exposed biting 
 mouth parts; a pair of long man3'-jointed antennae and a pair 
 of cerci of the same description ; a thin naked integument ; a 
 simple straight alimentary canal distinctly divided into three 
 primary regions ; a ganglion and a pair of spiracles for each 
 of the three thoracic and the first eight abdominal segments, 
 if not all the latter; no metamorphosis; functional abdominal 
 legs and active terrestrial habits. 
 
 The existing form that best meets these requirements is 
 Scolopendrella, which is not an insect, however, but belongs 
 among or near the diplopods. The most primitive of known 
 insects are Anajapyx and Cauipodca, through which other 
 insects trace their origin to the stock from which Symphyla 
 and Diplopoda arose. 
 
 Collembola, though specialized in several important ways, 
 all have the same peculiar kind of entognathous mouth parts 
 as Campodea and Japyx, for which reason and many others it 
 is believed that Collembola are an offshoot from the thysanu- 
 ran stem. Collembola, however, are not nearly so primitive 
 as Thysanura, for the former have fewer abdominal segments 
 than the latter, exhibit much greater concentration of the ner- 
 vous system, and are uniquely specialized in several respects, 
 notably as regards the ventral tube and the furcula, or spring- 
 ing organ. 
 
 Returning to Thysanura — the genera Machilis and Lcpisma 
 show decided orthopteran affinities ; thus their eyes are com- 
 pound and their mouth parts strongly orthopteran ; indeed, the 
 likeness of Lepisma to a young cockroach is striking, as is also 
 that of Japyx to a young forficulid. 
 
 In short, as Hyatt and Arms express it, " The generalized 
 form of Thysanura, and the manner in which it reappears in 
 the larvae of other insects, is the natural key of the classifi- 
 cation." 
 
 Orthoptera probably arose directly from the original thys- 
 anuriform stem. 
 
CLASSIFICATION 23 
 
 Platyptera, as a whole, are most nearly related to Orthop- 
 tera on the one hand and to Plecoptera on the other. Termit- 
 idse have strong orthopteran affinities and Embiidse have even 
 been placed in the order Orthoptera, though the latter family 
 is most nearly allied to Termitid.'c and Psocid?e. These two 
 are approached rather closely by Mallophaga and exhibit, by 
 the way, some collembolan characters, as Enderlein has lately 
 pointed out. 
 
 Plecoptera, which Packard placed in his group Platyptera, 
 are better regarded as a distinct order with some orthopteran 
 and many ephemerid and odonate affinities. The strong re- 
 semblance between nymphs of Plecoptera, Ephemerida and 
 Odonata indicates community of origin. 
 
 Ephemerida and Odonata are well circumscribed orders, 
 most nearly related to each other, but sharply separated, nev- 
 ertheless, by differences in the wings, mouth parts and other 
 organs. Ephemerida are almost unique among insects in hav- 
 ing a pair of genital openings — a primitive condition. 
 
 Thysanoptera form a distinct order, which is usually placed 
 next to Hemiptera, chiefly on account of the suctorial mouth 
 parts, though even in this respect there is no close agreement 
 between the two orders. 
 
 Hemiptera stand alone and give few hints of their ancestry. 
 They are least unlike Orthoptera and possibly originated with 
 Thysanoptera from some mandibulate and winged form. The 
 conversion of mandibulate into suctorial organs may be seen 
 within the order Collembola, but it is highly improbable that 
 Hemiptera arose from forms like Collembola. Hemiptera are 
 exceptional among insects with a direct metamorphosis in 
 their highly developed type of suctorial mouth parts. 
 
 Metamorphosis offers, upon the whole, the broadest criteria 
 for the separation of insects into primary groups. All the 
 orders considered thus far are characterized either by no meta- 
 morphosis or by a slight, or so-called " direct," or " incom- 
 plete," transformation. The following orders, on the con- 
 trary, are distinguished by an " indirect," or " complete," 
 
24 ENTOMOLOGY 
 
 metamorphosis, which appears in Neuroptera and attains its 
 maximum development in Diptera and Hymenoptera. 
 
 With Neuroptera the eruciform type of larva appears, as a 
 derivative of the earlier thysanuriform type. The larva of 
 Mantispo, as Packard has shown, actually passes, during its 
 individual development, from the primary, thysanuriform 
 stage to the secondary, eruciform condition. 
 
 Mecoptera form an isolated order, though their caterpillar- 
 like larvae, with eleven or twelve pairs of legs, suggest affini- 
 ties with Lepidoptera and, more remotely, with the tenthred- 
 inid Hymenoptera. 
 
 Trichoptera, while much like Mecoptera in structure and 
 metamorphosis, are undoubtedly closely related to Lepidop- 
 tera; in view of the extensive and deep-seated resemblances 
 between caddis flies and the most generalized moths (Microp- 
 terygidae) there is little doubt that Trichoptera and Lepi- 
 doptera originated from the same stock. 
 
 The origin of the coherent group Coleoptera is by no means 
 clear, although thysanuriform larvae occur frequently in this 
 order. Packard suggests that both beetles and earwigs arose 
 from some thysanuroid form or that the primitive coleopterous 
 larva sprang from some metabolous neuropteroid form. In 
 any linear arrangement of the orders the position of Coleop- 
 tera is largely arbitrary, and here the order is intruded between 
 Lepidoptera and Diptera simply for want of a more satisfac- 
 tory place. 
 
 Lepidoptera, Trichoptera and Mecoptera are probably 
 branches from one stem. Lepidoptera, Diptera and Hymen- 
 optera are reg'arded by Packard as having had a common 
 origin from metabolic Neuroptera. 
 
 Among Diptera, such larvae as those of Culicidae are com- 
 paratively primitive, according to Packard, and larvae of Mus- 
 cidae are secondary, or adaptive, forms. 
 
 Siphonaptera used to be regarded as Diptera and are prob- 
 ably an offshoot from the dipteran stem. 
 
 The most primitive hymenopterous larvae are those of the 
 
CLASSIFICATION 
 
 25 
 
 sawflies (Tentliredinidie), judging- from their resemblance to 
 mecopterons and lepidopterous larva?; and the simple, maggot- 
 like form of the larvae of ants, bees, wasps and parasitic 
 Hymenoptera is due to secondary modifications in correlation 
 with their sedentary mode of life. 
 
 In Diptera and Hymenoptera the phenomenon of metamor- 
 phosis attains its greatest complexity, as was remarked. 
 Opinions differ as to which of these two orders is the more 
 specialized. Hymenoptera are commonly called the " high- 
 est " insects, when their remarkable psychological development 
 is taken into account ; but from a purely structural standpoint 
 it is hard to say which order is the more complex — indeed, the 
 two orders are specialized in so many different ways that no 
 precise comparison can be made between them. 
 
 The following diagram (Fig. 32) is a graphic summary of 
 what has just been said in regard to the genealogy of the 
 
 Fig. 2,2. 
 
 DIPTERA 
 
 PLECOPTERA 
 PLATYPTERA 
 
 ORTHOPTERA 
 
 HEMIPTERA 
 
 COLEOPTERA 
 
 THYSANURA 
 
 Genealogical diagram of the orders of insects. 
 
 orders of insects. The positions of Hemiptera and Coleoptera 
 are most open to criticism. The central group (7") is the 
 
26 ENTOMOLOGY 
 
 hypothetical thysanuroid source of ah insects, including Thys- 
 anura themselves. Though Thysanura and Collembola show 
 no traces of wings, even in the embryo, it should be borne in 
 mind that all the other insects probably had winged ancestors 
 and that it is more reasonable to assume a single winged group 
 as a starting point than to suppose that wings originated inde- 
 pendently in several different groups of insects. 
 
CHAPTER II 
 ANATOMY AND PHYSIOLOGY 
 
 I. Skeleton 
 
 Number and Size of Insects. — The imnil^er of insect spe- 
 cies already known is about 300,000 and it is safe to estimate 
 the total number of existing species as at least one million. 
 
 Among the largest living species are the Venezuelan beetle 
 Dynastcs Jicrculcs, which is 155 mm. long, and the Venezuelan 
 grasshopper Acrid ium latrcillci, which has a length of 166 
 mm. and an alar expanse of 240 mm. Among Lepidoptera, 
 Attacus atlas of Indo-China spreads 240 mm.; Attacus ccesar 
 of the Philippines, 255 mm. ; and the Brazilian noctuid Erebus 
 agrippina, 280 mm. Some of the exotic wood-boring larvae 
 attain a length of 150 mm. 
 
 The giants among insects have been found in the Carbonif- 
 erous, from which Brong^niart described a phasmid (Titauo- 
 pliasina) as being one fourth of a meter long. 
 
 At the other extreme are beetles of the family Trichoptery- 
 gidse, some of which are only 0.25 mm. in length, as are also 
 certain hymenopterous egg-parasites of the families Chalcid- 
 ida2 and Proctotrypidje. 
 
 Thus, as regards size, insects occupy an intermediate place 
 among animals ; though some insects are smaller than the 
 largest protozoans and others are larger than the smallest 
 vertebrates. 
 
 Segmentation. — One of the fundamental characteristics of 
 arthropods is their linear segmentation. The subject of the 
 origin of this segmentation is far from simple, as it involves 
 some of the most difficult cjuestions of heredity and variation. 
 As arthropod segmentation is usually regarded as an inher- 
 itance from annelid-like ancestors, the subject resolves itself 
 
 27 
 
28 ENTOMOLOGY 
 
 into the question of the origin of the segmented from the nn- 
 segmented " worms." Cope, Packard and others give the me- 
 chanical explanation which is here summarized. In a thin- 
 skinned, unsegmented worm, the flexures of the body initiated 
 by the muscular system would throw the integument into 
 folds, much as in the leech, and with the thickening of the 
 integument, segmentation would appear from the fact that the 
 deposit of chitin would be least at the places of greatest flex- 
 ure, i. e., the valleys of the folds, and greatest at the places 
 of least flexure, i. e., the crests of the folds. This explana- 
 tion, which has been elaborated in some detail by the Neo- 
 Lamarckians, applies also to the segmentation of the limbs, as 
 well as the body. 
 
 Head. — In an insect several of the most anterior pairs of 
 primary appendages have been brought together to co-operate 
 as mouth parts and sense organs, and ^the segments to which 
 they belong have become compacted into a single mass — the 
 head — in which the original segmentation is difficult to trace. 
 The thickened cuticula of the head forms a skull, which 
 serves as a fulcrum for the mouth parts, furnishes a base of 
 attachment for muscles and protects the brain and other 
 organs. 
 
 While the jaws of most insects can only open and shut, 
 transversely, their range of action is enlarged by movements 
 of the entire head, which are permitted by the articulation 
 between the head and thorax. 
 
 As a rule, one segment overlaps the one next behind ; but 
 the head, thougii not a single segment of course, never over- 
 laps the prothorax in the typical manner, but is usually re- 
 ceived into that segment. This condition, which may possibly 
 have been brought about simply by the backward pull of the 
 muscles that move the head, has certain mechanical advantages 
 over the alternative condition, in securing, most economically,, 
 freedom of movement of the head and protection for the artic- 
 ulation itself. 
 
 The size and strength of the skull are usually proportionate 
 
ANATOMY AND PHYSIOLOGY 
 
 29 
 
 to the size and power of the moiitli parts. In some insects 
 ahnost the entire surface of the head is occupied by the eyes, 
 as in Odonata (Fig-. 20, B) and Diptera (Fio;. 39). In mus- 
 cid and many other chpterous larv.e, or " mag-o-ots." tlie head 
 is reckiced to the merest rn(hment. 
 
 Though commonly more or less globose or ovate, the head 
 presents innumerable forms ; it often bears unarticulated out- 
 growths of various kinds-, some of which are plainly adaptive, 
 while others are apparently purposeless and often fantastic. 
 
 Sclerites and Regions of the Skull. — The dorsal part of 
 the skull (Fig. 33) consists almost entirely of the cpicraiiiitiii, 
 
 Fig. 32. 
 
 mp 
 
 Skull of a grasshopper, Melanoplus diffcrcntialis. a, antenna; c, clypcus; e, com- 
 pound eye; /, front; g, gena; /, labrum; Ip, labial palpus; m, mandible; Dtp, maxillary 
 palpus; o, ocelli; oc, occiput; pg, post-gena; i', vertex. 
 
 which bears the compound eyes ; it is usually a single piece, 
 or sclcritc, though in some of the simpler insects it is divided 
 by a Y-shaped suture. The middle of the face, where the 
 median ocellus often occurs, is termed the front; ordinarily 
 this is simply a region, though a frontal sclerite exists in 
 some insects. Just above the front, and forming the sum- 
 
30 ENTOMOLOGY 
 
 mit of the head, is the region known as the vertex; it 
 often bears ocelh. The clypeus is easily recognized as being 
 the sclerite to which the upper Hp. or labium, is hinged, 
 though the clypeus is not invariably delimited as a distinct 
 sclerite. The cheeks of an insect are known as the gcncc, 
 and post-gcncu sometimes occur. On the under side of the 
 head is the gula, which bears the under lip, or labium. That 
 part of the skull nearest the prothorax is termed the occi- 
 put; usually it is not delimited from the epicranium, though 
 in some insects it is continuous with the post-gense to 
 form a distinct sclerite. The occiput surrounds the opening 
 known as the occipital foramen, through which the oesophagus 
 
 and other organs pass into 
 "^4- the thorax. The membrane 
 
 ^V ^^^<'''° °^ ^^^^ "^^^ ^" Orthoptera 
 
 .'■''--? W '^^^ m- X^ and some other insects con- 
 
 'I tains small cervical sclerites, 
 
 % dorsal, lateral or ventral in 
 
 |#f J- position; these, in the opin- 
 
 ^•* '-' ' ion of Comstock, pertain 
 
 to the last segment of the 
 head. Besides those de- 
 scribed, a few other cephalic 
 sclerites may occur, small 
 
 Skull of a grasshopper, Dissosteira caro- and iuCOnspicUOUS, but UCV- 
 lina. o. occipital foramen; t, t, anterior grthelCSS of Considerable 
 arms of tentorium. 
 
 morphological importance. 
 Tentorium. — In the head is a chitinous supporting struc- 
 ture known as the tentorium. This consists of a central plate 
 from which diverge two pairs of arms extending to the skull 
 (Fig. 34). The central plate lies between the brain and the 
 suboesophageal ganglion and under the oesophagus, which 
 passes between the anterior pair of arms. The tentorium 
 braces the skull, affords muscular attachments and holds the 
 cephalic ganglia and the oesophagus in place. It is not a true 
 internal skeleton, but arises from the same ectodermal laver 
 
 / 
 
ANATOMY AND PHYSIOLOGY 
 
 31 
 
 which produces the external cuticula; though authors are not 
 agreed as to the details of the development. 
 
 Eyes. — The eves are of two kinds — siiii/^lc and conipoiimL 
 The latter, or eves proper, conspicuous on each side of the 
 head, are of common occurrence 
 except in the larvae of most holo- 
 metaholous insects, in some gene- 
 ralized forms (as Collemhola) and 
 in parasitic insects. The compound 
 eyes (Fig. 40) are convex and often 
 hemispherical, though their outline 
 varies greatly ; thus it may be oval 
 (Orthoptera) or triangular (Noto- 
 necfa), while in the aquatic beetles 
 of the family Gyrinida; (Fig. 35) 
 each eye has a dorsal and a ventral 
 lobe, enabling the insect to see upward and downward at the 
 same time ; so also in Obcrca and other terrestrial beetles of the 
 same family. Superficially, a compound eye is divided into 
 
 Head of a gyrinid beetle, Dincu- 
 tus, to show divided eye. 
 
 Fig. 36. 
 
 Agglomerate eyes of a male 
 coccid, Leachia fuscipennis. — 
 After SiGNORET. 
 
 Fig. 37. 
 
 \^ ^J^^-J 
 
 c 
 
 ^ 
 
 'M**^ 
 
 Facets of a compound 
 eye of Melanoplns. 
 Highly magnified. 
 
 erate type of eye (Fig. 36) are commonly more or less hex- 
 agonal (Fig. 37), as the result of mutual pressure. These 
 facets are not necessarily equal in size, for in dragon flies the 
 dorsal facets are frequently larger than the ventral. In diam- 
 
32 
 
 ENTOMOLOGY 
 
 eter the facets range from .016 mm. {Lycccna) to .094 mm. 
 (Ceranibyx). Their number is often enormous; thus the 
 house fly (Mnsca doincstica) has 4,000 to each eye, a butter- 
 fly (Papilio) 17,000, a beetle {Mor- 
 
 FiG. 38. 
 
 dcUa) 25,000 and a sphingid moth 
 
 27,000 ; on the other hand, ants have 
 from 400 down, the worker ant of 
 Eciton having at most a single facet 
 on each side of the head. 
 
 Ocelli.- — The simple eyes, or ocelli, 
 appear as small polished lenses, either 
 lateral or dorsal in position. Lateral 
 ocelli (Fig. 38) occur in the larvze of 
 most holometabolous insects and in 
 parasitic forms. Dorsal ocelli, sup- 
 plementary to the compound eyes, 
 occur on or near the vertex, and are 
 more commonly three in number, ar- 
 ranged in a triangle, as in Odonata, Diptera (Fig. 39) and 
 Hymenoptera (Fig. 40) as well as many Orthoptera and He- 
 miptera. Few beetles have ocelli and almost no butterflies 
 
 Head of a 
 
 caterp 
 
 Samia cecrofia, 
 
 to E 
 
 lateral ocelli. 
 
 
 Fig. 39- 
 
 Ocelli and compound eyes of a fly, Phonnia rcgina. A, male; B, female. 
 
 (Lcreiiia accius with its one ocellus being the only exception 
 known), though not a few moths have two ocelli. 
 
 As explained beyond, the compound eyes are adapted to per- 
 ceive form and movements and the ocelli to form images of 
 
ANATOMY AND PHYSIOLOGY 
 
 33 
 
 objects at close range or simply to distinguish between light 
 and darkness. 
 
 Sexual Differences in Eyes. — In most Diptera (Fig. 39) 
 and in Ilymenoptera (Fig-. 40) and Ephemerida^ as well, the 
 eyes of the male are larger and closer together {lioloptic) than 
 
 1 10 [O 
 
 Ocelli and compound eyes of the honey bee, Apis mellifera. A, queen; B, drone. - 
 After Cheshire. 
 
 those of the female (dichoptic) . This difference is attributed 
 to the fact that the male is more active than the female, espe- 
 cially in the matter of seeking out the opposite sex. Among 
 ants of the same species the different forms may differ greatly 
 in the number of lateral facets. Thus in Formica pratensis, 
 according to Forel, the worker has about 600 facets in each 
 eye, the queen 800-900 and the male 1,200. 
 
 Blind Insects. — Many larva;, surrounded by an abundance 
 of food and living often in darkness, need no eyes and have 
 none; this is true of the dipterous " maggots " and many other 
 sedentary larvae, particularly such as are internal parasites 
 (Tachinidse, Ichneumonidae), or such as feed within the tis- 
 sues of plants (many Buprestidse, Cerambycidae and Curculi- 
 onid^e). Subterranean or cavernicolous insects are either eye- 
 less or else their eyes are more or less degenerate, according 
 to the amount of light to which they have access. The state- 
 ment is made that blind insects never have functional wings. 
 
 Antennae. — The antennae, never more than a single pair 
 (though embryonic " second antennae " occur in Thysanura 
 4 
 
34 
 
 ENTOMOLOGY 
 
 and Collembola), are situated near the compound eyes and 
 frequently between them. With rare exceptions the antennae 
 have always several and usually many segments. In form 
 these organs are exceedingly varied, though many of them 
 may be referred to the types represented in Figs. 41-43. 
 
 \^arious forms of antennae. A, filiform, Euschistus; B, setaceous, Plathemis; C, 
 moniliform, Catogenus; D, geniculate, Bombiis; f, flagellum; p, pedicel; s, scape; E, 
 irregular, Phormia; a, arista; F, setaceous, Galerita; G, clavate, Anosia; H, pectinate, 
 male Ptilodactyla; I, lamellate, Lachnosterna; J, capitate, Megalodacne ; K, irregular, 
 Dineutus. 
 
 Though homologous in all insects, the antennae are by no 
 means equivalent in function. They are commonly tactile 
 (grasshoppers, etc.) or olfactory (beetles, moths) and occa- 
 sionally auditory (mosquito), as described beyond, but may 
 
ANATOMY AND PHYSIOLOGY 
 
 35 
 
 he adapted for other than sensory functions. Thus the anten- 
 n;e of tlie aquatic heetle Hydrophiliis are used in connection 
 with respiration and those 
 
 to hold 
 
 Fig. 
 
 IK of a moth, 
 male; B, 
 
 Snmia cccropia. 
 female. 
 
 of the male Mcloc 
 the female. 
 
 Sexual Differences in An- 
 tennae. — In moths of the 
 family Saturniidas {S. cccro- 
 pia, C. promcthca, etc.) the 
 pectinate antennae of the male 
 are larg-er and more feathered 
 than those of the female, 
 and (liiYer also in having more 
 segments (Fig. 42). Here 
 the antennae are chieiiy olfac- 
 tory, and the reason for their 
 greater development in the 
 male appears from the fact 
 that the male seeks out the female l)y means of the sense of 
 smell and depends upon his antennas to perceive the odor ema- 
 nating from the opposite sex. 
 
 The plumose antennas of the male mosquito (Fig. 43) are 
 highly developed organs of hearing, and are used to locate the 
 female ; they have delicate fihrillae of various lengths, some of 
 which are thrown into sympathetic vibration by the note of 
 the female (p. 107). 
 
 Mcloc has just been mentioned. In Sinmthunis nialingrcnii 
 (Collembola) the antennae of the male are provided with 
 hooks and otherwise adapted to grasp those of the female at 
 copulation. 
 
 Though systematists have recorded many instances of an- 
 tennal antigeny, the interpretation of these sexual differences 
 has received very little attention ; though a beginning in the 
 subject has been made by Schenk, whose results will be re- 
 ferred to in connection with the sense organs. 
 
 Mouth Parts. — On account of their great range of diffe- 
 
36 
 
 ENTOMOLOGY 
 
 rentiation, the mouth parts are of fundamental importance to 
 the systematist, particularly for the separation of insects into 
 orders. Most of the orders fall into two groups according 
 as the mouth parts are either biting {luandihulatc) or sucking 
 
 Fig. 43- 
 
 Antennae of mosquito, Culcx pipiens. A, male; B, female. 
 
 (suctorial). Collembola and Hymenoptera, however, com- 
 bine both functions ; Diptera, though suctorial, exhibit various 
 modifications for piercing, lapping or rasping; Thysanoptera 
 are partly mandibulate but chiefly suctorial ; and adult Ephe- 
 merida and Trichoptera have but rudimentary mouth parts. 
 
 The mandibulate orders are Thysanura, Collembola (pri- 
 marily). Orthoptera, Platyptera, Plecoptera, Ephemerida 
 (rudimentarily in adult), Odonata, Neuroptera, Mecoptera 
 and Coleoptera. 
 
 The mouth parts of an insect consist typically of lahniin, 
 mandibles, niaxillcc, labium and hypo pharynx (Fig. 44), 
 though these organs differ greatly in different orders of in- 
 sects. The mandibulate, or primary type, from which the 
 suctorial, or secondary type, has been deri\-ed, will be consid- 
 ered first. 
 
 Mandibulate Type. — The iabruni, or upper lip, in biting 
 
ANATOMY AND PHYSIOLOGY 
 
 17 
 
 insects is a sini])lc plate, hing-ed to the clypens and moving up 
 and down, though capahle of protrusion and retraction to some 
 extent. It coxers tlie nianthljles in front .and pulls food back 
 to these organs. On the roof of the pharynx, under the la- 
 
 FiG. 44. 
 
 Mouth parts of a cockroach, Ischnoptera pennsylranica. A, labrum; B, mandible; 
 C, hypopharynx; D, maxilla; E, labium; c, cardo; g (of maxilla), galea; g (of labium), 
 glossa; /, lacinia; Ip, labial palpus; m, mentum; mp, maxillary palpus; p, paraglossa; 
 pf, palpifer; pg, palpiger; s, stipes; sm, submentum. B, D and E are in ventral 
 aspect. 
 
 l)rum and clypeus, is the cpipharyii.v ; this consists of teeth, 
 tubercles or bristles, which serve in some insects merely to 
 hold food, though as a rule the epipharynx in mandibulate 
 insects bears end-organs of taste (Packard). 
 
 The mandibles, or jaws proper, move in a transverse plane, 
 being closed by a pair of strong adductor muscles and opened 
 by a pair of weaker abductors. The mandible is almost 
 always a single solid piece. In herbivorous insects (Fig. 
 45, y^) it is compact, bluntly toothed, and often bears a molar, 
 or crushing, surface behind the incisive teeth. In carnivorous 
 
38 
 
 ENTOMOLOGY 
 
 Species (B) the mandible is usually long-, slender and sharply 
 toothed, without a molar surface. Often, as in soldier ants. 
 
 Various furiiis of mandibles. A, Melanoplus; B, Cicindcla; C, Apis; D, Ontliophagns; 
 E, Chrysopa; F-I, soldier termites (after Hagen). 
 
 the mandibles are used as piercing weapons; in bees (C) they 
 are used for various industrial purposes ; in some beetles they 
 are large, grotesque in form and appa- 
 rently purposeless. The mandibles of 
 Ontliophagns (D) and many other dung 
 beetles consist chiefly of a flexible lam- 
 ella, admirably adapted for its special 
 purpose. In Euphoria (Fig. 261 ), which 
 feeds on pollen and the juices of fruits, 
 the mandibles, and the other mouth 
 parts as well, are densely clothed with 
 hairs. In the larva of Chrysopa, the 
 inner face of the mandible (Fig. 45, £) 
 has a longitudinal groove against which 
 the maxilla fits to form a canal, through 
 which the blood of plant lice is sucked 
 into the oesophagus. In termites (F-I) 
 the mandibles assume curious and often 
 inexplicable forms. 
 
 Next in order are the inaxilkc, or 
 under jaws, which are less powerful 
 than the mandibles and more complex, consisting as they 
 do of several sclerites (Figs. 44, 46). Essentially, the 
 
 Maxilla of Harpalus 
 caliginosus, ventral as- 
 pect, c, cardo; g, galea; 
 I, lacinia; p, palpus; pf, 
 palpi fer; s, stipes; sg, 
 subgalea. 
 
ANATOMY AND PHYSIOLOGY 
 
 39 
 
 maxilla consists of three lobes, namely, palpus, galea and 
 lacinia, which are borne by a stipes, and hinged to the skull 
 by means of a cardo. The palpus, always lateral in position, 
 is usually four- or five-jointed and is tactile, olfactory or gus- 
 tatory in function. The lacinia is commonly provided with 
 teeth or spines. The maxillae supplement the mandibles by 
 holding the food when the latter open, and help to comminute 
 the food. Additional maxillary sclerites. of minor impor- 
 tance, often occur. 
 
 The labium, or under lip, may properly be likened to a united 
 pair of maxillae, for both are formed on the same three-lobed 
 plan. This correspondence is evident 
 in the cockroach, among other gener- 
 alized insects. Thus, in this insect 
 (Fig. 44) : 
 
 Fig. 47. 
 
 
 
 Labium = 
 
 Maxill.e 
 
 
 
 palpus = 
 
 palpus 
 
 
 
 paraglossa = 
 
 galea 
 
 
 
 ghssa = 
 
 lacinia 
 
 
 
 palpigcr = 
 
 palpi fa- 
 
 
 
 mcntinn =^ 
 
 sti pi tcs 
 
 'bnu 
 
 : lit Hill 
 
 with gula = 
 
 cai'dincs 
 
 In most mandibulate orders the 
 glossae unite to form a single median 
 organ, as in Harpalus (Fig. 47, g). 
 The labium forms the floor of the 
 pharynx and assists in carrying food 
 to the mandibles and maxillae. 
 
 The use of the term " second 
 maxillae " for the labium of an in- 
 sect is open to objection, as it implies an equivalence with 
 the second maxillae of Crustacea — which is by no means 
 established. 
 
 The tongue, or hypo pharynx, is a median fleshy organ (Fig. 
 44) which is usually united more or less with the base of the 
 labium. In insects in general, the salivary glands open at the 
 
 Labium of Harpalus caligi- 
 nosiis, ventral aspect. g, 
 united glossse, termed the 
 glossa; m, mentum; p, palpus; 
 pg, palpiger; pr, paraglossa; 
 sm, submentum. The median 
 portion of the labium beyond 
 the mentum is termed the 
 ligula^ 
 
40 
 
 ENTOMOLOGY 
 
 Fig. 48. 
 
 Hypopharynx of 
 niimerus talpoides. 
 lingua; s, superlingu 
 After Hansen. 
 
 base of the hypopharynx. In the most generaHzed insects, 
 Thysanura and Collembola, the hypopharynx is a compound 
 organ, consisting of a median ventral lobe, or lingua, and two 
 dorso-lateral lobes, termed superlingiicu 
 by the author. Superlinguje occur in a 
 few other mandibulate orders (Orthop- 
 tera, Fig. 48; Ephemerida, Fig. 49), but 
 have not yet been recognized in the more 
 specialized orders of insects. 
 
 Suctorial Types. — Owing to their 
 greater complexity, suctorial mouth parts 
 are not nearly so well understood as the 
 mandibulate organs, biit enough has been 
 learned to enable us to homologize the 
 two types, even though morphologists still disagree in regard 
 to minor details of interpretation. 
 
 The suctorial, or haustellate, orders are Collembola (in 
 part), Thysanoptera (in part), Hemiptera, Trichoptera (im- 
 perfectly) , Lepidoptera, Dip- 
 tera, Siphonaptera and Hy- 
 menoptera (which have 
 functional^ mandibles, how- 
 ever). 
 
 Hemiptera. — The beak, 
 or rosiniui, in Hemiptera 
 consists (Fig. 50) of a 
 conspicuous, one- to four- 
 jointed labium, which en- 
 sheathes hair-like mandibles and maxillse and is covered 
 above at its base by a short labrum. The mandibles and max- 
 illae are sharply-pointed, piercing organs and the former fre- 
 quently bear retrorse barbs just behind the tip; the two max- 
 illae lock together to form a sucking tube. Though primarily 
 a sheath, the labium bears at its extremity sensory hairs, which 
 are doubtless used to test the food. This general description 
 applies to all Hemiptera except the parasitic forms, which pre- 
 
 Hypopharynx of an 
 gcnia. I, lingua; si, 
 After Vayssiere. 
 
 and 
 
 ephemerid, Hepta- 
 sl, superlinguae. — ■ 
 
ANATOMY AND PHYSIOLOGY 
 
 41 
 
 sent special modifications. A pharyngeal pumping apparatus 
 is present, which is similar in its general plan to that of Lei)i- 
 doptera and Diptera, as presently described, though it differs 
 as regards the smaller details of construction. 
 Fig. 50. 
 
 Mouth parts of a liemipteron, Bcnaciis griseus. A, dorsal aspect; B, transverse sec- 
 tion; C, e.xtremity of mandible; D, transverse section of mandibles and maxillx; c, 
 canal; I, labrum; li, labium; m, mandible; m.v, maxillae. 
 
 Lepidoptera. — In Lepidoptera, excepting Erioccpliala. the 
 labrum is reduced (Fig. 51) and the mandibles are either rudi- 
 mentary or absent (Rhopalocera). The two maxillcC are rep- 
 resented by their gale?e, which form a conspicuous proboscis ; 
 the grooved inner faces of the galeae (or lacinicC, according to 
 Kellogg) form the sucking tube, which opens into the cesoph- 
 agus. The labium is reduced, though the labial palpi (Fig. 
 52) are well developed. The so-called rudimentary mandi- 
 
 to be lateral projections of the labrum (Fig. 51) and he terms 
 them pilifers. 
 
ENTOMOLOGY 
 
 The exceptional structure of the mouth parts in the gene- 
 rahzed genus Eriocephala {Micro pteryx) sheds much Hght on 
 
 the morphology of these 
 
 Fig. 51. 
 
 organs in other Lepidop- 
 tera. as Walter and Kel- 
 logg ha\-e shown. In 
 this genus there are func- 
 tional mandibles ; the 
 maxilla presents palpus, 
 galea, lacinia, stipes and 
 cardo, though there is no 
 pr( )b<3scis ; the labium has 
 well developed submen- 
 tum, mentum and palpi ; a 
 hypopharynx is present. 
 
 The sucking apparatus, 
 as described by Burgess, 
 Five muscles, originating 
 Fig. 52. 
 
 Head of a sphingid moth, Phlegethontiiis 
 sexta. a, antenna; c, clypeus; e, eye; /, labrum; 
 m. mandible; p, pilifer; pr, proboscis. 
 
 is essentially like that of Diptera. 
 at the skull and inserted on the 
 wall of a pharyngeal bulb, serve 
 to dilate the bulb that it may suck 
 in fluids, while numerous circular 
 muscles serve by contracting suc- 
 cessively to squeeze the contents 
 of the bulb back into the stomach ; 
 a hypopharyngeal valve prevent? 
 their return forward. 
 
 Diptera.- — In the female mos- 
 quito the mouth parts (Fig. 53) 
 are long and slender. As Dim- 
 mock has found, the labrum and 
 epipharynx combine^ to form a 
 
 maxillae are delicate, linear, pierc- 
 ing organs, the latter being barbed 
 distally; maxillary palpi are pres- 
 ^ Kulagin, however, describes them as remaining separate. 
 
 Head of a butterfly, J'anessa. 
 labial palpus; p, a, antennae; /, 
 proboscis. 
 
ANATOMY AND PHYSIOLOGY 
 
 43 
 
 ent; the hypopharynx is linear also and serves to conduct sa- 
 liva ; the labium forms a sheath, enclosing the other mouth 
 parts when they are not in use: a pair of sensory lobes, termed 
 labella, occur at the extremity o{ the labium. 
 
 Fig. 53. 
 
 I li h rj. 
 
 .n ^ mx 
 
 Mouth parts of female mosquito, Culcx pipicns. A, dorsal aspect; B, transverse 
 section; C, extremity of maxilla; D, extremity of labrum-epipharynx; a, antenna; e, 
 compound eye; h, hypopharynx; /, labrum-epipharynx; li, labium; m, mandible; mx, 
 maxilla; p, maxillary palpus. — B, after Dimmock. 
 
 The oesophagus is dilated to form a bull), or sucking organ, 
 from which muscles pass outward to the skull ; when these con- 
 tract, the bulb dilates and can suck in fluids, as blood or water, 
 which are forced back into the stomach by the elasticity of the 
 bulb itself, according to Dimmock ; the regurgitation of the 
 food is prevented by a valve. 
 
 The male mosquito rarely if ever sucks blood and its mouth 
 parts differ from those of the female in that the mandibles are 
 
44 
 
 ENTOMOLOGY 
 
 aborted and the maxilla; slightly developed, but with long 
 palpi, while the hypophar^-nx coalesces with the labium, and 
 there is no oesophageal bulb. 
 
 Hymenoptera. — In the honey bee, which will serve as a 
 type, the labrum (Fig. 54) is simple; the mandibles are well 
 developed instruments for cutting and other purposes and the 
 
 Fig. 54- 
 
 Mouth parts of the honey bee, Apis mclUfcra. a, base of antenna; br, brain; c, 
 clypeus; h, hypopharynx; /, labrum; Ip, labial palpus; m, mentum; mo, mouth; mx, 
 maxilla; sm, submentum. — After Cheshire. 
 
 remaining mouth parts form a highly complex suctorial appa- 
 ratus, as follows. The tongue is a long flexible organ, ter- 
 minating in a " spoon " (Fig. 127) and clothed with hairs of 
 various kinds, for gathering nectar or for sensory or mechan- 
 ical purposes. The maxillre and labial palpi form a tube em- 
 bracing the tongue, while the epipharynx fits into the space 
 between the bases of the maxillre to complete this tube. 
 Through this canal nectar is driven, by the expansion and con- 
 traction of the tube itself, according to Cheshire, except that 
 when only a small quantity of nectar is taken, this passes from 
 the spoon into a fine " central duct," or also into the '* side 
 ducts," which are specially fitted to convey quantities of fluid 
 too small for the main tube. For a detailed account of the 
 highly complex and exquisitely adapted mouth parts of the 
 honey bee, the reader is referred to Cheshire's admirable work 
 or to Packard's Text-Book. 
 
 Segmentation of the Head. — The determination of the 
 
ANATOMY AND PHYSIOLOGY 45 
 
 nuniljer of seo-ments entering" into the composition of the insect 
 head has heen a chfficiilt problem. As no sej^ment l)cars more 
 than one pair of primary aiiiiendao-es, tlierc are at least as 
 many seg-ments in the head as there are pairs of primary 
 appendages. On this basis, then, the antenn;e, mandibles, 
 maxillae and labinm may be taken to indicate so many seg- 
 ments; but in order to decide whether the e)es. labrnm and 
 hvpopharvnx represent segments, other than ]nn"ely anatom- 
 ical evidence is necessary. The key to the subject is furnished 
 by embryology. At an early stage of development the future 
 segments are marked off by transverse grooves on the ventral 
 surface of the embryo, and the pairs of segmental appendages 
 are all alike (Fig. 194), or equivalent, though later they dif- 
 ferentiate into antenn;c, mouth parts, legs, etc. Moreover, the 
 nervous system exhibits a segmentation which corresponds to 
 that of the entire insect; in other words, each pair of primitive 
 ganglia, constituting a neuromcrc, indicates a segment. Now 
 in front of the oesophagus three primitive segments appear, each 
 with its neuromere (Fig. 55) : first in position, an ocular seg- 
 ment, destined to bear the compound eyes; second, an antennal 
 segment; third, an intercalary (prciiiaiulibitlar) segment, 
 wdiich in the generalized orders Thysanura and Collembola 
 bears a transient pair of appendages that are probably homol- 
 ogous with the second antennae of Crustacea. In the adult, 
 the ganglia of these three segments have united to form the 
 brain, and the original simplicity and distinctness have been 
 lost. The labrum, by the way, does not represent a pair of 
 appendages, but arises as a single median lobe. Behind the 
 oesophagus, three embryonic segments are clearly distinguish- 
 able, each with its pair of appendages, namely, ;/;an(//6H/tfr, //m.i-- 
 illary and labial. Finally, the hypopharynx, or rather a part of 
 it, claims a place in the series of segmental appendages, as the 
 author has maintained ; for in Collembola its two dorsal con- 
 stituents, or supcrlingucr, develop essentially as do the other 
 paired appendages and, moreover, a superlingual neuromere 
 (Fig. 55) exists. The four primitive ganglia immediately 
 
46 
 
 ENTOMOLOGY 
 
 behind the mouth eventually combine to form the suboesopha 
 geal ganglion. 
 
 To summarize — the head of an insect is composed of at least 
 six segments, namely, ocular, antennal, intercalary, mandibu- 
 lar, maxillary and labial ; and at most seven, since a superlin- 
 gual segment occurs between the mandibular and maxillary 
 segments in Collembola and probably Thysanura, though it 
 has not yet been discovered in the more specialized insects. 
 
 Fig. 5 
 
 Paramedian section of an embryo of the collembolan Aniirida maritima, to show 
 the primitive cephalic ganglia. /, ocular neuromere; 2, antennal; s, intercalary; 4, 
 mandibular; 5, superlingual; 6, maxillary; 7, labial; i', protboracic; 9, mesotboracic; 
 a, antenna; /, labrum; li, labium; P, P, l^, thoracic legs; m, mandible; m.v, maxilla. 
 *— After FoLSOM. 
 
 Thorax. — The thorax, or middle region, comprises the 
 three segments next behind the head, which are termed, respec- 
 tively, pro-, mcso- and inetathorax. In aculeate Hymenop- 
 tera, however, the thoracic mass includes also the first abdom- 
 inal segment, then known as the propodeuin, or median seg- 
 ment. Each of the three thoracic segments bears a pair of 
 
ANATOMY AND PHYSIOLOGY 
 
 47 
 
 ps 
 
 Diagram of the principal scle- 
 rites of a thoracic segment, em, 
 epimeron; es, episternum; p, 
 praescutum; pr, parapteron; ps, 
 postscutellum; s, scutum; si, 
 scutellum; st, sternum. — After 
 
 COMSTOCK. 
 
 legs in almost all adnlt insects, but only the meso- and meta- 
 thorax may bear wings. 
 
 The differentiation of the thorax as a distinct region is an 
 incidental result of the development of the organs of locomo- 
 tion, particularly the wings. Thus 
 in legless (apodoiis) larvcC the ""-.S'- 
 
 thoracic and abdominal segments 
 are alike ; when legs are present, but 
 no wings, the thoracic segments are 
 somewhat enlarged ; and when 
 wings occur, the size of a wing- 
 bearing segment depends on the vol- 
 ume of the wing muscles, wdiich in 
 turn is proportionate to the size of 
 the wings. When \yings are absent 
 (as in Thysanura and Collembola) 
 or the two pairs equal in area (as 
 in Termitidse, Odonata, Trichoptera 
 and most Lepidoptera) the meso- and metathorax are equal. If 
 the fore wdngs exceed the hind ones (Ephemeridce, Hymenop- 
 tera) the mesothorax is proportionately larger than the meta- 
 thorax ; as also in Diptera, where no hind wings occur. If 
 the fore wings are small (Coleoptera) or almost absent (Sty- 
 lopidse) the mesothorax is correspondingly smaller than the 
 metathorax. The prothorax, which never bears wings, may 
 be enlarged dorsally to form a protective shield, as in Orthop- 
 tera, Hemiptera and Coleoptera; or, on the contrary, may be 
 greatly reduced, as in Ephemerida. Odonata, Lepidoptera and 
 Hymenoptera. In the primitive Apterygota the prothorax 
 may become reduced (many Collembola) or slightly enlarged 
 (Lepisnia) . 
 
 The dorsal wall of a thoracic segment is termed the notuui, 
 or tergum; the ventral wall, the sternum; and each lateral wall, 
 a pleuron; the restriction of these terms to particular segments 
 of the thorax being indicated by the prefixes pro-, meso- or 
 Dicta-. These parts are usually divided by sutures into dis- 
 
48 
 
 ENTOMOLOGY 
 
 Fig. 57, 
 
 tinct pieces, or sclerites, as represented diagrammatically in 
 Fig. 56. Thus the tergnm of a wing-bearing segment is re- 
 garded as being composed of four sclerites (tcrgitcs, Fig. 57), 
 namely and in order, prccscutuiii, sciitum, scutcUnm and post- 
 scutcUimi. The scutum and scutellum are commonly evident, 
 but the two other sclerites are 
 usually small and may be absent. 
 Each pleuron consists chiefly of 
 two sclerites {plciwitcs, Fig: 58), 
 separated from each other by a 
 more or less oblique suture. 
 The anterior of these two, which 
 joins the sternum, is termed the 
 cpistcniuni; the other, the cpi- 
 mcron. The former is divided 
 into two sclerites in Odonata and 
 both are so divided in Neuroptera. 
 The sternum, though usually 
 a single plate, is in some in- 
 stances divided into halves, as 
 in the cockroach, or even into 
 five sclerites (Forficulidse). 
 To these should be added the 
 pair 
 of erectile appendages of the 
 prothorax; and the paraptera, or fcgulcu, of Lepidoptera and 
 Flymenoptera — a pair of small sclerites at the bases of the 
 front wings. 
 
 Each thoracic segment bears a pair of spiracles in the em- 
 bryo and in some adults as well {Campodca, Heteroptera), 
 but in most imagines there are only two pairs of thoracic 
 spiracles, the suppressed pair being usually the prothoracic. 
 
 The sclerites of the thorax owe their origin probably to 
 local strains on the integument, brought about by the muscles 
 of the thorax. Thus the primitively wingless Thysanura and 
 Collembola have no hard thoracic sclerites, though certain 
 
 Dorsal aspect of the thorax of a 
 beetle, Hydrous piceus. I, pronotum; 
 2, mesoprjescutum; j, mesoscutum; 4, 
 niesoscutellum; 5, mesopostscutellum; 
 6, metaprKscut,um; 7, metascutum; 5, 
 
 metascutellum; 9, metapostscutellum. p^f^j^j^ ^f Lcpidoptcra a 
 
 —After Newport. t ^ i i 
 
ANATOMY AND PHYSIOLOGY 
 
 49 
 
 creases about the Ijases of the legs may be reg-arded as incipi- 
 ent sutures, produced mechanically by the movements of the 
 
 '"13 
 
 Ventral aspect of a carabid beetle, Galerita Janus, i, prosternum; 2, proepisternum, 
 3, proepimeron; 4, coxal cavity; 5, inflexed side of pronotum; 6, mesosternum; 7, meso- 
 episternum; 8, mesoepimeron; 9, metasternum; 10, antecoxal piece; 11, metaepisternum; 
 12, metaepimeron; 13, inflexed side of elytron; a, sternum of an abdominal segment; 
 an, antenna; c, coxa; f, femur; Ip, labial palpus; md, mandible; mp, maxillary palpus; 
 t, trochanter; tb, tibia; ts, tarsus. 
 
 legs. In soft nymphs and larvae, the sclerites do not form until 
 the wings develop ; and in forms that have nearly or quite lost 
 their wings, as Pediculidse, Mallophaga,Siphonaptera and some 
 5 
 
so 
 
 ENTOMOLOGY 
 
 Fig. 59. 
 
 parasitic Diptera, the sclerites of the thorax tend to disappear. 
 Furthermore, the absence of sclerites in the prothorax is prob- 
 ably due to the lack of prothoracic wings, notwithstanding- the 
 so-called obsolete sutures of the pronotum in grasshoppers. 
 
 Endoskeleton. — An insect has no internal skeleton, strictly 
 speaking, though the term endoskeleton is used in reference to 
 certain ingrowths of the external cuticula which serve as me- 
 chanical supports or as protections 
 for some of the internal organs. 
 The tentorium of the head has al- 
 ready been referred to. In the 
 thorax three kinds of chitinous in- 
 growths may be distinguished ac- 
 cording to their positions : ( i ) phrog- 
 inas, or dorsal projections; (2) 
 apodeines, lateral; (3) apophyses, 
 ventral. The phragmas (Fig. 59) 
 are commonly three large plates, 
 pertaining to the meso- and meta- 
 thorax, and serving for the origin 
 of indirect muscles of flight in 
 Lepidoptera, Diptera, Hymenoptera 
 and other strong-winged orders. The 
 apodemes are comparatively small in- 
 growths, occurring sometimes in all 
 three thoracic segments, though usu- 
 ally absent in the prothorax. The 
 apophyses occur in each thoracic seg- 
 ment as a pair of conspicuous proc- 
 esses, which either remain separate 
 or else unite more or less ; leaving, however, a passage for the 
 ventral nerve cord. 
 
 These endoskeletal processes serve chiefly for the origin of 
 muscles concerned with the wings or legs, and are absent in 
 such wingless forms as Thysanura, Pediculidze and Mal- 
 lophaga. 
 
 Transverse sections of the 
 thoracic segments of a beetle, 
 GoUathus, to show the endo- 
 skeletal processes. A, pro- 
 thorax; B, mesothorax; C, 
 metathorax; a, a, apophyses; 
 ad, apodeme; p, phragma. — 
 After KoLBE. 
 
ANATOMY AND PHYSIOLOGY 
 
 51 
 
 Vir,. 60. 
 
 tb 
 
 Some ambiguity attends the use of these terms. Thus some 
 writers use the term apodemes for apophyses and others apply 
 the term apodeme to any of the three 
 kinds of ingrowths. 
 
 Legs. — Tn ahnost all adult insects and 
 in most larv;c each of the three thoracic 
 segments bears a pair of legs. The leg 
 is articulated to the sternum, episternum 
 and epimercMi and consists of five seg- 
 ments (Fig. 60). in the following order: 
 coxa, f roc Jia liter, femur, tibia, tarsus. 
 The coxa, or basal segment, often has a 
 posterior sclerite. the trochantinc} The 
 trochanter is small, and in parasitic 
 Hymenoptera consists of two subseg- 
 ments. The femur is usually stout and 
 conspicuous, the tibia commonly slender. 
 The tarsus, rarely single-jointed, consists 
 usually of five segments, the last of which 
 bears a pair of claws in the adults of 
 most orders of insects, and a single claw 
 in larv£e ; between the claws in most 
 imagines is a pad. usually termed the 
 pulvillus, or cnipodiuin. 
 
 Adaptations of Legs. — The legs ex- 
 hibit a great variety of adaptive modifica- 
 tions. A walking or running insect, as a 
 carabid or cicindelid beetle (Fig. 62. A) presents an average 
 condition, as regards the legs. In leaping insects (grasshop- 
 pers, crickets. Halfica) the hind femora are enlarged (B) to 
 accommodate the powerful extensor muscles. In insects that 
 make little use of their legs, as May flies and Tipulidas, these 
 appendages are but weakly developed. The spinous legs of 
 
 ^ But on account of the ambiguous use of this last term, the name mcron 
 (Fig. 61), proposed by WaUon, is to be preferred. 
 
 Leg of a beetle, Calo- 
 soma calidum. c, coxa; 
 cl, claws; f, femur; s, 
 spur; t^-t^, tarsal seg- 
 ments; tb, tibia; tr, 
 trochanter. 
 
52 
 
 ENTOMOLOGY 
 
 Fig. 6i. 
 
 Left hind leg of Bittacus. c, coxa 
 genuina; em, epimeron; es, episternum; /, 
 femur; m, meron; t, trochanter. 
 
 dragon flies form a basket for catching the prey on the wing. 
 Modifications of the front legs for the purpose of grasping 
 occur in many insects, as the terrestrial families Mantidse (C) 
 and Reduviid?e and the aquatic families Belostomid^e and 
 
 Naucoridae {D). Swim- 
 ming species present special 
 adaptations of the legs (Fig. 
 228), as described in the 
 chapter on aquatic insects. 
 In digging insects, the fore 
 legs are expanded to form 
 shovel-like organs, notably 
 in the mole-cricket (Fig. 62, 
 E) , in which the fore tibia 
 has some resemblance to the 
 human hand, while the tarsus and tibia are remarkably adapted 
 for cutting roots, after the manner of shears. The Scara- 
 bseidas have fossorial legs, the anterior tarsi of which are in 
 some genera reduced (F) or absent; they are rudimentary in 
 the female {G) of Phancuus carnifex and absent in the male 
 (//), and absent in both sexes of Deltochilum. Though 
 females of Phancuus lose their front tarsi by digging, the de- 
 generate condition of these organs cannot be attributed to the 
 inheritance of a mutilation, but may have been brought about 
 by disuse ; though no one has explained why the two sexes 
 should differ in this respect. Many insects use the legs to 
 clean the antennae, head, mouth parts, wings or legs ; the honey 
 bee (with other bees, also ants, Carabidse, etc.) has a special 
 antenna-cleaner on the front legs (Fig. 263, D), which is 
 described, with other interesting modifications of the legs, on 
 page 271. 
 
 Indeed, the legs serve many such minor purposes in addi- 
 tion to locomotion. They are generally used to hold the 
 female during coition, and in several genera of Dytiscid?e 
 (Dytiscus, Cybister) the male (Fig. 62, /) has tarsal disks and 
 cupules, chiefly on the front tarsi, for this purpose. Among 
 
ANATOMY AND PHYSIOLOGY 
 
 53 
 
 Fig. 62. 
 
 Adaptive modifications of the legs. A, Cicindela se.vguttata; B, Nemohius vittatus, 
 hind leg; C, Stagmomantis Carolina, left fore leg; D, Pelocoris femorata, right fore 
 leg; E, Gryllotalpa borealis, left fore leg; F, Canthon lavis, right fore leg; G, PJiancciis 
 carnifex, fore tibia and tarsus of female; H, P. carnifex, fore tibia of male; /, Dytis- 
 cus fascizentris, right fore leg of male; c, coxa; /, femur; s, spur; t, trochanter; tb, 
 tibia; ts, tarsus. 
 
54 
 
 ENTOMOLOGY 
 
 Fig. 63. 
 
 Other secondary sexual peculiarities of the legs may be men- 
 tioned the tibial brushes of the male Catocala concnmhens, 
 regarded as scent organs, and the queer appendages of male 
 Dolichopodidse that dangle in the 
 air as these flies perform their 
 dances. 
 
 The pulvillus is commonly an 
 adhesive organ. In flies it has 
 glandular hairs that enable the in- 
 sects to walk on smooth surfaces 
 and to walk upside down ; so also 
 in many beetles and notably in the 
 honey bee (Fig. 63) ; in this insect 
 the pulvillus is released rapidly 
 from the surface to which it has 
 been applied, by rolling up from the 
 edges inward. 
 
 Sense organs occur on the legs. 
 Thus tactile hairs are almost always 
 present on these appendages, while 
 auditory organs occur on the front tibise of Locustidae, Gryllidie 
 and some ants. Finally, the legs may be used to produce sound, 
 
 Fig. 64. 
 
 Foot of honey bee, Apis mcl- 
 lifcra. c. c, claws; p, pulvillus; 
 fi-f", tarsal segments. — After 
 Cheshire. 
 
 Caterpillar of Plilegethontius sexta. Natural size. 
 
ANATOMY AND PHYSIOLOGY 
 
 55 
 
 as in Stenohothrus and such other AcridiicLx as stridulate by 
 rubbing the femora against the tegmina. 
 
 Legs of Larvae. — Tlioracic legs, terminating in a single 
 claw, are present in most larvce. Cateri)illars have, in addi- 
 tion, fleshy abdominal legs (Fig. 64) ending in a circlet of 
 hooks. Most caterpillars have five pairs of these legs (on 
 abdominal segments 3, 4, 5, 6 and 10), but the rest vary in 
 this respect. ' Thus Lagoa has seven pairs (segments 2-7 and 
 10) and GeometridcT two (segments 6 and 10), while a few 
 caterpillars (Tischcria, Limacodcs) have none. Larvae of 
 
 Fig. 65. 
 
 Mechanics of an insect's leg. a, axis of coxa; c, coxa; cl, claw; e, extensor of 
 tibia; ec, extensor of claw; et, extensor of tarsus; f, flexor of tibia; fc, flexor of 
 claw; ft, flexor of tarsus; r, r, rotators of coxa; s, spur; t, trochanter muscle (elevator 
 of femur) ; ti, tibia. — After Graber. 
 
 saW' flies (Tenthredinidas) have seven or eight pairs of abdom- 
 inal legs and larv?e of most Panorpidse, eight pairs. Not a 
 few coleopterous larv?e (some Cerambycidre, Phytonomiis) 
 also have abdominal legs, which are incompletely developed, 
 however, as compared with those of Lepidoptera. 
 
 The legless, or apodous, condition occurs frequently among 
 larvae and always in correlation wath a sedentary mode of life; 
 as in the larvae of many Cerambycidse, nearly all Rhynchoph- 
 ora, a few^ Lepidoptera, all Diptera, and all Hymenoptera ex- 
 cept Tenthredinida?, Siricidre, and other Terebrantia. 
 
56 
 
 ENTOMOLOGY 
 
 Fig. 66. 
 
 Among adult insects, female scale insects are exceptional in 
 being legless. 
 
 Walking. — An adult insect, when walking, normally uses 
 its legs in two sets of three each ; thus the front and hind legs 
 of one side and the middle leg of the other move forward 
 almost simultaneously — though not quite, for the front leg 
 moves a little before the middle one, 
 which, in turn, precedes the hind leg. 
 During these movements the body is sup- 
 ported by the other three legs, as on a 
 tripod. The front leg, having been ex- 
 tended and its claws fixed, pulls the body 
 forward by means of the contraction of 
 the tibial flexors;, the hind leg, on the 
 contrary, pushes the body, by the short- 
 ening of the tibial extensors, against the 
 resistance afforded by the tibial spurs ; the 
 middle leg acts much like the hind one, 
 but helps mainly to steady the body. 
 Different species show different peculiari- 
 ties of gait. In its analysis, the walking 
 of an insect is rather intricate, as Graber 
 and Marey have shown. 
 
 The mode of action of the principal 
 leg muscles may be gathered from Fig. 
 65. Here the flexion of the tibia would 
 cause the tibial spur (s) to describe the 
 line si; and the backward movement of 
 die leg due to the upper coxal rotator r 
 would cause the spur to follow the arc s j. 
 As the resultant of both these movements, 
 the path actually described by the tibial 
 spur is s 2 : then, as the leg moves forward, the curve is con- 
 tinued into a loop. 
 
 Caterpillars use their legs successively in pairs, and when 
 the pairs of legs are few and widely separated, as in Geomet- 
 ridae, a curious looping gait results. 
 
 Muscles of left mid 
 leg of a cockroach, pos- 
 terior aspect. ahc, 
 ductor of coxa; 
 adductor of coxa ; 
 extensor of femur; 
 extensor of tibia; 
 flexor of femur; 
 flexor of tibia ; 
 flexor of tarsus; rt 
 tractor of tarsus. — After 
 MiALL and Denny. 
 
ANATOMY AND PHYSIOLOGY 57 
 
 The leg- muscles of a cockroach are shown in ¥\s^. 66. 
 
 Leaping. — The hind legs, inserted nearest the center of 
 gravity, are the ones employed in leaping, and they act to- 
 gether. A grasshopper prepares to jnmp hy hending the 
 femur back against the tibia; to make the jump, the tibia is 
 jerked back against the ground, into which the tibial spurs are 
 driven, and the straightening of the leg by means of the pow- 
 erful extensors throws the insect into the air. At the distal 
 end of the femur are two lobes, one on each side of the tibia, 
 which prevent woljbling movements of the tibia. 
 
 Wings. — The success of insects as a class is to be attributed 
 largely to their possession of wings. These and the mouth 
 parts, surpassing all the other organs as regards range of dif- 
 ferentiation, have furnished the best criteria for the purposes 
 of classification. The wings of insects present such countless 
 differences that an expert can usually refer a detached wing 
 to its proper genus and often to its species, though no less 
 than three hundred thousand species of insects are already 
 known. 
 
 Typically, there are two pairs of wings, attached respec- 
 tively to the mesothorax and the metathorax, the prothorax 
 never bearing wings, as was said. \\'hen only one pair is 
 present it is almost invariably the anterior pair, as in Diptera 
 and male Coccidse, though in male Stylopidse it is the posterior 
 pair, the fore wnngs being rudimentary. 
 
 In bird lice, fieas and most other parasitic insects, the wnngs 
 have degenerated through disuse. In Thysanura and Collem- 
 bola there are no traces of wings even in the embryo ; whence 
 it is inferred that wings originated later than these orders of 
 insects. 
 
 Miiller and Packard have regarded the wings as tergal out- 
 growths; Tower, however, has recently shown that the wings 
 of Coleoptera, Orthoptera and Lepidoptera are pleural in ori- 
 gin, arising just below the line where later the suture between 
 the pleuron and tergum will originate, though the wings may 
 subsequently shift to a more dorsal position. 
 
58 ENTOMOLOGY 
 
 Modifications of Wings. — Being commonly more or less 
 triangular, a wing presents three margins: front (costal), 
 outer (apical) and inner (anal). Various modifications occur 
 in the front wings, which are in many orders more useful for 
 protection than for flight. Thus, in Orthoptera, they are 
 leathery, and are known as tcguiina; in Coleoptera they are 
 usuall}^ horny, and are termed elytra ; in Heteroptera. the hase 
 of the front wing is thickened and the apex remains mem- 
 branous, forming a heinclytron. Diptera have, in place of the 
 hind wings, a pair of clubbed threads, known as balancers, or 
 halteres, and male Coccidse have on each side a bristle that 
 hooks into a pocket on the wing and serves to support the lat- 
 ter. In many muscid flies a doubly lobed membranous squama 
 occurs at the base of the wing. 
 
 In Hymenoptera the front and hind wings of the same side 
 are held together by a row of hooks (hamuli) ; these are situ- 
 ated on the costal margin of the hind wing and clutch a rod- 
 like fold of the fore wing. In very many moths, the two 
 wings are enabled to act as one by means of a frenulum, con- 
 sisting of a spine or a bunch of bristles near the base of the 
 hind wing, which, in some forms, engage a membranous loop 
 on the fore wing. 
 
 Venation, or Neuration. — A wing is divided 1)y its veins, 
 or nervures, into spaces, or cells. The distribution of the 
 veins is of great systematic importance but. unfortunately, the 
 homologies of the veins in the different orders of insects have 
 not been fixed, until recently, so that no little confusion has 
 existed upon the subject. For example, the term discal cell, 
 used in descriptions of Lepidoptera, Diptera, Trichoptera and 
 Psocid?e, has in no two of these groups been applied to the 
 same cell. The admirable work of Comstock and Needham. 
 however, seems to settle this disputed subject. By a study of 
 the tracheae which precede and, in a broad way. determine the 
 positions of the veins, these authors have arrived at a primi- 
 tive type of tracheation (Fig. 67) to which the more complex 
 types of tracheation and venation may be referred. 
 
ANATOMY AND PHYSIOLOGY 59 
 
 In general, the following principal longitudinal veins may 
 be distinguished, in the following order: costa, subcosfa, 
 radius, media, cubitus and aiml (Figs. 67-71). 
 
 Hypothetical type of venation. A, anal vein; C, costa; Cu, cubitus; M, media; R, 
 radius; Sc, subcosta. — Figs. 67-71 after Comstock and Needham. 
 
 The costa (C) strengthens the front margin of the wing 
 and is essentially unbranched. 
 
 The subcosta (Sc) is close behind the costa and is un- 
 branched in the imagines of many orders in which there are 
 few wing veins, though it is typically a forked vein. 
 
 The radius (R), though subject to much modification, is 
 typically five-branched, as in Fig. 67. The second principal 
 branch of the radius is termed the radial sector (Rs). 
 
 The media (M) is often three-branched and is typically 
 four-branched, according to Comstock and Needham. 
 
 The cubitus (Cu) has two branches. 
 
 The anal veins (A) are typically three, of which the first 
 is generally simple, while the second and third are many- 
 branched in wings that have an expanded anal area. 
 
 The Plecoptera, as a whole, show the least departure from 
 the primitive type of venation ; which is well preserved, also, 
 in the more generalized of the Trichoptera. 
 
 Starting from the primitive type, specialization has occurred 
 in two ways : by reduction and by addition. Reduction oc- 
 curs either by the atrophy of \'eins or by the coalescence of 
 two or more adjacent veins. Atrophy explains the lack of all 
 but one anal vein in RJiypJius (Fig. 68) and other Diptera, 
 
6o 
 
 ENTOMOLOGY 
 
 and the absence of the base of the media in Anosia (Fig. 69) 
 and many other Lepidoptera ; in the pupa of Anosia, the media 
 may be found complete. Coalescence " takes place in two ways : 
 first, the point at which two veins separate occurs nearer and 
 
 /St A Cu^ 
 
 Wing of a fly, RliypJitis. Lettering as before. 
 
 nearer the margin of the wing, until finally, when the margin 
 is reached, a single vein remains where there were two before ; 
 second, the tips of two veins may approach each other on the 
 marsrin of the wing until they unite, and then the coalescence 
 
 Fig. 
 
 Rl R2 
 
 2dA 
 
 Wing of a butterfly, Anc 
 
 Lettering as before. 
 
 proceeds towards the base of the wing." (Comstock and Need- 
 ham.) The former, or outward, kind of coalescence is com- 
 mon in most orders of insects; the latter, or inward, kind is 
 especially prevalent in Diptera. 
 
 Specialization by addition occurs by a multiplication of the 
 branches of the principal veins. 
 
ANATOMY AND niYSIOLOGY 
 
 6i 
 
 Comstock and Needham have succeeded in homologizing 
 practically all the types of neuration, including such perplex- 
 ing types as those of Ephemerida (Fig. 70), Odonata (Fig. 
 20, B) and Hymenoptera (F^ig. 71), and their thorough work 
 affords a sound basis for a rational terminology of the wing 
 
 igs of a May fly 
 
 g as before. 
 
 veins ; there is no longer any excuse for the lamentable confu- 
 sion that has hitherto attended the study of venation. 
 
 Folding of Wing.^ — In some beetles (as Chrysobofhris) the 
 wings are no larger than the elytra and are not folded ; in 
 
 Fig. 71. 
 
 A typical hymenopterous wing. Lettering as before. 
 
 others, however, the wing's exceed the elytra in size, and when 
 not in use are folded under the elytra in ways that are simple 
 but efficient, as described by Kolbe and by Tower. To be 
 understood, the process of folding should be observed in the 
 living insect. As described by Tower for the Colorado potato 
 
02 ENTOMOLOGY 
 
 beetle, the folded wing (Fig. 72, B) exhibits a costal joint 
 (a), a fold parallel to the transverse vein (b), and a complex 
 joint at d. The wing rotates upon the articular head (ah) 
 and when folded back beneath the wing-covers the inner 
 end of the cotyla (c) is brought into contact with a chitin- 
 
 FiG. 72. 
 
 Mh an 
 
 Wing of Leptinotarsa dccemlincata. A, spread; B, folded; a, costal joint; ah, 
 articular head; an, anterior system of veins; b, transverse vein; c, cotyla; d, joint; 
 m, middle system of veins; p, posterior system of veins. — After Tower. 
 
 ous sclerite of the thorax, which stops the further movement 
 of the cotyla medianward, and as the wing swings farther back 
 the middle system of veins (///) is pushed outward and ante- 
 riorly. This motion, combined with the backward movement 
 of the wing as a whole, produces the folding of the distal end 
 of the wing. There are no traces of muscles or elastic liga- 
 ments in the wing which could aid in the folding. 
 
 Mechanics of Flight. — The mechanism of insect flight is 
 much less complex than one might anticipate. Indeed, owing 
 to the structure of the wing itself, simple up and down move- 
 ments are sufiicient for the simplest kind of flight. During 
 
ANATOMY AND PHYSIOLOGY 63 
 
 oscillation, the ])lane of the \vin<;- changes, as may be demon- 
 strated by holding" a detached wing by its base and blowing at 
 right angles to its snrface ; the membrane of the wing" then yields 
 to the pressure of the air while the rigid anterior margin does 
 not, to any great extent. Similarly, as the wing moves down- 
 ward the membrane is inclined upward l)y the resistance of the 
 air, and as the wing moves upward the membrane bends down- 
 ward. Therefore, by becoming deflected, the wing encounters 
 a certain amount of resistance from 
 behind, which is sufficient to propel 
 the insect. The faster the wings \N\ 
 vibrate, the greater t.he deflection, \ 
 the greater the resistance from be- 
 hind, and the faster the flight of the 
 insect. 
 
 The path traced in the air bv Trajectory of the wing of an 
 .,,.,. . ' insect. 
 
 a rapidly vibratmg wmg may be 
 
 determined by fastening a bit of gold leaf to the tip of the 
 wing and allowing the insect — a wasp, for example — to vibrate 
 its wings in the sunlight, against a dark background. Under 
 these conditions, the trajectory of the wing appears as a lumi- 
 nous elongate figure 8. During flight, the trajectory consists 
 of a continuous series of these figures, as in Fig. 73. 
 
 Marey, the chief authority on animal locomotion, used 
 chronophotography, among other methods, in studying the 
 process of flight, and obtained at first twenty, and later one 
 hundred and ten, successive photographs per second of a bee 
 in flight. As the wings were vibrating 190 times per second, 
 however, the images evidently represented isolated and not 
 consecutive phases of wing movement. Nevertheless, the 
 images could be interpreted without difficulty, in the light of 
 the results obtained by other methods. At length he obtained 
 sharp but isolated images of vibrating wings with an exposure 
 of only 1/25,000 of a second. 
 
 The frequency of wing vibration may be ascertained from 
 the note made by the wing — if it vibrates rapidly enough to 
 
64 
 
 ENTOMOLOGY 
 
 make one ; and, in any case, may be determined graphically by 
 means of a kymograph, which, in one of its forms consists of 
 a cylinder covered with smoked paper and revolved by clock- 
 work at a uniform rate. The insect is held in such a position 
 that each stroke of the wing makes a record on the smoked 
 paper, as in Fig. 74. 
 
 Comparing this record with one made 
 
 Fig. 74. 
 
 Records of wing vibration. A, mosquito, Anopheles. Above is the wing record 
 and below is the record of a tuning fork which vibrated 264.6 times per second. B, 
 wasp, Polistes. Tlie tuning fork in this instance had a vibration frequency of 97.6. 
 
 on the same paper by a tuning fork of known vibration period, 
 the frequency of wing vibration can be determined with great 
 accuracy. As the wing moves in the arc of a circle, the radius 
 of which is the length of the wing, the extreme tip of the wing 
 records only a short mark; if, however, the wing is pressed 
 against the smoked cylinder, a large part of the figure 8 trajec- 
 tory may be obtained, as in Fig. 74, B. The wings of the two 
 sides move synchronously, as Marey found. 
 
 The smaller the wings are, the more rapidly they vibrate. 
 Thus a butterfly (P. rapcc) makes 9 strokes per second, a 
 dragon fly 28, a sphingid moth 72, a bee 190 and a house 
 fly 330. 
 
 Wing Muscles. — The base of a wing projects into the 
 thoracic cavity and serves for the insertion of the direct mus- 
 cles of flight. Regarding the wing as a lever (Fig. 75, A), 
 
ANATOMY AND PHYSIOLOGY 
 
 ^S 
 
 with the fiilcrnni at />, it is easy to understand how the con- 
 traction of muscle c raises the wing and that of muscle d low- 
 ers it. These muscles are shown diagrammatically in Fig. 
 75. B. Besides these, there arc certain muscles of Ihgiit which 
 act indirectly upon the wings, by altering the form of the 
 thoracic wall. Thus 
 the muscle ic (Fig. 75, 
 B) elevates the wing 
 by pulling the tergum 
 toward the sternum : 
 and the longitudinal 
 muscle /(/ depresses the 
 wing indirectly by 
 arching the tergum of 
 the thorax. 
 
 Though up and 
 down movements are 
 all that are necessary 
 for the simplest kind 
 of insect flight, the 
 process becomes com- 
 plex in proportion to 
 the efficiency of the 
 flight. Thus in dragon 
 flies there are nine 
 muscles to each wing: 
 five depressors, three 
 elevators and one ad- 
 ductor. 
 
 Abdomen. — The 
 chief functions of the 
 al)domen are respiration and reproduction, to which should be 
 added digestion. The abdomen as a whole has undergone less 
 differentiation than the thorax and presents a simpler and more 
 primitive segmentation. 
 
 Segments. — A tvpical abdominal segment bears a dorsal 
 6 
 
 A, diagram to illustrate the action of the wing 
 muscles of an insect. B, diagram of wing mus- 
 cles, a, alimentary canal; en, muscle for con- 
 tracting the thorax, to depress the wings; d, de- 
 pressor of wing; e, elevator of wing; ex, muscle 
 for expanding the thorax, to elevate the wings; 
 id, indirect depressor; ie, indirect elevator; /, leg 
 muscle; p, pivot, or fulcrum; s, sternum; i, ter- 
 gum ; wg, wing. — After Graber. 
 
66 ENTOMOLOGY 
 
 plate, or fergum, and a ventral plate, or sternum, the two being 
 connected by a pair of pleural membranes, which facilitate the 
 respiratory movements of the tergum and sternum. Most of 
 the abdominal segments have spiracles, one on each side, situ- 
 ated in or near the pleural membranes of the first seven or 
 eight segments. The total number of pairs of spiracles is as 
 follows : 
 
 Thoracic. Abdominal. Total. 
 
 Caiiipodca, 
 Japyx, 
 Mad! His, 
 Lcpisvia, 
 
 
 3 
 
 4 
 
 O 
 
 7 
 
 7 
 8 
 
 3 
 II 
 
 9 
 
 10 
 
 Blattidffi. Acridi 
 
 idae, 
 
 2 
 
 8 
 
 10 
 
 Odonata, 
 
 
 2 
 
 8 
 
 10 
 
 Heteroptera, 
 Lepidoptera, 
 Diptera, 
 
 
 3 
 
 2 
 
 2 
 
 7 
 7 
 7 
 
 10 
 
 9 
 9 
 
 In most embryo insects there are eleven pairs of spiracles 
 (three thoracic and eight abdominal) ; in adults, howexer, two 
 pairs are commonly suppressed — the prothoracic and the 
 eighth aljdominal. 
 
 Number of Abdominal Segments. — Though consisting 
 typically of ten segments — the number evident in such general- 
 ized insects as Thysanura and Ephemerida — eleven occur in va- 
 rious adult Orthoptera. with traces of a twelfth, while Hey- 
 mons has detected twelve abdominal segments in embryos of 
 Orthoptera and Odonata. In the more specialized orders, ten 
 may usually be distinguished with more or less difficulty, 
 though the number is apparently, and in some cases actually 
 less, owing to modifications of the base of the abdomen in 
 relation to the thorax, but especially to modifications of the 
 extremity of the abdomen, for sexual purposes. 
 
 Modifications. — In aculeate Hymenoptera the first segment 
 of the abdomen has been transferred to the thorax, where it 
 \?,kno\\md.'s,i\\t propodcum, or median segment; in other words, 
 what appears to be the first abdominal segment is actually the 
 second ; this, as in bees and wasps, often forms a petiole, which 
 enables the sting to be applied in almost any direction. In Cy- 
 nipidse the tergum of segment two or three occupies most of the 
 
ANATOMY AND PHYSIOLOGY 
 
 (V 
 
 the remaining segments being reduced and 
 
 llie terminal segments of the abdomen often 
 
 abdominal ma 
 inconspicuous. 
 
 telescope into one another, as in 
 many Coleoptera and Hymenop- 
 tera (ChrysididcT) . (ir undergo 
 other mo<litications of form and 
 position which obscure the seg- 
 mentation. As to the number of 
 evident (not actual) abdominal 
 segments. Coleoptera show five or 
 six ventrally and seven or eight 
 dorsally; Lepidoptera, seven in 
 the female and eight in the male ; 
 Diptera, nine (male Tipulid?e) or 
 only four or five ; and Hymenop- 
 tera, nine (Tenthredinid?e) or as 
 few as three (Chrysidid?e). In 
 the larvae of these insects, how- 
 ever, nine or ten abdominal seg- 
 ments are usually distinguishable, 
 though the tenth is frequently 
 modified, being in caterpillars 
 united with the ninth. 
 
 Appendages. — ^Rudimentary ab- 
 dominal limbs occur in Thysanura 
 (Machilis, Fig. 76). Functional 
 abdominal legs do not occur in 
 adult insects, but in larv?e the ab- 
 dominal pro-legs (often called " false legs," Fig. 64) are ho- 
 mologous with the thoracic legs and the other paired segmental 
 appendages, as the embryology shows. The embryo of Qican- 
 thus, according to Ayers, has ten pairs of abdominal appen- 
 dages (Fig. 196), equivalent to the thoracic legs. Most of 
 these embryonic abdominal appendages are only transitory, but 
 the last three pairs frequently persist to form the genitalia, as in 
 
 Ventral aspect of the abdomen 
 of a female Machilis maritima, to 
 show rudimentary Hmbs (a) of 
 segments two to nine. (The left 
 appendage of the ninth segment is 
 omitted.) c, c, c, cerci. — After 
 
 OUDF.MANS. 
 
68 
 
 ENTOMOLOGY 
 
 Abdomen of female beetle, Ccraiiibyx, in 
 which the last three segments are used as an 
 ovipositor. — After Kolbe. 
 
 Orthoptera (to which order Qicantluis l>elongs). In Collem- 
 bola, the embryo has paired abdominal hml)s, and those of the 
 first abdominal segment eventnally nnite to form the peculiar 
 
 I'ciitral tube (Fig. 12) 
 of these insects, while 
 those of the fourth seg- 
 ment form the character- 
 istic leaping organ, or 
 ////'(■///(/. 
 
 Cerci. — In many of the 
 more generalized insects, 
 the abdomen bears at its 
 extremity two or three 
 appendages termed ccrci. These occur in both sexes and are 
 frequently long and multiarticulate, as in Thysanura (Figs. 
 76,9, 10) and Ephemerida (Figs. 19, 5; 84), though shorter in 
 cockroaches and reduced to a single sclerite in Acridiidae (Fig. 
 87). The paired cerci, or ccrcopoda of Packard, are usually 
 though not always associated with the tenth abdominal seg- 
 ment and are homologous with legs, as Ayers has found in 
 Qicantluis and Wheeler in Xiphidiiiin. As to their function. 
 the cerci of Thysanura are tac- 
 tile, and those of the cockroach 
 olfactory, wdiile the cerci of 
 male Acridiidse often serve to 
 hold the female during copu- 
 lation. 
 
 Extremity of Abdomen.-^ 
 Various modifications of the terminal segments of the abdo- 
 men occur for the purposes of defsecation and especially repro- 
 duction. The anus, dorsal in position, opens always through 
 the last segment and is often shielded above by a suraual plate 
 and on each side by a lateral plate. The genital orifice is al- 
 ways ventral in position and occurs commonly on the ninth 
 abdominal segment, though there is some variation in this re- 
 spect. The external, or accessory, organs of reproduction are 
 termed the genitalia. 
 
 Fig. 78. 
 
 Abdomen of a female midge, Cccido- 
 myia leguminicola, to show the pseudo- 
 ovipositor. 
 
ANATOMY AND PHYSIOLOGY 
 
 69 
 
 Female Genitalia. — In Neiiroptera, Coleoptera, Lepido])tera 
 and Diptera the vagina simply opens to the exterior or else 
 with the anus into a common chamhcr, or cloaca. Often, as 
 in Ceramhy.x- (Fig. yy) and Cccidomyia ( Ing. /cS) the attenu- 
 
 FiG. 79. 
 
 Ovipositor of Locust a. A, lateral aspect; B, ventral aspect; C, transverse section; 
 c, cerci; d, dorsal valve; i, inner valve; v, ventral valve. The numbers refer to 
 abdominal segments. — After Kolbe and Dewitz. 
 
 ated distal segments of the abdomen serve the purpose of an 
 ovipositor; thus in Cecidomyiid?e, the terminal segments, tele- 
 scoped into one another when not in use, form when extruded 
 a lash-like organ exceeding frequently the remainder of the 
 body in length. 
 
 A true oz'iposifor occurs in Thysanura, Orthoptera. Odo- 
 nata, Hemiptera, Hymenoptera and some other orders of in- 
 sects. The ovipositor consists essentially of three pairs of 
 valves, or gonapophyscs — a dorsal, a ventral and an inner 
 pair. The two inner valves form a channel through which 
 the eggs are conveyed. In LocustidcC (Fig. 79) the three 
 
70 
 
 ENTOMOLOGY 
 
 valves of each side are held together 
 by tongues and grooves, which, how- 
 e\-er, permit sliding movements to take 
 place. INIost authorities have found 
 that the gonapophyses belong to the 
 segmental series of paired appendages 
 — are homodynamous with limbs — and 
 pertain commonly to abdominal segments 
 seven, eight and nine. 
 
 The ovipositor attains its greatest 
 complexity in Hymenoptera, in which 
 it becomes modified for 
 sawing, boring or sting- 
 ing. In Sirc.v (Fig. 80) 
 the inner valves are 
 united together ; in Apis 
 the dorsal valves are rep- 
 
 FlG. 82. 
 
 Cross section of the 
 ovipositor of Sircx. c, 
 channel; d, d, dorsal 
 valves; i, united inner 
 valves; v, v, ventral 
 valves. — After Taschen- 
 
 BERG. 
 
 Fig. 81. 
 
 Sting and poison, apparatus 
 of honey bee. ag, accessory 
 gland; p, palpus; pg, poison 
 gland (formic acid) ; r, reser- 
 voir; .?, sting. — After Kraepe- 
 
 Sting of honey bee. A, i, 2, .?, positions 
 in three successive thrusts; s, sheath. B, 
 cross section; c, channel; /, united inner 
 valves, forming the sheath; .', '', ventral 
 valves, or darts. — A, after Cheshire; B, after 
 Fencer. 
 
 resented by a pair of palpi, the 
 inner valves unite to form the 
 sheath (Fig. 8i, B), and the ven- 
 tral two form the darts, each of 
 which has ten barbed teeth behind 
 its apex, which tend to prevent 
 the withdrawal of the sting from a 
 wound. The action of the sting, as 
 
ANATOMY AND PHYSIOLOGY 
 
 71 
 
 described by Cheshire, is rather complex. Brielly, the sheath 
 
 serves to open a wound and to guide the 
 
 darts ; these strike in ahernately, inter- 
 rupted at intervals by the deeper pknig- 
 
 ing- of the sheath ( h^ig". 81, A). The 
 
 poison of the hone}' l:)ee is secreted l^y 
 
 two glands, one acid and the other alka- 
 line. The former (Fig. 82) consists of 
 
 a glandular region which secretes formic 
 
 acid, of a reservoir, and a duct that 
 
 empties its contents into the channel of 
 
 the sheath. The alkaline gland also 
 
 opens into the reser\-oir. It is said that 
 
 both fluids are necessary for a deadly 
 
 effect; and that in insects which simply 
 
 paralyze their prey, as the solitary wasps, 
 
 the alkaline glands are functionless. 
 Male Genitalia. — The poiis may be 
 
 hollow or else solid, and in the latter case 
 
 the contents of the ejaculatory duct are 
 
 spread upon its surface. Morphologically, the male gona- 
 pophyses correspond to those of the 
 female. The penis (Fig'. 83) rep- 
 resents the two inner valves of the 
 ovipositor and is frequently enclosed 
 by one or two pairs of valves. In 
 Ephemerida the two inner valves 
 are partly or entirely separate from 
 each other, forming two intromit- 
 tent organs (Fig. 84). 
 
 In male Odonata, the ejaculatory 
 duct opens on the ninth abdominal 
 segment, but the copulatory organ is 
 placed on the under side of the sec- 
 ond segment, to which the spermato- 
 zoa are transferred by the bending 
 
 of the abdomen. At copulation, the abdominal claspers of the 
 
 cniity of abdomen 
 of a male beetle, Hy- 
 drophilus, ventral aspect. 
 g, genitalia; p, penis; 
 Z'^, v^, pairs of valves 
 enclosing tbe penis; 6-9, 
 sterna of abdominal seg- 
 ments. — After KoLBE. 
 
 Extremity of abdomen of i 
 
 male May fly, Hexagenia z'aria 
 
 bills, ventral aspect. c, c, c 
 
 cerci; cl, cl, claspers; i, i, in 
 tromittent organs. 
 
72 
 
 ENTOMOLOGY 
 
 male grasp the neck of the female, and the latter bends her 
 abdomen forward nntil the tip reaches the peculiar copulatory 
 apparatus of the male. 
 
 Fig. 8s. 
 
 Genitalia of a moth, Samia cecropia. A, male; B, female; a, anus; c, c, claspers; 
 o, opening of common oviduct; p, penis; s, uncus (the doubly hooked organ); v, vesti- 
 bule, into which the vagina opens. The numbers refer to abdominal segments. 
 
 The claspers of the male consist of a single pair, variously- 
 formed. They are present in Ephemerida, Neuroptera. Tri- 
 choptera, Lepidoptera (Fig. 85), Diptera and some Hymen- 
 optera, though not in Coleoptera, and often afford good spe- 
 cific characters, a§ in Odonata. 
 
 Fig. 86. 
 
 B 
 
 Terminal abdominal appendages of a dragon fly, Plathemis trimaculata. A, male; 
 B, female. i, inferior appendage; s, s, superior appendages (cerci). The numbers 
 refer to abdominal segments. 
 
 Thanaos, the claspers are peculiar in being strongly asym- 
 metrical. In Odonata (Fig. 86, A) and Orthoptera (Fig. 
 87, A) the cerci of the male often serve as claspers. 
 
ANATOMY AND PHYSIOLOGY 
 
 73 
 
 In many insects the tergum of the last alxloniinal segment 
 forms a small siiraiial plate (Fig. 87, B, sp) ; this sometimes 
 
 Fig. 87. 
 
 8g 10 u 
 
 9 10 n 
 
 Extremity of the abdomen of a grasshopper, Melanoplus diffcrcntialis. A, male; 
 B, female. The terga and sterna are numbered, c, cercus; d, dorsal valves of ovi- 
 positor; e, egg guide; p, podical plate; s, spiracle; sp, suranal plate; 7', ventral valves 
 of ovipositor. 
 
 supplements the claspers of the male 
 Lepidoptera (Fig. 85, A, s). 
 
 heir function, as in 
 
 2. Integument 
 
 Insects excel all other animals in respect to adaptive modi- 
 fications of the integument. No longer a simple limiting 
 membrane, the integument has become hardened into an exter- 
 nal skeleton, evaginated to form manifold adaptive structures 
 such as hairs and scales, and invaginated, along with the un- 
 derlying cellular layer, to make glands of various kinds. 
 
 Chitin. — The skin, or cuticula,^ of an insect differs from 
 that of a worm, for example, in being thoroughly permeated 
 with a peculiar substance known as chitin — the basis of the 
 arthropod skeleton. This is a substance of remarkable sta- 
 bility, for it is unaffected by almost all ordinary acids and 
 alkalies, though it is soluble in sodic or potassic hypochlorite 
 (respectively, Eau de Labarraque and Eau de Javelle) and 
 yields to boiling sulphuric acid. If kept for a year or so 
 under water, however, chitin undergoes a slow dissolution, 
 
 ^ The cuticida of an insect should be distinguished from the cuticle of 
 a vertebrate, the former being a hardened fluid, while the latter consists 
 of cells themselves, in a dead and flattened condition. 
 
74 
 
 ENTOMOLOGY 
 
 possibly a putrefaction, which accounts in a measure for the 
 rapid disappearance of insect skeletons in the soil (Miall and 
 Denny). By boiling the skin of an insect in potassic hydrate 
 it is possible to dissolve away the cuticular framework, leav- 
 ing fairlv pure chitin, without destroying the organized form 
 of the integument, though less than half the weight of the 
 integument is due to chitin. The formula of chitin is given 
 as CgHisNOu or CisHigNOig by Krukenberg, and Packard 
 adopts the formula CisHgeNgOjo; though no two chemists 
 agree as to the exact proportions of these elements, owing 
 
 probably to variations in the 
 
 Fir 88 
 
 substance itself in different in- 
 sects or even in the same species 
 of insect. Iron, manganese 
 and certain pigments also enter 
 into the composition of the 
 integument. 
 
 Chitin is not peculiar to ar- 
 thropods, for it has been de- 
 tected in the setae and pharyn- 
 geal teeth of annelid worms, 
 the shell of Lingula and the 
 pen of the cuttle fish (Kruken- 
 berg). 
 
 The chitinous integument (Fig. 88) of most insects con- 
 sists of two layers : ( i ) an outer layer, homogeneous, dense, 
 without lamellae or pore canals, and being the seat of the cutic- 
 ular colors; (2) an inner layer, "thickly pierced with pore 
 canals, and always in layers of different refractive indices and 
 different stainability." (Tower.) These two layers, respec- 
 tively primary and secondary cuticula, are radically different 
 in chemical and physical properties. The chitinous cuticula 
 is secreted, as a fluid, from the hypodermis cells. Each layer 
 arises as a fluid secretion from the hypodermis cells, the pri- 
 mary cuticula being the first to form and harden. 
 
 The fluid that separates the old from the new cuticula at 
 
 - h 
 
 Section through integument of a 
 beetle, Chrysobothris. b, basement 
 membrane; c^, primary cuticula; c", 
 secondary cuticula; h, hypodermis cell; 
 n, nucleus. — After Tower. 
 
ANATOMY AND PHYSIOLOGY 
 
 75 
 
 ecdysis is poured over the liypoderniis In- eertain large special 
 cells, which, according to Tower, "are not true glands, but 
 the setigerous cells which, in early life, are chiefly concerned 
 with the formation of the hairs upon the body; but upon the 
 
 Fig. 89. 
 
 s 
 
 Modifications of the hairs of bees 
 D, Chclostoim 
 
 A, B, Mcgachile; C, E, F, Collates, 
 -After Saunders. 
 
 loss of these, the cell takes on the function of secreting the 
 exuvial fluid, which is most copious at pupation. These cells 
 degenerate in the pupa, and take no part in the formation of 
 the imaginal ornamentation." 
 
 Histology. — The chitinous cuticula owes its existence to 
 the activity of the underlying layer of hypodermis cells (Fig. 
 88). These cells, distinct in embryonic and often in early lar- 
 val life, subsecjuently become confluent by the disappearance of 
 the intervening cell walls, though each cell is still indicated by 
 its nucleus. The cells are limited outwardly by the cuticula 
 and inw^ardly by a delicate, hyaline bascinciit inciiibrauc; they 
 contain pigment granules, fat-drops, etc. 
 
 Externally the cuticula may be smooth, wrinkled, striate, 
 granulate, tuberculate, or sculptured in numberless other 
 ways ; it may be shaped into all manner of structures, some 
 of which are clearly adaptive, while others are unintelligible. 
 
76 
 
 ENTOMOLOGY 
 
 Fig. go. 
 
 Hairs, Setae and Spines. — These occur universally, serv- 
 ing a great variety of purposes ; they 
 are not always simple in form, but are 
 often toothed, branched or otherwise 
 modified (Fig. 89). Hairs and bris- 
 tles are frequently tactile in function, 
 over the general integument or else 
 locally; or olfactory, as on the antennae 
 of moths; or occasionally auditory, as 
 on the antennae of the male mosquito; 
 these and other sensory modifications 
 are described beyond. The hairy 
 
 Section of antenna of a 
 moth, Saturnia, to show 
 developing hairs, c, cutic- 
 ula; f, formative cell of 
 hair; h, hypodermis; t, 
 trachea. — After Semper. 
 
 pillars (as Isia isahcUa) probably pro- 
 tects them from sudden changes of 
 temperature. Hairs and spines fre- 
 quently protect an insect from its ene- 
 mies, especially when these structures 
 and emit a 
 
 Fig. 91. 
 
 are glandular 
 
 malodorous, nauseous or 
 irritant fluid. Glandular 
 hairs on the pulvilli of 
 many flies, beetles, etc., 
 enable these insects to walk 
 on slippery surfaces. The 
 twisted or branched hairs 
 of bees serve to gather 
 and hold pollen grains ; in 
 short, these simple struc- 
 tures exhibit a surprising 
 variety of adaptive modifica- 
 tions, many of which \\\\\ be 
 described in connection with 
 other subjects. 
 
 A hair arises from a 
 modified hypodermis cell (Fig. 90), the contents of which 
 
 Radial section through the base of a 
 
 hair of a caterpillar, Picris rapcr. c, cutic- 
 
 ula; /, formative cell; h, hair; hy, hypo- 
 dermis. 
 
ANATOMY AND PHYSIOLOGY 
 
 77 
 
 extend through a pore canal into the interior of the liair (Fig. 
 91 ) ; sometimes, to be sure, as in glandular or sensory hairs, 
 the hair cell is multinucleate, rep- 
 resenting, therefore, as many cells 
 as there are nuclei. The wall nf 
 a hair is continuous witli the gen 
 eral cuticula and at moulting each 
 hair is stripi)ed ofT with the rest 
 of the cuticula, leaving in its place 
 a new hair, which has been form- 
 ings inside the old one. 
 
 Scales. — Besides occurring 
 thrcaighout the order Lepidoptera 
 and in numerous Trichoptera. 
 scales are found in many Thys- 
 anura and Collembola. several 
 families of Coleoptera (including 
 DermestidcC and Curculionidre), a 
 few Diptera and a few Psocidie. 
 
 Though diverse in form (Fig. 
 92), scales are essentially flattened 
 sacs having at one end a short 
 pedicel for attachment to the in- 
 tegument. The scales usuallv bear markings, which are 
 more or less characteristic of the species ; these markings, 
 always minute, are in some species so exquisitely fine as 
 to test the highest powers of the microscope ; the scales 
 
 of certain Collembola {Lchi- 
 
 Fif-. 03 
 
 docyrtiis. etc. ) have long been 
 used, under the name of 
 " Podura " scales, to test the 
 resolving power of objec- 
 tives, for which purpose they 
 are excelled only by some of the diatoms. Butterfly scales 
 are marked with ])arallel longitudinal ridges (Fig. 92, C), 
 which are confined almost entirely to the upper, or ex- 
 
 X'arious forms of scales. 
 A, E, thysanuran, Machilis; B, 
 beetle, Anthrcnus; C, butterfly, 
 Pic'-is: D. moth, Limacodes. 
 
 Cross section of scale of Aiiosia. — 
 After Mayer. 
 
78 
 
 ENTOMOLOGY 
 
 posed, surface of the scale (Fig. 93) and number from 
 ^;^ or less (Anosia) to 1,400 (MorpJio) to each scale, the 
 
 _ strise being- from .002 mm. 
 
 Fig. 94. ^ 
 
 to .0007 mm. apart (Kel- 
 logg) ; between these longi- 
 tudinal ridges may be dis- 
 cerned delicate transverse 
 markings. Internally, scales 
 are hollow and often contain 
 pigments derived from the 
 blood. 
 
 On the wing of a butter- 
 fly the scales are arranged 
 in regular rows and overlap 
 one another, as in Fig. 94; 
 in the more primitive moths 
 and in Trichoptera. how- 
 Arrangement of scales on the wing of a evcr, their distribution is 
 
 butterfly, Papilio. . . , 
 
 rather irregular. 
 
 A scale is the equivalent of a hair, for (i) a complete series 
 
 of transitions from hairs to scales may be found on a single 
 
 individual (Fig. 95) ; and (2) hairs and scales agree in their 
 
 manner of development, as shown by Semper, Schaffer, Spu- 
 
 Fi 
 
 Hairs and scales of a moth, Sa)nia cccropia. 
 
 ler, Mayer and others. Both hairs and scales arise as pro- 
 cesses from enlarged hypodermis cells, or formative cells (Fig. 
 96). The scale at first contains protoplasm, which gradually 
 withdraws, 
 membranes of the scale together. 
 
ANATOMY AND PHYSIOLOGY 
 
 79 
 
 Uses of Scales. — Anions^- Tliysaniira and C"<)11cnil)c)la. scales 
 occur (Mily on such species as live in comparatively drv situa- 
 tions, from which it may be inferred that tlie scales serve to 
 retard the evaporation of moisture through tlie delicate integu- 
 ment of these insects. This inference is supported by the fact 
 
 Fig. 96. Fk;. 97. 
 
 Development of butterfly scales. 
 A, I'anessa; B, Anosia. b, base- 
 ment membrane; f, formative cell; 
 h, hypodermis; s, scale. — After 
 Mayer. 
 
 Androconia of butter- 
 flies. A, Pieris rapa; B, 
 Everes comyntas. 
 
 that none of the scaleless Collembola can live long in a dry 
 atmosphere ; they soon shrivel and die even under conditions 
 of dryness which the scaled species are able to withstand. In 
 Lepidoptera the scales are possibly of some value as a mechan- 
 ical protection; they have no influence upon flight, as Mayer 
 has proved, and appear to be useful chiefly as a basis for the 
 
8o 
 
 ENTOMOLOGY 
 
 development of color and color patterns — which are not infre- 
 cjuently adaptive. 
 
 Androconia. — The males of many butterflies, and the males 
 only, have peculiarly shaped scales known as androconia (Fig. 
 97) ; these are commonly confined to the upper surfaces of the 
 front wings, where they are mingled with the ordinary scales 
 or else are disposed in special patches or under a fold of the 
 
 costal margin of the wing 
 (Thanaos) . The characteris- 
 tic odors of male butterflies 
 have long been attributed to 
 these androconia and M. B. 
 Thomas has found that the 
 scales arise from glandular 
 cells, which doubtless secrete 
 a fluid that emanates from 
 the scale as an odorous va- 
 por, the evaporation of the 
 fluid being facilitated l)y the 
 spreading or branching form 
 of the androconium. Similar 
 scales occur also on the wings of various moths and some 
 Trichoptera (Mystacidcs) . 
 
 Glands. — A great many glands of various form and func- 
 tion have been found in insects. Most of these, being formed 
 from the hypodermis, may logically be considered here, ex- 
 cepting some which are intimately concerned with digestion 
 or reproduction. 
 
 Glandular Hairs and Spines. — The presence of adhesive 
 hairs on the empodium of the foot of a fly enables the insect 
 to walk on a smooth surface and to walk upside down ; these 
 tcnent hairs emit a transparent sticky fluid through minute 
 pore canals in their apices. The tenent hairs of Hylobius 
 (Fig. 98) are each supplied with a flask-shaped unicellular 
 gland, the glutinous secretion of which issues from the bulbous 
 
 Section across tarsus of a beetle, 
 Hylobius, to show bulbous glandular 
 hairs. — After Simmermacher. 
 
ANATOMY AND PHYSIOLOGY 
 
 8l 
 
 Fig. 99. 
 
 Stinging hair of a caterpillar, 
 Gastropacha. c, cuticula; g, 
 gland cell; h, hair; hy, hypo- 
 dermis. — After Claus. 
 
 extremity of the hair. Bulbous tenent hairs occur also on the 
 tarsi of Collembola, AphididcT and other insects. 
 
 Nettling- hairs or spines clothe the 
 caterpillars of certain Satuniiidae 
 { Autoiucris) , Liparichc. etc. These 
 spines ( h'ig. 99), which are sharp, 
 brittle and tilled \\ith poison. Ijreak 
 to pieces when the insect is handled 
 and cause a cutaneous irritation 
 much like that made by nettles. In 
 Lagoa crispata (Fig-. 100) the irri- 
 tating fluid is secreted, as is usual, 
 by several large hypodermal cells 
 at the base of each spine. These 
 irritating hairs protect their pos- 
 sessors from almost all birds except 
 cuckoos. 
 
 Repellent Glands. — The various 
 offensive fluids emitted by insects 
 
 are also a highly effective means of defence against birds 
 and other insectivorous vertebrates as well as against preda- 
 ceous insects. The blood itself serves 
 as a repellent fluid in the oil-beetles 
 (Meloidcc) and CoccinellicLne, issuing as 
 a yellow fluid from a pore at the end 
 of the femur. The blood of MeloidcT 
 ( one species of which is still used me- 
 dicinally under the name of " Spanish 
 Fly '■) contains cantharidine, an ex- 
 tremely caustic substance, which is an 
 almost perfect protection against birds, 
 reptiles and predaceous insects. Coccinel- 
 lid?e and Lampyridie are similarly exempt 
 from attack. Larvae of Cimhcx when 
 disturbed squirt jets of a watery fluid 
 from glands opening above the spiracles. Many Carabidse 
 eject a pungent and often corrosive fluid from a pair of anal 
 7 
 
 Fig. 100. 
 
 Stinging spines of 
 caterpillar, Lagoa c 
 pata. — After P..\ck.\rd. 
 
82 ENTOMOLOGY 
 
 glands (Fig. 146) ; this fluid in Brachinus, and occasionally 
 in Galerita janns and a few other carabids, volatilizes explo- 
 sively upon contact with the air. When one of these " bom- 
 bardier-beetles " is molested it discharges a puff of vapor, 
 accompanied by a distinct report, reminding one of a minia- 
 ture cannon, and this performance may be repeated several 
 times in rapid succession; the vapor is acid and corrosive, 
 staining the human skin a rust-red color. 
 Individuals of a large South American 
 Brachinus when seized " immediately 
 began to play off their artillery, burning 
 and staining the flesh to such a degree 
 that only a few specimens could be cap- 
 tured with the naked hand, leaving a 
 mark which remained for a considerable 
 time." (Westwood.) 
 
 As malodorous insects, Hemiptera are 
 
 Osmeterium of Pajyilio UOtOrioUS, thougll UOt 2. fcW hcmiptC- 
 
 polyxenes. / . r .1 • 
 
 rous odors are (apart from tlien^ associa- 
 tions) rather agreeable to the human olfactory sense. Com- 
 monly the odor is due to a fluid from a mesothoracic gland or 
 glands, opening between the hind coxae. 
 
 Eversible hypodermal glands of many kinds are common in 
 larvae of Coleoptera and Lepidoptera. The larvae of Mclasoma 
 lapponica, among other Chrysomelidae. evert numerous paired 
 vesicles which emit a peculiar odor. The caterpillars of our 
 Popiliu butterflies, upon being irritated, evert from the pro- 
 thorax a yellow Y-shaped osmeterium (Fig. loi) which dif- 
 fuses a characteristic but indescribable odor that is probably 
 repellent. The larva of Cerura everts a curious spraying 
 apparatus from the under side of the neck. 
 
 Alluring Glands. — Odors are largely used among insects to 
 attract the opposite sex. The androconia of male butterflies 
 have already been spoken of. Males of Catocala concumhens 
 disseminate an alluring odor from scent tufts on the middle 
 legs. Female saturniid moths (as eecropia and promcthca) 
 
ANATOMY AND PHYSIOLOGY 
 
 83 
 
 entice the males by means of a characteristic odor, emanating 
 from the extremity of the alxlonien. In lyca^nid caterpillars, 
 an eversible sac on the dorsum of the seventh abdominal seg- 
 ment secretes a sweet tlnid. for the sake of which these larvae 
 are sought out by ants. 
 
 Wax Glands. — Wax is secreted by insects of several orders, 
 but especially Hymenoptera and Hemiptera. In the worker 
 
 \'entral aspect of worker honey bee, showing the four pairs of wax scales. — After 
 Cheshire. 
 
 honey bee the wax exudes from unicellular hypodermal glands 
 and appears on the under side of the abdomen as four pairs 
 of wax scales (Fig. 102). Plant lice of the genus Schizo- 
 nciira owe their woolly appearance to dense white filaments of 
 wax, which arise from glandular hypodermal cells. In scale 
 insects, waxen threads, emerging from cuticular pores, become 
 matted together to form a continuous shield over and often 
 under the insect itself, the cast skins often being incorporated 
 into this waxen scale. The wax glands in Coccid?e are simply 
 enlarged hypodermis cells. 
 
 Silk Glands. — Larv?e of very diverse orders spin silk, for 
 the purpose of making cocoons, w-ebs, cases, and supports of 
 one kind or another. Silk glands, though most characteristic 
 of Lepidoptera and Trichoptera, occur also in the cocoon- 
 spinning larvre of not a few Hymenoptera (saw flies, ichneu- 
 mons, wasps, bees, etc.), in Diptera (Cecidomyiidse), Neurop- 
 
ENTOMOLOGY 
 
 tera (Chrysopidse, Myrmeleonidse), and in various larvae 
 whose pup?e are suspended from a silken support, as in the 
 
 coleopterous families Coc- 
 cinellidae and Chrysomel- 
 idse (in part) and the dip- 
 terous family Syrphid?e, 
 as well as most diurnal 
 Lepidoptera. 
 
 Fig. 104. 
 
 Head of caterpillar of Samia cecropia. a, 
 antenna; c. clypeus; /, labrura; Ip, labial palpus; 
 m, mandible; mp, maxillary palpi; o, ocelli; s, 
 spinneret. 
 
 The silk glands of caterpillars 
 are homologous with the true 
 salivary glands of other insects, 
 opening as usual through the hy- 
 popharynx, which is modified to 
 form a spinning organ, or spin- 
 ncrct (Fig. 103). The silk glands 
 of Lepidoptera are a pair of long 
 tubes, one on each side of the 
 body, but often much longer than 
 the body and consequently convo- 
 luted. Thus in the silk worm 
 {Bouihyx inori) they are from 
 four to five times as long as the 
 body and in Tclca polyphenius, 
 
 Silk glands of the silk worm, 
 Bombyx inori. cd, common duct; 
 d, one of the paired ducts; g, g, 
 Filippi's glands; gl, gland proper; 
 p, thread press; r, reservoir. 
 
 worm the convoluted glandular 
 
 portion of each tube (Fig. 104) opens into a dilatation, or silk 
 
 reservoir, which in turn empties into a slender duct, and the 
 
ANATOMY AND PHYSIOLOGY 
 
 85 
 
 Fig. 105. 
 
 B 
 
 two ducts join into a short common duct, which passes 
 tlirough the tuluilar spinneret. Two divisions of the spinning 
 tube are distinguished: (i) a posterior muscular i)ortion, or 
 thread-press and (2) an anterior directing tube. The thread- 
 press combines the two streams of 
 silk fluid into one, determines the form 
 of the silken thread and arrests the 
 emission of the thread at times, besides 
 having other functions. Tlie silk fluid 
 hardens rapidly upon exposure to the 
 air; about fifty per cent, of the fluid 
 is actual silk substance and the re- 
 mainder consists of protoplasm and 
 gum, with traces of wax, pigment, fat 
 and resin. 
 
 A transverse or radial section of a 
 silk gland shows a layer of glandular 
 epithelial cells, with the usual intima 
 and basement membrane ( Fig. 105 ) : 
 the cells are remarkably large and their 
 nuclei are often branched ; the intima 
 is distinctly striated, from the presence 
 of pore-canals. The glands arise as 
 evaginations of the pharynx (ectoder- 
 mal ) and the chitinous intima of each 
 gland is cast at each moult, along with 
 the general integument. 
 
 The silk glands of Trichoptera are essentially like those of 
 Lepidoptera, but the glands of Chrysopa, Mynneleon, Coc- 
 cinellidce, Chrysomelid?e and Syrphid?e, which open into the 
 rectum, are morphologically quite different from those of 
 Lepidoptera. 
 
 3. Muscular System 
 
 The number of muscles possessed by an insect is surpris- 
 ingly large. A caterpillar, for example, has about two 
 thousand. 
 
 Sections of silk gland of 
 the silk worm. A, radial; 
 B, transverse, h, basement 
 membrane; i, intima; s, 
 glandular cell with branched 
 nucleus. — After Helm. 
 
86 
 
 ENTOMOLOGY 
 
 The muscles of the trunk are segmentally arranged — most 
 evidently so in the body of a larva or the abdomen of an 
 imago, where the musculature is essentially the same in sev- 
 eral successive segments. In the thoracic segments of an ima- 
 go, however, the musculature is, at first sight, unlike that of 
 
 Fig. io8. 
 
 Muscles of cockroach; of ventral, dorsal and lateral walls, respectively, a, alary 
 muscle; ahc, abductor of coxa; adc, adductor of coxa; ef, extensor of femur; h, head 
 muscles; Is, longitudinal sternal; It, longitudinal tergal; Ith, lateral thoracic; os, 
 oblique sternal; ot, oblique tergal; ts, tergo-sternal; ts^, first tergo-sternal. — After 
 MiALL and Denny. 
 
 the abdomen, and in the head it is decidedly different ; though 
 future studies will doubtless show that the thoracic and cepha- 
 lic kinds of musculature are only modifications of the simpler 
 abdominal type — modifications brought about in relation to 
 the needs of the legs, wings, mouth parts, antenncT and other 
 movable structures. 
 
 The muscular system has been generally neglectetl by stu- 
 dents of insect anatomy ; the only comprehensive studies upon 
 the subject being those of Straus-Diirckheim (1828) on the 
 beetle Melolontha; Lyonet (1762), Newport (1834) and 
 Lubbock (1859) on caterpillars; and the more recent studies 
 of Lubbock and Janet on Hymenoptera. 
 
ANATOMY AND PHYSIOLOGY 
 
 87 
 
 
 scle fiber of 
 an insect. 
 
 The more important muscles in the body of a cockroach are 
 represented in l'"ii;s. 106-108, from Miall and Denny. The 
 longitudinal stcrnals with the longitudinal tcrgals act to tele- 
 scope the abdominal see-ments ; the oblique , 
 
 i '^ -' ] K 109 
 
 stcrnals l)en(l the alxlomen laterall}- ; the 
 tcrgo-stcrnals, or \ertical expiratory mus- 
 cles, draw the tergum and sternum to- 
 gether. The muscles of the legs and the 
 wings have already been referred to. 
 
 Structure of Muscles. — The muscles 
 of insects differ greatly in form and are 
 inserted frequently by means of chitinous 
 tendons. A muscle is a bundle of long- 
 fibers, each of which has an outer elastic striated 
 membrane, or sarcolcninta, within which 
 are several nuclei ; thus the fiber represents several cells, 
 wdiich have become confluent. With rare exceptions (" alary " 
 muscles and possibly a few thoracic muscles) the muscle 
 
 fibers of an insect present 
 j^l a striated appearance, owing 
 to alternate light and dark 
 bands (Fig. 109), the for- 
 mer being singly refracting, 
 or isotropic, and the latter 
 doubly refracting, or aniso- 
 tropic. 
 
 The minute structure of 
 these fibers, being extremely 
 
 Minute structure of a striated muscle difflCUlt of interpretation, 
 
 fiber. A, longitudinal section; B, trans- . . 
 
 verse section in the region of /; C. trans- haS glVCU nSC tO UlUCh dlf- 
 
 yerse section in the region of n. /, fej-gj^^^ ^f OpiuioU. The 
 
 longitudinal fibrillse; n, Krause s mem- ^ 
 
 brane; nl, nucleus; r, radial fibrills; 3, moSt plaUSiblc vicW is that 
 
 sarcolemma. — After Janet. , r^ : i ^ t i. 
 
 of van Ciehuchten, Janet 
 and others, who hold that both kinds of dark bands ( h'ig 
 no) consist of highly elastic threads of spongioplasni (aniso- 
 tropic) embedded in a matrix of clear, semi-fluid, nutritive 
 
 Fig. no. 
 
ENTOMOLOGY 
 
 hyaloplasm (isotropic). The spongioplasmic threads of the 
 long- bands extend longitudinally and those of the short bands 
 {" Krause's membrane") radially, in respect to the form of 
 the fiber. Moreover, the attenuated extremities of the longi- 
 tudinal fibrillse connect with the radial fibrillje, the points of 
 connection being marked by slight thickenings, or nodes, 
 which go to make up Krause's membrane. 
 
 Under nervous stimulus a muscle shortens and thickens 
 because its component fibers do, and this in turn is attributed 
 to the shortening and thickening of the longitudinal fibrillje. 
 When the stimulus ceases, the radial fibrillse, by their elas- 
 ticity, possibly pull the longitudinal ones back into place. The 
 last word has not been said, however, upon this perplexing 
 subject. 
 
 Muscular Power. — The muscular exploits of insects appear 
 to be marvellous beside those of larger animals, though they 
 are often exaggerated in popular writings. The weakest in- 
 sects, according to Plateau, can pull five times their own 
 weight and the average insect, over twenty times its weight, 
 while Donacia (Chrysomelidje) can pull 42.7 times its weight. 
 As contrasted with these feats, a man can pull in the same 
 fashion but .86 of his weight and a horse from .5 to .83. How 
 are these dififerences explained? 
 
 It is incorrect to say that the muscles of insects are stronger 
 than those of vertebrates, for, as a matter of fact, the contrac- 
 tile force of a vertebrate muscle is greater than that of an 
 insect muscle, other things being equal. The apparently 
 greater strength of an insect in proportion to its weight is 
 accounted for in several ways. The specific gravity of chitih 
 is less than that of bone, though it varies greatly in both sub- 
 stances. Furthermore, the external skeleton permits muscu- 
 lar attachments of the most advantageous kind as compared 
 with the internal skeleton, so that the muscles of insects sur- 
 pass those of vertebrates as regards leverage. These reasons 
 are only of minor importance, however. Small animals in 
 general appear to be stronger than larger animals (allowing 
 
ANATOMY AND PHYSIOLOGY 89 
 
 for the differences in weis^-lit) for tlie same reason tliat a 
 smaller insect has more conspicnons streni^th than a larger 
 one, when the two are similar in everything except weight. 
 \'i)v example: where a bumble bee can pull 16.1 times its own 
 weight, a honey bee can pull 20.2 ; and where the same bumble 
 bee can carry wdiile flying a load 0.63 of its own weight, the 
 honey bee can carry 0.78. Always, as Plateau has shown, the 
 lighter of two insects is the stronger in respect to external 
 manifestations of muscular force — in the ratio of this muscu- 
 lar strength to its own weight. 
 
 To understand this, let us assume that a beetle continues to 
 grow (as never happens, of course). As its weight is increas- 
 ing so is its strength — but not in the same proportion. For 
 while the weight — say that of a muscle — increases as the cube 
 of a single dimension, the strength of the muscle (depending 
 solely upon the area of its cross section) is increasing only as 
 the square of one dimension — its diameter. Therefore the 
 increase in strength lags behind that of weight more and 
 more; consequently more and more strength is required sim- 
 ply to move the insect itself, and less and less surplus strength 
 remains for carrying additional weight. Thus the larger in- 
 sect is apparently the weaker, though it is actually the 
 stronger, in that its total muscular force is greater. 
 
 The writer uses this explanation to account also for the 
 inability of certain large beetles and other insects to use their 
 wings, though these organs are well developed. Increasing 
 w^eight (due to a larger supply of reserve food accumulated 
 bv the larva) has made such demands upon the muscular 
 power that insufficient strength remains for the purpose of 
 flight. 
 
 Statements such as this are often seen — a flea can jump a 
 meter, or six hundred times its own length. Almost needless 
 to say, the length of the body is no criterion of the muscular 
 power of an animal. 
 
 4. Nervous System 
 The central nerx'ous system extends along the median line 
 of the floor of the body as a series of ganglia connected by 
 
90 
 
 ENTOMOLOGY 
 
 b-W 
 
 nerve cords. Typically, there is a gan- 
 glion (double in origin) for each primary 
 
 qI segment, and the connecting cords, or 
 
 , coiiuiiissiircs, are paired; these conditions 
 
 are most nearly realized in embryos and 
 
 I in the most generalized insects — Thysa- 
 
 "'^^ nura ( Fig. 1 1 1 ) . In all adult insects, 
 however, the originally separate ganglia 
 consolidate more or less (Fig. 112) and 
 
 r the commissures frequently unite to 
 
 form single cords. Thus in Tabainis 
 
 ^^ ( 1' ig- II-. C) the three thoracic gan- 
 glia have united into a single com- 
 
 flf poi^^i'it^l ganglion and the abc^ominal gan- 
 glia are concentrated in the anterior 
 part of the abdomen ; in the grasshop- 
 per, the ner\-e cord, double in the tho- 
 rax, is single in the abdomen. Various 
 other modifications of the same nature 
 occur. 
 
 Cephalic Ganglia. — In the head the 
 primitive ganglia always unite to form 
 two compound ganglia, namely the 
 brain and the subccsophagcal ganglion 
 ( disregarding a few anomalous cases 
 in which the latter is said to be 
 absent). 
 
 The brain, or suprao'sophagcal gan- 
 glion (Fig. 113), is formed by the union 
 of three primitive ganglia, or ncurouicrcs 
 
 (Fig. 55), namely, (T) the protoccrc- 
 
 bruni, which gives off the pair of optic 
 nerves; (2) the dcntoccrcbnini, which 
 
 Central nervous system 
 
 of a thysanuran, Machilis. nerve; b, brain; c, compound eye; /, labial nerve; m, 
 
 The thoracic and abdom- mandibular nerve; mx, maxillary nerve; o, cesophagus; 
 
 inal ganglia are numbered ol, optic lobe; s, suboesophageal ganglion; sy, sympathetic 
 
 in succession, a, antennal nerve.— After Oudemans. 
 
ANATOMY AND PHYSIOLOGY 
 
 91 
 
 innervates the antenn:c; and (3) the Irilocmivuin , which in 
 Apterygota hears a pair of ni(hmentar_\' a])pen(la<;es that are 
 reg-arded as traces of a second i)air of antenna\ 
 
 Successive stages in the concentration of tlie central nervous system of Diptera. A, 
 Cliirowiniis ; B, Enipis; C, Tabmiiis; D, Sarcophaga. — After Br,\ndt. 
 
 Fk;. 113. 
 
 Nervous system of the head of a cockroach, a, antennal nerve; ag, anterior lateral' 
 ganglion of sympathetic system; b, brain; d, salivary duct; /, frontal ganglion; h, hypo- 
 pharynx; /, labrum; ii, labium; m, mandibular nerve; mx, maxillary nerve; n!, nerve to 
 labrum; >i/t, nerve to labium; o, optic nerve; of, oesophageal commissure; o<?, CBsophagus; 
 pg, posterior lateral ganglion of sympathetic system; r, recurrent nerve of sympa- 
 thetic system; s, suboesophageal ganglion. — After Hofer. 
 
 The suboesophageal ganghon (Fig. 113) is ahvays con- 
 nected with the brain l)y a pair of nerve cords {wsopliagcal 
 
92 
 
 ENTOMOLOGY 
 
 coiiunissurcs) between which the fESophagus passes. This 
 
 compound ganglion represents at most four neuromeres : ( i ) 
 
 mandihnlav, innervating the mandibles; (2) snpcvUngual, 
 
 found by the author in Collembola, 
 
 l-IG. 114. 
 
 but not yet reported in the less gen- 
 eralized insects; (3) maxillary, inner- 
 ^^^_^^ vating the maxilke ; (4) labial, which 
 
 <:5nj( Y yi^ sends a pair of nerves to the labium. 
 
 ^~-J -^"^^^■"^'^ Ur, The minute structure of the brain, 
 
 though highly complex, has received 
 considerable study, but will not be 
 described here for the reason that the 
 anatomical facts are of no general 
 interest so long as their physiological 
 interpretation remains obscure. 
 
 Sympathetic System. — ^ L y i n g 
 along the median dorsal line of the 
 oesophagus is a recurrent, or stoma to- 
 gastric, nerve (Fig. 114), which 
 arises anteriorly in a frontal gan- 
 glion and terminates posteriorly in 
 a stomachic ganglion situated at 
 the anterior end of the mid intes- 
 tine. Connected with the recurrent 
 nerve are two pairs of lateral ganglia, 
 the anterior of which innervate the 
 dorsal vessel and the posterior, the 
 tracheae of the head. The ^'entral 
 nerve cord may include also a median 
 nerve thread (Fig. 11 1) which gives 
 off paired transverse nerves to the 
 muscles of the spiracles. 
 Structure of Ganglia and Nerves. — A ganglion consists 
 of (i) a dense cortex, composed of ganglion cells (Fig. 115), 
 each of which has a large rounded nucleus and gives off usu- 
 ally a single nerve fiber; and (2) a clear medullary portion 
 
 Sympathetic nervous system 
 of an insect, diagrammatically 
 represented. a, antenna! 
 nerve; b, brain; f, frontal 
 ganglion; /, /, paired lateral 
 ganglia; m, nerves to upper 
 mouth parts; o, optic nerve; 
 r, recurrent nerve; s, nerve to 
 salivary glands; st, stomachic 
 ganglion. — After Kolbe. 
 
ANATOMY AND PHYSIOLOGY 
 
 93 
 
 (Piiiiktsubsfaii::;) derived from the processes of the cortical 
 ganghon ceHs and serving as the place of origin of nerve fihril- 
 lae. There are, however, ganglion cells from which processes 
 may pass directly into nerve fibrilhc. 
 
 A ncr\c, in an insect, consists of an a.vis-cyltiidcr, composed 
 of hhrilla-, and an enveloping membrane, or uriirilriniiia. The 
 axis-c\lin(ler is the transmitlinsj" i)ortion and the ij'.'nii'iia are 
 
 Fig. 
 
 Transverse section of an abdominal ganglion of a caterpillar, a, axis-cylinder; g, 
 ganglion cells; n, nenrilennna; p, Punktsubstanz. 
 
 the trophic centers, i. e., they regulate nutrition. A nerve is 
 always either sensory, transmitting impulses inward from a 
 sense organ; or else motor, conveying- stimuli from the central 
 nervous system outward to muscles, glands, or other organs. 
 
 Functions. — The brain innervates the chief sensory organs 
 (eyes and antennae) and converts the sensory stimuli that it 
 receives into motor stimuli, which effect co-ordinated muscular 
 or other movements in response to particular sensations from 
 the en\'ironment. The brain is the seat of the will, using the 
 term " will " in a loose sense; it directs locomotor mo^'ements 
 of the legs and wings. An insect deprived of its brain cannot 
 go to its food, though it is able to eat if food be placed in con- 
 tact with the end-organs of taste, as those of the palpi ; further- 
 more, it walks or flies in an erratic manner, indicating a lack 
 of co-ordination of nuiscular action. 
 
 The suboesophageal ganglion controls the mouth parts, co- 
 ordinating their movements as well as some of the bodily 
 movements. 
 
94 ENTOMOLOGY 
 
 The thoracic gangHa govern the appendages of their respec- 
 tive segments. These gangha and those of the abdomen are 
 to a great extent independent of brain control, each of these 
 gangha being an individual motor center for its particular 
 segment. Thus decapitated insects are still able to breathe, 
 walk or fly, and often retain for several days some power of 
 movement. 
 
 In regard to the sympathetic system, it has been shown ex- 
 perimentally that the frontal ganglion controls the swallowing 
 mo\'ements and exerts through the stomatogastric nerve a 
 regulative action upon digestion. The dorsal sympathetic sys- 
 tem controls the dorsal vessel and the salivary glands, while 
 the ventral sympathetic system is concerned with the spiracu- 
 lar muscles. 
 
 5. Sense Organs 
 
 For the reception of sensory impressions from the external 
 world, the armor-like intesrument of insects is modified in a 
 
 another may occur on almost any part of an insect, they are 
 most numerous and varied upon the head and its appendages, 
 particularly the antennae. 
 
 Antennal Sensilla. — Some idea of the diversity of form 
 in antennal sense organs may be obtained from Figs. 1 16-125, 
 taken from a recent paper by Schenk. whose useful classifica- 
 tion of antennal scusilla, or sense organs, is here outlined : 
 
 1. Scusilluin caloconicuin — a conical or peg-like projection 
 immersed in a pit (Figs. 116-117). In all probability 
 olfactory. 
 
 2. ^. hasiconicuin — a cone projecting above the general sur- 
 face (Fig. 118). Probably olfactory. 
 
 3. 5^. styloconicum — a terminal tooth or peg seated upon a 
 more or less conical base (Fig. 119). Olfactory. 
 
 4. 6^. cliccticuni — a bristle-like sense organ (Fig. 120). 
 Tactile. 
 
 5. 6^. tvichodcum — a hair-like sense organ (Figs. 121, 122). 
 Tactile. 
 
ANATOMY AND PHYSIOLOGY 
 
 95 
 
 6. 5. placodcuni — a membranous plate, its outer siu'face 
 continuous with the g-eneral integument ( h'ig. 123). h\inc- 
 
 FiGs. 1 16-125. 
 
 Types of antennal sensilla, in longitudinal section (excepting Figs. 119 and 120). 
 Fig. 116, sensillum cotloconicum; 117, cceloconicum; 118, basiconicum; 119, stylo- 
 conicum; 120, chseticum; 121, trichodeum; 122, trichodeum; 123, placodeum; 124, 
 ampullaceum; 125, ampullaceum; c, cuticula; h, hypodermis; n, nerve; s, sensory cell. 
 Figs. 116, 118, 121, 123, 124, honey bee, Apis mellifera; 117, 119, 122, moth, FiJonia 
 piniaria; 120, moth, Ino pruni; 125, wasp, Vespa crabro. — After Schenk. 
 
96 ENTOMOLOGY 
 
 tion doubtful ; not auditory and probably not olfactory, though 
 the function is doubtless a mechanical one; Schenk suggests 
 that they are affected by air pressure, as when a bee or wasp 
 is moving about in a confined space. 
 
 7. 5. ampiiUaccnm — a more or less flask-shaped cavity with 
 an axial rod (Figs. 124, 125). Probably auditory. 
 
 These types of sensilla will be referred to in physiological 
 order. 
 
 Touch. — The tactile sense is highly developed in insects, 
 and end-organs of touch, unlike those of other senses, are com- 
 monly distributed over the entire integument, though the an- 
 tenucC, palpi and cerci are especially sensitive to tactile impres- 
 sions. 
 
 The end-organs of touch are bristles (sensilla ch^etica) or 
 hairs (sensilla trichodea), each arising from a special hypo- 
 dermis cell and having connection with a nerve. Sensilla 
 ch?etica doubtless receive impressions from foreign bodies, 
 while sensilla trichodea, being best developed in the swiftest 
 flying insects and least so in the sedentary forms, may be 
 affected by the resistance of the air, when the insect or the air 
 itself is in motion. 
 
 Not all the hairs of an insect are sensory, however, for many 
 of them have no nerve connections. 
 
 In blind cave insects the antennre are very long and are ex- 
 quisitely sensitive to tactile impressions. 
 
 Taste. — The gustatory sense is unquestionably present in 
 insects, as is shown both by common observation and by pre- 
 cise experimentation. \\\\\ fed wasps with sugar and then 
 replaced it with powdered alum, which the wasps unsuspect- 
 ingly tried but soon rejected, cleaning the tongue with the 
 fore feet in a comical manner and manifesting other signs of 
 what we may call disgust. Forel offered ants honey mixed 
 with morphine or strychnine; the ants began to feed but at 
 once rejected the mixture. In its range, however, the gusta- 
 tory sense of insects differs often from that of man. Thus 
 \\\\\ found that Hymenoptera refused honey with which a 
 
ANATOMY AND PHYSIOLOGY 
 
 97 
 
 very little glycerine had been mixed (thoug-h Muscidrc did not 
 object to the glycerine) and Forel found that ants ate iinsus- 
 
 Section through tongue of wasp, I'cspa ml 
 hypodermis; n, nerve; ob, gustatory bristle; pli 
 tactile bristle.— After Will. 
 
 'i^. c, ciiticula 
 rotecting hair; 
 
 gland cell; li, 
 sensory cell; tb, 
 
 Fig. i; 
 
 pectingiy a mixture of honey and phosphorus until some of 
 them were killed by it. Under the same circumstances, man 
 would be able to detect the phosphorus 
 but not the glycerine. 
 
 Location of Gustatory Organs. — As 
 would be expected, the end-organs of 
 taste are situated near the mouth, com- 
 monly on the hypopharynx (Fig. 126), 
 epipharynx and maxillary palpi. On the 
 tongue of the honey bee the taste organs 
 appear externally as short setse (Fig. 
 127) and on the maxillae of a wasp as 
 pits, each with a cone, or peg, projecting 
 from its base (Figs. 128, 129). Similar 
 taste pits and pegs have been found by 
 Packard on the epipharynx in most of the 
 mandibulate orders of insects. 
 Histology- — The end-organs of taste arise from special 
 hypodermis cells, as minute setae or, more commonly, pegs. 
 
 Tongue of honey bee, 
 Apis mellifera. p, pro- 
 tecting bristles; s, ter- 
 minal spoon; t, taste 
 setae. — After Will. 
 
98 
 
 ENTOMOLOGY 
 
 Fig. 128. 
 
 ..-tc 
 
 —tk 
 
 each seated in a pit, or cup, and connected with a nerve fiber 
 (Figs. 129, 130). In some cases, however, it is difficult to 
 
 decide whether a given organ 
 is gustatory or olfactory, owing 
 to the similarity between these 
 two kinds of structures. In 
 aquatic insects, indeed, the 
 senses of taste and smell are not 
 differentiated, these forms hav- 
 ing with other of the lower 
 animals simply a " chemical " 
 sense. 
 
 Smell. — In most insects the 
 sense of smell is highly efficient 
 and in many species it is incon- 
 ceivably acute. Hosts of in- 
 sects depend chiefly on their 
 olfactory powers to find food, 
 for example many beetles, the 
 flesh flies and the flower-visit- 
 
 Under side of left maxilla of 
 
 wasp, Vespa zndgaris. p, palpus; pr, 
 
 protecting hairs; tc, taste cup; th, 
 tactile hair. — After Will. 
 
 the opposite sex, as is notably 
 the case in saturniid moths. 
 
 In dragon flies, however, this 
 sense is relied upon far less 
 than that of sight. 
 
 Organs of Smell. — By 
 means of simple but conclu- 
 sive experiments, Hauser and 
 others have shown that the 
 antennae are frequently olfac- 
 tory — though not to the ex- 
 clusion of tactile or auditory 
 functions, of course. Hauser 
 found that ants, wasps, vari- 
 ous flies, moths, beetles and 
 larvse, which react violently toward the vapor of turpen- 
 
 Longitudinal section of gustatory 
 end-organ {tc, of Fig. 128). c, cutic- 
 ula; h, hypodermis; sc, sensory cell; 
 tc, taste cup. — After Will. 
 
ANATOMY AND PHYSIOLOGY 
 
 99 
 
 tine, acetic acid and other pnngent fluids, no longer re- 
 spond to the same stimuli after their antenna' have been 
 amputated or else covered with paraftine to exclude the 
 air. His experiments were conducted under conditions 
 such that the results could not be ascribed to the shock 
 
 Fir;. T30. 
 
 Taste cup 
 
 from maxilla 
 
 of Bombus. 
 
 sc, sensory 
 
 cell; n, nerve. 
 
 —After Will. 
 
 Section of antennal olfac- 
 tory organ of grasshopper, 
 Caloptcniis. c, cuticula; m, 
 membrane; n, nucleus of 
 sensory cell; nv, nerve; p, 
 pit with olfactory peg; pg, 
 pigment. — After Hauser. 
 
 of the operation or to effects upon the gustatory or res- 
 piratory systems ; except for having lost the sense of smell, 
 the insects experimented upon behaved in a normal manner. It 
 should be said, however, that Carahus, Mclolontlia and Silpha 
 still reacted to some extent toward strong vapors even after the 
 extirpation of the antennae ; while in Hemiptera the loss of the 
 antennas did not lessen the response to the odors used. These 
 facts indicate that the sense of smell is not always confined to 
 the antennae ; indeed the maxillary palpi are frequently olfac- 
 tory, as in Silpha and Hydoticus; also the cerci, as in the cock- 
 roach and other Orthoptera. Experiments indicate that an 
 
lOO 
 
 ENTOMOLOGY 
 
 insect perceives 
 
 Fig. 132. 
 
 Section through antennal olfactory 
 pit of fly, Tabaiius. c, cuticula; p, 
 pit with peg; pb, protecting bristles; 
 s, sensory cell. — After H.'iUSEr. 
 
 some odors by means of the antenna and 
 others by the palpi or other 
 organs. Hauser found that 
 the flies Sarcophaga and Cal- 
 liphora, after the amputation 
 of their antennae, became 
 quite indifferent toward de- 
 cayed meat, to which they 
 had previously swarmed with 
 great persistence, though 
 their actions in all other re- 
 spects remained normal. 
 ]\Iales of many moths and a 
 few beetles are unable to find 
 
 Fig. 133- 
 
 cn 
 
 the females (see beyond) when the for- 
 mer are deprived of the use of their 
 antennae. 
 
 End-Organs. — Structures which are 
 regarded as olfactory end-organs occur 
 commonly on the antennje. often on the 
 maxillary and labial palpi and sometimes 
 on the cerci. These end-organs are hy- 
 podermal in origin and consist, generally 
 speaking, of a multinucleate cell (Fig. 
 131) penetrated by a nerve and prolonged 
 into a chitinous bristle or peg, which is 
 more or less enclosed in a pit, as in Ta- 
 baniis (Fig. 132). In many instances, 
 however, the end-organs take the form of 
 teeth or cones projecting from the gen- 
 eral surface of the antenna, as in J^cspa 
 (Fig. 133). These cones are usually less 
 numerous than the pits; in J\^spa crabro, 
 for example, the teeth number 700 and 
 the pits from 13.000 to 14.000 on each 
 antenna. The pits are even more numerous in some other 
 
 Longitudinal section 
 of antennal olfactory 
 organ of wasp, Vespa. 
 c, olfactory cell; cn, ol- 
 factory cone; ct, cutic- 
 ula; h, hypodermis cells; 
 n, nerve; r, rod. — After 
 Hauser. 
 
ANATOMY AND PHYSIOLOGY 
 
 insects ; tlins there are as 
 many as 17.000 on each an- 
 tenna of a l)l<)\v fly (Hicks). 
 The male of Mclolontha vul- 
 garis, which seeks ont the 
 female hy the sense of smell, 
 has according- to Hauser 39,- 
 000 pits on each antenna, and 
 
 Fig. 134. 
 
 the female onl\- :5s. 000. 
 
 Pit^ 
 
 presumahly olfactory in fnnc- 
 tion ha\e l)een fonnd hy 
 Packard on the maxillary and 
 lahial palpi of Pcrla and on 
 the cerci of the cockroach 
 Pcriplancta aincvicana. Vom 
 
 Longitudinal section of a portion of a 
 
 caudal appendage of a cricket, Grylliis 
 
 domesticus. b, bladder-like hair; c, cutic- 
 
 ula; /;, hypodermis; n, nerve; ns, non- 
 
 Rath has deSCrihed four kinds sensory sets; sc, sense cell; sh, sensory 
 
 hair 
 
 .\fter voM Rath. 
 
 Fi'-- 135- 
 
 of sense hairs from the two 
 
 larger of the four caudal appen- 
 dages of a cricket. Gryllus; some 
 of these (Fig. 134) may be olfac- 
 tory, though possibly tactile. The 
 same author found on the terminal 
 palpal segment in various Lepidop- 
 tera a large flask-shaped invagina- 
 tion (Fig. 135) into wdiich pro- 
 ject numerous chitinous rods, each 
 a process of a sensory cell, which 
 is supplied by a branch of the prin- 
 cipal palpal nerve ; these peculiar 
 organs are inferred to be olfactory. 
 The chief reason for regard- 
 ing these various end-organs as 
 olfactory is that they appear 
 Longitudinal section of ape.x of ^^om their structurc to he better 
 
 palpus of Pieris. c, cuticuia; h, adapted to rcccivc that kind of 
 
 hypodermis; n, nerve; s, scales; ... 
 
 sc, sense ceiis.-After vom Rath, ^i" impressioii than any Other, SO 
 
I02 ENTOMOLOGY 
 
 far as we can judge from our own experience. Though it is 
 easy to demonstrate that the antennae, for example, are olfac- 
 tory, it frequently happens that the antennae bear several dis- 
 tinct forms of sensory end-organs, so minute and intermingled 
 that their physiological differences can scarcely be ascertained 
 by experiment but must be inferred from their peculiarities of 
 structure. Schenk, however, has arrived at precise results 
 by comparing the antennal sensilla in the two sexes, selecting 
 species in which the antennae exhibit a pronounced sexual 
 dimorphism, in correlation with sexual differences of behavior. 
 Taking NotolopJius (Orgyia) antiqua, in which the male seeks 
 out the female by means of antennal organs of smell, he finds 
 that the male has on each antenna about 600 sensilla coelo- 
 conica and the female only 75 ; similarly in the geometrid Fido- 
 7iia, in which the ratio is 350 to 100. The sensilla styloconica, 
 also, of these two genera are regarded as olfactory organs. 
 These two kinds of end-organs are not only structurally adapted 
 for the reception of olfactory stimuli, but their numerical dif- 
 ferences accord with the observed differences in the olfactory 
 powers of the two sexes, there being no other antennal end- 
 organs to enter into the consideration. 
 
 Assembling. — It is a fact, well known to entomologists, 
 that the females of many moths and some beetles are able by 
 exhaling an odor to attract the opposite sex, often in consid- 
 erable numbers. Under favorable conditions, a freshly 
 emerged female of the promcthca moth, exposed out of doors 
 in the latter part of the afternoon, will attract scores of the 
 males. A breeze is essential and the males come up against 
 the wind; if they pass the female, they turn back and try again 
 until she is located, vibrating the antennae rapidly as they near 
 her. The female, meanwhile, exhales an appreciable odor, 
 chiefly from the region of the ovipositor, and males will con- 
 gregate on the ground at a spot where a female has been. If 
 one of these males is deprived of the use of his antennae, how- 
 ever, he flutters about in an aimless way and is no longer able 
 to find the female. 
 
ANATOMY AND PHYSIOLOGY IO3 
 
 Among- beetles, males of Polyphylla gather and scratch at 
 places where females are about to emerge from the ground. 
 Prionus also assembles, as Mrs. Dimmock observed in Massa- 
 chusetts. In this instance many males, with palpitating an- 
 tennae, ran and flew to the female; moreover, a number of 
 females were attracted to the scene. 
 
 Sounds of Insects. — Before considering the sense of hear- 
 ing, some account of the sounds of insects is desirable. Most 
 of these are made by the vibrations of a membrane or by the 
 friction of one part against another. 
 
 The wings of many Diptera and Hymenoptera vibrate with 
 sufficient speed and regularity to give a definite note. The 
 wing tone of a honey bee is A' and that of a common house 
 fly is F'. From the pitch the number of vibrations may be 
 determined; thus A' means 440^ vibrations per second and 
 F', 352. The numbers thus ascertained may be verified by 
 Marey's graphic method (Fig. 74) ; he found that the fly 
 referred to actually made 330 strokes per second against the 
 smoked surface of a revolving cylinder. 
 
 Flies, bees, dragon flies and some beetles make buzzing or 
 humming sounds by means of the spiracles, there being behind 
 each spiracle a membrane or chitinous projection wdiich vi- 
 brates during respiration. This " voice " should be distin- 
 guished from the wing tone when both are present, as in bees 
 and flies. A fly will buzz when held by the wings, and some 
 gnats continue to buzz aft'er losing wings, legs and head. 
 The wing tone is the more constant of the two ; in the honey 
 ])ee it is A', falling to E' if the insect is tired, while the spirac- 
 ular tone of the same insect is at least an octave higher (A") 
 and often rises to B" or C" , according to the state of the ner- 
 vous system ; in fact, it is possible and even probable that vari- 
 ous spiracular tones express different emotions, as is indicated 
 by the effects produced by the voice of the old queen bee upon 
 the young queens and the males. 
 
 ' Upon tlie basis of C as 264 vibrations per second. The C of the 
 physicist has 256 as its frequency of vibration. 
 
I04 . ENTOMOLOGY 
 
 The well-known " shrilling " of the male cicada is produced 
 by the rapid vibration of a pair of membranes, or drums, sit- 
 uated on the basal abdominal segment, and vibrated each by- 
 means of a special muscle. 
 
 Frictional sounds are made by beetles in a great variety of 
 ways : by the rubbing of the pronotum against the mesonotum 
 (many Cerambycidse) ; or of abdominal ridges against elytral 
 rasps {Elaphrns, Cychnis) ; or two dorsal abdominal rasps 
 against specialized portions of the wing folds (Passahis cor- 
 nutus) , not to mention other methods. In most cases one 
 part forms a rasp and the other a scraper, for the production 
 of sound. 
 
 In many of these instances the sound serves to bring the 
 two sexes together and is not necessarily confined to one sex; 
 thus, in Passahis corn lit us both sexes stridulate. 
 
 A few moths (Sphingidse) and a few butterflies make 
 sounds ; the South American butterfly Agcronia feronia emits 
 a sharp crackling noise as it flies. A rasp and a scraper have 
 been found in several ants, though ants very seldom make any 
 sounds that can be distinguished by the human ear; Mutilla, 
 however, makes a distinct squeaking sound by means of a 
 stridulating organ similar to those of ants. 
 
 Stridulating organs attain their best development in Orthop- 
 tera, in which group the ability to stridulate is often restricted 
 to the male, though not so often as is commonly supposed. 
 Among Acridiidse, Stenobotliriis rubs the hind femora against 
 the tegmina to make a sound, the femur bearing a series of 
 teeth, which scrape across the elevated veins of the wing-cover; 
 while the male of Dissosteira makes a crackling sound during 
 flight or while poising, by means of friction between the front 
 and hind wings, where the two overlap. 
 
 Locustidae and Gryllidse stridulate by rubbing the bases of 
 the tegmina against each other. Thus in the male Microcen- 
 trum laurifoliiim the left tegmen, which overlaps the right, 
 bears a file-like organ of about fifty-five teeth (Fig. 136), while 
 the opposite tegmen bears a scraper, at right angles to the file. 
 
ANATOMY AND PHYSIOLOGY 
 
 105 
 
 The teg:mina are first spread a little: then, as they close gTadu- 
 ally, the scraper clicks across the teeth, makino- from twenty to 
 thirty sharp " tic "-like sounds in rapid succession. This call 
 guides the female to the male and when they are a few inches 
 apart she makes now and then a short, soft chirp, to which he 
 responds Avith a similar chirp, which is quite unlike the first 
 
 Fig. 136. 
 
 Stridulating organs of Microccntrum laurifolium. A, dorsal aspect of file {st) 
 when the tegmina are closed; B, ventral aspect of left tegmen to show Hie; C, dorsal 
 aspect of right tegmen to show scraper (s). 
 
 call and, moreover, is made by the opening of the tegmina. 
 These and other details of the courtship may readily be ob- 
 served in twilight and even under artificial light, as the latter, 
 if not too strong, does not disturb the pair. Something sim- 
 ilar may be observed in the daytime in Orclielimum, Xiphidiiim 
 and the tree crickets, GEcanthiis. The stridulating areas are 
 usually membranous and the rasping organs are modified veins. 
 
I06 ENTOMOLOGY 
 
 Frequently the wing-covers bulge out to form a resonant cham- 
 ber that reinforces the sound. 
 
 The naturalist can recognize many a species of grasshopper 
 by its song; Scudder has expressed some of these songs in 
 musical notation. The usual song of the common meadow- 
 grasshopper, OrclieUniuvi vulgare, may be represented by a 
 prolonged .cr . . . sound, followed by a staccato jip-jip-jip- 
 jip. ... 
 
 In Orthoptera, the frequency of stridulation increases with 
 the temperature; and the correlation between the two is so 
 close that it is easy to compute the temperature from the num- 
 ber of calls per minute, by means of formulae. The formula 
 for a common cricket [probably a species of Gryllits] , as given 
 by Professor Dolbear, is 
 
 ^ N-40 
 
 T= 50 -h — - -. 
 4 
 
 Here T stands for temperature and A^, the rate per minute. 
 
 A similar formula for the katydid {Cyrtophyllus perspicil- 
 
 latus), based upon observations made by R. Hayward, would 
 
 be 
 
 T=6o-\- -. 
 
 Here, in computing A^, either the " katy-did " or the " she- 
 did " is taken as a single call. 
 
 Hearing. — There is no doubt that insects can hear. The 
 presence of sound-making organs is strong presumptive evi- 
 dence that the sense of hearing is present. Female grass- 
 hoppers and beetles make locomotor and other responses to 
 the sounds of the males, and male grasshoppers will answer 
 the counterfeit chirping made with a quill and a file. 
 
 Auditory organs are not restricted to any one region of an 
 insect, but occur, according to the species, on antennae, abdo- 
 men, legs or elsewhere. 
 
 The antennae of some insects are evidently stimulated by 
 certain notes, particularly those made by their own kind. 
 Thus the antennae of the male mosquito are auditory, as 
 
ANATOMY AND PHYSIOLOGY 
 
 107 
 
 proved by the well-known experiments of Mayer. He fastened 
 a male Culcx to a microscope slide and sounded various tuning 
 forks. Certain tones caused certain of the antennal hairs to 
 vibrate sympathetically, and the greatest amount of vibration 
 occurred in response to 512 vibrations per second, or the note 
 C" , which is approximately the note upon which the female 
 hums. The male probably turns his head until the two an- 
 tennae are equally affected l)y the note of the female, when, by 
 
 Fig. 137. 
 
 S" — d 
 
 Inner aspect of right tympanal sense organ of a grasshopper, Caloptenus itallcus. 
 b, chitinous border; c, closing muscle of spiracle; gn, ganglion; m, tympanum; n, 
 nei-ve; o, opening muscle of spiracle; p, p, processes resting against tympanum; s, 
 spiracle; t)ii, tensor muscle of tympanum; z; vesicle. — After Gr.^ber. 
 
 going- Straight ahead, he is able to locate her with great 
 precision. 
 
 In the lack of experimental evidence, other organs are in- 
 ferred to be auditory on account of their structure. Acridiidae 
 bear on each side of the first abdominal segment a tympanal 
 sense organ — the subject of Graber's well-know^n figure (Fig. 
 137). This organ is admirably adapted to receive and trans- 
 mit sound-waves. The tympanum, or membrane, is tense, 
 and can vibrate freely, as the air pressure against the two sur- 
 
io8 
 
 ENTOMOLOGY 
 
 faces of the membrane is equalized by means of an adjacent 
 spiracle, which admits air to the inner surface. Resting 
 against the inner face of the tympanum are two processes 
 (Fig. 137, />, p) , which serve probably to transfer the vibra- 
 tions, and there is also a delicate vesicle connected by means 
 
 of an intervening ganglion 
 ^^' ^^ ■ with the auditory nerve, which 
 
 in this case comes from the 
 metathoracic ganglion. The 
 nerve terminations consist of 
 delicate bristle-like processes 
 which are probably affected by 
 the oscillations of the fluid con- 
 tained in the vesicle just re- 
 ferred to. 
 
 Other tympanal organs, 
 doubtless auditory, are found 
 on the fore tibise of Locustid?e, 
 ants, termites and Perlidse, on 
 the femora of Pediculid?e and 
 the tarsi of some Coleoptera. 
 
 Several types of chordotonal 
 organs have been described, of 
 which those of the transparent 
 Coretlira larva may serve as an 
 example. These organs, situ- 
 ated on each side of abdonlinal 
 segments 4-10, inclusive, con- 
 sist each (Fig. 138) of a tense 
 cord, probably capable of vibra- 
 tion, which is attached at its posterior end to the integument 
 and at its anterior end to a ligament. Between the cord and 
 the supporting ligament is a small ganglion, which receives a 
 nerve from the principal ganglion of the segment. 
 
 Vision. — The external characters of the two kinds of eyes 
 — ocelli and compound eyes — have already been described. 
 
 Chordotonal sense organ of aquatic 
 dipterous larva, Coretlira phimicornis. 
 cd, cord; eg, chordotonal ganglion; /, 
 fibers of an integumental nerve; g, 
 ganglion of ventral chain; /, ligament; 
 m, longitudinal muscles; n, chordotonal 
 nerve; r, rods (nerve terminations); t, 
 tactile setae. — After Graber. 
 
ANATOMY AND PHYSIOLOGY 
 
 109 
 
 While the lateral ocelli are comparatively simple in structure, 
 consisting of a small number of cells, the dorsal ocelli almost 
 rival the compound eyes in complexity. 
 
 Dorsal Ocelli. — These consist (Fig. 139) of (i) lens, (2) 
 ■rilrcoiis body, (3) retina, 
 (4) nerve fibers, (5) pig- 
 mented hypodennis eells, 
 and (6) accessory cells, be- 
 tween the retinal cells and 
 the nerve fibers. The lens, 
 usually biconvex in form, is 
 a local thickening of the 
 general cuticula ; it is sup- 
 plemented in its function by 
 the \-itreous body, consist- 
 ing of a layer of transpar- 
 ent hypodermis cells; these 
 in many insects are elon- 
 gate, constituting a vitreous 
 layer of rather more im- 
 portance than the one rep- 
 resented in Fig. 139. The 
 retina consists of cells more 
 or less spindle-shaped and 
 associated in pairs or in groups of two or three, each group 
 being termed a ret in it la. The basal end of each retinal cell is 
 continuous with a nerve fiber (Fig. 140), according to Redi- 
 korzew and others, and in some instances (Calopteryx) a nerve 
 
 Median ocellus of honey bee, Apis met- 
 lifcra, in sagittal section, h, hypodermis; 
 /, lens; v, nerve; p, iris pigment; r, retinal 
 cells; z; vitreous body. — After Redikorzew. 
 
 or rhabdoin, in the secretion of which all the cells of the retinula 
 are concerned. Between the retinal cells and nerve fibers are 
 indifferent, or accessory cells. Pigment granules, usually black, 
 are contained in these cells, also in the retinal cells and around 
 the lens, in the last instance forming the iris. 
 
 Vision by Ocelli. — Though the ocellus is constructed on 
 
ENTOMOLOGY 
 
 Fig. 140. 
 
 somewhat the same plan as the human eye, its capacity for 
 forming images must l^e extremely limited ; for since the form 
 of the lens is fixed and also the distance between the lens and 
 the retina, there is no power of accommo- 
 dation, and most external objects are out 
 of focus ; to make an image, then, the 
 object must be at one definite distance 
 from the lens, and as the lens is usually 
 strongly convex, this distance must be 
 small ; in other words, insects, like spiders, 
 are very near-sighted, so far as the ocelli 
 are concerned ; furthermore, the small 
 number of retinal rods implies an image of 
 only the coarsest kind. 
 
 If the compound eyes of a grasshopper 
 are covered with an opaque varnish and 
 the insect is placed in a box with only a 
 single opening, it readily finds its way out 
 by means of its ocelli ; if all three ocelli are 
 also covered, however, it no longer does 
 so, except by accident, though it can make 
 its escape when only one of the ocelli is 
 left uncovered. The ocelli, then, can dis- 
 tinguish light from darkness — and they 
 are probably more serviceable to the in- 
 sect in this way than in forming images. 
 Compound Eyes. — As regards deli- 
 cacy and intricacy of structure, the com- 
 pound eye of an insect is scarcely if at all 
 inferior to the eye of a vertebrate. In 
 radial section (Fig. 141), a compound eye 
 appears as an aggregation of similar 
 elongate elements, or ommaiidia, each of which ends exter- 
 nally in a facet. The following structures compose, or are 
 concerned with, each ommatidium : (i) cornea, (2) crystal- 
 line lens, or cone, (3) rhabdom and retinnla, (4) pigment {iris 
 
 ■n 
 
 An ocellar retinula of 
 the honey bee, composed 
 of two retinal cells. A, 
 longitudinal section ; B, 
 transverse section ; ii, n, 
 nerves; p, pigment; r, 
 rhabdom. — After Redi- 
 
 KORZEW. 
 
ANATOMY AND PHYSIOLOGY 
 
 I II 
 
 and retinal'), (5) fenestrate membrane, (6) fibers of the optic 
 nerve, (7) trachece. 
 
 The cornea (Fi.^'. 142) is a l)icon\'ex transparent portion 
 of the external chitincuis cuticiila. Inimechately beneath it are 
 the eone eells, which ma}- contain a 
 clear liuid or else, as in most insects, 
 solid transparent cones. The rhab- 
 dom is a transparent chitinous rod 
 or a group of rods {rhabdomeres) 
 situated in the long axis of the 
 ommatidium and surrounded l:)y 
 greatly elongated cells, which 
 constitute the retinula. T w o 
 zones of pigment are present : an 
 outer zone, of iris pigment, in 
 which the pigment in the form of 
 fine black granules is contained 
 chiefly in short cells that surround 
 the retinula distally ; and an inner 
 zone of retinal pigment, in which 
 the pigment cells are long and 
 slender, and enclose the retinula 
 
 proximally. All these parts are hjgDodermal in origin, as is also 
 the fenestrate basement membrane, through which pass trachese 
 and nerve fibers. The nerve fibrill?e, which are ultimate 
 branches of the optic nerve, pass into the retinal cells — the end- 
 organs of vision. Under the basement membrane is a fibrous 
 optic tract of complex structure. 
 
 Physiology. — After much experimentation and discussion 
 upon the physiology of the compound eye — the subject of the 
 monumental works of Grenacher and Exner — Miiller's " mo- 
 saic " theory is still generally accepted, though it was proposed 
 early in the last century. It is thought that an image is 
 formed by thousands of separate points of light, each of which 
 corresponds to a distinct field of vision in the external world. 
 
 Portion of compound eye of 
 fly, CalUphora roinitoria, radial 
 section, c, cornea; i, iris pig- 
 ment; II, nerve fibers; nc, nerve 
 cells; r, retinal pigment; t, tra- 
 chea. — After HicKSON. 
 
ENTOMOLOGY 
 
 Fig. 14: 
 
 t a 
 
 Structure of an omniatid- 
 ium of Calliphora vomitoria. 
 
 A, radial section (chiefly) ; 
 
 B, transverse section through 
 middle region; C, transverse 
 section through basal region ; 
 hm, basement membrane; c, 
 cornea; n, nucleus; nv, nerve 
 fibrillae; pc, pseudocone; pg^, 
 
 pg'^, cells containing iris pig- 
 ment; p^, cell containing ret- 
 inal pigment; r, one of the six 
 
 Each ommatidium is adapted to trans- 
 mit light along its axis only (Fig. 
 143). as oblique rays are lost by ab- 
 sorption in the black pigment which 
 surrounds the crystalline cone and the 
 axial rhabdom. Along the rhabdom, 
 then, light can reach and affect the 
 terminations of the optic nerve. Each 
 ommatidium does not itself form a 
 picture ; it simply preserves the inten- 
 sity and color of the light from one 
 particular portion of the field of 
 vision ; and when this is done by hun- 
 dreds or thousands of contiguous om- 
 matidia, an image results. All that 
 the painter does, who copies an object, 
 is to put together patches of light in 
 the same relations of quality and posi- 
 tion that he finds in the object itself 
 — and this is essentially what the com- 
 pound eye does, so far as can be in- 
 ferred from its structure. 
 
 Exner, removing the cones with the 
 corneal cuticula (in La/»/>ym), looked 
 through them from behind with the 
 aid of a microscope and found that the 
 images made by the separate omma- 
 tidia were either very close together 
 or else overlapped one another, and 
 that in the latter case the details corre- 
 sponded ; in other words, as many 
 as twenty or thirty ommatidia may co- 
 operate to form an image of the same 
 portion of the field of vision ; this 
 
 retinal cells which compose the retinula; rh, rhab- 
 dom, composed of six rhabdomeres; t, trachea; tv, 
 tracheal vesicle. — After Hickson. 
 
ANATOMY AND PHYSIOLOGY 
 
 113 
 
 " superposition " image being correspondingly bright — an ad- 
 vantage, probably, in the case of nocturnal insects. 
 
 Large convex eyes indicate a wide field of vision, while 
 small numerous facets mean distinctness of vision, as Lubbock 
 has pointed out. The closer the object the better the sight, 
 for the greater will be the number of 
 lenses employed to produce the impres- 
 sion, as Mollock says. If Miiller's 
 theory is true, an image may be formed 
 of an object at any reasonable distance. 
 no power of accommodation being ne- 
 cessary; while if, on the other hand, 
 each cornea with its crystalline cones 
 had to form an image after the manner 
 of an ordinary hand-lens, only objects 
 at a definite distance could be imaged. 
 
 The limit of the perception of form 
 by insects is placed at about two meters 
 for Lampyris, 1.50 meters for Lepi- 
 doptera, 68 cm. for Diptera and 58 cm. 
 for Hymenoptera. 
 
 It is generally agreed, however, tliat 
 the compound eyes are specially adapted 
 to perceive movements of objects. The 
 sensitiveness of insects to even slight 
 movements is a matter of common ob- 
 servation ; often, however, these insects can be picked up with 
 the fingers, if the operation is performed slowly until the insect 
 is within the grasp. A moving object afifects different facets in 
 succession, without necessitating any turning of the eyes or the 
 head, as in vertebrates. Furthermore, on the same principle, 
 the compound eyes are serviceable for the perception of form 
 when the insect itself is moving rapidly. 
 
 The arrangement of the pigment depends adaptively upon 
 the quality of the light, as Stefanowska and Exner have 
 shown ; thus, when the light is too strong, the iris and retinal 
 9 
 
 Diagram of outer, trans- 
 parent portion of an omma- 
 tidium to illustrate the 
 transmission of an axial ray 
 (v4) and the repeated reflec- 
 tion and absorption of an 
 oblique ray (B), which at 
 length emerges at C. p, iris 
 pigment. 
 
I 14 ENTOMOLOGY 
 
 pigment cells elongate around the ommatidium and their pig- 
 ment granules absorb from the cone cells and rhabdom the 
 excess of light. If the light is weak, they shorten, and absorb 
 but a minimum amount of light. 
 
 Origin of Compound Eye. — The compound eye is often 
 said to represent a group of ocelli, chiefly for the reason that 
 externally there appears to be a transition from simple eyes, 
 through agglomerate eyes, to the facetted type. This plausi- 
 ble view, however, is probably incorrect, for these reasons 
 among others. In the ocellus, a single lens serves for all 
 the retinul^e, while in the compound eye there are as many 
 lenses as there are retinulae. Moreover, ocelli do not pass 
 directly into compound eyes, but disappear, and the latter arise 
 independently of the former. 
 
 Probably, as Grenacher holds, both the ocellus and the com- 
 pound eye are derived from a common and simpler type of 
 eye — are '' sisters," so to speak, derived from the same 
 parentage. 
 
 Perception of Light through the Integument. — In vari- 
 ous insects, as also in earthworms, blind chilopods and some 
 other animals, light affects the nervous system through the 
 general integument. Thus eyeless dipterous larvae avoid the 
 light, or, more precisely, they retreat from the rays of shorter 
 wave-length (as the blue), but come to rest in the rays of 
 longer wave-length (red), as if they were in darkness (see 
 page 350). The blind cave-beetles of the genus Anophthal- 
 imts react to the light of a candle (Packard). Graber found 
 that a cockroach deprived of its eyesight could still perceive 
 light, but Lubbock found that an ant whose eyes had been 
 covered with an opaque varnish became indifferent to light. 
 
 Color Sense. — Insects undoubtedly distinguish certain col- 
 ors, though their color sense differs in range from our own. 
 Thus ants avoid violet light as they do sunlight, but probably 
 cannot distinguish red or orange light from darkness; on 
 the other hand, they are extremely sensitive to the ultra-violet 
 rays, which make no sensible impression upon us. Honey 
 
ANATOMY AND PHYSIOLOGY I I 5 
 
 bees frequently select Hue flowers; white butterflies (Pieris) 
 prefer white flowers, and yellow butterflies (Colias) appear 
 to alight on yellow flowers in preference to white ones (Pack- 
 ard). In fact, the color sense is largely relied upon by insects 
 to find particular flowers and l)y butterflies to a large extent to 
 flntl their mates. To be sure, insects will visit flowers after 
 
 Fig. 144- 
 
 Alimentary tract of a collembolan, Orchcsclla. F, fore gut; H, hind gut; M, mid 
 gut; c, cardiac valve; cm, circular muscle; Im. longitudinal muscle; p, pharynx; py, 
 pyloric valve. 
 
 the brightly colored petals have been removed or concealed, 
 as Plateau found, l;)ut this does not prove that the colors are 
 of no assistance to the insect, though it does show that they 
 are not the sole attraction — the odor also being an important 
 guide. 
 
 Problematical Sense Organs. — As all our ideas in regard 
 to the sensations of insects are necessarily inferences from our 
 own sensory experiences, they are inevitably inadequate. 
 While it is certain that insects have at least the senses of touch, 
 taste, smell, hearing and sight, it is also certain that these 
 senses of theirs differ remarkably in range from our own, as 
 we have shown. We can form no accurate conception of these 
 ordinary senses in insects, to say nothing of others that insects 
 have, some of which are probably peculiar to insects. Thus 
 they have many curious integumentary organs which from 
 their structure and nerve connections are probably sensory 
 end-organs, though their functions are either doubtful or un- 
 known. Such an organ is the sensillum placodeum (p. 95), 
 the use of which is very doubtful, though the organ is pos- 
 sibly affected by air pressure. Insects are extremely sensitive 
 
i6 
 
 ENTOMOLOGY 
 
 to variations of wind, temperature, moisture and atmospheric 
 pressure, and very likely have special end-organs for the per- 
 ception of these variations; indeed, the sensilla trichodea are 
 probably affected by the wind, as we have said. 
 
 The halteres of Diptera, representing the hind wings, con- 
 tain sensory organs of some sort. They have been variously 
 regarded as olfactory (Lee), auditory (Graber),and as organs 
 of equilibration. When one or both halteres are removed, 
 the fly can no longer maintain its equilibrium in the air, and 
 Weinland holds that the direction of flight is affected by the 
 movements of these " balancers." 
 
 6. Digestive System 
 
 The alimentary tract in its simplest form is to be seen in 
 Thysanura, Collembola and most larv?e, in which (Fig. 144) 
 it is a simple tube extending along the axis of the body and 
 
 Alimentary tract of a grasshopper, Melanophis differentialis. c, colon; cr, crop; 
 Sc, gc, gastric caeca; i, ileum; m, mid intestine, or stomach; mt, Malpighian, or kid- 
 ney, tubes; o, oesophagus; p, pharynx; r, rectum; s, salivary gland of left side. 
 
 consisting of three regions, namely, fore, mid and Jiind gut. 
 These regional distinctions are fundamental, as the embry- 
 ology shows, for the middle region is entodermal in origin 
 and the two others are ectodermal, as appears beyond. 
 
 There are many departures from this primitive condition, 
 and the most specialized insects exhibit the following- modifi- 
 cations (Figs. 145, 146) of the three primary regions: 
 
 Fore intestine {stoinodcruin) : mouth, pharynx, oesophagus, 
 crop, proventriculus (gizzard), cardiac valve. 
 
ANATOMY AND PHYSIOLOGY 
 
 117 
 
 Fig. 146. 
 
 Mid iiifc'sfiiic (incseiiteron) : ventriculus (stomach). 
 
 HiJhi nitrstiiic ( proctodmim) : pyloric valve, ileum, colon, 
 rectum, aims. 
 
 Stomodaeum. — The mouth, the anterior opening- of the 
 food canal, is to be dis- 
 tinguished from the 
 pharynx, a dilatation for 
 reception of food. In 
 the pharynx of mandib- 
 ulate insects the food is 
 acted upon by the saliva ; 
 in suctorial forms the 
 pharynx acts as a pump- 
 ing organ, in the manner 
 already described. 
 
 The ocsopliagus is com- 
 monly a simple tube of 
 small and uniform cali- 
 ber, varying greatly in 
 length according to the 
 kind of insect. Passing 
 between the commissures 
 that connect the brain 
 with the subcesophageal 
 ganglion (Fig. 113), the 
 oesophagus leads grad- 
 ually or else abruptly 
 into the crop or gizsard, 
 or when these are absent, 
 directly into the stomach. 
 In addition to its func- 
 tion of conducting food, 
 the oesophagus is some- 
 times glandular, as in the grasshopper, in which it is said 
 to secrete the "molasses "wliich these insects emit. 
 
 Digestive system of a beetle, Carahus. a, 
 anal gland; c (of fore gut), crop; c (of 
 hind gut), colon, merging into rectum; d, 
 evacuating duct of anal gland; g, gastric 
 caeca; i, ileum; in, mid intestine; mt, Mal- 
 pighian tubes; o, oesophagus; p, proventricu- 
 lus; r, reservoir. — After Kolbe. 
 
ii8 
 
 ENTOMOLOGY 
 
 Fig. 147 
 
 The crop is conspicuous in most Orthoptera (Fig. 145) and 
 Coleoptera (Fig. 146) as a simple dilatation. In Neuroptera 
 (Fig. 147) its capacity is increased by 
 means of a lateral pocket — the food reser- 
 voir; this in Lepidoptera, Hymenoptera 
 and Diptera is a sac (Fig. 148, c) commu- 
 nicating with the oesophagus by means of 
 a short neck or a long tube, and serving as 
 a temporary receptacle for food. In her- 
 Ijivorous insects the crop contains glucose 
 formed from starch by the action of saliva 
 or the secretion of the crop itself; in car- 
 nivorous insects this secretion converts 
 albuminoids into assimilable peptone-like 
 substances. 
 
 Next comes the enlargement known as 
 the prorciitriciiliis, or gi:;::ard, which is 
 present in many insects, especially Orthop- 
 tera and Coleoptera (Fig. 146), and is 
 usually found in such mandibulate insects 
 as feed upon hard substances. The pro- 
 ventriculus is lined with chitinous teeth or 
 ridges for straining the food, and has 
 powerful circular muscles to squeeze the 
 food back into the stomach, as well as 
 longitudinal muscles for relaxing, or open- 
 ing, the gizzard. Some authors maintain that the proventricu- 
 lus not only serves as a strainer, but also helps to comminute 
 the food, like the gizzard of a bird. 
 
 In most insects a cardiac valve guards the entrance to the 
 stomach, preventing the return of food to the gullet. This 
 valve (Figs. 144, 149) is an intrusion of the stomodseum into 
 the mesenteron, forming a circular lip which permits food to 
 pass backward, but closes upon pressure from behind. 
 
 Mesenteron. — The vciitricuhis, otherwise known as the 
 
 Digestive system of 
 Myrmeleon larva. c, 
 csecum; cr, crop; m, mid 
 intestine; mt, Malpighian 
 tubes; s, spinneret. — 
 After Meinert. 
 
ANATOMY AND PHYSIOLOGY 
 
 119 
 
 mid intestine, or stomach, is usually a simple tube of large 
 caliber, as compared with the oesophagus or intestine, and into 
 
 Fig. 148. 
 
 cm 
 
 Alimentary tract of a moth, Sphinx, c, food reservoir; cl, colon; cm, caecum; i, ileui 
 m, mid intestine; mt, Malpighian tubes; o, a-sophagus; r, rectum; s, salivary gland. 
 After Wagner. 
 
 the ventriculus may open glandular blind tubes 
 cccca (Figs. 145. 146) ; these, though 
 numerous in some insects, are commonly 
 few in number and restricted to the ante- 
 rior region of the stomach. The gastric 
 c?eca of Orthoptera secrete a weak acid 
 ^^•hich emulsifies fats, or one which passes 
 forward into the crop, there to act upon 
 albuminoid substances. In the stomach 
 the food may be acted upon by a fluid 
 secreted by specialized cells of the epithe- 
 lial wall. In various insects, certain cells 
 project periodically into the lumen of the 
 stomach as papillse, which by a process of 
 constriction become separated from the 
 parent cells and mix bodily with the food. 
 This phenomenon takes place in the larva 
 of Ptychoptera (van Gehuchten), also in 
 nymphs of Odonata (Needham), and is 
 probably of widespread occurrence among 
 insects. The chief function of the 
 
 Cardiac valve of young 
 muscid larva, o, cesoph- 
 agus; p, proventriculus; 
 z', valve. In an older 
 larva the valve projects 
 into the mid intestine. — 
 After KowALEVSKY. 
 
I20 
 
 ENTOMOLOGY 
 
 Stomach, however, is absorption, which is effected by the 
 general epithehum. Physiologically, the so-called stomach of 
 an insect is quite unlike the stomach of a vertebrate, being more 
 like an intestine. 
 
 Proctodasum. — At the anterior end of the hind intestine 
 there is usually a pyloric valve, which prevents the contents of 
 the intestine from returning into the stomach. This valve may 
 operate by means of a sphincter, or constricting, muscle, or 
 may, as in Collembola (Fig. 144), con- 
 sist of a backward-projecting circular 
 ridge, or lip. which closes upon pressure 
 from behind. 
 
 In its primitive condition the hind 
 intestine is a simple tube (Fig. 144). 
 Usually, however, it presents two or 
 even three specialized regions, namely 
 and in order, ileum, colon and rectum 
 (Fig. 145). The hind intestine varies 
 greatly in length and is frecjuently so 
 long as to be thrown into convolutions 
 (Fig. 150). The ileum is short and 
 stout in grasshoppers (Fig. 145) ; long, 
 slender and convoluted in many carniv- 
 orous beetles ; and quite short in cater- 
 pillars and most other larvje ; its func- 
 tion is absorption. The colon, often 
 absent, is evident in Orthoptera and 
 Lepidoptera and may bear (Bencicus, 
 Dytiscus, Silphidse, Lepidoptera) a con- 
 spicuous cjecal appendage (Figs. 148, 150) of doubtful func- 
 tion, though possibly a reservoir for excretions. The colon 
 contains indigestible matter and the waste products of diges- 
 tion, including the excretions of the Malpighian tubes. The 
 rectum (Fig. 145) is thick-walled, strongly muscular and often 
 folded internally. Its office is to expel excrementitious matter, 
 consisting largely of the indigestible substances chitin, cellulose 
 
 Digestive system of Belos- 
 toma. c, caecum; i, ileum; 
 m, mid intestine; mt, Mal- 
 pighian tubes; r, salivary 
 reservoir; s, salivary gland. 
 — After LocY, from the 
 American Naturalist. 
 
ANATOjMY AND PHYSIOLOGY 
 
 121 
 
 and chlorophyll. The rectum terminates in the anus, which 
 opens throug-h the last segment of the ahdomen, always above 
 the g"enital apertnre. 
 
 Histology. — The epithelial wall of the alimentary tract is 
 a single layer of cells (Fig. 151). which secretes the intima, 
 or lining layer, and the basement mcuihranc — a delicate, struc- 
 tureless enveloping layer. 
 The intima, which is contin- 
 uous with the external cutic- 
 ula, is chitinous in the fore 
 and hind gut (which are 
 ectodermal in origin), but 
 not in the mid gut (entoder- 
 mal), and usually exhibits 
 extremely fine transverse 
 stri?e, which are due prob- 
 ably to minute pore canals. 
 Surrounding the basement 
 membrane is a series of cir- 
 cular muscles and outside 
 these is a layer of longitudi- 
 nal muscles. The circular 
 muscles serve to constrict the pharynx in sucking insects 
 and, in general, to squeeze backward the contents of the 
 alimentary canal by successively reducing its caliber. The 
 longitudinal muscles, restricted almost entirely to the mid 
 intestine, act in opposition to the constricting muscles to en- 
 large the lumen of the food canal and in addition to efifect 
 peristaltic movements of the stomach. 
 
 The intima of the crop is sometimes shaped into teeth, and 
 that of the proventriculus is heavily chitinized and variously 
 modified to form spines, teeth or ridges. 
 
 Salivary Glands. — In their simplest condition, the salivary 
 glands are a pair of blind tubes (Fig. 152), one on each side 
 of the oesophagus and opening separately at the base of the 
 hypopharynx. Commonly, however, the glands open through 
 
 W'all of mid intestine of silk worm, 
 transverse section, b, basement membrane; 
 c, circular muscle; i, intima; /, longitudinal 
 muscle; n, n, nuclei of epithelial cells; s, 
 secretory cell. 
 
ENTOMOLOGY 
 
 Fig. 152. 
 
 g 
 
 two salivary ducts into a common, or evacuating, duct ; a pair 
 of salivary reservoirs (Fig. 153) may be 
 present, and the glands are frequently 
 branched or lobed, and, though usually 
 confined to the head, may extend into the 
 thorax or even into the abdomen. 
 
 Many insects have more than one pair 
 of glands opening into the pharynx or 
 oesophagus ; thus the honey bee has six 
 pairs and Hymenoptera as a whole have 
 as many as ten different pairs. Though 
 all these are loosely spoken of as salivary 
 glands, it is better to restrict that term to 
 the pair of glands that open at the hypo- 
 pharynx. 
 
 All these cephalic glands are evagina- 
 tions of the stomodseum (ectodermal in 
 origin) and consist of an epithelial layer 
 with the customary intima and basement 
 membrane (Fig. 154). The nuclei are 
 large, as is usually the case in glandular 
 cells, and the cytoplasm consists of a dense 
 framework (appearing in sections as a 
 network) enclosing vacuoles of a clear 
 substance — the secretion; the chitinous 
 Fig. 
 
 A simple salivary 
 gland of Cacilius. c, 
 canal; (/, duct; g, g, gland- 
 ular cells. — After Kolbe. 
 
 Right salivary gland of cockroach, ventral aspect, c, common duct; g, gland; h, 
 hypopharynx; r, reservoir. — After Miall and Denny. 
 
ANATOMY AND PHYSIOLOGY 
 
 123 
 
 Histology of salivary gland 
 of Cacilius, radial section. h, 
 basement membrane; c, canal; 
 g, glandular cell; i, intima; n, 
 nucleus. — After Kolbe. 
 
 intima is penetrated by fine pore canals through which the 
 secretion passe.^. In many insects, notably the cockroach, the 
 common duct is held distended by 
 spiral threads which give the duct 
 much the appearance of a tra- 
 chea. 
 
 In herbivorous insects the saliva 
 changes starch into glucose, as in 
 vertebrates; in carnivorous forms it 
 acts on proteids and is often used 
 to poison the prey, as in the larva 
 of Dytiscits. In the mosquito each 
 gland is three-lobed (Fig. 155) ; the 
 middle lobe is different in appearance 
 from the two others and secretes 
 a poisonous fluid which is carried out 
 along the hypopharynx. Though this poison is said to facili- 
 tate the process of blood-sucking by preventing the coagulation 
 of the blood, its primary use was perhaps to act upon proteids 
 in the juices of plants. 
 
 Malpighian Tubes. — The kidney, or Malpighian, tubes, 
 present in nearly all insects, are long, slender, blind tubes open- 
 ing into the intestine imme- 
 diately behind the stomach 
 as a rule (Figs. 145, 146), 
 but always into the intestine. 
 The number of kidney tubes is 
 very different in different in- 
 sects; Collembola have none, 
 while Odonata have fifty or more and Acridiid?e as many as 
 one hundred and fifty; commonly, however, there are four or 
 six, as in Coleoptera, Lepidoptera and many other orders. 
 Not more than six and frequently only four occur in the em- 
 bryo (Wheeler), though these few embryonic tubes may sub- 
 sequently branch into many. 
 
 One of the three-lobed salivary glands 
 of a mosquito. The middle lobe secretes 
 the poison. — After Macloskie, from the 
 American Naturalist. 
 
124 
 
 ENTOMOLOGY 
 
 Fig. 156. 
 
 The Malpighian tubes (Fig. 156) are evaginations of the 
 proctodaeum and are consequently ectodermal. A cross sec- 
 tion of a tube shows a ring of from one 
 to six or more large polygonal cells (Fig. 
 157), which often project into the lumen 
 of the tube ; the nuclei are usually large 
 and may be branched, as in Lepidoptera. 
 A chitinous intima, traversed by pore- 
 canals, lines the tube, and a delicate base- 
 ment membrane is present, surrounded 
 by a peritoneal layer of connective tissue. 
 Furthermore, the urinary tubes are richly 
 supplied with tracheae. In function, the 
 Malpighian tubes are analogous to the 
 vertebrate kidneys and contain a great 
 variety of substances, chief among 
 which are uric acid and its derivatives 
 (such as urate of sodium and of ammo- 
 nium), calcium oxalate and calcium car- 
 bonate. 
 
 Parts of the fat-body may also be 
 concerned in excretion ; thus the fat- 
 body in Collembola and Orthop- pj^, ^ry 
 tera serves for the permanent stor- 
 age of urates. 
 
 7. Circulatory System 
 Insects, unlike vertebrates, have 
 no system of closed blood-vessels, 
 but the blood wanders freely 
 through the body cavity to enter cross section of Malpighian tube 
 eventually the dorsal vessel, which ^^ silkworm, Bombyx mori. b, 
 
 . . basement membrane; c, crystals; i, 
 
 resembles a heart merely in bemg intima; /, lumen; n, nucleus; p. 
 
 a propulsatory organ. ' peritoneal layer. Greatly magnified. 
 
 Dorsal Vessel. — The dorsal vessel (Figs. 158, 162) is a 
 
 Portion of Malpighian 
 tube of caterpillar, Samia 
 cecropia, surface view. 
 
ANATOMY AND PHYSIOLOGY 
 
 ately under the integ^ument. A simple tube in some larvcT, it 
 consists in most adults chiefly of a series of chambers, each of 
 
 Fig. 158. 
 
 Dorsal vessel of beetle, 
 Lucantis. a, aorta; al, alary 
 muscle; o, ostium. — After 
 Steaus-Durckheim. 
 
 Diagram of a portion of the heart of a dragon 
 fly nymph, Epithcca. o, ostium; z; valve; the ar- 
 rows indicate the course of the blood. — After 
 
 KoLBE. 
 
 Fig. 160. 
 
 Diagrammatic cross section of pericardial 
 region of a grasshopper, Qidipoda. a, alary 
 muscle; d, dorsal vessel; s, suspensory mus- 
 cles; sp, septum. — After Graber. 
 
 Blood corpuscles of a grasshopper, Stoiobotltnis. a~f, corpuscles covered witli fat- 
 globules; g, corpuscle after treatment with glycerine, showing nucleus. — After Graber. 
 
 which has on each side a valvular opening, or ostium (Fig. 
 159) , which permits the ingress of blood but opposes its egress ; 
 
126 
 
 ENTOMOLOGY 
 
 within the chambers occur other valvular folds that allow the 
 blood to move forward only. With few exceptions (Ephe- 
 meridcx) the dorsal vessel is blind behind and the blood can 
 enter it only through the lateral ostia. 
 
 Aorta. — The posterior, or 
 pulsating portion (heart) of 
 the dorsal vessel is confined 
 for the most part to the abdo- 
 men ; the anterior portion, or 
 aorta, extends as a simple 
 attenuated tube through the 
 thorax and into the head, 
 where it passes under the 
 brain and usually divides into 
 two l)ranches (Fig. 162), 
 each of which may again 
 branch. In the head the 
 blood leaves the aorta ab- 
 ruptly and enters the general 
 body cavity. 
 
 Alary Muscles. — Extend- 
 ing outward from the "heart," 
 or propulsatory portion, and 
 making with the dorsal wall 
 of the body a pericardial 
 chamber, is a loose diaphragm, 
 formed largely by paired fan-like muscles — the alary muscles 
 (Eigs. 158, 160). These are thought to assist the heart in its 
 propulsatory action. 
 
 Structure of the Heart. — The dorsal vessel has a delicate 
 lining-membrane, or intima, and a thin enveloping membrane; 
 between these, in the heart, is a layer of fine muscle fibers, cir- 
 cular or spiral in direction, which efifect the contractions of the 
 organ. 
 
 Ventral Sinus. — In many if not most insects a pulsatory 
 septum (Fig. 177, v) extends across the floor of the body cav- 
 
 r^ 
 
 Diagram to indicate the course of the 
 blood in the nymph of a dragon fly, 
 Epitheca. a, aorta; h, heart; the arrows 
 show directions taken by currents of 
 blood. — After Kolbe. 
 
ANATOMY AND PHYSIOLOGY I 2/ 
 
 ity to form a sinus, in wliicli tlic blood flows backward, batbiiio- 
 the ventral nerve cord as it "'oes. Tliis ventral sinus supple- 
 ments the heart in a minor way, as do also the local pulsatory 
 sacs which ha\e l)een discovered in the lei^'s of arjuatic Hemip- 
 tera and the head of Orthoptera. 
 
 Blood. — The blood, or hcumolyinph, of an insect consists 
 chielly of a watery fluid, or plasma, which contains corpuscles, 
 or leucocytes. Thoug-h usually colorless, the plasma is some- 
 times A^ellow (Coccinellidrc, Meloidre), often greenish in her- 
 bivorous insects from the presence of chlorophyll, and some- 
 times of other colors ; often the blood owes its hue to yellow 
 or red drops of fat on the surface of the blood corpuscles 
 (Fig. i6i). 
 
 Leucocytes. — The corpuscles, or leucocytes, are minute 
 nucleated cells, 6 to 30 ;«■ in diameter, variable in form even 
 in the same species but commonly (Fig. 161) round, oval or 
 ovate in profile, though often disk-shaped, elongate or amoe- 
 boid in form. 
 
 Function of the Blood. — The blood of insects contains 
 many substances, including egg albumin, globulin, fibrin, iron, 
 potassium and sodium (Mayer), and especially such a large 
 amount of fatty material that its principal function is probably 
 one of nutrition; the blood of an insect contains no red cor- 
 puscles and has little or nothing to do with the aeration 
 of tissues, that function being relegated to the tracheal 
 system. 
 
 Circulation. — The course of the circulation is evident in 
 transparent aquatic nymphs or larv?e. In odonate or ephe- 
 merid nymphs, currents of blood may be seen (Fig. 162) flow- 
 ing through the spaces between muscles, tracheze, nerves, etc., 
 and bathing all the tissues; separate outgoing and incoming 
 streams may be distinguished in the antennae and legs; the 
 returning blood flows along the sides of the body and through 
 the ventral sinus and the pericardial chamber, eventually to 
 enter the lateral ostia of the dorsal vessel. A circulation of 
 blood occurs in the wings of freshly emerged Odonata. Ephe- 
 
128 ENTOMOLOGY 
 
 merida, Coleoptera, Lepidoptera, etc., the currents trending 
 along- the tracheje; this circulation ceases, however, with the 
 drying of the wings. 
 
 The chambers of the dorsal vessel expand and contract suc- 
 cessively from behind forward. At the expansion (diastole) 
 of a chamber its ostia open and admit blood ; at contraction 
 (systole) the ostia close, as well as the valve of the chamber 
 next behind, while the chamber next in front expands, afford- 
 ing the only exit for the blood. The valves close partly 
 through blood-pressure and partly by muscular action. 
 
 The rate of pulsation depends to a great extent upon the 
 activity of the insect and upon the temperature and the amount 
 of oxygen or carbonic acid gas in the surrounding atmosphere. 
 Oxygen accelerates the action of the heart and carbonic acid 
 gas retards it. A decrease of 8° or io° C. in the case of the 
 silkworm lowers the number of beats from 30 or 40 to 6 or 
 8 per minute. The more active an insect, the faster its heart 
 beats. 
 
 The rate of pulsation is very different in the different stages 
 of the same insect. Thus in Sphinx ligustri, according to 
 Newport, the mean number of pulsations in a moderately 
 active larva before the first moult is about 82 or 83 per minute ; 
 before the second moult, 89, sinking to 63 before the third 
 moult, to 45 before the fourth, and to 39 in the final larval 
 stage; the force of the circulation, however, increases as the 
 pulsations decrease in number. During the quiescent period 
 immediately preceding each moult, the number of beats is 
 about 30. In the pupal stage the number sinks to 22, and 
 then lowers until, during winter, the pulsations almost cease. 
 The moth in repose shows 41 to 50 per minute, and after flight 
 as many as 139. 
 
 8. Fat-Body 
 
 The fat-body appears (Fig. 163) as many-lobed masses of 
 tissue filling in spaces between other organs and occupying a 
 large part of the body cavity. The distribution of the fat- 
 body is to a certain extent definite, however, for the fat-tissue 
 
ANATOMY AND PHYSIOLOGY 
 
 129 
 
 conforms to the general segmentation and is arranged in each 
 segment with an ap]irf\'ich to symmetry. Much of this tissue 
 forms a distinct peripheral layer in each segment, and masses 
 of fat-hody occur constantly on each side of the alimentary 
 
 Transverse section of the abdomen of a caterpillar, Picris rapcr. b, blood corpus- 
 cles; c, cuticula; d, dorsal vessel; f, fat-body; g, ganglion; /;, hypodermis; /, leg; m, 
 muscle; mi, mid intestine, containing fragments of cabbage leaves; mt, Malpighian 
 tube; s, silk gland; sp, spiracle; tr, trachea. 
 
 tract and also at the sides of the dorsal vessel, in the latter case 
 forming the pericardial fat-body. 
 
 Fat-Cells. — The fat-cells (Fig. 164) are large and at first 
 more or less spherical, with a single nucleus (though there are 
 said to be two in Apis and several in Musca), l)ut the cellular 
 10 
 
30 
 
 ENTOMOLOGY 
 
 Fat-cells of a caterpillar, Pieris. 
 cells filled with drops of fat; B, cell 
 freed of fat-drops, showing nucleus. — 
 After KoLBE. 
 
 Structure of the fat-tissue is often difficult to make out because 
 the cells are usually filled with globules of fat (Fig. 165), 
 
 while old cells break down, 
 leaving only a disorderly net- 
 work. The fat-cells sometimes 
 contain an albuminoid sub- 
 stance, and usually the fat-body 
 includes considerable quantities 
 of uric acid or its derivatives, 
 frequently in the form of con- 
 spicuous concretions. 
 Functions. — The physiology of the fat-system is still ob- 
 scure. Probably the fat-body combines several functions. In 
 caterpillars and other larvje it furnishes a reserve supply of 
 nutriment, at the expense of which the metamorphosis takes 
 place; the amount of fat increases as the larva grows, and 
 diminishes in the pupal stage, though some of it lasts over to 
 furnish nourishment for the imago and its germ cells. The 
 gradual accumulation of uric 
 
 acid and urates in the fat- ^^^- ^^5- 
 
 body indicates an excretory 
 function, particularly in Col- 
 lembola, which have no Mal- 
 pighian tubes. The intimate 
 association between the ulti- 
 mate tracheal branches and 
 the fat-body has led some 
 authorities to ascribe a res- 
 piratory function to the lat- 
 ter. A close relation of 
 some sort exists also be- 
 tween the fat-system and 
 the blood-system ; fat-cells 
 are found free in the blood, 
 
 and the blood corpuscles originate in the thorax and abdo- 
 men from tissues that can scarcely be distinguished from 
 
 Section through fat-body of a silkworm, 
 showing nucleated cells, loaded with drops 
 of fat. 
 
ANATOMY AND PHYSIOLOGY 
 
 131 
 
 ffinocytes and accom- 
 panying trachea, from 
 abdomen of a silkworm. 
 
 fat-tissues. The corpuscles (leucocytes, or phagocytes) which 
 in some insects absorb effete larval tissues during- meta- 
 morphosis have been by some authors reg'arded as wandering 
 fat-cells. Cells cc^nstiluting the pericardial fat-body are at- 
 tached to the lateral muscles (alary muscles) of the dorsal 
 vessel, but almost nothing is known as 
 to their function. Associated with the 
 fat-body proper are the peculiar cells 
 known as a^iiocytes. These occur in 
 most insects, in segmentally-arranged 
 clusters on each side of the abdomen, 
 and consist of exceptionally large cells, 
 more or less rcnnid or oval (Fig. 166), 
 each with a large round, oval or elon- 
 gate nucleus. These peculiar cells are 
 usually separate from one another, but 
 are held in clusters by tracheal branches. 
 Their function is unknown. Finally, the 
 
 fat-body is the basis of the luminosity, or so-called phospho- 
 rescence, of insects. 
 
 Luminosity. — This phenomenon appears sporadically and 
 by various means in protozoans, worms, insects, fishes and 
 other animals. Luminosity in insects, though sometimes 
 merely an incidental and pathological effect of bacteria, is usu- 
 ally produced by special organs in which light is generated 
 probably by the oxidation of a fatty substance. 
 
 There are not many luminous insects. Those best known 
 are the Mexican and West Indian beetles of the genus Py- 
 rophorus (Elateridie), in which the pronotum bears a pair of 
 luminous spots, and the common fire-tiies (Lampyridse). In 
 Lampyrid?e, the light is emitted from the ventral side of the 
 posterior abdominal segments. In our common Photinus, the 
 seat of the light is a modified portion of the fat-body — a 
 photogenic plate, situated immediately under the integument 
 and supplied with a profusion of fine tracheal branches. The 
 cells of the photogenic plate, it is said, secrete a substance which 
 
132 
 
 ENTOMOLOGY 
 
 undergoes rapid combustion in the rich supply of oxygen fur- 
 nished by the tracheae. 
 
 The rays emitted by the common fire-flies are remarkable in 
 being almost entirely light rays, with almost no thermal or 
 
 actinic rays. According to 
 Young' and Langley, the radia- 
 tions of an ordinary gas-tlame 
 contain less than three per cent. 
 of visible rays, the remainder 
 being heat or chemical rays, of 
 no value for illuminating pur- 
 poses ; while the light-giving 
 efficiency of the electric arc is 
 only ten per cent, and that of 
 sunlight only thirty-live per 
 cent. The light of the fire- 
 fly, however, may be rated at 
 one hundred per cent. ; this 
 light, then, is perfect, and as 
 yet unapproached by artificial 
 means. 
 
 As to the use of this lumi- 
 nosity, there is a general 
 opinion that the light exists 
 for the purpose of sexual 
 attraction — a belief held by 
 the author in regard to Pho- 
 tiiiiis, at least. Another view 
 is that the light is a warning 
 
 Tracheal system of an insect, a, an 
 tenna; b, brain; /, leg; n, nerve cord 
 
 p, palpus; ., spiracle; .f spiracular, or ^j j ^^^ nOCtumal birds, batS 
 
 , branch; t, mam tracheal trunk; ^ 
 
 stigmatal 
 
 V, ventral branch 
 
 After KoLBE. 
 
 isceral branch.- 
 
 )r other insectivorous animals: 
 this is supported by the fact 
 that lampyrids are refused Ijy birds in general, after ex- 
 perience; young birds readily snap at a fire-fly for the first 
 time, but at once reject it and thereafter pay no attention to 
 these insects. 
 
ANATOMY AND PHYSIOLOGY 
 
 133 
 
 9. Respiratory System 
 In insects, as contrasted with vertebrates, the air itself is 
 conveyed to tlic remotest tissues l)y means of an elaborate sys- 
 tem (vf branchins^- air-tubes, or Iraclwcc, which receive air 
 throui^h paired se^nientally-arran£j;e(l sf^irnclcs. Each spiracle 
 is commonly the mouth of a short tube which opens into a 
 main tracheal trunk (Fig. 167) extending along the side of 
 
 Diagrammatic cross section of the thorax of an insect, a, alimentary canal; d, 
 dorsal vessel; g, ganglion; ,?, spiracle; zv, wing; /, dorsal tracheal branch; 3, visceral 
 branch; ^, ventral branch. 
 
 the body. From the two main trunks branches are sent which 
 divide and subdivide until they become extremely delicate 
 tubes, which penetrate even between muscle fibers, between the 
 ommatidia of the compound eyes and possibly enter cells. In 
 most cases each main longitudinal trunk gives off in each seg- 
 ment (Fig. i68) three large branches: ( i) an upper, or dor- 
 sal, branch, which goes to the dorsal muscles; (2) a middle, 
 or visceral, branch, which supplies the alimentary tract and the 
 reproductive organs; (3) a lower, or ventral, branch, which 
 pertains to the ventral ganglia and muscles. 
 
 In many swiftly-flying insects (dragon flies, beetles, moths, 
 flies and bees) there occur tracheal pockets, or air-sacs, which 
 
134 
 
 ENTOMOLOGY 
 
 Fig. 169. 
 
 were formerly and erroneously supposed to diminish the 
 weight of the insect, but are now regarded as simply air- 
 reservoirs. 
 
 Types of Tracheation. — Two types of tracheal system are 
 distinguished for convenience : ( i ) The primary, open, or 
 
 Iwlopncustic type described 
 above, in which the spiracles 
 are functional; (2) the sec- 
 ondary, closed, or apncitstic 
 type, in which the spiracles 
 are either functionless or ab- 
 sent. This type is illustrated 
 in Collembola and such acjuatic 
 nymphs and larvae as breathe 
 either directly through the skin 
 or else by means of gills. 
 The two types, howe\'er, are 
 connected by all sorts of inter- 
 mediate stages. 
 
 Tracheal Gills. — In manv 
 
 Lateral gill from abdomen of a May 
 fly nymph, Hcxagcnia variabilis. En- 
 larged. 
 
 acjuatic nymphs and larva? the 
 
 spiracles are suppressed (though they become functional in 
 
 the imago) and respiration is effected by means of gills; these 
 
 are cuticular outgrowths which usuallv, ^ 
 
 ^ . ' Fig. 170. 
 
 though not invariably, contain tracheae, 
 
 and are commonly lateral or caudal in 
 position. Lateral tracheal gills are 
 highly developed in ephemerid nymphs 
 (Fig. 169), in which a pair occurs on 
 some or all of the first seven segments 
 of the abdomen ; a few genera, how- 
 ever, have cephalic or thoracic gills. Larvae of Trichoptera 
 have paired abdominal gills varying greatly in form and posi- 
 tion, and Perlidae often have paired thoracic gills. Caudal 
 traclieal gills are conspicuous in nymphs of Agrionidae (Fig. 
 170) as three foliaceous appendages. A few coleopterous 
 
 Caudal gills of 
 agrionid nyniph, 
 larged. 
 
ANATOMY AND PHYSIOLOGY 
 
 135 
 
 larxcT of cuiiiatic hal)it, as Gyriuits and 
 Ciicniidofiis, possess tracheal gills, as do 
 also caterpillars of the g'eniis Paniponyx 
 {V\g. 171). which feed 011 the leaves of 
 several kinds of water plants. 
 
 Though manifold in form, tracheal 
 g'ills are generally more or less foliaceous 
 or filamentous, presenting always an ex- 
 tensive respiratory surface ; their integu- 
 ment is thin and the tracheae spread 
 closely beneath it. These adaptations 
 are often supplemented by waving move- 
 ments of the gills, as in May fly nymphs, 
 and by frequent movements of the insect 
 from one place to another. 
 
 Especially noteworthy are the rectal 
 tracheal gills of odonate nymphs. In 
 these insects the lining- of the rectum 
 forms numerous papilke or lamellse, which 
 
 contain a profusion of delicate tracheal 
 branches; these are bathed by water 
 drawn into the rectum and then expelled, 
 at rather irregular intervals. A similar 
 rectal respiration occurs also in ephemerid 
 nymphs and mosquito larvae. 
 
 A few forms, chiefly Perlidae, are 
 exceptional in retaining tracheal gills 
 in the adult stage ; in some imagines 
 they are merely vestiges of the nymphal 
 gills, but in others, such as Pteronarcys 
 (Fig. 18), which habitually dips into 
 the water and rests in moist situations, 
 the gills probablv supplement the spira- 
 .i;r <:J-,./s;:r: cles. Further details on the respiration 
 ing respiratory tube. ^f aquatic iusccts are given in Chapter 
 
 Natural size. — After 
 
 Hapt. IV. 
 
 Caterpillar of Para- 
 ponyx obscuralis, to show 
 tracheal gills. Length, 
 15 mm. — After Hart. 
 
 Fig. 172. 
 
136 
 
 ENTOMOLOGY 
 
 Spiracles. — The paired external openings of the tracheae 
 occur on the sides of the thorax and abdomen, there being 
 never more than one pair to a segment. Though the thysa- 
 nuran Japy.v has ii pairs, no winged insect has more than lo; 
 ahhough there are in all 12 segments which may bear spiracles 
 — the three thoracic and the first nine abdominal segments. 
 (Additional details are given on page 66.) 
 
 The spiracles, or stigmata, are usually provided with bris- 
 tles, hairs or other processes to exclude dust ; or the hairs of 
 the body may serve the same purpose, as in Lepidoptera and 
 Diptera ; in many beetles the spiracles are protected by the 
 elytra ; in other beetles, however, and in many Hemiptera and 
 Diptera the spiracles are unprotected externally. Larvje that 
 live in water or mud may have spiracles at the end of a long 
 
 Fig. 173. 
 
 Apparatus for closing the spiracular trachea in a beetle, Luc 
 opened; B, closed; b, bow; bd, band; c, external cuticula; /, lever; 
 spiracle; t, trachea. — After Judeich and Nitsche. 
 
 4, trachea 
 muscle; s, 
 
 tube, which can be thrust up into the pure air; this is true of 
 the dipterous larv?e of Eristalis, Bittacouwrpha (Fig. 172) 
 and Culcx (Fig. 229). 
 
 Closure of Spiracles. — As a rule, a spiracle is opened and 
 closed periodically by means of a valve, operated by a special 
 occlusoi' muscle. In dipterous larvae the closure is effected by 
 the contraction of a circular muscle, but Coleoptera and Lepi- 
 doptera, among other insects, ha\'e a somewhat complex appa- 
 ratus for closing the trachea immediately behind the spiracle. 
 
ANATOMY AND PIIVSIOLOGV 
 
 137 
 
 Tims, in the stag-beetle, a crescentic bo-.i' ( I-'ig. 173, /;) extends 
 half around the trachea, and the rest of the circumference is 
 
 s])anned hy a /cc'cr (/) and a band (/></) ; these three chitinons 
 
 ny- around the trachea, 
 the lever and the hand. 
 
 Fk;. i7i. 
 
 ])arts, articulated to.^ether, form a r 
 I'urthermorc, a muscle ( /// ) connects 
 As the muscle shortens, the lexer 
 turning- ui)on the end of the hand as 
 a fulcrum, pulls the l)o\v toward the 
 lever and hand until the enclosed 
 trachea is pinched together, ^^dlen 
 the muscle relaxes, the trachea opens 
 1)_\- its own elasticity. 
 
 Structure of Tracheae. — The 
 trachea' originate in the emhrvo as 
 simple in-pocketings of the outer 
 germ layer, or ectoderm, and from 
 these the countless tracheal l)ranches 
 are deri\'ed by the same process 
 of invagination. The lining mem- 
 brane of a trachea is, then, con- 
 tinuous with the external cuticula, 
 
 and the cellular wall of a trachea is continuous wdth the 
 rest of the hypodermis. This wall consists of a layer of 
 polygonal cells (Fig. 174) fitting closely together as a paz'c- 
 mcnt epithelium. The chitinous lining-, or iiitiiiia, is thick- 
 ened at regular intervals to form thread-like ridges, which 
 course around the inner circumference in essentially a spiral 
 manner, though the continuity of the so-called spiral thread is 
 frecjuently interrupted. These elastic threads, or tccnidia, 
 serve to keep the trachea open without affecting its flexibility. 
 
 The ultimate tracheal branches (Fig. 175) are extremely 
 delicate tubes, which do not end blindly, but anastomose with 
 one another, forming- a capillary network of continent tubes. 
 Some authors have held that the finest tracheal filanients pene- 
 trate epithelial or other cells. 
 
 Respiration. — The external signs of respiration are the 
 
 Structure of a trachea. .';, 
 icheal hypodermis; i, intima; 
 t.-enidium. 
 
i^iS 
 
 ENTOMOLOGY 
 
 regular opening and closing movements of some of the spira- 
 cles and the rhythmic contraction and expansion of the abdo- 
 men. During contraction, the dorsal and ventral walls ap- 
 
 Tracheal capillary end-network from silk gland of Porthetria dispar. p, peritracheal 
 membrane; t, tracheal capillary. — After Wistingh.\usen. 
 
 proach each other (Fig. 176) and during expansion they 
 separate. The tergum moves more than the sternum in Cole- 
 optera and Heteroptera, and vice ^■ersa in Acridiidae, Odonata, 
 Diptera and aculeate Hymenoptera. The width of the abdo- 
 men usually changes but little during respiration, for the ter- 
 gal and sternal movements are taken up by the pleural mem- 
 
 FiG. 176. 
 I t 
 
 A ^ 
 
 Transverse sections of abdominal segments, to illustrate respiratory movements. A, 
 cockroach (Blatta); B, bee (Boinbiis): s, sternum; t, tergum. The dotted lines 
 indicate positions of terga and sterna after expiration; the continuous lines, after 
 inspiration. — After Plateau. 
 
 bra lies which, as in the grasshopper, infold at contraction and 
 straighten out at expansion. Other respiratory movements 
 occur, but they are of minor importance. 
 
ANATOMY AND PHYSIOLOGY 
 
 139 
 
 Tlie rate of respiration increases or diminishes with the 
 activity of the insect and with temperature and other conch- 
 tions. In six specimens of Mclanophis diiferciitialis, held he- 
 tween the fino-ers, the thoracic spiracles opened and closed 
 resi)ectively 34. 43, 45. 54, ()0 
 indi\-i(hi.'ds of .1/. fcniiir- 
 
 riibniiii under the same cii 
 
 ()i times per minute. Four 
 
 'O, 
 
 90 
 
 cumstances g; 
 and t;2. 
 
 At expansion inspiration 
 takes place, and at contrac- 
 tion expiration occurs. In 
 the grasshopper, the thoracic 
 spiracles open almost simul- 
 taneously with the expan- 
 sion of the ahdomen. Con- 
 traction is effected by special 
 vertical expiratory muscles 
 (Fig. 177), but expansion 
 is due to the elasticity of 
 the abdominal wall, as a 
 rule ; this is the reverse 
 of what occurs in mam- 
 mals, wdiere expiration is 
 passive and inspiration ac- 
 tive. Inspiratory muscles 
 are found, however, in Acridiida;, Trichoptera and Hymen- 
 optera. 
 
 Though the respiratory movements of an insect may be 
 studied with a hand-lens, a more precise method is that of 
 Plateau — the chief authority on insect physiology — who made 
 use of the stereopticon to project an enlarged profile of the 
 insect upon a screen, on which could be marked the different 
 contours of the abdomen at its phases of inspiration and 
 expiration. 
 
 The way in which the air reaches the finest tracheal branches 
 
 Diagrammatic cross section of abdomen 
 of a grasshopper, Acridium. d, dorsal 
 septum, or diapliragm; ex, expiratory mus- 
 cle; /, fat-body; g, ganglion; /;, heart; in, 
 inspiratory muscle; r, ventral septum, be- 
 low which is the ventral sinus. The dorsal 
 and ventral septa rise and fall periodically. 
 — After Graber. 
 
I40 
 
 ENTOMOLOGY 
 
 is not clearly ascertained, but it is thoiig-ht that air is forced 
 into these tubes by pressure from the abdominal muscles, while 
 its escape through the spiracles is being prevented by the com- 
 pression of the stigmatal trache??. 
 
 The respiratory movements are entirely reflex and are inde- 
 pendent of the brain or suboesophageal ganglion, for they con- 
 tinue after decapitation and even in the detached abdomen of 
 a grasshopper or dragon fly. Each ventral ganglion of the 
 body is an independent respiratory center for its particular 
 segment. 
 
 lo. Reproductive System 
 
 The sexes are always separate in insects, hermaphroditism 
 occurring only as an abnormal condition. The sexual organs, 
 situated in the abdomen, consist essentially of a pair of ovaries 
 
 Fig. 1/8. 
 
 Fig. 179. 
 
 Reproductive system of male beetle, Melo 
 lontha. a, accessory gland; c, copulatory 
 organ; d, ejaculatory duct; s, seminal vesicle; 
 t, testis; v, vas deferens. — After Kolbe. 
 
 Reproductive system of male 
 Lepidoptera. a, accessory gland; 
 d, ejaculatory duct; t, vniited 
 testes; v, vas deferens. — After 
 Kolbe. 
 
 or testes and a pair of ducts [oviducts or seminal ducts, respec- 
 tively). Primitively, the ducts open separately, as they still 
 do in Ephemeridic. but in nearly all other insects the two ducts 
 enter a common evacuating duct {vagina or ejaculatory duct) ; 
 this opens ordinarily between the penultimate and antepenulti- 
 mate segments of the abdomen, i. e., usually the ninth and 
 eighth, at any rate never through the last abdominal segment. 
 
ANATOMY AND PHYSIOLOGY 
 
 141 
 
 Homologies. — As in other animals, the repr(~)(hicti\c or- 
 gans are homologous in the two sexes. Thus : 
 
 Male. Fkmale. 
 
 Testes = Oi'orics 
 Sciniiuil ducts =^ Oc'idiuts 
 Ejaculatory duct = Vagina 
 
 Seminal vesicle = Seminal receptacle 
 Accessory glands = Accessory glands 
 Penis and accessories = Ovipositor 
 
 Male Organs. — Each testis, though sometimes a single 
 blind tube, is usually a group of tubes or sacs (Fig. 178), 
 testicular follicles, which open into a seminal duct (z'as clefer- 
 
 FiG. 180. 
 
 Fig. 18 
 
 Spermatozoa. A, locustid 
 grasshopper; B, cockroach, 
 Blatta; C, beetle, Copris. 
 — After BuTSCHLi and Bal- 
 
 LOWITZ. 
 
 Reproductive system of queen 
 honey bee. a, accessory sac of 
 vagina; b, bulb of stinging ap- 
 paratus; c, colleterial, or cement, 
 gland; o, ovary; od, oviduct; p, 
 poison glands; pr, poison reser- 
 voir; r, receptaculum seminis; 
 re, rectum; ?■, vagina. — After 
 Leuckart. 
 
 ens). In most Lepidoptera the testes are secondarily united 
 into a single mass (Fig. 179) as also in /Vcridiidae. The two 
 seminal ducts enter the common ejaculatory duct, which ter- 
 
142 
 
 ENTOMOLOGY 
 
 minates in the intromittent organ, or penis. Often each vas 
 deferens is dilated near its mouth into a sciiiiiiol vesicle, or 
 reservoir; or there may be only a single seminal vesicle, aris- 
 ing from the common duct. One or more pairs of glands 
 opening into the vasa deferentia or the liiictiis cjaciilaforiiis 
 secrete a fluid which mixes with the spermatozoa and often- 
 times unites them into packets, known as spermatophorcs. 
 
 All these parts are subser- 
 vient to the formation, pres- 
 ervation and emission of the 
 spcnnatozoa. These minute 
 thread-like bodies (Fig. i8o) 
 arise in the testicular follicles 
 from a germinal epitheliuni, 
 and consist, as in vertebrates, 
 of a head, middle-piece and 
 a vibratile /a/7 — without en- 
 tering into the finer struc- 
 ture. 
 
 Female Organs. — Each 
 oi'ary (Fig. i8i ) consists of 
 one or more tubes opening 
 into an oviduct. The two 
 oviducts enter a common 
 duct, the z'agina, which 
 opens to the exterior, often 
 through an ovipositor. Fre- 
 quently the vagina is ex- 
 panded as a pouch, or bursa copulatrix, though in Lepidoptera 
 the bursa and the vagina are distinct from each other and open 
 separately (Fig. 182). In most insects a dorsal evagination 
 of the vagina forms a seminal receptacle, or spermatheca, from 
 which spermatozoa emerge to fertilize the eggs. The acces- 
 sory glands, either paired or single, provide a secretion for 
 attaching the eggs to foreign objects, cementing the eggs to- 
 gether, forming an egg-capsule, etc. 
 
 Reproductive system of female Lepi- 
 doptera. b, bursa copulatrix; /, terminal 
 filament; g, cement glands; o, o, ovaries; 
 od, oviduct; r, receptaculum seminis; -■, 
 vagina; I's, vestibule, or entrance to 
 bursa. — After Kolbe. 
 
ANATOMY AND PHYSIOLOGY 
 
 H3 
 
 Tn each ovarian tube, or ovariole, are found ova in succes- 
 sive stai^-es o\ j^rowth, the lars^est and oldest ovum being- near- 
 est the o\i(hict. In the ])rimitive t}-pe of egg'-tube, as in Thys- 
 aiuu-a and Ortho])tera (Fig. 183, A) every chaniljer ccjntains 
 an o\-uni ; in more speciahzed 
 types, every other chamber con- 
 tains a nutritive cell instead of a 
 germ cell, the nutriti\e cells serv- 
 ing as fo(_)d ft)r the adjacent o\-a 
 [B) ; or the nutriti\e cells, in- 
 stead of alternating with the ova, 
 may be collected in a special 
 chamber, Ijeyond the ovarian 
 chambers {C). An egg-tube is 
 usually prolonged distally as a 
 terminal filament, or suspciisor, 
 the free end of which is attached 
 near the dorsal vessel. 
 
 Ovaries and testes arise from 
 indifferent cells, or primitive 
 germ cells, which are at first 
 exactly alike in the two sexes. 
 In the female, certain of these 
 cells form o\a and others form a 
 foUicic around each o\-um (Fig. 
 184). In the male, the primary 
 germ cells form cells termed 
 spcniiafogoiiia ; each of these 
 forms a spcniiafocytc, and this 
 gives rise to four spcriuatocoa. 
 
 Hermaphroditism. — The phenomenon of hcnnaphrodi- 
 fisiii, or the combination of male and female characters in the 
 same individual, occurs only as an extremely rare abnormality 
 among insects. Speyer estimated that in Lepidoptera only 
 one individual in thirty thousand is hermaphroditic. Bertkau 
 (1889) listed 335 hermaphroditic arthropods, of which 8 were 
 
 Types of ovarian tubes. A, with- 
 out nutritive cells; B, with alternat- 
 ing nutritive and egg-cells; C, with 
 terminal nutritive chamber; c, ter- 
 minal chamber; e, egg-cell; ep, fol- 
 licle epithelium; f, terminal fila- 
 ment; s, strands connecting ova 
 with nutritive chamber; _v, yolk, or 
 nutritive, cells. — From Lang's Lclir- 
 biu-h. 
 
144 
 
 ENTOMOLOGY 
 
 crustaceans. 2 spiders, 2 Orthoptera, 8 Diptera, 9 Coleoptera, 
 51 Hymenoptera and 255 Lepidoptera. The large proportion 
 of Lepidoptera is due in great measure 
 to the fact that they are collected 
 of tener than other insects ( excepting 
 possil)ly C(^leoptera ) and that sexual 
 dimorphism is so prevalent in the 
 order that hermaphrodites are easily 
 recognized. 
 
 The most common kind of her- 
 maphroditism is that in which one 
 side is male and the other female, as in 
 Fig. 185. Bertkau found this right- 
 and-left hermaphroditism in 153 in- 
 dividuals. In other instances the 
 antero-posterior kind may occur, as 
 when the fore wings are of one sex 
 and the hind wings of the other ; 
 rarelv, the characters of the two sexes 
 are intermingled. 
 Hermaphroditic insects are such rarities that very few of 
 them have heen sacrificed to the dissecting needle in order to 
 
 determine whether the 
 
 Fig. 185. 
 phenomenon involves the 
 
 primary organs as well as 
 the secondary sexual char- 
 acters. Where dissections 
 have been made it has 
 been found usually that 
 hermaphroditism does ex- 
 tend to the reproductive 
 organs themselves. Thus 
 a butterfly with male 
 wnngs on the right side 
 and female wings on the 
 left would have a testis on the right side of the abdomen and an 
 ovary on the left side. 
 
 Ovum of a butterfly, Va- 
 nessa, in its follicle, e, fol- 
 licle epithelium; g, germinal 
 vesicle; n, branching nucleus 
 of nutritive cell; o, ovum. — 
 After WooDWORTH. 
 
 Hermaphrodite gypsy moth, Porthetn'a dis- 
 bar; right side, male; left, female. Natural 
 size. — After Taschenberg, from Hertwig's 
 Lchrbiich. 
 
ANATOMY AND PHYSIOLOGY 1 45 
 
 Parthenogenesis. — Reproduction without fertilization is a 
 normal phenomenon in not a few insects. This parthcno- 
 o^cncsis may easily he ohserved in i)lant lice. In these insects 
 there are many snccessixe hroods consistino- of females only, 
 which hrino- forth livin,^- yonn,^-; at dehnite intervals, however, 
 and usually in autumn, males ajjpear also, and fertilized eggs 
 are laid which last o\er winter. This cyclic reproduction, by 
 the way, is known as Jictcrogcny. Among Hymenoptera, 
 parthenogenesis is prevalent, usually alternating with sexual 
 reproduction, as in many Cynipidos. In some Cynipidse, how- 
 ever, males are unknown ; such is the case also in some Ten- 
 thredinidse. The statement has long been made that the un- 
 fertilized eggs of worker ants, bees and wasps produce in\ari- 
 ably males; it has been found recently, however, that the par- 
 thenogenetic worker eggs of the ant Lasius nigcr may produce 
 normal workers ( Reichenbach, Mrs. A. B. Comstock). Males 
 may, of course, result from fertilized eggs, as in the honey bee, 
 according to Dickel; who maintains, indeed, that all the eggs 
 laid by the queen bee are fertilized. Parthenogenesis has been 
 recorded as occurring also in a few moths, some Coccidse and 
 many Thysanoptera. 
 
 Paedogenesis." — In Miasfor and some species of Cccido- 
 
 inyia, young are produced l;)y the lar7'a. This extraordinary 
 
 form of parthenogenesis is termed pccdogciicsis, and is limited 
 
 Fig. iJ 
 
 Young paedogenetic larvae of Miastor in the body of the mother larva. Greatly en- 
 larged. — After Pagenstkcher. 
 
 apparently to the family Cecidomyiid^e. The pcedogenetic 
 larvae of Miastor (Fig. i86) develop before the oviducts have 
 appeared and escape by the rupture of the mother. After 
 several successive generations of this kind the resulting larvae 
 pupate and form normal male and female flies. The pupa of 
 a species of Chirononiiis occasionally deposits unfertilized 
 eggs, wdiich develop, however, in the same manner as the fer- 
 tilized eggs of the species. 
 
CHAPTER III 
 
 DEVELOPMENT 
 
 I. Embryology 
 Ovum. — The ovum of an insect, as of any other animal, 
 is a single cell (Fig. 187), with a large nucleus (genninal 
 vesicle) , a large nucleolus, nutritive mat- 
 ter, or yolk {dcutoplasni) , contained in 
 the cytoplasm, and a cell wall {vitelline 
 niemhraue) secreted hy the ovum; the 
 egg-shell, or chorion, is secreted around 
 the o\-um by surrounding ovarian cells. 
 
 Maturation. — As a preparation for 
 fertilization the germinal vesicle divides 
 twice, forming two polar bodies, and as 
 the first of these bodies may itself divide, 
 there result iouv cells ; three of these, 
 however — the polar bodies — are minute 
 and rudimentary. 
 
 These phenomena of ovogenesis are 
 paralleled in the development of the sper- 
 matozoa, or speriuafogeuesis; for the pri- 
 mary spennafocyfe gives rise to two sec- 
 ondary spermatocytes, and these to four 
 spermatids, each of which forms a sper- 
 matozoon. 
 
 By means of this maturation process 
 the number of chromosomes in the egg- 
 nucleus is reduced to half the number 
 normal for sonmtic cells (body cells as 
 distinguished from germ cells). A sim- 
 ilar reduction occurs also during the de- 
 velopment of the spermatozoon, and when sperm-nucleus and 
 
 146 
 
 Sagittal section of egg 
 of fly, Musca, in process 
 of fertilization, c, cho- 
 rion; d, dorsal; in, mi- 
 cropyle, with gelatinous 
 exudation; p, male and 
 female pronuclei, before 
 union; pb, polar bodies; 
 pr, peripheral proto- 
 plasm; r, ventral; vt, 
 vitelline membrane; y, 
 yolk. — After Henking 
 and Blochmann. 
 
DEVELOPMENT 147 
 
 cgg-iiuc!cus unite, the resulting- nucleus contains the normal 
 number of chromosomes. The meaning- of these reduction 
 phenomena — highly important from the standpoint of heredity 
 — is a much debated subject. 
 
 Fertilization. — As the eggs pass through the vagina, they 
 are capable of being fertilized by spermatozoa, previously 
 stored in the seminal receptacle. Through the inicropylc of 
 the chorion one or more spermatozoa enter and a sperm- 
 nucleus unites with the eg-g-nucleus to form what is known as 
 the segiiirnfafioti mtclriis. Through this union of nuclear 
 
 Fig. 1 88. 
 
 Equatorial section of egg of a beetle. Clytra Itriiiisciila. b. blastoderm; g, germ 
 band; y, yolk granule; yc, yolk cell. — After Lecaillon. 
 
 substances the qualities of the two parents are combined in the 
 offspring-. Needless to say. the minute details of the process 
 of fertilization are of the highest biological importance. 
 
 Blastoderm. — In an arthropod ovum the yolk occupies a 
 central position {ccntrolccithal type), being enclosed in a thin 
 layer of protoplasm. From the segmentation nucleus just 
 mentioned are derived many nuclei, some of which migrate 
 outward with their attendant protoplasm to form with the 
 original peripheral protoplasm a continuous cellular layer, the 
 blastoderm (Fig. i88). 
 
148 
 
 ENTOMOLOGY 
 
 Germ Band. — The blastoderm, at first of uniform thick- 
 ness, becomes thicker in one region, by cell multiplication, 
 forming the genu baud {primitive streak, etc.) ; this appears 
 in surface view as an o^'al or elongate area, denser than the 
 remaining blastoderm, with which it is, of course, continuous. 
 
 Fig. 1 89. 
 
 »^£fe 
 
 . ransverse sectic 
 
 of germ band of Clytra at gastrulation. 
 layer. — After Lecaillon. 
 
 g, germ band; 
 
 Gastrulation. — The germ band next infolds along the me- 
 dian line, appearing in cross section, as in Fig. 189; the 
 two lips of the median groove close together over the inva- 
 ginated portion and form an outer layer, or ectoderm (Fig. 
 igo), while the invaginated portion spreads out as an inner 
 
 Fig. 190 
 
 Transverse section of germ layers 
 and amnion folds of Clytra. a, am- 
 nion; e, ectoderm; i, inner layer 
 (meso-entoderm) : 5, serosa. — Original, 
 based on Lecaillon's figures. 
 
 Transverse section of germ layers and 
 embryonal membranes of Clytra. a, am- 
 nion; ac, amnion cavity; e, ectoderm; i, 
 inner layer (meso-entoderm) ; s, serosa. 
 — After Lecaillon. 
 
 layer, which is destined to form two layers, known respectively 
 as entoderm and mesoderm. This formation of two primary 
 
 tioii; it is an important stage in the development of all eggs, 
 and among insects several variations of the process occur. 
 Amnion and Serosa. — ^Meanwhile, the blastoderm has been 
 
DEVELOPMENT 
 
 149 
 
 folding over tlie germ band from either side, as shown in Fig. 
 190, and at length the two' folds meet and unite to form two 
 membranes (Fig. 191). namely, an inner one, or amnio)!, and 
 an outer one, or serosa. 
 
 Fig. 192. 
 
 .:^;?^^^. „. •-'''.:■■": ''h.. 
 
 lif' 
 
 WM 
 
 Germ band of a beetle, Mdasoina. 
 B, with oral segments demarkated : C 
 dominal segments. — After Grablr. 
 
 three successive stages. A, unsegmented; 
 th three oral, three thoracic and two ab- 
 
 Segmentation and Appendages. — On the germ band, 
 which represents the ventral part of the future insect, the body 
 segments are marked off by 
 transverse grooves (Figs. 
 192, 194) ; this segmentation 
 beginning usually at the an- 
 terior end of the germ band 
 and progressing backward. 
 Furthermore, an anterior in- 
 folding occurs (Fig. 193), 
 forming the stoiiiodcruni, 
 from which the mouth, 
 pharynx, oesophagus and other parts of the fore gut are to 
 arise; a similar, but posterior invagination, or proctodeum 
 
 s ' ^ g 
 
 Diagrammatic sagittal section of 
 hymenopterous egg to show stomodaeal 
 is) and proctodaeal (/>) invaginations 
 of the germ band {g). — .\fter Graber. 
 
150 ENTOMOLOGY 
 
 (Fig\ 193), is the beginning, or fuudauicut, of the hind gut. 
 At the anterior end of the germ band is a pair of large 
 proccphalic lobes (Figs. 192, 194). which eventuahy bear the 
 lateral eyes, and immediately behind these are the fundaments 
 of the antenncT. The fundaments of the primary paired ap- 
 pendages are out-pocketings of the ecto- 
 iG. 194. dermal germ band, and at first antennae, 
 
 C"^''^^ month parts and legs are all alike, except 
 
 N^ i in their relative positions. Behind the 
 
 a.._ y->r *-3y- i antennae (in Thysanura and Collembola 
 
 .O-I-IOl— '" at least) appears a pair of rudimentary 
 
 ■" '"^ appendages (Fig. 194, ;") which are 
 " - thought to represent the second antennae 
 • 2 of Crustacea ; instead of developing, they 
 
 yO.-4X4--t-— f^ disappear in the embryo or else persist in 
 ^;jlJJj?^;— a^ the adult as mere rudiments. In front of 
 
 -'^Hf'^' ^ these transitory intercalary appendages is 
 
 -^f^" " ^ the mouth-opening, above which the 
 
 31-^^ '^ labrum and clypeus are already indicated 
 -.^.? 2ll " ^"^ ^^y '^ single, median evagination. Behind 
 
 '^-.... pf. the mouth the mandibles, maxillae and 
 
 labium are represented by three pairs of 
 
 \'entral aspect of germ 
 
 band of a coiiemboian, fuudameuts, and iu Thysanura and Col- 
 t:™:, . :XaMLi„:, >embola a fourth pa,r is present to form 
 appendages; i, intercalary the superliuguje (Fig. 195, sl) , alrcadv rc- 
 
 appendage; /, labrum; li, ^ . 
 
 left labial appendage; fcrred to. A cxt lu ordcr are the three 
 "n "l""'^'^'"' /"■!'' ,T' pairs of thoracic legs (Fig. 194) and then, 
 
 illa; p, procephalic lobe: "^ o \ o ^^ / 
 
 pr, proctodaeum; t^-t^ in many cascs, paired abdominal appen- 
 
 thoracic legs. , ,„. ^ . . . 
 
 dages (rigs. 194, 196), indicating an 
 ancestral myriopod-like condition ; some of these abdominal 
 limbs disappear in the embryo but others develop into abdomi- 
 nal prolegs (Lepidoptera and Tenthredinidae), external genital 
 organs (Orthoptera, Hymenoptera. etc.) or other structures. 
 The study of these embryonic fundaments sheds much light 
 upon the morpholog}^ of the appendages and the subject of 
 segmentation. 
 
DEVELOPMENT I 51 
 
 Two Types of Germ Bands. — The g-erm l^and described 
 above belongs to the simple oz'crgroii'ii type, exemplified in 
 Clytra, in which the germ band retains its original posi- 
 tion and the amnion and serosa arise by a process of over- 
 growth (Figs. 190, 191), as distinguished from the invaginated 
 type, illustrated in Odonata, in which the germ band inva- 
 ginates into the egg, as in Fig. 197, until the ventral surface 
 
 Anterior aspect of embryonal mouth parts of a collembolan, Anurida maritima. a, 
 antenna; /, labrum; Ig, prothoracic leg; li, left fundament of labium; In, lingua; m, 
 mandible; in.r, maxilla; p, maxillary palpus; si, superlingua. — After Folsom. 
 
 of the embryo becomes turned around and faces the dorsal side 
 of the egg. In this event, a subsequent process of revolution 
 occurs, by means of which the ventral surface of the embryo 
 resumes its original position (Fig. 198). 
 
 Dorsal Closure. — As was said, the germ band forms the 
 ventral part of the insect. To complete the general form of 
 the body the margins of the germ band extend outward and 
 upward (Fig. 199) until they finally close over to form the 
 dorsal wall of the insect. Besides this simple method, how- 
 ever, there are several other ways in which the dorsal closure 
 may be effected. 
 
 Nervous System. — Soon after gastrulation. the ventral ner- 
 vous system arises as a pair of parallel cords from cells (Fig. 
 
ENTOMOLOGY 
 
 Fig. 196. 
 
 200, ;/) which have been derived by direct prohferation from 
 those of the germ band, and are therefore ectodermal in origin. 
 This primitive double nerve cord l^ecomes constricted at inter- 
 vals into segments, or iicuromercs, which correspond to the 
 segments of the germ band. Each nenromere consists of a 
 pair of primitive ganglia, and these 
 are connected together by paired 
 nerve cords, which later may or 
 may not unite into single cords ; 
 moreover, some of the ganglia 
 finally unite to form compound 
 ganglia, such as the brain and the 
 subcesophageal ganglion. In front 
 of the oesophagus (Fig. 55) are 
 three neuromeres : ( i ) pvotoccrc- 
 bnuii, which is to bear the com- 
 pound eyes ; (2) deutoccrcbniui, or 
 antennal neuromere ; ( 3 ) trifoccrc- 
 bruui, which belongs to the seg- 
 ment which bears the rudimentary 
 intercalary appendages spoken of 
 above. Behind the oesophagus are, 
 at most, four neuromeres, namely 
 and in order, mandihnlar, siipcr- 
 liiigual (found only in Collembola 
 as yet), maxillary and labial. 
 Then follow the three thoracic gan- 
 glia and ten (usually) abdominal 
 ganglia. The first three neuro- 
 meres always unite together to 
 form the brain, and the next four 
 ( always three ; but four in Col- 
 lembola and perhaps other insects), to form the subceso- 
 phageal ganglion. Compound ganglia are frequently formed 
 also in the thorax and abdomen by the union of primitive 
 
 Embryo of CEcanthus, ventral 
 aspect. a, antenna; a>-a^, ab- 
 dominal appendages; e, end of 
 abdomen; /, labrum; //, left 
 fundament of labium; Ip, labial 
 palpus; t^-P, thoracic legs; m, 
 mandible; mp, maxillary palpus; 
 mx, maxilla; p, procephalic lobe; 
 pr, proctodaeum. — After Ayers. 
 
DEVELOPMENT 
 
 153 
 
 Tracheae. — The trachea? l)ej;-in as paired invaginations of 
 the ectoderm {V\g. 201. /) ; these simple pockets elongate and 
 
 Diagrammatic sagittal sections to illustrate invagination of germ band in Calop- 
 tcryx. a, anterior pole; ac, amnion cavity; am, amnion; b, blastoderm; d, dorsal; 
 g, germ band; h, head end of germ band; p, posterior pole; s, serosa; v, ventral; y, 
 yolk. — After Brandt. 
 
 Fig'. 198. 
 
 Diagrammatic sagittal sections to illustrate revolution of Caloptcryx 
 antenna; am, amnion; /, labium; l^-P, thoracic legs; m, mandible; mx, 
 serosa. — After Br.\ndt. 
 
 ;mbryo. 
 maxilla; 
 
154 
 
 ENTOMOLOGY 
 
 unite to form the main lateral trunks, from which arise the 
 countless branches of the tracheal system. 
 
 Mesoderm. — From the inner layer which was derived 
 from the germ band by gastrulation (Figs. 189-191) are 
 formed the important germ layers known as mesoderm and 01- 
 
 FiG. 199. 
 
 Diagrammatic transverse sections to illustrate formation of dorsal wall in a beetle, 
 Lcptinofarsa. a, amnion (breaking up in C); g, germ band; s, serosa. — After 
 Wheeler, from the Journal of Morphology. 
 
 todcrm. Most of the layer becomes mesoderm, and this splits 
 on either side into chambers, or ca:lom sacs (Fig. 200, c) , a pair 
 to each segment. In Orthoptera these coelom sacs are large 
 and extend into the embryonic appendages, but in Coleoptera, 
 Lepidoptera and Hymenoptera they are small. These sacs 
 
 Fig. 200. 
 
 Tan-sverse section of germ layers of Clytra. c, ccelom sac; n, 
 neuroblasts (primitive nervous cells). — After Lecaillon. 
 
 may share in the formation of the definite body-cavity, though 
 the last arises independently, from spaces that form between 
 the yolk and the mesodermal tissues. From the coelom sacs 
 develop the muscles, fat-body, dorsal vessel, blood corpuscles, 
 ovaries and testes ; the external sexual organs, however, as 
 well as the vagina and ejaculatory duct, are ectodermal in 
 orig-in. 
 
DEVELOPMENT 
 
 155 
 
 Entoderm. — At its anterior and posterior ends, the inner 
 layer just referred to ^ives rise to a mass of cells which are 
 
 Fig. 201. 
 
 Transverse section of abdomen of Clytra embryo at an advanced stage of develop- 
 ment, a, appendage; e, epithelium of mid intestine; g, ganglion; m, Malpighian tube; 
 mi, muscular layer of mid intestine; ms, muscle elements; my, mesenchyme (source 
 of fat-body); s, sexual organ; t, tracheal invagination. — After Lec-mllon. 
 
 Fig. 202. 
 
 destined to form the mcscntcron, from which the mid intestine 
 
 develops. One mass is adjacent to the blind end of the stomo- 
 
 d;eal im-agination and the other to that of 
 
 the proctodajal in-folding. The two 
 
 masses become U-shaped (Fig. 202), and 
 
 the lateral arms of the two elongate and 
 
 join so that the entodermal masses become 
 
 connected by two lateral strands of cells : 
 
 by overgrowth and undergrowth from 
 
 these lateral strands a tube is formed 
 
 which is destined to Ijecome the stomach, 
 
 and by the disappearance of the partitions 
 
 that separate the mesenteron from the 
 
 stomodseum at one end and from the proc- 
 
 todseum at the other end. the continuity 
 
 of the alimentary canal is established. 
 
 The fore and the hind gut. then, are 
 
 ectodermal in origin, and the mid gut 
 
 entodermal. 
 
 formation 
 of entoderm in Leptino- 
 tarsa. e, e, entodermal 
 masses; m, mesoderm. — 
 After Wheeler. 
 
156 
 
 ENTOMOLOGY 
 
 2. External Metamorphosis 
 Metamorphosis. — One of the most striking phenomena of 
 insect Hfe is expressed by the term inctamorphosis, which 
 means conspicuous change of form after birth. The tgg of 
 a butterfly produces a larva; tliis eats and grows and at length 
 becomes a pupa; Avhich, in turn, develops into an imago. 
 These stages are so different (Fig. 27) that witliout experi- 
 
 FiG. 203. 
 
 Cyllcne pi. 
 
 A, larva; B, pnpa; C, 
 
 ence one could not know that they pertained to the same 
 individual. 
 
 Holometabola. — The more specialized insects, namely, 
 Neuroptera. Alecoptera. Trichoptera, Lepidoptera, Coleoptera 
 (Fig. 203), Diptera (Figs. 204, 29), Siphonaptera (Fig. 30) 
 and Hymenoptera (Fig. 280), undergo this indirect, or com- 
 plete,^ metamorphosis, involving profound changes of form 
 and distinguished by an inactive pupal stage. These insects 
 are grouped together as Holometabola. 
 
 Larvae receive such popular names as "' caterpillar " (Lepi- 
 
 ^ These terms, though somewhat misleading in impHcation, are cur- 
 rently used. 
 
DEVELOPMENT 
 
 157 
 
 doptera), " stuI) " (Coleoptera ), and " maj^got " (Diptera), 
 while the ]wpa of a moth or l)ullerlly (especiahy the latter) 
 is called a " chrysalis." 
 
 Heterometabola, — In a o-rassh()])per, as contrasted with a 
 hnttertlv, the imago, or adult, is essentially like the young at 
 birth, except in having wings and mature reproductive organs, 
 and the insect is active throughout life; hence the metamor- 
 phosis is termed direct, or iiicoinplclr. This type of trans- 
 
 Phormia rcgiua. A, larva; B 
 
 formation, without a true pupal period, is characteristic of 
 the more generalized of the metamorphic insects, namely, 
 Orthoptera, Platyptera, Plecoptera, Ephemerida (Fig. 19), 
 Odonata (Fig. 20), Thysanoptera and Hemiptera (Fig. 205). 
 These orders constitute the group Heterometabola. ^^'ithin 
 the limits of the group, however, various degrees of meta- 
 morphosis occur ; thus Plecoptera, Ephemerida and Odonata 
 undergo considerable change of form ; a resting, or cpiiescent, 
 period may precede the imaginal stage, as in Cieada (Fig. 
 
158 
 
 ENTOMOLOGY 
 
 206) ; while male Coccidc-e have what is essentially a complete 
 metamorphosis. In fact, the various kinds of metamorphosis 
 
 Fig. 20= 
 
 Six successive instars of the squash bug, Anasa tristis. x 2. 
 
 Fig. 206. 
 
 Cicada tibiccn. A, imago emerging from nymphal skin; B, the cast ski 
 C, imago. Natural size. 
 
 grade into one another in such a way as to make their classifi- 
 cation to some extent arbitrary and inadequate. 
 
DEVELOPMENT 
 
 159 
 
 As there is no distinction ])etween larva and pnpa in most 
 heterometabolous insects, it is customary to use the term 
 n\inph durins;- the interval between egg- and inia.^o. 
 
 Ametabola. — The most generalized insects, Thysanura and 
 Collembola, develop to sexual maturity without a metamor- 
 phosis ; the form at hatching is retained essentially throughout 
 life, there are no traces of wings even in the embryo, and there 
 is no change of habit. These two orders form the group 
 Ametabola. All other insects have a metamorphosis in the 
 broad sense of the term, and are therefore spoken of as Mctab- 
 ola. In this we follow Packard, rather than Brauer, who 
 uses a somewhat different set of terms to express the same 
 ideas. 
 
 Stadium and Instar. — During the growth of every insect, 
 the skin is shed periodically, and with each moult, or ecdysis, 
 the appearance of the insect changes more or less. The inter- 
 vals between the moults are termed stages, or stadia. To 
 designate the insect at any particular stag'e, the term instar 
 has been proposed and is growing in favor ; thus the insect at 
 hatching is the first instar, after the first moult the seeond 
 instar, and so on. 
 
 Egg. — The eggs of insects are exceedingly diverse in form. 
 Commonly they are more or less spherical, oval, or elongate, 
 but there are innumerable special forms, some of which are 
 
 Eggs of various insects. A, butterfly, Polygonia intcrrogationis; B, house fly, 
 Miisca domestica; C, chalcid, Bruchophagus funebris; D, butterfly, Papilio troiliis; E, 
 midge, Cecidomyia trifolii; F, hemipteron, Trifhleps insidiosus; G, hemipteron, 
 Podisiis spinosus; H, fly, Drosophila ampelophila. Greatly magnified. 
 
[6o 
 
 ENTOMOLOGY 
 
 quite fantastic, 
 in Fig. 207. 
 
 Fig. 208. 
 
 Three eggs of the 1 
 rap<T. Greatly magnified 
 scale. 
 
 Something of the variety of form is shown 
 As regards size, most insect eggs can be 
 distinguished by the 
 naked eye ; many of 
 them tax the vision, 
 however, for example. 
 the ehiptical eggs of 
 Cccidoiiiyia Icgiiiiiiiii- 
 cola, which are but 
 .300 mm. in length 
 and .075 mm. in 
 width ; the oval eggs 
 of the cccropia moth, 
 
 ihbage butterfly, Pieris 
 but all drawn to same 
 
 Fig. 209. 
 
 on the other hand, are as long as 3 mm. 
 
 The egg-shell, or cJiorioii, secreted 
 around the ovum by cells of the ovarian 
 follicle, may be smooth but is usually 
 sculptured, frequently with ridges 
 which, as in lepidopterous eggs, may 
 serve to strengthen the shell. The 
 ornamentation of the egg-shell is often 
 exquisitely beautiful, though the par- 
 ticular patterns displayed are probably 
 of no use, being incidentally produced 
 as impressions from the cells which 
 secrete the chorion. Variations of 
 form, size and pattern are frequent in 
 eggs of the same species, as appears in 
 Fig. 208. 
 
 Always the chorion is penetrated by 
 one or more openings, constituting- the 
 micro pylc, for the entrance of sperma- 
 tozoa. 
 
 As a rule, the eggs when laid are accompanied by a fluid of 
 some sort, which is secreted usually by a cement gland or 
 glands, opening into the vagina. This fluid commonly serves 
 
 Chrysopa. laying eggs. 
 Slightly enlarged. 
 
DEVELOPMENT l6l 
 
 to fasten the eg-gs to appropriate objects, such as food plants, 
 the skin of other insects, the hairs of mammals, etc. ; it may 
 form a pedicel, or stalk, for the egg. as in Chrysopa ( h'ig. 
 209) ; may surrountl the eggs as a gelatinous envelope, as in 
 caddis Hies, dragon tlies. etc. ; or may form a capsule enclosing 
 the eggs, as in the cockroach. 
 
 The number of eggs laid by one female differs greatly in 
 different species and varies considerably in different individ- 
 uals of the same species. Some of the fossorial wasps and 
 bees lay only a dozen or so and some grasshoppers two or three 
 dozen, while a (jueen honey bee may lay a million. Two 
 females of the beetle Friomis laticollis had, respectively, 332 
 and 597 eggs in the abdomen (Mann). A. A. Girault gives 
 the following numbers of eggs per female, from an examina- 
 tion of twenty egg-masses of each species : 
 
 Maximum. Minimum. Average. 
 
 Thyridoptcryx cplicmcrafoniiis 1076 753 941 
 
 Clisiocampa aiiicricaiia 466 313 375-5 
 
 Chionaspis ftirfura 84 ^^ 66.5 
 
 Hatching. — Many larv?e, caterpillars for example, simply 
 eat their way out of the egg-shell. Some maggots rupture 
 the shell by contortions of the body. Some larvae have spe- 
 cial organs for opening the shell ; thus the grub of the Colo- 
 rado potato beetle has three pairs of hatching spines on its 
 body (Wheeler) and the larval tiea has on its head a tempo- 
 rary knife-like egg-opener (Packard). The process of hatch- 
 ing varies greatly according to the species, but has received 
 \ery little attention. 
 
 Larva. — Although larvae, generally speaking, differ from 
 one another much less than their imagines do. they are easily 
 referable to their orders and usually present specific dift'er- 
 ences. Larvae that display individual adaptive characters of 
 a positive kind (Lepidoptera, for example) are easy to place, 
 but larvae with negative adaptive characters (many Diptera 
 and Hymenoptera) are often hard to identify. 
 1 2 
 
i6; 
 
 ENTOMOLOGY 
 
 Thysanuriform Larvae. — Two types of larvae are recog- 
 nized by Braiier, Packard and other authorities: fhysanuri- 
 fonn and cntcifonii; respectively generahzed and speciahzed 
 in their organization. The former term is apphed to many 
 larvae and nymphs (Fig. 210, C, D) on account of their resem- 
 blance to Thysanura, of which Cauipodea and Lepisma are 
 
 Fig. 210. 
 
 Types of larvK. A, B, Thysanura; C, D, thysanuriform nymphs; E-I, cruciform 
 larvae. A, Campodea; B, Lepisma; C, perlid nymph (Plecoptera) ; D, Libellula 
 (Odonata) ; E, Tenthrcdopsis (Hymenoptera) : F, Lachnosterna (Coleoptera) ; G, 
 Melanotus (Coleoptera); H, Boinbus (Hymenoptera); /, Hypoderma (Diptera). 
 
 types. The resemblance lies chiefly in the flattened form, hard 
 plates, long legs and antennae, caudal cerci, well-developed man- 
 dibulate mouth parts, and active habits, with the accompanying 
 sensory specializations. These characteristics are permanent 
 in Thysanura, but only temporary in metamorphic insects, and 
 their occurrence in the latter forms may properly be taken to 
 indicate that these insects have been derived from ancestors 
 which were much like Thysanura. 
 
 Thysanuriform characters are most pronounced in nymphs 
 of Blattidae, Forficulidae, Perlidae, Ephemeridae and Odonata, 
 but occur also in the larvae of some Neuroptera (Mantispa) 
 and Coleoptera (Carabidae and Meloidae). These primitive 
 characters are gradually overpowered, in the course of larval 
 evolution, by secondary, or adaptive, features. 
 
DEVELOPMENT 
 
 163 
 
 Eruciform Larvae. — The prevalent type of lar\a among 
 holometabolous insects is tlie cruciform (Fig. 210, £-/), illus- 
 trated by a cater])illar or a maggot. Here the body is cylin- 
 drical and often lleshy ; the integument weak; the legs, anten- 
 ^a^ cerci, and mouth parts reduced, often to disappearance; 
 the habits sedentary and the sense organs correspondingly re- 
 duced. These characteristics are interpreted as being results of 
 partial or entire disuse, the amount of reduction being propor- 
 tional to the degree of inactivity. Extreme reduction is seen 
 in the maggots of parasitic and such other Diptera as, secur- 
 ing their food with almost no exertion, are simple in form, 
 thin-skinned, legless, with only a mere vestige of a head and 
 with sensory powers of but the simplest kind. 
 
 Transitional Forms. — The eruciform is clearly derived 
 from the thysanuriform type, as Brauer and Packard have 
 shown, the continuity between the two types being established 
 by means of a complete series of intermediate stages. The 
 
 Fig. 211 
 
 Mantispa. A, larva at hatching — thysanuriform; B, same larva just before first 
 moult — now becoming enicifonn. C, imago, the wings omitted; D, winged imago, 
 slightly enlarged.—^ and B after Br.'vuer; C and D after Emerton, from Packard's 
 Text-Book of Entomology, by permission of the Macmillan Co. 
 
 beginning of the eruciform type is found in Neuroptera, where 
 the campodeoid sialid larva assumes a quiescent pupal condi- 
 tion. The key to the origin of the complete metamorphosis, 
 
164 ENTOMOLOGY 
 
 involving the ernciform condition, Packard finds in the neu- 
 ropterons genus Mantispa (Fig. 211), the first larva of which 
 is truly campodea-form and active. Beginning a sedentary 
 life, however, in. the egg-sac of a spider, it loses the use of its 
 legs and the antenn?e become partly aborted, before the first 
 moult. In Packard's words, " Owing to this change of hab- 
 its and surroundings from those of its active ancestors, it 
 changes its form, and the fully grown larva becomes cylin- 
 drical, with small slender legs, and, owing to the partial disuse 
 of its jaws, acquires a small, round head." Meloiclje (Fig. 
 217) afiford other excellent examples of the transition from 
 the thysanuriform to the cruciform condition during- the life 
 of the individual. 
 
 Thysanuriform characters become gradually suppressed in 
 favor of the cruciform, until, in most of the highly developed 
 orders (Mecoptera, Trichoptera, Lepidoptera, Diptera, Si- 
 phonaptera and Hymenoptera) , they cease to appear, except 
 for a few embryonic traces — an illustration of the principle of 
 " acceleration in development." 
 
 Growth. — The larval period is pre-eminently one of growth. 
 In Heterometabola, growth is continuous during- the nymphal 
 stage, but in Holometabola this important function becomes 
 relegated to the larval stage, and pupal development takes 
 place at the expense of a reserve supply of food accumulated 
 by the larva. 
 
 The rapidity of larval growth is remarkaljle. Trouvelot 
 found that the caterpillar of Tclca polyphcmus attains in 56 
 days 4,140 times its original weight (1/20 grain), and has 
 eaten an amount of food 86,000 times its primitive weight. 
 Other larvc-e exceed even these figures ; thus the maggot of a 
 common flesh fly attains 200 times its original weight in 24 
 hours. 
 
 Ecdysis. — The exoskeleton, unfitted for accommodating 
 itself to the growth of the insect, is periodically shed, and 
 along with it go not only such integumentary structures as 
 hairs and scales, but also the chitinous lining, or intima, of 
 
DEVELOPMENT 165 
 
 the stom(Hl;cuin. ])n)ct()(Ia'iini, trachce, inteoiimentary siands, 
 etc. The process of nioiiltiiii;-, or ccdysis, in caterpillars is 
 briefly as follows. The old skin becomes detached from tlie 
 body l)y an interveninj^- fluid of hypodermal orio-in; the skin 
 dries, shrinks, is ])nshed backward by the contractions of the 
 larva, and at lenoth splits near the head, frequently under the 
 neck ;, tln-oui^li this split appear the new head and thorax, and 
 the old skin is worked back toward the tail until the larva is 
 freed of its cwirz'icc. The details of tlie process, however, are 
 by no means simple. Ecdysis is probably something- besides 
 a pro\-ision for growth, for Collembola continue to moult long 
 after growth has ceased, and the winged May fly sheds its 
 skin once after emergence. The meaning of this is not 
 known, though perhaps ecdysis has an excretory importance 
 in the case of Collembola, which are exceptional among in- 
 sects in ha\ing no Malpighian tubes. 
 
 Number of Moults.— The frequency of moulting differs 
 greatly in different orders of insects. Acridiidre ha\-e five 
 moults; Lepidoptera usually four or five, but often more, as 
 in Isia (Pyrrharctia) Isabella, which moults as many as ten 
 times (Dyar) ; Musca doniestica has three (Packard); the 
 honey bee probably six (Cheshire) ; and the^seventeen-year 
 locust about twenty-five or thirty (Riley). Packard suggests 
 that cold and lack of food during hibernation in arctians (as 
 /. isabdla ) and partial starvation in the case of some beetles, 
 cause a great number of moults by preventing grow^th, the 
 hypodermis cells meanwhile retaining their activity. 
 
 The appearance of the insect often changes greatly with 
 each moult, particularly in caterpillars, in which the changes 
 of coloration and armature may have some phylogenetic sig- 
 nificance, as Weismann has attempted to show in the case of 
 sphingid larvae. 
 
 Adaptations of Larvae. — Larva; exhibit innumerable con- 
 formities of structure to environment. The greatest variety 
 of adaptive structures occurs in the most active larva?, such as 
 predaceous forms, terrestrial or aquatic. These have well- 
 
1 66 ENTOMOLOGY 
 
 developed sense organs, excellent powers of locomotion, spe- 
 cial protective and aggressive devices, etc. In insects as a 
 whole, the environment of the larva or nymph and that of the 
 adult are very different, as in the dragon fly or the butterfly, 
 and the larvae are modified in a thousand ways for their own 
 immediate advantage, without any direct reference to the 
 needs of the imago. 
 
 The chief purpose, so to speak, of the larva is to feed and 
 grow, and the largest modifications of the larva depend upon 
 nutrition. Take as one extreme, the legless, headless, fleshy 
 and sluggish maggot, embedded in an abundance of food, and 
 as the other extreme the active and " wide-awake " larva of 
 a carabid beetle, dependent for food upon its own powers of 
 sensation, locomotion, prehension, etc., and obliged meanwhile 
 to protect or defend itself. Between these extremes come 
 such forms as caterpillars, active to a moderate degree. The 
 great majority of larval characters, indeed, are correlated with 
 food habits, directly or indirectly; directly in the case of the 
 mouth parts, sensory and locomotor organs, and special struc- 
 tures for obtaining special food ; indirectly, as in respiratory 
 adaptations and protective structures, these latter Ijeing numer- 
 ous and varied. 
 
 Larvae that live in concealment, as those that burrow in the 
 ground or in plants, have few if any special protective struc- 
 tures ; active larvre. as those of Carabidse, have an armor-like 
 integument, but owe their protection from enemies chiefly to 
 their powers of locomotion and their aversion to light {nega- 
 tive phototropisin) ; various acjuatic nymphs (Zaitha, Odonata ) 
 are often coated with mud and therefore difiicult to distin- 
 guish so long as they do not mo\'e; caddis worms are con- 
 cealed in their cases, and caterpillars are often sheltered in a 
 leafy nest. There is no reason to suppose that insects conceal 
 themselves consciously, however, and one is not warranted in 
 speaking of an instinct for concealment in the case of insects — 
 since everything goes to show that the propensity to hide, 
 though advantageous indeed, is simply a reflex, inevitable. 
 
DEVELOPMENT 1 67 
 
 negative reaction to light (iicgatk'c f^Jioloiropisni) or a positive 
 reaction to contact {/^ositrrc iliigiiiofropisin) . 
 
 Exposed, sedentary larv;e. as those of many Lepidop- 
 tera and Coleoptera, often exhil)it highly developed protective 
 adaptations. Caterpillars may be colored to match their sur- 
 ronndings and may resemble twigs, bird-dung, etc. ; or larv?e 
 may possess a disagreeable taste or repellent fluids or spines, 
 these odious qualities being frequently associated with warn- 
 ing colors. 
 
 Larvae need protection also against adverse climatal condi- 
 tions, especially low temperature and excessive moisture. 
 The thick hairy clothing of some hibernating caterpillars, as 
 Isia (Pyrrliarcfia) Isabella, doubtless serves to mollify sudden 
 changes of temperature. Naked cutworms hibernate in well- 
 sheltered situations, and the grubs of the common " May 
 beetles," or " June bugs," burrow down into the ground below 
 the reach of frost. Ordinary high temperatures have little 
 effect upon larwx, except to accelerate their growth. Exces- 
 sive moisture is fatal to immature insects in general — conspicu- 
 ously fatal to the chinch bug. Rocky ^Mountain locust, aphids 
 and sawfly larvae. The effect of moisture may be an indirect 
 one, however; thus moisture may favor the development of 
 bacteria and fungi, or a heavy rain may be disastrous not only 
 by drowning larvae, but also by washing them off their food 
 plants. 
 
 As a result of secondary adaptive modifications, larvse 
 may differ far more than their imagines. Thus Plafygastcr in 
 its extraordinary first larval form (Fig. 218) is entirely unlike 
 the larvae of other parasitic Hymenoptera, reminding one, 
 indeed, of the crustacean Cyclops rather than the larva of an 
 insect. As Lubbock has said, the characters of a larva depend 
 
 ( 1 ) upon the group of insects to which the larva belongs and 
 
 (2) upon the special environment of the larva. 
 
 Pupa. — The term pupa is strictly applicable to holometabo- 
 lous insects only. Most Lepidoptera and many Diptera have 
 an obtect pupa (Fig. 212), or one in which the appendages 
 
i68 
 
 ENTOMOLOGY 
 
 Fig. 212. 
 
 Obtect pupa of milk- 
 weed butterfly, Anosia 
 ple.vippus, natural size. 
 
 and body are compactly united ; as distinguished from the free 
 pupa of Neuroptera, Trichoptera, Coleoptera and others, in 
 which the appendages are free (Fig. 203). This distinction, 
 however, cannot always be drawn sharply. Diptera present 
 also the coarctatc type of pupa (Fig. 
 204), in which the pupa remains en- 
 closed in the old larval skin, or pnpa- 
 riiim. 
 
 Pupal characters, though doubtless of 
 great adaptive and phylogenetic signifi- 
 cance, have received but little attention. 
 Lepidopterous pup?e present many puz- 
 zling characters, for example, an eye- 
 like structure (Fig. 213) suggesting 
 an ancestral active condition, such as 
 still occurs among heterometabolous in- 
 sects. 
 Pupation of a Caterpillar, — The process of pupation in 
 a caterpillar has been carefully observed by Riley. The cater- 
 pillar of the milkweed butterfly (PI. i. A) spins a mass of 
 silk in which it entangles its suranal plate and anal prolegs 
 and then hangs downward, bending up 
 the anterior part of the body (B), which 
 gradually becomes swollen. The skin 
 of the caterpillar splits dorsally, from 
 the head backward, and is worked back 
 toward the tail (C and D) by the con- 
 tortions of the larva. 
 
 The way in which the pupa becomes at- 
 tached to its silken support is rather com- 
 plex. Briefly, while the larval skin still 
 retains its hold on the support, the posterior end of the pupa 
 is withdrawn from the old integument and by the vigorous 
 whirling and twisting of the body the hooks of the terminal 
 cremaster of the pupa are entangled in the silken support. At 
 first the pupa is elongate (E) and soft, but in an hour or so 
 
 Fig, 
 
 Head of chrysalis of 
 Papilio polyxcnes, to 
 show eye-like structure. 
 Enlarged. 
 
PLATK 1. 
 
 Successive stages in the 
 
 nation of the milkweed caterpillar, Anosin f^lcvippn 
 Natural size. 
 
DEVELOPMENT 
 
 169 
 
 it has contracted, hardened, and assumed its characteristic form 
 and coloration (/•"). 
 
 Pupal Respiration. — Except under special conditions, pupre 
 breathe by means of ordinary abdominal spiracles. Aquatic 
 pupai have special res])iratory org-ans. 
 such as the tracheal filaments of Siiiiu- 
 liuiii (Fig". -230), and the respiratory 
 tubes of Ciilrx (Fig. 229). 
 
 Pupal Protection. — Inactive and 
 helpless, most puprc are concealed in one 
 wav or another from the observation of 
 enemies and are protected from mois- 
 ture, sudden changes of temperature, 
 mechanical shock and other adverse in- 
 fluences. The larv?e of many moths 
 burrow into the ground and make an 
 earthen cell in which to pupate ; a large 
 number of coleopterous larv;e ( Lac Jin o- 
 stcrna, Osmodcrma, Passaliis, Liicaiiiis, 
 etc.) make a chamber in earth or wood, the walls of the cell 
 being strengthened with a cementing fluid or more or less 
 silk, forming a rude cocoon. Silken cocoons are spun by 
 some Xeuroptera ( Chrysopidae, Fig. 214), by Trichoptera 
 (whose cases are essentially cocoons), Lepidoptera, a few Co- 
 leoptera (as CuvcuWonidx, Doiiacia) , some Diptera (as Cecido- 
 myiidse), Siphonaptera, and many Hymenoptera (for exam- 
 ple, Tenthredinid?e, Ichneumonid?e, wasps, bees and some 
 ants). 
 
 The cocoon-making- instinct is most highly developed in 
 Lepidoptera and the most elaborate cocoons are those of Satur- 
 niidse. The cocoon of Saniia cecropia is a tough, w^ater-proof 
 structure and is double (Fig. 215), there being tw^o air spaces 
 around the pupa ; thus the pupa is protected against moisture 
 and sudden changes of temperature and from most birds as 
 well, though the downy woodpecker not infrequently punc- 
 tures the cocoon. S. cecropia binds its cocoon firmly to a 
 
 Cocoon of Clirysopa, 
 after emergence of 
 i m a g o. Slightly en- 
 larged. 
 
70 
 
 ENTOMOLOGY 
 
 twig; Tvopcca luna and Tcica poIypJicnius spin among leaves, 
 and their cocoons (with some exceptions) fah to the ground; 
 Callosainia proiucthca, whose cocoon is covered with a curved 
 leaf, fastens the leaf to the twig with a wrapping of silk, so 
 that the leaf with its burden hangs to the twig throughout the 
 winter. The leaves surrounding cocoons may render them 
 inconspicuous or may serve merely as a foundation for the 
 cocoon. While silk and often a water-proof gum or cement 
 
 Fig. 215. 
 
 Cocoon of Samia cccropia, cut open to show the two silken layers 
 pupa. Natural size. 
 
 id the enclosed 
 
 form the basis of a cocoon, much foreign material, such as bits 
 of soil or wood, is often mixed in ; the cocoons of many com- 
 mon Arctiidae. as Diacrisia z'irgiiiica and Isia isabcUa. consist 
 principally of hairs, stripped from the body of the larva. 
 
 Butterflies have discarded the cocoon, the last traces of 
 which occur in Hesperiidse, which draw together a few leaves 
 with a scanty supply of silk to make a flimsy substitute for a 
 cocoon. Papilionid and pierid pupcT are supported by a silken 
 girdle (Fig. 2y) . and nymphalid chrysalides hang freely sus- 
 pended by the tail (Fig. 212). 
 
 Cocoon-Spinning. — The caterpillar of Tclca polyplicuius 
 " feels with its head in all directions, to disco\-er any leaves 
 to which to attach the fibres that are to give form to the co- 
 coon. If it finds the place suitable, it begins to wind a layer 
 
DEVELOPMENT I/I 
 
 of silk around a Iwii;-, then a fil^re is attached to a leaf near 
 by, and 1)y many times doubling this fibre and making it 
 shorter ever}- time, the leaf is made to approach the twig at 
 the distance necessary to build the cocoon; two or three leaves 
 are disposed like this one, and then fibres are spread between 
 them in all directions, and soon the ov(^id form of the cocoon 
 distinctly appears. This seems to be the most difficult feat 
 for the worm to accomplish, as after this the work is simply 
 mechanical, the cocoon being made of regular layers of silk 
 united by a gummy substance. The silk is distrllnited in zig- 
 zag lines of about one-eighth of an inch long-. When the 
 cocoon is made, the worm will ha\'e mo\-ed his head to and 
 fro, in order to distribute the silk, about two hundred and 
 fifty-four thousand times. After about half a day's work, the 
 cocoon is so far completed that the worm can hardly be dis- 
 tinguished through the fine texture of the wall ; then a gummy 
 resinous substance, sometimes of a light brown color, is spread 
 over all the inside of the cocoon. The larva continues to work 
 
 for four or five days, hardly taking a 
 
 •^ ' ^ •;, '^ Fig. 2i6. 
 
 few mmutes ot rest, and nnally another 
 
 coating is spun in the interior, when Py-'I^ 
 
 the cocoon is all finished and completely Wl p3k 
 
 air tight. The fibre diminishes in thick- ^:^£^ 
 
 ness as the completion of the cocoon liZss^^ 
 
 advances, so that the last internal coat- p~^7 
 
 ing is not half so thick and so strong p^^^^^ 
 
 as the outside ones." (Trouvelot.) ^|^^ 
 
 Emergence of Pupa, — Subterranean if 
 
 pup?e wriggle their way to the surface Subterranean pupa of 
 
 - , , . , ' , . , ^ . Anisota. Enlarged. 
 
 ot the ground, often by the aid of spines 
 
 (Fig. 216) that catch successively into the surrounding soil. 
 These locomotor spines may occur on almost any part of the 
 pupa, but occur commonly on the abdominal segments, as in 
 lepidopterous pupcC ; the extremity of the abdomen, also, bears 
 frequently one or more spinous projections, as in Tipulidae, 
 Carabidse and Lepidoptera, to assist the escape of the pupa. 
 
1/2 ENTOMOLOGY 
 
 These structures are found also in pup?e, as those of Sesiidre, 
 that force their way out of the stems of plants in which the 
 larvK ha^'e lived. The emergence from the cocoon is accom- 
 plished in some cases by the pupa, in others by the imago. 
 Hemerobiidse, Trichoptera and the primitive lepidopteron 
 Eriocephala use the pupal mandibles to cut an opening in the 
 cocoon; while many lepidopterous pupae have on the head a 
 beak for piercing the cocoon, or teeth for rending or cutting 
 the silk. 
 
 Eclosion. — During the last few hours before the emer- 
 gence of a butterfly the colors of the imago develop and may 
 be seen through the transparent skin of the chrysalis (PI. 
 2, A). No movement occurs, however, until several seconds 
 before emergence; then, after a few convulsive movements of 
 the legs and thorax of the imprisoned insect, the pupa skin 
 breaks in the region of the tongue and legs (5), a secondary 
 split often occurs at the back of the thorax, and the butterfly 
 emerges {C-E) with moist body, elongated abdomen and 
 miniature wings. Hanging to the empty pupa case (F), or 
 to some other available support, the insect dries and its wings 
 gradually expand {G, H) through the pressure of the blood. 
 At regular intervals the abdomen contracts and the wings fan 
 the air, and sooner or later a drop or two of a dull greenish 
 fluid (the meconium) is emitted from the alimentary canal. 
 The expansion of the wings takes place rapidly, and in 
 less than an hour, as a rule, they have attained their full 
 size (/). 
 
 T. polyphcmiis is " provided with two glands opening into 
 the mouth, which secrete during the last few days of the pupa 
 state, a fluid which is a dissolvent for the gum so firmly unit- 
 ing the fibres of the cocoon. This liquid is composed in great 
 part of bombycic acid. When the insect has accomplished the 
 work of transformation which is going on under the pupa 
 skin, it manifests a great activity, and soon the chrysalis cover- 
 ing bursts open longitudinally upon the thorax ; the head and 
 legs are soon disengaged, and the acid fluid flows from its 
 
PLATE II. 
 
 Successive stages in the emergence of the milkweed butterfly, Anosia l<lcxlppus, from 
 the clirysalis. Natural size. 
 
DEVELOPMENT 1/3 
 
 mouth, wcttiiii^' ibe inside of the cocoon. The ])r(^cess of ex- 
 cUision from the cocoon lasts for as much as half an hour. 
 The insect seems to be instinctively aware [ ?] that some time 
 is required to dissolve the gum. as it does not make any attempt 
 to open the fibres, and seems to wait with patience this event. 
 \\nien the liquid has fully penetrated the cocoon, the pupa con- 
 tracts its l:)odv, and pressing" the hinder end, which is furnished 
 with little hooks, against the inside of the cocoon, f(jrcibly 
 extends its body ; at the same time the head pushes hard upon 
 the fibres and a little swelling is observed on the outside. 
 These contractions and extensions of the body are repeated 
 many times, and more fluid is added to soften the gum, until 
 under these efforts the cocoon swells, and finally the fibres 
 separate, and out comes the head of the moth. In an instant 
 the legs are thrust out, and then the whole body appears ; not 
 a fibre has been ])roken, they have only been separated. 
 
 " To observe these phenomena, I had cut open with a razor 
 a small portion of a cocoon in which was a living chrysalis 
 nearly ready to transform. The opening made was covered 
 with a piece of mica, of the same shape as the aperture, and 
 fixed to the cocoon with mastic so as to make it solid and air- 
 tight ; through the transparent mica, I could see the move- 
 ments of the chrysalis perfectly well. 
 
 " When the insect is out of the cocoon, it immediately seeks 
 for a suitable place to attach its claws, so that the wings may 
 hang down, and by their own weight aid the action of the 
 fluids in developing and unfolding the very short and small 
 pad-like wings. Every part of the insect on leaving the co- 
 coon, is perfect and with the form and size of maturity, except 
 the pad-like wings and swollen and elongated abdomen, which 
 still gives the insect a worm-like appearance ; the abdomen con- 
 tains the fluids which flow to the wings. 
 
 " \\dien the still immature moth has found a suitable place, 
 it remains quiet for a few minutes, and then the wings are seen 
 to grow very rapidly by the afflux of the fluids from the abdo- 
 men. In about twentv minutes the wings attain their full 
 
174 ENTOMOLOGY 
 
 size, but they are still like a piece of wet cloth, without con- 
 sistency and firmness, and as yet entirely unfit for flight, but 
 after one or two hours they become sufficiently stiff, assuming 
 the beautiful form characteristic of the species." (Trouvelot.) 
 The expansion of the wing is due to blood-pressure brought 
 about chiefly by the abdominal muscles. In the freshly- 
 emerged insect, the two membranes of the wing are corru- 
 gated, and expansion consists in the flattening out of these 
 folds. The wing is a sac, which would tend to enlarge into 
 a balloon-shaped bag, were it not for hypodermal fibers which 
 hold the wing-membranes closely together (Mayer). Samia 
 cccropia also uses a dissolvent fluid; Tropcca hum, PJiilosaniia 
 cyiithia and others cut and force an opening through the cocoon 
 by means of a pair of saw-like organs, one at the base of each 
 front wing. 
 
 Hypermetamorphosis. — In a few remarkable instances, 
 metamorphosis involves more than three stages, owing to the 
 existence of supernumerary larval forms. This phenomenon 
 of hypcniictamorpliosis occurs notably in the coleopterous 
 genera Mcloc, Epicauta, Sitaris, RhipipJiorus and Sfylops, in 
 male Coccid?e and several parasitic Hymenoptera. 
 
 In Mcloc, as described by Riley, the newly-hatched larva 
 (triunguliii form) is active and campodea-form. It climbs 
 upon a flower and thence upon the body of a bee (AiifJio- 
 phora), which carries it to the nest, where it eats the egg of 
 the bee. After a moult, the larva though still six-legged, has 
 become cylindrical, fleshy and less active, resembling a lamelli- 
 corn larva; it now appropriates the honey of the bee. With 
 plenty of rich food at hand the larva becomes sluggish, and 
 after another moult appears as a pseudo-pupa, with function- 
 less mouth parts and atrophied legs. From this pseudo-pupa 
 emerges a third larval form, of the pure cruciform type, fat 
 and apodous like the bee-larvre themselves. After these four 
 distinct stages the larva becomes a pupa and then a beetle. 
 
 Epicauta, another meloid, has a similar history. The tri- 
 uiigitlin (Fig. 217, A) of E. z'ittafa burrows into an egg'-pod 
 
DEVELOPMENT 
 
 '75 
 
 of Mclaiu)plus diffcrcutiaUs and eats the eL;i;s of that g'rass- 
 hopper. After a niDult the second larz'd (carabidoid form) 
 appears; this {B) is soft, with re(hice(l lei^'s aii<l niontli parts 
 and less acti\-e than the trinni^nhn. A second monit and the 
 scarabaddiud form of the second h\r\a is assnmed ; the lees 
 
 Fig. 
 
 Stages in the hypermetamorphosis of Epicanta. A, ti-iungulin; B, carabidoid stage 
 of second larva; C, ultimate stage of second larva; D, coarctate larva; E, pupa; F, 
 imago. E is species cinerea; the others are z'itfata. All enlarged except F. — After 
 Riley, from Trans. St. Louis Acad. Science. 
 
 and mouth parts are now rudimentary and the body more 
 compact than before. A third and a fourth moult occur with 
 little change in the form of the second larva, which is now^ in 
 its nltiniatc stage (C). After the fifth moult, however, the 
 coarctate larva, or pseudo-pupa, appears; this (D) hibernates 
 and in spring sheds its skin and becomes the tJiird larva, which 
 soon transforms to a true pupa (£), from which the beetle 
 {F) shortly emerges. Thus the pupal stage is preceded by 
 at least three distinct larval stages. 
 
 In the anomalous l;)eetle Stxlops, the males are winged, but 
 the females are maggot-like and sedentary, living in the bodies 
 of bees and wasps. Packard found as many as three hundred 
 
176 
 
 ENTOMOLOGY 
 
 triimgiilin larva; issuing from a female Sfylops in the body of 
 an Aiidrcua. The further life history of Stylo ps is but im- 
 perfectly known ; probajbly the triungulin climbs upon a bee 
 or a wasp and enters its body, after the manner of the Euro- 
 pean Rliipiphonis paradoxus, whose life-history is much bet- 
 ter understood. 
 
 The most extraordinary metamorphoses have been found 
 among parasitic Hymenoptera. as in Platygastcr, a proctotry- 
 pid which infests the larva of Cccidoiiiyia. The egg of Platy- 
 pasfcr, according to Ganin, hatches into a larva of bizarre 
 
 Fig. 2 1 8. 
 
 Stages in the hypermetamorphosis of Platygastcr. A, first larva; B, second larva; 
 C, third larva; a, antenna; b, brain; f, fat-tissue; /;, hind intestine: )n, mandible; mo, 
 mouth; ins, muscle; n, nerve cord; r, reproductive organ of one side; s, salivary 
 gland; t, trachea. — After Ganin. 
 
 form (Fig. 218, A), suggesting the crustacean Cyclops, rather 
 than an insect. This first larva has a blind food canal and no 
 nervous, circulatory or respiratory systems. After a moult 
 the outline is oval [B), and there are no appendages as yet, 
 though the nervous system is partially developed. Another 
 moult, and the third larva appears (C), elliptical in contour, 
 ■externally segmented, with trachea^ and a pair of mandibles. 
 
DEVELOPMENT 1/7 
 
 From now on, the development is essentially like that of other 
 parasitic Hymenoptera. 
 
 E(|nally anomalous are the changes undergone by ^0/3-- 
 iiciiui. a proctotrypid parasite in the eggs of dragon flies, and 
 by the proctotrypid Tclcas, which affects the eggs of the tree 
 cricket (Qicanfhiis). In all these cases the larvae go through 
 changes which in most other insects are confined to the egg 
 stage. In other words, the lar\a hatches before its embryonic 
 development is completed, so to speak. 
 
 Significance of Metamorphosis, — " The essential features 
 of metamorphosis," says Sharp, " appear to be the separation 
 in time of growth and development, and the limitation of the 
 reproductive processes to a short period at the end of the indi- 
 vidual life." 
 
 The simplest insects, Thysanura, have no metamorphosis, 
 and show no traces of ever having had one. Hence it is in- 
 ferred that the first insects had none ; in other words, the phe- 
 nomenon of metamorphosis originated later than insects them- 
 selves. Successive stages in the evolution of metamorphosis 
 are illustrated in the various orders of insects. 
 
 The distinctive mark of the simplest metamorphosis, as in 
 Orthoptera and Hemiptera, is the acquisition of w'ings ; growth 
 and sexual development proceeding essentially as in the non- 
 metamorphic insects (Thysanura and Collembola). Here the 
 development of wnngs does not interfere wnth the activity of 
 the insect; its food habits remain unaltered; throughout life 
 the environment of the individual is practically the same. 
 Even when considerable difference exists between the nym- 
 phal and imaginal euA'ironments, as in Ephemerida and 
 Odonata, the activity of the individual may still be continu- 
 ous, even if somewdiat lessened as the period of transforma- 
 tion approaches. 
 
 With Neuroptera, the pupal stage appears. In these and 
 all other holometabolous insects the larva accumulates a sur- 
 plus of nutriment sufficient for the further development, which 
 becomes condensed into a single pupal stage, during wdiich 
 external activity ceases temporarily. 
 13 
 
178 ENTOMOLOGY 
 
 With the increasing contrast between the organization of 
 the larva and that of the imago, the pupal stage gradually 
 becomes a necessity. Metamorphosis now means more than 
 the mere acquisition of wings, for the larva and the imago 
 have become adapted to widely different environments, chiefly 
 as regards food. The caterpillar has biting mouth parts for 
 eating leaves, while the adult has sucking organs for obtaining 
 liquid nourishment : the maggot, surrounded by food that may 
 be obtained almost without exertion, has but minimum sensory 
 and locomotor powers and for mouth parts only a pair of 
 simple jaws ; as contrasted with the fly, which has wings, 
 highly developed mouth parts and sense organs, and many 
 other adaptations for an environment which is strikingly un- 
 like that of the larva ; so also in the case of the higher Hymen- 
 optera, where maternal or family care is responsible for the 
 helpless condition of the larva. 
 
 Thus it is evident that the change from larval to imaginal 
 adaptations is no longer congruous with continuous external 
 activity; a quiescent period of reconstruction becomes in- 
 evitable. 
 
 As was said, the cruciform type of larva has been derived 
 from the thysanuriform type, the strongest evidence of this 
 being the fact that among hypermetamorphic insects, the 
 change from the one to the other takes place during the life- 
 time of the individual. Furthermore, the cruciform condi- 
 tion is plainly an adaptive one, brought about by an abundant 
 and easily obtainable supply of food. The lack of a thysa- 
 nuriform stage in the development of the most specialized 
 cruciform larvse, as those of flies and bees, is regarded by 
 Hyatt and Arms as an illustration of the general principle 
 known as " acceleration of development," according to which 
 newer and useful adaptive characters tend to appear earlier 
 and earlier in the development, gradually crowding- upon and 
 forcing out older and useless characters. In connection with 
 this subject, the appearance of temporary abdominal legs in 
 embryo bees is significant, as indicating an ancestral active 
 
DEVELOPMENT 
 
 179 
 
 Fig. 
 
 condition. In accounting- for the evolution of metamorpho- 
 sis, the theory of natural selection 
 finds one of its most important appli- 
 cations. 
 
 3. Internal METAMORrnosEs 
 
 In Heterometahola. the internal 
 post-embryonic changes are as di- 
 rect as the external changes of 
 form; in Holometahola, on the con- 
 trar)-. not all the larval organs 
 pass directly into imaginal organs, 
 for certain larval tissues are de- 
 molished and their sul)stance recon- 
 structed into imaginal tissues. Wdien 
 
 Diagrammatic transverse 
 
 section of Corethra larva, to 
 show imaginal buds of wings 
 iw) and legs (/) ; h, hypoder- 
 mis; i, integument. — Modified 
 from Lang's Lehrbttch. 
 
 ¥k 
 
 Diagrammatic transverse sections of muscid larvre, to show imaginal buds, h, lar- 
 val hypodermis; /, larval integument; ih. imaginal hypodermis; /, imaginal bud of 
 leg; w, imaginal bud of wing.— Modified from Lang's Lchrbuch. 
 
:8o 
 
 ENTOMOLOGY 
 
 indirect, however, the internal metamorphosis is nevertheless 
 continuous and gradual, without the abruptness that charac- 
 terizes the external transformation. In the lan'al stage ima- 
 ginal organs arise and grow ; in the pupal stage the purely 
 larval organs gradually disappear ^^•hile the imaginal organs 
 are continuing their development. 
 
 Phagocytes. — The destruc- 
 
 FlG. 221. . f •' 
 
 tion of larval tissues, or his- 
 tolysis, is due often to the 
 amoeboid blood corpuscles, 
 known as leucocytes or phago- 
 cytes, which attack some tis- 
 sues and absorb their mate- 
 rial, but later are themselves 
 food for the developing imagi- 
 nal tissues. The construction 
 of tissues is termed histo- 
 genesis. 
 
 In Coleoptera. however, the 
 degeneration of the larval mus- 
 cles is entirely chemical, there 
 being no evidence of phago- 
 cytosis, according to Dr. R. S. 
 Breed. Berlese, indeed, goes 
 so far as to deny in general 
 the destructive action of leuco- 
 cytes on larval tissues. 
 
 Imaginal Buds. — The wings 
 and legs of a fly originate in 
 the larva in the form of cellu- 
 lar masses, or iiiiagiiial buds, 
 as \\"eismann discovered. Thus 
 in the larva of Corethra, there 
 are in each thoracic segment a pair of dorsal buds and a pair 
 of ventral buds (Fig. 219), each bud being clearly an evagi- 
 nation of the hypodermis at the bottom of a previous invagi- 
 
 Imaginal buds of full grown larva 
 of Pieris, dorsal aspect, b, brain ; 
 m, mid intestine; s^, prothoracic 
 spiracle; s*, first abdominal spiracle; 
 sg, silk gland; I, prothoracic bud; 
 //, bud of fore wing; ///, bud of 
 hind wing. — After Gonin. 
 
DEVELOPMENT 
 
 I8l 
 
 nation. Tlie six ventral Inuls form the legs eventually; of 
 the dorsal l)U(ls. the middle and posterior pairs form, resi)cc- 
 tively, the wings and the halteres, and the anterior pair form 
 the pupal respiratory processes. Each imaginal hud is situ- 
 ated in a pcripodal arrily. the wall of which { pcripodal mem- 
 brane) is continuous with the general hypoderniis; as the legs 
 and wings develop, they emerge from their pcripodal sacs and 
 hecome free. 
 
 In Corcthra hut little histolysis occurs, most of the larval 
 structures passing' directly into the corresponding structures 
 of the adult. Corcthra, indeed, is in many respects interme- 
 diate between heterometabolous and holometabolous insects as 
 regards its internal changes. 
 
 Fig. 222. 
 
 Section through left hind wing in larva of Picris rapff, the section being a frontal 
 one of the caterpillar; tlie base of the wing is anterior in position, and the apex 
 posterior, c, cuticula; /;, hypodermis; t, trachea; w, developing wing. — After M.wer. 
 
 Muscidae. — In ]\Iuscid?e, as compared with Corcthra, the 
 imaginal buds are more deeply situated, the peripodal mem- 
 brane forming a stalk (Fig. 220), and the processes of his- 
 tolysis and histogenesis become extremely complicated. The 
 hypodermis, muscles, alimentary canal and fat-body are grad- 
 ually broken down and remodeled, and part of the respiratory 
 system is reorganized, thougii the dorsal vessel and the central 
 nervous system, uninterrupted in their functions, undergo 
 comparatively little alteration. 
 
 The imaginal hypodermis of the thorax arises from thick- 
 
l82 
 
 ENTOMOLOGY 
 
 enings of the peripodal membrane which spread over the lar- 
 val hypodermis, while the 
 "^' latter is gradually being 
 
 broken down by the leuco- 
 cytes ; in the head and abdo- 
 men the process is essen- 
 tially the same as in the 
 thorax, the new hypodermis 
 arising from imaginal buds. 
 Most of the larval mus- 
 cles, excepting" the three 
 pairs of respiratory muscles, 
 undergo dissolution. The 
 imaginal muscles have been 
 traced back to mesodermal 
 cells such as are always as- 
 sociated with imaginal buds. 
 Hymenoptera and Lepi- 
 doptera. — The internal 
 transformation in Hymen- 
 optera, according to Bugn- 
 ion, is less profound than 
 in MuscidcT and more ex- 
 tensive than in Coleoptera 
 and Lepidoptera. The in- 
 ternal metamorphosis in 
 Lepidoptera resembles in 
 many respects that of Corc- 
 tlira. In both these orders 
 the dorsal pair of protho- 
 racic buds is absent. In a 
 full-grown caterpillar the 
 fundaments of the imaginal 
 legs and wings (Fig. 221) 
 may be seen, the wings in a 
 
 frontal section of the larva appearing as in Fig. 222. Many 
 
 Internal transformations of Sphinx ligus- 
 tri. A, larva; B, pupa; C, moth; a, aorta; 
 an, antenna; b, brain; f, fore intestine; 
 fr, food reservoir; h, hind intestine; ht, 
 heart; m, mid intestine; mt, Malpighian 
 tubes; p, proboscis; s, suboesophageal gang- 
 lion; t, testis; tg, thoracic ganglia; v, ven- 
 tral nerve cord. — After Newport. 
 
DEVELOPMENT 1 83 
 
 of the details of the internal metamorphosis in Lepidoptera 
 ha\e heen described by Ne\vi)ort and Gonin. Figaire 223, 
 after Xewport, shows some of the more evident internal dif- 
 ferences in the larva, ])npa and imago of a lepidopterous insect. 
 Significance of Pupal Stage. — To repeat — among- holo- 
 metabolons insects the function of nutrition becomes relegated 
 to the larval stage and that of reproduction to the imaginal 
 stage. Larva and imago become adapted to widely different 
 environments. So dissimilar are the two environments that 
 a gradual change from the one to the other is no longer pos- 
 si])le; the revolutionary changes in structure necessitate a tem- 
 porary cessation of external activity. 
 
CHAPTER IV 
 
 ADAPTATIONS OF AQUATIC INSECTS 
 
 Ease, versatility and perfection of adaptation are beauti- 
 fully exemplified in aquatic insects. 
 
 Systematic Position. — Aquatic insects do not form a sepa- 
 rate group in the system of classification, but are distributed 
 among many orders, of which Plecoptera, Ephemerida, Odo- 
 nata and Trichoptera are pre-eminently aquatic. One third of 
 the families of Heteroptera and less than one fourth those of 
 Diptera are more or less acjuatic. One tenth of the families 
 of Coleoptera frequent the^water at one stage or another, but 
 only half a dozen genera of Lepidoptera. A few Collembola 
 live upon the surface of water, and several Hymenoptera, 
 though not strictly aquatic, are known to parasitize the eggs 
 and larvcT of aquatic insects. 
 
 The change from the terrestrial to the aquatic habit has been 
 a gradual change of adaptation, not an abrupt one. Thus at 
 present there are some tipulid larvse that inhabit comparatively 
 dry soil ; others live in earth that is moist ; many require a 
 saturated soil near a body of water and many, at length, are 
 strictly aquatic. Among beetles, also, similar transitional 
 stages are to be found. 
 
 Food. — Insects have become adapted to utilize with re- 
 markable success the immense and varied supply of food that 
 the water afifords. Hosts of them attack such parts of plants 
 as project above the surface of the water, and the caterpillar 
 of Paraponyx (Fig. 171) feeds on submerged leaves, espe- 
 cially of Vallisncria, being in this respect unique among Lepi- 
 doptera. Hydrophilid beetles and many other aquatic insects 
 devour submerged vegetation. The larvae of the chrysomelid 
 genus Donacia find both nourishment and air in the roots of 
 aquatic plants. Various Collembola subsist on floating algae, 
 
 184 
 
ADAPTATIONS OF AQUATIC INSECTS 
 
 185 
 
 and Iarv;e of mosquitoes and l)lack-flies on microscopic org-an- 
 isms near the surface, while larvae of CJiironoinus find food in 
 the sediment that accumulates at the bottom of a body of 
 water. 
 
 Predaceous species abound in the water. Nofoiiccta (Fig. 
 224) approaches its i)rey from beneath, clasps it with the front 
 
 Fig. 224. 
 
 Fig. 225. 
 
 Backsvvimmer, Notonccta insulata, 
 natural size. 
 
 Water-skater, Ccrris re, 
 
 natural size. 
 
 pair of legs and pierces it. Ncpa and Ranatva likewise have 
 prehensile front legs along with powerful piercing organs. 
 Bclostoina and Bcnacus (Fig. 22) even 
 kill small fishes by their poisonous punc- 
 tures. Some other kinds, as the water- 
 skaters (GerridcC, Fig. 225), depend on 
 dead or disabled insects. The species of 
 Hydrophihis (Fig. 226) are to some ex- 
 tent carnivorous as larvae but phytopha- 
 gous as imagines-, while Dytiscidse are car- 
 nivorous throughout life. Aquatic insects 
 eat not only other insects, but also worms, 
 crustaceans, mollusks or any other avail- 
 able animal matter. 
 
 Even aquatic insects are not exempt 
 from the attacks of parasitic species. A 
 few Hymenoptera actually enter the 
 
 water to find their victims, for example, the ichneumon Agrio- 
 typiis, which lays its eggs on the larvae of caddis flies. 
 
 Hydro[>hilus triangularis, 
 natural size. 
 
i86 
 
 ENTOMOLOGY 
 
 Locomotion. — Excellent adaptations for aquatic locomo- 
 tion are found in the common Hydro pJiihis triangularis (Fig. 
 226). Its general form reminds one of a boat, and its long 
 legs resemble oars. The smoothly elliptical contour and the 
 polished surface serve to lessen friction. Owing to the form 
 of the body (Fig. 22"/, A) and the presence of a dorsal air- 
 
 FlG 
 
 Transverse sections of {A) 
 
 A B 
 
 Hydropliilus and (S) Notonccta. 
 tron; /. metathoracic leg. 
 
 elytron; h, hemely- 
 
 chamber under the elytra, the back of the insect tends to re- 
 main uppermost, while in Notonccta (Fig. 227, B) ,on the other 
 hand, the conditions are reversed, and the insect swims with 
 its back downward. The legs of HydropJiilns, excepting the 
 first pair, are broad and thin (Fig. 228, A) and the tarsi are 
 fringed with long hairs. When swimming, the " stroke " is 
 made by the flat surface, aided by the spreading hairs ; but on 
 the " recover," the leg is turned so as to cut the water, while 
 the hairs fall back against the tarsus from the resistance of the 
 water, as the leg is being drawn forward. The hind legs, 
 being nearest the center of gravity, are of most use in swim- 
 ming, though the second pair also are used for this purpose ; 
 indeed, a terrestrial insect, finding itself in the water, instinc- 
 tively relies upon the third pair of legs for locomotion. Hy- 
 drophilus uses its oar-like legs alternately, in much the same 
 sequence as land insects, but Cybistcr and other Dytiscidae, 
 which are even better adapted than Hydro philus for acjuatic 
 locomotion, move the hind legs simultaneously, and therefore 
 can swim in a straight line, without the wobbling and less 
 economical movements that characterize HydropJiilns. 
 
ADAPTATIONS OF AQUATIC INSECTS 
 
 187 
 
 Larvne of niosciniloes pr()[)el themseh-es by means of lash- 
 ing, or undulatory, movements of the abdomen. A peculiar 
 mode of locomotion is found in dragon lly nymphs, which 
 project themselves by forcibly ejecting a stream of water from 
 the anus. 
 
 On account of the large amount of air that they carry about, 
 most aquatic imagines are lighter than the water in which they 
 
 Fk;. 228. 
 
 Left hind legs of aquatic beetles. A, hh 
 hit us; c, coxa; /, femur; s, spur; 
 
 droplnlus 
 t, tarsus 
 
 Mignlar 
 . tibia: 
 
 B, Cybisfci 
 trochanter 
 
 live, and therefore can rise without effort, but can descend only 
 by exertion, and can remain below only by clinging to chance 
 stationary objects. The mosquito larva (Fig. 229, ^) is often 
 heavier than water, but the pupa (Fig. 229, B) is lighter, and 
 remains clinging to the surface film. 
 
 The tension of this surface film is sufticient to support the 
 weight of an insect up to a certain limit, provided the insect 
 
i88 
 
 ENTOMOLOGY 
 
 Fig. 229. 
 
 has some means of keeping its body dry. This is accom- 
 phshed usually by hairs, set together so thickly that water 
 cannot penetrate between them. 
 As the legs and body of Gcrris 
 are rendered water-proof by a vel- 
 vety clothing of hairs, the insect, 
 though heavier than water, is able 
 to skate about on the surface. 
 Gyrimis, by means of a similar 
 adaptation, can circle about on the 
 surface film, and minute collem- 
 bolans leap aljout on the surface as 
 readily as on land. 
 
 The modifications of the legs 
 for swimming have often impaired 
 their usefulness for walking, so 
 that many aquatic Coleoptera and 
 Hemiptera can move but awk- 
 wardly on land, \\dien walking, 
 it is interesting to note, Cybisfcr 
 and some other aquatic forms no 
 longer move their hind legs simul- 
 taneously as they do in swimming, 
 but use them alternately, like ter- 
 restrial species. 
 
 The adaptations for swimming 
 do not necessarily affect the power 
 of flight. Dytiscus, Hydrophilus, 
 Gyriuiis, Notonccta, Bcnaciis and 
 many other Coleoptera and Hemip- 
 Larva ^A) and pupa (B) of ^cra Icavc the water at night and 
 
 mosquito, Culex pipicns. r, respi- fly arOUUd, oftCU bciug fouud about 
 ratory tube; t, tracheal gills. 
 
 Respiration. — Aquatic insects have not only retained the 
 primitive, or open (Jwlopiicitsfic) , type of respiration, charac- 
 
ADAPTATIONS OF AQUATIC INSECTS 1 89 
 
 terized by the presence of spiracles, but have also developed 
 an adaptive, or closed {apiicustic) , type, for ntilizini;- air that 
 is mixed with water. 
 
 Through minor modifications of structure and habit, many 
 holopneustic insects have become fitted for an aquatic life. In 
 these instances the insects have some means of carrying down 
 a supply of air fn^n the surface of the water. Thus Noto- 
 nccta bears on its bcxly a silvery film of air entangled in closely 
 set hairs, which exclude the water. Gyriiius descends with a 
 bublile of air at the end of the abdomen. Dyfiscus and Hy- 
 drophUiis have each a capacious air-space between the elytra and 
 the abdomen, into which space the spiracles open. Ncpa and 
 Ranatra have each a long respiratory organ composed of two 
 vah-es. which lock together to form a tube that communicates 
 with the single pair of spiracles situated near the end of the 
 abdomen. The mosquito larva, hanging from the surface 
 film, breathes through a cylindrical tube (Fig. 229, A, r) pro- 
 jecting from the penultimate abdominal segment ; the pupa, 
 however, bears a pair of respiratory tubes on the back of the 
 thorax (Fig. 229, 5. r, r), which is now^ upward, probably in 
 order to facilitate the escape of the fly. The rat-tailed maggot 
 (Eristalis) , three quarters of an inch long, has an extensile 
 caudal tube seven times that length, containing two tracheae 
 terminating in spiracles, through which air is brought down 
 from above the mud in wdiich the larva lives. Similarly, in 
 the dipterous larva, Bitiacomorpha clavipcs (Fig. 172), the 
 posterior segments of the abdomen are attenuated to form a 
 long respiratory tube. The larva of Donacia appears to have 
 no special adaptations for aquatic respiration except a pair of 
 spines near the end of the body, for piercing air chambers in 
 the roots of the acjuatic plants in which it dwells. 
 
 The simplest kind of apneustic respiration occurs in aquatic 
 nymphs such as those of Ephemerida and Agrionidce, whose 
 skin at first is thin enough to allow a difect aeration of the 
 blood. This cutaneous respiration is possible during the early 
 life of many aquatic species. 
 
190 
 
 ENTOMOLOGY 
 
 Bronchial respiration, however, is the prevalent type amon^ 
 aquatic nymphs and is perhaps the most important of their 
 adaptive characteristics. Thin-walled and extensive out- 
 growths of the integument, containing tracheal branches or, 
 rarely, only blood, enable these forms to oljtahi air from the 
 water. May fly nymphs (Figs. 19, A ; 169), with their ample 
 waving gills, offer familiar examples of branchial respiration. 
 Tracheal gills are \ery diverse in form and situation, occurring 
 in a few species of May fly nymphs on the 
 thorax or head, though commonly re- 
 stricted to the sides of the abdomen, 
 where they occur in pairs or in paired 
 clusters (Fig. 19, A). Caudal gills are 
 found in agrionid nymphs (Fig. 170). 
 The aquatic caterpillars of Paraponyx 
 (Fig. 171) are unique among Lepidop- 
 tera in having gills, which are filamentous 
 in this instance. 
 
 Caddis worms, enclosed in their cases, 
 maintain a current of water by means 
 of undulatory movements of the body, 
 and the larvse and pupse of most black flies 
 (Simuliid?e, Fig. 230) secure a continuous 
 supply of fresh air simply by fastening 
 themselves to rocks in swiftly flowing streams. 
 
 Rectal respiration is highly developed in odonate and ephe- 
 merid nymphs. In these, the rectum is lined with thousands 
 of tracheal branches, which are bathed by water drawn in from 
 behind, and then expelled. 
 
 All these kinds of respiration — cutaneous, branchial and 
 rectal — occur in young ephemerid nymphs ; while mosquito 
 larvcC have in addition spiracular respiration. 
 
 With the arrival of imaginal life, tracheal gills disappear, 
 except in Perlidse, and even in these insects the gills are of 
 little if any use. 
 
 Marine Insects. — Except along the shore, the sea is almost 
 
 Simulium; A, larva; B, 
 pupa, showing respira- 
 tory filaments. 
 
ADAPTATIONS OF AQUATIC INSECTS IQI 
 
 devoid of insect life, the exceptions being- a few cliirononiid 
 larvcC which lia\e liecn (h'edt^ed in deep water, and fifteen 
 species of }{alobafcs (belong-inj^- to tlie same family as onr 
 familiar pond-skaters), which are fonnd en warm smooth seas, 
 where they snbsist on floating animal remains. 
 
 Between tide-marks may be fonnd varions beetles and col- 
 lemb(tlans, which feed upon organic del)ris; as the tide rises, 
 the former retreat, but the latter commonly burrow in the sand 
 or under stones and become submerged, for example the com- 
 mon Auurida inaritiiiia. 
 
 Insect Drift. — Seaweed or other refuse cast upon the shore 
 harbors a great variety of insects, especially dipterous larvae, 
 staphylinid scavengers and predaceous Carabidre. On the 
 shores of inland ponds and lakes a similar assemblage of in- 
 sects may be found feeding for the most part on the remains 
 of plants or animals, or else on one another. During a strong 
 wind, the leeward shore of a lake is an excellent collecting 
 ground, as many insects are driven against it. On the shores 
 of the Great Lakes insects are occasionally cast up in immense 
 numbers, forming a broad windrow, fifty or perhaps a hundred 
 miles long. Needham has described such an occurrence on 
 the west shore of Lake ^Michigan, following a gale from the 
 northeast. In this instance, a liter of the drift contained 
 nearly four thousand insects, of which 66 per cent, were crick- 
 ets {Nemobius), 20 per cent. Acridiidae, and the remainder 
 mostly beetles (CarabidcT, Scarab?eidas. Chrysomelidre, Coc- 
 cinellidae, etc.). dragon flies, moths, butterflies (Auosia, 
 Picris, etc.) and various Hemiptera, Hymenoptera and Dip- 
 tera. A large proportion of the insects were acjuatic forms, 
 such as Hydrophilus, Cyhistcr, ZaitJia, and a species of caddis 
 fly ; these had doubtless been carried out by freshets, while the 
 butterflies and dragon flies had been borne out by a strong 
 wind from the northwest, after which all were driven back to 
 the coast by a northeast wind. While some of these insects 
 survived, notably CoccinellidcC, Trichoptera. Asilidie, Acridi- 
 idas and Gryllidc'e, nearly all the rest were dead or dying, in- 
 
192 ENTOMOLOGY 
 
 eluding the dragon flies, flies, bumble bees and waspsl Fora- 
 ging Carabidse were observed in large numbers, also scaven- 
 gers of the families Staphylinidje, Silphidse and Dermestidse. 
 
 On the seashore and on the shores of the Great Lakes, the 
 salient features of insect life are essentially the same. Sim- 
 ilar species occur in the two places with similar biological 
 relations, on account of the general similarity of environment. 
 
 Origin of the Aquatic Habit. — The theory that terrestrial 
 insects have arisen from aquatic species is no longer tenable, 
 for the evidence shows that the terrestrial type is the more 
 primitive. Aquatic insects still retain the terrestrial type of 
 organization, which remains unobscured by the temporary and 
 comparatively slight adaptations for 'an aquatic life. Thus, 
 the development of tracheal gills has involved no important 
 modification of the fundamental plan of tracheal respiration. 
 It is significant, moreover, that the most generalized, or most 
 primiti\-e, insects — Thysanura — are without exception terres- 
 trial. Acjuatic insects do not constitute a phylogenetJc unit, 
 but represent various orders, which are for the most part un- 
 doubtedly terrestrial, notwithstanding the fact that a few of 
 these orders (Plecoptera, Ephemerida, Odonata, Trichoptera) 
 are now wholly aquatic in habit. Adaptations for an aquatic 
 existence have arisen independently and often, in the most 
 diverse orders of insects. 
 
CHAPTER V 
 
 COLOR AND COLORATION 
 
 The naturalist distinguishes between the terms color and 
 coloration. A color is a single hue, while coloration refers 
 to the arrangement of colors. 
 
 Sources of Color. — The colors of insects are classed as 
 (i) pigmental {cliciiiical) , those due to internal pigments; 
 (2) structural {physical), those due to structures that cause 
 interference or reflection of light; and (3) coiiibiiiation colors 
 (chciiiico-pliysical) , which are produced in both ways at once. 
 
 Structural Colors. — The iridescence of a fly's wing and 
 that of a soap bul)l)le are produced in essentially the same way. 
 The wing, however, consists of two thin, transparent, slightly 
 separated lamelhe. which diffract white light into prismatic 
 rays, the color differences depending upon differences in the 
 distance between the two membranes. 
 
 The brilliant iridescent hues of many butterfly scales are due 
 to the diffraction of light by fine, closely parallel strije (Fig. 
 92) just as in the case of the " diffraction gratings " used by 
 the physicist, which consist of a glass or metallic plate wath 
 parallel diamond rulings of microscopic fineness. The par- 
 ticular color produced depends in both cases upon the distance 
 between the striae. Though almost all lepidopterous scales are 
 striated, it is only now and then that the striae are sufficiently 
 close together to give diffraction colors. In a Brazilian species 
 of A pat lira the iridescent scales have 1050 strire to the milli- 
 meter, and in a species of Morplw, according to Kellogg, the 
 iridescent pigmented scales have 1,400 striae per millimeter, the 
 striae being only .0007 mm. apart; wdiile in some of the finest 
 Rowland gratings they are as far apart as .0015 mm., though 
 numbering 1,700 per millimeter. 
 
 These interference colors of butterfly scales may be due. not 
 u 193 
 
194 ENTOMOLOGY 
 
 only to surface markings, but also to the lamination of the 
 scale and to the overlapping- of two or more scales. In beetles 
 the metallic blues and greens, and iridescence in general, are 
 often produced by minute lines or pits that diffract the light. 
 Purely structural colors, however, are not so common as might 
 be supposed, according to Tower, who says, " The pits alone, 
 however, are powerless to produce any color; it is only when 
 they are combined with a highly reflecting and refractive sur- 
 face lamella and a pigmented layer below that the iridescent 
 color appears. The action of light is in this case the same as 
 in the plain metallic coloring, excepting that each pit acts as 
 a revolving prism to disperse different wave-lengths of light 
 in different directions, and the combined result is iridescence. 
 The existence of minute pits over the body surface is of com- 
 mon occurrence, but it is only wdien they are combined as 
 above that iridescent colors occur." 
 
 Silvery white effects are usually caused by the total reflec- 
 tion of light from scales or other sacs that are filled with air ; 
 the same silvery appearance is given also by air-filled trachese 
 and by the air bubbles that many aquatic insects carry about 
 under water. 
 
 Violet, blue-green, coppery, silver and gold colors are, with 
 few exceptions, structural colors. (Mayer.) 
 
 Pigmental Colors. — These are either cuticular or hypo- 
 dcnnal. The predominant brown and black colors of insects 
 are made by pigment diffused in the outer layer of the cuticula 
 (Fig. 88). Cockroaches are almost white just after a moult, 
 but soon become brown, and many beetles change gradually 
 from brown to black. In these cases it is apparently signifi- 
 cant that the cuticular pigments lie close to the surface of the 
 skin, i. e., where they are most exposed to atmospheric 
 influences. Tower finds, however, that cuticular colors " are 
 not clue to drying, oxidation, secretion, or like processes," but 
 are due to " some katalytic agent or enzyme [formed by the 
 hypodermis] which, passing out through the pore canals, 
 comes in contact with the primary cuticula and there becomes 
 the active factor in the production of cuticula colors." 
 
COLOR AND COLORATION 195 
 
 Tlie cuticular pigments are derived, of course, from the 
 underlying hypodermis cells, and these cells themselves, more- 
 over, usually contain ( i ) colored granules or fatty drops 
 which give red, yellow, orange and sometimes white or gold 
 colors as seen through the skin; (2) diffused chlorophyll 
 (green) or xanthophyll (yellow), taken from the food plant. 
 Unlike the structural colors, which are persistent, these hypo- 
 dermal colors often change after death, though less rapidly 
 when the pigments are tightly enclosed, as in scales or hairs. 
 Though white and green are structural colors as a rule, 
 they are due to pigments in Pieridce, Lyc3enid?e and some 
 Geometridcie. 
 
 Frequently a color pattern consists partly of cuticular and 
 partly of hypodermal colors, the hypodermal or sub-hypoder- 
 mal color forming " a groundwork upon which the pattern is 
 cut out by the cuticular color." (Tower.) Thus in Lcptino- 
 tai'sa dcccmlineata the pattern " is composed of a dark cutic- 
 ular pigment upon a yellow hypodermal background." 
 
 Combination Colors. — The splendid changeable hues of 
 Apotnra, Eiiphva and other tropical butterflies depend upon 
 the fact that their scales are both pigmented and striated. 
 Under the microscope, certain Apatiira scales are brown by 
 transmitted light and violet by reflected light, and to the un- 
 aided eye the color of the wing is either brown or violet, ac- 
 cording as the light is received respectively from the pigment 
 or from the striated surfaces of the scales. According to 
 Tower, chemico-physical colors " which are of exceedingly 
 wide occurrence, are also the most brilliant and varied of all 
 those found in insects. To this class belong all metallic, iri- 
 descent, pearly, and translucent colors, as well as blue, green, 
 and violet in almost every case." 
 
 Nature of Pigments. — Some pigments are taken bodily 
 from the food ; others are manufactured indirectly from the 
 food, and some of these are excretory products. 
 
 The green color of many caterpillars and grasshoppers is 
 due to chlorophyll, which tinges the blood and shows through 
 
196 ENTOMOLOGY 
 
 the transparent integument. ]\Iayer has found that scales of 
 Lepidoptera contain only blood while the pigment is forming; 
 that the first color to appear upon the pupal wings is a dull 
 ochre or drab — the same color that the blood assumes when 
 it is removed from the pupa and exposed to the air; also that 
 pigments like those of the wings may be manufactured artifi- 
 cially from pupal blood. Pierid?e are peculiar in the nature 
 of their pigments, as Hopkins has shown. The white pigment 
 of this family is uric acid and the reds and yellows of Pieris. 
 Colias and Papilio are due to derivatives of uric acid ; the 
 yellow pigment, termed lepidotic acid, precedes the red in time 
 of appearance, the latter being probably a derivative of the 
 former. The green pigments of some Papilionidse, Noctu- 
 idse, Geometridc-e and Sphingidje are also said by some inves- 
 tigators to be products of uric acid, which in insects as in other 
 animals is primarily an excretory, or waste, product. 
 
 Effects of Food on Color. — Besides chlorophyll, to which 
 various caterpillars, aphids and other forms owe their green 
 color, the yellow constituent of chlorophyll, namely xantho- 
 phyll, frequently imparts its color to plant-eating insects, while 
 some phytophagous species are dull yellow or brown from the 
 presence of tannin, taken from the food plant. Most pig- 
 ments, however, are elaborated from the food by chemical 
 processes that are not well understood. 
 
 Many who have reared Lepidoptera extensively know that 
 the color of the imago is influenced by the character of the 
 larval food, other conditions being equal, and are able at will 
 to effect certain color changes simply by feeding the larvse 
 from birth upon particular kinds of plants. In this country 
 we have few observations upon the subject, but in Europe 
 the effects of food upon coloration have been ascertained in 
 the case of many species of Lepidoptera. According to Greg- 
 son, Hybernia defoliaria is richly colored when fed upon 
 birch, but is dull colored and almost unmarked when fed on 
 elm. Pictet, by feeding larvae of J^aucssa urficcc on the flow- 
 ers instead of the leaves of the nettle obtained the variety 
 
COLOR AND COLORATION 1 97 
 
 known as wticoidcs. T^"'ood affects the color of the larva also, 
 as Poulton found in the case of caterpillars of Tryphcuna pro- 
 iiiiba, all from the same batch of eggs. When fed with only 
 the white midribs of cabbage leaves, the larv?c remained almost 
 white for a time, but afterward showed a moderate amount of 
 black pigment ; when fed with the yellow etiolated heart-leaves 
 or the dark green external leaves, however, the larvrc all be- 
 came bright green or brown — the same pigment being derived 
 indifferently from etiolin (probably the same substance as 
 xanthophyll) or chlorophyll. 
 
 Though the pigments may dift'er in color or amount accord- 
 ing to the kind of food, the color patterns vary without regard 
 to food. Thus CaUosamia promctlica, Leptinotarsa decem- 
 Uncata (Colorado potato beetle), Coccinellidae (lady-bird 
 beetles) and a host of other insects exhibit extensive individ- 
 ual variations in coloration under precisely the same food con- 
 ditions. Caterpillars of the same kind and age are often very 
 dift'erently marked when feeding upon the same plant; for 
 example, Hcliothis aniiiger (corn worm) and the sphingid 
 Dcilcphila Uncata. Furthermore, striking changes of colora- 
 tion accompany each moult in most caterpillars, but particu- 
 larly those of butterflies, and these changes may prove to have 
 an important phylogenetic significance. Individual differ- 
 ences of coloration apart from those due to the direct action 
 of food, light, temperature and other environmental condi- 
 tions are to be explained by heredity. 
 
 Effects of Light and Darkness. — Sunlight is an important 
 factor in the development of most animal pigments, as they 
 will not develop in its absence. The collembolan Anurida 
 maritima is white at hatching, but soon becomes indigo blue, 
 unless shielded from sunlight, in which event it remains white 
 until exposed to the sunlight, when it assumes the blue color. 
 Subterranean or wood-boring larvae are commonly white or 
 yellow, but never highly colored. The most notable instances, 
 however, are furnished by cave insects. These, like other 
 cavernicolous animals, are characteristically white or pale 
 
198 ENTOMOLOGY 
 
 from the absence of pigrnent, if they hve in regions of con- 
 tinual darkness, but have more or less pigmentation in propor- 
 tion respectively to the greater or less amount of sunlight to 
 which they have access. 
 
 Curiously enough, light often hastens the destruction of 
 pigment in insects that are no longer alive, for which reason 
 it is necessary to keep cabinet specimens in the dark as much 
 as possible. Life is evidently essential for the sustension or 
 renewal of the pigments. 
 
 A chrysalis not infrequently matches its surroundings in 
 color. This phenomenon has been investigated by Poulton, 
 who has proved that the color of the chrysalis is determined 
 largely by the prevalent color of the surroundings during the 
 last few days of larval life. Larvae of Pieris rapcu, raised 
 upon the same food plant (all other conditions being made as 
 nearly equal as possible) produced dark pupae if kept in dark- 
 ness for a few days just before pupation; yellow light arrested 
 the formation of the dark pigment and gave green pupae ; while 
 light colors in general gave light-colored pupae. This color re- 
 semblance is commonly assumed to be of protective value, and 
 perhaps it is. Nevertheless, it is a direct effect of light, and 
 does not need to be explained by natural selection, even though 
 it cannot be denied that natural selection may have helped in 
 its production. 
 
 Poulton extended his studies to the adaptive coloration of 
 caterpillars and has published the results of an extensive 
 series of experiments which prove that the colors of certain 
 caterpillars also are directly produced by the same colors in 
 the surrounding light. Gastropacha quercifolia, which always 
 rests by day on the older wood of its food plant, was given 
 black twigs, reddish brown sticks, lichens, etc., to rest upon, 
 and though all the larvae were from the same cluster of eggs, 
 and had been fed in the same way, each larva gradually 
 assumed the color or colors of its resting place, resulting in 
 excjuisite examples of protective resemblance, the most re- 
 markable of which were those in which the larvae assumed the 
 
COLOR AND COLORATION 199 
 
 variegated coloration of lichens. Only the yonnger larvae, 
 however, proved to be susceptible to the colors of the environ- 
 ment; unlike those of Aiiiphidasis hetnlaria, in which the older 
 larvae also were- sensitive to the surrounding light. Here 
 again, natural selection is unnecessary, even if not superfluous, 
 as an explanation of this kind of protective coloration. 
 
 Effects of Temperature. — The amount of a pigment in the 
 wing of a butterfly depends in great measure upon the sur- 
 rounding temperature during the pupal stage, when the pig- 
 ments are forming. Black or brown spots have been enlarged 
 artificially by subjecting chrysalides to cold ; hence it is probable 
 that the characteristically large black spots on the under side 
 of the wings of the spring brood of our Cyaniris pseudargiolus 
 are simply a direct effect of cold upon the wintering chrysal- 
 ides. Similarly the spring brood (variety marcia) of Phy- 
 ciodes tharos owes its distinctive coloration to cold, as Ed- 
 wards has proved experimentally. Lepidoptera have been the 
 subject of very many temperature experiments, some of which 
 will be mentioned presently in the consideration of seasonal 
 coloration. 
 
 Speaking generally, warmth (except in melanism) tends to 
 induce a brightening and cold a darkening of coloration, the 
 darkening being due to an increased amount of black or brown 
 pigment. Temperature, whether high or low, seldom if ever 
 produces new pigments, but simply alters the amount and dis- 
 tribution of pigments that are present already. 
 
 Effects of Moisture. — Very little is known as to the effects 
 of moisture upon coloration. The dark colors of insular or 
 coastal insects as contrasted with inland forms, and the pre- 
 dominance of dull or suffused species in mountainous regions 
 of high humidity, have led observers occasionally to ascribe 
 melanism and suffusion to humidity. In these cases, how- 
 ever, the possible influence of low temperature and other fac- 
 tors must be taken into consideration. The experiments of 
 Merrifield and of Standfuss showed no effect of moisture upon 
 lepidopterous pupae. 
 
200 ENTOMOLOGY 
 
 Pictet has recently found, however, that humidity acting 
 on the caterpillars of Vanessa urticcu and V. polychloros has 
 a conspicuous effect on the coloration of the butterflies. Thus 
 when the caterpillars were fed for ten days with moist leaves, 
 the resulting iDutterflies had abnormal black markings on the 
 wings, and the same results followed wdien the larvae were 
 kept in an atmosphere saturated with moisture. 
 
 Climatal Coloration. — The brilliant and varied colors of 
 tropical insects are popularly ascribed to intense heat, light 
 and moisture ; and the dull monotonous colors of arctic insects, 
 similarly, to the surrounding climatal conditions. Climate 
 undoubtedly exerts a strong influence upon coloration, but the 
 precise nature of this influence is obscure and will remain so 
 until more is known about the effects separately produced by 
 each of the several factors that go to make up what is called 
 climate. 
 
 The prevalence of intense and varied colors among tropical 
 insects is doubtless somewhat exaggerated, for the reason that 
 the highly colored species naturally attract the eye to the ex- 
 clusion of the less conspicuous forms. Indeed, Wallace 
 assures us that, although tropical insects present some of the 
 most gorgeous colors in the whole realm of nature, there are 
 thousands of tropical species that are as dull colored as any 
 of the temperate regions. Carabidse, in fact, attain their 
 greatest brilliancy in the temperate zone, according to Wal- 
 lace, though butterflies certainly show a larger proportion of 
 vivid and varied colors in the tropics. Mayer finds, in the 
 widely distributed genus Papilio, that 200 South American 
 species display but 36 colors, while 22 North American species 
 show 17. While the number of species in South America is 
 nine times as great as in North America, the number of colors 
 displayed is only a little more than twice as great ; hence 
 Mayer concludes that the richer display of colors in the tropics 
 may be due to the far greater number of species, which gives 
 a better opportunity for color sports to arise; and not to any 
 direct influence of the climate. Furthermore, the number of 
 
COLOR AND COLORATION 201 
 
 broods wiiicli occur in a year is much o-reater in the tropics 
 than in the temperate zones, so that the tropical species must 
 possess a corresponchnoiy g'reater opportunity to vary. 
 
 Albinism and Melanism, — These interesting- phenomena, 
 widespread among the higher animals, are little understood, 
 but appear to be due chiefly to temperature. 
 
 Albiiiisiit is excepti(^nal whiteness or paleness of coloration, 
 and is due usually to lack or deficiency of pigment, but in 
 some instances (Pieridre) to the presence of a white pigment. 
 
 The common yellow butterfly, C olios philodicc, and its rela- 
 tives, are frequently albinic. Indeed, as Scudder observes, 
 albinism among butterflies in America appears to be confined 
 to a few Pieridc-e, and to be restricted to the female sex ; it is 
 more common in subarctic and subalpine regions than in lower 
 latitudes and altitudes, and only in the former places does it 
 include all the females. At low altitudes, instead of appear- 
 ing early in the year as mig"ht be expected, the albinic forms 
 appear during' the warmer months. 
 
 In Europe there are many albinic species of butterflies, and 
 they are by no means confined to the family Pierid?e. 
 
 Mclaiiisjii is unusual blackness or darkness of coloration. 
 As to how it is produced little is known, though warmth is 
 probably the most potent influence, and some attribute it to 
 moisture, as w^as mentioned. Pictet obtained partial melan- 
 ism in Vanessa tirticce and V. polycJiIoros by subjecting the 
 larvae to moisture. 
 
 In warm latitudes, some females of. our Papilio glaiicus 
 are blackish brown with black markings, instead of being, as 
 usual, yellow with black markings. In the South, some males 
 of the spring brood of Cyaniris pseiidargiolus are partly or 
 wholly brown instead of blue. 
 
 Seasonal Coloration. — When butterflies have more than 
 one brood in a year, the broods usually differ in aspect, some- 
 times so much that their specific identity is revealed only 
 by rearing one brood from another. The same species may 
 exist under two or more distinct forms during- the same sea- 
 
202 ENTOMOLOGY 
 
 son — in other words, may be seasonally diinorphic, trimorphic 
 or polymorphic. 
 
 Thus Polygoiiia interrogationis has two forms, fabricii and 
 umbrosa, which differ not only in coloration, but even in the 
 form of the wings and the genitalia. In New England fabricii 
 hibernates and produces umbrosa, as a rule, while umbrosa 
 usually yields fabricii. 
 
 The little blue butterfly, Cyaiiiris pseudargiolus (Fig. 231), 
 is polymorphic tp a remarkable degree. In the high latitudes 
 of Canada,* a single brood (litcia) occurs. About Boston, the 
 same spring brood appears, but under two forms : an earlier 
 variety (liicia) , which is small, with large black markings 
 
 Fig. 231. 
 
 C 
 
 Cyaniris pseudargiolus; A, form lucia; B, liolacea; C, pseudargiolus proper. 
 Natural size. 
 
 beneath; and a later variety (violacea), which is typically 
 larger, with smaller black spots, though it varies into the form 
 lucia. Finally, in summer, a third form {pseudargiolus 
 proper) appears, as the product of lucia or else the joint prod- 
 uct of lucia and violacea, and this is still larger, but the black 
 spots are now faint. In the warm South, the spring form is 
 violacea, but while some of the males are blue, others are 
 melanic, as just mentioned — a dimorphic condition which does 
 not occur in the North. Jlolacca then produces pseudargi- 
 olus, in which, however, all the males are blue. 
 
 Iphiclidcs ajax (Fig. 232) is another polymorphic butterfly 
 whose life history is complex. The three principal varieties 
 of this species, known respectively as marcellus, telamonides 
 and ajax, differ not only in coloration, but also in size and 
 form; uiarccUus appears first, in spring; tclaiuonidcs appears 
 
COLOR AND COLORATION 
 
 203 
 
 a little later (though heforc niarccllits has disappeared) ; and 
 aja.v is the summer form ; as the season advances the varieties 
 become successively larger, with longer tails to the hind wings. 
 
 Iphiclidcs aja.v. fLirin tclaiiioiiiilcs, on flower of button bush. Reduced. 
 
 Now Edw^ards submitted chrysalides of the summer form 
 ajax to cold and thereby obtained, in the same summer, butter- 
 flies with the form of ajax but the markings of the spring 
 
 Fig. 233. 
 
 Phyciodes fliaros; A, spring form, marcia; B, summer form, morphcus ; under sur- 
 faces. Natural size. 
 
 form telamonidcs. Some of the chrysalides, however, lasted 
 over until the next spring and then gave tdauwnidcs. 
 
204 ENTOMOLOGY 
 
 In PJiyciodcs tharos (Fig. 233) the spring and summer 
 broods, termed respectively marcia and morpheus, were at first 
 regarded as distinct species. In marcia the hind wings are 
 heavily and diffusely marked beneath with strongly contrast- 
 ing colors, while in morpheus they are plain and but faintly 
 marked. Edwards placed upon ice eighteen chrysalides that 
 normally would have produced morpheus; but instead of this, 
 the fifteen imagines that emerged were all of the spring form 
 marcia and were smaller than usual. Pupae derived from 
 eggs of marcia gave, after artificial cooling, not morpheus, 
 but marcia again. The evident conclusion is that the distinc- 
 tive coloration of the spring variety is brought about by low 
 temperature. In Labrador, only one brood occurs — marcia; 
 in New York, the species is digoneutic (two-brooded) and in 
 West Virginia polygoneutic (several-brooded). 
 
 Extensive temperature experiments upon seasonal dimor- 
 phism in Lepidoptera have been conducted in Europe by some 
 of the most competent biologists. Weismann found that pupae 
 of the summer form of Pieris napi, if placed on ice, disclosed 
 the darker winter form, usually in the same season, though 
 sometimes not until the next spring. It was found impossible, 
 however, to change the winter variety into the summer one 
 by the application of heat. Similar results have attended the 
 important and much-discussed experiments of Dorfmeister, 
 Weismann and others upon ]'\messa levana-prorsa and other 
 species, from which it has been inferred by Weismann that 
 the winter form is the primary, older, and more stable of the 
 two forms, and the summer form a secondary, newer, and less 
 stable variety; since the latter form only, as a rule, responds 
 much to thermal influences. A\'eismann argues that, in addition 
 to the direct effect of temperature, alternative inheritance also 
 plays an important part in the production of seasonal varieties. 
 He tries to show, moreover, that each seasonal variety is col- 
 ored in adaptation to its particular environment and that this 
 adaptation may have been brought about by natural selection — 
 though he does not succeed in this respect. 
 
COLOR AND COLORATION 205 
 
 In several instances, local varieties have been artificially pro- 
 duced as results of temperature control. Thus Standfuss 
 produced in Germany, by the application of cold, individuals 
 of J\Tiicssa iirticw Avhich were indistinguishable from the 
 northern variety polaris; and from pupa; of Vanessa cardiii, 
 by warmth, a very pale form like that found in the tropics ; 
 and, by cold, a dark variety similar to one found in Lapland. 
 
 These investigators and others, notably Merrifield and 
 Fischer, have accumulated a considerable mass of experimen- 
 tal evidence, the interpretation of which is in many respects 
 difficult, involving as it does, not merely the direct effect of 
 temperature upon the organism, but also deep questions of 
 heredity, including reversion, individual variation, and the in- 
 heritance of accpired characters. 
 
 The seasonal increase in size that is noticeable, as in C. 
 psciidargiolus and /. ajax, is doubtless an expression of in- 
 creasing metabolism due to increasing temperature. Warmth, 
 as is well known, stimulates growth, and cold has a dwarfing 
 effect. While this is true as a rule, there are some apparent 
 exceptions, however. Thus Standfuss found that some cater- 
 ]5illars were so much stimulated by unusual warmth that they 
 pupated before they were sufficiently fed, and gave, therefore, 
 tmdersized imagines. A moderate degree of w^armth, how- 
 ever, undoubtedly hastens growth. 
 
 Sexual Coloration. — The sexes are often distinguished by 
 colorational as well as structural differences. Colorational 
 antigcny (this word signifying secondary sexual differences 
 of whatever sort) is most prevalent among butterflies, in 
 which it is the extreme phase of that differentiation of orna- 
 mentation for which Lepidoptera are unrivaled. 
 
 The male of Picris protodice (Fig. 234) has a few brown 
 spots on the front wings ; the female is checkered wdth brown 
 on both wings. In Colias philodice (Fig. 235) and C. ciiry- 
 thcinc the marginal black band of the front wings is sharp 
 and uninterrupted in the male, but diffuse and interrupted by 
 3'ellow spots in the female. In the genus Papilio the sexes 
 
2o6 
 
 ENTOMOLOGY 
 
 Fig. 234, 
 
 Picris protodicc; 
 
 le left) and female (on the right). Natural size. 
 
 Fig. 235. 
 
 are often distinguished by colorational differences and in Hes- 
 periidae the males often have an obHque black dash across the 
 middle of each front wing. Callosainia promethea (Fig. 
 236), the gypsy moth and many other Lepidoptera exhibit 
 colorational antigeny. In not a few Sesiidse the sexes differ 
 greatly in coloration. Thns in the 
 male of the peach tree borer {San- 
 ninoidca exitiosa) all the wings are 
 colorless and transparent; while in 
 the female the front wings are vio- 
 let and opaque and the fourth ab- 
 dominal segment is orange above. 
 The same sex may present two 
 types of coloration, as do males of 
 Cyan iris pseudargiohis and females 
 of Papilio glauciis, already men- 
 tioned. Papilio nicrope, of South 
 Africa, is remarkable in having three 
 females (Frontispiece, Figs. 5, 7, 9, 
 11) which are entirely different in 
 coloration from one another and 
 from the male. There is no longer any doubt, it may be 
 added, as to the specific identity of these forms. 
 
 Next to Lepidoptera, Odonata most frequently show col- 
 orational antigeny. The male of Calopteryx macitlata is vel- 
 
 Colias philodice; right fore 
 wing of male (above) and of 
 female (below). Natural size. 
 
COLOR AND COLORATION 
 
 207 
 
 vetv black ; the female smoky, with a white ptcrostigmatal 
 spot. Among- Coleoptera, the male of Hoplia trifasciata is 
 grayish and the female reddish brown ; a few more examples 
 might be given, though sexual differences in coloration are 
 
 Fig. 236. 
 
 Callosamia promethca; A, male, clinging to cocoon; B, female. Reduced. 
 
 comparatively rare among beetles. Of Hymenoptera, some 
 of the Tenthredinidae exhibit colorational antigeny. 
 
 Among tropical butterflies there are not a few instances in 
 which the special coloration of the female is adaptive — har- 
 monizing with the surroundings or else imitating with remark- 
 able precision the coloration of another species which is known 
 
208 ENTOMOLOGY 
 
 to be immune from the attacks of birds — as descril^ed beyond. 
 In this way. as \\'allace sug-gests. the egg--laden females may 
 escape destruction, as they shiggishly seek the proper plants 
 upon which to lay their eggs. Here would be a fair field for 
 the operation of natural selection. 
 
 In most insects, however, sexual differences in coloration 
 are apparently of no protective value and are usually so trivial 
 and variable as probably to be of no use for recognition pur- 
 poses. The usual statement that these differences facilitate 
 sexual recognition is a pure assumption, in the case of insects, 
 and one that is inadec|uate in spite of its plausibility, for (i) 
 it is extremely improbable from our present knowledge of 
 insect vision that insects are able to perceive colors except in 
 the broadest way. namely, as masses; (2) the great majority 
 of insect species show no sexual differences in coloration; (3) 
 when colorational antigeny is present it is probably unneces- 
 sary, to say the least, for sexual recognition. Thus, n(jtwith- 
 standing the marked dissimilarity of coloration in the two 
 sexes of C. proincthea, the males, guided by an odor, seek out 
 their mates even when the wings of the female have been am- 
 putated and male Avings glued in their place, as Alayer found. 
 
 Hence, when useless, colorational antigeny cannot have 
 been developed by natural selection and may be due simply 
 to the extended action of the same forces that have produced 
 variety of coloration in general. 
 
 Origin of Color Patterns. — Tower, who has written an 
 important work on the C(3lors and color patterns of Coleop- 
 tera, finds that each of the black spots on the pronotum of the 
 Colorado potato beetle (Fig. 237) " is developed in connection 
 with a muscle, and marks the point of attachment of its fibers to 
 the cuticula." Thus the color pattern, in its origin, is not neces- 
 sarily useful. This point is so important that we cjuote Tow- 
 er's conclusions in full. " The most important and widely 
 disseminated of insect colors are those of the cuticula . . . 
 these colors develop as the cuticula hardens, and appear first, 
 as a rule, upon sclerites to which muscles are attached. In 
 
COLOR AND COLORATION 2O9 
 
 one of the earlier sections of this paper I showed that the pig- 
 ment develops from Ijefore Imckwanl and, approximately, by 
 segments, excepting that it may appear npon the head and 
 most posterior segments simultaneously. 
 
 " In ontogeny color appears first, as a rule, over the muscles 
 which become active first, or upon certain sclerites of the body. 
 These are usually the head muscles, although exceptions are 
 not infrequent. It should be remembered that as the color 
 appears the cuticula hardens, and, considering" that muscles 
 must ha^■e fixed ends for their action, it seems that there is a 
 definite relation between the development of color, the hard- 
 ening of the cuticula, and the beginning of muscular activity ; 
 the last being dependent upon the second, and, incidentally, 
 accompanied by the first. As muscular activity spreads over 
 the animal the cuticula hardens and color appears, so that 
 color is nearly, if not wholly, segmentally developed. 
 
 " The relation which exists between cuticular color and the 
 stiffening of the cuticula is thus a physiological one, the cutic- 
 ula not being able to harden without becoming yellow or 
 brown. \\'hat bearing has this upon the origin of color pat- 
 terns? In the lower forms of tracheates, such as the Myria- 
 pods, colors appear as segmental repetitions of spots or pig- 
 mented areas which mark either important sclerites or muscle 
 attachments. On the abdomens of insects, where segmenta- 
 tion is best observed, color appears as well-defined, segmen- 
 tally arranged spots, but on the thorax segmentation is ob- 
 scured and lost upon the head. Of what importance, then, is 
 pigmentation? x'Vnd how did it arise? If the ontogenetic 
 stages offer any basis for phylogenetic generalization, we may 
 conclude that cuticula color originated in connection wdth the 
 hardening of the integiunent of the ancestral tracheates as 
 necessary to the muscular activity of terrestrial life. The 
 primitive colors were yellows, browns and blacks, correspond- 
 ing well with the surroundings in which the first terrestrial 
 insects are supposed to have lived. The color pattern was a 
 segmental one, showing repetition of the same spots upon suc- 
 cessive segments, as upon the abdomen of Coleoptera. 
 '5 
 
2 10 ENTOMOLOGY 
 
 " So firmly have these characters become ingrained in the 
 tracheate series, and so important is this relation of the hard- 
 ening of the cuticula to the musculature and to the formation 
 of body sclerites, that even the most specialized forms show 
 this primitive system of coloration; and, although there may 
 be spots and markings which have no connection with it, still 
 the chief color areas are thus closely associated." 
 
 Development of Color Patterns. — Although the causes of 
 coloration are, for the most part, obscure, it is possible, never- 
 theless, to point out certain paths along which coloration ap- 
 pears to have developed. These paths have been determined 
 by the comparison of color patterns in kindred groups of in- 
 sects and the study of colorational variations in adults of the 
 same species. The development of coloration in the individ- 
 ual, however, has as yet received but little attention — excepting 
 the excellent studies of Mayer and of Tower. Butterflies, 
 moths and beetles have naturally been preferred by most stu- 
 dents of the subject. 
 
 The most primitive colors among moths are uniform dull 
 yellows, browns and drabs — the same colors that the pupal 
 blood assumes when it is dried in the air. These simple col- 
 ors prevail on the hind wings of most moths and on the less 
 exposed parts of the wings of highly colored butterflies. The 
 hind wings of moths are, as a rule, more primitively colored 
 than the front ones because, as Scudder says, " all dififeren- 
 tiation in coloring has been greatly retarded by their almost 
 universal concealment by day beneath the overlapping front 
 wings." Exceptions to this statement are found in Geomet- 
 ridae and such other moths as rest with all the wings spread. 
 " In such hind wings we find that the simplest departure from 
 uniformity consists in a deepening of the tint next the outer mar- 
 gin of the wing; next we have an intensification of the deeper 
 tint along a line parallel to the margin ; it is but a step from this 
 condition to a distinct line or band of dark color parallel to 
 the margin. Or the marginal shade may, in a similar way, 
 break up into two or more transverse and parallel submarginal 
 
COLOR AND COLORATION 2 I I 
 
 lines, a very common style of ornamentation, especially in 
 moths. Or, again, starting- with the snbmarg-inal shade, this 
 may send shoots or tongiies of dark color a short distance 
 toward the base, giving- a serrate inner border to the marginal 
 shade; when now this breaks np into one, two, or more lines 
 or narrow stripes, these stripes become zigzag, or the inner 
 ones may be zigzag, while the outer ones are plain — a very 
 common phenomenon. 
 
 " A basis such as this is sufficient to account for all the modi- 
 fications of simple transverse markings which adorn the wings 
 of Lepidoptera." 
 
 Briefly, one or more liands may break up into spots or bars, 
 the breaks occurring either between the veins or, more com- 
 monly, at the veins ; and in the latter event, short bars or more 
 or less quadrate or rounded spots arise in the interspaces. 
 From simple round spots there may develop, as Darwin and 
 others have shown, many-colored eye-like spots, or ocelli. 
 
 ]\Iayer gives the following laws of color pattern : " (a) Any 
 spot found upon the wing of a butterfly or moth tends to be 
 bilaterally symmetrical, both as regards form and color; and 
 the axis of symmetry is a line passing through the center of 
 the interspace in which the spot is found, parallel to the longi- 
 tudinal nervures. (b) Spots tend to appear not in one inter- 
 space only, but in homologous places in a row of adjacent 
 interspaces, (c) Bands of color are often made by the fusion 
 of a row of adjacent spots, and, conversely, chains of spots are 
 often formed by the breaking up of bands, (d) When in 
 process of disappearance, bands of color usually shrink away 
 at one end. (c) The ends of a series of spots are more vari- 
 able than the middle. (/) The position of spots situated near 
 the outer edges of the wing is larg'ely controlled by the wing- 
 folds or creases." 
 
 These results have Ijeen arrived at chiefly by the study of 
 the variations presented by color patterns. 
 
 Variation in Coloration. — It is safe to say that no two 
 insects are colored exactly alike. Some species, however, are 
 
m 
 
 10 
 
 
 12 
 
 13 
 
 14 
 
 ^>:uu 
 
 16 
 
 Colorational variations of the pronotum of the Colorado potato beetle, Leptinotar 
 deccmlineata. 
 
Fig. 238. 
 
 18 
 
 Elytral color patterns of species of Cicindela. 1-8 illustrate reduction of dark area; 
 ^14, extension of dark area; 15, 16, formation of longitudinal vitta; 17, 18, linear 
 extension of markings. I, C. vulgaris; 2, generosa; 3, generosa; 4, pamphila; 5, lim- 
 bata; 6, togata; 7, gratiosa; 8, canosa; g, tenuisignata; 10, marginipennis; 11, hentzii; 
 12, sexguttata; 13, hemorrhagica; 14, splendida; 15, imperfecta; 16, lemniscata; 
 17, gabbii; 18, sanlcyi. — After Horn, from Entomological News. ^21^) 
 
214 ENTOMOLOGY 
 
 far more variable than others. Catocala ilia, for example, 
 occurs under more than fifty varieties, each of which might 
 be given a distinctive name, were it not for the fact that these 
 varieties run into one another. One may examine hundreds 
 of potato beetles (L. decemlincata) without finding any two 
 that have precisely the same pattern on the pronotum. The 
 range of this variation in this species is partially indicated in 
 Fig. 237, and that of Cicindela in Fig. 238. 
 
 Individuals of Cicindela vary in pattern in a few definite 
 directions, and the patterns that characterize the various spe- 
 cies appear to be fixations of individual variations. In the 
 words of Dr. Horn: " (i) The type of marking is the same 
 in all our species. (2) Assuming a well-marked species {vul- 
 garis, Fig. 238, i) as a central type, the markings of other 
 species vary from that type, {a) by a progressive spreading 
 of the white, (&) by a gradual thinning or absorption of the 
 white, (c) by a fragmentation of the markings, {d) by linear 
 supplementary extension. (3) Many species are practically 
 invariable (/. e., the individual variations are small in amount 
 as compared with those in other species). These fall into two 
 series : (a) those of the normal type, as vulgaris, hirticollis 
 and tenuisignata; (b) those in which some modification of the 
 type has become permanent, probably through isolation, as 
 marginipennis, to gala and lemniscata. (4) Those species 
 which vary do so in one direction only." New types of pat- 
 tern, of specific value, appear to have arisen by the isolation 
 and perpetuation of individual variations. 
 
 Variations in general fall into two classes: continuous {in- 
 dividual variations) and discontinuous {sports). The former 
 are always present, are slight in extent and intergrade with 
 one another; they are distributed symmetrically about a mean 
 condition. The latter are occasional, of considerable extent 
 and sharply separated from the normal condition. 
 
 Replacements.- — Examples of the replacement of one color 
 by another are familiar to all collectors. The red of Vanessa 
 atalanta and Coccinellidje may be replaced by yellow. These 
 
COLOR AND COLORATION 21 5 
 
 two colors in many butterflies and l:)eetles are due to pig^ments 
 that are closely related to each other chemically. Thus in the 
 chrysomelid Melasonia lapponica the beetle at emergence is 
 pale but soon becomes yellow with black markings, and after 
 several hours, under the influence of sunlight, the yellow 
 changes to red ; the change may be prevented, however, by keep- 
 ing the beetle in the dark. After death, the red fades back 
 through orange to yellow, especially as the result of exposure 
 to sunlight. Yellow in place of red, then, may Ije attributed 
 to an arrested development of pigment in the living insect and 
 to a process of reduction in the dead insect, metabolism having 
 ceased. 
 
 Yellow and green are similarly related. The stripes of 
 Pa-cilocapsiis lincatits are yellow before they become green, and 
 after death fade back to yellow. As the green pigment in most, 
 if not all, phytophagous insects is chlorophyll, these color 
 changes are probably similar to those that occur in leaves. 
 Leaves grown in darkness are yellow, from the presence of etio- 
 lin, and do not turn green until they are exposed to sunlight (or 
 electric light), without which chlorophyll does not develop; 
 and as metabolism ceases, chlorophyll disintegrates, as in 
 autumn, leaving its yellow constituent, xanthophyll, which is 
 very likely the same substance as etiolin. 
 
 Cicindela sexguttata and Calosoma scrutator are often blue 
 in place of green. Here, however, these colors are structural, 
 and their variations are to be attributed to slight differences in 
 the spacing of the surface elevations or depressions. 
 
 Green grasshoppers occasionally become pink toward the 
 close of summer. No explanation has been offered for this 
 phenomenon, though it may be remarked that when grasshop- 
 pers are killed in hot water the normal green pigment turns to 
 pink. 
 
 These changes of color are apparently of no use to the insect, 
 being merely incidental effects of light, temperature or other 
 inorganic influences. 
 
CHAPTER VI 
 
 ADAPTIVE COLORATION 
 
 Protective Resemblance. — Every naturalist knows of 
 many animals that tend to escape detection by resembling their 
 surroundings. This phenomenon of protective reseinhlancc 
 is richly exemplified by insects, among which one of the most 
 remarkable cases is furnished by the Kalliina butterflies, espe- 
 cially K. inachis of India and K. paraklcta of the Malay Archi- 
 pelago. The former species (Fig. 239) is conspicuous when 
 
 Fig. 239. 
 
 A, upper surface; 
 
 ', with wings closed, showing resemblance to a 
 leaf. X i. 
 
 on the wing; its bright colors, however, are confined to the 
 upper surfaces of the wings, and when these are folded to- 
 gether, as in repose, the insect resembles to perfection one of 
 the dead leaves among which it is accustomed to hide. The 
 form, size and color of the leaf are accurately reproduced, the 
 petiole being simulated by the tails of the wings. Two paral- 
 lel shades, one light and one dark, represent, respectively, 
 
 216 
 
ADAPTIVE COLORATIOX 
 
 217 
 
 the illuminated and the shaded side of a mid-rib. and the side- 
 veins as well are imitated ; there are even small scattered black 
 spots resembling- those made on the leaf by a species of 
 fungus. Furthermore, the butter tly ha])itually rests, not 
 among green leaves, where it would be conspicuous, but among 
 leaves with wdiich it har- 
 
 , . Vu;. 240. 
 
 monizes ni coloration. 
 Notwithstanding a recent 
 discussion as to whether 
 it usually rests in pre- 
 cisely the same position 
 as a leaf, this insect cer- 
 tainly deceives experi- 
 enced entomologists and 
 presumably eludes birds 
 and other enemies by 
 means of its deceptive 
 coloration. 
 
 Some of the tropical 
 Phasmidse counterfeit 
 sticks, green leaves, or 
 dead leaves with minute 
 accuracy. Our common 
 phasmids, Diaphcrorncra 
 fcuiorata and veliei (Fig. 
 240), are well known as 
 " stick insects " ; indeed, 
 it is not necessary to go 
 beyond the temperate zone 
 to find plenty of examples 
 of protective resemblance. Geometrid caterpillars imitate twigs, 
 holding the body stiffly from a branch and frequently reprodu- 
 cing the form and coloration of a twig with striking exactitude ; 
 and the moths of the same family are often colored like the 
 bark against which they spread their wings. Even more per- 
 fectly do the Catocala moths resemble the bark upon which 
 
 Diapheromcra relic 
 
 Natural size. 
 
2l8 
 
 ENTOMOLOGY 
 
 they rest (Fig-. 241), with their conspicuous and usually showy 
 hind wings concealed under the protectively colored front 
 wings. The caterpillars of Basilarchia archippus and Pa- 
 pilio thoas, as well as other larvse and not a few moths, 
 resemble closelv the excrements of birds. Numerous grass- 
 
 FiG. 241 
 
 Catocala lacrymosa; A, upper surface; B, with 
 Reduced. 
 
 igs closed, and resting on bark. 
 
 eating caterpillars are striped with green, as is also a sphingid 
 species (Ellcina harrisii) that lives among pine needles. The 
 large green sphinx caterpillars perhaps owe their inconspicu- 
 ousness partly to their oblique lateral stripes, which cut a mass 
 of green into smaller areas. The caterpillar of Schizura 
 ipoiiKrcc (Fig. 242), which is green with brown patches, rests 
 
ADAPTIVE COLORATION 
 
 219 
 
 for hours along" the eaten or torn edge of a basswood leaf, in 
 which position it bears an extremely deceptive resemblance to 
 the partially dead border of a leaf. The weevils that drop to 
 the ground and remain immovable are often indistinguishable 
 
 Fig. 242. 
 
 Caterpillar of ScliKitni ipouia-a: clinging to a torn leaf. Natural size. 
 
 to the collector on account of their likeness to bits of soil or 
 little pebbles. Everyone has noticed the extent to which some 
 of the grasshoppers resemble the soil in color; Triiiicrotropis 
 maritima is practically invisible against the gray sand of the 
 seashore or other places to which it restricts itself; and Dis- 
 sostevra Carolina, which varies greatly in color, ranging from 
 ashy gray to yellowish or to reddish brown, is commonly found 
 on soil of its own color. 
 
 Adventitious Resemblance. — If, instead of hastily ascrib- 
 ing all cases apparently of protective resemblance to the action 
 of natural selection, one inquires into the structural basis of 
 the resemblance in each instance, it is found that some cases 
 can be explained, with(.)ut the aid of natural selection, as being 
 
220 ENTOMOLOGY 
 
 direct effects of food, light or other primary factors. Such cases, 
 then, are in a sense accidental. For example, many inconspic- 
 uous green insects are green merely because chlorophyll from 
 the food-plant tinges the blood and shows through the skin. 
 If it be argued that natural selection has brought about a thin 
 and transparent skin, it may be replied that the skin of a green 
 caterpillar is by no means exceptional in thinness or trans- 
 parency. Moreover, many leaf-mining caterpillars are green, 
 simply because their food is green ; for, living as they do within 
 the tissues of leaves, and surrounded by chlorophyll, their own 
 green color is of no advantage, but is merely incidental. 
 
 Ag'ain, in the " protectively " colored chrysalides experi- 
 mented upon by Poulton, their color was directly influenced 
 by the prevailing color of the light that surrounded the larva 
 during the last few days before pupation. Of course, it is 
 conceivable that natural selection may have preserved such in- 
 dividuals as were most responsive to the stimulus of the sur- 
 rounding- light ; nevertheless the fact remains that these resem- 
 blances do not demand such an explanation, which is, in other 
 words, superfluous. 
 
 Indeed, a great many of the assumed examples of "protec- 
 tive resemblance " are very far-fetched. On the other hand, 
 when the resemblance is as specific and minutely detailed as it 
 is in the Kallima butterflies — where, moreover, special instincts 
 are involved — the phenomenon can scarcely be due to chance ; 
 the direct and uncombined action of such factors as food or 
 light is no longer sufticient to explain the facts — although these 
 and other factors are undoubtedly important in a primary, or 
 fundamental, way. Here natural selection becomes useful, as 
 enabling us to understand how original variations of structure 
 and instinct in favorable directions may have been preserved 
 and accumulated until an extraordinary degree of adaptation 
 has been attained. 
 
 Value of Protective Resemblance. — The popular opinion 
 as to the efficiency of protective resemblances is undoubtedly 
 an exaggerated one, owing mainly to the false assumption that 
 
ADAPTIVE COLORATION 221 
 
 the senses of the Ic^wcr animals are C()-extensi\-e in range 
 with our own. As a matter of fact, l)ir(ls detect insects with 
 a facihty far superior to that of man, and destroy them hy 
 the wholesale, in spite of protective coloration. Thus, as 
 Judd has ascertained, no less than three hundred species of 
 birds feed ui)on protectively colored g-rasshopi)ers, which they 
 destrov in immense numbers, and more than twenty species 
 prey upon the twig-like geometrid larvae ; while the weevils 
 that look like particles of soil, and the green-striped caterpillars 
 that assimilate with the surrounding" foliage are constantly to 
 be found in the stomachs of birds. 
 
 After all, however, protective resemblance may be regarded 
 as advantageous upon the whole, even if it is inefTectual in 
 thousands of instances. An adaptation may be successful 
 even if it does fall short of perfection; and it should be borne 
 in mind that the evolution of protective resemblances among 
 insects has probably been accompanied on the part of birds by 
 an increasing ability to discriminate these insects from their 
 surroundings. 
 
 Warning Coloration. — In strong contrast to the protec- 
 tively colored species, there are many insects which are so 
 vividly colored as to be extremely conspicuous amid their nat- 
 ural surroundings. Such are many Hemiptera (Lygcuus, 
 Miirgantia), Coleoptera {Nccroplionis, Lampyridae, Coccinel- 
 lidc-e, Chrysomelidae), Hymenoptera (Mutillidae, Vespidse), 
 and numerous caterpillars and butterflies. Conspicuous col- 
 ors, being frecjuently — though not always — associated with 
 c|ualities that render their possessors unpalatable or offensive 
 to birds or other enemies, are advantageous if, by insuring 
 ready recognition, they exempt their owners from attack. 
 
 Efficiency of Warning Colors. — Owing to much disagree- 
 ment as to the actual value of " warning " colors, several in- 
 vestigators have made many observations and experiments 
 upon the subject. Tests made by offering various conspicu- 
 ous insects to birds, lizards, frogs, monkeys and other insec- 
 ti^'orous animals have given diverse results, according to cir- 
 
222 ENTOMOLOGY 
 
 cumstances. Thus, one gaudy caterpillar is refused by a cer- 
 tain bird, at once, or else after being tasted, but another and 
 equally showy caterpillar is eaten without hesitation. Or, an 
 insect at first rejected may at length be accepted under stress 
 of hunger ; or a warningly colored form disregarded by some 
 animals is accepted by others. Moreover, some of the experi- 
 ments with captive insectivorous animals are open to objection 
 on the score of artificiality. 
 
 Nevertheless, from the data now accumulated, there emerge 
 some conclusions of definite value. Frank Finn, whose con- 
 clusions are quoted beyond, has foifnd in India that the con- 
 spicuous colors of some butterflies (Danainae, Acrcua violcc, 
 Delias eucharis, Papilio anstolochice) are probably effective 
 as " warning '' colors. Marshall found in South Africa that 
 mantids, which would devour most kinds of butterflies, includ- 
 ing warningly colored species, refused Acrcea, which appeared 
 to be not only distasteful but even unwholesome; Acrcea is 
 eaten, however, by the predaceous Asilidse, which feed indis- 
 criminately upon insects — for example, beetles, dragon flies and 
 even stinging Hymenoptera. The masterly studies of Mar- 
 shall and Poulton strongly support the general theory of warn- 
 ing coloration. 
 
 In this country, much important evidence upon the subject 
 has been obtained by Dr. Judd from an extensive examination 
 of the stomach-contents of birds, supplemented by experiments 
 and field observations. Judd says that Miirgantia histrionica 
 and other large showy bugs are usually avoided by birds ; that 
 the showy, ill-flavored Coccinellidss, and Chrysomelidas such 
 as the elm leaf beetle, Diabrotica, and Leptinotarsa {Dory- 
 phora) , possess comparative immunity from birds ; and that 
 Macrodacfyliis, Chauliogiiathus and Cyllcne are highly exempt 
 from attack. Such cases, he adds, are comparatively few 
 among insects, however, and in general, warning colors are 
 effective against some enemies but ineffective against others. 
 
 Generally speaking, hairs, stings and other protective de- 
 vices are accompanied by conspicuous colors — though there 
 
ADAPTIVE COLORATION 2 23 
 
 are many exceptions to this rnle. These warnino- colors, how- 
 ever, fail to accomplish their snpposed purpose in the follow- 
 ing- instances, given by Juckl. Taking insects that are thought 
 to be protected by an offensive odor or a disagreeable taste : 
 Heteroptera in general are eaten by all insectivorous birds, the 
 squash bug by hawks and the pentatomids by many birds ; 
 among Carabid.e with their irritating fluids, Harpalus caligi- 
 nosiis and poiiisyk'aniciis are food for the crow, catbird, robin 
 and six others; Carabits and Calosoiiia are relished by crows 
 and blackbirds; Silphid^e are taken by the crow, loggerhead 
 shrike and kingbird ; and Leptiiiotorsa dcceinlineata is eaten 
 by at least six kinds of birds : wood thrush, rose-breasted gros- 
 beak, quail, crow, cuckoo and catbird. Of hairy and spiny cat- 
 erpillars, Arctiid?e are eaten by the robin, bluebird, catbird, 
 cuckoo and others ; the larvae of the .gypsy moth are food for 
 the blue-jay, robin, chickadee, Baltimore oriole and many 
 others [thirty-one birds, in Massachusetts] ; and the spiny 
 caterpillars of Vanessa antiopa are taken by cuckoos and ori- 
 oles. Of stinging Hymenoptera, bumble bees are eaten by the 
 bluebird, blue-jay and two flycatchers ; the honey bee. by the 
 wood pewee, phoebe, olive-sided flycatcher and kingbird; 
 Andrena by many birds, and Vespa and Polistes by the red- 
 bellied woodpecker, kingbird, and yellow-bellied flycatcher. 
 
 These facts by no means invalidate the general theory, but 
 they do show that " disagreeable " qualities and their associ- 
 ated color signals are of little or no avail against some enemies. 
 The weight of evidence favors the theory of warning colora- 
 tion in a qualified form. A\'hile cxDnspicuous colors do not 
 ahvays exempt their owners from destruction, they frequently 
 do so, by advertising disagreeable attributes of one sort or 
 another. 
 
 The evolution of warning coloration is explained by natural 
 selection ; in fact, we have no other theory to account for it. 
 The colors themselves, however, must have been present before 
 natural selection could begin to operate; their origin is a ques- 
 tion quite distinct from that of their subsequent preservation. 
 
2 24 
 
 ENTOMOLOGY 
 
 Protective Mimicry. — This interesting and highly involved 
 phenomenon is a special form of protective resemblance in 
 which one species imitates the appearance of another and 
 
 Fig. 243. 
 
 A, Anosia plc.vil^piis, the " model 
 
 ilarcliia architf's, the " mimic. 
 
 better protected species, thereby sharing its immunity from 
 destruction. Though it attains its highest development in the 
 tropics, mimicry is well illustrated in temperate regions. A 
 familiar example is furnished by Basilarchia archippiis (Fig. 
 243, B) , which departs widely from the prevailing dark colora- 
 tion of its p-enus to imitate the milkweed buttertiv, Anosia 
 
ADAPTIVE COLORATION 
 
 !25 
 
 plcxippus. The latter species, or " model," appears to be un- 
 molested l)y birds, and the former species, or " mimic," is 
 thought to secure the same exemption from attack by being 
 mistaken for its unpalatable model. The common drone-fly, 
 Eristdlis tciiax ( I'ig. 244, B) mimics a honey bee in form, size, 
 
 ViG. 244. 
 
 Protective mimicry. 
 
 A, drone bee, Apis mellifcra; B, drone fly, Erislalis teiiax. 
 Natural size. 
 
 coloration and the manner in which it buzzes about flowers, 
 in company with its model ; it does not decei^•e the kingbird 
 and the flicker, however. Some Asilidx are remarkably like 
 bumble bees in superficial appearance and certain Syrphus flies 
 mimic wasps with more or less success. The beetle Casnonia 
 bears a remarkable resemblance to the ants with which it lives. 
 The classic cases are those of the Amazonian Heliconiidse 
 and Pieridae, in which mimicry was first detected by Bates. 
 The Heliconiidas (Frontispiece, Fig. i) are abundant, vividly 
 colored and eminently free from the attacks of birds and other 
 
 and taste. Some of the Pierid?e — a family fundamentally dif- 
 ferent from Heliconiidse — imitate (Frontispiece, Fig. 2) the 
 protected HeliconiidcC so successfully, in coloration, form and 
 flight, that while other Pieridse are preyed upon by many foes, 
 the mimicking species tend to escape attack. 
 
 The family Heliconiidse, referred to by Bates, comprised 
 what are now known as the subfamilies Heliconiin?e, Itho- 
 miinre and Danaina? ; similarly, Pieridre and Papilionidse are 
 16 
 
2 26 ENTOMOLOGY 
 
 now often termed respectively Pierinae and Papilioninae. 
 Ithomiinse are mimicked also by Papilioninae and by moths of 
 the families Castniidse and Pericopidae. 
 
 The discoveries of Bates in tropical South America were 
 paralleled and supported by those of \\'allace in India and the 
 Malay Archipelago (where Danainae are the chief " models "), 
 and of Trimen in South Africa (where Acrseinae and Danain?e 
 serve as models). Trimen discovered a most remarkable case, 
 in which three species of Danainae are mimicked, each by a 
 distinct variety of the female of Papilio mcropc (Frontispiece, 
 Fig-s. 5-11). 
 
 So much for that kind of mimicry — but how is the following 
 kind to be explained? The Ithomiinas of the i\mazon valley 
 have the same form and colorationas the Hehconiinse (Frontis- 
 piece, Figs. I, 4), but the Ithomiinse themselves are already 
 highly protected. The answer is that this resemblance is of 
 advantage to both groups, as it minimizes their destruction by 
 birds — these having to learn but one set of warning signals 
 instead of two. This is the essence of Aliiller's famous expla- 
 nation, which will presently be stated with more precision. 
 There are two kinds of mimicry, then : ( i ) the kind described 
 by Bates, in which an edible species obtains security by coun- 
 terfeiting the appearance of an inedible species; (2) that ob- 
 served by Bates and interpreted by ]\Iuller, in which both 
 species are inedible. These two kinds are known respectively 
 as Batesian and ]\Iullerian mimicry, though some writers prefer 
 to limit the term mimicry to the Batesian type. 
 
 Wallace's Rules. — The chief conditions under which mimi- 
 cry occurs have been stated by Wallace as follows : 
 
 " I. That the imitative species occur in the same area and 
 occupy the very same station as the imitated. 
 
 " 2. That the imitators are always the more defenceless. 
 
 '' 3. That the imitators are always less numerous in indi- 
 viduals. 
 
 " 4. That the imitators differ from the bulk of their allies. 
 
 " 5. That the imitation, however minute, is external and 
 
ADAPTIVE COLORATION 22/ 
 
 visible only, never extending to internal characters or to such 
 as do not affect the external appearance." 
 
 These rules relate chiefly to the Batesian form of mimicry 
 and need to be altered to apply to the Miillerian kind. 
 
 The first criterion given by Wallace is evidently an essential 
 one and it is sustained by the facts. It is also true that mimic 
 and model occur usually at the same time of year ; Marshall 
 found many new instances of this in South Africa. In some 
 cases of mimicry, strange to say, the precise model is unknown. 
 Thus some Nymphalid?e diverge from their relatives to mimic 
 the Euploeina?, though no particular model has been found. 
 In such instances, as Scudder suggests, the prototype may 
 exist without having been found; may have become extinct; 
 or the species may have arrived at a general resemblance to 
 another group without having as yet acquired a likeness to 
 any particular species of the group, the general likeness mean- 
 while being profitable. 
 
 The second condition named by Wallace is correct for 
 Batesian but not for Miillerian mimicry. 
 
 The fulfilment of the third condition is requisite for the 
 success of Batesian mimicry. Bates noted that none of the 
 pierid mimics were so abundant as their heliconiid models. 
 If they were, their protection would be less ; and should the 
 mimic exceed its model in numbers, the former would be more 
 subject to attack than the latter. Sometimes, indeed, as 
 Miiller found, the mimic actually is more common than the 
 model ; in which event, the consequent extra destruction of the 
 mimic would — at least theoretically — reduce its numbers back 
 to the point of protection. 
 
 In ]^Iiillerian mimicry, however, the inevitable variation in 
 abundance of two or more converging and protected species is 
 far less disastrous ; though when two species, equally distaste- 
 ful, are involved, the rarer of the two has the advantage, as 
 Fritz Miiller has shown. His lucid explanation is essentially 
 as follows : 
 
 Suppose that the birds of a region have to destroy 1,200 
 
2 28 ENTOMOLOGY 
 
 butterflies of a distasteful species before it becomes recognized 
 as such, and that there exist in this region 2,000 individuals 
 of species A and 10,000 of species B ; then, if they are diif event 
 in appearance, each will lose 1,200 individuals, but if they are 
 deceptively alike, this loss will be divided among them in pro- 
 portion to their numbers, and A will lose 200 and B 1,000. A 
 accordingly saves 1,000, or 50 per cent, of the total number 
 of individuals of the species, and B saves only 200, or 2 per 
 cent. Thus, while the relative numbers of the two species are 
 as I to 5, the relative advantage from their resemblance is as 
 25 to I. 
 
 If two or more distasteful species are equally numerous, 
 their resemblance to one another brings nearly equal advan- 
 tages. In cases of this kind — and many are known — it is 
 sometimes impossible to distinguish between model and mimic, 
 as all the participants seem to have converged toward a com- 
 mon protective appearance, through an interchange of features 
 — the " reciprocal mimicry " of Dr. Dixey. 
 
 From this explanation, the superior value of Miillerian as 
 compared with Batesian mimicry is evident. 
 
 The fourth condition — that the imitators differ from the 
 bulk of their allies — holds true to such a degree that even the 
 two sexes of the same species may differ extremely in colora- 
 tion, owing to the fact that the female has assumed the like- 
 ness of some other and protected species. The female of 
 Papilio merope, indeed, occurs (as was just mentioned) under 
 three varieties, which mimic respectively three entirely dissim- 
 ilar species of Danainre, and none of the females are any- 
 thing like their male in coloration (Frontispiece, Figs. 5-1 1). 
 The specific identity of these four South African varieties of 
 merope has been established by Trimen, Marshall and other 
 investigators. 
 
 The generally accepted explanation for these remarkable 
 but numerous cases in which the female alone is mimetic, is 
 that the female, burdened with eggs and consequently sluggish 
 in flight and much exposed to attack, is benefited by imitating 
 
ADAPTIVE COLORATION 229 
 
 a species which is ininnine; while the male has had no such 
 incentive — so to speak — to become mimetic. Of course, there 
 has been no conscious evolution of mimicry. 
 
 Wallace's iifth stipulation is important, but should read this 
 way: ''The imitation, however minute, is but external and 
 visible itsiiaHy, and never extends to internal characters zvliich 
 do not affect the external appearance." J^'or, as Poulton 
 points out, the alertness of a beetle which mimics a wasp, 
 implies appropriate changes in the nervous and muscular sys- 
 tems. In its intent, however, Wallace's rule holds good, and 
 by disregarding it some w-riters strain the theory of mimicry 
 beyond reasonable limits. Some have said, for example, that 
 the resemblance between caddis flies and moths is mimicry; 
 when the fact is that this resemblance is not merely superficial 
 but is deep-seated; the entire organization of Trichoptera 
 shows that they are closely related to Lepidoptera. This like- 
 ness expresses, then, not mimicry, but ai^nity and parallel 
 development. The same objection applies to the assumed 
 cases of mimicry within the limits of a single family, as be- 
 tween two genera of Heliconiidse or between the chrysomelid 
 genera Leuia and Diahrotica. The nearer two species are 
 
 related to each other, the more probable 
 
 1 1 1 • ■ -1 • ■ 1 Fig. 245. 
 
 it becomes that then" smiilarity is due — 
 
 not to mimicry — but to their common 
 
 ancestry. 
 
 On the other hand, the resemblance 
 
 frequently occurs between species of such 
 
 -,• ^c , ■ , . , ., A locustid, Alvnnc- 
 
 diiterent orders that it cannot be attrib- cophana faiiax, which 
 uted to affinity. Illustrations of this are ^"^"^"es an ant. Twice 
 
 -^ natural length. From 
 
 the mimicry of the honey bee by the brunner von wat- 
 
 ^ n ^ 1 1 • • TENWYL. 
 
 drone fly, and the many other instances m 
 which stinging Hymenoptera are counterfeited by harmless 
 flies or beetles. A locustid of the Soudan resembles an ant 
 (Fig. 245), and the resemblance, by the w-ay, is obtained in a 
 most remarkable manner. Upon the stout body of this or-r 
 thopteron the abdomen of an ant is delineated in black, the rest 
 
230 ENTOMOLOGY 
 
 of the body being light in color and inconspicuous by contrast 
 with the black. Indeed the various means by which a super- 
 ficial resemblance is brought about between remotely related 
 insects are often extraordinary. 
 
 Irrespective of affinity, insects of diverse orders may con- 
 verge in wholesale numbers toward a central protected form. 
 The most complete examples of this have recently been brought 
 to light by ]\Iarshall and Poulton, in their splendid work on 
 the bionomics of South African insects, in which is given, for 
 instance, a colored plate showing how closely six distasteful 
 and dominant beetles of the genus Lyciis are imitated by nearly 
 forty species of other genera — a remarkable example of con- 
 vergence involving no less than eighteen families and five or- 
 ders, namely, Coleoptera, Hymenoptera, Hemiptera, Lepidop- 
 tera and Diptera. Excepting a few unprotected, or Batesian, 
 mimics (a fly and two or three beetles.), this association is 
 one between species that are already protected, by stings, bad 
 tastes or other peculiarities. In other words, here is Miiller- 
 ian mimicry on an immense scale ; and if Miillerian mimicry 
 is profitable when only two species are concerned, what an 
 enormous benefit it must be to each of forty participants ! 
 
 Strength of the Theory. — Evidently the theory of mimicry 
 rests upon the assumption that the mimics, by virtue of their 
 mimicry, are specially protected from insectivorous foes. Un- 
 til the last few years, however, there was altogether too little 
 positive evidence bearing upon the assumption itself, though 
 this was supported by such scattered observations as were 
 available. The oft-repeated assertion that this lack of evi- 
 dence was due simply to inattention to the subject, has been 
 proved to be true by the decisive results recently gained in the 
 tropics by several competent investigators who have been able 
 to give the subject the requisite amount of attention. 
 
 From his observations and experiments in India, Frank 
 Finn concludes : 
 
 " I. That there is a general appetite for butterflies among 
 insectivorous birds, even though they are rarely seen when 
 wild to attack them. 
 
ADAPTIVE COLORATION 23 I 
 
 '' 2. That many, probably most species, dislike, if not in- 
 tensely, at any rate in comparison with other butterflies, the 
 warningly-colored Danainae, Acrcca violcc, Delias eucharis, and 
 Papilio aristolocliicc; of these the last being- the most distaste- 
 ful, and the Danainae the least so. 
 
 " 3. That the mimics of these are at any rate relatively 
 palatable, and that the mimicry is commonly effectual under 
 natural conditions. 
 
 " 4. That each bird has separately to acquire its experience, 
 and well remembers what it has learned. 
 
 " That therefore on the whole, the theory of Wallace and 
 Bates is supported by the facts detailed in this and my former 
 papers, so far as they deal with birds (and with the one mam- 
 mal used). Professor Poulton's suggestion that animals may 
 be forced by hunger to eat unpalatable forms is also more 
 than confirmed, as the unpalatable forms were commonly eaten 
 without the stimulus of actual hunger — generally, also, I may 
 add, without signs of dislike." 
 
 Though insects have many vertebrate and arthropod ene- 
 mies, it is probable that the evolution of mimetic resemblance, 
 implying warning coloration, has been brought about chiefly 
 by insectivorous birds. 
 
 Neglecting papers of minor importance, we may pass at 
 once to the most important contribution upon this subject — 
 the voluminous w^ork of Marshall and Poulton upon mimicry 
 and warning colors in South African insects. These investi- 
 gators have found that birds are to be counted as the principal 
 enemies of butterflies; that the Danainae and Acrseinse, which 
 are noted as models, are particularly immune from destruc- 
 tion, while unprotected forms suffer; and that mimicking, 
 though palatable species, share the freedom of their models. 
 The same is true of beetles, of which Coccinellidae, Mala- 
 codermidre (notably Lyciis) , Cantharidse and many Chryso- 
 melidcC serve as models for many other Coleoptera, being 
 " conspicuous and constantly refused by insect-eaters." In 
 short, the splendid work of Marshall and Poulton tends to 
 
232 ENTOMOLOGY 
 
 place the theory of Batesian and Miillerian mimicry upon a 
 substantial foundation of observational and experimental 
 evidence. 
 
 In regard to the important cjuestion — do birds avoid un- 
 palatable insects instinctively or only as the result of experi- 
 ence — the evidence is all one way. Several investigators, in- 
 cluding Lloyd Morgan, have found that newly-hatched birds 
 have no instinctive aversions as regards food, but test every- 
 thing, and (except for some little parental guidance) are 
 obliged to learn for themselves what is good to eat and what 
 is not. This experimental evidence that the discrimination of 
 food by birds is due solely to experience, was evidently highly 
 necessary to place the theory of mimicry — especially the Miil- 
 lerian theory — upon a sound basis. 
 
 Though butterflies as a group are much subject to the at- 
 tacks of birds in the tropics, there are very few recorded in- 
 stances of this for our temperate region. It may then be 
 asked, what advantage does the " viceroy " (Fig. 243, B) gain 
 by resembling the " monarch," in a region where all butter- 
 flies are exempt from destruction by birds? In reply, it may 
 be said that the premise of the argument is as yet little more 
 than an assumption, because so little attention has been given 
 to the relations between birds and butterflies in our own coun- 
 try. Or, admitting the premise, it may be said that the resem- 
 blance was advantageous once, if not now ; and that in any 
 event, the departure of archippus from its congeners toward 
 one of the Danainic — a famous group of " models " in the 
 tropics — is unintelligible except as an instance of mimicry. 
 
 Granting that mimicry is upon the whole advantageous, it 
 becomes important to learn just how far the advantage ex- 
 tends ; and we find that mimicry is not of universal effective- 
 ness. Even the highly protected Heliconiina; and Danaina^ 
 are food for some predaceous insects. In this country, as 
 Judd has observed, the drone-fly (Erisfalis fciia.v), which 
 mimics the honey bee, is eaten by the kingbird and the phoebe; 
 the kingbird, indeed, eats the honey bee itself, but is said to 
 
ADAPTIVE COLORATION 233 
 
 pick out the drones; chickens also (hscriminate l)et\\een ch'ones 
 and workers, eating the former and avoicHng the latter. Bum- 
 ble bees and wasps, imitated by many other insects, are them- 
 selves eaten by the .kinoi)ird, catbird and several other birds, 
 thoug-h it is not known whether the stingless males of these 
 are singled out or not. Such facts as these do not discredit 
 the general theory of mimicry but point out its limits. 
 
 Evolution of Mimicry. — Natural selection gives an adequate 
 explanation of the e\-olution of a mimetic pattern. Before 
 accepting this explanation, however, we must inquire: (i) 
 What were the tirst stages in the development of a mimetic 
 pattern? (2) What evidence is there that every step in this 
 development was vitally useful, as the theory demands that it 
 should be ? These pertinent questions have been answered by 
 Darwin. Wallace, Miiller, Dixey and several other authorities. 
 
 The incipient mimic must have possessed, to begin with, col- 
 ors or patterns that were capable of mimetic development; 
 evidently the raw material must have been present. Now 
 IMiiller and Dixey in particular have called attention to the 
 fact that many pierids have at least touches of the reds, yellows 
 and other colors that are so conspicuous in the heliconids. 
 More than this, however, Dixey has demonstrated — as appears 
 clearly from his colored figures — a complete and gradual tran- 
 sition from a typical non-mimetic pierid, Pieris locusta, to the 
 mimetic pierid Mylothris pyrrha, the female of which imitates 
 Heliconius numata. He traces the transition chiefly through 
 the males of several pierid species — for the males, though for 
 the most part white (the typical pierid color), " show on the 
 under surface, though in varying degrees, an approach towards 
 the Heliconiine pattern that is so completely imitated by their 
 mates. These partially developed features on the under sur- 
 face of the males [compare Figs. 2 and 3 of Frontispiece] en- 
 able us to trace the history of the growth of the mimetic pat- 
 tern." Starting from Pieris lociisia, it is an easy step to 
 Mylothris lypera, thence to M. lorcna, and from this to the 
 mimetic M. pyrrha. '" Granted a beginning, howe\'er small, 
 
2 34 ENTOMOLOGY 
 
 such as the basal red touches in the normal Pierines, an elabo- 
 rate and practically perfect mimetic pattern may be evolved 
 therefrom by simple and easy stages." 
 
 Furthermore (in answer to the second cjuestion), it does not 
 tax the imagination to admit that any one of these color pat- 
 terns has — at least occasionally — been sufficiently suggestive 
 of the heliconid type to preserve the life of its possessor; espe- 
 cially when both bird and insect were on the wing and perhaps 
 some distance apart, when even a momentary flash of red or 
 yellow from a pierid might be enough to save it from attack. 
 
 It is highly desirable, of course, that this plausible explana- 
 tion should be tested as far as possible by observations in the 
 field and by experiments as well. 
 
 Adaptive Colors in General. — Several classes of adaptive 
 colors have been discriminated and defined by Poulton, whose 
 classification, necessarily somewhat arbitrary but nevertheless 
 very useful, is given below, in its abridged form. 
 
 I. APATETIC COLORS. — Colors resembling some part of the en- 
 vironment or the appearance of another species. 
 
 A. Cryptic Colors. — Protective and Aggressive Resemblances. 
 
 1. Procryptic colors. — Protective Resemblances. — Conceal- 
 
 ment as a protection against enemies. Example : Kal- 
 lima butterfly. 
 
 2. Anticryptic colors. — Aggressive Resemblances. — Conceal- 
 
 ment in order to facilitate attack. Example : Mantids 
 with leaf-like appendages. 
 
 B. PsEUDOSEMATic CoLORS. — False warning and signalling colors. 
 
 1. Pscudaposcmatic colors. — Protective ^Mimicry. Example: 
 
 Bee-like fly. 
 
 2. Pscudcpiscmatic colors. — Aggressive Mimicry and Allur- 
 
 ing Coloration. Examples : Volucclla, resembling bees 
 (Fig. 246) ; F'lower-like mantid. 
 II. SEMATIC COLORS.— Warning and Signalling Colors. 
 
 1. Aposematic colors. — Warning Colors. Examples: Gaudy 
 
 colors of stinging insects. 
 
 2. Episcmatic co/or.?.— Recognition IMarkings. 
 
 III. EPIGA^IIC COLORS.— Colors Displayed in Courtship. 
 
 Such of these classes as have not already been discussed 
 need brief reference. 
 
ADAPTIVE COLORATION 
 
 Fig. 246. 
 
 235 
 
 Aggressive mimicry. On the left, a bee, Rombiis iiiastniciUns; on tlic right, a fly, 
 Volucclla hombylans. Natural size. 
 
 Aggressive Resemblances. — The reseml:)lancc of a car- 
 ni\orons animal to its surroundings may not only be protec- 
 tive l)ut may also enable it to approach its prey undetected, as 
 in the case of the polar bear or the tiger. Among insects, 
 however, the occurrence of aggressive resemblance is rather 
 doubtful, even in the case of the leaf-like mantids. 
 
 Aggressive Mimicry. — Under this head are placed those 
 cases in which one species mimics another to which it is hostile. 
 The best known instance is furnished by European flies of the 
 genus Volucclla, whose larv?e feed upon those of bumble bees 
 and wasps. The flies bear a close resemblance to the bees, 
 owing to which it is supposed that the former are able to enter 
 the nests of the latter and lay their eggs. 
 
 Alluring Coloration. — The best example of this phenom- 
 enon is afforded by an Indian mantid, Gongylus gongyloidcs, 
 which resembles so perfectly the brightly colored flowers 
 among which it hides that insects actually fly straight into its 
 clutches. 
 
 Recognition Markings. — Though these are apparently im- 
 portant among mammals and birds, as enabling individuals of 
 the same species quickly to recognize and follow one another, 
 no special markings for this purpose are known to occur among 
 insects, not excepting the gregarious migrant species, such as 
 Anosia plcxippns and the Rocky Mountain locust. 
 
 Epigamic Colors. — Among birds, frequently, the Ijright col- 
 ors of the male are displayed during courtship, and their evo- 
 
230 ENTOMOLOGY 
 
 lution has been attributed by Darwin and many of his follow- 
 ers to sexual selection— a highly debatable subject. Among 
 insects, however, no such phenomenon has been found ; when- 
 ever the two sexes differ in coloration the difference does not 
 appear to facilitate the recognition of even one sex by the 
 other. 
 
 Evolution of Adaptive Coloration. — Natural selection is 
 the only theory of any consequence that explains the highly 
 involved phenomena of adaptive coloration. Against such 
 vague and unsupported theories as the action of food, climate, 
 laws of growth or sexual selection, natural selection alone 
 accounts for the multitudinous and intricate correlations of 
 color, pattern, form, attitude, movement, place, time, etc., that 
 are necessary to the development of a perfect case of protective 
 resemblance or mimicry. Natural selection cannot, of course, 
 originate colors or any other characters, its action being re- 
 stricted to the preservation and accumulation of such advan- 
 tageous variations as may arise, from whatever causes. As 
 Poulton says, the vast body of facts, utterly meaningless under 
 any other theory, become at once intelligible as they fall har- 
 moniously into place under the principle of natural selection, 
 to which, indeed, they yield the finest kind of support. 
 
CHAPTER VII 
 
 ORIGIN OF ADAPTATIONS AND OF SPECIES 
 
 T. .Adaptations 
 
 Organic Evolution. — Oro-anic evolution is essentially the 
 evolution of adaptive structures and functions. There remain 
 to be explained, however, non-adaptive structures and func- 
 tions, and no theory of evolution is adequate which does not 
 account for the useless as well as the useful characters. 
 
 Existing structures are due to the nature of the organism 
 and the nature of the environment ; in other words, are results 
 of the activity of protoplasm under the influence of environ- 
 mental forces. Variations arise which are useful or not and 
 either transmissible or not. Useful transmissible variations 
 not only remain but tend to become more nearly perfect ; while 
 useless variations tend to disappear. 
 
 The various theories of organic evolution difi^er chiefly in 
 their answers to these questions: (i) What is the nature of 
 variations and how do they arise? Variations are classed as 
 either continuous or discontinuous ; adaptive or unadaptive. 
 In asexual organisms, variations are brought about by the 
 direct influence of temperature, light and other primary fac- 
 tors upon protoplasm ; in sexual organisms, variations are due 
 to another cause as well, namely, the union of two kinds of 
 protoplasm. In any given case of variation, how much is due 
 immediately to protoplasm and how much to the environment ? 
 (2) What kinds of variations are transmissible? Discontinu- 
 ous variations (sports) are strongly transmissible as a rule, 
 while continuous (individual) variations are often non-trans- 
 missible; though it is often dii^cult to decide whether they are 
 transmissible or not. Each kind of variation has to be exam- 
 ined separately, on its own merits. Difficulties arise from the 
 
 237 
 
238 ENTOMOLOGY 
 
 fact that some variations which appear in successive genera- 
 tions are due not to inheritance but to the direct action of the 
 environment on each successive generation ; also to the fact 
 that some structural changes may have been brought about by 
 selection of some sort, rather than by inheritance. Are the 
 results of use or disuse or mutilation inheritable? It has not 
 been proved as yet that these " acquired characters " are 
 transmissible. On the other hand, experiments show that 
 some organisms can become acclimatized to unusual degrees 
 of heat, density, etc., through inheritance, in cases where selec- 
 tion does not enter into the problem. JMuch of the confusion 
 attending the discussion of " the inheritance of acquired char- 
 acters " has been due to disagreements as to what is meant by 
 the term "acquired characters." (3) What are the secondary 
 influences that have brought about the evolution of structures ? 
 Of these influences, natural selection and isolation are by far 
 the most important; while in some instances extensive struc- 
 tural adaptations have arisen spontaneously, without a long 
 -course of evolution. 
 
 Natural Selection. — The more intricate adaptations of 
 organism to environment, however, are for the most part inex- 
 plicable without the aid of Darwin's and Wallace's theory of 
 natural selection. After almost fifty years of searching criti- 
 cism and even violent opposition, this theory, though modified 
 in some respects, remains essentially as it was formulated, and 
 is at present the working hypothesis of most naturalists. This 
 doctrine is here outlined in its several factors. 
 
 Excessive Multiplication. — Any one species of animal or 
 plant, were its multiplication unchecked, would soon cover the 
 earth. The progeny of a single aphid in ten generations, as 
 •calculated by Huxley, would " contain more ponderable su1v 
 stance than five hundred millions of stout men ; that is, more 
 than the whole population of China." The hop aphid (Phor- 
 odon hiimuli), studied by Riley, has thirteen generations a 
 year, consisting entirely of females up to the last generation. 
 Assuming that each female produces 100 young and that the 
 
ORIGIN OF ADAPTATIONS AND OF SPECIES 239 
 
 increase is unchecked, the number of individuals of the twelfth 
 generation, as the descendants of a single female of the first 
 generation, would be ten sextillions. These if placed in a 
 single file, allowing lo aphids to an inch, would form a line so 
 long that light itself, traveling at the rate of 186,000 miles 
 per second, would require over 2,690 years to go from one 
 end of the line to the other. 
 
 As it is, many species become temporarily dominant under 
 favorable conditions; for example, the Rocky Mountain locust, 
 chinch bug and gypsy moth. Even one of the least prolific 
 species would predominate in a surprisingly short time, were 
 it permitted to increase in its normal geometrical ratio. The 
 rate of sexual reproduction is highest in fishes and insects. An 
 insect averages one or two hundred eggs, while some forms, 
 as queen termites, lay them by thousands. 
 
 Struggle for Existence. — Although a single species is 
 potentially capable of covering the earth, there actually are at 
 least 1,000,000 species of insects, not to mention 250,000 spe- 
 cies of other animals and some 500,000 kinds of plants. This 
 means a tremendous prevention of reproduction among the 
 individuals of any one species — an intense " struggle for ex- 
 istence," as Darwin termed it. Among plants and the lower 
 animals, comparatively few individuals survive and reproduce ; 
 the majority die. The agents of destruction are manifold, 
 each species having its own army of enemies, organic and in- 
 organic. Thus insects are subject to unfavorable conditions 
 of temperature and moisture, to bacterial and fungous dis- 
 eases, vertebrate and invertebrate enemies, accidents, etc. 
 The aphids are at the same time among the most prolific and 
 the most defenceless of animals. These delicate insects suc- 
 cumb to very slight mechanical shocks and are killed by ex- 
 tremes of temperature that most other insects can endure. 
 They are often washed off their food plants by rain. Their 
 rate of reproduction decreases if their food plant receives in- 
 sufficient moisture. Aphids form the chief food of coccinellid 
 larvae and beetles, are preyed upon by chrysopid and syrphid 
 
240 ENTOMOLOGY 
 
 larvje, parasitized by Braconidse and Chalcididse, carried off 
 by some of the digger-wasps (Mimesidae, Pemphredonidje), 
 and devoured by ants, carabids, other insects, spiders, and some 
 birds, as the chickadee. In damp weather, aphids are killed 
 in countless numbers by a fungous disease. In short, the 
 aphid is threatened in every direction. 
 
 Elimination of the Unfit. — In the intense " struggle for 
 existence," as it is commonly, though misleadingly, called, 
 those comparatively few individuals that survive do so mani- 
 festly by virtue of certain advantages over their less fortunate 
 fellows. One egg can stand a little more cold than another; 
 one beetle drops to the ground when disturbed and thus 
 escapes an attacking' bird, while its companions remain in place 
 and are destroyed ; some individuals escape by surpassing their 
 fellows in locomotor ability or by resembling the surface on 
 which they happen to rest. 
 
 Such fortunate individuals live to transmit their advantage- 
 ous peculiarities to their progeny, while the less favored indi- 
 viduals succumb. The progeny inherit the life-saving pecu- 
 liarities in differing degrees, and the least favored of the 
 progeny are again weeded out. Thus by the continual elim- 
 ination of individuals that vary in unfavorable directions, the 
 individuals that remain become better and better adapted to 
 the surrounding conditions of life, through the preservation 
 and accumulation of advantageous variations. This preser- 
 vation and accumulation of advantageous variations through 
 .the destruction of disadvantageous ones is the essence of nat- 
 ural selection, or the " survival of the fittest." 
 
 Favorable variations may have been so slight and infre- 
 quent as to have required geological ages for their accumula- 
 tion. On the other hand, adaptive variations are sometimes 
 so extensive from the beginning as to lead some writers to 
 doubt that these variations are preserved and improved by 
 natural selection. 
 
 Variation. — Natural selection cannot originate useful char- 
 acters, of course, but is limited to the preservation and accu- 
 
ORIGIN OF ADAPTATIONS AND OF SPECIES 24 1 
 
 mulation of such advantageous variations as already exist. 
 Variation, then, is the basis of natural selection. Though the 
 question of the origin of variations is still unsettled, the fact 
 of their occurrence in a manner sufficient for the purposes of 
 natural selection is beyond dispute. No two individuals of a 
 species are ever exactly alike in structure or jjehavior, and 
 their differences furnish the material for the operation of 
 natural selection. 
 
 Two classes of variations are distinguished on the basis of 
 the amount of variation: (i) coiitiiinous {individual) varia- 
 tions, of small extent, intergrading with one another and with 
 the typical form; and (2) discoufiiuious variations (sports), 
 or considerable and isolated departures from the normal con- 
 dition. Furthermore, variations of either class are adaptive 
 or unadaptive, the latter kind being either harmful or simply 
 neutral. 
 
 Origin of Adaptive Variations. — Xatural selection, as 
 was said, does not begin to operate until useful variations are 
 already in existence ; and the origin of these primary adaptive 
 variations is a question quije distinct from that of their sub- 
 sequent preservation and accumulation by natural selection. 
 
 That all adaptive variations are due to the response of pro- 
 toplasm to environmental influences (using the term " envi- 
 ronment " in its widest sense), it goes without saying. These 
 variations are, however, either direct or indirect. Direct 
 variations, appearing first in the soma, or body, of the organ- 
 ism, are termed somatogenic; indirect variations, apparently 
 spontaneous, and due immediately to the germ cells, are termed 
 blastogenic. Weismann places somatogenic variations, ac- 
 cording to their origin, into three categories: (i) injuries, 
 (2) functional z'ariatious, and (3) variations depending on 
 the so-called " influences of environment," these influences 
 being mainly clinuitic. These three kinds will receive brief 
 consideration. 
 
 Injuries. — There appears to be no good evidence that in- 
 juries or mutilations can be transmitted. Nearly all the ex- 
 •7 
 
242 ENTOMOLOGY 
 
 periments upon the subject have given decidedly negative 
 results. Thus Weismann found that the amputation of the 
 tails of hundreds of mice, down to the nineteenth generation, 
 had no influence on the tails of the descendants. 
 
 Mechanical injuries to the body of an organism are merely 
 casual, or accidental, effects of the environment and appear to 
 have no influence upon the germ cells. From the standpoint 
 of adaptation, injuries are only of minor importance. 
 
 Functional Variations. — While it is certain that the use 
 or disuse of organs affects their form in the individual, it 
 remains doubtful whether the effects of use and disuse are 
 transmissible. Weismann and his followers contend that they 
 are not. On the other hand, Neo-Lamarckians, as Cope, 
 Hyatt, H. F. Osborn, Packard and Eimer, have maintained 
 that they are. Weismann admits, however, that both use and 
 disuse may lead indirectly to variations, " the former when- 
 ever an increase as regards the character concerned is useful, 
 and the latter in all cases in which an organ is no longer of 
 any importance in the preservation of the species " ; and that 
 these variations may be acted upon by natural selection. 
 Thus, in a few words, the question stands. 
 
 Environmental Variations. — Under this head may be 
 classed such variations as are due directly to climate, nutrition 
 and other primary environmental influences. It is certain 
 that changes of temperature, light, and food, for example, 
 cause corresponding changes of form and function in the indi- 
 vidual organism ; though the inheritance of these changes 
 directly induced by the environment is the subject of much 
 debate. 
 
 Dallinger took flagellate infusorians that at first would die 
 at a temperature of 23° C, and by slowly raising the tempera- 
 ture through several years, brought them safely to a tempera- 
 ture of 70^ C. There was some mortality, to be sure, in his 
 experiments, but other experimenters have obtained similar 
 results without the loss of a single individual, and therefore — 
 it is important to note — without the entrance of natural selec- 
 
ORIGIN OF ADAPTATIONS AND OF SPECIES 243 
 
 tion. This prog-ressive acclimatization of successive genera- 
 tions of an organism to heat is clearly due in large measure to 
 heredity. So also in the case of the entomostracan Artemia, 
 whose specific form Schmankewitsch succeeded in changing, 
 by increasing the salinity of the water in which the animal 
 lived. Here, again, the adaptation was brought about with- 
 out the aid of selection. 
 
 Poulton's already-mentioned experiments on larvae and 
 pupcT show that these may become protectively colored as the 
 direct effect of the surrounding light on the organism. Here, 
 of course, the possible influence of natural selection can scarcely 
 be excluded, though the fact remains that the color resem- 
 blances are initiated directly by the stimulus of light upon 
 protoplasm. 
 
 Protoplasm itself is to a certain extent adaptive, in that it 
 may become acclimatized to untoward conditions of heat, light 
 and other stimuli. From this point of view, Henslow's theory 
 of self-adaptation in plants deserves more consideration than 
 it has received, though Henslow did not adopt the theory of 
 natural selection. 
 
 Blastogenic Variations. — According to Weismann, only 
 congenital variations are inheritable, i. e., only those that result 
 from modifications of the germ plasm. He holds that while 
 all variations are due ultimately to external influences, the 
 processes of reproduction (conjugation in unicellular, and 
 sexual reproduction in multicellular organisms) furnish fresh 
 combinations of individual variations for the operation of nat- 
 ural selection, and that this is the chief purpose of aniphimixis, 
 or " the mingling of two individuals or of their germs." 
 
 Inheritance of Acquired Characters. — Weismann and his 
 followers, in opposition to the Neo-Lamarckians, hold that 
 somatogenic, or acquired, characters are not transmissible ; 
 that every permanent (hereditary) variation proceeds from 
 the germ. 
 
 The subject of the inheritance of acquired characters has 
 aroused no end of discussion, much of which has been fruit- 
 
244 ENTOMOLOGY 
 
 less, chiefly for two reasons. First, there is no httle disagree- 
 ment as to what is meant by the term " acquired characters." 
 An acquired character arises, not in the germ cells, but in the 
 soma, or body, and for the theoretical transmission of the 
 character the soma must affect the germ cells subsequently ; 
 though some maintain that a given external influence may 
 affect both soma and germ plasm at the same time. The defi- 
 nition of acquired characters excludes (i) sports; (2) changes 
 due to the renewed action of the environment upon successive 
 generations of an organism; (3) changes which may have 
 been due to selection. Second, having defined the term, it is 
 often difficult if not impossible to say whether a given charac- 
 ter is acquired or not. Thus in an acclimatization experiment, 
 if heat, for example, affects first the soma and the latter affects 
 the germ cells subsequently, we have an example of the inheri- 
 tance of an acquired character. If, however, the heat affects 
 soma and germ plasm simultaneously, the result is or is not 
 the inheritance of an acquired character, according as one de- 
 fines the term. Indeed, Weismann himself has found the 
 greatest difficulty in trying to explain the inheritance of " cli- 
 matic" variations in terms of his well-known hypothesis. In 
 fact, the distinction between acquired and non-acquired charac- 
 ters is to no little extent artificial and arbitrary ; and too strong 
 an insistence upon the distinction bars the way to the solution 
 of the more important question — What kinds of variations are 
 inheritable and what are not ? 
 
 To summarize : Of somatogenic, or acquired, characters, 
 ( I ) injuries or mutilations are unadaptive and probably unin- 
 heritable. (2) Functional variations are adaptive, but the 
 subject of their transmissibility is involved in doubt. As yet 
 there is no adequate experimental evidence upon the subject, 
 the discussion of which, therefore, is based chiefly on theoret- 
 ical grounds. There is a strong tendency, however, to believe 
 that results of use or disuse are to some extent transmissible 
 to the benefit of succeeding generations, and even Weismann. 
 the chief opponent of the Neo-Lamarckians. admits that the 
 
ORIGIN OF ADAPTATIONS AND OF SPECIES 245 
 
 effects of use and disuse are important in organic evolution. 
 (3) Effects of climatal inlluences and of nutrition arc fre- 
 quently adaptive and often transmissible, as experiments have 
 proved. There is, however, much difference of opinion as to 
 the precise way in which these effects are transmitted. 
 
 Incidental Adaptations. — Many leaf-eating caterpillars 
 and grasshoppers are green from the presence of chlorophyll 
 in their l)odies; they owe their color directly to their food. 
 Now it may be admitted that this green color is often protec- 
 tive, without admitting that the color was acquired for that 
 purpose. In the case of green leaf-mining caterpillars, cer- 
 tainly, the color appears to be superfluous for protective pur- 
 poses. Even variegated protective coloration may be simply 
 a direct effect of the surrounding kinds of light, as Poulton 
 proved. 
 
 Again, take the various tropisnis, described in another 
 chapter. Often they are adaptive and often they are not ; but 
 they occur inevitably, whether they result advantageously or 
 not. It is too much to say that a useful structure or function 
 appeared because of its usefulness. It first appeared, and then 
 proved to be either useful or not useful. If useful, a structure 
 may save the life of its possessor and possibly be transmitted to 
 the next generation ; if harmful, it is self-eliminating. 
 
 2. Species 
 
 Modifications arise, and are either useful or not to their 
 possessors. For the systematist who aims merely to distin- 
 guish one species from another, this distinction matters but 
 little. To the biologist, however, the difference is an essential 
 one, and he draws a line between specific peculiarities that are 
 adaptive and those that are not adaptive. The origin of 
 species and the origin of adaptations are by no means the 
 same thing. 
 
 Darwin's Origin of Species. — At the time Darwin's great 
 W'Ork was written, its immediate purpose was to demonstrate 
 a process of organic evolution; and this object was accom- 
 
246 ENTOMOLOGY 
 
 plished in the most forcible way, namely, by shattering the 
 traditional belief in the immutability of species. Nowhere 
 does Darwin imply that nature is striving to produce " spe- 
 cies " for their own sake. A process of evolution was the 
 theme of Darwin and its key-note was adaptation. 
 
 Indeed, for the purposes of the present generation, Dar- 
 win's immortal work would more properly be entitled — The 
 Evolution of Adaptations by Means of Natural Selection. 
 And to us, who now ridicule the old notion of the special 
 creation of species, the doctrine of natural selection appears in 
 a fresh light, with a new mission. For, in the words of 
 Romanes, the theory is " primarily, a theory of adaptations, 
 and only becomes secondarily a theory of species in those com- 
 paratively insignificant cases where the adaptations happen to 
 be distinctive of the lowest order of taxonomic division." 
 The opposite view he compares " to that of an astronomer who 
 should define the nebular hypothesis as a theory of the origin 
 of Saturn's rings. It is indeed a theory of the origin of 
 Saturn's rings ; but only because it is a theory of the origin of 
 the entire solar system, of which Saturn's rings form a part. 
 Similarly, the theory of natural selection is a theory of the 
 entire system of organic nature in respect of adaptations, 
 whether these happen to be distinctive of particular species 
 only, or are common to any number of species." It should be 
 remembered, of course, in using this comparison, that not all 
 specific characters are adaptive. 
 
 As regards the origin of species, however, there are several 
 processes at work besides natural selection. Indeed, Darwin 
 himself knew this, for he expressly stated : " I am convinced 
 that natural selection has been the most important, but not the 
 exclusive, means of modification." 
 
 The Conception of "Species." — What is a "species"? 
 The only practical criterion of species is isolation, or separate- 
 ness, of one kind or another. The majority of our " species " 
 are sharply separated from one another by structural differ- 
 ences ; the minority, however, blend into one another, and 
 
ORIGIN OF ADAPTATIONS AND OF SPECIES 247 
 
 have so many characters in common that the separation into 
 species hecomes an arbitrary matter, depenchng upon the g-ood 
 judgment of the systematist, who if wise, is neither a 
 "' Uimper " nor a " sphtter." At present, the minutely dis- 
 criminating" powers of an unfortunately large number of ento- 
 mological systematists are displayed in an extraordinary mul- 
 tiplication of generic and specific names, often to the sacrifice 
 of convenience and stability of nomenclature. This has been 
 carried to such an extent, however, that a reaction has already 
 set in; and there is now some promise of a rational termi- 
 nology. 
 
 Considering characters as of specific importance only, it 
 makes no immediate difference whether they are adaptive or 
 not. If adaptive, whatever their origin, they may have been 
 developed by natural selection; if not, they are incidental, and 
 may be due to such influences as those next to be referred to. 
 
 Climate and Food. — Naturalists have recorded many in- 
 stances in which plants or animals when transferred to a new 
 climate have produced ofTspring' markedly different from the 
 parent form. The term climate, however, has no precise 
 meaning for the naturalist, referring as it does collectively to 
 several distinct influences, chief among which are tempera- 
 ture, moisture, light and (indirectly) food conditions. Ex- 
 perimental evidence has already been adduced to show^ that 
 color changes in insects may be brought about as direct effects 
 of warmth, cold, light or food. Some of these color varia- 
 tions are possibly inheritable, and many of them, artificially 
 produced, would be regarded as distinctive of new species, if 
 found in a state of nature. In fact, the distinction between 
 varieties and species is often entirely arbitrary ; varieties are 
 incipient species and it is often impossible to draw any sharp 
 line between the two. 
 
 Mutation Theory. — De Vries' imitation theory, expounded 
 in 1 90 1 as the result of nearly twenty years of experimenta- 
 tion, is at present an absorbing subject of study and discussion 
 in the biological world, and will continue to be for many years, 
 until the full bearing of the theory is ascertained. 
 
248 ENTOMOLOGY 
 
 De Vries has produced new species by experimental means 
 and without the aid of selection. Moreover, he has produced 
 them at once, showing that a species does not necessarily re- 
 quire hundreds of years to develop, by means of a long-con- 
 tinued process of selection. 
 
 It has long been customary to draw a distinction between 
 individual variations and sports. Darwin recognized the dis- 
 tinction and was one of the first to notice the extraordinary 
 persistence with which sports are transmitted, as compared 
 with the relative instability of individual variations. Not a 
 few dominant races of plants and animals are known to have 
 arisen from sports, and the belief has been gaining ground 
 with Bateson and others that species also have to some extent 
 arisen from sports, rather than from individual variations; 
 though the rarity of sports as compared with individual varia- 
 tions is the strongest objection to this theorv as a theory of 
 the origin of species in general. 
 
 De Vries, however, was the first to make extensive experi- 
 ments on sports, or imitations, as he calls them, and to formu- 
 late a definite theory of the subject from a considerable body 
 of evidence. He regards the qualities of organisms as being 
 built up of definite but sharply separated units, or elements, 
 which combine in groups. The addition of a new unit means 
 a mutation, a sudden departure from the normal specific form ; 
 in other words, a new species may arise from the parent form 
 without any evident gradation. The mutable condition exists 
 only at times, and some species are more mutable than others. 
 Acting upon this as a hypothesis, De Vries made a preliminary 
 study of a great number of plants in order to find one in its 
 period of mutation, and at length selected CEnothera Lamarck- 
 iana (probably a variety of our E. biennis, introduced into 
 Holland from America), because of its exceptionally vigorous 
 multiplication, dispersion and variation. By careful cultivation 
 and by means of artificial pollination, he succeeded in obtaining 
 seven or more new species. Most of these remained con- 
 stant from year to year in spite of intercrossing. ]\Ioreover, 
 
ORIGIN OF ADAPTATIONS AND OF SPECIES 249 
 
 cross pollination was not necessary to the prodnction of new 
 species by mutation, and when employed did not accelerate the 
 results materially. As a botanist, De Vries confined his inves- 
 tigations to plants, but his g-eneral conclusions are perhaps 
 equally applicable to animals, and his experiments are doulit- 
 less being- repeated by zoologists. 
 
 Through his exhaustive experiments, De Vries has partly 
 attained a long-desired object, in that he has removed the ques- 
 tion of the origin of some species " from the purely theoretical 
 to the concrete." 
 
 The mutation theory is not primarily a theory of the origin 
 of adaptive characters. It endeavors to account for the origin 
 of certain characters, which may or may not prove useful to 
 their possessors. Indeed, one great merit of De Vries' theory 
 is that it affords an explanation for the existence of variations 
 which are not useful. Now Darwdn does not pretend to 
 account for the origin of variations, but he shows how given 
 variations, if useful, may be preserved and accumulated. 
 Thus the theory of De Vries supplements that of Darwin and 
 does not antagonize it; even though De Vries himself takes 
 much pains to contrast the two theories, and even asserts that 
 new species arise exclusively as mutations. Both theories, 
 indeed, are theories of the origin of species ; but according to 
 De Vries, specific characters spring into existence, irrespective of 
 their usefulness; while according to Darwin, useful characters, 
 and these only, are premised, as the starting point of the evolu- 
 tion of certain kinds of species. Thus, as another has said, 
 natural selection begins where the mutation theory leaves off. 
 
 Isolation. — The theory of isolation as given by Gulick and 
 by Romanes is highly important as affording an explanation 
 of " the rise and continuance of specific characters which need 
 not necessarily be adaptive characters." By isolation is meant 
 " simply the prevention of intercrossing between a separated 
 section of a species or kind and the rest of that species or 
 kind. ... So long as there is free intercrossing, heredity 
 cancels variability, and makes in favor of fixity of type. Only 
 
250 ENTOMOLOGY 
 
 when assisted by some form of discriminate isolation, which 
 determines the exchisive breeding of hke with hke, can hered- 
 ity make in favour of change of type, or lead to what we un- 
 derstand by organic evolution." (Romanes.) 
 
 " As soon as a portion of a species is separated from the 
 rest of that species, so that breeding between the two portions 
 is no longer possible, the general average of characters in the 
 separated portion not being in all respects precisely the same 
 as it is in the other portion, the result of in-breeding among 
 all individuals of the separated portion will eventually be dif- 
 ferent from that which obtains in the other portion ; so that, 
 after a number of generations, the separated portion may 
 become a distinct species from the effect of isolation alone. 
 Even without the aid of isolation, any original difference of 
 average characters may become, as it were, magnified in suc- 
 cessive generations, provided that the divergence is not harm- 
 ful to the individuals presenting it, and that it occurs in a 
 sufficient proportional number of individuals not to be imme- 
 diately swamped by intercrossing." (Romanes.) 
 
 Of the many modes of isolation, the most important are the 
 geographical and the physiological, both of which have re- 
 ceived elaborate treatment by Romanes. 
 
 The doctrine of geographical isolation offers a partial ex- 
 planation of the origin of the peculiar faun?e and florae of 
 remote islands. These island species, however peculiar, 
 doubtless came originally from the mainlands where their 
 nearest allies now occur; thus the endemic insects of the Gala- 
 pagos Islands are most nearly related to species of western 
 South America. 
 
 The first individuals of Schisfoccrca doubtless reached the 
 Galapagos Islands by means of the wind or on driftwood. 
 These individuals, separated from the main body of their spe- 
 cies, would interbreed and might thereby give rise to a new 
 variety or species, if we may assume that the average of charac- 
 ters of the detached portion of the species differed from that 
 of the main bodv of individuals ; in other words, that the iso- 
 
ORIGIN OF ADAPTATIONS AND OF SPECIES 251 
 
 lated forms varied aroniul a mean condition of their own, and 
 no longer around the mean of the species as a whole. 
 
 Besides this, the influences of new food and new climatal con- 
 ditions as means of modification must be taken into account. 
 Furthermore, though a new species might conceivalily arise on 
 an island without the aid of natural selection, it is very likely 
 that selection has often played a part in the formation of such 
 a species, as in the apterous or subapterous forms that pre- 
 dominate on oceanic islands. While it is possible that the 
 earliest arrivals were already apterous, and arrived safely be- 
 cause on that account they clung to driftwood instead of flying 
 away, it is probable, on the other hand, that on wind-swept 
 islands the full-winged and more \'enturesome individuals 
 would be carried out to sea and drowned, leaving the poorly 
 winged and less venturesome ones to remain and transmit 
 their owni life-saving peculiarities ; wdiich would become inten- 
 sified by continual selection of the same kind. Romanes, in- 
 deed, regards natural selection itself as but one form of iso- 
 lation. 
 
 Physiological isolation, which though important will not be 
 discussed here, " arises in consequence of mutual infertility 
 between the members of any group of organisms and those of 
 all other similarly isolated groups occupying simultaneously 
 the same area." (Romanes.) 
 
CHAPTER VIII 
 
 INSECTS IN RELATION TO PLANTS 
 
 Insects, in common with other animals, depend for food 
 primarily upon the plant world. No other animals, however, 
 sustain such intimate and complex relatiijns to plants as in- 
 sects do. The more luxuriant and varied the flora, the more 
 abundant and diversified is its accompanying insect fauna. 
 
 Not only have insects become profoundly modified for using 
 all kinds and all parts of plants for food and shelter, but plants 
 themselves have been modified to no small extent in relation to 
 insects, as appears in their protective devices against unwelcome 
 insects, in the curious formations known as '* galls," the various 
 insectivorous plants, and especially the omnipresent and often 
 intricate floral adaptations for cross-pollination through the 
 agency of insect visitors. Though insects have laid plants un- 
 der contribution, the latter have not only vigorously sustained 
 the attack but have even pressed the enemy into their own ser- 
 vice, as it were. 
 
 Numerical Relations. — The number of insect species sup- 
 ported by one kind of plant is seldom small and often surpris- 
 ingly large. The poison ivy (Rhus toxicodendron) is almost 
 exempt from attack, though even this plant is eaten by a leaf- 
 mining caterpillar, two pyralid larvae and the larva of a scolytid 
 beetle ( Schwarz, Dyar ) . Horse-chestnut and buckeye have per- 
 haps a dozen species at most ; elm has eighty ; birches have over 
 one hundred, and so have maples; pines are known to harbor 
 170 species and may yield as many more; while our oaks sus- 
 tain certainly 500 species of insects and probably twice as many. 
 Turning to cultivated plants, the clover is affected, directly or 
 indirectly, by about 200 species, including predaceous insects, 
 parasites, and flower-visitors. Clover grows so vig'orously that 
 
 252 
 
INSECTS IN RELATION TO PLANTS 253 
 
 it is able to withstand a great deal of injury from insects. Corn 
 is attacked by about 200 species, of which 50 do notable injury 
 and some 20 are pests. Aj^ple insects number some 400 species. 
 
 Not uncommonly, an insect is restricted to a single species of 
 plant. Thus the caterpillar of H codes hypopliUcas feeds only 
 on sorrel {Rmnex acctoscUa) , so far as is known. The chry- 
 somelid Chrysochus aurafiis appears to l)e limited to Indian 
 hemp {Apocymiin androsccmifoliuiii) and to milkweed (As- 
 clcpias). In many instances, an insect feeds indifferently 
 upon several species of plants provided these have certain 
 attributes in common. Thus Argynnis cyhclc, aphrodite and 
 atlantis eat the leaves of various species of violets, and the 
 Colorado potato beetle eats different species of Solarium. 
 Papilio thoas feeds upon orange, prickly ash and other Ruta- 
 cese. Anosia plexippus eats the various species of Asclepias 
 and also Apocynuin aiidrosccinifoliiuii ; while ChrysocJiiis 
 also is limited to these two genera of plants, as was said. 
 These plants agree in having a milky juice ; in fact the two 
 genera are rather nearly related botanically. The common cab- 
 bage butterfly (Pier is rapcc) though confined for the most part 
 to Cruciferae, such as cabbage, mustard, turnip, radish, horse- 
 radish, etc., often develops upon Tropccoluui, which belongs to 
 Geraniace?e ; all its food plants, however, ha\-e a pungent odor, 
 which is probably the stimulus to oviposition. 
 
 ?^Iost phytophagous insects, however, range over many food- 
 plants. The cecropia caterpillar has more than sixty of these, 
 representing thirty-one genera and eighteen orders of plants ; 
 and the tarnished plant bug (Lygits prafciisis) feeds indiffer- 
 ently on all sorts of herbage, as does also the caterpillar of 
 Diacrisia virgiriica. Alany of the insects of apple, pear, 
 quince, plum, peach, and other plants of the family Rosaceas 
 occur also on wild plants of the same family ; and the worst of 
 our corn and wheat insects have come from wild grasses. As 
 regards number of food plants, the gypsy moth " holds the 
 record," for its caterpillar will eat almost any plant. In Mass- 
 achusetts, according to Forbush and Fernald, it fed in the field 
 
254 
 
 ENTOMOLOGY 
 
 upon 78 Species of plants, in captivity upon 458 species (30 
 under stress of hunger, the rest freely), and refused only 19 
 species, most of which (such as larkspur and red pepper) 
 had poisonous or pungent juices, or were otherwise unsuit- 
 
 ^ able as food. The migratorv 
 
 FiG. 247. . . . ' 
 
 locust is notoriously omniv- 
 orous, and perhaps eats even 
 more kinds of plants than the 
 gypsy moth. 
 
 Galls. — Alost of the conspic- 
 uous plant outgrowths known 
 as " galls " are made by in- 
 sects, though many of the 
 smaller plant galls are made 
 by mites (Acarina) and a few 
 plant excrescences are due to 
 nematode worms and to fungi. 
 Among insects, Cynipidse ( Hy- 
 menoptera) are pre-eminent 
 as gall-makers and next to 
 these, Cecidomyiidje (Diptera), 
 Aphidid^e and Psyllidas (Hemiptera) ; a few gall-insects occur 
 Fig. 248. 
 
 Holciispis globulus. A, galls on oak, 
 natural size; B, the gall-maker, twice 
 natural length. 
 
 of Ho leas pis d\t 
 
 on oak. Natural size. 
 
 among Tenthredinid?e (Hymenoptera) and Trypetid?e (Dip- 
 tera), and one or two among Coleoptera and Lepidoptera. 
 Cynipidje affect the oaks (Figs. 247, 248) far more often 
 
INSECTS IN RELATION TO PLANTS 
 
 255 
 
 Fig. 249. 
 
 than any other plants, though not a few species select the wild 
 rose. Cecidomyiid galls occur on a great variety of plants, and 
 those of aphids on elm (Fig. 249), poplar, and many other 
 plants; while psyllid galls are most frequent on hackberry. 
 The galls may occur anywhere on a plant, from the roots to the 
 flowers or seeds, though each gall-maker always works on the 
 same part of its plant, — root, stem, 
 bud, leaf, leaf-vein, flower, seed, etc. 
 
 Galls present innumerable forms, 
 but the form and situation of a 
 gall are usually characteristic, so 
 that it is often possible to classify 
 galls as species even before the 
 gall-maker is known. 
 
 Gall-Making. — The female cy- 
 nipid punctures the plant and lays 
 an egg in the wound ; the egg- 
 hatches and the surrounding plant 
 tissue is stimulated to grow rapidly 
 and abnormally into a gall, which 
 serves as food for the larva ; this 
 transforms within the gall and es- 
 capes as a winged insect. The 
 physiology of gall-formation is far 
 from being understood. It has been 
 found that the mechanical irritation from the ovipositor is not 
 the initial stimulus to the development of a gall ; neither is 
 the fluid which is injected by the female during oviposition,this 
 fluid being probably a lubricant ; if the egg is removed, the gall 
 does not appear. Ordinarily the gall does not begin to grow 
 until the egg has hatched, and then the gall grows along with 
 the larva; exceptions to this are found in some Hymenoptera 
 in which the egg itself increases in volume, when the gall may 
 grow with the egg. It appears that the larva exudes some 
 fluid which acts upon the protoplasm of certain plant cells (the 
 cambium and other cells capable of further growth and multi- 
 plication) in such a way as to stimulate their increase in size 
 
 i 
 
 M^^Km^^ 
 
 i 
 
 JB 
 
 i 
 
 1 
 
 i,.sy'^£ 
 
 f 
 
 
 ^ 
 
 ^ 
 
 Cockscomb gall of Colopha ulml 
 on elm. Slightly reduced. 
 
256 ENTOMOLOGY 
 
 and number. \\'hy the gall should have a distinctive, or spe- 
 cific, form, it is not yet known. There is no evidence that the 
 form is of any adaptive importance, and the subject probably 
 admits of a purely mechanical explanation — a problem for the 
 future. 
 
 Gall Insects. — The study of gall insects is in manv respects 
 difficult. It is not at all certain that an insect which emerges 
 from a gall is the species that made it ; for many species, even 
 of Cynipidse, make no galls themselves but lay their eggs in 
 galls made by other species. Such guest-insects are termed 
 inquiUnes. Furthermore, both gall-makers and inquilines are 
 attacked by parasitic Hymenoptera, making the interrelations 
 of these insects hard to determine. Many species of insects 
 feed upon the substance of galls; thus Sharp speaks of as 
 many as thirty different kinds of insects, belonging to nearly 
 all the orders, as having been reared from a single species of 
 gall. 
 
 Parthenogenesis and Alternation of Generations. — Par- 
 tlicnogcncsis has long been known to occur among Cynipidae. 
 It has repeatedly been found that of thousands of insects 
 emerging from galls of the same kind, all were females. In 
 one such instance the females were induced by Adler to lay eggs 
 on potted oaks, when it was found that the resulting galls were 
 quite unlike the original ones, and produced both sexes of an 
 insect which had up to that time been regarded as another 
 species. Besides parthenogenesis and this alternation of gene- 
 rations, many other complications occur, making the study of 
 gall-insects an intricate and highly interesting subject. 
 
 Plant-Enemies of Insects. — ]\Iost of the flowering plants 
 are comparatively helpless against the attacks of insects, though 
 there are many devices which prevent "unwelcome " insects 
 from entering flowers, for instance the sticky calyx of the catch- 
 fly (Silene z'irginica) , which entangles ants and small flies. A 
 few plants, however, actually feed upon insects themselves. 
 Thus the species of Drosera, as described in Darwin's classic 
 volume on insectivorous plants, have specialized leaves for the 
 
INSECTS IN RELATION TO PLANTS 
 
 257 
 
 purpose of catching insects. The stout hairs of these leaves 
 end each in a g-lolmlar kiiol). which secretes a sticky fluid. 
 When a tly ahglits on one of these leaves the hairs hend over 
 and hold the insect: then a fluid analogotis to the gastric juice 
 of the human stomach exudes, digests the 
 alhuminoid suhstances of the insect and ''^'■- --''"■ 
 
 tliese are ahsorhed into the tissues of the 
 leaf; after which the tentacles unfold 
 and are ready for the next insect \-isitor. 
 The Venus's flytrap is another well- 
 known example ; the trap. f(jrmed from 
 the terminal portion of a leaf, consists of 
 two valves, each of which hears three 
 trigger-like hristles. and when these are 
 touched l)v an insect the \'ah'es snap to- 
 gether and fretjuently imprison the insecc. 
 which is eventually digested, as hefore. 
 In the common pitcher-plants, the pitcher, 
 fashioned from a leaf, is lined with d(jwn- 
 ward pointing bristles, which allow an 
 insect to enter but pre\ent its escape. 
 The bottom of the pitcher contains water, 
 in which ma}- Ije found the remains 
 of a great variety of insects which 
 ha\'e drowned. There are e\en nectar 
 glands and conspicuous colors, presum- 
 ably to attract insects into these traps, 
 where their dec(jmp(jsition products are 
 more or less useful to the plant. In 
 
 Fructifying sprouts of 
 a fungus, Conlyccps rav^:!- 
 ncHi, arising from the 
 Ijody of a white grub, 
 Lachnosterna. Slightly 
 reduced. — After Riley. 
 
 over and envelops insects that have 
 
 been caught by the glandular hairs of the upper surface 
 of the leaf, a copious secretion digests the softer portions of 
 the insects, and the dissolved nitrogenous matter is absorbed 
 into the plant. Utricularia has little bladders which entrap 
 small aquatic insects. These plants are only partially depend- 
 18 
 
258 
 
 ENTOMOLOGY 
 
 ent on insect-food, however, for they all possess chlorophyll. 
 
 Bacteria cause epidemic diseases among- insects, as in the 
 flacherie of the silkworm ; and fungi of a few groups are spe- 
 cially adapted to develop in the bodies of living insects. 
 
 Those who rear insects know how frequently caterpillars and 
 other larvcT are destroyed by fungi that g*ive the insects 
 a powdered appearance. These fungi, referred to the genus 
 Isario, are in some cases known to be asexual stages of forms 
 of Cordyccps, which forms appear from the bodies of various 
 larvae, pupae and imagines as long, conspicuous, fructifying 
 sprouts (Fig. 250). 
 
 The chief fungus parasites of insects belong to the large 
 family Entomophthoraceae, represented by the common Empusa 
 imtsccc (Fig. 251) which affects various flies. In autumn, 
 
 Fig. 251. 
 
 
 Empusa musca, the common fly-fungus. A, house fly {Mttsca domestica), sur- 
 rounded by fungus spores (conidia) ; B, group of conidiophores showing conidia in 
 several stages of development; C, basidium (6) bearing conidium (c) before discharge. 
 B and C after Th.^xter. 
 
 especially in warm moist weather, the common house fly may 
 often be seen in a dead or dying condition, sticking to a win- 
 dow-pane, its abdomen distended and presenting alternate black 
 and white bands, while around the fly at a little distance is a 
 
INSECTS IN RELATION TO PLANTS 259 
 
 wliite powdery rinj;', nv halo. 'Hie white intersegmental bands 
 are made bv threads of tlie fnni^iis just name(b and the white 
 halo by countless asexual spores known as coiiiilia, which have 
 been forcibly discharged from the swollen threads that bore 
 them ( h'ig. -'51 ) by pressure, resulting probably from the ab- 
 sorption of moisture. These spores, ejected in all directions, 
 may infect another fly upon contact and produce a grow'th of 
 fungus threads, or liyl^luc, in its body. The fungus may be 
 ])r(~»pagated also by means of resting spores, as found by Thax- 
 ter. t)ur authority upon the fungi of insects. 
 
 Eiiipiisa aphidis is very common on plant lice and is an im- 
 portant check upon their multiplication. Aphids killed by this 
 fungus are found clinging to their food plant, with the body 
 swollen and discolored. Einpusa grylli attacks crickets, grass- 
 hoppers, caterpillars and other forms. Curiously enough, 
 grasshoppers affected by this fungus almost always crawl to 
 the top of some plant and die in this conspicuous position. 
 
 Sporotrichuni, a genus of hyphomycetous fungi, affects a 
 great variety of insects, spreading within the body of the host 
 and at length emerging to form on the body of the insect a 
 dense white felt-like covering, this consisting chiefly of myriads 
 of spores, by means of which healthy insects may become in- 
 fected. Under favorable conditions, especially in moist sea- 
 sons, contagious fungus diseases constitute one of the most 
 important checks upon the increase of insects and are therefore 
 of vast economic importance. Thus the termination (in 
 1889) of a disastrous outlireak of the chinch bug' in Illinois 
 and neighboring states " was apparently due chiefly, if not 
 altogether, to parasitism by fungi." Artificial cultures of the 
 common Sporofrichnm globiilifcnim have been used exten- 
 sively as a means of spreading infection among chinch bugs 
 and grasshoppers, with, however, Imt moderate success as yet. 
 
 Insects in Relation to Flowers. — Among the most marve- 
 lous phenomena known to the biologist are the innumerable 
 and complex adaptations by means of which flowers secure 
 cross pollination through the agency of insect visitors. 
 
26o 
 
 ENTOMOLOGY 
 
 Cross fertilization is actually a necessity for the continued 
 vigor and fertility of flowering plants, and while some of them 
 are adapted for cross pollination by wind or water, the major- 
 ity of flowering- plants exhil)it profound modifications of floral 
 structure for compelling insects ( and a few other animals, as 
 birds or snails) to carry pollen from one flower to another. In 
 general, the conspicuous colors of flowers are for the purpose 
 
 Fig. 252. 
 
 Bumble bee (Boiiibus) entering flower of blue-fiag il ris -versicolor). 
 reduced. 
 
 of attracting insects, as are also the odors of flowers. Night- 
 blooming flowers are often white or yellow and as a rule 
 strongly scented. Colors and odors, however, are simply 
 indications to insects that edible nectar or pollen is at hand. 
 Such is the usual statement, and it is indeed probable that 
 
INSECTS IN RELATION TO PLANTS 
 
 261 
 
 Fig. 253. 
 
 insects actually do associate color and nectar, even though 
 thev will tl}' to bits of colored paper almost as readilv as they 
 will to tlowers of the same colors. Jt is not to be supposed, 
 however, that insects realize that they confer any benefit 
 ujion the plant in the flowers of which they find food. At 
 an\' rate, most flowers are so 
 constructed that certain insects 
 cannot get the nectar or pollen 
 without carrying some pollen 
 away, and cannot enter the next 
 flower of the same kind without 
 leaving some of this pollen upon 
 the stigma of that flower. Take 
 the iris, for example, which is 
 admirably adapted for pollina- 
 tion by a few bees and flies. 
 
 Iris. — In the common blue-flag (Iris versicolor, 
 Fig. 252), each of the three drooping sepals forms 
 the floor of an arched passageway leading to the nec- 
 tar. Over the entrance and pointing outward is a 
 movable lip (Fig. 253, /), the outer surface of which 
 is stigmatic. An entering bee hits and bends down 
 the free edge of this lip, wdiich scrapes pollen from 
 the back of the insect and then springs Ijack into 
 
 place. Within the passage, the section to illustrate cross pollination 
 
 hairy back of the bee rubs against °' -'"'■ ""' ^"''^^;"= ^' ^'*^™^'^'^ '''' 
 
 J "-' n, nectary; s, sepal. 
 
 an overhanging anther (a/;) and 
 
 becomes powdered with grains of pollen as the insect pushes 
 down towards the nectar. As the bee backs out of the pass- 
 age it encounters the guardian lip again, but as this side of 
 the lip can not receive pollen, immediate close pollination is 
 prevented. Of course, it is possible for bees to enter another 
 part of the same flower or another flower of the same plant, 
 l)ut as a matter of fact, they habitually fly away to another 
 plant ; moreover, as Darwin found, foreign pollen is prepotent 
 over pollen from the same flower. It may be added that bees 
 
262 
 
 ENTOMOLOGY 
 
 and other poUenizing insects ordinarily visit in succession sev- 
 eral flowers of the same kind. 
 
 Orchids. — The orchids, with their fantastic forms, are really 
 elaborate traps to insure cross pollination. In some orchids 
 {Hahcnaria and others) the nectar, lying- at the bottom of a 
 long tube, is accessible only to the long-tongued Sphingid?e. 
 While probing for the nectar, a sphinx moth brings each eye 
 against a sticky disk to which a pollen mass is attached, and 
 flies away carrying the mass on its eye. Then these poUinia 
 bend down on their stalks in such a way that when the moth 
 thrusts its head into the next flower they are in the proper 
 position to encounter and adhere to the stigina. The orchid 
 Angrcrcuiu scsquipcdalc, of Madagascar, has a nectary tube 
 more than eleven inches long, from which Darwin inferred the 
 existence of a sphinx moth with a tongue equally long, — an 
 inference which proved to be correct. 
 
 Milkweed. — The various milkweeds are fascinating subjects 
 to the student of the interrelations of flowers and insects. The 
 flowers, like those of orchids, are remarkablv formed with 
 
 Fig. 254. 
 
 ^^ 
 
 Structure of milkweed flower (Asclcpuis incaniata) with reference to cross pollina- 
 tion. A, a single flower; c, corolla; li, hood; B. external aspect of fissure (/) leading 
 up to disk and also into stigmatic chamber; /;, hood; C, pollinia; d, disk. Enlarged. 
 
INSECTS IN RELATION TO PLANTS 
 
 ^63 
 
 reference to cross pollination by insects. As a honc}- bee or 
 other insect crawls o\-er the Howers (hii^'. 254, A) to get the 
 nectar, its le.^'s slip in between the pecnliar nectariferons Iioods 
 sitnated in front of each (?/;///('/'. As a let;" is drawn npwarcl one 
 of its claws, hairs, or spines frecinently catches in a \'-shaped 
 fissnre (/, Fig". 254, B) and is guided along a slit to a notched 
 disk, or corpuscle ( iMg. 254, C, </ ) . This disk clings to the 
 leg of the insect, which carries off by means of the disk a pair 
 of pollen masses of poUinia (Fig. 254, C). When first re- 
 moved from their enclosing pockets, or anthers, these thin 
 spatulate pollinia lie each pair in the same plane, but in a few 
 minutes the two pollinia twist on their stalks and come face to 
 face in such a way that one of them can be easily introduced 
 into the sfigiiiatic chamber of 
 a new flower \'i sited bv the in- 
 
 FiG. 2s=;. 
 
 A wasp, Splicx ichncuDioiica, 
 linia of milkweed attached to 
 Slightly enlarged. 
 
 ith pel- 
 ts legs. 
 
 the insect ordinarily break the 
 
 stem, or rcfinaciilitiii, of the 
 
 pollinium and free the insect. 
 
 Often, however, the insect loses 
 
 a leg or else is permanently 
 
 entrapped, particularly in the 
 
 case of such large-flowered 
 
 milkweeds as Asclcpias coriiiiti, 
 
 wdiich often captures bees, flies 
 
 and moths of considerable size. 
 
 Pollination is accomplished by 
 
 a great variety of insects, chiefly Hymenoptera, Diptera, Lepi- 
 
 doptera and Coleoptera. These insects when collected about 
 
 milkweed flow^ers usually display the pollinia dangling from 
 
 their legs, as in Fig. 255. 
 
 The details of pollination may lie g'athered bv a close ob- 
 ser^'er from observations in the field and may be demonstrated 
 to perfection by using a detached leg of an insect and dragging 
 it upward between two of the hoods of a flower ; first to re- 
 move the pair of pollinia and then again to introduce one of 
 them into an empty stigmatic chamber. 
 
264 
 
 ENTOMOLOGY 
 
 Yucca. — An extraordinary example of the interdependence 
 of plants and insects was made known by Riley, whose 
 detailed account is here summarized. The yuccas of the 
 southern United States and ^Mexico are among the few plants 
 that depend for pollination each upon a single species of insect. 
 The pollen of Yucca iilamciifosa cannot be introduced into the 
 stigmatic tube of the flower without the help of a little white 
 tineid moth, Pronuba ynccasclla, the female of which pollen- 
 izes the flower and lays eggs among the ovules, that her larvae 
 
 Fig. 256. 
 
 may feed upon the 
 young seeds. \Miile 
 the male has no un- 
 usual structural pecu- 
 liarities, the female is 
 adapted for her special 
 work by modifications 
 which are u n i q u e 
 a m o n g Lepidoptera, 
 namely, a pair of pre- 
 hensile and spinous 
 maxillary " tentacles " 
 (Fig. 256, A) and a 
 long protrusible ovi- 
 positor (B) which 
 combines in itself the 
 functions of a lance 
 and a saw. 
 
 The female begins to work soon after dark, and will con- 
 tinue her operations even in the light of a lantern. Clinging 
 to a stamen (Fig. 257) she scrapes off pollen with her palpi 
 and shapes it into a pellet by using the front legs. After 
 gathering pollen from several flowers she flies to another 
 flower, as a rule, thrusts her long flexible ovipositor into the 
 ovary (Fig. 258) and lays a slender egg alongside seven or 
 eight of the ovules. 
 
 Pronuba yuccasella.' A, maxillary tentacle 
 and palpus; B, ovipositor. — After Riley. Fig- 
 ures 256-258 are republished from the Third 
 Report of the Missouri Botanical Garden, by 
 permission. 
 
INSECTS IN RELATION TO PLANTS 
 
 >65 
 
 the pistil and actually thrusts pollen into the stigmatic tube and 
 pushes it in firmly. The ovules develop 
 into seeds, some of which are consumed 
 by the larv;e. thoug-h plenty are left to 
 perpetuate the plant itself. Three species 
 of Pronuba are known, each restricted 
 to particular species of Yucca. Rilc)' 
 says that Yucca never produces seed 
 where Prouuha does nt)t occur or where 
 she is excluded artificially, and that 
 artificial pollination is rarely so success- 
 ful as the normal method. 
 
 Why does the insect do this? The lit- 
 tle nectar secreted at the base of the pistil 
 appears to be of no consequence, at pres- 
 ent, and the stigmatic fluid is not necta- 
 rian ; indeed, the tongue of Pronuba, used 
 in clinging to the stamen, seems to have 
 lost partially or entirely its sucking power, 
 and the alimentarv canal is resrarded as functionless 
 
 Pronuba yuccasella, fe- 
 male, gathering pollen 
 from anthers of Yucca. 
 Enlarged. 
 
 Ordina- 
 
 Pronuba moth ovipositing in flower of Yucca. Slightly reduced. 
 
 rily it is the flower which has become adapted to the insect, 
 which is enticed by means of pollen or nectar, but here is a 
 
266 
 
 ENTOMOLOGY 
 
 flower which — though entomophilous in general structure— has 
 apparently adapted itself in no way to the single insect upon 
 which it is dependent for the continuance of its existence. More 
 than this, the insect not only lal3ors without compensation in the 
 way of food, but has even become highly modified with refer- 
 ence to the needs of the plant, — its special modifications being 
 unparalleled among insects with the exception of bees, and 
 being more puzzling than the more extensive adaptations of 
 the bees wdien we take into consideration the impersonal nature 
 of the operations of Pronuba. Further investigation may 
 render these extraordinary interrelations more intelligible, or 
 less mysterious, than they are at present. 
 
 The bogus Yucca moth 
 Fig. 259. {Prodoxus qitiiiqiicpinic- 
 
 fclla) closely resembles 
 and associates with Pro- 
 uuha but oviposits in the 
 flower stalks of Yucca 
 and has none of the spe- 
 cial adaptive structures 
 found in Pronuba. 
 
 As regards floral adap- 
 tations, these examples 
 are sufficient for present 
 purposes ; many others 
 have been described l)y 
 the botanist ; in fact, the 
 adaptations for cross pol- 
 lination by insects are as 
 varied as the flowers them- 
 selves. 
 Insect Pollenizers. — The great majority of entomophilous 
 flowers are pollenized by bees of various kinds ; the apple, 
 pear, blackberry, raspberry and many other rosaceous plants 
 depend chiefly upon the honey bee, while clover cannot set seed 
 without the aid of Immble bees or honey bees, assisted possibly 
 
 Phlcgcthontius sc.vta visiting flower of Pi- 
 Reduced. 
 
INSECTS IN RELATION TO I'EANTS 
 
 267 
 
 l)v Ituttcrflies. I^ilies and orcliids trccinently em])l(>y l)utternics 
 and moths, as well as l)ees. and the milkweed is adapted in a 
 remarkal)le manner for pollination l)y 1)ntternies, moths and 
 some wasps, as was descrihed. Honeysuckle, lilac, azalea, 
 tohacco, l\'hnil(i, Pulurn and many other strctnt^ly scented anrl 
 conspicuous nocturnal llowers attract for their own uses the 
 
 Fig. 260. 
 
 A buttcrily, Fulitcs pcckiiis, stealing nectar from a flower of Iris z'crsicolor. 
 Slightly reduced. 
 
 long-tonged sphinx moths (Fig. 259) ; the evening primrose, 
 like milkweed, is a favorite of noctuid moths. Umhelliferous 
 plants are pollenized chietiy by various flies, but also by bees 
 and wasps. Pond lilies, golden rod and some other flowers 
 are pollenized largely by beetles, though the flowers exhibit no 
 special modifications in relation to these particular insects. It 
 
268 
 
 ENTOMOLOGY 
 
 Fig. 261 
 
 is noteworthy that polHnation is performed only by the more 
 highly organized insects, the bees heading the list. 
 
 Of all the insects that haunt the same flower, it frequently 
 happens that only a few are of any use to the flower itself ; 
 many come for pollen only; many secure the nectar illegiti- 
 mately ; thus bumble bees puncture the nectaries of columbine, 
 snapdragon and trumpet creeper from the outside, and wasps 
 of the genus Odyiicnis cut through the corolla of Pcntstcuwn 
 ItTZ'igafus, making a hole opposite each nectary ; then there are 
 the many insects that devour the floral organs, and the insects 
 which are predaceous or parasitic upon the others. In the 
 Iris, according to Needham, two small bees (Clisodon tcrmi- 
 luilis and Osniia disfiucta) are the most important pollenizers, 
 and next to them a few syrphid flies, while bumble bees also 
 
 are of some impor- 
 tance. The beetle 
 Trie hilts pigcr and sev- 
 eral small flies obtain 
 pollen without assist- 
 ing the plant, and 
 Painplula, Eudauius, 
 Chrysophanus a n d 
 some other butterflies 
 succeed after many 
 trials in stealing the 
 nectar from the out- 
 side (Fig. 260). A 
 weevil (Moiioiiychus 
 z'lilpcciiliis) punctures 
 the nectary, and the 
 flowing nectar then at- 
 tracts a great variety of 
 insects. Grasshoppers 
 and caterpillars eat the 
 flowers, an ortalid fly destroys the buds, and several parasitic 
 or predaceous insects haunt the plant ; in all, over sixty species 
 of insects are concerned in one way or another with the Iris. 
 
 A, right mandible; B, right maxilla; C, hypo- 
 pharynx, of a pollen-eating beetle, Euphoria inda. 
 Enlarged. (The mandibles are remarkable in 
 being two-lobed.) 
 
INSECTS IN RELATION TO PLANTS 
 
 269 
 
 Modifications of Insects with Reference to Flowers. — 
 
 While the manifold and ex(|nisite adaptations of tlie dower for 
 eross pollination have eni^aj^ed nniversal attention, very little 
 has heen recorded concernin_^' the adaptations of insects in re- 
 lation to tlowers. in fact, the adapta- 
 
 11 • 1 1 ,1 1 ^' "■• -6-- 
 
 tion IS larg'ely one-sided; tlowers ha\e 
 
 lieconie adjusted to the structure of in- 
 sects as a matter of \-ital necessity — to 
 init it that way — while insects have had 
 no such urgent need — so to speak — in 
 relation to floral structure. Thev ha\-e 
 been induenced by floral structure to 
 soiue extent, however, and in some cases 
 to a \-ery great extent, as appears from 
 their structural and i)hysiological adapta- 
 tions for gathering and using pollen and 
 nectar. 
 
 Among mandibulate insects, beetles 
 and caterpillars that eat the floral en- 
 velopes show' no special modifications 
 for this purpose ; pollen-feeding beetles, 
 however, usually have the mouth parts 
 densely clothed with hairs, as in Euphoria (Fig. 261). In 
 suctorial insects, the mouth parts are frequently formed with 
 reference to floral structure ; this is the case in many but- 
 terflies and particularly in Sphingid?e, in which the length of 
 the tongue bears a direct relation to the depth of the nectary in 
 the flowers that they visit. According to ]\Iiiller, the mouth 
 parts of Syrphidae, Stratyomyiid?e and Aluscicte are specially 
 adapted for feeding on pollen. In Apidse, the tongue as com- 
 pared wdth that of other Hymenoptera, is exceptionally long, 
 enabling the insect to reach deep into a flower, and is exqui- 
 sitely specialized (Fig. 127) for lapping up and sucking in 
 nectar. 
 
 Pollen-gathering flies and bees collect pollen in the hairs of 
 the body or the legs; these hairs, especially dense and often 
 
 Pollen-gathering hair 
 from a worker honey 
 bee, with a pollen grain 
 attached. Greatly mag- 
 nified. 
 
2/0 
 
 ENTOMOLOGY 
 
 twisted or branched (Figs. 262, 89) to hold the pollen, do not 
 occur on other than pollen-gathering species of insects. Caii- 
 dell found that out of 200 species of Hymenoptera only 22, 
 species had branched hairs and that these species belonged 
 without exception to the pollen-gathering group Anthophila, 
 
 Adaptive modifications of the legs of the worker honey bee. A, outer aspect of 
 left hind leg; B, portion of left middle leg; C, inner aspect of tibio-tarsal region of 
 left hind leg; D, tibio-tarsal region of left fore leg; a, antenna comb; h, brush; c, 
 coxa; CO, corbiculum; /, femur; pc, pollen combs; s. spur; sp, spines; ss, spines; t, 
 trochanter; t\, tibia; v, velum; w, wax pincers; /-5, tarsal segments; /, metatarsus, 
 or planta. 
 
 no representative of which was found without such hairs. 
 Similar branched hairs occur also on the flower-frequenting 
 Bombyliidae and Syrphidas. 
 
 The most extensive modifications in relation to flowers are 
 found in Proiiuba, as already described, and above all in 
 Apidse, especially the honey bee. 
 
 Honey Bee. — The thorax and abdomen and the bases of the 
 legs are clothed with flexible branching hairs (Fig. 262), 
 
INSECTS IN RELATION TO PLANTS 27 1 
 
 which entangle pollen grains. These are comhed ont of the 
 gatliering hairs hy means of special pollen combs ( JMg. 263, 
 C.f^c) on the inner snrface of the proximal segment of the hind 
 tarsus, the middle legs also assisting in this operation. JM-om 
 these comhs, the pollen is transferred to the pollen boskets, or 
 corbicula (Fig. 263, A, co) , of the outer surface of each hind 
 tihia ; hy crossing the legs, the pollen from one side is trans- 
 ferred to the corhiculum of the opposite side, the spines (ss) on 
 the posterior margin of the tihia serving- to scrape the pollen 
 from the coml)S. Arri\-ing at the nest, the hind legs are thrust 
 into a cell and the mass of pollen on each corhiculum is pried 
 out hy means of a spur situated at the apex of the middle tiljia 
 ( iMg. 263, B, s), this lever heing slipped in at the upper end 
 of the corhiculum and then pushed along the tibia under the 
 mass of pollen ; the spur is used also in cleaning the wings, 
 which explains its presence on queen and drone, as well as 
 worker, but the pollen-gathering structures of the hind legs 
 are confined to the worker. This is true also of the lea.v- 
 piiiccrs of the hind legs (Fig. 263, A, C, w) at the tibio-tarsal 
 articulation ; these nippers are used l)y the worker to remove 
 the wax plates from the al)domen. 
 
 For cleaning the antenn.'e, a front leg- is passed over an 
 antenna, which slips into a semicircular scraper (Fig. 263, 
 D, a) fashioned from the basal segment of the tarsus; when 
 the leg is bent at the tibio-tarsal articulation, an appendage, or 
 z'cliim [z'), of the tibia falls into place to complete a circular 
 comb, through which the antenna is drawn. This comb is 
 itself cleaned by means of a brush of hairs (b) on the front 
 margin of the tibia. A series of erect spines (sp) along the 
 anterior edge of the metatarsus is used as an eye brush, to 
 remove pollen grains or other foreign bodies from the hairs 
 of the compound eyes. The labium, hypopharynx and max- 
 \\\x (Fig. 54) are exquisitely constructed with reference to 
 gathering and sucking nectar ; the maxilhe are used also to 
 smooth the cell walls of the comb; the mandibles (Fig. 45, C). 
 notched in queen and drone but with a sharp entire edge in the 
 
2^2 
 
 ENTOMOLOGY 
 
 worker, are used for cutting, scraping and moulding wax, as 
 well as for other purposes. The entire digestive system of the 
 honey bee is adapted in relation to nectar and pollen as food ; 
 the pro\-entriculus forms a reservoir for honey and is even 
 provided at its mouth with a rather complex apparatus for 
 straining the honey from the accompanying' pollen grains, as 
 described hy Cheshire. The wax glands (Fig. 102) are re- 
 markable specializations in correlation with the food habits, as 
 are also the various cephalic glands, the chief functions of 
 which are given as : ( i ) digestion, as the conversion of cane 
 sugar into grape sugar, and possibly starch into sugar; (2) 
 the chemical alteration of wax; (3) the production of special 
 food substances, which are highly important in larval develop- 
 ment. 
 
 Numerous special sensory adaptations also occur. In fact, 
 the whole organization of the honey bee has become pro- 
 foundly modified in relation to nectar and pollen. Many 
 other insects have the same food but none of them sustain such 
 intimate relations to the flowers as do the bees. 
 
 Ant-Plants. — There are several kinds of tropical plants 
 Avhich are admirably suited to the ants that inhabit them. In- 
 deed, it is often asserted that these plants have become modified 
 
 Fig. 264. 
 
 Acacia spha:rocc\mala, an ant-plant, h. one of the " Helt's bodies"; g. gland; s, .>, 
 ■hollow stipular thorns, perforated by ants. Reduced. — From Strasburger's Lchrbuch 
 dcr Botanik. 
 
INSECTS IN RELATION TO PLANTS 
 
 273 
 
 with special reference to their use Ijy ants, ihouqh tliis is a 
 gTatuitous and improbable assumption. 
 
 Belt found several species of Acacia in Xicaras^na and the 
 Amazon \-alley which ha\e laro-e hollow slipular thorns, in- 
 habited by ants of the g-enus Psciidoniyniia. I'hc ants enter 
 by boring" a hole near the a])ex of a thorn ( l^^ig. 264, .v). The 
 plant affords the ants food as well as shelter, for glands {i^) 
 
 Fig. 265. 
 
 Fig. 266. 
 
 Portion of young stem of Cccrofia odoiol^iis, 
 showing internodal pits, a and b. Natural size. 
 
 Figures 265-267 are from Schimper's Fflanzcn- 
 gcograpTuc. 
 
 Cccrofia adcnopns. Por- 
 tion of a stem, split so as 
 to show internodal cham- 
 bers and the intervening 
 septa perforated by ants. 
 
 at the bases of the petioles secrete a sugary fluid, while many 
 of the leaflets are tipped with small egg-shaped or pear-shaped 
 appendages (b) known as " Belt's bodies," which are rich in 
 albumin, fall ofl^ easily at a touch, and are eaten by the ants. 
 These ants drive away the leaf-cutting species, incidentally 
 protecting the tree in which they live. 
 19 
 
274 
 
 ENTOMOLOGY 
 
 The ant-trees (Cccropia adcnopus) of Brazil and Central 
 America have often been referred to by travelers. When 
 one of these trees is handled roughly, hosts of ants rush out 
 P ,_ from small openings in the 
 
 stems and pugnaciously at- 
 tack the disturber. Just 
 above the insertion of each 
 leaf is a small pit (Fig. 265, 
 a, b) where the wall is so 
 thin as to form a mere dia- 
 phragm, through which an 
 ant (probably a fertilized 
 female) bores and reaches a 
 hollow internode. To es- 
 tablish communication Ije- 
 tween the internodal cham- 
 bers, the ants bore through 
 the intervening septa (Fig. 
 266). They seldom leave 
 the Cccropia plant, unless 
 disturbed, and even keep 
 herds of aphids in their 
 abode. The base of each 
 petiole bears (Fig. 267) tender little egg-like bodies (" ]\Iul- 
 ler's ])odies ") which the ants detach, store away and eat; 
 the presence of these bodies is a sure sign that the tree is un- 
 inhabited by these ants, which, by the way, belong to the genus 
 A:::fcca. 
 
 It is too much to assert that the ants protect the Cccropia 
 plant /;/ return for the food and shelter which they obtain. 
 All ants are hostile to all other species of ants, with few excep- 
 tions, and even to other colonies of their own species; so that 
 their assaults upon leaf-cutting ants are by no means special 
 and adaptive in their nature, and any protection that a plant 
 derives thereby is merely incidental. Furthermore, hollow 
 stems, glandular petioles and pitted stems are of common oc- 
 
 Cccropia adoiopus. Base of petiole showing 
 " Miiller's bodies." Slightly reduced. 
 
INSECTS IN RELATION TO PLANTS 
 
 275 
 
 currence wlien they bear no relation to the needs of ants. 
 These interrelations oi ants and plants are too often misinter- 
 preted in popular and uncritical accounts of the subject. 
 
 The interesting;- habits of the leaf-cuttiui;- ants in relation to 
 the plants that they attack are described in a subsequent chap- 
 ter, where will be found also an account of the harvesting?- ants. 
 
 .'oS. 
 
 HyJiu'tliyti 
 
 Dwntanitm. Section of pseudo-bulb, to show chamber 
 One fourth natural size. — After Forel. 
 
 inhabited by ants. 
 
 The epiphytic plants Mynitccodia and Hydnopliytuui, of 
 Java, form spongy bulb-like masses, the chambers of which 
 are usually tenanted by ants, which rush forth when disturbed. 
 These lumps (Fig. 268) are primarily water-reservoirs, but 
 the ants utilize them by boring into them and from one cham- 
 ber into another. In plants of the genus Huniholdtia the ants 
 can enter the hollow internodes through openings that already 
 exist. 
 
CHAPTER IX 
 
 INSECTS IN RELATION TO OTHER ANIMALS 
 
 I. The General Subject 
 
 On the one hand, insects may derive their food from other 
 animals, either hving' or dead : on the other hand, insects them- 
 selves are food for other animals, especially fishes and birds, 
 against which they protect themselves by various means, more 
 or less effective. These topics form the principal subject of 
 the present chapter. 
 
 Predaceous Insects. — Innumerable aquatic insects feed 
 largely or entirely upon microscopic Protozoa, Rotifera, Ento- 
 mostraca. etc. ; this is especially the case with culicid and chi- 
 ronomid larvae. Many aquatic Hemiptera and Coleoptera 
 prey upon planarians, nematodes, annelids, molluscs and 
 crustaceans ; Bclostoina sometimes pierces the bodies of tad- 
 poles and small fishes ; Dytiscus also kills young fishes occa- 
 sionally and is distinctly carnivorous both as larva and imago. 
 Among terrestrial insects, Carabid?e are notably predaceous, 
 preying not only upon other insects but also upon molluscs, 
 myriopods, mites and spiders. Ants do not hesitate to attack all 
 kinds of animals; in the tropics, the wandering ants (Eciton) 
 attack lizards, rats and other vertebrates, and it is said that 
 even huge serpents, when in a torpid condition, are sometimes 
 killed by armies of these pugnacious insects. 
 
 ]\Iosquitoes affect not only mammals but also, though 
 rarely, fishes and turtles. The gad flies (Tabanidse) torment 
 horses and cattle by their punctures; and the black-flies, or 
 buffalo gnats (Siimtliuni) , persecute horses, mules, cattle, 
 fowls, and frequently become unendurable even to man. The 
 notorious tsetse fly {Glossiiia morsifaiis) of South Africa 
 spreads a deadly disease among horses, cattle and dogs, by 
 
 276 
 
INSECTS IN RELATION TO OTHER ANIMALS 2/7 
 
 inocnlafing them with a protozoan l)loo(l-parasite, to the effects 
 of whicli. fortunately, man is not susceptihle. 
 
 Parasitic Insects. — Insects l)cl()no-ing- to several diverse 
 orders have hecomc ])ccnliarl}- modified to exist as parasites 
 either upon or within the hodies of birds or mammals. 
 
 Almost all birds are infested by Mallophaga, or Ijird lice, of 
 which Kellogg has catalogued 264 species from 257 species of 
 Xorth American birds. Sometimes a species of Mallophaga is 
 restricted to a single species of bird, though in the majority of 
 cases this is not so. Several mallophagan species often infest 
 a single bird; thus nine species occur on the hen, and no less 
 than twelve species, representing five genera, on the American 
 coot. These parasites spread by contact from male to female, 
 from old to young, and from one bird to another when the 
 birds are gregarious. Wdien a single species of bird louse 
 occurs on two or more hosts, these are almost always closely 
 allied, and Kellogg has suggested the interesting possibility 
 that such a species has persisted unchanged from a host which 
 was the common ancestor of the two or more present hosts. 
 ^Mallophaga are not altogether limited to birds, however, for 
 they may be found on cattle, horses, cats, dogs, and some other 
 mammals ; Kellogg records eighteen species from fifteen 
 species of mammals. These biting lice feed, not upon blood, 
 l)ut upon epidermal cells and portions of feathers or hairs. 
 They have flat tough bodies (Fig. 17), with no traces of wings, 
 and a large head with only simple eyes ; the eggs are glued to 
 feathers or hairs. 
 
 iNIammals only are infested by the sucking lice, or Pediculidce 
 (Hemiptera). These (Fig. 2t,) have a large oval or rounded 
 abdomen, no wings, a small head, minute simple eyes or none, 
 and claws that are adapted to clutch hairs ; the eggs are glued 
 to hairs. Sucking lice affect horses, cattle, sheep, dogs, mon- 
 keys, seals, elephants, etc., and man is parasitized by three 
 species, namely, the head louse (Pcdiciiliis caj^itis), the body 
 louse {Pcdiciiliis I'csfiiiiciifi) , and the crab louse (Phthirius 
 pubis), though the first two are possibly the same species. 
 
278 ENTOMOLOGY 
 
 An anomalous beetle, PlatypsyUiis casforis, occurs through- 
 out North America and also in Europe as a parasite of the 
 beaver. 
 
 The fleas, allied to Dii:)tera but constituting a distinct order 
 ( Siphonaptera), are familiar parasites of chickens, cats, dogs 
 and human beings. These insects (Fig. 30) are well adapted 
 by their laterally compressed bodies for slipping about among 
 hairs, and their saltatory powers and general elusiveness are 
 well known. Their wings are reduced to mere rudiments, their 
 eyes when present are minute and simple and their mouth 
 parts are suctorial. 
 
 Among Diptera, there are a few external parasites, the best 
 known of which is the sheep tick {Mdophagiis 0T'/;/;/,y) , though 
 several highly interesting but little-studied forms are parasitic 
 upon birds. and bats. 
 
 The larvse of the hot flies (CEstridcX) are common internal 
 parasites of mammals. The sheep hot fly {CEsfnis oi'is) 
 deposits her eggs or lar\'?e on the nostrils of sheep: the 
 maggots develop in the frontal sinuses of the host, causing 
 vertigo or even death, and when full grown escape through 
 the nostrils and pupate in the soil. The horse bot fly {Gas- 
 trophilus eqiii) glues its eggs to the hairs of horses, especially 
 on the fore legs and shoulders, whence the larvce are licked off 
 and swallowed; once in the stomach, the hots fasten them- 
 selves to its lining, 1)y means of special hooks, and withstand 
 almost all eft'orts to dislodge them ; though when the hots have 
 attained their growth they release their hold and pass with the 
 excrement to the soil. Bots of the genus Hypodcnua form 
 tumors on cattle and other mammals, domesticated or wild. 
 The ox-warble (H. lincata, Fig. 210, /) reaches the oesophagus 
 of its host in the same manner as the horse bot, according to 
 Curtice, but then makes its way into the subcutaneous tissue 
 and causes the well-known tumors on the back of the animal; 
 when full grown the bots squirm out of these tumors and drop 
 to the ground, leaving permanent holes in the hide. 
 
 Parasitism in General. — Parasitic insects evidentlv do not 
 
INSECTS IN RELATION TO OTHER AXniALS 2/9 
 
 constitute a phylog-cnetic unit, Imt the parasitic habit has arisen 
 independently in many different orders. These insects do. 
 however, agree superficially, in certain respects, as the result 
 of what may be termed convergence of adaptation. Thus a 
 dipterous larx'a, li\-ing as an internal ])arasite. in the i)resence 
 of an abundant supply of food, has no legs, no e}"es or anten- 
 nae, and the head is reduced to a mere rudiment, sufticient 
 simply to support a pair of feeble jaws; the skin, moreover, is 
 no longer armor-like l)ut is thin and delicate, the body is com- 
 pact and fleshy, and the digestive system is of a simplified type. 
 The same modilications are found in hymenopterous larv?e, 
 under similar food-conditions, except that the head usually 
 undergoes less reduction. The various external parasites lack 
 wings, almost invariably, and the eyes, instead of being com- 
 pound, are either simple or else absent. In some special cases, 
 however, as in a few dipterous parasites of birds and bats, the 
 wings are present, either permanently or only temporarily, 
 enabling the insects to reach their hosts. 
 
 This so-called parasitic degeneration, widespread among 
 animals in general and consisting chiefly in the reduction or 
 loss of locomotor and sensory functions in correlation with an 
 immediate and plentiful supply of food, results in a simplicity 
 of organization which is to be regarded — not as a primitive 
 condition — but as an expression of what is, in one sense, a 
 high degree of specialization to peculiar conditions of life. 
 This exquisite degree of adaptation to a special environment, 
 however, sacrifices the general adaptability of the animal, — 
 makes it impossible for a parasite to adapt itself to new con- 
 ditions ; and while parasitism may be an immediate advantage 
 to a species, there are few parasites that have attained any 
 degree of dominance among animals. Ichneumonidce, to be 
 sure, are remarkably dominant among insects, but here the 
 parasitic adaptations are limited for the most part to the larval 
 stage and the adults may be said to be as free for new adapta- 
 tions as are any other Hymenoptera. 
 
 Scavenger and Carrion Insects. — Not a few families of 
 
28o ENTOMOLOGY 
 
 Diptera and Coleoptera derive their food from dead animal 
 matter. The aquatic famihes Dytiscid?e and Gyrinidse are 
 largely scavengers. Among terrestrial forms, Silphidse feed 
 on dead animals of all kinds; the burying beetles (Necroph- 
 onts). working in pairs, undermine and bury the bodies of 
 birds, frogs and other small animals, and lay their eggs in the 
 carcasses ; Histerid?e and Staphylinicke are carrion beetles, and 
 Dermestid^ attack dried animal matter of almost every de- 
 scription, their depredations upon furs, feathers, museum 
 specimens, etc., being familiar to all. Ants are famous as 
 scavengers, destroying decaying organic matter in immense 
 quantities, particularly in the tropics. ]\Iany Scarab^eidse feed 
 upon excrementitious matter, for example the " tumble-bugs," 
 which are frequently seen in pairs, laboriously rolling along or 
 burying a large ball of dung, which is to serve as food for the 
 larva. 
 
 Insects as Food for Vertebrates. — Lizards, frogs and 
 toads are insectivorous, especially toads. The American toad 
 feeds chiefly upon insects, which form yy per cent, of its food 
 for the season, the remainder consisting of myriopods, spiders, 
 Crustacea, molluscs and worms, according to the observations 
 of A. H. Kirkland, who states that Lepidoptera form 28 per 
 cent, of the total insect food, Coleoptera 27, Hymenoptera 19 
 and Orthoptera 3 per cent. The toad does not capture dead 
 or motionless insects but uses its extensile sticky tongue to lick 
 in moving insects or other prey, which it captures with sur- 
 prising speed and precision. In the cities one often sees many 
 toads under an arc-light engaged in catching insects that fall 
 anywhere near them. Though its diet is varied and some- 
 what indiscriminate, the toad consumes such a large propor- 
 tion of noxious insects, such as May beetles and cutworms, 
 that it is unquestionably of service to man. 
 
 Aloles are entirely insectivorous and destroy large numbers 
 of white grubs and caterpillars ; field mice and prairie squirrels 
 eat many insects, especially grasshoppers, and the skunk rev- 
 els in these insects, though it eats beetles frequently, as does 
 
INSECTS IN RELATION TO OTHER ANIMALS 28 1 
 
 also the raccoon, whicli is to some extent insectivorous. 
 Monkeys are onini\-orotis l)nt dcNonr many kinds of insects. 
 
 W'itli these hasty references, we may i)ass at once to tlie 
 siil)ject of the insect food of hshes and l)irds. 
 
 Insects in Relation to Fishes. — Insects constitute the 
 most important portion of the food of a(hdt fresh water fishes, 
 furnishiui^- forty per cent, of their food, acconhng- to Dr. 
 Forhes, from whose vahia1)le writint^s the followint^- extracts 
 are taken, 
 
 " The principal insecti\'orous tishes are the smaller species, 
 whose size and food structures, when adult, unht them for the 
 capture of Entomostraca, and yet do not bring- them within 
 reach of fishes or Mollusca. Some of these fishes have pecu- 
 liar habits which render them especially dependent upon insect 
 life, the little minnow Phciiacobiiis, for example, which, ac- 
 cording to my studies, makes nearly all its food from insects 
 ( ninety-eight per cent. ) found under stones in running water. 
 Xext are the pirate perch, Aplivcdodcnis (ninety-one per 
 cent. ) , then the darters ( eighty-seven per cent. ) , the croppies 
 (seventy-three per cent.), half-grown sheepshead (seventy- 
 one per cent.), the shovel fish (fifty-nine per cent.), the chub 
 minnow (fifty-six per cent.) , the black warrior sunfish (CIktiio- 
 bryttus) and the brook silversides (each fifty-four per cent.), 
 and the rock bass and the cyprinoid genus Notropis (each 
 fifty-two per cent.). 
 
 " Those which take few insects or none are mostly the mud- 
 feeders and the ichthyophagous species, Ainia (the dog-fish) 
 being the only exception noted to this general statement. 
 Thus we find insects wholly or nearly absent from the adult 
 dietary of the burbot, the pike, the gar, the black bass, the wall- 
 eyed pike, and the great river catfish, and from that of the 
 hickory shad and the mud-eating minnows (the shiner, the fat- 
 head, etc.). It is to be noted, however, that the larger fishes 
 all go through an insectivorous stage, whether their food 
 when adult be almost wholly other fishes, as with the gar and 
 the pike, or molluscs, as with the sheepshead. The mud- 
 
282 ENTOMOLOGY 
 
 feeders, however, seem not to pass through this stage, but to 
 adopt the Hmophagous habit as soon as they cease to depend 
 upon Entomostraca. 
 
 " Terrestrial insects, dropping into the water accidentally 
 or swept in l)y rains, are evidently diligently sought and 
 largeh- depended upon by several species, such as the pirate 
 perch, the brook minnow, the top minnows or killifishes 
 ( cyprinodonts ) , the toothed herring and several cyprinoids 
 {Scnwtiliis, Piuicphalcs and Notropis). 
 
 " Among aquatic insects, minute slender dipterous larvae, 
 belonging mostly to Chironoinus, Corcthra and allied genera, 
 are of remarkable importance, making, in fact, nearly one 
 tenth of the food of all the fishes studied. They are most 
 abundant in Pliciiacobius and Ethcostoiiia, which genera have 
 become especially adapted to the search for these insect forms 
 in shallow rocky streams. Next I found them most generally 
 in the jiirate perch, the brook silversides, and the stickleback, 
 in which they averaged forty-five per cent. They amounted 
 to about one third the food of fishes as large and important 
 as the red horse and the river carp, and made nearly one fourth 
 that of fifty-one buffalo fishes. They appear further in con- 
 siderable quantity in the food of a number of the minnow 
 family (Notropis, Pimcphalcs. etc.), which habitually fre- 
 quent the swift waters of stony streams, but were curiously 
 deficient in the small collection of miller's thumbs (Cottid?e) 
 which hunt for food in similar situations. The sunfishes eat 
 but few of this important group, the average of the famil) 
 being only six per cent. 
 
 " Larvns of aquatic beetles, notwithstanding the abundance 
 of some of the forms, occurred in only insignificant ratios, but 
 were taken by fifty-six specimens, belonging to nineteen of the 
 species, — more frequently by the sunfishes than by any other 
 group. The kinds most commonly captured were larvae of 
 Gyrinidae and Hydrophilidae ; whereas the adult surface beetle? 
 themselves {Gyrinus, Dincutcs, etc.) — whose zigzag-darting 
 swarms no one can have failed to notice — were not once en- 
 countered in my studies. 
 
TNSECTS IN RELATION TO OTHER ANIMALS 283 
 
 " The almost equally well-known slender water-skippers 
 {H\i^iu>trrcJius) seem also C(Mn])letely ]:)r()tectc(l by their habits 
 and acti\-it\' from capture b_\' tishcs, only a singie specimen oc- 
 curring in the food of all my s])ecimens. Indeed, the true 
 water bugs ( llemiptera) were generally rare, with the excep- 
 tion of the small soft-bodied genus Corisa, which was taken by 
 one hundred and ten specimens, belonging to twenty-seven 
 species, — most alnindantly by the sunfishes and top minnows. 
 
 " h'rom the order Neuroptera [in the broad sense] fishes 
 draw a larger part of their food than from any other single 
 group. In fact, nearly a hfth of the entire amount of food 
 consumed by all the adult hshes examined b}' me consisted of 
 aquatic larvce of this order, the greater part of them larvae of 
 day flies (Ephemerid?e), principally of the genus Hcxagenia. 
 These neuropterous larvse were eaten especially by the miller's 
 thumb, the sheepshead, the white and striped bass, the common 
 perch, thirteen species of the darters, both the black bass, seven 
 of the sunfishes, the rock bass and the croppies, the pirate 
 perch, the brook silversides, the sticklebacks, the mud minnow, 
 the top minnows, the gizzard shad, the toothed herring, twelve 
 species each of the true minnow family and of the suckers and 
 buffalo, li\e catfishes, the dog-fish, and the shovel fish, — 
 seventy species out of the eighty-seven which I ha\'e studied. 
 
 " Among the above, I found them the most important food 
 of the white bass, the toothed herring, the shovel fish (fifty- 
 t)ne per cent.), and the croppies; while they made a fourth or 
 more of the alimentary contents of the sheepshead ( forty-six 
 per cent.), the darters, the pirate perch, the common sunfishes 
 {Lcpoinis and CJiccnohrytius) . the rock l^ass, the little pickerel, 
 and the common sucker (thirty-six per cent.). 
 
 " Ephemerid larvcC were eaten by two hundred and thirteen 
 specimens of forty-eight species — not counting young. The 
 larvcT of Hcxagenia, one of the commonest of the ' river 
 flies,' was by far the most important insect of this group, this 
 alone amounting to about half of all the Neuroptera eaten. 
 Thev made nearlv one half of the food of the shovel fish, more 
 
284 ENTOMOLOGY 
 
 than one tenth that of the sunfishes, and the principal food re- 
 sources of half-grown sheepshead ; but were rarely taken by 
 the sucker family, and made only five per cent, of the food of 
 the catfish group. 
 
 " The various larvae of the dragon flies, on the other hand, 
 were much less frequently encountered. They seemed to be 
 most a1)undant in the food of the grass pickerel (twenty-five 
 per cent.), and next to that, in the croppie. the pirate perch, 
 and the common perch (ten to thirteen per cent.). 
 
 " Case-worms (Phryganeidse) were somewhat rarely 
 found, rising to fifteen per cent, in the rock bass and tweh'e 
 per cent, in the minnows of the Hybopsis group, but otherwise 
 averaging from one to six per cent, in less than half of the 
 species." 
 
 Insects in Relation to Birds. — From an economic point 
 of view the relations between birds and insects are extremely 
 important, and from a purely scientific standpoint they are no 
 less important, involving as they do biological interactions of 
 remarkable complexity. 
 
 The prevalent popular opinion that birds in general are of 
 inestimable value as destroyers of noxious insects is a correct 
 one, as Dr. Forbes proved, from his precise and extensive 
 studies upon the food of Illinois birds, involving a laborious 
 and difficult examination of the stomach contents of many 
 hundred specimens. All that follows is taken from Forbes, 
 when no other author's name is mentioned, and though the 
 percentages given by Forbes apply to particular years and 
 would undoubtedly vary more or less from year to year, they 
 are here for convenience regarded as representative of any 
 year and are spoken of in the present tense. About two thirds 
 of the food of birds consists of insects. 
 
 Robin. — The food of the robin in Illinois, from February to 
 Alay inclusive, consists almost entirely of insects ; at first, 
 larvae of Bibio albipciiiiis for the most part, and then caterpil- 
 lars and various beetles. When the small fruits appear, these 
 are largely eaten instead of insects ; thus in June, cherries and 
 
INSECTS IN RELATION TO OTHER ANIMALS 285 
 
 raspberries form fifty-li\e ])er cent, and insects (ants, cater- 
 pillars, \vire-\V(»rms and l"aral)id;c) forty-two ])er cent, of tlie 
 food : and in Jnly, ras])l)erries. blackberries and currants form 
 seventv-nine per cent, and insects (mostly caterpillars, beetles 
 and crickets) l)nt twenty per cent, of the food. In Angnst. 
 insects rise to forty-three per cent, and fruits drop to tifty-six 
 per cent., and these are mostly cherries, of which two thirds 
 are wild kinds. In Septemljer. ants form tifteen per cent, of 
 the food, caterpillars five per cent, and fruits (mostly grapes, 
 mountain-ash berries and moonseed berries) seventy per cent. 
 In October, the food consists chiefly of wild grapes (fifty- 
 three per cent.), ants (thirty-five per cent.), and caterpillars 
 (six per cent.). 
 
 For the }-ear, judging from the stomach contents of one 
 hundred and fourteen birds, garden fruits form only tw^enty- 
 nine per cent, of the food of the robin, while insects constitute 
 two thirds of the food. The results are confirmed by those 
 of Professor Beal in Michigan, who found that more than 
 forty-two per cent, of the food of the robin consists of insects 
 with some other animal matter, the remainder being made up 
 of \arious small fruits, but notably the wild kinds. 
 
 Upon the whole, the robin deserves to be protected as an 
 energetic destroyer of cutworms, wdiite grubs and other injuri- 
 ous insects, and the comparatively few culti\-ated berries that 
 the bird appropriates are ordinarily but a meagre compensa- 
 tion for the valuable ser\-ices rendered to man by this familiar 
 bird. 
 
 Catbird. — Xot so much can be said for the catbird, however, 
 for though its food habits are similar to those of the robin, it 
 arrives later and departs earlier, with the result that it is less 
 dependent than the robin upon insects and that berries form a 
 larger percentage of its total food. 
 
 In May, eighty-three per cent, of the food of the catbird 
 consists of insects, mostly beetles (Carabidje, Rhynchophora, 
 etc.), crane-flies, ants and caterpillars (Noctuidae) ; while dry 
 sumach berries are eaten to the extent of seven per cent. For 
 
286 ENTOMOLOGY 
 
 the first half of June, the record is much the same, with an in- 
 crease, ho\ve\er, in the num1)er of May beetles eaten ; in the 
 second half of the month, the food consists chiefly of small 
 fruits, especially raspberries, cherries and currants ; so that for 
 the month as a whole, only forty-nine per cent, of the food is 
 made up of insects. This falls to eighteen per cent, in July, 
 when three quarters of the food consists of small fruits, 
 mostly blackberries, however. In August, with the diminu- 
 tion of the smaller cultivated fruits, the percentage of insects 
 rises to forty-six per cent., nearly one half of which is made 
 up of ants and the rest of caterpillars, grasshoppers, Hemip- 
 tera, Coleoptera, etc. In September, with the appearance of 
 wild cherries, elderberries, Virginia creeper berries and 
 grapes, these are eaten to the extent of seventy-six per cent., 
 the insect element of the food falling to twenty-one per cent., 
 of which almost half consists of ants, and the remainder of 
 beetles and a few caterpillars. 
 
 For the entire year, as appears from the study of seventy 
 specimens by Forbes, insects form forty-three per cent, of the 
 food of the catbird and fruits fifty-two per cent. As the in- 
 jurious insects killed are ofTset by the beneficial ones destroyed, 
 " the injury done in the fruit-garden by these birds remains 
 without compensation unless we shall find it in the food of the 
 voung," says Professor Forbes. And this has been found, to 
 the credit of the catbird ; for Weed learned that the food of 
 three nestlings consisted of insects, sixty-two per cent, of 
 which were cutworms and four per cent, grasshoppers ; while 
 Judd found that fourteen nestlings had eaten but four per 
 cent, of fruit, the diet being chiefly ants, beetles, caterpillars, 
 spiders and grasshoppers. In fact. Weed believes that, on 
 the whole, the benefit received from the catbird is much greater 
 than the harm done, and that its destruction should never be 
 permitted except when necessary in order to save precious 
 crops. 
 
 Bluebird. — The excellent reputation which the bluebird 
 bears everywhere as an enemy of noxious insects is well-de- 
 
INSECTS IN RELATION TO OTHER ANIMAES 28/ 
 
 served. Fiv^m a stndv (if one hundred and ei,<;ht illinois si~)cci- 
 mens, h^)rl)es finds lliat se\'enty-eit;'lil per cent, of tlie food for 
 tlie year consists of insects, eight per cent, of .\rachnida, one 
 per cent, of jnhd;e and only thirteen per cent, of veo-eta1)le 
 matter. e(hble fruits forming merely one per cent, of the entire 
 food. The insects eaten are mostl}- cater])illars (chielly cut- 
 worms). Orthoptera (grasshoppers and crickets) and Cole- 
 ojitera (Carabichc and Scaral)<Ti(l;e ). ddiough some of the 
 insects are more or less beneficial to man. such as C'arabid.-e 
 and IchneumonidcT (respectively predaceous and parasitic), 
 the beneficial elements form only twenty-two per cent, of the 
 food for the vear. as against forty-nine per cent, of injurious 
 elements, the remaining twenty-nine per cent, consisting of 
 neutral elements. The food of the nestlings, according to 
 Judd. is essentially like that of the adults, being " Ijeetles. 
 caterpillars, grasshoppers, spiders antl a few snails." 
 
 Other Insectivorous Birds. — Weed and Dearborn, from 
 whose excellent work the following notes are taken, find that 
 the common chickadee devours immense numbers of canker- 
 worms, and that more than half its food during winter con- 
 sists of insects, largely in the form of eggs, including those of 
 the common tent caterpillar ( C. aincricaiia) < the fall web- 
 worm {H. ciiiica) and particularly plant lice, whose eggs, 
 small as they are. form more than one fifth of the entire food; 
 more than four hundred and fifty of them are sometimes eaten 
 by a single bird in one day. and the total number destroyed 
 annually is inconceivably large. The house wren is alm;)st 
 exclusively insectivorous, feeding upon caterpillars and other 
 larvae, ants, grasshoppers, gnats, beetles, bugs, spiders, and 
 myriopods. The swallows, also, are highly insectivorous; 
 " most of their food is captured on the wing", and consists of 
 small moths, two-winged flies, especially crane-flies, beetles in 
 great variety, flying- bugs, and occasionally small dragon-flies. 
 The young are fed with insects." Ninety per cent, of the food 
 of the kingbird " consists of insects, including such noxious 
 species as May-beetles, click-beetles, wheat and fruit weevils. 
 
288 
 
 ENTOMOLOGY 
 
 grasshoppers, and leafhoppers." The honey bees eaten l)y 
 this bird are insignificant in number. \\^oodpeckers destroy 
 immense numbers of wood-boring larvae, bark-insects, ants, 
 caterpillars, etc. The cuckoos " are unique in having a taste 
 for insects that other birds reject. Most birds are ready to 
 devour a smooth caterpillar that comes in their way, but they 
 leave the hairy varieties severely alone. The cuckoos, how- 
 ever, make a specialty of devouring such unpalatable crea- 
 tures : e\en stink-bugs and the poisonous spiny larv?e of the lo 
 moth are freely taken." Caterpillars form fifty per cent, of 
 the food for the year; Orthoptera (grasshoppers, katydids, 
 and tree crickets), thirty per cent. ; Coleoptera and Hemiptera, 
 six per cent, each ; and flies and ants are taken in small quanti- 
 ties. " The nestling birds are fed chiefly with smooth cater- 
 pillars and grasshoppers, their stomachs probably being unable 
 to endure the hairy caterpillars. All in all. the cuckoos are of 
 the highest economic value. They do no harm and accom- 
 plish great good. If the orchardist could colonize his or- 
 chards with them, he would escape much loss." The quail 
 feeds largely upon insects during the summer, frequently eat- 
 ing the Colorado potato beetle and the army worm ; the prairie 
 hen has similar food habits but lives almost exclusively on 
 grasshoppers, when these are abundant. 
 
 The Insect Food of Birds. — " There are few groups of 
 injurious insects that enter so largely into the composition of 
 the food of birds as do the locusts, or short-horned grasshop- 
 pers, of the family Acridiid^e. The enormous destructive 
 power of these insects is well known, but our indebtedness to 
 birds in checking their oscillations is less generally recog- 
 nized." Professor Aughey. who has made extensive studies 
 upon the relation of birds to the Rocky Mountain locust, 
 found that upon one occasion 6 robins had eaten 265 of these 
 insects, 5 catbirds 152. 3 bluebirds 67. 7 barn swallows 139, 7 
 night hawks 348. 16 yellow-billed cuckoos 416, 8 flickers 252. 
 8 screech owls 219. and i humming bird 4; while crows and 
 blue-jays had eaten large numbers of the locusts ; and grouse. 
 
INSECTS IN RELATION TO OTHER ANIMALS 289 
 
 quail and prairie hen, enormons numbers. Even shore birds, 
 such as g-eese, ducks, guhs and pehcans came to share in the 
 feast. Aughey estimated that the locusts eaten in one day by 
 the passerine birds of the eastern half of Nebraska were 
 sufficient to destroy in a single day 174.397 tons of crops, 
 valued at $1,743.97. 
 
 Weed and Dearborn state that, of Hemiptera, Jassidse are very 
 often found in the stomachs of birds, and that aphids and their 
 eggs form a large part of the food of many of the smaller birds, 
 such as the warblers, nuthatches, kinglets and chickadees. 
 " A large proportion of the caterpillars of the Lepidoptera are 
 eagerly devoured by birds, forming" an important element of 
 the food of many species." The hairy caterpillars are eaten 
 by cuckoos and blue-jays and the large saturniid caterpillars, 
 such as cecropia and polypJiemus, by some of the hawks. Al- 
 most all kinds of Coleoptera are food for birds, but especially 
 the grubs of Scarabceidse, which are eagerly devoured by 
 robins, blackbirds, crows and other birds. Of the Diptera, 
 Cecidomyiidae and other gnats are eaten by swallows, swifts 
 and night hawks ; while Tipulidae are often found in the stom- 
 achs of birds. Among Hymenoptera, ants are eaten exten- 
 sively by woodpeckers, catbirds and many other species, as are 
 also Ichneumonida^ and other parasitic forms — these last by 
 the flycatchers in particular. 
 
 The Regulative Action of Birds upon Insect Oscilla- 
 tions. — The worst injuries by insects are done by species that 
 fluctuate excessively in number as the result of variations in 
 those manifold forces that act as checks upon the multiplica- 
 tion of the species. 
 
 In order to determine whether birds do anything to reduce 
 existing oscillations of injurious insects, Professor Forbes 
 made some admirable studies upon the food of birds which 
 were shot in an Illinois apple orchard which was being ravaged 
 by canker-worms. In this orchard, birds were present in 
 extraordinary number and variety, there being at least thirty- 
 five species, most of which were studied by Forbes, from 
 
290 ENTOMOLOGY 
 
 whose exhaustive tables the following food-percentages are 
 taken : 
 
 Birds Examined. Insects. Canker-worms. 
 
 Robin, 
 
 9 
 
 93 % 
 
 21 
 
 Catbird, 
 
 14 
 
 98 
 
 15 
 
 Brown Tlirush, 
 
 4 
 
 94 
 
 12 
 
 Bluebird, 
 
 5 
 
 98 
 
 12 
 
 Black-capped Chickadee, 
 
 2 
 
 100 
 
 61 
 
 House Wren, 
 
 5 
 
 91 
 
 46 
 
 Tennessee Warbler, 
 
 I 
 
 100 
 
 80 
 
 Summer Yellow Bird, 
 
 5 
 
 94 
 
 67 
 
 Black-throated Green Warbler, 
 
 I 
 
 100 
 
 70 
 
 Maryland Yellow-throat, 
 
 2 
 
 100 
 
 Zl 
 
 Baltimore Oriole, 
 
 3 
 
 100 
 
 40 
 
 To quote Forbes : " Three facts stand out very clearly as 
 results of these investigations: i. Birds of the most varied 
 character and habits, migrant and resident, of all sizes, from 
 the tiny wren to the blue-jay, birds of the forest, garden and 
 meadow, those of arboreal and those of terrestrial habits, were 
 certainly either attracted or detained here by the bountiful 
 supply of insect food, and were feeding freely upon the species 
 most abundant. That thirty-five per cent, of the food of all 
 the birds congregated in this orchard should have consisted of 
 a single species of insect, is a fact so extraordinary that its 
 meaning can not be mistaken. Whatever power the birds of 
 this vicinity possessed as checks upon destructive irruptions of 
 insect life, was being largely exerted here to restore the broken 
 balance of organic nature. And while looking for their in- 
 fluence over one insect outbreak we stumbled upon at least two 
 others, less marked, perhaps incipient, but evident enough to 
 express themselves clearly in the changed food ratios of the 
 birds. 
 
 " 2. The comparisons made show plainly that the reflex effect 
 of this concentration on two or three unusually numerous in- 
 sects was so widely distributed over the ordinary elements of 
 their food that no especial chance was given for the rise of new 
 fluctuations among the species commonly eaten. That is to 
 say, the abnormal pressure put upon the canker-worm and vine- 
 
. INSECTS IN RELATION TO OTHER ANIMALS 29 1 
 
 chafer was compensated by a general diminution of the ratios 
 of all the other elements, and not by a neglect of one or two 
 alone. If the latter had been the case, the criticism might 
 easily have been made that the birds, in helping to reduce one 
 oscillation, were setting cithers on foot. 
 
 " 3. The fact that, with the exception of the indigo bird, the 
 species whose records in the orchard were compared with those 
 made elsewhere, had eaten in the former situation as many 
 caterpillars other than canker-worms as usual, simply adding 
 their canker-worm ratios to those of other caterpillars, goes 
 to show that these insects are favorites with a majority of 
 birds."' 
 
 The Relations of Birds to Predaceous and Parasitic In- 
 sects. — The false assumption is often made that a bird is 
 necessarily inimical to man's interest whenever it destroys a 
 parasitic or a predaceous insect. Weed and Dearborn attack 
 this assumption as follows : 
 
 " Suppose an ichneumon parasite is found in the stomach of 
 a robin or other bird : it may belong to any one of the follow- 
 ing categories : 
 
 " I. The primary parasite of an injurious insect. 
 
 " 2. The secondary parasite of an injurious insect. 
 
 " 3. The primary parasite of an insect feeding on a noxious 
 plant. 
 
 " 4. The secondarv parasite of an insect feeding on a nox- 
 ious plant. 
 
 '' 5. The primary parasite of an insect feeding on a wild 
 plant of no economic value. 
 
 " 6. The secondary parasite of an insect feeding on a wild 
 plant of no economic value. 
 
 "" 7. The primary parasite of a predaceous insect. 
 
 " 8. The primary parasite of a spider or a spider's egg. 
 
 " This list might easily be extended still farther, and the 
 assumption that the parasite belongs to the first of these cate- 
 gories is unwarranted by the facts and does violence to the 
 probabilities of the case. 
 
292 ENTOMOLOGY 
 
 " A correct idea of the economic role of the feathered tribes 
 may be obtained only by a broader view of nature's methods, 
 — a view in which we must ever keep before the mind's eye 
 the fact that all the parts of the organic world, from monad to 
 man, are linked together in a thousand ways, the net result 
 being that unstable equilibrium commonly called ' the balance 
 of nature.' " 
 
 This broader view was first elaborated by Professor Forbes, 
 in his masterly paper, " On Some Interactions of Organisms," 
 the substance of wdiich is given below. 
 
 " Evidently a species can not long maintain itself in num- 
 bers greater than can find sufficient food, year after year. If 
 it is a phytophagous insect, for example, it will soon dwindle 
 if it seriously lessens the numbers of the plants upon which it 
 feeds, either directly, by eating them up, or indirectly, by so 
 weakening them that they labor under a marked disadvantage 
 in the struggle with other plants for foothold, air, light and 
 food. The interest of the insect is therefore identical with 
 the interest of the plant it feeds upon. Whatever injuriously 
 affects the latter, equally injures the former; and whatever 
 favors the latter, equally favors the former. This must, 
 therefore, be regarded as the extreme normal limit of the num- 
 bers of a phytophagous species, — a limit such that its depre- 
 dations shall do no especial harm to the plants upon which it 
 depends for food, but shall remove only the excess of foliage 
 or fruit, or else superfluous individuals which must perish 
 otherwise, if not eaten, or, surviving, must injure their species 
 by over-crowding. If the plant-feeder multiply beyond the 
 above limit, evidently the diminution of its food supply will 
 soon react to diminish its own numbers ; a counter reaction 
 will then take place in favor of the plant, and so on through 
 an oscillation of indefinite continuance. 
 
 " On the other hand, the reduction of the phytophagous in- 
 sect below the normal number, will evidently injure the food 
 plant by preventing a reduction of its excess of growth or 
 numbers, and will also set up an oscillation like the preceding, 
 except that the steps will be taken in reverse order. 
 
INSECTS IN RELATION TO OTHER ANIMALS 293 
 
 " I next point ont the fact that precisely the same reasoning 
 appHes to predaceons and parasitic insects. Tlieir interests, 
 also are identical with the interests of the species they para- 
 sitize or prey upon. A diniinntion of their food reacts to de- 
 crease their own numbers. The}- are thus vitally interested 
 in confining- their depredations to the excess of individuals 
 produced, or to redundant or otherwise unessential structures. 
 It is only by a sort of unlucky accident that a destructive spe- 
 cies really injures the species preyed upon. 
 
 " The discussion has thus far affected only such organisms 
 as are confined to a single species. It remains to see how it 
 applies to such as have several sources of support open to 
 them, — such, for instance, as feed indifferently upon several 
 plants or upon a variety of animals, or both. Let us take, 
 first, the case of a predaceous beetle feeding upon a variety of 
 other insects. — either indifferently, upon whatever species is 
 most numerous or most accessible, or preferably upon certain 
 species, resorting to others only in case of an insufficiency of 
 its favorite food. 
 
 " It is at once evident that, taking the group of its food- 
 insects as a unit, the same reasoning applies as if it were re- 
 stricted to a single species for food ; that is, it is interested in 
 the maintenance of these food-species at the highest number 
 consistent with the general conditions of the environment, — 
 interested to confine its own depredations to that surplus of 
 its food which would otherwise perish if not eaten — interested, 
 therefore, in establishing a rate of reproduction for itself 
 which will not unduly lessen its food supply. Its interest in 
 the numbers of each species of the group it eats will evidently 
 be the same as its interest in the group as a whole, since 
 the group as a whole can be kept at the highest number 
 possible only by keeping each species at the highest number 
 possible. . . . 
 
 " This argument holds for birds as well as for insects, for 
 animals of all kinds, in fact, whether their food be mixed or 
 simple, animal or vegetable, or both. It also applies to para- 
 
294 ENTOMOLOGY 
 
 sitic plants. The ideal adjustment is one in which the repro- 
 ductive rate of each species should be so exactly adapted to its 
 food supply and to the various drains upon it that the species 
 preyed upon should normally produce an excess sufficient for 
 the species it supports. And this statement evidently applies 
 throughout the entire scale of being. Among all orders of 
 plants and animals, the ideal balance of Nature is one promo- 
 tive of the highest good of all the species. In this ideal state, 
 towards which Nature seems continually striving, every food- 
 producing species of plant or. animal would grow and multiply 
 at a rate sufficient to furnish the required amount of food, 
 and every depredating species w-ould reproduce at a rate no 
 higher than just sufficient to appropriate the food thus fur- 
 nished. . . . 
 
 " Exact adjustment is doubtless never reached anywhere, 
 even for a single year. It is usually closely approached in 
 primitive nature, but the chances are practically infinite against 
 its becoming really complete, and mal-adjustment in some de- 
 gree is therefore the general rule. All species must oscillate 
 more or less." 
 
 Professor Forbes then shows that oscillations are injurious 
 to a species and that the tendency of things is toward a 
 healthy ecjuilibrium. If the rate of reproduction, as in a 
 parasite for instance, is too small in relation to the food sup- 
 ply, the species will eventually yield to its more prolific compet- 
 itors in the general struggle for existence. If, on the other 
 hand, its rate of multiplication is too high, the species will be 
 at a disadvantage in the search for food, as compared with 
 better adjusted species, and must again suffer. " The fact of 
 survival is therefore usually sufficient evidence of a fairly com- 
 plete adjustment of the rate of reproduction to the drains upon 
 the species." ... " We may be sure, therefore, that, as a 
 general rule, in the course of evolution, only those species 
 have been able to survive whose parasites, if any, were not 
 prolific enough sensibly to limit the numbers of their hosts for 
 any length of time. 
 
INSECTS IN RELATION TO OTHER ANIMALS 295 
 
 " We notice incidentally that it is thus made unlikely that an 
 injurious species can be exterminated, can even be permanently 
 lessened in numbers, by a parasite strictly dependent upon it, — 
 a conclusion which remarkably diminishes the economical role 
 of parasitism. The same line of argimient will, of course, 
 apply, with slight modifications, to any animal, or even to any 
 plant dependent upon any other animal or any other plant for 
 existence. 
 
 " It is a general truth, that those animals and plants are 
 least likely to oscillate widely which are preyed upon by the 
 greatest number of species, of the most varied habit. Then 
 the occasional diminution of a single enemy will not greatly 
 affect them, as any consequent excess of their own numbers 
 will be largely cut down by their other enemies, and especially 
 as, in most cases, the backward oscillations of one set of ene- 
 mies will be neutralized by the forward oscillations of another 
 set. But by the operations of natural selection, most animals 
 are compelled to maintain a varied food habit, — so that if one 
 element fails, others may be available. Thus each species 
 preyed upon is likely to have a number of enemies, which will 
 assist each other in keeping it properly in check. 
 
 " Against the uprising of inordinate numbers of insects, 
 commonly harmless but capable of becoming temporarily in- 
 jurious, the most valuable and reliable protection is un- 
 doubtedly afforded by those predaceous birds and insects 
 which eat a mixed food, so that in the absence or diminution 
 of any one element of their food, their own numbers are not 
 seriously affected. Resorting, then, to other food supplies, 
 they are found ready, on occasion, for immediate and over- 
 whelming attack against any threatening foe. Especially 
 does the wonderful locomotive power of birds, enabling them 
 to escape scarcity in one region which might otherwise deci- 
 mate them, by simply passing to another more favorable one, 
 without the loss of a life, fit them, above all other animals and 
 agencies, to arrest disorder at the start, — to head off aspiring 
 and destructive rebellion before it has had time fairlv to make 
 
296 ENTOMOLOGY 
 
 head. But we should not therefrom derive the general, but 
 false and mischievous notion, that the indefinite multiplication 
 of either birds or predaceous insects is good. Too many of 
 either is nearly or quite as harmful as too few. 
 
 " There is a general consent that primeval nature, as in the 
 uninhabited forest or the untilled plain, presents a settled har- 
 mony of interaction among organic groups which is in strong 
 contrast with the many serious mal-adjustments of plants and 
 animals found in countries occupied by man. 
 
 " To man, as to nature at large, the question of adjustment 
 is of vast importance, since the eminently destructive species 
 are the widely oscillating ones. Those insects which are well 
 adjusted to their environments, organic and inorganic, are 
 either harmless or inflict but moderate injury (our ordinary 
 crickets and grasshoppers are examples) ; while those that are 
 imperfectly adjusted, whose numbers are, therefore, subject 
 to wide fluctuations, like the Colorado grasshopper, the 
 chinch-bug and the army worm, are the enemies which we 
 have reason to dread. Man should then especially address 
 his efforts, first, to prevent any unnecessary disturbance of the 
 settled order of the life of his region which will convert rela- 
 tively stationary species into widely oscillating ones ; second, 
 to destroy or render stationary all the oscillating species in- 
 jurious to him ; or, failing in this, to restrict their oscillations 
 within the narrowest limits possible. 
 
 " For example, remembering that every species oscillates to 
 some extent, and is held to relatively constant numbers by the 
 joint action of several restraining forces, we. see that the re- 
 moval or weakening of any check or barrier is sufficient to 
 widen and intensify this dangerous oscillation ; may even con- 
 vert a perfectly harmless species into a frightful pest. Wit- 
 ness the maple bark louse, which is so rare in natural forests 
 as scarcely ever to be seen, limited there as it is by its feeble 
 locomotive power and the scattered situation of the trees it 
 infests. With the multiplication and concentration of its food 
 in towns, it has increased enormously, and, if it has not done 
 
INSECTS IN RELATION TO OTHER ANIMALS 297 
 
 the g-ravest injury, it is because the trees attacked by it are of 
 comparatively sb'ght economical value, and because it has 
 finally reached new limits which hem it in once more. 
 
 " We are therefore sure that the destruction of any species 
 of insectivorous bird or predaceous insect, is a thing- to be 
 done, if at all, only after the fullest acquaintance with the facts. 
 The natural presumptions arc nearly all in their favor. It is 
 also certain that the species best worth preserving" are the 
 mixed feeders and not those of narrowly restricted dietary 
 (parasites, for instance), — that while the destruction of the 
 latter would cause injurious oscillations in the species affected 
 by them, they afford a very uncertain safeguard against the 
 rise of such oscillations. In fact, their undue increase would 
 be finally as dangerous as their diminution. 
 
 " Notwithstanding the strong presumption in favor of the 
 natural system, when we remember that the purposes of man 
 and what, for convenience' sake, we may call the purposes of 
 Nature do not fully harmonize, we find it incredible that, act- 
 ing intelligently, we should not be able to modify existing ar- 
 rangements to our advantage, — especially since much of the 
 progress of the race is due to such modifications made in the 
 past. . . . 
 
 "■ But far the most important general conclusion we have 
 reached is a conviction of the general beneficence of nature, a 
 profound respect for the natural order, a belief that the part 
 of wisdom is essentially that of practical conservatism in deal- 
 ing with the system of things by which we are surrounded." 
 
 Efficiency of Protective Adaptations of Insects. — Inter- 
 esting from a scientific point of view are the various adaptations 
 by means of which insects are protected more or less from 
 their bird enemies. Colorational adaptations having been dis- 
 cussed in another chapter, there remain for consideration — 
 (i) hairs, (2) stings. (3) odors, flavors and irritants. Most 
 of what follows is from an admirable paper by Dr. Judd, 
 whose data are based upon his examination of the stomach 
 contents of fifteen thousand birds. 
 
298 ENTOMOLOGY 
 
 Hairs. — '' Excepting two species of cuckoos, no species of 
 bird in the eastern United States, so far as I am aware, makes 
 a business of feeding upon hairy caterpillars." Judd observed 
 that Hyphantria cunea infesting a pear tree was not at all 
 molested, in spite of the fact that the tree was tenanted by 
 three broods of birds at the time, namely, kingbirds, orchard 
 orioles and English sparrows. The hairy arctiid caterpillars, 
 however, are eaten by a few birds : the robin, bluebird, catbird, 
 sparro\\--hawk, cuckoos and shrikes ; and the spiny larvae of 
 Vanessa antiopa by cuckoos and the Baltimore oriole; while the 
 hairy caterpillars of the gypsy moth are known to be eaten in 
 Massachusetts by no less than thirty-one species of birds, 
 notably cuckoos, Baltimore oriole, catbird, chickadee, blue-jay, 
 chipping sparrow, robin, vireos and the crow, these birds be- 
 ing of no little assistance in the suppression of this pest. 
 These are exceptional cases, however, and in general the hairi- 
 ness of caterpillars appears to be a highly effective protection 
 against most birds. 
 
 Stings. — Some birds (chewink, young ducks) are fatally 
 affected by eating honey bees. The blue- jays, however, will 
 eat Bombiis and Xylocopa, and flycatchers and swallows feed 
 habitually upon stinging Hymenoptera, particularly Scoliidse, 
 wdiile a great many birds eat Myrmicidae, or stinging ants. 
 The formic acid of ants does not protect them from wholesale 
 destruction by birds ; Judd found three thousand ants in the 
 stomach of a flicker. " Stingless ants pretend to sting but 
 many birds they do not deceive." The stinging caterpillar of 
 Autoincris io is occasionally eaten by the yellow-billed cuckoo. 
 Aside from these exceptions, however, the stings of insects are 
 an extremely efficient means of defence. 
 
 Odors, Flavors and Irritants. — The malodorous Heterop- 
 tera in general are food for most birds ; Lygiis, Reduviid^e and 
 Pentatomidae are eaten by song sparrows, and Euschisfus by 
 blackbirds and crows. The odors of Heteroptera are by no 
 means universally protective. 
 
 Among Coleoptera, the showy, ill-scented or ill-flavored 
 
INSECTS IN RELATION TO OTHER ANIMALS 299 
 
 CoccinellicLx are eaten by but very few birds — the flvcatcliers 
 and swallows — and are refused by caged blue-jays and song 
 sparrows even when these birds are hungry. Of Chrysomel- 
 id?e, the Colorado potato beetle is refused by the catbird, blue- 
 jay and song sparrow, and Diabrotica is not often eaten, ex- 
 cept by catbirds and thrushes. " The smaller Carabidae, 
 whether stinking or not, are eaten by practically all land birds." 
 Crows, blackbirds and jays eagerly swallow Calosouia scruta- 
 tor, and the first two birds are especially fond of Harpalus 
 caliginosus and H. pcnnsylvaniciis, and feed Galcrita to their 
 young. " A score of smaller Carabidse and Chrysomelidse, 
 metallic and conspicuously colored, are habitually eaten by 
 birds that have an abundance of other insect food to pick 
 from." 
 
 The stenches of Lampyridse appear to be more effective 
 than those of Carabida;. Tclephoriis is occasionally eaten, but 
 Photimis rarely if at all. Chaiiliognatlms is not eaten by 
 many birds (though flycatchers and swallows select this in- 
 sect) and the genus is regarded unfavorably by caged catbirds 
 and blue-jays. 
 
 In regard to other insects, Judd finds that Epicauta, with its 
 irritant fluid, is immune from all but the kingbird; Cyllene 
 seldom occurs in the stomachs of birds ; May flies and caddis 
 flies, however, are terribly persecuted, but swiftly flying Dip- 
 tera and Odonata are highly immune. 
 
 From such facts as these, Judd properly infers, " not cases 
 of protection and non-protection, but cases of greater and 
 lesser et^ciency of protective devices." 
 
 2. The Transmission of Diseases by Insects. 
 
 It is now known that several kinds of insects are of vital 
 importance to man as agents in the transmission of certain 
 diseases. This recently demonstrated role of insects now 
 commands universal attention. 
 
 Malaria.- — So far as is known, malaria is transmissible 
 only through the agency of mosquitoes. 
 
300 
 
 ENTOMOLOGY 
 Fig. 269. 
 
 
 Life history of malaria parasite, Plasmodium pracox. i, sporozoite, introduced by- 
 mosquito into human blood; the sporozoite becomes a schizont. 2, young schizont, 
 which enters a red blood corpuscle. s> young schizont in a red blood corpuscle. 4, 
 full-grown schizont, containing numerous granules of melanin. 5, nuclear division 
 preparatory to sporulation. 6, spores, or merozoites, derived from a single mother- 
 cell, y, young macrogamete (.female), derived from a merozoite and situated in a 
 red blood corpuscle. 7a, young microgametoblast (.male), derived from a merozoite. 
 
 8, full-grown macrogamete. Sa, full-grown microgametoblast. In stages S and 8a the 
 parasite is taken into the stomach of a mosquito; or else remains in the human blood. 
 
 9, mature macrogamete, capable of fertilization; the round black extruded object may 
 probably be termed a " polar body." 9a, mature microgametoblast, preparatory to 
 
INSECTS IN RELATION TO OTHER ANIMALS 3OI 
 
 1"hc malaria "germ," discoxercd in iS8o by tlie French 
 army surgeon Laveran. may 1)C found as a pale. auKjeboid 
 organism (PlasiiKn^iinn, Fig. 269) in the red blood corpus- 
 cles of persons aillicted with the disease. This organism 
 {Silil::::'iif, J) grows at the expense of the h;emoglol)in of the 
 corpuscle (SS) and its growth is accompanied by an increasing 
 deposit of black granules (inelatiin) , which are doubtless 
 excretory in their nature. At length, the amoebula divides 
 into many spores ( iiicro::;('itcs, 6), which by the disintegration 
 of the corpuscle are set free in the plasma of the blood. Here 
 many if not most of the spores, and the pigment granules as 
 well, are attacked and absorbed by leucocytes, or white blood 
 corpuscles, while some of the spores may invade healthy red 
 corpuscles and develop as before. The period of sporulation, 
 as Golgi found, is coincident with that of the " chill " experi- 
 enced by the patient; and quinine is most effective when ad- 
 ministered just before the sporulation period. The destruc- 
 tion of red blood corpuscles explains the pallid, or ancvmic, 
 condition which is characteristic of malarial patients. In 
 three or four days the number of red corpuscles may be re- 
 duced from 5,000,000 per cubic millimeter — the normal num- 
 ber — to 3,000,000; and in three or four weeks of intermittent 
 fever, even to 1,000,000. 
 
 Three types of malaria are recognized: (i) the tertian, in 
 which the paroxysm recurs every two days; (2) the quartan, 
 in which it happens every third day; and (3) the asstivo- 
 autumnal type (Fig. 269). These three kinds are by some 
 
 forming microgametes. pb, resting cell, bearing six flagellate microgametes (male). 
 10, fertilization of a macrogamete by a motile microgamete. The macrogamete next 
 becomes an ookinete. //, ookinete, or wandering cell, which penetrates into the wall 
 of the stomach of the mosquito. 12, ookinete in the outer region of the wall of the 
 stomach, i. e., next to the body cavity. /,•;, young oocyst, derived from the ookinete. 
 14, oocyst, containing sporoblasts, which are to develop into sporozoites. 15, older 
 oocyst. 16, mature oocyst, containing sporozoites, which are liberated into the body 
 cavity of the mosquito and carried along in the blood of the insect. 17, transverse 
 section of salivary gland of an Anopheles mosquito, showing sporozoites of the malaria 
 parasite in the gland cells surrounding the central canal. 
 
 1-6 illustrate schi::ogony (asexual production of spores) ; 7-/6, sporogony (sexual 
 production of spores). 
 
 After Grassi and Leuckart, by permission of Dr. Carl Chun. 
 
302 ENTOMOLOGY 
 
 investigators thought to be due to different species of para- 
 sites; and when, as often happens, the malarial chill occurs 
 every day, this is attributed to two sets of tertian amcebulse, 
 sporulating on alternate days. 
 
 After several successive asexual generations, there are pro- 
 duced merozoites which develop — no longer into schizonts — 
 but into sexual forms, or gametes. These occur in red 
 blood corpuscles either as macrogametes (female, 7, 8) or as 
 micro gametoblasts (male, ya, 8a), in which forms the parasite 
 is introduced into the stomach of a mosquito which has been 
 feeding upon the blood of a malarial patient. The macro- 
 gamete now leaves its blood corpuscle and becomes spherical 
 (p), as does also the microgametoblast (pa) ; but the latter puts 
 forth a definite number {six, in P. prcucox, pb) of flagella, 
 or micro gametes, which separate off as motile male bodies, 
 capable of fertilizing the macrogametes. A microgamete 
 penetrates a macrogamete (10) and the nucleus of the one 
 unites with that of the other. The fertilized macrogamete now 
 becomes a migrating cell, or ookinete (ii), which penetrates 
 almost through the wall of the stomach of the mosquito (12) 
 and then becomes a resting cell, or cyst. This oocyst (ij) 
 grows rapidly and its contents develop, by direct nuclear divis- 
 ion, into sporoblasts {14, ij), which differentiate into spindle- 
 shaped sporozoites (16, i). The sporozoites are liberated into 
 the body cavity of the mosquito, carried in the blood to the sali- 
 vary glands (as well as elsewhere) and thence along the hypo- 
 pharynx into the body of a human being, bird or other animal 
 attacked by the insect. 
 
 The role of the mosquito as the intermediary host of mala- 
 rial organisms was discovered by Manson and Ross and con- 
 firmed by Koch, Sternberg and others. It has been found 
 repeatedly that certain mosquitoes (Anopheles) after feeding 
 on the blood of a malarial patient can transmit the disease by 
 means of their " bites " to healthy persons. Thus, Anopheles 
 mosquitoes were fed on the blood of malarial subjects in Rome 
 and then sent to London, where a son of Dr. Alanson allowed 
 
INSECTS IN RELATION TO OTHER ANIMALS 3O3 
 
 himself to be bitten by the insects. Thoug-h previously free 
 from the malarial org-anism. he contracted a well-marked 
 infection as the result of the inoculation. 
 
 Furthermore, it is hig-hly probable that malaria cannot be 
 transmitted to man except throug-h the agency of the mos- 
 quito. This appears from the oft-cited exi)eriment of Doc- 
 tors Sambon and Low on the Roman Campag-na, a place 
 notorious for malaria. There the experimenters lived during 
 the malarial season of 1900, freely exposed to the emanations 
 of the marsh and taking- no precautions except to screen 
 their house carefully against mosquitoes and to retire indoors 
 before the insects appeared in the evening. Simply by ex- 
 cluding Anopheles mosquitoes, with which the Campagna 
 swarmed, these investigators remained perfectly immune from 
 the malaria which was ravaging the vicinity. 
 
 In a later experiment on the island of Formosa, one com- 
 pany of Japanese soldiers was protected from mosquitoes and 
 suffered no malaria, while a second and unprotected company 
 contracted the disease. 
 
 The evident preventive measures to be taken against ma- 
 laria are ( i ) the avoidance of mosquito bites, by means of 
 screens, and washes of eucalyptus oil, camphor, oil of penny- 
 royal, oil of tar, etc., applied to exposed parts of the body; 
 (2) the isolation of malarial patients from mosquitoes, in 
 order to prevent infection; (3) the destruction of mosquitoes 
 in their breeding places, especially by the use of kerosene and 
 by drainage. During unavoidable exposure in malarious 
 regions, quinine should be taken in doses of six to ten grains 
 during the day at intervals of four or five days (Sternberg). 
 
 Culex and Anopheles. — The mosquitoes of North America 
 number one hundred and twenty-five known species. Of these 
 only the genus Anopheles transmits malaria to man. though in 
 India, Ross found that Culex transmits a form of malaria to 
 sparrows. These two common genera are easily distinguish- 
 able. In Culex the wings are clear; in Anopheles they are 
 spotted with brown. In Culex when resting, the axis of the 
 
304 ENTOMOLOGY 
 
 body forms a curved line, the insect presenting a luimp-backed 
 appearance; in Anopheles the axis forms a straight Hne. 
 Culex has short maxillary palpi, while in Anopheles they are 
 almost as long as the proboscis. The note of the female 
 Anopheles is several tones lower than that of Culex, and only 
 the female is bloodthirsty, by the way. As regards eggs, 
 larvae and pupae, the two genera differ greatly. The eggs of 
 Culex are laid in a mass and those of Anopheles singly; the 
 larvae of Culex hang from the surface film of a pool at an 
 angle of about forty-five degrees, while those of Anopheles 
 are almost parallel with the surface of the water in which 
 they live. 
 
 The bite of an Anopheles is not necessarily injurious, of 
 course, unless the insect has had recent access to a malarious 
 person. Anopheles may be present where there is no malaria. 
 On the other hand, it has been found impossible to prove that 
 malaria exists where there are no Anopheles mosquitoes. 
 Finally, fevers are sometimes diagnosed as malarial which are 
 not so. 
 
 Possibly the malarial parasite can complete its cycle of 
 development in other animals than man. It is also possible 
 that originally the malarial organism was derived by mos- 
 quitoes from the stems or other parts of aquatic plants, and 
 that its effects on man are incidental phenomena. 
 
 Yellow Fever. — It has now been demonstrated that the 
 dreaded disease, yellow fever, is transmitted from one human 
 being to another by the bite of a mosciuito (Stegoniyia fas- 
 ciata) and in no other way excepting, of course, by the arti- 
 ficial injection of diseased blood. The discovery of the mode 
 of transmission of the disease was made in Cuba during 1900 
 and 1902 by Dr. Reed and his corps of United States army sur- 
 geons. These investigators succeeded in transmitting the dis- 
 ease to healthy subjects by inoculation from mosquitoes which 
 had previously fed on the blood of yellow fever patients. To 
 convey the disease, however, a period of ten to thirteen 
 days was necessary between the original biting of a patient 
 
INSECTS IN RELATION TO OTHER ANIMALS 3O5 
 
 and the inoculation of a healthy subject. The disease fol- 
 lowed the l)ite of an infected Stci^oiiiyia with remarkable 
 precision. 
 
 Furthermore, Dr. Reed and his associates found that yel- 
 low fever could not be conveyed by means of the clothing, 
 bedding, etc., of fever patients, so long as mosquitoes were 
 excluded. In the absence of the mosquito the yellow fever 
 patient is harmless and in the absence of a patient the mos- 
 quito is harmless (Sternberg). The disease terminates in 
 cold weather with the disappearance of the mosquito. 
 
 Preventive measures based upon these recently acquired 
 facts have been wonderfully successful. The city of Havana, 
 in which yellow fever had always prevailed, has now been 
 freed of the disease. 
 
 The specific cause of yellow fever has as yet eluded detec- 
 tion in the human body. There has been discovered, how- 
 ever, in the stomach and salivary glands of mosquitoes in- 
 fected with yellow fever, a protozoan parasite (order Coc- 
 cidiida), the sexual cycle of wdiich, ending in the development 
 of sporozoites, has been traced in the body of the Stcgomyia. 
 This coccidium may or may not prove to be concerned in the 
 transmission of the disease. 
 
 Other Diseases. — Typhoid fever is transmitted frequently 
 by the common house fly, which may carry the bacillus from 
 the excreta of typhoid patients to food supplies in kitchens or 
 elsewhere. The spread of the disease in army camps is due 
 chiefly to the house fly {Miisca doniestica) , as was demon- 
 strated in 1898 by a commission of the United States army. 
 
 The dreaded disease filariasis (elephantiasis) of Oriental 
 tropical regions is transmitted by mosquitoes of the genus 
 Culex, as Dr. Manson discovered many years ago. The dis- 
 ease is due to a parasitic worm (Filaria) , both sexes of which 
 lodge in the lymphatic vessels, obstruct the flow of the lymph 
 and thereby cause an abnormal enlargement of the parts in 
 which they occur. The embryos of the parasite pass into the 
 blood and thence into the body of the mosquito ; there they 
 
306 ENTOMOLOGY 
 
 remain in the thoracic muscles for a time and become larvae, 
 which at length pass through the proboscis of the mosquito 
 into the skin of man. It is possible, though not proved, that 
 other mosquitoes than Cnlex and indeed other kinds of insects 
 are involved in the transmission of filariasis. 
 
 In Egypt, an eye disease is transmitted by the house fly. 
 There is some evidence that the bubonic plague is spread 
 through the agency of fleas. Anthrax of cattle is carried by 
 gad flies (Tabanidse). A South African disease fatal to 
 horses, cattle and dogs, though not to man, is transmitted 
 from infected to healthy animals by the proboscis of a muscid 
 fly, Glossina morsitans, as has been mentioned. The specific 
 cause of this disease is a blood parasite similar to that of 
 malaria. Finally, the destructive Texas fever of cattle is 
 undoubtedly transmitted by the common cattle-tick, as was 
 discovered by Theobald Smith, though the tick is not, properly 
 speaking, an insect. 
 
CHAPTER X 
 
 INTERRELATIONS OF INSECTS 
 
 Fig. 270. 
 
 Insects in general are adapted to utilize all kinds of organic 
 matter as food, and they show all gradations of habit from 
 herl)ivorons to carni\-orons. The many forms that derive 
 their food from the bodies of other insects may conveniently 
 be classed as predaceons or parasitic. 
 
 Predaceous Insects. — Among Orthoptera, Mantidse are 
 nota1)ly predatory, their front legs (Fig. 62, C) being well 
 fitted for grasping and killing other insects. The predaceous 
 odonate nymphs have a peculiar 
 hinged extensible labium Avith 
 which to gather in the prey. The 
 adults catch with surpassing 
 speed and precision a gTeat va- 
 riety of flying insects, mostly 
 small forms, but occasionally but- 
 terflies of considerable size. The 
 eyes of a dragon fly are remark- 
 ably large ; the legs form a spiny 
 basket, probably to catch the prey, 
 which is instantly stripped and 
 devoured, these operations being 
 facilitated by the excessive mobil- 
 ity of the head. The hemipter- 
 ous families Corixidse, Notonect- 
 id?e (Fig. 224). Nepidse, Belos- 
 
 tomid?e (Fig. 22), Naucoridae (Fig. 62, D), Reduviidae and 
 Phymatidje are predaceous, with raptorial front legs and sharp 
 beaks. Some of the Pentatomidse (Fig. 270) are of con- 
 siderable economic value on account of their predaceous 
 habits. Most of the Xeuroptera feed upon other insects. 
 
 307 
 
 Nymph of Podisiis spiitosus suck- 
 ing the blood from a clover cater- 
 pillar, Colias philodice. Natural 
 size. 
 
308 ENTOMOLOGY 
 
 The My nucleoli larva digs a funnel-shaped pitfall, at the bot- 
 tom of which it bnries itself to await the fall of some unlucky 
 ant. The Chrysopa larva impales an aphid on the points of 
 its mandibles and sucks the blood through a groove along 
 each mandible (Fig. 45, E), the maxilla fitting against this 
 groove to form a closed channel. Several families of Coleop- 
 tera are almost entirely predaceous. Among aquatic beetles, 
 Dytiscidae are carnivorous both as larv?e and imagines, Gyrin- 
 idse subsist chiefly upon disabled insects, but occasionally eat 
 plant substances, and Hydrophilid^e as larvae catch and devour 
 other insects, though some of the beetles of this family {H. 
 triangularis, for example, Fig. 226) feed largely if not en- 
 tirely upon vegetation. Of terrestrial Coleoptera, the tiger 
 beetles (Cicindelidje) are strictly predaceous upon other insects. 
 The Cicindcla larva lives in a burrow in the soil and lies in 
 wait for passing insects ; a pair of hooks on the fifth segment 
 of the abdomen serves to prevent the larva from being jerked 
 out of its burrow by the struggles of its captive. The large 
 family Carabidae is chiefly predaceous ; these " running 
 beetles " both as larvee and adults easily overtake and capture 
 other terrestrial insects. The Carabid^e, however, are by no 
 means exclusively carnivorous, for many of them feed to some 
 extent upon fungus spores, pollen, ovules, root-tips and other 
 vegetable matter, as Forbes has found; Harpalus caliginosus 
 eats the pollen of the ragweed in autumn ; Galerita janiis eats 
 caterpillars and occasionally the seeds of grasses; Calosoma, 
 however, appears to be strictly carnivorous, feeding chiefly 
 upon caterpillars and being in this respect of considerable eco- 
 nomic importance. As a whole, Carabidse prefer animal food, 
 as appears from the fact that when canker worms, for in- 
 stance, are unusually abundant they form a correspondingly 
 large percentage of carabid food, the increase being compen- 
 sated by a diminution in the amount of vegetable food taken 
 (Forbes). Coccinellid larvce (excepting Epilachna, which 
 eats leaves) feed almost entirely upon plant lice and consti- 
 tute one of the most effective checks upon their multiplication ; 
 
INTERRELATIONS OF INSECTS 3O9 
 
 the beetles eat aphides, but also fungus spores and pollen in 
 large quantities. Though Lepidoptera are pre-eminently phy- 
 tophagous, the larva of Feniscca tarqidnius is unique in feeding 
 solely upon plant lice, particularly the woolly Schiconcura tes- 
 scllata of the alder. Among Diptera, Asilida^, Midaidse, 
 Therevidse and Empidida^ are the chief predaceous families. 
 Asilidae ferociously attack not only other flies, but also beetles, 
 bumble bees, butterflies and dragon flies ; as larvae they feed 
 largely upon the larvse of beetles. Many of the larvae of 
 Syrphidse prey upon plant lice, and the larvae of Volucclla feed 
 in Europe on the larvK of bumble bees and wasps. Of 
 Hymenoptera, the ants are to a great extent predaceous, 
 attacking all sorts of insects, but particularly soft-bodied 
 kinds; while Vespidae feed largely upon other insects, though 
 like the ants, they are fond of the nectar of flowers and the 
 juices of fruits. 
 
 Parasitic Insects. — Though very many insects occur as 
 external parasites on the bodies of birds and mammals, very 
 few occur as such on the bodies of other insects ; one of the 
 few is Braula cccca, a wingless dipteron found on the body 
 of the honey bee. 
 
 A vast number of insects, however, undergo their larval 
 development as internal parasites of other insects, and most 
 of these parasites belong to the two most specialized orders, 
 Diptera and Hymenoptera. 
 
 The larvae of Bombyliidae feed upon the eggs of Orthop- 
 tera and upon larvae of Lepidoptera and Hymenoptera. 
 Tachinidae are the most important dipterous parasites of other 
 insects and lay their eggs most frequently upon caterpillars ; 
 the larvae bore into their victim, develop within its body, and 
 at length emerge as winged insects. These parasites often 
 render an important service to man in checking the increase 
 of noxious Lepidoptera. 
 
 The great majority of insect parasites — many thousand 
 species — belong to the order Hymenoptera, constituting one 
 of the primary divisions of the order. They are immensely 
 
3IO 
 
 ENTOMOLOGY 
 
 important from an economic standpoint, particularly the Ich- 
 neumonid?e, of which more than ten thousand species are al- 
 ready known. Our most conspicuous ichneumonids are the 
 two species of Thalessa, T. atrata and T. lunator (Fig. 271), 
 with their long ovipositors (three inches long in lunator, and 
 
 Fig. 271. 
 
 Oviposition of Thalessa lunator. Natural size. — After Riley. 
 
 four to four and three Cjuarters inches in atrata). Thalessa 
 bores into the trunks of trees in order to reach the burrows of 
 another large hymenopteron, Tremex coluinba (Fig. 31), upon 
 whose larvae the larva of Thalessa feeds. 
 
 The enormous family Braconidre, closely related to Ichneu- 
 monidcT, is illustrated by the common Apantcles congregatiis, 
 which lays its eggs in the caterpillars of various Sphingidae. 
 The parasitic larvae feed upon the blood and possibly also the 
 fat-body of their host, and at length emerge and spin their co- 
 coons upon the exterior of the caterpillar (Fig. 272), sometimes 
 to the number of several hundred. Species of Aphidius trans- 
 form within the bodies of plant lice, one to each host, and the 
 imago cuts its way out throug'h a circular opening with a cor- 
 respondingly circular lid. Chalcididae, of which some four 
 thousand species are know^n, are usually minute and parasitic; 
 
INTERRELATIONS OF INSECTS 
 
 311 
 
 thoiii^h some are phytophagous, for example, Isosoma hordei, 
 which Hves in the stems of grasses, especially wheat, rye and 
 harlcy. Chalcids affect a gTeat variety of insects of one stage 
 or another, such as caterpillars, pup;e. cockroach eggs, plant 
 lice and scale insects; while some of them develop in cynipid 
 galls, either upon the larvcC of the gall-makers or upon the 
 larvas of inquilines. Giard in France reared more than three 
 thousand chalcids {Copidosoma tnnicatcllinn) from a single 
 
 Fig. 272, 
 
 A tomato worm, Phlcgetltontius sc.vta, bearing cocoons of the parasitic Apantclcs con- 
 gregaius. Natural size. 
 
 caterpillar of Plusia. Proctotrypidae are remarkable as para- 
 sites. Most of them are minute ; indeed this family and the 
 coleopterous family Trichopterygidae contain the smallest 
 winged insects known — species but one third or one fourth 
 of a millimeter long. A large proportion of the Proctotry- 
 pidas are parasitic in the eggs of other insects or of spiders, 
 several sometimes developing in the same egg; others affect 
 odonate nymphs and coleopterous or dipterous larvse, while 
 several species have been reared from cecidomyiid and cynipid 
 galls, and many proctotrypids are parasites of other parasitic 
 insects — -in other words, are liyperparasitcs. 
 
3 I 2 ENTOMOLOGY 
 
 Hyperparasitism. — Not only are primary parasites fre- 
 quently attacked by other, or secondary, parasites, but tertiary 
 parasitism is known to occur in a few instances, and there is 
 some reason to believe that even the quaternary type exists 
 among insects, as in the following case. 
 
 The caterpillar of Hernerocampa (Orgyia) leucostigma 
 defoliates shade trees in the northeastern United States. An 
 enormous increase of this species in the city of Washington in 
 1895 was attended by a corresponding increase of parasitic 
 and predaceous species, and this unusual opportunity for the 
 study of parasitism was made the most of by Dr. Howard, 
 from whose admirable paper these facts are taken. 
 
 The primary parasites of H. leucostigma numbered 23 spe- 
 cies — 17 Hymenoptera and 6 Diptera; of the hyperparasites 
 (all hymenopterous) 13 were secondary, 2 and probably 5 
 were tertiary, and one of these (Asecodes albitarsis) may un- 
 der certain conditions prove to be a quaternary parasite. To 
 illustrate — The ichneumon Piuipla inquisitor, an important 
 primary parasite of lepidopterous larvae, lays its eggs in cater- 
 pillars of H. leucostigma; its larvae suck the blood of their 
 host and at length spin their cocoons within the loose cocoon 
 of the Henicrocanipa. These cocoons have yielded a well- 
 known secondary parasite, the chalcid Dibrachys bouchcanus. 
 Now another chalcid, Asecodes albitarsis, has been seen to issue 
 from a pupa of this Dibrachys, thus establishing tertiary para- 
 sitism. Furthermore, it is quite possible that Dibrachys itself 
 is a tertiary parasite, in which event the Asecodes might be- 
 come a parasite of the quaternary order. 
 
 Economic Importance of Parasitism. — If a primary para- 
 site is beneficial, its own parasites are indirectly injurious, gen- 
 erally speaking; while those of the third and the fourth order 
 are respectively beneficial and injurious. The last two kinds 
 are so rare, however, as to be of no practical importance from 
 an economic standpoint. The first- two kinds are of immense 
 economic importance, particularly the primary parasites. 
 " Outbreaks of injurious insects," says Howard, " are fre- 
 
INTERRELATIONS OF INSECTS 3 13 
 
 qiiently stopped as thout^li by magic l)y the work of insect ene- 
 mies of the species. llnl)bard found, in icSSo, that a minute 
 parasite, Trichograiiiiiia prctiosa, alone and unaided, ahnost 
 annihilated the fifth brood of the cotton worm in Morida, fully 
 ninety per cent, of the eggs of this prolific crop enemy being 
 infested by the parasite. Not longer ago than 1895, in the 
 city of Washington, more than ninety-seven per cent, of the 
 caterpillars of one of our most important shade-tree pests 
 [Orgyia, as just mentioned] were destroyed by parasitic in- 
 sects, to the complete relief of the city the following year. 
 The Hessian fly, that destructive enemy to wheat crops in the 
 United States, is practically unconsidered by the wheat grow- 
 ers of certain states, for the reason that wdienever its numbers 
 begin to be injuriously great its parasites increase to such a 
 degree as to prevent appreciable damage. 
 
 " The control of a plant-feeding insect by its insect enemies 
 in an extremely complicated matter, since, as we have already 
 hinted, the parasites of the parasites play an important part. 
 The undue multiplication of a vegetable feeder is followed by 
 the undue multiplication of parasites, and their increase is fol- 
 lowed by the increase of hyperparasites. Following the very 
 instance of the multiplication of the shade-tree caterpillar just 
 mentioned, the writer [Howard] was able to determine this 
 parasitic chain during the next season down to cjuaternary 
 parasitism. Beyond this point, true internal parasitism prob- 
 ably did not exist, but even these quaternary parasites were 
 subject to bacterial or fungus disease and to the attacks of 
 predatory insects. 
 
 " The prime cause of the abundance or scarcity of a leaf- 
 feeding species is, therefore, obscure, since it is hindered by 
 an abundance of primary parasites, favored by an abundance 
 of secondary parasites (since these will destroy the primary 
 parasites), hindered again by an abundance of tertiary para- 
 sites, and favored again by an abundance of quaternary para- 
 sites." 
 
 Entomologists have made many attempts to import and 
 
314 ENTOMOLOGY 
 
 propagate insect enemies of various introduced insect pests, 
 and some of their etTorts have been crowned with success, as 
 was notably the case when Novius cardinalis, a lady-bird 
 beetle, was taken from Australia to California to destroy the 
 fluted scale. 
 
 Form of Parasitic Larvae. — The peculiar environment of 
 parasitic larvae is responsible for profound changes in their 
 organization. These larvae, in general, are apodous, the body 
 is compact and the head is more or less reduced, sometimes to 
 the merest rudiment. These characters, occurring also in such 
 dipterous larvae as live in a mass of decaying organic matter 
 and again in those hymenopterous larvae whose food is pro- 
 vided by the mother or by nurses, are to be attributed to the 
 presence of a plentiful supply of food, obtainable with little or 
 no exertion, and indicate, not primitive simplicity of organiza- 
 tion, but a high degree of specialization, as we have said before. 
 The embryonic development of parasitic larvae is frequently 
 highly anomalous, as appears in the chapter on development. 
 
 Maternal Provision. — Excepting several families of Hy- 
 menoptera and the Termitidae, few insects make any special 
 provision for the welfare of the young beyond laying the eggs 
 in some appropriate situation. Many insects, as walking- 
 sticks (Phasmidae) and May beetles {Lachnosterna) simply 
 drop their eggs to the ground, leaving the young to shift for 
 themselves. Most insects, however, instinctively lay their 
 eggs in situations where the larva is sure to find its proper food 
 near at hand. Thus various flies and beetles deposit their eggs 
 on decaying animal matter, butterflies and moths are more or 
 less restricted to particular species of plants, and parasitic 
 Hymenoptera to certain species of insects. The beetles of the 
 genus Nccrophonis go so far as to bury the body of a bird, 
 mouse or other animal in which the eggs are to be laid; and 
 in this instance the male assists the female in undermining and 
 afterward co^•ering the body. A similar co-operation of the 
 two sexes occurs in the scarabaeid beetles known as " tumble- 
 bugs," a pair of which may often be seen rolling along labori- 
 
INTERRELATIONS OF INSECTS 315 
 
 ously a ball of dung which is to serve as larval food. The 
 female mole-cricket (Gryllolalpa) is said to care for her eggs 
 and even to feed the young at first. 
 
 Hymenoptera display all degrees of complexity in regard to 
 maternal provision. Tenthredinidse simply lay their eggs on 
 the proper food plants or else insert them into the tissues of 
 the plants. Sphecina make a nest, provision it with food and 
 leave the young to care for themselves. Queen wasps and 
 • bumble bees go a step further in feeding the first larvae and 
 carrying them to maturity. Finally, in the honey bee the care 
 of the young is at once relegated by the queen to other individ- 
 uals of the colony, as is also the case among ants. 
 
 Some of the most elaborate examples of purely maternal 
 provision are found among the digger wasps and the solitary 
 wasps ; these instances are highly interesting, involving as they 
 do an intricate co-ordination of many refiex actions — as ap- 
 pears in the discussion of insect behavior. 
 
 Among the Sphecina, or digger wasps, the female makes a 
 nest by burrowing into the ground, by mining into such pithy 
 plants as elder or sumach, or else by plastering bits of mud 
 together. The nest is provisioned with insects or spiders 
 which have been stung in such a way as usually to be para- 
 lyzed, without being actually killed. The various species of 
 Sphecina frequently select particular species of insects or 
 spiders as food for the young. Pepsis formosa (Pompilidae) 
 uses tarantulas for this purpose; Splicciits speciosus (Bembe- 
 cidse) stores her nest with a cicada; Nyssonidse pick out cer- 
 tain species of Membracidoe ; mud-daubers (Sphecidcx) use 
 spiders; and other families of Sphecina capture bees, beetles, 
 plant lice or other insects, as the case may be. The solitary 
 wasps (Eumenidae) are similar to the digger wasps in habits. 
 
 Of the solitary bees, Megocliile is well known for its habit 
 of cutting pieces out of rose leaves; it uses oblong pieces to 
 form a thimble-shaped tube which, after being stored with pol- 
 len and nectar, is plugged with a circular piece of leaf. The 
 larval cells are made either in tunnels excavated in wood by 
 the mother or else in cracks or other chance cavities. 
 
3i6 
 
 ENTOMOLOGY 
 
 One of the carpenter bees, Ccratina dupla, which builds in 
 the hollow stem of a plant a series of larval cells separated by 
 partitions, is said by Comstock to watch over her nest until 
 the young mature. 
 
 The transition from the solitary to the social habit is indi- 
 cated in the life-histories of wasps and bumble bees, where a 
 solitary queen founds the colony but soon relegates to other 
 individuals all duties except that of egg-laying. The social 
 insects will now be considered. 
 
 Termites 
 Though popularly known as " white ants," the termites are 
 quite different from true ants, being indeed not very far re- 
 moved from the most primitive insects. In view of the ex- 
 treme contrast in structure and development between termites 
 and ants, it is remarkable that the two groups should have 
 much the same kind of complex social organization. 
 
 Fig. 272,. 
 
 Various forms of Terincs lucifugus. A, adult worker; B, soldier; C, perfect winged 
 insect; D, perfect insect after shedding the wings; E, young complementary queen; 
 F, older complementary queen. Enlarged. — After Grassi and Sandias. 
 
 Classes of Termites. — In general, four kinds of adults are 
 produced in a community of termites, namely — workers, sol- 
 diers, zvingcd males and unnged females. 
 
 The workers (Fig. 273, A), which are ordinarily the most 
 numerous, are of either sex, but their reproductive organs are 
 undeveloped. A worker-ant or bee, however, is always a 
 
INTERRELATIONS OF INSECTS 
 
 1^7 
 
 Fig. 
 
 female. The termite workers, as the name imphes, do most 
 of the work; they make the nest, provide food, feed and care 
 for the young and the royal pair, and attend to many other 
 domestic duties. 
 
 The soldiers, like the workers, are of either sex, with unde- 
 veloped sexual organs. With monstrous mandibles and head 
 (Fig. 273, B), their chief duty apparently 
 is to defend the colony, though they fre- 
 quently fail to do so. 
 
 The winged males and females (Fig. 
 273. C) which are sexually mature, 
 swarm from the nest and mate. After 
 the nuptial flight the pair burrow into 
 some crevice and shed the wings, which 
 break off each along a peculiar transverse 
 suture, leaving four triangular stumps 
 (Fig. 273, D). The king and queen 
 found a new colony and may live for 
 scA'cral years, sheltered in a special cham- 
 ber, the queen, meanwdiile, becoming 
 enormously distended (Fig. 274) with 
 eggs and almost incapable of locomotion. 
 The prolificacy of the queen is astonish- 
 ing; she can lay thousands of eggs, 
 sometimes at the rate of sixty per minute. 
 She is the nucleus of the colony, and 
 should she become incapacitated, is replaced by one or more 
 substitute queens, which have been developed to meet the emer- 
 gency; similarly, a substitute king is matured upon occasion. 
 These substitutes (Fig. 273, E) differ from the primary pair 
 in having nymphal wing-pads in place of the remains of func- 
 tional wings. 
 
 These six kinds are by no means all that may occur in a 
 single colony. Tennes lucifugus, according to Grassi, has no 
 less than fifteen kinds of individuals, counting nymphs in vari- 
 ous stages of development toward workers, soldiers, and pri- 
 mary or else complementary, or reserve, kings or queens. 
 
 Queen of Tcrines obc- 
 sus. Natural size. — After 
 Hagen". 
 
3l8 ENTOMOLOGY 
 
 Origin of Castes. — Grassi maintains that all the forms are 
 alike at birth except as reg-ards sex, and that the differences 
 between worker and soldier, which are independent of sex, 
 depend probably upon nutrition. Grassi attributes all the di- 
 versities of caste, except the sexual ones, to the character and 
 amount of the food. 
 
 Food. — The food of termites is of six kinds : ( i ) wood ; 
 (2) matter emitted from the oesophag-us or rectum, termed 
 respectively stomodseal and proctodfeal food; (3) cast skins 
 and other exuvial stuff; (4) the bodies of their companions; 
 (5) saliva; (6) water. Of these the proctodaeal food is the 
 favorite. Nymphs receive at first only saliva ; later they get 
 stomodseal and proctod?eal food until, finally, they are able to 
 eat wood — the staple food of a termite. 
 
 American Species. — Our common termite is Termes Uavi- 
 pes, which occurs throughout the United States, excavating 
 its galleries in decaying logs, stumps or other dead wood. The 
 nuptial flight of this species takes place in spring, when the two 
 sexes swarm in numbers that are sometimes enormous. One 
 swarm, as recorded by Hagen, appeared as a dense cloud, and 
 was being followed and attacked by no less than fifteen species 
 of birds, among which were robins, bluebirds and sparrows ; 
 some of the robins were so gorged to the mouth with termites 
 that their beaks stood open. Though plenty of winged fe- 
 males are said to occur in the swarming season, a true queen 
 of T. Havipcs is as yet unknown, the queen described by Hub- 
 bard being evidently, from her undeveloped wings, a substitu- 
 tion c[ueen. 
 
 In the Western states, six species of termites are known, in- 
 cluding Termes hieifugus, which has probably been introduced 
 from Europe. In this species the primary queen is known to 
 exist. ' Regarding the Californian Teniiopsis angusticollis, 
 Dr. Heath says that if only one of the royal pair be destroyed 
 usually only one substitution form is developed, but when both 
 perish, from ten to forty substitutes appear, according to the 
 size of the colony ; furthermore — a remarkable fact — these 
 
INTERRELATIONS OF INSECTS 
 
 319 
 
 substitution royalties may contain workers or even soldiers 
 capable of laying eggs. 
 
 Architecture. — Wbile many termites simply burrow in dead 
 wood, other species construct more elaborate nests. A Jamai- 
 can species builds huge nests in the forks of trees, with covered 
 passageways leading to the ground. 
 
 In parts of Africa and Australia, where they are free from 
 disturbance, termites erect huge mounds, frequently six to ten 
 and sometimes eighteen or twenty feet high, with galleries 
 extending as far below the 
 
 surface of the ground as " " ^' 
 
 they do above it. These im- 
 mense structures (Fig. 275) 
 consist chiefly of earth, ce- 
 mented by means of some 
 secretion into a stony clay, 
 with which also much excre- 
 mentitious matter is mixed ; 
 they are pyramidal, colum- 
 nar, pinnacled or of various 
 other forms, according to 
 the species, and are perfor- 
 ated by thousands of pass- 
 ages and chambers, while 
 there are underground gal- 
 leries extending away from 
 the mound to a distance 
 of often several hundred 
 feet. 
 
 An extraordinary type of mound is constructed by the 
 "compass," or ''meridian," termites of North Australia, for 
 their wedge-shaped mounds (Fig. 276), commonly eight or 
 ten feet high, though sometimes as high as twenty feet, are 
 directed north and south with surprising accuracy. By means 
 of this orientation the exposure to the heat of the sun is re- 
 duced to the minimum, as occurs also in the case of many Aus- 
 
 rmite mound, Kimberley type, Australia. 
 — After Saville-Kent. 
 
320 
 
 ENTOMOLOGY 
 
 Fig. 276. 
 
 tralian plants, the leaves of which present their edges instead 
 of their faces to the sun. 
 
 More than one species of termite may inhabit a single nest ; 
 in one South African nest Haviland found five species of ter- 
 mites and three of ants. The 
 widely distributed genus Euter- 
 nics is essentially a group of 
 inqiiiline, or guest, species. 
 Termite mounds afford shelter 
 to scorpions, snakes, lizards, 
 rats, and even birds, some of 
 which nest in them. The Aus- 
 tralian bushmen hollow out the 
 mounds to make temporary 
 ovens, and even eat the clay of 
 which they are composed, while 
 natives of India and Africa are 
 accustomed to eat the termites 
 themselves, the flavor of which 
 is said to be delicious. 
 
 Ravages. — In tropical re- 
 gions the amount of destruc- 
 tion done by termites is enor- 
 mous, and these formidable 
 pests are a constant source of 
 consternation and dread. They 
 emit a secretion that corrodes 
 metals and even glass, while 
 anything made of wood is sim- 
 ply at their mercy. Always avoiding the light, they hollow 
 out floors, rafters or furniture, leaving only a thin outer shell, 
 and as a result of their insidious work a chair or a table may 
 unexpectedly crumble at a touch. Jamestown, the capital of 
 St. Helena, was largely destroyed by termites (1870) and had 
 to be rebuilt on that account. 
 
 In the United States and Europe few species of termites 
 
 INIound of the " compass " termite 
 of North Australia. — After Saville- 
 Kent. 
 
INTERRELATIONS OF INSECTS 
 
 321 
 
 occur, and they do little injury as compared with the tropical 
 species; thong"h onr common Tcniics flcn'ipcs occasionally 
 damages woodwork, hooks, plants, etc.. in an extensive way, 
 particularly in the Southern states. 
 
 Termitophilism. — Associating with termites are found 
 various other arthropods, mostly insects. Their relations to 
 the termites are, so far as is known, similar to those described 
 beyond between myrmecophilous species and ants. These 
 tcnniiopJiilous forms. howe\'er, have recei\'ed as yet but little 
 attention. 
 
 Honey Bee 
 
 For more than three thousand years the honey bee has been 
 almost unique among insects as an object of human care and 
 study. It was highly prized by the old Greeks and Romans 
 (as appears from the writings of Aristotle, 330 B. C, and 
 Cato, about 200 B. C.) and actually worshiped as a symbol 
 of royalty by the ancient Egyptians, through whose papyri 
 and scarabs the honey bee may be traced back to the time of 
 Rameses I., or 1400 B. C. 
 
 Though its habits have been somewhat modified by domesti- 
 cation, the honey bee, unlike most domesticated animals, is still 
 so little dependent upon man that it readily returns to a wild 
 life. Under many distinct races, which are due largely to 
 human intervention. Apis uiclUfcra is widely distributed over 
 the earth. 
 
 Castes. — The species comprises three kinds of individuals: 
 queen, drone and worker (Fig. 277). The workers are fe- 
 
 FiG. 277. 
 
 The honey bee, Apis mcllift 
 22 
 
 , drone; C, worker. Natural size. 
 
322 
 
 ENTOMOLOGY 
 
 males with an atrophied reproductive system. They constitute 
 the vast majority in any colony and are the only kind that is 
 commonly seen out of doors. Upon the industrious workers 
 falls the burden of the labor; they build the comb, nurse the 
 young, gather food, clean and repair the nest, guard it from 
 intruders, control larval development, expel the drones — 
 briefly, the workers alone are responsible for the general man- 
 agement of the community. Though hibernating workers live 
 eight or nine months, the other workers live but from five to 
 twelve weeks. 
 
 The term queen is, of course, a misnomer, for the govern- 
 ment of the hive is anything but monarchial. The chief duties 
 Pj^. ,„g of the queen, or mother, are simply to lay 
 
 eggs and to lead away a swarm. She is 
 able to deposit as many as 4,000 eggs in 
 twenty-four hours. After a single mat- 
 ing, the spermatozoa retain their vitality 
 in the spermatheca of the queen for three 
 or four years — the lifetime of a queen. 
 The males, or drones, apart from their 
 occasional sexual usefulness, are of little 
 or no service, and their very name has 
 become an expression for laziness. 
 
 The Comb. — Wax, of which the comb 
 is built, is made from honey or sugar, 
 many pounds (twenty, according to 
 A, bases of comb cells; Hubcr) of lioucv bciug required to make 
 
 B, section of comb. Some- ^ ,01 
 
 what enlarged.— A f t e r one pouucl of wax. The workcrs, gorged 
 
 Cheshire. . , ^ ,. ^ ,, • 
 
 With nectar, cling to one another m a 
 dense heated mass until the white films of wax appear under- 
 neath the abdomen (Fig. 102) ; these are transferred to the 
 mouth by means of the wax-pincers (Fig. 263, C) of the hind 
 legs and are masticated with a fluid, secreted by cephalic 
 glands, which alters the chemical composition of the wax and 
 makes it plastic. 
 
 The w^orkers now contribute their wax to form a vertical, 
 
INTERRELATIONS OF INSECTS 
 
 323 
 
 hanging septnm, on the ()])posite sides of which they proceed 
 to bite ont i)its — the bottoms of the future ceHs — using the 
 excavated wax in making the cell walls. The bottom of each 
 cell consists of three rhombic plates (b'ig. 278, A), and the 
 
 278, B) in such a way that each rhomb serves for two cells 
 at once. Wax is such a precious substance that it is used 
 (instinctively, however) always with the greatest economy; 
 the cell walls are scraped to a thinness of 1/280 or even 1/400 
 of an inch, and nowhere is more wax used than is sufficient 
 for strength; one pound of wax makes from 35,000 to 50,000 
 worker cells. The cells, at first circular in cross section, be- 
 come hexagonal from the mutual interference of workers on 
 
 opposite sides of the same 
 
 11 1 r 1 Fig. 279. 
 
 wall ; the lorm, however, 
 
 is by no means a regular 
 hexagon in the mathemat- 
 ical sense, for it is difficult 
 to find a cell with errors 
 of less than 3 or 4 degrees 
 in its angles (Cheshire). 
 Worker cells are one fifth 
 of an inch in diameter, 
 wdiile the larger cells, des- 
 tined for drones or to hold 
 honey, are one quarter of 
 an inch across. 
 
 To strengthen the edges 
 of cells or to fill crevices, 
 the workers use propolis, 
 the sticky exudation from 
 the buds or leaf axils of 
 poplar, fir, horsechestnut 
 or other trees ; though they will utilize instead such artificial 
 substances as grease, pitch or varnish. As winter approaches, 
 the bees apply the propolis liberally, making their abode tight 
 and comfortable. 
 
 Comb of honey bee, showing the insect in 
 arious stages. At the right are large queen 
 ells. — After Renton. 
 
324 
 
 ENTOMOLOGY 
 
 Larval Development. — When the brood cells are ready, 
 the queen, attended by workers, lays an egg in each cell and 
 has no further concern as to its fate. After three days the egg 
 discloses a footless grub (Figs. 279, 280) which depends at first 
 upon the milky food that bathes it and has been supplied from 
 the mouths of the worker nurses. Later the larva is weaned 
 by its nurses to pollen, honey and water. As the stomach and 
 the intestine of the larva do not communicate with each other, 
 the excretions of the larva cannot contaminate the surrounding 
 nutriment, and they are retained until the final moult. Five 
 days after hatching, the larva spins its cocoon, the workers 
 having meanwhile covered the larval cell with a porous cap 
 
 Fig. 280. 
 
 Honey bee. /, feeding larva; />, pupa; s, spinning larva. — After Cheshire. 
 
 of wax and pollen (Fig. 280) and on the twenty-first day after 
 the egg was laid the winged bee cuts its way out, assisted in 
 this operation by the ever-attenti^'e nurses. Now, after acquir- 
 ing the use of its faculties, the newly emerged bee itself 
 assumes the duties of a nurse, but as soon as its cephalic nurs- 
 ing glands are exhausted it becomes a forager. This account 
 applies to the worker ; the three kinds of individuals differ in 
 respect to the number of days required for development, as 
 appears in the following table, from Benton : 
 
 Egg. Larva. Pupa. Total. 
 
 Queen, 3 S'A 7 ^S'A 
 
 Worker, 3 5 13 21 
 
 Drone, 3 6 15 24 
 
 The cells in which queens develop (Fig. 279) are cjuite dif- 
 ferent from worker or drone cells, being much larger, more 
 
INTERRELATIONS OF INSECTS 3^5 
 
 or less irregular in form, and vertical instead of horizontal ; 
 they are attached usually to the lower edge of a comb or else 
 to one of the side edges. 
 
 Other Facts. — The entire organization of the lioney bee 
 has been profoundly modified with reference to floral struc- 
 ture; the life of the bee is wrapped up in that of the flower. 
 The more important structural adaptations of bees in relation 
 to flowers have been described, as well as many of their sen- 
 sory peculiarities ; there remain to be added, however, some 
 other items of interest, chosen from the many. 
 
 A colony of bees in good condition at the opening of the 
 season contains a laying queen and some 30,000 to 40,000 
 worker bees, or six to eight quarts by measurement. Besides 
 this there should be four, five, or even more combs fairly 
 stocked with developing brood, with a good supply of honey 
 about it. Drones may also be present, even to the number of 
 several hundred. 
 
 Ordinarily the queen mates but once, flying from the hive 
 to meet the drone high in the air, when five to nine days old 
 generally. Seminal fluid sufficient to impregnate the greater 
 number of eggs she will deposit during the next two or three 
 years (sometimes even four or five years) is stored at the time 
 of mating in a sac — the spennatheca, opening into the egg- 
 passage. At the time the queen mates, there are in the hive 
 neither eggs nor young larv?e from which to rear another 
 queen ; hence, should she be lost, no more fertilized eggs would 
 be deposited, and the old workers gradually dying ofif wdthout 
 being replaced by young ones, the colony would become extinct 
 in the course of a few months at most, or meet a speedier fate 
 through intruders, such as wax-moth larvae, robber bees, 
 wasps, etc., which its weakness would prevent its repelling 
 longer; or cold is very likely to finish such a decimated colony, 
 especially as the bees, because queenless, are uneasy and do 
 not cluster compactly. 
 
 The liquid secreted in the nectaries of flowers is usually quite 
 thin, containing, when just gathered, a large percentage of 
 
3^6 ENTOMOLOGY 
 
 water. Bees suck or lap it up from such flowers as they can 
 reach with their flexible, sucking tongue, 0.25 to 0.28 inch 
 long. This nectar is taken into the lioncy sac, located in the 
 abdomen, for transportation to the hive. Besides being thin, 
 the nectar has at first a raw, rank taste, generally the flavor 
 and odor peculiar to the plant from which gathered, and these 
 are frequently far from agreeable. To make from this raw- 
 product the healthful and delicious table luxury which honey 
 constitutes — " fit food for the gods " — is another of the func- 
 tions peculiar to the worker bee. The first step is the station- 
 ing of workers in lines near the hive entrances. These, by 
 incessant buzzing of their wings, drive currents of air into and 
 out of the hive and over the comb surfaces. If the hand be 
 held before the entrance at such a time a strong current of 
 warm air may be felt coming out. The loud buzzing heard at 
 night during the summer time is due to the wings of workers 
 engaged chiefly in ripening nectar. Instead of being at rest, 
 as many suppose, the busy workers are caring for the last- 
 gathered lot of nectar and making room for further accessions. 
 This may go on far into the night, or even all night, to a 
 greater or less extent, the loudness and activity being propor- 
 tionate to the amount and thinness of the liquid. Frequently 
 ^.he ripening honey is removed from one set of cells and placed 
 in others. This may be to gain the use of certain combs for 
 the queen, or possibly it is merely incidental to the manipula- 
 tion the bees wish to give it. When, finally, the process has 
 been completed, it is found that the water content has usually 
 been reduced to 10 or 12 per cent., and that the disagreeable 
 odors and flavors, probably due to volatile oils, have also been 
 driven off in a great measure, if not wholly, by the heat of 
 the hive, largely generated by the bees. During the manipu- 
 lation an antiseptic (formic acid) secreted by glands in the 
 head of the bee, and possibly other glandular secretions as well 
 have been added. The finished product is stored in waxen 
 cells above and around the brood nest and the main cluster of 
 bees, as far from the entrance as it can be and still be near 
 
INTERRELATIONS OF INSECTS 327 
 
 to the bro(Ml and l)ees. Tlie work of scalini;- with waxen caj^s 
 then g-ocs forward rapidl)-. the C(^\crino- l)ein_g- more or less 
 porous. Eacli kind of lioney has its distinctive flavor and 
 aroma, derived, as already indicated, mainly from the particu- 
 lar blossoms by which it was secreted, but modified and soft- 
 ened by the manipulaticMi given it in the hives. The last three 
 paragraphs are taken from Benton's useful manual. 
 
 The phenomenon of " swarming " results from the tremen- 
 dous repro(lucti\'e capacity of the queen, though it is immedi- 
 ately an instance of posit k'c pliototropisui, as Kellogg has 
 shown. Accompanied l)y most of the workers, the old cjueen 
 abandons the hive to establish a new colony. The workers 
 that remain behind have provided against this contingency, 
 however, and the departed queen is soon, if not already, re- 
 placed by a new one. 
 
 Determination of Caste. — The difference lietween queen 
 and worker depends solely upon nutrition, both forms being 
 deri\'ed from precisely the same kind of egg. To produce a 
 queen, a large cell of special form is constructed, and its occu- 
 pant, instead of being weaned, is fed almost entirely upon the 
 highly nutritious secretion which worker grubs receive only at 
 first and in limited quantity. This nitrogenous food, the 
 product of cephalic glands, develops the reproductive system 
 in proportion to the amount received. Drone larvse get much 
 of it, though not so much as queens, while an occasional excess 
 of this " royal jelly " is believed to account for the abnormal 
 appearance of fertile workers. 
 
 Parthenogenesis, or reproduction without fertilization, is 
 kno\vn to occur in the bee, as well as in various other insects. 
 The always unfertilized eggs of \vorkers produce invariably 
 drones, as do also unfertilized eggs of the queen. Probably 
 the cjueen cannot control the sex of her eg'gs, as she has long 
 been supposed to do, for Dickel has recently found, among 
 other revolutionary' facts, that all the eggs of the normal 
 mother bee are fertilized. 
 
326 entomology 
 
 Bumble Bees 
 Familiar as the buml)le bees are, their habits are but imper- 
 fectly known. The queen hibernates and in spring- starts a 
 colony, utilizing frequently for this purpose the deserted nest 
 of a field mouse or sometimes the burrow of a mole or gopher. 
 The queen lays her eggs in a small mass of pollen mixed with 
 nectar (Putnam). The larvje eat out cavities in the mass of 
 food and when full grown spin silken cocoons, from which the 
 imago cuts its way out; the empty cocoon being subsequently 
 used as a receptacle for honey. At first only workers are 
 produced and they at once relieve the queen of the duties of 
 collecting nectar and pollen, caring for the young, etc. The 
 workers are of different sizes, the smaller ones being nurses 
 or builders and the larger ones foragers — the kind commonly 
 seen out of doors. In the latter part of summer both males 
 and females are produced, but when severe frost arrives, the 
 old queen, the workers and the males succumb, leaving only 
 the young queens to survive the winter. 
 
 SocL\L Wasps 
 
 The Social Wasps constitute the family Vespid?e, of which 
 we have three genera, namely, Vcspa, Polistcs and Polybia, 
 the last genus being represented by a single Californian species. 
 
 Vespa. — Some species of J^cspa, as ]\ inaculata, make a 
 nest which consists of several tiers of cells protected by an 
 envelope (Fig. 281), attaching the nest frequently to a tree; 
 other species, as gcniianica and vulgaris, make a nest under- 
 ground. The paper of which the nests are composed is manu- 
 factured from weather-worn shreds of wood, which are torn 
 off by the mandibles and then masticated with a secreted fluid 
 which cements the paper and makes it waterproof. 
 
 A solitary queen founds the colony in spring; she starts the 
 nest, lays eggs, feeds the young and brings forth the first 
 workers; these then relieve her — continue the building opera- 
 tions, collect food, nurse the young, in short, assume the bur- 
 den of the labor. In the latter part of summer, fertile males 
 
INTERRELATIONS OF INSECTS 
 
 329 
 
 and females ap])ear and ])airin£^- occnrs. 1dinng-li tlie statement 
 has often l)een made that only the )-inin_i;- c|neens sin'\-i\-e the 
 winter, there is some reason to belie\'e that not only the queens 
 but also males and workers may hibernate successfully in the 
 nest. 
 
 The ]ar\-;c are fed at hrst, b}' rei;in\^itati()n, upon the sugary 
 nectar of tlowers and the juices of fruits, and later u])on more 
 
 Fig. 281. 
 
 Nest of wasp, J'espa maculata. A, outer aspect; B. with envelope cut away to show 
 combs. Greatly reduced. 
 
 substantial food, such as the softer parts of caterpillars, flies. 
 bees, etc., reduced to a pulp by mastication; occasionally wasps 
 steal honey from bees. 
 
 The workers, as is usual among social Hymenoptera, are 
 modified females, incapable of reproduction as a rule, though 
 the distinction between worker and queen is not nearly so sharp 
 among wasps as it is among bees. Worker eggs are said to 
 be parthenogenetic and to produce only males. The males, 
 unlike those of the honey bee, are active laborers in the colony. 
 In the tropics there are wasps that form permanent colonies, 
 store hone}- and swarm, after the fashion of honey bees. 
 
 Polistes. — The preceding description of Vcspa applies 
 equally well to our several species of Polistes, except that the 
 
330 ENTOMOLOGY 
 
 nest of Polistcs is a single comb hanging by a pedicel and with- 
 ont a protecting envelope. Miss Enteman, who has carefnlly 
 studied the habits of Polistcs, finds that the larva spins a lin- 
 ing as well as a cap for its cell, by means of a fluid from the 
 mouth, and that the adults emerge after a pupal period of three 
 weeks, males and females appearing (in the vicinity of Chi- 
 cago) in the latter part of August and early in September. 
 
 Ants 
 
 The habits of ants have engaged the serious attention of 
 some of the most sagacious students of the phenomena of life. 
 Any species of ant presents innumerable problems to the 
 thoughtful investigator and no less than two thousand species 
 of ants are already known. 
 
 A large part of our knowledge of the habits of these remar- 
 kable insects has been obtained by the use of artificial formi- 
 caries, which are easily constructed and have yielded important 
 results in the hands of Lubbock, Forel, Janet, Wasmann, 
 Fielde, Wheeler and other well-known students of ants. 
 
 Castes. — In a colony of ants three kinds of individuals are 
 produced as a rule : males, females and workers, the last being 
 sexually imperfect females. 
 
 The males and females swarm into the air for a nuptial 
 flight, after which the males die, but the females shed their 
 wings and enter upon a new and prolific existence, which may 
 last for many years; a queen of Lasiits iiiger was kept alive 
 by Lubbock for nine years, and one of Formica fiisca, fifteen 
 years, and then its death was due to an accident. 
 
 The workers live from one to seven years, according to the 
 same authority. They constitute the vast majority in any 
 colony and are the familiar forms that so often command at- 
 tention by their industry and pertinacity. In some species 
 certain of the workers are known as soldiers; these may be 
 recognized l)y their larger heads and mandibles. 
 
 Polymorphism. — Ants and termites surpass all other in- 
 sects in respect to the number of forms under which a single 
 
INTERRELATIONS OF INSECTS 331 
 
 species may occur. In some species of ants several types of 
 workers exist ; these are disting-uished by structural peculiari- 
 ties of one kind or another, which possibly indicate special 
 functions, for the most i)art as yet unascertained. Further- 
 more, the sexual indixiduals are not necessarily wing-ed ; some 
 or all of them mav be wingless, especially the females. These 
 wing-less males and females are termed crgatoid, on account 
 of their reseml)lance to workers. 
 
 As to how these various forms are produced, very little is 
 known. Proljably. as among bees, workers and queens are 
 produced from the same kind of eggs, which have been ferti- 
 lized, and the differences between worker and queen and be- 
 tween workers themselves may be due to the ([uality and quan- 
 tity of the food that is supplied to the larvae by their nurses. 
 As in bees, the parthenogenetic eggs laid by abnormal workers 
 may produce males, as Forel, Lubbock and Miss Fielde have 
 found ; or they may produce normal workers, as Reichenbach 
 and Mrs. .V. B. Comstock have found to be the case in Lasius 
 iiigcr. Wheeler points out the possibility of the inheritance 
 of worker characters through the male offspring of workers. 
 
 Larvae. — The numerous eggs laid by one or more queens 
 are taken in charge by the young workers, through ^^■hose 
 assiduous care the helpless larvae are carried to maturity. The 
 nurses feed the larvc'e from their own mouths, clean the larvcC, 
 and carry them from one place to another in order to secure 
 the optimum conditions of temperature, moisture, etc. When 
 a nest is broken open, the workers seize the larv?e and pupie 
 and hurry into some dark place. The pupa is either naked 
 or else enclosed in a cocoon, spun by the larva. 
 
 Nests. — The species of the tropical genus Ecitoii do not 
 make nests but occupy temporarily any suitable retreat which 
 they may happen to find in the course 
 Ants in g-eneral know how to utilize al 
 ties as nests ; they make use of crevices in rocks and under 
 stones or bark, the holes made by bark-beetles, hollow stems 
 or roots, plant-galls, fruits, etc. The extraordinary '* ant- 
 plants " have already received special consideration. 
 
332 ENTOMOLOGY 
 
 Very many ants excavate their nests in the ground ; after 
 a rain these ants are especially industrious in the improvement 
 of the nest, pressing the wet earth into the walls of the gal- 
 leries and adding probably a secreted fluid which acts as a 
 cement ; stones and sticks are often worked into the walls of 
 a nest and the mounds of ants are frequently fashioned about 
 blades of grass or growing herbage of whatever kind. The 
 subterranean galleries are often complex labyrinths ; frequenth^ 
 there are long underground passages extending out in all direc- 
 tions, sometimes to aphid-infested roots of plants or, as in the 
 case of the leaf-cutting ants of the tropics, to trees which are 
 destined to be attacked ; special chambers are set apart for the 
 storage of food and others for eggs, larvse or pupae. 
 
 Often a nest is excavated under a stone. As Forel ob- 
 serves, the stone warms speedily under the rays of the sun, 
 and in damp or cool weather the ants are always in the highest 
 story of the nest as soon as the sun's warmth begins to pene- 
 trate the soil, while they go below as soon as the sun disap- 
 pears or when its heat becomes too strong. They select stones 
 that are neither too large nor too small to regulate the tem- 
 perature well, while other ants attain the same object by mak- 
 ing the nest under sheltering herbage or by making a mound 
 with a hard cemented roof. 
 
 The well-known ant-hills may consist simply of excavated 
 particles of soil or else, as in the huge mounds of Fonnica 
 csscctoidcs, may contain labyrinthine passages in addition to 
 those underground. The mounds of this species are elaborate 
 structures which may last a man's lifetime at least. F. cxscc- 
 foidcs is accustomed to form new colonies in connection with 
 the parent nest; McCook found in the Alleghanies no less than 
 1, 600 nests, forming a single enormous community with hun- 
 dreds of millions of inhabitants, hostile to all other colonies of 
 ants, even those of the same species. This ant covers its 
 mound with twig's, dead leaves, grass and all sorts of foreign 
 material, and is said to close the exits of the nest with bits of 
 wood at night and in rainy weather, removing them in the 
 morning or when the weather becomes favorable. 
 
INTERRELATIONS OF INSECTS T,^^ 
 
 As Forel says [translation] : " The chief feature (^f ant 
 architecture, in contrachstinction to tliat of the l)ees and the 
 \vasi)s. is its irrei^'ularity and want of uniforniit\- — tliat is to 
 say. its adaptal)ihty. or the capacity of making- all the sur- 
 roundings and incidents subserve the purjiose of attaining the 
 greatest possil)le economy of space and time and the greatest 
 ])(^ssil)le comfort. For instance, the same species will live in 
 the Alps under stones which absorb the rays of the sun; in a 
 forest it will live in warm, decayed trunks of trees; in a rich 
 mead(^w it will live in high, conical mounds of earth." Some 
 species construct peculiar pasteboard nests, as Lasiiis ftilii^iiio- 
 sits of Europe and tropical species of Crciiiastogastcr; and 
 others spin silk to fasten leaves together, as Polyrhachis of 
 India and Qicophylla of tropical Asia and tropical Africa, the 
 silk being probably a salivary secretion, according to Forel. 
 
 Habits in General. — The habits of ants are an inexhaustible 
 and ever-fascinating subject of study to the naturalist, and 
 well repay the most critical observation. While each species 
 has its characteristic habits, ants in general have many customs 
 in common. 
 
 Thus ants of one colony exhibit, as a rule, a pronounced 
 hostility toward ants of any other colony, even one of the same 
 species, but recognize and spare members of their own colony, 
 even after many months of separation and though the colony 
 may number half a million individuals. This recognition is 
 effected by means of an odor, distinctive of the colony and ap- 
 parently inheritable. When an ant is washed and then restored 
 to its fellows, it is treated at first as an intruder and may even be 
 killed. The same is true when the ant has been smeared with 
 juices from the bodies of alien ants. According to Miss 
 Fielde, workers of colony A, smeared with the juices from 
 crushed ants of colony B and then placed in colony B are 
 received amicably, but at once set about to destroy their hosts, 
 like " wolves in sheep's clothing." These statements apply 
 only to workers, however, for alien larvae and pup?e are fre- 
 quently captured and reared by ants, and Miss Fielde states 
 
334 ENTOMOLOGY 
 
 that king's of one colony of Sfciiamiiia when introduced into 
 anotlier colony are even cordially received. 
 
 Some of the most careful students of the habits of ants agree 
 that these insects can communicate with one another. An ant 
 discovers a supply of food, returns toward the nest, meets a 
 fellow worker, the two stroke antenucne and then both start 
 back to the food ; before long other members of the colony 
 swarm to the prize. It has been thought that the odor of the 
 food or some other odor, left by the first ant, serves as a trail 
 for the other ants to follow. Bethe, indeed, infers from his 
 experiments that this phenomenon is purely mechanical and 
 involves no psychical qualities on the part of the ants. His 
 Dwn experiments, however, show that one ant can inform an- 
 other by means of an odor as to the whereabouts of food — 
 which is certainly one form of communication. 
 
 Ants avoid sunlight as a rule but prefer rays of lower re- 
 frangibility to those of higher. Upon exposing ants to the 
 colors of the spectrum, as transmitted through glasses of dif- 
 ferent colors, Lubbock found that they congregated in greatest 
 numbers under the red glass and that the numbers diminished 
 regularly from the red to the violet end of the spectrum, there 
 being very few individuals under the violet glass. 
 
 Miss Fielde, experimenting with cjueens, workers and young 
 of Stcnamma fulvum picciiui in an artificial nest, covered half 
 the nest with orange glass and half with violet. '* The ants re- 
 moved hastily from under the violet as often as an interchange 
 of the panes was made, once or twice a day, for about twenty 
 days. Thereafter they became indifi^erent to the violet rays." 
 " The plasticity of the ants is remarkably shown in their grad- 
 ually learning to stay where they were never disturbed by me, 
 under rays from which their instincts at first withdrew them." 
 
 Ants are sensitive not only to the different colors of the 
 spectrum but also to the ultra-violet rays, which produce no 
 appreciable effect on the human retina (though they induce 
 chemical changes). If obliged to choose between the two. ants 
 prefer violet to ultra-violet rays, as Lubbock found. If, how- 
 
INTERRELATIONS OF INSECTS 335 
 
 ever, the ultra-violet rays are intercepted. l)y means of a screen 
 of sulphate of (|uinine or l)isuli)hi(le of carbon, the ants then 
 collect under the screen in preference to under the \'iolet rays. 
 
 r^'om lack of experience we can form no ade(|uate idea as 
 to the range of sensation in ants or other insects. Ants can 
 taste substances that we cannot, and vice versa. They show 
 no response to sounds of human contrivance, yet many of them 
 possess stridulating organs and organs that are doubtless audi- 
 tor}-; whence it may be inferred that ants can communicate 
 with one another by means of sounds. In rare instances the 
 stridulation of an ant can impress the human ear, as in a spe- 
 cies of At fa mentioned by Sharp. 
 
 Experiments show that ants, as well as bees and wasps, find 
 their way back to the nest, not by a mysterious " sense of 
 direction," but by remembering the details of the surroundings, 
 and in the case of ants, by means of an odor left along the 
 trail. 
 
 In studying the habits of ants, the greatest care must be 
 exercised in order to discriminate between actions that may 
 be regarded as purely instinctive and those that may indicate 
 some degree of intelligence. If any insects show sig'ns of in- 
 telligence, the social Hymenoptera do so ; but in the study of 
 this recondite subject, false conclusions can be avoided only 
 l)y observation and experiment of the most critical kind. 
 
 Hunting Ants. — Some ants, as Formica fusca, live by the 
 chase, hunting their prey singly. The African " driver ants " 
 (Anoinnia airois), although blind, hunt in immense droves, 
 consuming all the animal refuse in their way, devouring all the 
 insects they meet, and not hesitating to attack all kinds of ver- 
 tebrates ; these ants ransack houses from time to time and 
 clear them of all vermin, though they themselves are a great 
 nuisance to the householder. The Brazilian species of Ecitou 
 (Fig. 283, B, C) have similar habits and are likewise blind, or 
 else have but a single lens on each side of the head. These in- 
 sects hunt in armies of hundreds of thousands, to the terror of 
 everv animate thing that thev come across. Thev have no 
 
SS^ ENTOMOLOGY 
 
 permanent abode, but now and then appropriate some conveni- 
 ent hole for the purpose of raising a new brood of marauders. 
 
 Slave-making Ants. — It is a fact that some ants make 
 sla^'es of other species. Formica saiiguiiica, for example, will 
 attack a colony of Formica fiisca, kill its active members in 
 spite of their determined resistance, kidnap the larv?e and pupae 
 and carry them home, where the captives receive every care, 
 and at length, as imagines, serve their masters as faithfully as 
 they would serve their own species. In the x-\lleghanies, ac- 
 cording to McCook, colonies of F. fusca occur where there are 
 no " red ants " (F. sangiiinca), but are hard to find where the 
 enslaving species occurs. 
 
 Although F. saiigiiiiica can exist very well without slaves. 
 Polycrgus rufcscciis, of Europe, is notoriously dependent upon 
 their services, it being doubtful whether it is capable of feed- 
 ing itself. This species is powerful as a warrior, but its man- 
 dibles are of little use, except to pierce the head of an adver- 
 sary. Sfroiigyloiiotiis is still more helpless, while Ancrgatcs 
 (also of Europe) is said to depend absolutely upon its slaves. 
 
 Polycrgus litcidiis occurs in the Alleghanies, where the col- 
 onies of this species, according to McCook, contain large num- 
 bers of the workers of Formica schaiifussi. The masters are 
 good fighters but do no other work, and have not been seen to 
 feed themselves, though they may often be seen feeding from 
 the mouths of their slaves. 
 
 Honey Ants. — Among ants in general, the workers that 
 stay in the nest receive food from the mouths of the foragers 
 — a custom which has led to the extraordinary conditions 
 found in the " honey ants," in which certain of the workers 
 sacrifice their own activity in order to act as living reservoirs 
 of food for the benefit of the other members of the colony. 
 This remarkable habit has arisen independently, in different 
 genera of ants, in North America, Australia and South Africa, 
 as Lubbock observes. 
 
 The honey ant whose habits are best known, through the 
 studies of McCook and others, is Myrmccocystus mcUigcr, of 
 
INTERRELATIONS OF INSECTS 
 
 337 
 
 Mexico, New Mexico and southern Colorado. In this species 
 some of the workers hang skig-gishly from the roof of their 
 Httle dome-hke chamher, several inches underground, and act 
 as permanent receptacles for the so-called honey, which is a 
 transparent sugary exudation from certain oak-galls ; it is gath- 
 ered at night by the foraging workers and regurgitated to the 
 
 Fig. 282. 
 
 Honey ants, Myntiecocystus mclligcr, clinging to the roof of tht^ir chamber, 
 natural size. — After McCook. 
 
 mouths of the " honey-bearers," whose crops at length become 
 distended with honey to such an extent that the insects (Fig. 
 282) look like so many little translucent grapes or good-sized 
 currants. This stored food is in all probability drawn upon 
 by the other ants when necessary. 
 
 Leaf-cutting Ants. — The most dangerous foes to vegeta- 
 tion in tropical America are the several species of Atta (CEco- 
 doiiia, Fig. 283, A). Living in enormous colonies and capable 
 of stripping a tree of its leaves in a few hours, these formida- 
 ble ants are the despair of the planter; where they are abun- 
 dant it becomes impossible to grow the orange, coffee, mango 
 and many other plants. These ants dig an extensive under- 
 ground nest, piling the excavated earth into a mound, some- 
 23 
 
338 
 
 ENTOMOLOGY 
 
 times thirty or forty feet in diameter, and making paths in 
 various directions from the nest for access to the plants of the 
 
 Fig. 
 
 A, leaf-cutting ant, Atfa ccphalotcs. B, wandering ant, Eciton drcfanophorum ; C, 
 Eciton omnivoriun. Natural size. — After Shipley. 
 
 Fig. 284. 
 
 vicinity ; Belt often found these ants at work half a mile from 
 their nest; they attack flowers, fruits and seeds, but chiefly 
 leaves. Each ant, by laboring 
 four or fi\-e minutes, bites out a 
 
 a leaf (Fig. 284) and carries it 
 home, or else drops it for another 
 worker to carry ; and two strings 
 of ants may be seen, one carry- 
 ing their leafy burdens toward the 
 nest, the other returning for more 
 plunder. 
 
 The use made of these leaves 
 has been the subject of much dis- 
 cussion. Belt found the true ex- 
 planation, but it remained for 
 Moller to investigate the subject 
 so thoroughly as to leave no room 
 for doubt. The ants grow a fun- 
 gus upon these leaves and use it 
 as food. The bits of leaves are 
 kneaded into a pulpy, spongy 
 mass, upon which the fungus at 
 length appears. The food for 
 
 A, B, cuts made in Ciiphea 
 leaves in four or five minutes by 
 Atta discigera; natural size. C, 
 Atta discigera transporting severed 
 fragments of leaves; reduced. — 
 After Moller. 
 
INTERRELATIONS OF INSECTS 
 
 339 
 
 Fk;. 28; 
 
 the sake n{ which the ants carry on their complex o])er- 
 ations consists of the knobbed ends of fnni^ns threads 
 (Fig. 285), and these bodies, rich in fluid, form the most 
 important, if not the sole food of the leaf-cnttini^- ants, fjy 
 assiduously wcedins;- out all foreig-n organisms the ants ob- 
 tain a pure culture of the fungus, and by pruning the fungus 
 the}' keep it in the N'egeta- 
 tive condition and pre\-ent 
 its fructification: under 
 exceptional circumstances, 
 however, the fungus de\-el- 
 oi)s aerial organs of fructi- 
 fication of the agaricine 
 type, but this species (Ro- 
 £ifcs gongylophova ) has 
 never been found outside 
 of ants' nests. The pecu- 
 har clubbed threads were 
 produced by Moller in arti- 
 ficial cultures and are not 
 spores, but products of cul- 
 ti^'ation. Other ants are known to cultivate other kinds of 
 fungi for similar purposes. 
 
 McCook has found a leaf-cutting ant {Atta fcrvcns) in 
 Texas, and mentions that it cuts circular pieces out of leaves 
 of chietiy the live-oak, these being (h-opped to the ground and 
 taken to the nest by another set of workers. He records an 
 underground tunnel of Atta fcrvens which extended 448 feet 
 from the nest and then opened into a path 185 feet in length; 
 the tunnel w^as 18 inches below the surface on an average, 
 though occasionally as deep as 6 feet, and the entire route led 
 with remarkable precision to a tree which was being defoliated. 
 
 The same observer has given also a brief account of a leaf- 
 cutting ant that lives in New Jersey. This species (Atta scp- 
 tcntrionalis) cuts the needle-like leaves of seedling pines into 
 httle pieces, which are carried to the nest. Two columns of 
 
 Fungus clumiis {Rocitcs gongylof'lwra) 
 cultivated by ants of the genus Atta. 
 Greatly magnified. — After Moller. 
 
340 ENTOMOLOGY 
 
 workers may be seen, one composed of individuals returning 
 to the nest, each with a piece of a pine needle, the other of 
 outgoing workers. The nest is a simple structure, extending 
 some seven inches underground and ending in a chamber in 
 which are several small pulpy balls, consisting probably of 
 masticated leaves. Further studies upon our own leaf-cutting 
 ants, modeled after the admirable studies of Moller, are much 
 to be desired. 
 
 Harvesting Ants. — Lubbock observes that some ants col- 
 lect the seeds of violets and grasses and preserve them care- 
 fully for some purpose as yet unknown. From such a begin- 
 ning as this may have arisen the extraordinary habits of the 
 agricultural, or harvesting, ants, of which some twenty species 
 are known from various parts of the world. 
 
 The Texas species Pogonouiyrmcx harhafus, studied by 
 Lincecum and by McCook, clears away the herbage around its 
 nest (even plants several feet high and as thick as a man's 
 thumb) and levels the ground, forming a disk often lo or 12 
 and sometimes 15 to 20 feet in diameter, from which radiating 
 paths are made, from 60 to 300 feet in length. The ants go 
 back and forth along these roads, carrying to the nest seeds 
 which they have collected from the ground or else have cut 
 from plants ; these seeds are stored in " granaries " several feet 
 underground and are eventually used as food. The ants pre- 
 fer the seeds of a grass, Arisfida oUgantha, but the oft-repeated 
 statement that they sow the seeds of this " ant-rice," guard it 
 and weed it, is denied by Wheeler. 
 
 Notwithstanding the elaborate studies of McCook upon this 
 subject, there still remain not a few essential questions to be 
 answered. 
 
 Myrmecophilism. — To add to the complexity of ant-life, 
 the nests of ants, when at all extensive, are frequented by a 
 great variety of other arthropods, which on account of their 
 association with ants are termed inyniiccophilcs. Most of 
 these are insects, of which Wasmann has catalogued 1,200 
 species, but not a few are spiders, mites, crustaceans, etc. 
 
INTERRELATIONS OF INSECTS 341 
 
 Thoug-h the di\'erse relations l:>et\veen myrmecophiles and ants 
 are but partially understood, these aliens may for convenience 
 be considered under f\\e ""roups : captii'cs, i:^!icsts. Z'isitors, iji- 
 trudcrs and parasites. 
 
 Captives. — l^esides ens]a\ing- other species, as already men- 
 tioned, ants make use of aphids and some coccids for the sake 
 of their palatable products. The attendance of ants upon col- 
 onies of plant lice is a common occurrence and one that repays 
 careful observation. With the aid of a hand-lens, one may 
 see the ants hastening" about among" the plant lice and patting" 
 them nervously with the antenna.^ until at length some aphid 
 responds by emitting" from the end of the abdomen a g^listening 
 drop of watery fluid, which the ant snatches. This fluid, con- 
 trary to prevalent accounts, is not furnished by the so-called 
 honey-tubes of the aphid, but comes from the alimentary canal ; 
 the " honey-tubes " are glandular indeed, but are probably 
 repellent in function. In some instances ants give much care 
 to their aphids, for example covering them with sheds of mud, 
 which are reached through covered passagew^ays. More than 
 this, however, some ants actually collect aphid eggs and pre- 
 serve them over winter as carefully as they do their own eggs. 
 In one such instance, Lubbock found that the aphids upon 
 hatching, after six months, were brought out by the ants and 
 placed upon young shoots of the English daisy, their proper 
 food plant. In our own country, as Forbes has discovered, 
 the eggs of the corn root louse (Aphis maid irad ids) are col- 
 lected in autumn by ants (especially of the genus Lasiiis) and 
 stored in the underground nests. In winter, the eggs are taken 
 to the deepest parts of the nest, and on bright spring days they 
 are brought up and even scattered about temporarily in the 
 sunshine; while if a nest is opened, the ants carry off the aphid 
 eggs as they would their own. In spring, the ants tunnel to 
 the roots of pigeon grass and smartweed, seize the aphids and 
 carry them to these roots, and later to the roots of Indian 
 corn. Throughout the year the ants exercise supervision over 
 these aphids ; occasionally, as Forbes says, an ant seizes a 
 
342 ENTOMOLOGY 
 
 winged louse in the field and carries it down out of sight, and 
 in one such instance it appeared that the wings had been 
 gnawed away near the body, as if to prevent the escape of 
 the louse. Similar relations exist also between ants and some 
 species of scale insects. 
 
 Guests. — Though Aphides and CoccidcT are able almost 
 always to live without the help of ants, there are some insects 
 which have never been found outside the nests of ants. Most 
 of these insect guests are beetles, notably Staphylinidae and 
 Pselaphidae. The rove-beetles make themselves useful by 
 devouring refuse organic matter, and these scavengers are un- 
 molested by the ants with which they live. A few myrme- 
 
 FlG. 286. 
 
 Lomcchusa stniinosa being freed of mites by Dinarda dentata. — After Wasmann. 
 
 cophilous beetles furnish their hosts with a much-coveted secre- 
 tion and receive every attention from the ants, which clean 
 these valuable beetles and even feed them mouth to mouth, as 
 the ants feed one another. Lomechusa (Fig. 286) is one of 
 these favored guests, as it has abdominal tufts of hairs from 
 which the ants secure a secreted fluid. Atcniclcs (Fig. 287) 
 is another ; it solicits and obtains food from the mouth of a 
 foraging ant as if it were an ant itself. In the Alleghanies, 
 
INTERRELATIONS OF INSECTS 
 
 343 
 
 Afciiirli's cdT'd occurs in the nests of Fonuica nifa, and is much 
 ])rize(l l)y this ant on account of tlie lluid wliicli the 1)eetlc 
 secretes from g'lanchilar hairs on the sides of tlie alxlomen. 
 The beetle Clavii^cr has at the base of each elytron a tuft 
 of hairs, which the ants lick persistently. This ])eetle is Ijlind 
 
 Fig. 287. 
 
 Atemclcs emarginatiis being fed by an ant, lilynnica scahrinodis. — After Wasmann. 
 
 and appears to be incapable of feeding itself; for when de- 
 l)rived of ant-assistance it dies, even though surrounded by 
 food. These cases of symbiosis, or mutual benefit, are well 
 authenticated. 
 
 Visitors. — Many myrmecophilous insects are not restricted 
 to ants' nests, but are free to enter or to leave. This is true of 
 such Staphylinidse as visit formicaries simply for shelter or to 
 feed upon detritus, and these visitors are treated with indif- 
 ference by the ants. 
 
 Intruders. — Not so. however, with species that are inimical 
 to the interests of the ants, such as many species of Staphy- 
 linidfe and Histerid?e, which steal food from the ants, kill 
 them or devour their larvje or pupse at every opportunity. 
 The ants are hostile to these marauders, though the latter often 
 escape through their agility or else rely upon their armor for 
 protection. Oiicdius brcz'is and Myniicdoiiia, as Schwarz 
 observes, are soft-bodied forms which remain beside the walls 
 of the galleries or near the entrance of a nest and attack soli- 
 tary ants; while Hctccriiis, which mixes with the ants, is pro- 
 
344 
 
 ENTOMOLOGY 
 
 tected by its hard and smooth covering, under which the legs 
 and antennae can be withdrawn. Such an enemy is an un- 
 avoidable evil from the standpoint of an ant. 
 
 Janet has described the amusing way in which an audacious 
 species of Lcpismina steals food from the very mouths of ants. 
 As is well known, ants are accustomed to feed one another 
 from mouth to mouth. When the foragers, filled with honey 
 or other food, return to the nest, they are solicited for food 
 by those that have remained at home ; as a forager and a beg- 
 gar stand head to head, the former disgorges small drops of 
 
 Fig. 288. 
 
 Lepismina stealing food from a pair of ants. — After Janet. 
 
 food, which are seized by the latter. While a pair of ants are 
 engaged in this performance (Fig. 288). and a drop of honey 
 is being passed, the Lepismina rushes in, grabs the drop and 
 hurries away. As might be expected, these interlopers are 
 
 the nest to another. 
 
 Parasites. — Nematode worms occupy the pharyngeal glands 
 of ants ; larvae of Sfylops inhabit their bodies ; more than thirty 
 kinds of mites attach themselves to the heads or feet of ants; 
 while ChalcididcC and Proctotrypid?e parasitize ants' eggs. 
 
CHAPTER XI 
 
 INSECT BEHAVIOR 
 
 1lie subject of insect behavior will be considered under three 
 heads: (i) Tropisms, (2) Instinct, (3) Intelligence. 
 
 I. Tropisms 
 
 Environmental influences, such as light, temperature or 
 moisture, may control the direction of locomotion of an organ- 
 ism by determining the orientation of its l)ody. The reaction 
 of the organism under these circumstances is known as a 
 tropic, or tactic, reaction. A moth, for example, flies tow^ard 
 a flame — is positively pJiototropic ; a cockroach, on the con- 
 trary, avoids the light — is negatively pJiototropic. A plant 
 turns toward the sun — in other words, is positively lielio- 
 tropic. 
 
 An insect flies toward the light as inevitably and as mechan- 
 ically as a i)lant turns toward the sun ; indeed, the tw^o phenom- 
 ena are fundamentally the same. Some students, however, 
 prefer to use the term taxis for bodily movements of motile 
 organisms, and the term tropisin for turning- movements of 
 fixed organisms. 
 
 The study of tropic reactions, though comparatively new, 
 has already illuminated the whole subject of the behavior of 
 organisms and placed it on a rational basis. The complex 
 tropisms of insects offer a fresh and large field to the investi- 
 gator, comparatively little having as yet been published upon 
 the subject. 
 
 Chemotropism. — Positive and negative cheiiiotropisiii, as 
 Wheeler observes, " are among the most potent factors in the 
 lives of insects." Insects are affected positively or negatively 
 by such substances as can affect their end-organs of smell or 
 taste. Positive chemotropism enables many insects to find 
 
 345 
 
346 ENTOMOLOGY 
 
 their food or their mates ; and negative chemotropism enables 
 them to avoid injurious substances. This negative reaction 
 on the part of other organisms is made use of also by such 
 insects as emit repellent odors. 
 
 A maggot orients its body with reference to a source of 
 food and then moves toward the food just as mechanically as 
 a moth flies to a flame. The maggot, as Loeb maintains, is 
 influenced chemically by the radiating diffusion from a piece 
 of meat, and follows a line of diffusion to the center of diffu- 
 sion in much the same way that a moth follows a ray of light 
 to its source. In both cases a stimulus affects muscular tissue ; 
 the animal orients its body until the muscular tension is sym- 
 metrically distributed, and then locomotion brings the animal 
 to the source of the stimulus, whether it be food or light or 
 something else. 
 
 The remarkable " instinctive " action of the fly in laying 
 her eggs on meat is due, according to Loeb, simply to the fact 
 that both the fly and the maggot have the same kind of posi- 
 tive chemotropism. Similarly also in the case of such butter- 
 flies or other insects as lay their eggs on a special kind of plant. 
 It is certain that " neither experience nor volition plays any 
 part in these processes." 
 
 Hydrotropism. — Wheeler observed that beetles of the gen- 
 era Haliplits and Hydropunis were positively Jiydrotropic ; that 
 when released on the shore from a bunch of water plants, they 
 scrambled toward the lake, twenty feet away. Collectors take 
 advantage of the negative hydrotropism of Bcinhidiuui, 
 Elaphrus, OmopJwon and other shore-dwelling beetles by 
 splashing the water upon the dry bank, when the beetles leave 
 their places of concealment and are easily caught. 
 
 It is well known that after a rain ants carry their young out 
 into the sunshine, though when the upper parts of the nest 
 become too dry, the ants transfer their eggs, larv?e and pupae 
 to lower and moister galleries. In these instances, however, 
 we have to deal with thcnnotropism as well as hydrotropism. 
 
 Thigmotropism. — Negative thigiiwfropisiii, as displayed in 
 
INSECT BEHAVIOR 34/ 
 
 the withdrawal from contact, is a common iiliencimenon amon«- 
 animals, from T'rotozoa to X'ertcbrata. and is often conducive 
 to the safety of an organism ; though the negative response 
 occurs none the less, whether it is to prove useful or not. and 
 occurs as automatically as the collapse of a sensitive plant at 
 a touch. • 
 
 Positive thig-motropism is less common, though nevertheless 
 widespread among animals. Protozoa and Infusoria cling to 
 solid bodies and become aggregated about them. Cockroaches 
 squeeze themselves into crevices until their bodies come into 
 close contact with surrounding surfaces. A moth, Pyrophila 
 {Ainphipyra) pyrainidoidcs, is accustomed to squeeze into 
 crevices under loose bark or elsewhere, though this habit, 
 though doubtless protective, is not performed for the purpose 
 of self-concealment. That this is not a case of negative photo- 
 tropism. it was proved by Loeb, who wrote : " I placed some 
 of these animals in a box, one-half of which was covered with 
 a non-transparent body, the other half with glass. I covered 
 the bottom of the box with small glass plates which rested on 
 small blocks, and were raised just enough from the bottom to 
 allow an Ainphipyra to get under them. Then the Ainphipyra 
 collected under the little glass plates, where their bodies w-ere 
 in contact with solid bodies on every side, not in the dark cor- 
 ner wdiere they would have been concealed from their enemies. 
 They even did this when in so doing they were exposed to 
 direct sunlight. This reaction also occurred when the whole 
 box was dark. It was then impossible for anything but the 
 stereotropic [thigmotropic] stimuli to produce the reaction." 
 
 Rheotropism. — Fishes swimming or heading directly 
 against a current of water illustrate positive rheotropism. 
 When facing the current, the resistance of the water is sym- 
 metrically distributed on the body of the animal and is met 
 by symmetrical muscular action, in the most economical man- 
 ner. Many aquatic insects offer such examples of rheotropism, 
 either positive or negative. 
 
 Anemotropism. — Various flies orient the body with refer- 
 
34c> ENTOMOLOGY 
 
 ence to the direction of the wind. AMieeler observed swarms 
 of the male of Bibio alhipennis poising in the air, with all the 
 flies headed directly toward the gentle wind that was blowing. 
 If the wind shifted, the insects at once changed their position 
 so as again to face to windward ; a strong wind, however, blew 
 them to the grcTund. The males of an anthomyiid (Ophyra 
 Iciicostoiiia) . accdrding to the same naturalist, hover in swarms 
 in the shade for liours at a time; if the breeze subsides they 
 lose their definite orientation, but if it is renewed they face 
 the wind with military precision. In Syrphidse, he finds, either 
 males or females are positively ancinotropic. The midges of 
 the genus Chirojioiinis, which on summer days dance in swarms 
 for hours over the same spot, orient themselves to every pass- 
 ing breeze. So also in the case of Empididne. which Wheeler 
 has observed swarming in one spot every day for no less than 
 two weeks, possibly on account of " some odor emanating from 
 the soil and attracting and arresting the flies as they emerged 
 from their pup?e." 
 
 The Rocky Mountain locusts " move with the wind and 
 when the air-current is feeble are headed away from its 
 source"; when the wind is strong, however, they turn their 
 heads toward it. 
 
 Anemotropism and rheotropism are closely allied phenom- 
 ena. As A\'heeler says. " The poising fly orients itself to the 
 wind in the same way as the swimming fish heads upstream." 
 adjusting itself to a gaseous instead of a liquid current. " In 
 both cases the organism naturally assumes the position in 
 which the pressure exerted on its surface is symmetrically dis- 
 tributed and can be overcome by a perfectly symmetrical action 
 of the musculature of the right and left halves of the body." 
 
 Geotropism, — Gravity frequently determines the orienta- 
 tion and direction of locomotion of an animal. A freshly 
 emerged moth hangs with the abdomen downward and re- 
 mains in this position until the wings have expanded. Certain 
 dolichopodid flies found on the bark of trees " rest or walk 
 with the long axis of the body perpendicular to the earth and 
 
INSECT BEHAVIOR 
 
 349 
 
 parallel with the lonq- axis of the trunk of the tree and the 
 head pointing- upwards. When disturbed they tly off, but 
 very soon alis^iit nearer the earth and ag'ain walk upward." 
 (Wheeler.) Coccinelli(l;e and cockroaehes are also neg'atively 
 gcotropic. ddie latter insects, as Loeb has obser\ed, tend to 
 leave a horizontal surface but come to rest on a surface that 
 is vertical or as nearly so as i)ossible. 
 
 Wheeler says, " Geotropic as well as anemotro]:)ic orienta- 
 tion is not altered for the sake of response to lig^ht. Even if 
 the insect be strongly heliotropic, as is the case in most Dip- 
 tera, it orients itself to the wind or to gravity no matter 
 whence the light may fall." 
 
 Phototropism. — It is a matter of common observation that 
 house flies, butterflies, bees and many other diurnal insects fly 
 toward the light ; and that cockroaches and bedbugs avoid the 
 light. These are familiar examples of pJiotofropism, or the 
 " control of the direction of locomotion by light." The pho- 
 
 A, tracks made on paper by a larva of Liicilia cccsar moving out of a spot of ink 
 under the influence of light; A and B show respectively the first and second 
 directions of the light. B, tracks made in the dark. — After Pouchet. 
 
350 ENTOMOLOGY 
 
 totropic response is either positive or negative according as 
 the organism moves, respectively, toward or away from the 
 source of Hght. Maggots of Lucilia cccsar and of many other 
 fiies are negatively phototropic as a rule (Fig. 289, A), but in 
 the absence of light (other directive stimuli being excluded, of 
 course) wander about indifferently (Fig. 289. B) . 
 
 Do the different rays of the spectrum differ in phototropic 
 power? This question has occurred to many investigators, 
 who have found that, in general, the rays of shorter wave 
 length, as violet or blue, are more effective than those of longer 
 wave length, as yellow or red; the latter in fact acting like 
 darkness. Ants avoid violet rays as they would avoid direct 
 sunlight, but carry on their operations under yellowish red light 
 as they would in darkness. Miss Fielde has made use of this 
 fact in studying the habits of ants, by using as a cover for her 
 artificial formicaries an orange-red sheet of glass such as the 
 photographer uses for his dark room. Though ants avoid 
 violet rays, they prefer them to ultra-violet rays, as Lubbock 
 found ; though the latter rays produce no sensible effect on the 
 human organism. 
 
 These responses to light are inevitable on the part of the 
 organism, whether they are beneficial or harmful, and it is now 
 becoming recognized that the reactions of both plants and ani- 
 mals to light are fundamentally the same. 
 
 Phototaxis and Photopathy. — A phototropic organism, if 
 bilaterally symmetrical, orients itself with the head directly 
 toward or else directly away from the source of light and 
 moves toward or away from the light, as the case may be. In 
 either event the long axis of the organism becomes parallel 
 with the rays of light. Now a ray of light is ever diminishing 
 in intensity from its source, and it would seem that differences 
 of intensity along the paths of light rays determine the orien- 
 tation and consequent direction of locomotion of the organism. 
 Some investigators, however, distinguish between the effects 
 of intensify of light and those of its direction. Thus by in- 
 geniously contrived experiments, it has been found, apparently, 
 
INSECT BEHAVIOR 351 
 
 that Protista (Stvashuvger) .Dal^Juiia (Davenport and Cannon) 
 and the caterpillars of Povtlicsia ( Loeb) move toward a source 
 of lig'ht even while, in so doin^-, thev are passing- into reg"ions 
 of /(\s\s- intensity of illumination, l^'or this migration as deter- 
 mined by the direction of the light rays, the term pliototaxis 
 is by some authors (as Davenport) reserved. Usually, how- 
 ever, the direction of locomotion docs depend on differences 
 of intensity, without regard to the direction whence the light 
 comes. This " migration towards a region of greater or less 
 intensity of light " has been termed pliotopathy, and organisms 
 are said to be photo pliil or pliotophob, according as they move, 
 respectively, toward or away from a more intensely illumi- 
 nated area. 
 
 Verworn and others maintain that differences of intensity 
 are sufificient to account for all phototropic phenomena. 
 
 Optimum Intensity. — It has been found that there is a 
 certain optiuiinn degree of light, differing according to the 
 organism, toward which the organism will move, from either 
 a region of greater illumination or one of less. The organism 
 appears to be attuned to a " certain range of intensity." This 
 attunement is used by Davenport to explain apparent anoma- 
 lies between the response to light of a butterfly and that of a 
 moth. Butterflies are positively phototropic to sunlight and 
 most moths are negatively so. Why, then, do moths fly 
 toward a lamp or an electric light ? The answer is given that 
 the moth is positively phototropic up to a certain intensity of 
 light, at which it becomes negatively phototropic. " Butter- 
 flies are attuned to a high intensity of light, moths to a low 
 intensity ; so that bright sunlight, which calls forth the one, 
 causes the other to retreat. On the other hand, a light like 
 that of a candle, so weak as not to stimulate a butterfly, pro- 
 duces a marked response in the moth." (Davenport.) 
 
 The circling of moths and other insects about a light is a 
 matter of common observation, an explanation for which has 
 been given by Loeb. Loeb says, " If a moth be struck by the 
 Hght on one side, those muscles which turn the head toward 
 
352 ENTOMOLOGY 
 
 the light become more active than those of the opposite side, 
 and correspondingly the head of the animal is turned toward 
 the source of light. As soon as the head of the animal has 
 this orientation and the median-plane (or plane of symmetry) 
 comes into the direction of the rays of light, the symmetrical 
 points of the surface of the body are struck by the rays of light 
 at the same angle. The intensity of light is the same on both 
 sides, and there is no reason why the animal should turn to 
 the right or left, away from the direction of the rays of light. 
 Thus it is led to the source of the light. Animals that move 
 rapidly (like the moth) get into the flame before the heat of 
 the flame has time to check them in their flight. Animals that 
 move slowly are afTected by the increasing heat as they ap- 
 proach the flame ; the high temperature checks their progres- 
 sive movement and they walk or fly slowly about the flame." 
 As Loeb insists, the moth " does not fly into the flame out of 
 ' curiosity,' neither is it ' attracted ' by the light ; it is only 
 oriented by it and in such a manner that its median-plane is 
 brought into the direction of the rays and its head directed 
 toward the source of light. In consequence of this orienta- 
 tion its progressive movements must lead it to the source of 
 light." 
 
 Factors Infiuencing Phototropism. — The response of an 
 organism to light is influenced by previous exposure to light, 
 by temperature, moisture, nutrition and other factors, all of 
 which have to be taken into account in experiments on photo- 
 tropism. 
 
 Loeb found that larvcX of the moth Euproctis elirysorrlicva, 
 driven by the warm sunshine out of the nest in which they 
 have hibernated, crawl upward to the tips of branches and feed 
 upon the buds and new leaves. This self-preservative " in- 
 stinct " is purely a response to light. The caterpillars are 
 positively phototropic, and as the horizontal components of the 
 surrounding light neutralize each other, only the light from 
 above is effective as a stimulus to orientation. After feeding, 
 however, the larvK are no longer positively phototropic and 
 
INSECT BEHAVIOR 353 
 
 crawl downward ; in otlier words, they are positively photo- 
 tropic only so loiii^- as tliey are nnfed. Here the kind of pho- 
 totropism is dependent upon nutrition. 
 
 Phototropism may be overruled by chemotropisni and influ- 
 enced by conditions of metabolism, as Parker found for the 
 buttertly J'aiicssa autiopa. In his words: J'aiicssa oiitioj^a, in 
 brio-ht sunligiit, comes to rest widi the head away from the 
 source of light, that is, it is neg-atively phototropic, when the 
 surface on wdiich it settles is not perpendicular or very nearly 
 perpendicular to the direction of the sun's rays. When, how- 
 ever, this surface is perpendicular to the sun's rays the insect 
 settles without reference to the direction of the rays. When 
 feeding- or near food [such as running- sap] the butterflies do 
 not respond phototropically. 
 
 This negative phototropism is seen only in intense sunlight 
 and after the butterfly has been on the wing, i. e., after a cer- 
 tain state of metabolism has been established. 
 
 V. antiopa creeps and flies toward a source of light, that is, 
 it is positively phototropic in its locomotor responses. Posi- 
 tive phototropism also occurs in intense sunlight, and is not 
 dependent upon any particular phase of metabolism. 
 
 Both negative and positive phototropism in this species are 
 independent of the " heat rays " of sunlight. 
 
 The position assumed in negative phototropism exposes the 
 color patterns of the wings to fullest illumination, and prob- 
 ably has to do with bringing the sexes together during the 
 breeding season. 
 
 To these may be added other important conclusions of 
 Parker's : 
 
 No light reactions are obtained from the butterfly when 
 shadows are thrown upon any part of the body except the 
 head. \\'hen one eye is painted black the butterfly creeps or 
 flies in circles with the unaffected eye always toward the cen- 
 ter. When both eyes are painted black all phototropic re- 
 sponses cease and the insect flies upward. Butterflies with 
 normal eyes liberated in a perfectly dark room come to rest 
 24 
 
354 ENTOMOLOGY 
 
 near the ceiling. This upward flight in both cases is due to 
 negative geotropism, not to phototropic activity. 
 
 ['. antiopa does not discriminate between lights of greater 
 or less intensity provided they are all of at least moderate 
 intensity and of approximately equal size. ]\ antiopa does 
 discriminate between light derived from a large luminous area 
 and that from a small one, e\'en when the light from these two 
 sources is of equal intensity as it falls on the animal. These 
 butterflies usually fly toward the larger areas of light. This 
 species remains in flight near the ground because it reacts posi- 
 tively to large patches of bright sunlight rather than to small 
 ones, even though the latter, as in the case of the sun, may be 
 much more intense. 
 
 V. antiopa retreats at night and emerg'es in the morning, not 
 so much because of light differences, as because of temperature 
 changes. On warm days it will, however, become quiet or 
 active, without retreating, depending upon a sudden decrease 
 or increase of light. 
 
 The maggots of the muscid Plwnnia rcgina are, as the 
 author has observed, negatively phototropic until full grown, 
 when they become positively phototropic for an hour or less, 
 leave the decaying matter in which they have developed and 
 wriggle along the ground toward the sun; or if the sunlight 
 is diffused by clouds, wander about aimlessly, but at length 
 bury themselves in the ground to pupate. Here the positive 
 phototropism just before pupation is adaptive, as it is in the 
 case of sexually mature ants, which make a nuptial flight into 
 the sunlight when they have acquired wings. The swarming 
 of the honey bee is likewise a case of periodic positive photo- 
 tropism, as Kellogg has observed. 
 
 Though adaptive in their results, these phototropic reac- 
 tions can scarcely be said to be performed on account of 
 their usefulness. They are performed anyway, and may re- 
 sult harmfully, as when they lead a moth into a flame or, to 
 take a more natural example, when they expose an insect to 
 its enemies. 
 
INSECT BEHAVIOR 355 
 
 Phototropism and thermotropism, cither too-cthcr or singly, 
 as Wheeler suggests, may explain the np and d(^wn migration 
 of insects in vegetation. " On cold, cloudy days few insects 
 are taken hecause they lurk quietly near the surface of the soil 
 and about the roots of tlie vegetation, l)ut with an increase in 
 warmth and light they move upwards along' the stems and 
 leaves of the plants, and, if the day be warm and sunny, escape 
 into the air." 
 
 Thermotropism. — Ants are strongly thennotropic; they 
 carry their eggs, larvse and pupae from a cooler to a warmer 
 place or vice versa, and thus secure optimum conditions of 
 temperature. Caterpillars and cockroaches migrate to regions 
 of optimum temperature. 
 
 In thermotropism it appears that the direction of heat rays 
 has little or no effect as compared with differences of intensity. 
 
 Tropisms in General. — Other kinds of tropisms are known, 
 for example, tonotropism, or the control of the direction of 
 locomotion by density, and electrotropism ; not to mention any 
 more. 
 
 All these phenomena are responses of protoplasm to definite 
 stimuli and are almost as inevitable as the response of a needle 
 to a magnet. 
 
 The tropisms of the lower organisms have been experi- 
 mented upon by many skilled investigators, whose results fur- 
 nish a broad basis for the study of the subject in the higher 
 animals — a study which has scarcely begun. Even in the 
 simplest organisms, behavior is the resultant etTect of several 
 or many stimuli acting at once, and the precise effect of each 
 stimulus can be ascertained only by the most guarded kind of 
 experimentation ; while in the higher animals, with their com- 
 plex organization, including specialized sense organs, the study 
 of behavior becomes intricate and cannot be carried on intelli- 
 gently without an extensive knowledge of the l^ehavior of 
 unicellular organisms. The properties of protoplasm are the 
 key to the behavior of organisms, though comparatively little 
 is known as yet in regard to these properties. Furthermore, 
 
356 ENTOMOLOGY 
 
 the study of tropic reactions is complicated by the fact that 
 they are due not only to external stimuli, but also to little- 
 understood internal stimuli, arising from unknown conditions 
 of the alimentary canal, reproductive organs, etc. 
 
 A newly recognized property of protoplasm is that of adap- 
 tation, as manifested in the acclimatization of protoplasm to 
 untoward conditions of temperature, light, contact and other 
 stimuli ; and this adaptation to unusual conditions may take 
 place without the aid of natural selection. 
 
 A tropic reaction occurs, whether it is to prove useful to the 
 organism or not. Thus a lady-bird beetle walks upward, on 
 a branch, on a fence, on one's finger. It walks upward as far 
 as possible and then flies into the air. If it happens to reach 
 the tip of a twig and finds aphids there, the beetle stops and 
 feeds upon them. This adaptive result is in a sense incidental 
 Yet, upon the whole, tropic reactions are wonderfully adaptive 
 in their results. Here natural selection is of special value as 
 affording an explanation of the phenomena. 
 
 As Loeb and Davenport have insisted, the mechanical reac- 
 tions to gravity, light, heat and other influences determine the 
 behavior of the organism. 
 
 2. Instinct 
 
 Insects are eminently instinctive ; though their automatic 
 behavior is often so remarkably successful as to appear ra- 
 tional, instead of purely instinctive. 
 
 Instinct, as distinguished from reason, attains adaptive ends 
 without prevision and without experience. For example, a 
 butterfly selects a particular species of plant upon which to lay 
 her eggs. Caterpillars of the same species construct the same 
 kind of nest, though so isolated from one another as to exclude 
 the possibility of imitation. Every caterpillar that pupates 
 accomplishes the intricate process after the manner of its kind, 
 without the aid of experience. 
 
 Instinctive actions belong to the reflex type — they consist 
 of co-ordinated reflex acts. A complex instinctive action is a 
 
INSECT BEHAVIOR 357 
 
 chain, each hnk of which is a simple reflex act. In fact, no 
 sliarp hne can be drawn between reflexive and instinctive 
 actions. 
 
 Basis of Instinct. — Reflex acts, the elements from which 
 instinctive actions are compounded, are the inevitable responses 
 of particular organs to appropriate stimuli, and involve no 
 volition. The i)resence of an organ normally implies the 
 ability to use it. The newly born butterfly needs no practice 
 preliminary to flight. The process of stinging is entirely 
 reflex ; a decapitated wasp retains the power to sting, directing 
 its weapon toward any part of the body that is irritated; and 
 a freshly emerged wasp, without any practice, performs the 
 stinging movements with greatest precision. 
 
 As Whitman observes, the roots of instincts are to be sought 
 in the constitutional activities of protoplasm. 
 
 Apparent Rationality. — The ostensible rationality of be- 
 havior among insects, as was said, often leads one to attribute 
 intelligence to them, even when there is no evidence of its 
 existence. As an illustration, many plant-eating beetles, when 
 disturbed, habitually drop to the ground and may escape detec- 
 tion by remaining immovable. We cannot, however, believe 
 that these insects " feign death " with any consciousness of 
 the benefit thus to be derived. This act, widespread among 
 animals in general, is instinctive, or reflex, as Whitman main- 
 tains, being, at the same time, one of the simplest, most advan- 
 tageous and deeply seated of all instinctive performances. 
 
 Take the many cases in which an insect lays her eggs upon 
 only one species of plant. The philenor butterfly hunts out 
 Aristolochia, which she cannot taste, in order to serve larvae, 
 of whose existence she can have no foreknowledge. Oviposi- 
 tion is here an instinctive act, not performed until it is evoked 
 by some sort of stimulus — perhaps an olfactory one — from a 
 particular kind of plant. 
 
 Stimuli. — Some determinate sensory stimulus, indeed, is the 
 necessary incentive to any reflex act. The first movements of 
 
358 ENTOMOLOGY 
 
 probably one of temperature. Simple contact with the egg- 
 shell is probably sufficient to stimulate the jaws to work, and 
 the caterpillar eats its way out; yet it cannot foresee that its 
 biting is to result in its liberation. Nor, later on, when vora- 
 ciously devouring leaves, can the caterpillar be supposed to 
 know that it is storing up a reserve supply of food for the dis- 
 tant period of pupation and the subsequent imaginal stage. 
 The ends of these reflex actions are proximate and not ulti- 
 mate, except from the standpoint of higher intelligence. 
 
 Just as simple reflexes link together to form an instinctive 
 action, so may instincts themselves combine. The complex 
 behavior of a solitary wasp is a chain of instincts, as the Peck- 
 hams have shown. All the operations of making the nest, 
 stinging the prey, carrying it to the nest, etc., are performed 
 as a rule in a definite, predicable sequence, and even a slight 
 interference with the normal sequence disconcerts the insect. 
 Just as the performance of one reflex act may serve as the 
 stimulus for the next reflex in order, so the completion of one 
 instinctive action may be in part the stimulus for the next one. 
 
 Modification of Instincts. — An action can be regarded as 
 purely instinctive in its initial performance only, because every 
 subsequent performance may have been modified by experi- 
 ence ; in other words, habits may have been forming and fix- 
 ing, so that the results of instinct become blended with those 
 of experience. J"hus the first flight of a dragon fly is instinc- 
 tive and erratic, but later efforts, aided by experience, are well 
 under control. 
 
 When once shaped by experience, reflex or instinctive ac- 
 tions tend to become intense habits. Thus, certain caterpillars, 
 having eaten all the available leaves of a special kind, will 
 almost invariably die rather than adopt a new food plant, 
 whereas larvae of the same species will eat a strange plant if 
 it is offered to them at birth. An act is strengthened in each 
 repetition by the influence of habit, to the increasing exclusion 
 of other possible modes of action. Many a caterpillar, having 
 eaten its way out of the egg-shell, does not stop eating, but 
 
INSECT BEHAVIOR 359 
 
 consumes the remainder of the shell — a rellex act, started by 
 a stimulus of contact against the jaws and continued until the 
 cessation oi the stimulus, unless some stronger stimulus should 
 intervene. It has been said that the larva eats the remains of 
 the shell because they might betray its presence to its enemies. 
 \\'hether this is true or not, to assume conscious foresight of 
 such a result on the part of an inexperienced caterpillar is worse 
 than unnecessary. 
 
 With insects, as with other animals, many instincts are 
 transitory; even A\hen partially fixed by habit, they are replace- 
 able by stronger instincts. Thus the gregarious habit of lar- 
 vae is finally overpowered by a propensity to wander, which 
 does not mature, however, until the approach of the transfor- 
 mation period. The reproductive instinct is another of those 
 impulses that do not ripen until a certain age in the individual. 
 
 Inflexibility of Instincts. — Broadly speaking, instinctive 
 actions lack individuality — are performed in the same way by 
 every individual of the species. The solitary wasps of the 
 same species are remarkably consistent in architecture, in the 
 selection of a special kind of prey, in the way they sting it, 
 carry it to the nest and dispose of it ; all these operations, more- 
 over, are performed in a sequence that is characteristic of the 
 species. Examples of this so-called inflexibility of instinct are 
 so omnipresent, indeed, that insect behavior as a whole is 
 admitted to be instinctive, or automatic. Insects are capable 
 of an immense number of reflex impulses, ready to act singly 
 or in intricate correlation, upon the recjuisite stimuli from the 
 environment. 
 
 To normal conditions of the environment, the behavior of 
 an insect is accurately adjusted ; in the face of abnormal cir- 
 cumstances, however, demanding the exercise of judgment, 
 most insects are helpless. The specialization to one kind of 
 food, though usually advantageous, is fatal if the supply be- 
 comes insufficient and the larva is unable to adopt another 
 food. A species of Sphc.v habitually drags its grasshopper 
 victim by one antenna. Fabre cut of¥ both antennae and then 
 
36o 
 
 ENTOMOLOGY 
 
 found that the Sphcx, after vain efforts to secure its customary 
 hold, abandoned the prey. Under such unaccustomed condi- 
 tions, insects often show a surprising- stupidity, capable as thev 
 are amid ordinary circumstances. 
 
 Flexibility of Instincts. — Notwithstanding such examples, 
 the common assertion that instincts are absolutely " blind," or 
 inflexible, is incorrect. Instinctive acts are not mechanically 
 invariable, though their variations are so inconspicuous as 
 frequently to escape casual observation. A precise observer 
 can detect individual variations in the performance of any 
 instinctive act — variations analogous to those of structure. 
 
 Fig. 290. 
 
 Ammophila urnaria using a stone to pound down the earth over her nest. Greatly 
 enlarged. — After Peckham, from Bull. Wisconsin Geol. and Nat. Hist. .Survej-. 
 
 To take extreme examples, the Peckhams found that an 
 occasional queen of Polistes fiisca would occupy a comb of the 
 previous year, instead of building a new one ; and that an indi- 
 vidual of Pompilus marginatiis, instead of hiding her captured 
 spider in a hole or imder a lump of earth as usual, hung it up 
 in the fork of a purslane plant. They observed also that one 
 AiiimopJiila, in order to pound down the earth over her nest, 
 actually used a stone, held between the mandibles (Fig. 290). 
 
 While most of the variations that one encounters are small 
 
INSECT BEHAVIOR 3^1 
 
 and, in a sense, accidental, or purposeless, such novel depart- 
 ures as those of the Polisfrs or the Amuiol^Jiihi would seem to 
 denote adaptability. 
 
 Even the despotic power of habit may be ovcrl)orne Ijy indi- 
 vidual adaptability. Among caterpillars that have exhausted 
 their customary food, there are often a few that will adopt a 
 new food plant and survive, leaving' their more conservative 
 fellows to starve. 
 
 As Darwin himself held, the doctrine of natural selection is 
 applicable to instincts as well as structures. All reflex acts are 
 to some extent variable. Disadvantageous reflexes or combi- 
 nations of reflexes eliminate themselves, wdiile advantag"eous 
 ones persist and accumulate. 
 
 Indeed, structures and instincts must frequently have 
 evolved hand in hand. The remarkable protective resemblance 
 of the KaUiina butterfly would be useless, did not the insect 
 instinctively rest among dead leaves of the appropriate kind. 
 
 Origin of Instinct. — There are two leading theories as to 
 the origin of instinct. Lamarck, Romanes and their followers 
 have regarded instinct as inherited habit ; have supposed that 
 instincts have originated by the relegation to the reflex type of 
 actions that at first were rational, and that instincts represent 
 the accumulated results of ancestral experience. This habit 
 theory, however, has little to support it, and assumes the in- 
 heritance of accjuired characters — which has not been proved. 
 
 The selection theory of Darwin, Weismann, Morgan and 
 others has much in its favor. It regards reflex acts as primi- 
 tive, as the raw material from which natural selection, as the 
 chief factor, has effected those combinations that are termed 
 instincts. 
 
 Instincts and Tropisms. — We have already emphasized 
 the fact that an instinct is a reflex act or a combination of 
 reflex acts. The same fact may now be stated in these words : 
 an instinct is a tvopism or a combination of tropisms. The 
 more important of these tropisms have been considered. 
 Whenever possible it is better to discard the ambiguous term 
 
3^2 ENTOMOLOGY 
 
 instinct in favor of such more precise terms as phototropism, 
 geotropism, etc. ; thoug-h the term instinct remains useful as 
 appHed to an action that is the resukant of several tropic 
 responses. 
 
 The modern student of instincts aims to resolve them into 
 their component reflexes and to determine as precisely as pos- 
 sible the influence of each reflex component. Thanks to the 
 labors of a great number of skilled investigators, we are no 
 longer satisfied to class an action as " instinctive " and then 
 dismiss it from thought ; for now we are in a position to 
 analyze the action, and may hope to explain it eventually in 
 terms of the physical and chemical properties of protoplasm. 
 
 3. Intelligence 
 
 Though manifestly dominant, pure instinct fails to account 
 for all insect behavior. The ability of an insect to profit by 
 experience indicates some degree of intelligence. 
 
 Take, for example, the precision with which bees or wasps 
 find their way back to the nest. This is no longer to be 
 accounted for on the assumption of a mysterious " sense of 
 direction," for there is the best of evidence for believing that 
 it depends upon the recognition of surrounding objects. 
 When leaving the nest for the first time, these insects make 
 " locality studies," which are often elaborate. Referring to 
 Sphex ichnciiinonca, the Peckhams write: ''At last, the nest 
 dug, she was ready to go out and seek for her store of pro- 
 vision and now came a most thorough and systematic study 
 of the surroundings. The nests that had been made and then 
 deserted had been left without any circling. Evidently she 
 was conscious of the difference and meant, now, to take all 
 necessary precautions against losing her way. She flew in and 
 out among the plants first in narrow circles near the surface 
 of the ground, and now in wider and wider ones as she rose 
 higher in the air, until at last she took a straight line and 
 disappeared in the distance. The diagram [Fig. 291, A] 
 gives a tracing of her first study preparatory to departure. 
 
INSECT BEHAVIOR 
 
 1>^Z 
 
 \e\'\ often after one thorcmt^'h study of the topog-raphy of her 
 liome has l)een made, a wasp goes away a second time with 
 much less circhng or with none at all. The second diagram 
 [Fig. 291, 5] gives a fair illustration of one of these more 
 hasty departures. . . . 
 
 " If the examination of the objects about the nest makes no 
 impression upon the wasp, or if it is not remembered, she ought 
 not to be inconvenienced nor thrown off her track when weeds 
 and stones are removed and the surface of the ground is 
 smoothed over; but this is just what happens. Aponis fasci- 
 
 FiG. 291. 
 
 Locality studies made by a wasp, Sphe.v iciuieumonea. A, a thorough study; 
 a hasty study; n, nest. After Peckham, from Bull. Wisconsin Geol. and Nat. Hist. 
 Survey. 
 
 atus entirely lost her way when we broke off the leaf that 
 covered her nest, but found it without trouble, when the miss- 
 ing object was replaced. All the species of Ccrccvis were ex- 
 tremely annoyed if we placed any new object near their nest- 
 ing-places. Our Amnio phila refused to make use of her bur- 
 row after w-e had drawn some deep lines in the dust before it. 
 The same annoyance is exhibited when there is any change 
 
3^4 ENTOMOLOGY 
 
 made near the spot upon which the prey of the wasp, whatever 
 it may be, is deposited temporarily." 
 
 If we take, as one criterion of intelHgence. the power to 
 choose between ahernatives, then insects are more intelHgent 
 than is generally admitted. The control of locomotion, the 
 selection of prey, and the avoidance of enemies, as results of 
 experience, indicate powers of discrimination. The power of 
 intercommunication, conceded to exist among the social Hy- 
 menoptera, implies some degree of intelligence. 
 
 If instinct is blind, or mechanical, with no adjustment of 
 means to ends, then a pronounced individuality of action must 
 signify something more than instinct — as in the case of the 
 Ammophila. In regard to a female Poinpiliis scelcstiis, which 
 had dragged a large spider nearly to her nest, the Peckhams 
 observe : " Presently she went to look at her nest and seemed 
 to be struck with a thought that had already occurred to us — 
 that it was decidedly too small to hold the spider. Back she 
 went for another survey of her bulky victim, measured it with 
 her eye, without touching it, drew her conclusions, and at once 
 returned to the nest and began to make it larger. \\'"e have 
 several times seen wasps enlarge their holes when a trial had 
 demonstrated that the spider would not go in, but this seemed 
 a remarkably intelligent use of the comparative faculty." 
 
 From the standpoint of pure instinct, indeed, much of the 
 behavior of the solitary wasps is inexplicable ; while the actions 
 of the social Hymenoptera ha\"e led some of the most critical 
 students to ascribe intelligence to these insects. The activities 
 of the harvesting ants, the military or the slave-holding species, 
 are of such a nature that the possibility of education by experi- 
 ence and instruction is strong, to say the least. In fact, Forel 
 has maintained that a young ant is actually trained to its 
 domestic duties by. its older companions. Miss Enteman, on 
 the contrary, says : '* \\'asps do not imitate one another. In- 
 stinct and individual experience account sufficiently for their 
 powers, and their apparent cooperation is due entirely to the 
 accident of their beinsf born in the same nest." She finds that 
 
INSECT BEHAVIOR 365. 
 
 the worker Polisirs dcies n^t learn to feed the larv.x l)y imi- 
 tating the (|neen. 
 
 It is extremely difficnlt. however, if not impossible, to draw 
 the line between instinct and intelligence ; and in doubtful cases 
 there is a general tendency to exaggerate the importance of 
 intelligence rather than that of instinct. For example, the 
 well-known discrimination on the part of ants between mem- 
 bers of their own colony and those of other colonies, even of 
 the same species, would seem tn impl}- intelligent rec(^gnition. 
 This recognition, h(.)wever, is due simply to a characteristic 
 odor, which is derived from the mother of the community. 
 An ant after being washed receives hostile treatment from 
 others of its own colony; while an alien ant after being 
 smeared with the juices of hostile ants is treated by the latter 
 as a friend. 
 
 Each instance of apparent intelligence must be examined 
 impartially on its own merits. At present it may be said that, 
 while most of the behavior of insects is purely instinctive, there 
 is some reason to believe that at least gleams of intelligence 
 appear in the most specialized Hymenoptera. 
 
 Lack of Rationality. — However intelligent the social Hy- 
 menoptera may be in their way, they show no signs of the 
 power of abstract reasoning. Even ants, according to the 
 experiments of Lubbock, display profound stupidity in the 
 face of novel emergencies wdien they might extricate them- 
 selves by abstract reasoning of the simplest kind. The 
 thoughts of an ant or bee seem to be limited to simple associa- 
 tions of concrete things. Aliss Enteman observed a Polistcs 
 worker which gnawed a piece out of the side of a dead larva 
 of its own kind and, turning, actually offered it as food to the 
 mouth of the same larva. In another instance, a larA'a was 
 attacked and killed, and then offered a piece of its owm body. 
 
 Such examples as these emphasize the strength of the reflex 
 factor in the behavior of insects. Indeed, the basis of all 
 behavior is being sought in the reactions of protoplasm to 
 external stimuli. Possibly even memory, consciousness and 
 other attributes of intelligence will eventually be reduced to 
 this basis, improbable as it may now^ seem. 
 
CHAPTER XII 
 
 DISTRIBUTION 
 
 I. Geographical 
 
 Importance of Dispersion. — Dispersion enables species to 
 mitigate the intense competition and the rigid selection that 
 result from crowded numbers ; hence the tendency to disperse, 
 being self-preservative, has become universal. Some species 
 habitually emigrate in prodigious numbers : the African migra- 
 tory locust, the Rocky JMountain locust, and the milkweed but- 
 terfly, which annually leaves the Northern states for the South 
 in immense swarms, in autumn, and in the following spring 
 straggles back to the North. Vanessa cardiii occasionally mi- 
 grates in immense numbers, as do also Picris, some dragon 
 flies and some beetles, notably Coccinellidje. 
 
 Wide Distribution of Insects. — Insects have been found in 
 almost every latitude and altitude explored by man. Butter- 
 flies and mosquitoes occur beyond the polar circle, the former 
 in Lat. 83° N., the latter in Lat. y2° N., and a species of 
 Emesa closely allied to our common E. longipes is recorded by 
 Whymper from an altitude of 16,500 ft. in Ecuador, where, 
 according to the same traveler, Orthoptera occur at 16,000 
 ft., Pieris xanthodicc ranges above 15,000 ft., and dragon flies. 
 Hymenoptera and scorpions reach a height of 12,000 ft., while 
 twenty-nine species of Lepidoptera range upward of 7,300 
 ft. A ver}' few species of insects inhabit salt water, Halohatcs 
 being found far at sea; some kinds live in arid regions and a 
 few even in hot springs, while caves furnish many peculiar 
 species. In short, insects are the most widely distributed of 
 all animals, excepting Protozoa and possibly Alollusca. 
 
 While all the large orders of insects are world-wide in dis- 
 tribution, the most richly distributed are Coleoptera, Thys- 
 
 366 
 
DISTRIBUTION 367 
 
 aimra and C"olleml)ola, the last two feeding usnall\' upfMi 
 minute particles of organic matter in the soil and l)eing remark- 
 al)ly tolerant of extremes of temperature. The four chief 
 families of butterflies (Kcur the world over, as do several fam- 
 ilies of beetles. Of species that are essentially cosmopolitan 
 we may mention the collembolan Isotoma finictaria, and the 
 butterflies J\iucssa canliii and .liiosia plcvi/^piis, while among 
 beetles no less than one hundred species are cosmopolitan or 
 subcosmopolitan, including Tcncbrio uioUtor, Sihainis siiri- 
 fiaiiiciisis, Dcnncstcs lardarius, Atfagenns picciis and Calandra 
 oryrjcr. The coccinellid genus Seym nits occurs in North 
 America, Europe, Hawaii, Galapagos Islands and New Zea- 
 land, and A)iobiu}]i and Hydrobiiis are distributed as widely. 
 The huge noctuid, Erebus odora, occurring in Brazil on the 
 lowlands, and in Ecuador at an altitude of 10,000 ft., finds its 
 way up into the United States and even into Canada. The 
 chinch bug and many other Central American forms also 
 spread far northward, as described beyond. 
 
 Means of Dispersal. — This exceptional range of insects is 
 due to their exceptional natural advantages for dispersal, chief 
 among which are the power of flight and the ability to be 
 carried by the wind. The migratory locust, Schisfoccrca 
 peregrina, has been found on the wing five hundred miles east 
 of South America. The home of the genus, according to 
 Scudder, is Mexico and Central America, where 23 species are 
 found ; 20 occurring in South America, including the Gala- 
 pagos Islands, 1 1 in the United States and 6 in the West 
 Indies ; and there is every reason to believe that 5^. peregrina 
 — the biblical locust and the only representative of its genus 
 in Africa — crossed over from South America, where it is found 
 indeed at present. Darwin and others have recorded many 
 instances of insects being taken alive far at sea; Trimen men- 
 tions moths and longicorn beetles as occurring 230 miles west 
 of the African coast and Sphinx convolvulus as flying aboard 
 ship 420 miles out. In these instances the insects have usually 
 been assisted or carried by strong' winds, particularly the trade- 
 
368 ENTOMOLOGY 
 
 winds, and oceanic islands have undonbtedly been colonized in 
 this way. On land. Webster has found that the direction in 
 which the Hessian fly spreads is determined largely by the 
 prevailing winds at the time when these delicate insects are on 
 the wing, and that the San Jose scale insect spreads far more 
 rapidly with the prevailing winds than against them, the wind 
 carrying the larvae as if they were so many particles of dust. 
 The pernicious buffalo-gnat of the South emerges from the 
 waters of the bayous and may be carried on a strong wind to 
 appear suddenly in enormous numbers twenty miles distant 
 from its breeding place. Mosquitoes are distributed locally by 
 light breezes, but cling to the herbage during strong winds. 
 
 Ocean currents may carry eggs, larvae or adults on vegetable 
 drift to new places thousands of miles away. Thus the Gulf 
 Stream annually transports thousands of tropical insects to the 
 shores of Great Britain, where they do not survive, however. 
 
 Fresh-water streams convey incalculable numbers of insects 
 in all stages ; and insects as a whole are very tenacious of life, 
 being able to withstand prolonged immersion in water, and 
 even freezing, in many instances, while they can live for a long 
 time without food. 
 
 The universal process of soil-denudation must aid the dif- 
 fusion of insects, slowly but constantly. 
 
 Birds and mammals disseminate various insects in one way 
 or another, while the agency of man is, of course, highly im- 
 portant. Intentionally, he has spread such useful species as 
 the honey bee, the silkworm and certain useful parasites ; inci- 
 dentally he has distributed the San Jose scale, Colorado potato 
 beetle, gypsy moth and many other pests. 
 
 Barriers. — The most important of the mechanical barriers 
 which limit the spread of terrestrial species is evidently the sea. 
 Mountain ranges retard distribution more or less successfully, 
 though a species may spread along one side of a range and 
 sooner or later pass through a break or else around one end. 
 Mountain chains act as barriers, however, chiefly because they 
 present unendurable conditions of climate and vegetation. 
 
DISTRIBUTION 369 
 
 For the same reason deserts are highly effective barriers. In- 
 deed the most important checks upon distribution are those of 
 chmate, and of chmatal factors temperature is the most power- 
 ful. Tropical species, as a rule, cannot survive and reproduce 
 in regions of frost; most of the tropical species which have 
 entered the United States are restricted to its narrow tropical 
 belts (PI. 4). The stages of an insect are frequently so 
 accurately adjusted to particular climatal conditions that an 
 unfamiliar climate deranges the life cycle. Thus many South- 
 ern butterflies find their way every year to the Northern states, 
 only to perish w^ithout reproducing their kind. Insects, how- 
 ever, are more adaptable than most other animals in respect to 
 climate, and frequently follow their food plants into new cli- 
 mates, as in the case of the harlequin cabbage bug, which has 
 pushed north from the tropics to Missouri, southern Illinois 
 and Indiana. 
 
 Humidity ranks next to temperature in the importance of 
 its influence upon the distribution of organisms, but in the case 
 of animals acts for the most part indirectly, by its effects upon 
 vegetation. Thus the effectiveness of an arid region as a bar- 
 rier is due chiefly to the lack of vegetation in consequence of 
 the lack of moisture. Excessive moisture, on the other hand, 
 may act as a barrier. The Rocky Mountain locust, migrating 
 eastward in immense swarms, succumbs in the moist valley of 
 the Mississippi ; the chinch bug is never seriously injurious in 
 wet years. Moisture checks the development of these and 
 other insects in ways as yet unascertained ; possibly it acts indi- 
 rectly by favoring the growth of fungus diseases, to which 
 insects are much subject. 
 
 The absence of proper food is more effective than climate, 
 as a direct check upon the spread of an animal ; food itself being, 
 of course, dependent ultimately upon climatal factors and soil. 
 Many insects, being confined to a single food plant, cannot 
 exist long where this plant does not occur ; but they will follow 
 the plant, as was just said, into new climates; thus Anosia 
 plexippus is following the milkweed over the world. The 
 25 
 
370 ENTOMOLOGY 
 
 butterfly Euphydryas pliccton is remarkably local in its occur- 
 rence, being limited to swamps where its chief food plant 
 {Chelone glabra) grows; and Epidcmia epixanthe is similarly 
 restricted to cranberry bogs, though its food-habits are as yet 
 unknown. 
 
 Former Highways of Distribution. — Many facts of dis- 
 tribution which are inexplicable under the present conditions 
 of topography and climate become intelligible in the light of 
 geological history. The marked similarity between the fauna 
 of Europe and that of North America means community of 
 origin ; and though the Arctic zone now interposes as a barrier, 
 there was once an opportunity for free dispersion when, in the 
 early Pleistocene or late Pliocene, a land connection existed 
 between Asia and North America and a warm climate pre- 
 vailed throughout what is now the Arctic region. 
 
 The extraordinary isolation of the butterfly CEncis sc- 
 midea on mountain summits in New Hampshire and Colo- 
 rado (particularly Mt. Washington, N. H., and Pike's Peak, 
 Col.) is explained by glacial geolog}\ The ancestors of this 
 species, it is thought, were driven southward before an advan- 
 cing ice-sheet and then followed it back as it retreated north- 
 ward, adapted as they were to a rigorously cold climate. 
 Some of these ancestors presumably followed the melting ice 
 up the mountain sides, until they found themselves stranded 
 on the summits. Other individuals, undiverted from the low- 
 lands, followed the retreating glacier into the far north ; and 
 at present there occurs throughout Labrador a species of 
 GEneis which differs but slightly from its lonely ally of the 
 mountain tops. 
 
 Glaciation undoubtedly had a profound effect upon the 
 fauna and flora of North America. " With the slow south- 
 ward advance of the ice, animals were crowded southward; 
 with its recession they advanced again northward to reoccupy 
 the desolated region, until now it has long been repopulated, 
 either with the direct descendants of its former inhabitants or 
 with such limitations to the integritv of the fauna as this inter- 
 
DISTRIBUTION 371 
 
 rnption of local life may have caused." (Scudder.) Probably 
 many species were exterminated and many others became 
 greatly modified, though little is known as to the relationship 
 of the present fauna to the preglacial fauna. " The glacial 
 cold still lingers over the northern part of this continent and 
 our present animals are only a remnant of the rich fauna that 
 existed in former ages, when the magnolia and the sassafras 
 thrived in Greenland." 
 
 Island Faunae. — The al)ility of insects to surmount barriers, 
 under favorable circumstances, is strikingly shown in the col- 
 onization of oceanic islands. Not a few insects, including 
 J\incssa carditi, have found their way to the isolated island 
 of St. Helena. In the Madeira Islands, according to Wollas- 
 ton, there are 580 species of Coleoptera, of which 314 are 
 known to occur in Europe, wdiile all the rest are closely allied 
 to European forms. Subtracting 120 species as having been 
 introduced probably or possibly through the agency of man, 
 there remain 194 that have been introduced by " natural " 
 means. The rest, 266 species, are endemic, though akin to 
 European species. 
 
 The scanty insect fauna of the Galapagos Islands includes 
 twenty species of Orthoptera, which have been studied by 
 Scudder and by Snodgrass. Five of these are cosmopolitan 
 cockroaches, doubtless introduced commercially, and the re- 
 maining fifteen are all " distinctly South and Central American 
 in their affinities." Three of these fifteen are strong-winged 
 species which doubtless arrived by flight from the neighboring 
 mainland; indeed, Scudder records a Schistocerca {S. exsul) 
 as having been taken at sea two hundred miles off the west 
 coast of South America, or nearly half way to the Galapagos 
 Islands. Thirteen of the fifteen are endemic, and five are 
 apterous or subapterous, while a sixth has an apterous female. 
 Apterous insects, noticeably common on wind-swept oceanic 
 islands, may have been carried thither on driftwood, though 
 'i ^s more likely that the apterous condition arose on the 
 islands,' where the better-winded and more venturesome indi- 
 
Z72 ENTOMOLOGY 
 
 viduals may have been constantly swept out to sea and 
 drowned, leaving the more feeble-winged and less venturesome 
 individuals behind, to reproduce their own life-saving pecu- 
 liarities. 
 
 The Coleoptera of the Hawaiian Islands, studied by Dr. 
 Sharp, number 428 species, representing 38 families, and " are 
 mostly small or very minute insects," the few large forms being 
 non-endemic, with little or no doubt ; 352 species are at present 
 known only from this archipelago. Dr. Sharp distinguishes 
 three elements in the fauna : " First, species that have been 
 introduced, in all probability comparatively recently, by artifi- 
 cial means, such as with provisions, stores, building timber, 
 ballast, or growing plants ; many of these species are nearly 
 cosmopolitan. Second, species that have arrived in the islands, 
 and have become more or less completely naturalized ; they are 
 most of them known to be wood- or bark-beetles, but some that 
 are not so may have* come with the earth adhering to the roots 
 of floating trees; a few, such as the Dytiscid?e, or water beetles, 
 may possibly have been introduced by violent winds. Third, 
 after making every allowance for introduction by these artifi- 
 cial and natural methods, there still remains a large portion 
 standing out in striking contrast with the others, which we 
 are justified in considering strictly endemic or autochthonous." 
 Among the introduced genera- are Coccinclla, Dcrmcstcs, 
 Aphodins, Buprestis, Ptiniis and Ccrauihyx. The immigrant 
 longicorns appear to have been derived " from the nearest 
 lands in various directions " — the Philippine Islands, tropical 
 America and the Polynesian Islands — and the same conclusion 
 will probably be found to hold for the other immigrants, when 
 their general distribution shall have been sufficiently studied. 
 The endemic species number 214, or exactly half the total num- 
 ber of species, and are distributed among 9 families, as follows : 
 

 
 DISTRIBUTION 
 
 
 ?>7Z 
 
 Families. 
 
 
 Species. 
 
 Genera. 
 
 Endemic Genera. 
 
 Carabidae, 
 
 
 51 
 
 7 
 
 7 
 
 Staphylinidae, 
 
 
 19 
 
 3 
 
 I 
 
 Nitidulidre, 
 
 
 38 
 
 2 
 
 I 
 
 Elatcridse, 
 
 
 7 
 
 I 
 
 I 
 
 Ptinidae (Anobiini) 
 
 19 
 
 3 
 
 3 
 
 Cioidae, 
 
 
 19 
 
 I 
 
 
 
 Aglycyderidse, 
 
 
 30 
 
 I 
 
 I 
 
 Curculionidse 
 
 (Cossonini), 21 
 
 3 
 
 3 
 
 Cerambycidae, 
 
 
 10 
 
 I 
 
 
 Sharp writes : " I think it may be looked on as certain that 
 these islands are the home of a large number of peculiar spe- 
 cies not at present existing- elsewhere, and if so it follows that 
 either they must have existed formerly elsewhere and migrated 
 to the islands, and since have become extinct in their original 
 homes, or that they must have been produced within the 
 islands. This last seems the simpler and more probable sup- 
 position, and it appears highly probable that there has been a 
 large amount of endemic evolution within the limits of these 
 isolated islands." 
 
 The parasitic Hymenoptera of Hawaii, according to Ash- 
 mead, number 14 families, 69 genera and 128 species; only 
 ■eleven genera are endemic and most of the other genera are 
 represented in nearly all the known faunje of the earth. Ash- 
 mead concurs in the view that the Hawaiian fauna was origi- 
 nally derived from the Australasian fauna — the view held by 
 all the specialists who have studied Hawaiian insects. 
 
 Geographical Varieties. — Darwin found that wide-ranging 
 species are as a rule highly variable. The cosmopolitan but- 
 terfly Vanessa cardiii presents striking variations in different 
 parts of the earth, largely on account of climatal differences, 
 as is indicated by the temperature experiments of several inves- 
 tigators. Standfuss exposed German pup?e of this insect to 
 cold, and obtained thereby a dark variety such as occurs in Lap- 
 land ; and by the influence of warmth, obtained a very pale form 
 such as occurs normally in the tropics only. Our Cyaniris 
 pseiidargiolus, which ranges from Alaska into Mexico and 
 
374 ENTOMOLOGY 
 
 from the Pacific to the Atlantic, exhibits many geographical 
 varieties, some of which are clearly due to temperature, as 
 experiments have shown. 
 
 Geographical isolation is often followed by changes in the 
 specific characters of an organism, as witness the endemic 
 species and varieties of oceanic islands. Even in the same 
 archipelago, the different islands may be characterized by dif- 
 ferent varieties of one and the same species, or even by differ- 
 ent but closely allied species of the same genus. Thus Darwin 
 and Alexander Agassiz found that in the Galapagos Islands 
 each island had its own species of Tropidiirus (a lizard) and 
 had only one species, with almost no exceptions. The same 
 phenomenon occurs in the two Galapagan species of Schisto- 
 cerca — 6". melanoccra and vS'. litcrosa. In mclanoccra, as 
 Scudder discovered, " Three or four distinct types are becom- 
 ing gradually differentiated on the eight [now ten] islands 
 from which, they are known." Snodgrass, who has recently 
 made important additions to Scudder's account, says, in regard 
 to the two species, " The specimens from the different islands 
 show striking, though, in most cases, slight differences distin- 
 guishing the individuals of each island as a race, from those 
 inhabiting any other island. There are two exceptions. 
 Abingdon and Bindloe have the same form, and Albemarle 
 supports at least two races." Each of these two species pre- 
 sents no less than five racial types, to which distinctive names 
 have been applied. Though the relationships and evolution of 
 these races have been ably discussed by Snodgrass, definite 
 conclusions upon these subjects are still needed. Isolation in 
 general we have considered briefly in Chapter VII. 
 
 Faunal Realms. — The general distribution of life is such 
 that naturalists divide the earth into several realms, each of 
 which has its characteristic fauna and flora. As to the precise 
 boundaries of these faunal realms, zoologists do not all agree, 
 owing chiefly to the fact that faunje overlap one another to 
 such an extent as to render their exact separation more or less 
 arbitrary. Five realms, at least, are generally recognized : 
 
DISTRIBUTION 375 
 
 Holarctic, Neotropical, Ethiopian, Oriental and Australian 
 
 (PI- 3)- 
 
 The Holarctic realm comprises the whole of Europe, North- 
 ern Africa as far south as the Sahara, Asia down to the Hima- 
 layas, and North America down to Mexico. Though the 
 fauuce of all these areas are fundamentally alike (as Merriam 
 and other authorities maintain), it is often convenient to 
 divide the Holarctic into two parts : the Palccarctic, including 
 Europe and most of temperate Asia, being limited roughly by 
 the Tropic of Cancer; and the Ncarcfic, occupying almost the 
 entire continent of North America, including Greenland. The 
 northern portion of the Holarctic realm forms a circumpolar 
 l)elt with a remarkable homogeneous fauna and flora ; there- 
 fore some authors distinguish an Arctic realm, limited by the 
 isotherm of 32°, which marks very closely the tree-limit. 
 
 The boreal insects of Eurasia and North America are strik- 
 ingly alike. Dr. Hamilton has catalogued nearly six hundred 
 species of beetles as being holarctic in distribution ; five hun- 
 dred of these are common to Europe, Asia and North America, 
 and the remainder are known to occur in North America and 
 also in Europe or Asia ; one hundred are cosmopolitan or sub- 
 cosmopolitan, to be sure, but fifty of these are probably hol- 
 arctic in origin, for example — Dcnucstcs lardarius and Tene- 
 hrio molitor. Of butterflies, out of some two hundred and 
 fifty species that are found in the United States east of the 
 Rocky ]\Iountains, scarcely more than a dozen occur also in 
 the old world. North of the United States, however, as 
 Scudder finds, no less than thirteen genera are represented in 
 the old world by the same or by allied species. 
 
 The Neotropical realm embraces South America, Central 
 America, the West Indies and the coasts of Mexico ; Mexico 
 being for the most part a transition tract between the Neo- 
 tropical and the Nearctic. The richest butterfly fauna in the 
 world is found in tropical South America. To this region are 
 restricted, almost without exception, the Euploeinse and 
 Lemoniinse and over ninety-nine per cent, of the Libytheinse; 
 
376 ENTOMOLOGY 
 
 here the Hehconiiclfc and PapiHonidae attain their highest 
 development, as do also the Cerambycid?e, or longicorn beetles. 
 
 The Ethiopian realm consists of Africa south of the Sahara, 
 Southern Arabia and Madagascar ; though some prefer to 
 regard Madagascar as a distinct realm, the Lemiirian. Ac- 
 cording to Wallace, the Ethiopian realm has seventy-five pecu- 
 liar genera of Carabidae and is marvelously rich in Cetoniidse 
 and Lycaenidae. 
 
 The Oriental realm includes India, Ceylon, Tropical China, 
 and the Western Malay Islands. In the richness of its insect 
 fauna, this realm vies with the Neotropical. Danaid?e and 
 Papilionidae are abundant, while the genus Morpho is repre- 
 sented by some forty species ; of Coleoptera, Buprestidse are 
 important and Lucanidse especially so. 
 
 The Australian realm embodies Australia, New Zealand, the 
 Eastern Malay Islands and Polynesia. Buprestidae are here 
 represented by forty-seven genera, of which twenty are pecu- 
 liar; against this showing, the Oriental has forty-one genera 
 and the Neotropical thirty-nine (W^allace). Strong affinities 
 are said to exist between the Australian and Neotropical insect 
 faunae. 
 
 Life Zones of North America. — Merriam, the chief au- 
 thority upon the subject, says : *' The continent of North 
 America may be divided, according to the distribution of its 
 animals and plants, into three primary transcontinental regions 
 — Boreal, Austral and Tropical." (PI. 4.) 
 
 The Boreal region covers the northern part of the continent 
 to about the northern boundary of the United States and con- 
 tinues southward along the higher portions of the mountain 
 ranges. This region is divided into three transcontinental 
 zones: (i) the Arctic- Alpine, lying above the limits of tree 
 growth, in latitude or altitude; (2) the Hudsonian, compris- 
 ing the northern part of the great transcontinental coniferous 
 forest and the upper timbered slopes of the highest mountains 
 of the United States and Mexico; (3) the Canadian, covering 
 the remainder of the Boreal region. The butterfly Erynnis 
 manitoha (Fig. 292) is strictly boreal in distribution. 
 
DISTRIBUTION 
 
 377 
 
 The Austral region " covers the \\h()le of the United States 
 and Mexico, except the Boreal mountains and tlie TroiMcal 
 lowlands." It comprises three transcontinental l)elts : (i) the 
 Transition zone, in which the Boreal and the Austral overlap; 
 (2) the Upper Austral; (3) tha LoK'cr Austral. The butter- 
 
 FlG. 202. 
 
 P'lG. 293. 
 
 
 "TP^g^ 
 
 
 n— tm35C 
 
 vA 
 
 ^)3S^ 
 
 ^\\ 
 
 \/^^ \) 
 
 Distribution of Erynnis manitoba, a 
 butterfly restricted to subarctic and sub- 
 alpine regions. — After Scudder. 
 
 Distribution in the United States of 
 Etidamits protciis, primarily a tropical 
 butterfly. — After Scudder. 
 
 tiy Eudainus protcus (Fig. 293) is restricted, generally speak- 
 ing, to the Tropical region and the warmer and more humid 
 portions of the Austral. 
 
 The Tropical region covers the southern extremity of 
 Florida and of Lower CaHfornia, most of Central America and 
 a narrow strip along the two coasts of Mexico, the western 
 strip extending up into California and Arizona. 
 
 These divisions are based primarily upon the distribution of 
 mammals, birds and plants, and the three primary divisions 
 serve almost equally well for insects also. In regard to the 
 zones, however^ not so much can be said — for insects are to a 
 high degree independent of minor differences of climate. 
 Many instances of this are given beyond. 
 
 The insect fauna of the United States is upon the whole a 
 heterogeneous assemblage of species derived from several 
 sources, and the foreign element of this fauna we shall con- 
 sider at some length. 
 
 Paths of Diffusion in North America. — It may be laid 
 down as a general rule that every species tends to spread in 
 
3/8 ENTOMOLOGY 
 
 all directions and does so spread until its further progress is 
 prevented, in one way or another. The paths along which a 
 species spreads are determined, then, by the absence of barri- 
 ers. The diffusion of insects in our own country has received 
 much attention from entomologists, especially in the case of 
 such insects as are important from an economic standpoint. 
 The accessions to our insect fauna have arrived chiefly from 
 Asia, Central and South America, and Europe. 
 
 Webster, our foremost student of this subject, to whom the 
 author is indebted for most of his facts, names four paths along 
 which insects have made their way into the United States : 
 ( I ) Northwest — Northern Asia into Alaska and thence south 
 and east; (2) Southwest — Central America through Mexico; 
 (3) Southeast — AVest Indies into Florida; (4) Eastern — from 
 Europe, commercially. 
 
 Northwest. — The northern parts of Europe, Asia and 
 North America have in common very many identical or closely 
 allied species, whose distribution is accounted for if, as geol- 
 ogists assure us, Asia and North America were once con- 
 nected, at a time when a subtropical climate prevailed within 
 the Arctic Circle; in fact, the distribution is scarcely explic- 
 able upon any other theory. Curiously enough, the trend of 
 diffusion seems to have been from Asia into North America 
 and rarely the reverse, so far as can be inferred. 
 
 Coccinella qninquenotata, occurring in Siberia and Alaska, 
 has spread to Hudson Bay, Greenland, Kansas, Utah, Califor- 
 nia and Mexico ; while C. sanguinea, well known in Europe 
 and Asia, ranges from Alaska to Patagonia ; and Megilla iiiac- 
 ulata from Vancouver and Canada to Chile. About six hun- 
 dred species of beetles are holarctic in distribution, as was 
 mentioned. Some of them inhabit different climatal regions 
 in different parts of their range; thus Melasoma (Lina) lap- 
 pon'iea in the Old World " occurs only in the high north and 
 on high mountain ranges, whereas in North America it ex- 
 tends to the extreme southern portion of the country," being 
 widely diffused over the lowlands (Schwarz). Similarly, 
 
DISTRIBUTION 379 
 
 Silpha lappoiiica is strictly arctic in Europe, but is distrilmted 
 over mi^st of North America; Silpha opaca, on the contrary, 
 is common all over Europe, but is strictly arctic in North 
 America. Silplia atrata, common throug-hout Europe and 
 western Siberia, was introduced into North America, but failed 
 to establish itself. 
 
 Southwest. — \>ry many species have come to us from Cen- 
 tral America and even from South America. South America 
 appears to be the home of the genus Halisidota, according to 
 Webster, who has traced several of our North American spe- 
 cies as offshoots of South American forms. Many of our 
 species may be traced back to Yucatan. //. ciiictipcs ranges 
 from South America to Texas and Elorida ; H. tcsscUaris has 
 spread northward from Central America and now occurs over 
 the middle and eastern United States, while a form closely like 
 fesscllaris ranges from Argentina to Costa Rica ; H. carycc 
 follows tessellaris, and appears to have branched in Central 
 America, giving ofif H. agassizii, which extends northward 
 into California. Similarly in the case of the Colorado potato 
 beetle {Lcpuuotavsa dcccinUncata) and its relatives. Accord- 
 ing to Tower, the parent form, L. undcccuiUncata, seems to 
 have arisen in the northern part of South America, to have 
 migrated northward and, in the diversified Mexican region, to 
 have split into several racial varieties. The parent form 
 grades into L. mnltiUncata of the Mexican table lands, which 
 in turn, in the northern part of the Mexican plateau, passes 
 imperceptibly into L. dcccmlincata, which last species has 
 spread northward along the eastern slope of the western high- 
 lands, west of the arid region. In the lower part of the Mex- 
 ican region the parent form may be traced into L. juncta, 
 which has spread along the low humid Gulf Coast, up the Miss- 
 issippi valley to southern Illinois, and along the Gulf Coast 
 and up the Atlantic coast to Maryland, Delaware and New 
 Jersey. In general, the mountains of Central America and 
 Mexico and the plateau of Mexico have been barriers to the 
 northward spread of many species, which have reached the 
 
380 ENTOMOLOGY 
 
 United States by passing to the east or to the west of these 
 barriers, in the former case skirting the Gulf of Mexico and 
 spreading northward along the Mississippi valley or along the 
 Atlantic coast, in the latter event traveling along the Pacific 
 coast to California and other Western states. Not a few spe- 
 cies, however, have made their way from the Mexican plateau 
 into New Mexico and Arizona ; this is true of many Sphin- 
 gidas. The butterfly Anosia herenice ranges from South 
 America into New Mexico, Arizona and Colorado ; while many 
 of the Libytheidae have entered Arizona and neighboring states 
 from Mexico. The chrysomelid genus Diabrotica is almost 
 exclusively confined to the western hemisphere and its home 
 is clearly in South America, where no less than 367 species are 
 found. About 100 species occur in Venezuela and Colombia, 
 " of which 1 1 extend into Guatemala, 8 into Mexico, and i 
 into the United States." We have 18 species of Diabrotica, 
 almost all of which can be traced back to Mexico, and several 
 of them — as the common D. longicornis — to Central America. 
 " The common Dyiiasfcs fityus occurs from Brazil through 
 Central America and Mexico, and in the United States from 
 Texas to Illinois and east to southern New York and New 
 England." Erebus odora ranges from Ecuador and Brazil to 
 Colorado, Illinois, Ohio, New England and into Canada, 
 though it is not known to breed in North America, being in 
 fact a rare visitor in our northern states. 
 
 Southeast. — Many South American species have made their 
 way into southern and western Florida by way of the West 
 Indies, while some subtropical species have reached Florida 
 probably by following around the Gulf coast. The semi- 
 tropical insect fauna of southern and southwestern Florida, 
 including about 300 specimens of Coleoptera, according to 
 Schwarz, is entirely of West Indian and Central American 
 origin, the species having been introduced with their food 
 plants, chiefly by the Gulf Stream, but also by flight, as in the 
 case of Sphingidse. Ninety-five species of Hemiptera collected 
 in extreme southern Florida by Schwarz and studied by Uhler 
 
DISTRIBUTION 38 1 
 
 are distinctly Central American and West Indian in their 
 affinities. Indeed Uhler is inclined to believe that the principal 
 portion of the Ilemiptera of the United States has been derived 
 from the region of Central America and Mexico. 
 
 Eastern. — On the Atlantic coast are many European species 
 of insects which ha^•e arri\-ed throug'h the ag-encv of man. 
 Most of them have not as }et passed the Appalachian moun- 
 tain system, but some have worked their way inland. Thus 
 the common cabbage butterfly (Pieris rapcc), first noticed in 
 Quebec about i860, was found in the northern parts of Maine, 
 New Hampshire and Vermont five or six years later, was 
 established in those states by 1867, entered New York in 1868 
 and then Ohio. Aphodius fossor followed much the same 
 course from New York into northeastern Ohio, as did also the 
 asparagus beetle (Crioccris asparagi), the clover leaf weevil 
 (PhytoJionins puncfatiis) , the clover root borer (Hylostcs 
 ohscurus) and other species. In short, as Webster has pointed 
 out. New York offers a natural g'ateway through which species 
 introduced from Europe spread westward, passing either to the 
 north or to the south of Lake Erie. 
 
 Inland Distribution. — Pieris rapcc, the spread of which in 
 North America has been thoroughly traced by Scudder, 
 reached northern New York in 1868 (as above), but appears 
 to have been independently introduced into New^ Jersey in 
 1868, whence it reached eastern New York again in 1870; it 
 was seen in northeastern Ohio in 1873, Chicago 1875, Iowa 
 1878, Minnesota 1880, Colorado 1886, and has extended as 
 far south as northern Florida, but is apparently unable to make 
 its way down into the peninsula. 
 
 Crioccris asparagi, another native of Europe, became con- 
 spicuous in Long Island in 1856, spread southward to Virginia 
 and westward to Ohio, where it was taken in 1886; it occurs 
 now in Illinois. This insect, as Howard observes, flies read- 
 ily, and may be introduced commercially in the egg or larval 
 stage on bunches of asparagus. 
 
 Cryptorhyiichits hipatJii, a beetle destructive to willows and 
 
382 ENTOMOLOGY 
 
 poplars, and common in Europe, Siberia and Japan, was found 
 in New Jersey in 1882 and in New York in 1896, though 
 known for many years previously in Massachusetts. It be- 
 came noticeable in Ohio in 1901, and is steadily extending its 
 ravages, being reported recently from Minnesota. 
 
 From Colorado the well-known potato beetle (Leptinotarsa 
 dcccinUncata) has worked eastward since 1840, reaching the 
 Atlantic coast within twenty years, and has even made its way 
 several times into Great Britain, only to be stamped out with 
 commendable energy. The box-elder bug (Leptocoris trk'it- 
 tatiis) is similarly working eastward, having now reached 
 Indiana. The Rocky Mountain locust periodically migrates 
 eastward, but meets a check in the moist valley of the Missis- 
 sippi, as has been said. 
 
 The chinch bug (Blissiis leucopterus), the distribution of 
 which has been traced by Webster, has spread from Central 
 America and Mexico northward along the Gulf coast into the 
 United States, following three paths: (i) Along the Atlantic 
 coast to Cape Breton; (2) along the Mississippi valley and 
 northward into Manitoba; (3) along the western coast of Cen- 
 tral America and Mexico into California and other Western 
 states. Everywhere this insect has found wild grasses upon 
 which to feed, but has readily forsaken these for cultivated 
 grasses upon occasion. The harlequin cabbage bug {Murgan- 
 tia hisfrionica) has spread from Central America into Califor- 
 nia and Nevada, and has steadily progressed in the Mississippi 
 basin as far north as Illinois, Indiana and Ohio, though it 
 appears to be unable to maintain itself in the northern parts 
 of these states. This insect required about twenty-five years 
 to pass from Louisiana (1864) to Ohio, spreading through its 
 own efforts and not commercially to any great extent. 
 
 Every year some of the southern butterflies reach the North- 
 ern states, where they die without finding a food plant, or else 
 maintain a precarious existence. Thus Iphiclides ajax occa- 
 sionally reaches Massachusetts as a visitor and a visitor only ; 
 Lccrtias philcnor, however, finds a limited amount of food in 
 
DISTRIBUTION 383 
 
 the cultivated ArisfolocJiia. P. tlioas, one of the pests of 
 the orange tree in the South, is highly prized as a rarity by 
 New England collectors and is able to perpetuate itself in the 
 Middle States on the prickly ash (Xaiithoxyluin). The 
 strong-winged grasshopper, Schistocerca amcricana, l)elonging 
 to a genus the center of whose dispersion is tropical America, 
 ranges freely over the interior of North America, sometimes 
 in great swarms, and its nymphs are able to survive in mode- 
 rate numbers in the southern parts of Illinois, Ohio and other 
 states of as high latitude, while the adults occasionally reach 
 Ontario, Canada. 
 
 Many species are now so widely distributed that their for- 
 mer paths of ditifusion can no longer be ascertained. The 
 army worm {Hcliopliila unipiiiicta) , feeding on grasses, and 
 occurring all over the United States south of Lat. 44° N., is 
 found also in Central America, throughout South America, 
 and in Europe, Africa, Japan, China, India, etc. ; in short, it 
 occurs in all except the coldest parts of the earth, and where 
 it originated no one knows. 
 
 Determination of Centers of Dispersal. — In accounting 
 for the present distribution of life, naturalists employ several 
 kinds of evidence. Adams recognizes ten criteria, aside from 
 palaeontological evidence, for determining centers of dispersal : 
 
 1. Location of greatest differentiation of a type. 
 
 2. Location of dominance or great abundance of individuals. 
 
 3. Location of S3mthetic or closely related forms (Allen). 
 
 4. Location of maximum size of individuals (Ridgway- 
 Allen). 
 
 5. Location of greatest productiveness and its relative sta- 
 bility, in crops (Hyde). 
 
 6. Continuity and convergence of lines of dispersal. 
 
 7. Location of least dependence upon a restricted habitat. 
 
 8. Continuity and directness of individual variations or 
 modifications radiatine from the center of oriein alone: the 
 
 gn 
 
 highways of dispersal. 
 
 9. Direction indicated by biogeographical affinities. 
 
3^4 ENTOMOLOGY 
 
 lo. Direction indicated by the annual migration routes, in 
 birds (Palmen). 
 
 2. Geological 
 
 Means of Fossilization. — Abundant as insects are at pres- 
 ent, they are comparatively rare as fossils, the fossil species 
 forming but one per cent, of the total number of described 
 species of insects. The absence of insect remains in sedimen- 
 tary rocks of marine origin is explained by the fact that almost 
 no insects inhabit salt water ; and terrestrial forms in general 
 are ill-adapted for fossilization. The hosts of insects that die 
 each year leave remarkably few traces in the soil, owing per- 
 haps, in great measure, to the dissolution of chitin in the pres- 
 ence of moisture. 
 
 ]\Iost of the fossil insects that are known have been found 
 in- vegetable accumulations such as coal, peat and lignite, or 
 else in ancient fresh-water basins, where the insects were prob- 
 ably drowned and rapidly imbedded. At present, enormous 
 numbers of insects are sometimes cast upon the shores of our 
 great lakes — a phenomenon which helps to explain the profu- 
 sion of fossil forms found in some of the ancient lake basins. 
 
 Insects in rich variety have been preserved in amber, the 
 fossilized resin of coniferous trees. This substance, as it 
 exuded, must have entangled and enveloped insect visitors just 
 as it does at present. ]\Iany of these amber insects are ex- 
 cjuisitely preserved, as if sealed in glass. Copal, a transparent, 
 amber-like resin from various tropical trees, particularly Legu- 
 minosje, has also yielded many interesting insects. 
 
 Ill-adapted as insects are by organization and habit for the 
 commoner methods of fossilization, the number of fossil spe- 
 cies already described is no less than three thousand. 
 
 Localities for Fossil Insects. — The Devonian of New 
 Brunswick has furnished a few forms, found near St. John, in 
 a small ledge that outcrops between tide-marks ; these forms, 
 though few, are of extraordinary interest, as will be seen. 
 
 For Carboniferous species, Commentry in France is a noted 
 locality, through the admirable researches of Brongniart, who 
 
DISTRIBUTION 
 
 385 
 
 Fig, 
 
 descriljed from there 97 species of 48 genera, representing- 12 
 families or higher groups, lo of which are regarded as extinct; 
 without including many hundred specimens of cockroaches 
 which he found hut did not study. In this country, many 
 species have heen found in the coal fields of Illinois, Nova 
 Scotia, Rhode Island, Pennsylvania and Ohio. 
 
 Many fine fossils of the Jurassic period have heen found in 
 the lithographic limestones of Bavaria; 143 species from the 
 Lias — four fifths of them heetles — were studied hy Heer. 
 
 The Tertiary period has furnished the majority of fossil 
 specimens. To the Oligocene helong the amher insects, of 
 which 900 species are known from Baltic amber alone, and to 
 the same epoch are ascribed the deposits of Florissant and 
 White River in Colorado and of Green River, Wyoming. 
 These localities — the richest in the world — have been made 
 famous by the monumental works of Scudder. At Florissant 
 there is an extinct lake, in the bed of 
 which, entombed in shales derived 
 from volcanic sand and ash, the re- 
 mains of insects are found in aston- 
 ishing profusion. For Miocene 
 forms, of which 1,550 European spe- 
 cies are known, the CEningen beds of 
 Bavaria are celebrated as having furnished 844 species, des- 
 cribed by the illustrious Heer. 
 
 Pleistocene species are supplied by the peats of France and 
 Europe, the lignites of Bavaria, and the interglacial clays of 
 Switzerland and Ontario, Canada. 
 
 Silurian and Devonian, — The oldest fossil insect known 
 consists of a single hemipterous wing, Protociiiic.v, from the 
 Lower Silurian of Sweden. Next in age comes a wing, 
 Palcuoblaffiiia (Fig. 294), of doubtful position,^ from the 
 Middle Silurian of France. Following these are six speci- 
 mens of as many remarkable species from the Devonian shales 
 
 ^ There is some evidence, it should be said, that this species is not an 
 insect. Handhrsch denies also that Protocimcx is an insect. 
 
 Palccohlattina douvillci, iiatur 
 size. — After Brongniart. 
 
386 
 
 ENTOMOLOGY 
 
 of New Brunswick. The specimens, to be sure, are nothing- 
 but broken wings, yet these few fragments, interpreted by Dr. 
 Scuckler. are rich in meaning. All are neuropteroid, but they 
 cannot be classified satisfactorily with recent forms on account 
 
 Fig. 295. 
 
 Platcpl 
 
 \fter ScuDDER. 
 
 of being" highly synthetic in structure. Thus Platcphciiicra 
 aiitiqiia (Fig. 295). though essentially a May fly of gigantic 
 proportions (spreading probably 135 mm.), has an odonate 
 type of reticulation; while Xcnoncum (Fig. 296) combines 
 characters which are now distributed among Ephemeridse, 
 Sialidje. Rhaphidiidae, Coniopterygid?e, and other families, 
 besides being in many respects unique. These Devonian forms 
 
 Xenoneura antiquornm, five times 
 
 After ScuDDER. 
 
 attained huge dimensions as compared with their recent repre- 
 sentatives ; Gcrcphcincra, for example, had an estimated ex- 
 panse of 175 millimeters. 
 
 Carboniferous. — The Carboniferous age, with its luxuriant 
 vegetation, is marked by the appearance of insects in great 
 
DISTRIBUTION 
 
 387 
 
 number and variety, still restricted, however, to the more 
 generalized orders. The dominance of cockroaches in the 
 Carboniferous is especially noteworthy, no less than 200 Palcco- 
 zoic species being- known from Eu- 
 rope and North America. These '' "'^''' 
 ancient roaches (Fig. 297) differed 
 from their modern descendants in 
 the similarity of the two pairs of 
 wings, which were alike in form. 
 size, transparency and g-eneral neu- 
 ration. with six principal ner\-ures 
 in each wing; while in recent cock- 
 roaches the front wings have be- 
 come tegmina, with certain of the 
 veins always blended together, 
 though the hind wings have retained 
 their primitive characteristics with a 
 few modifications, such as the ex- 
 pansion of the anal area. Car- 
 boniferous cockroaches furthermore 
 exhibit ovipositors, straight, slender, 
 and half as long again as the abdo- 
 men — organs which do not exist in 
 recent species. 
 
 Lithomantis (Fig. 298), a remarkable form from Scotland, 
 possessed in addition to its four large neuropteroid wings, 
 a pair of prothoracic wing-like appendages which, provided 
 they may be regarded' as homologous with wings, represent 
 a third pair, either atrophied or undeveloped — a condition 
 which is never found today, unless the patagia of Lepidoptera 
 represent wings, which is unlikely. 
 
 From the rich deposits of Commentry, Brongniart has des- 
 cribed several forms of striking interest. Dictyoneura is a Car- 
 boniferous genus with neuropteroid wings and an orthopteroid 
 body, having, in common with several contemporary genera, 
 strong isopteran affinities. Corydaloides scudderi, a phasmid, 
 
 Efoblattina ma::ona, a Car- 
 boniferous cockroach from 
 Illinois. Twice natural size. 
 — After ScuDDER in Miall and 
 Denny. 
 
388 
 
 ENTOMOLOGY 
 
 has an alar expanse of twenty-eight inches. The Carbonife- 
 rons prototypes of oiir Odonata were gigantic l3eside their 
 modern descendants, one of them (il/t^o^a;/c'//;77 ) having a spread 
 of over two feet ; they were more generahzed in strnctnre than 
 recent Odonata, presenting a much simpler type of neuration 
 and less differentiation of the segments of the thorax. The 
 Carboniferous precursors of our May flies attained a high 
 
 Fig. 298. 
 
 Lithomantis carbonarius, showing prothoracic appendages. Two thirds natural size.- 
 After WooDW.\RD. 
 
 development in number and variety ; in fact, the Ephemeridse, 
 like the Blattidse, achieved their maximum development ages 
 ago, wdien they attained an importance strongly contrasting 
 with their present meager representation. 
 
 The Permian has supplied a remarkable genus Eugcrcon 
 (Fig. 299) with hemipterous mouth parts associated with fili- 
 form antennae and orthopteroid wings. The earliest uncjues- 
 tionable traces of insects with an indirect metamorphosis are 
 found in the Permian of Bohemia, in the shape of caddis worm 
 cases. 
 
 Triassic. — Triassic cockroaches present interesting stages 
 in the evolution of their familv. Through these ]\Iesozoic 
 
DISTRIBUTION 
 
 389 
 
 Species, the continuity between Paheozoic and recent cock- 
 roaches is clearly established — which can be said of no other 
 insects ; and in fact of no other animals, the only comparable 
 cases being those of the horse and the molluscan oenus Planor- 
 his. In the Triassic period occur the first fossils that can be 
 
 Fig 
 
 Eiigcrcon bockingi. Three quarter 
 
 size. — After Dohrn. 
 
 referred indisputably to Coleoptera and Hymenoptera, the lat- 
 ter order being represented first, as it happens, by some of 
 its most specialized members, namely ants. 
 
 Jurassic. — At length, in the Jurassic, all the large orders 
 except Lepidoptera occur; Diptera appear for the first time, 
 and Odonata are represented by many well-preserved speci- 
 mens, while the Liassic Coleoptera studied by Heer number 
 over one hundred species. The Cretaceous has yielded but 
 few^ insects, as might be expected. 
 
 Tertiary. — In the rich Tertiary deposits all orders of insects 
 occur. Baltic amber has yielded Collembola, some remarkable 
 Psocidae, many Diptera, and ants in abundance. Of 844 spe- 
 
390 
 
 ENTOMOLOGY 
 
 cies taken from the noted Miocene beds of CEning-en, nearly 
 one half were Coleoptera, followed by neuropteroid forms 
 (seventeen per cent.) and Hymenoptera (fourteen per cent.) ; 
 ants were twice as numerous in species as they are at present 
 in Europe. Almost half the known species of fossil insects 
 have been described from the Miocene of Europe. To the 
 Miocene belongs the indusial limestone of Auvergne, France, 
 where extensive beds — in some places two or three meters 
 deep — consist for the most part of the calcified larval cases of 
 caddis flies. 
 
 At Florissant, as contrasted with CEningen by Scudder, 
 Hymenoptera constitute 40 per cent, of the specimens, owing 
 chiefly to the predominance of ants ; Diptera follow with 30 
 per cent, and then Coleoptera with 13 per cent. Modern fam- 
 ilies are represented in great profusion. The material from 
 Florissant and neighboring localities includes a Lcpisina, fif- 
 teen species of Psocidae, over thirty species of x\phididae, and 
 over one hundred species of Elateridse, while the Rhynchoph- 
 ora number 193 species as against 150 species from the 
 
 Tertiary of Europe. Tipu- 
 lidas are abundant and ex- 
 cjuisitely preserved, while 
 Bibionidae, as compared with 
 their present numbers, are 
 surprisingly common. Nu- 
 merous masses of eggs oc- 
 cur, undoubtedly sialid and 
 closely like those of Cory- 
 dalis. Sialid characters, in- 
 deed, appear in the oldest 
 fossils known, and are 
 strongly manifest through- 
 out the fossil series, though among recent insects Sialidce oc- 
 cupy only a subordinate place. Strange to say, few' aquatic 
 insects have been found in this ancient lake basin. 
 
 Fossil butterflies are among the greatest rarities, only sev- 
 
 Proclyyas pcrscphonc, a fossil butterfly 
 from Colorado. Natural size. — • After 
 Scudder. 
 
DISTRIBUTION . 39I 
 
 enteen being known : yet Florissant has contributed eight of 
 these, a few of which are marvelOusly well preserved (Fig. 
 300), as appears from Scudder's figures. Two of the Floris- 
 sant specimens belong to Libytheinse, a group now scantily 
 represented, though widely distributed over the earth. The 
 group is structurally an archaic one. and its recent members 
 (forming only one eight-hundredth of the described species 
 of butterfiies) are doubtless relicts. 
 
 Taken as a whole, the insect facies of Tertiary times was 
 apparently much the same as at present. The Florissant fauna 
 and flora indicate, however, a former climate in Colorado as 
 warm as the present climate of Georgia. 
 
 Quaternary. — The interglacial clays of Toronto, Ontario, 
 have yielded fragments of the skeletons of beetles to the extent 
 of several hundred specimens, about one third of which 
 (chiefly eilytra) were sufiiciently complete or characteristic to 
 be identified by Dr. Scudder, who has found in all 76 species 
 of beetles, representing 8 families, chiefly Carabido; and 
 Staphylinidse. All these interglacial beetles are referable to 
 recent genera, but none of them to recent species, though the 
 differences between the interglacial species and their recent 
 allies are very slight. As a whole, these species " indicate 
 a climate closely resembling that of Ontario to-day, or perhaps 
 a slightly colder one. . . . One cannot fail, also, to notice that 
 a large number of the allies of the interglacial forms are re- 
 corded from the Pacific coast." (Scudder.) The writer, who 
 has studied these specimens, has been impressed most by their 
 likeness to modern species. It is indeed remarkable that so 
 little specific differentiation has occurred in these beetles since 
 the interglacial epoch — certainly ten thousand and possibly 
 two or three hundred thousand years ago. 
 
 General Conclusions. — Unfortunately, the earliest fossils 
 with which we are acquainted shed much less light upon the 
 subject of insect phylogeny than one might expect. The few 
 Devonian forms, though synthetic indeed as compared with 
 their modern allies, are at the same time highly organized, or 
 
392 ENTOMOLOGY 
 
 far from primitive, and their ancestors have been obhterated. 
 
 The general plan of wing- structure, as Scudder finds, has 
 remained unaltered from the earliest times, though the De- 
 vonian specimens exhibit many peculiarities of venation, in 
 which respect some of them are more specialized than their 
 nearest living allies, while none of them have much special 
 relation to Carboniferous forms. 
 
 Carboniferous insects are more nearly related to recent 
 forms than are the Devonian species, but present a number of 
 significant generalized features. Generally speaking, the tho- 
 racic segments were similar and unconsolidated, and the two 
 pairs of diaphanous wings were alike in every respect — in 
 groups that have since developed tegmina and dissimilar tho- 
 racic segments. The Carboniferous precursors of our cock- 
 roaches, phasmids and May flies have been mentioned. Palae- 
 ozoic insects are grouped by Scudder into a single order, 
 Palseodictyoptera, on account of their synthetic organization, 
 though other authors have tried to distribute them among the 
 modern orders. This disagreement will continue until, with 
 increasing knowledge, our classification becomes less arbitrary 
 and more natural. 
 
 Mesozoic insects are interesting chiefly as evolutionary links, 
 notably so in the case of cockroaches — the only insects whose 
 ancestry is continuously traceable. In this era the large fam- 
 ilies became differentiated out. 
 
 Most of the Tertiary species are referable to recent genera, 
 peculiar families being highly exceptional, while all the Quater- 
 nary species belong to recent genera. 
 
 Hemiptera appear in the Silurian; Neuroptera (in the old 
 sense) in the Devonian; Thysanura and Orthoptera, Carbonif- 
 erous ; Coleoptera and Hymenoptera, Triassic ; Diptera, Juras- 
 sic; and Lepidoptera not until the Tertiary. 
 
CHAPTER XITI 
 
 INSECTS IN RELATION TO MAN 
 
 A great many insects, eminently successful from their own 
 standpoint, so to speak, nevertheless interfere seriously with 
 the interests of man. On the other hand, many insects are 
 directly or indirectly so useful to man that their services form 
 no small compensation for the damage done hy other species. 
 
 Injurious Insects. — Insects destroy cultivated plants, infest 
 domestic animals, injure food, manufactured articles, etc., and 
 molest or harm man himself. 
 
 The cultivation of a plant in great quantity offers an un- 
 usual opportunity for the increase of its insect inhahitants. 
 The numher of species affecting- one kind of plant — to say 
 nothing of the number of individuals — is often great. Thus 
 about 200 species attack Indian corn, 50 of them doing notable 
 injury; 200 affect clover, directly or indirectly; and 400 the 
 apple ; while the oaks harbor probably i .000 species. 
 
 The average annual loss through the cotton worm, i860 to 
 1874. was $15,000,000. according to Packard; the loss from 
 the Rocky Mountain locust, in 1874, in Iowa, Missouri. Kan- 
 sas and Nebraska. $40,000,000 (Thomas) ; and the total loss 
 from this pest, 1874 to 1877, $200,000,000. The loss through 
 the chinch bug, in 1864, was $73,000,000 in Illinois alone, as 
 estimated by Riley. The ravages of the Hessian fly, fluted 
 scale, San Jose scale, gypsy moth and cotton boll weevil need 
 only be mentioned. 
 
 At times, an insect has been the source of a national calam- 
 ity, as was the case for forty years in France, when Phylloxera 
 threatened to exterminate the vine. In Africa the migratory 
 locust is an unmitigated evil. 
 
 Probably at least ten per cent, of every crop is lost through 
 the attacks of insects, though the loss is often so constant as 
 
 393 
 
394 ENTOMOLOGY 
 
 to escape observation. Regarded as a direct tax of ten cents 
 upon the dollar, however, this loss becomes impressive. Web- 
 ster says : " It costs the American farmer more to feed his 
 insect foes than it does to educate his children." The average 
 annual damage done by insects to crops in the United States 
 was conservatively estimated by Walsh and Riley to be $300,- 
 000,000 — or about $50 for each farm. " A recent estimate by 
 experts put the yearly loss from forest insect depredations at 
 not less than $100,000,000. The common schools of the coun- 
 try cost in 1902 the sum of $235,000,000, and all higher insti- 
 tutions of learning cost less than $50,000,000, making the total 
 cost of education in the United States considerably less than 
 the farmers lost from insect ravages. Thus it would be within 
 the statistical truth to make a still more startling statement 
 than Webster's, and say, that it costs American farmers more 
 to feed their insect foes than it does to maintain the whole 
 system of education for everybody's children. 
 
 " Furthermore, the yearly losses from insect ravages aggre- 
 gate nearly twace as much as it costs to maintain our army and 
 navy; more than twice the loss by fire; tw^ice the capital in- 
 vested in manufacturing agricultural implements ; and nearly 
 three times the estimated value of the products of all the fruit 
 orchards, vineyards, and small fruit farms in the country." 
 (Slingerland.) 
 
 Though most of the parasites of domestic animals are 
 merely annoyances, some inflict serious or even fatal injury, 
 as has been said. The gad flies persecute horses and cattle; 
 the maggots of a hot fly grow in the frontal sinuses of sheep, 
 causing vertigo and often death; another hot fly develops in 
 the stomach of the horse, enfeebling the animal. The worst 
 of the bot flies, however, is Hypoderma lineata, the ox-warble, 
 which not only impairs the beef but damages the hide by its 
 perforations ; the loss from this insect for one period of six 
 months (Chicago, 1889) was conservatively estimated as 
 $3,336,565, of which $667,513 represented the injury to hides. 
 
 All sorts of food stuffs are attacked by insects, particularly 
 
INSECTS IN RELATION TO MAN 395 
 
 cereals ; clothing-, especially of wool, fur or feathers ; also fur- 
 niture and hundreds of other useful articles. 
 
 As carriers of disease germs, insects are of ^•ital importance 
 to man, as we have shown. 
 
 Beneficial Insects. — The vast benefits derived from insects 
 are too often o\-erlooked, for the reason that they are often 
 so unobvious as compared with the injuries done by other spe- 
 cies. Insects are useful as checks upon noxious insects and 
 plants, as pollenizers of tiowers. as scavengers, as sources of 
 human clothing, food, etc., and as food for birds and fishes. 
 
 Almost every insect is subject to the attacks of other insects, 
 predaceous or parasitic — to say nothing of its many other 
 enemies — and but for this a single species of insect might soon 
 ox'errun the earth. There are only too many illustrations of 
 the tremendous spread of an insect in the absence of its accus- 
 tomed natural enemies. One of these examples is that of the 
 gypsy moth, artificially introduced into Massachusetts from 
 Europe ; another is the fluted scale, transported from Australia 
 to California. Some conception of the vast restrictin^g influ- 
 ence of one species upon another may be gained from the fact 
 that the fluted scale has practically been exterminated in Cali- 
 fornia as the result of the importation from Australia of one 
 of its natural enemies, a lady-bird beetle known as Ahn'iiis car- 
 dinalis. The plant lice, though of unparalleled fecundity, are 
 ordinarily held in check by a host of enemies, as w^as described. 
 
 An astonishingly large number of parasites may develop in 
 the body of a single individual ; thus over 3,000 specimens of 
 a hymenopterous parasite {Copidosoina truncatcUuin) were 
 reared by Giard from a single Pliisia caterpillar. 
 
 Parasites themselves are frequently parasitized, this phe- 
 nomenon of hyperparasitism being of considerable economic 
 importance. A beneficial primary parasite may be overpow- 
 ered by a secondary parasite, evidently to the indirect disad- 
 vantage of man, while the influence of a tertiary parasite would 
 be beneficial again. Xow parasites of the third order occur 
 and probably of the fourth order, as appears from Howard's 
 
39^ ENTOMOLOGY 
 
 studies, which we have already summarized. Moreover, para- 
 sites of ah degrees are attacked by predaceous insects, birds, 
 bacteria, fungi, etc. The control of one insect by another 
 becomes, then, a subject of extreme intricacy. 
 
 Insects render an important, though commonly unnoticed, 
 service to man in checking the growth of weeds. Indeed, in- 
 sects exercise a vast influence upon vegetation in general. A 
 conspicuous alteration in the vegetation has followed the inva- 
 sions of the Rocky IMountain locust, as Riley has said ; many 
 plants before unnoticed have grown in profusion and many 
 common kinds have attained an unusual luxuriance. 
 
 As agents in the cross pollination of flowers, insects are 
 eminently important. Darwin and his followers have proved 
 beyond question that as a rule cross pollination is indispensable 
 to the continued vitality of flowering plants ; that repeated 
 close pollination impairs their vigor to the point of extermina- 
 tion. Without the visits of bees and other insects our fruit 
 trees would yield little or nothing, and the fruit grower owes 
 these helpers a debt which is too often overlooked. 
 
 As scavengers, insects are of inestimable benefit, consuming 
 as they do in incalculable quantity all kinds of dead and decay- 
 ing" animal and vegetable matter. This function of insects is 
 most noticeable in the tropics, where the ants, in particular, 
 eradicate tons of decomposing matter that man lazily neglects. 
 
 The usefulness of the silkworms and the honey bee need 
 only be mentioned, and after these, the cochineal insect and the 
 lac insects. The " Spanish fly " — a meloid beetle — is still used 
 medicinally, and in China medicinal properties are ascribed 
 to many different insects. As human food, insects are of con- 
 siderable importance among semi-civilized races ; the migra- 
 tory locust is eaten in great quantities in Africa, and termites 
 in Africa and Australia, the latter insects being said to have 
 a delicious flavor; in ]\Iexico the egg's and adults of an aquatic 
 hemipteron. Corixa, are highly relished by the natives. As 
 food for fishes, g-ame birds, song- birds and poultry, insects are 
 of vast importance, it is needless to say. 
 
INSECTS IN RELATION TO MAN 397 
 
 Introduction and Spread of Injurious Insects. — Many of 
 (Uir worst insect pests were Ijrought accidentally from lun'ope. 
 notably the Hessian fly. wheat midg-e, codling- moth (prob- 
 ably), g'y])sy moth, cabbage bntterlly. cabbage aphis, clover 
 leaf beetle, cloxer root borer, asi)arag'ns beetle, imported cur- 
 rant worm and many cutworms; though few .American species 
 have obtained a foothold in Europe, one of the few being the 
 dreaded Phylloxera, which appeared in France in 1863. 
 
 The gypsy moth, liberated in Massachusetts in 1868, cost 
 the state over one million dollars in appropriations (1890- 
 1899) and is not yet under control. The San Jose scale, a 
 nati^■e of Xorth China according to ]\Iarlatt, was introduced 
 into the San Jose valley, California, about 1870, proljably upon 
 the flowering Chinese peach, became seriously destructive there 
 in 1873. "^'^'''-s carried across the continent to New Jersey in 
 1886 or 1887 on plum stock, and thence distributed directly to 
 several other states, upon nursery stock. At present the San 
 Jose scale is a permanent menace to horticulture throughout 
 the United States and is being checked or subdued only by the 
 vigorous and continuous work of official entomologists, acting 
 under special legislation. This pernicious insect occurs also 
 in Japan, Hawaii, Australia and Chile, in these places probably 
 as a recent introduction. 
 
 The Mexican cotton boll weevil (Aiitlioiioinus graiidis) 
 crossed the Rio Grande river and appeared in Brownsville, 
 Texas, about 1892, since when it has spread over eastern Texas 
 and even into western Louisiana. Advancing as it does at 
 the rate of fifty miles a year, the insect would require but fif- 
 teen or eighteen years to cover the entire cotton belt. The 
 beetle hibernates and lays its eg'gs in the cotton bolls ; these 
 are injured both by the larva feeding within and by the beetles, 
 whose feeding-punctures destroy the bolls and cause them to 
 drop. If unchecked, this pest would destroy fully one half the 
 cotton crop, entailing an annual loss of $250,000,000. As it 
 is, the universal adoption of the cultural methods recommended 
 by the Bureau of Entomology promises to reduce the damage 
 to a point at which cotton can still be grown at a fair profit. 
 
398 ENTOMOLOGY 
 
 An insect often passes readily from a wild plant to a nearly 
 related cultivated species. Thus the Colorado potato beetle 
 passed from the wild species Solaiiuni rostratuin to the intro- 
 duced species, Solannni tuhcrosnm, the potato. Many of our 
 fruit tree insects feed upon wild, as well as cultivated, species 
 of Rosace?e ; the peach borer, a native of this country, probably 
 fed orig-inally upon wild plum or wild cherry. Many of the 
 common scarab.neid larvae known as " white grubs " are native 
 to prairie sod, and attack the roots of various cultivated grasses, 
 including corn, and those of strawberry, potato and other 
 plants. The chinch bug fed originally upon native grasses, 
 but is ecjually at home on cultivated species, particularly millet, 
 Hungarian grass, rice, wheat, barley, rye and corn. In fact, 
 the worst corn insects, such as the chinch bug, wire w^orms. 
 white grubs and cutworms, are species derived from wild 
 grasses. 
 
 Even in the absence of cultivated plants their insect pests 
 continue to sustain themselves upon wild plants, as a rule ; the 
 larva of the codling moth is very common in wild apples and 
 wild haws. 
 
 The Economic Entomologist. — To mitigate the tremen- 
 dous damage done by insects, the individual cultivator is almost 
 helpless without expert advice, and the immense agricultural 
 interests of this country have necessitated the development of 
 the economic entomologist, the value of whose services is uni- 
 versally appreciated by the intelligent. 
 
 Nearly every State now has one or more economic entomolo- 
 gists, responsible to the State or else to a State Experiment 
 Station, while the general Government attends to general ento- 
 mological needs in the most comprehensive and thorough 
 manner. 
 
 " It is the special object of the economic entomologist," 
 says Dr. Forbes, " to investigate the conditions under which 
 these enormous losses of the food and labor of the country 
 occur, and to determine, first, whether any of them are in any 
 degree preventable; second, if so, how they are to be prevented 
 
INSECTS IN RELATION TO MAN 399 
 
 with the least possil)le cost of lalxM" and monev; and. tliird, to 
 estimate as exactly as possihle the expenses of such prevention, 
 or to furnish the data for such an estimate, in order that each 
 may determine for himself what is for his interest in every 
 case arising-. 
 
 " The suhject matter of this science is not insects alone, nor 
 plants alone, nor farmini^- alone. One may he a most excellent 
 entomologist or hotanist. or he may ha\c the whole theory and 
 practice of agriculture at his tongue's end, and at his fingers'' 
 ends as Avell, and yet he without knowdedge or resources when, 
 brought face to face with a new practical prol)lem in economic 
 entomology. The suhject is essentially that of the relations 
 of these things to each other ; of insect to plant and of plant 
 to insect, and of both these to the purposes and operations of 
 the farm, and it involves some knowdedge of all of them. 
 
 " As far as the entomological part of the subject is con- 
 cerned, the chief requisites are a familiar acquaintance with 
 the common injurious insects, and especially a thorough 
 knowledge of their life histories, together wdth a practical 
 familiarity with methods of entomological study and research. 
 The life histories of insects lie at the foundation of the whole 
 subject of economic entomology ; and constitute, in fact, the 
 principal part of the science; for until these are clearly and 
 completely made out for any given injurious species, we can- 
 not possibly tell when, where or how to strike it at its weakest 
 point. 
 
 " But besides this, we must also know the conditions favor- 
 able and unfavorable to it ; the enemies wdiich prey upon it, 
 whether bird or insect or plant parasite ; the diseases to which 
 it is subject, and the effects of the various changes of weather 
 and season. W^e should make, in fact, a thorough study of 
 it in relation to the whole system of things by wdiich it is 
 affected. Without this we shall often be exposed to needless 
 alarm and expense, perhaps, in fighting by artificial remedies, 
 an insect already in process of rapid extinction by natural 
 causes ; perhaps giving up in despair just at the time when the 
 
400 ENTOMOLOGY 
 
 natural checks upon its career are about to lend their powerful 
 aid to its suppression. We may even, for lack of this knowl- 
 edge, destroy our best friends under the supposition that they 
 are the authors of the mischief which they are really exerting 
 themselves to prevent. In addition to this knowledge of the 
 relations of our farm pests to what we may call the natural 
 conditions of their life, we must know how our own artificial 
 farming operations affect them, which of our methods of cul- 
 ture stimulate their increase, and which, if any, may help to 
 keep it down. And we must also learn where strictly artifi- 
 cial measures can be used to advantage to destroy them. 
 
 " For the life histories of insects, close, accurate and con- 
 tinuous observation is of course necessary ; and each species 
 studied must be followed not only through its periods of de- 
 structive abundance, w^hen it attracts general attention, but 
 through its times of scarcity as well, and season after season, 
 and year after year. 
 
 '' The observations thus made must of course be collected, 
 collated and most cautiously generalized, wdth constant refer- 
 ence to the conditions under which they were made. No part 
 of the work requires more care than this. 
 
 " This work becomes still more ditificult and intricate when 
 we pass from the simple life histories of insects to a study of 
 the natural checks upon their increase. Here hundreds and 
 even thousands of dissections of insectivorous birds and pre- 
 daceous insects are necessary, and a careful microscopic study 
 of their food, followed by summaries and tables of the prin- 
 cipal results, a tedious and laborious undertaking, a specialty 
 in itself, recjuiring its special methods and its special knowl- 
 edge of the structures of insects and plants, since these must 
 be recognized in fragments, while the ordinary student sees 
 them only entire. 
 
 " If we would understand the relations of season and 
 weather to the abundance of injurious insects, we are led up 
 to the science of meteorology; and if w^e undertake to master 
 the obscure subject of their diseases, especially those of epi- 
 
INSECTS IN RELATION TO MAN 4O I 
 
 demic or contag'ious character, we sliall find use for the highest 
 skill of the microscopist. and the best instruments of micro- 
 scopic research. 
 
 " All these investigations are preliminary to the practical 
 part of our subject. What shall the farmer do to protect his 
 crops? To answer this question, besides the studies just men- 
 tioned, much careful experiment is necessary. All practical 
 methods of fighting the injurious insects must be tried — first 
 on a small scale, and under conditions which the experimenter 
 can control completely, and then on the larger scale of actual 
 practice ; and these experiments must be repeated under vary- 
 ing circumstances, until we are sure that all chances of mistake 
 or of accidental coincidence are removed. The whole subject 
 of artificial remedies for insect depredations, whether topical 
 applications or special modes of culture, must be gone over 
 critically in this way. So many of the so-called experiments 
 upon which current statements relating to the value of reme- 
 dies and preventives are based, have been made by persons 
 unused to investigation, ignorant of the habits and the trans- 
 formations of the insects treated, without skill or training in 
 the estimation of evidence, and failing to understand the im- 
 portance of verification, that the whole subject is honeycombed 
 with blunders. Popular remedies for insect injuries have, in 
 fact, scarcely more value, as a rule, than popular remedies for 
 disease. 
 
 " Observation, record, generalization, experiment, verifica- 
 tion — these are the processes necessary for the mastery of this 
 subject, and they are the principal and ordinary processes of 
 all scientific research." 
 
 The official economic entomologist uses every means to 
 reach the public for whose benefit he works. Bulletins, circu- 
 lars and reports, embodying most serviceable information, are 
 distributed freely where they will do the most good, and timely 
 advice is disseminated through newspapers and agricultural 
 journals. An immense amount of correspondence is carried 
 on with individual seekers for help, and personal influence is 
 27 
 
402 ENTOMOLOGY 
 
 exerted in visits to infested localities and by addresses before 
 agricultural meetings. Special emergencies often tax every 
 resource of the official entomologist, especially if he is ham- 
 pered by inadequate legislative provision for his work. Too 
 often the public, disregarding the prophetic voice of the expert, 
 refuses to " close the door until the horse is stolen." 
 
 Aside from these emergencies, such as outbreaks of the 
 Rocky Mountain locust, chinch bug, Hessian fly, San Jose 
 scale and others, the State or Experiment Station entomologist 
 has his hands full in any State of agricultural importance ; in 
 fact, can scarcely discharge his duties properly without the aid 
 of a corps of competent assistants. 
 
 This chapter would be incomplete without some mention of 
 the progress of economic entomology in this country, especially 
 since America is pre-eminently the home of the science. The 
 history of the science is largely the history of the State and 
 Government entomologists, for the following account of whose 
 work we are indebted chiefly to the writings of Dr. Howard, 
 to which the reader is referred for additional details as well 
 as for a comprehensive review of the status of economic ento- 
 mology in foreig'n countries. 
 
 Massachusetts. — Dr. Thaddeus W. Harris, though preceded 
 as a writer upon economic entomology by William D. Peck, 
 was our pioneer official entomologist — official simply in the 
 sense that his classic volume was prepared and published at 
 the expense of the state of Massachusetts, first (1841) as a 
 " Report " and later as a " Treatise." The splendid Flint 
 edition (1862), entitled "A Treatise on Some of the Insects 
 Injurious to Vegetation," is still " the z'cuic mccum of the 
 working entomologist who resides in the northeastern section 
 of the country." 
 
 Dr. Alpheus S. Packard gave the state three short but use- 
 ful reports from 1871 to 1873. 
 
 As entomologist to the Hatch Experiment Station of the 
 Massachusetts Agricultural College, Prof. Charles H. Fernald 
 has issued important bulletins upon injurious insects, and has 
 
INSECTS IN RELATION TO MAN 4O3 
 
 publisliecl ill collalxn-atioii willi Edward II. Forbush a notable 
 volume upon the i;ypsy moth. For the suppression of this 
 pest, which threatened to exterminate ve.^-etation over one hun- 
 dred square miles, the state of Massachusetts made annual 
 appropriations amounting" in all to more than one million dol- 
 lars, and the operations, carried on by a committee of the State 
 Board of Agriculture, rank among the most extensive of their" 
 kind. 
 
 New York. — Dr. .\sa Fitch, appointed in 1854 by the New 
 York State Agricultural Society, under the authorization of 
 the legislature, was the first entomologist to be officially com- 
 missioned by any state. His fourteen repcjrts (1855 to 1872) 
 embody the results of a large amount of painstaking investi- 
 gation. 
 
 In 1881, Dr. James A. Lintner became state entomologist 
 of New York. Highly competent for his chosen work, Lint- 
 ner made every effort to further the cause of economic ento- 
 mology, and his thirteen reports, accurate, thorough and ex- 
 tremely serviceable, rank among the best. 
 
 Lintner has had a most able successor in Dr. E. P. Felt, who 
 is continuing the work with exceptional vigor and the most 
 careful regard for the entomological welfare of the state. 
 Felt has published at this writing eighteen bulletins (including 
 seven annual reports), besides important papers on forest and 
 shade tree insects, and has directed the preparation by Need- 
 ham and his associates of three notable volumes on aquatic 
 insects. 
 
 The Cornell Laiiversity Agricultural Experiment Station, 
 established in 1879, ^^^^ issued many valual)le publications 
 upon injurious insects, written by the master-hand of Pro- 
 fessor Comstock or else under his influence. The studies of 
 Comstock and Slingerland are always made in the most con- 
 scientious spirit and their bulletins — original, thorough and 
 practical — are models of what such works should be. 
 
 Illinois. — Mr. Benjamin D. Walsh, engaged in 1867 by the 
 Illinois State Horticultural Society, published in 1868, as act- 
 
404 ENTOMOLOGY 
 
 ing state entomologist, a report in the interests of horticulture 
 — an accurate, sagacious and altogether excellent piece of ori- 
 ginal work. Like many other economic entomologists he was 
 a prolific writer for the agricultural press and his contribu- 
 tions, numbering about four hundred, were in the highest 
 degree scientific and practical. 
 
 Walsh was succeeded by Dr. William LeBaron, who pub- 
 lished (1871 to 1874) four able reports of great practical 
 value. In the words of Dr. Howard, " He records in his first 
 report the first successful experiment in the transportation of 
 parasites of an injurious species from one locality to another, 
 and in his second report recommended the use of Paris green 
 against the canker worm on apple trees, the legitimate outcome 
 from which has been the extensive use of the same substance 
 against the codling moth, which may safely be called one of 
 the great discoveries in economic entomology of late years." 
 
 Following LeBaron as state entomologist, Rev. Cyrus 
 Thomas and his assistants, G. H. French and D. W. Coquillett, 
 produced a creditable series of six reports (1875 to 1880) as 
 part of a projected manual of the economic entomology of 
 Illinois. 
 
 Since 1882, Prof. Stephen A. Forbes has fulfilled the duties 
 of state entomologist in the most efficient manner. Thor- 
 oughly scientific, with a broad view and a clear insight into 
 the agricultural needs of the state, his authoritative and schol- 
 arly works upon economic entomology rank with those of the 
 highest value. Of the twelve reports issued thus far by Dr. 
 Forbes, those dealing with the chinch bug, San Jose scale, corn 
 insects and sugar beet insects are especially noteworthy. 
 
 Missouri. — Appointed in 1868, Prof. Charles V. Riley pub- 
 lished (1869 to 1877) nine reports as state entomologist. To 
 quote Dr. Howard, " They are monuments to the state of Mis- 
 souri, and more especially to the man who wrote them. They 
 are original, practical and scientific. . . . They may be said to 
 have formed the basis for the new economic entomology of 
 the world." Riley's subsequent work will presently be spoken 
 of. 
 
INSECTS IN RELATION TO MAN 4O5 
 
 State Experiment Stations. — The oro-anization of State 
 Agricultural Experiment Stations in 1888, under the Hatch 
 Act, gave economic entomology an additional impetus. At 
 present, all the states and territories, except Indian Territory, 
 have an experiment station, and in a few instances two or even 
 three; while there are stations in Alaska, Hawaii and Porto 
 Rico. These stations, often in connection with state agricul- 
 tural colleges, maintain altogether over forty men who con- 
 cern themselves more or less with entomology, and have issued 
 a great numher of bulletins upon injurious insects. These 
 publications are extremely valuable as a means of disseminat- 
 ing entomological information, and not a few of them are 
 based upon the investigations of their authors. Especially 
 noteworthy as regards originality, volume and general useful- 
 ness are the publications of Slingerland in New York. Smith 
 in New Jersey, Webster in Ohio (formerly), Hopkins in West 
 Virginia, Gillette and Osborn in Iowa and Gillette in Colorado. 
 The reports that Lugger issued in Minnesota, though compiled 
 for the most part, contain much serviceable information, pre- 
 sented in a popularly attractive manner. 
 
 While these workers have been conspicuously active in the 
 publication of their investigations, there are many other sta- 
 tion entomologists who devote themselves altogether to the 
 practical application of entomological knowledge, and whose 
 work in this respect is highly important, even though its influ- 
 ence does not extend beyond the limits of the state. 
 
 The U. S. Entomological Commission. — This commission 
 founded under a special Act of Congress in 1877 to investigate 
 the Rocky JNIountain locust, consisted of Dr. C. V. Riley, Dr. 
 A. S. Packard and Rev. Cyrus Thomas, remained in existence 
 until 1 88 1, and published five reports and seven bulletins, all 
 of lasting value. The first two reports form a most elaborate 
 monograph of the Rocky Mountain locust; the third report 
 includes important work upon the army worm and the canker 
 worm ; the fourth, written by Riley, is an admirable volume on 
 the cotton w^orm and boll worm ; and the fifth, by Packard, is 
 a useful treatise on forest and shade tree insects. 
 
406 ENTOMOLOGY 
 
 The U. S. Department of Agriculture. — The first ento- 
 mological expert appointed under the general government was 
 Townend Glover, in 1854. He issued a large number of 
 reports (1863-1877), which "are storehouses of interesting 
 and important facts which are too little used by the working 
 entomologists of to-day," as Howard says. Glover prepared, 
 moreo\'er, a most elaborate series of illustrations of North 
 American insects, at an enormous expense of labor, out of all 
 proportion, however, to the practical value of his undertaking. 
 
 Glover was succeeded in 1878 by Riley, whose achievements 
 have aroused international admiration. He resigned in a year, 
 after writing a report, and was succeeded by Prof. Comstock, 
 who held office for two years, during which he wrote two 
 important volumes (published respectively in 1880 and 1881) 
 dealing especially with cotton, orange and scale insects. His 
 work on scale insects laid the foundation for all our subsequent 
 investigation of the subject. 
 
 Riley, assuming the ofiice of government entomologist, pub- 
 lished up to 1894, "12 annual reports, 31 bulletins, 2 special 
 reports, 6 volumes of the periodical bulletin Insect Life, and 
 a large number of circulars of information." During his 
 vigorous and enterprising administration economic entomology 
 took an immense step in advance. The life histories of injuri- 
 ous insects were studied with extreme care and many valuable 
 improvements in insecticides and insecticide machinery were 
 made. One of the notable successes of Dr. Riley and his co- 
 workers, which has attracted an exceptional amount of public 
 attention, was the practical extermination of the fluted scale 
 (Iccrya piirchasi), which threatened to put an end to the cul- 
 tivation of citrus trees in California. This disaster was 
 averted by the importation from Australia, in 1888, of a native 
 enemy of the scale, namely, the lady-bird beetle Ahviits 
 (Fcdalia) cardiiialis, which, in less than eighteen months after 
 its introduction into California, subjugated the noxious scale 
 insect. The United States has since sent Noz'ius to South 
 Africa, Egypt and Portugal with similar beneficial results. 
 
INSECTS IN RELATION TO MAN AOJ 
 
 Based upon the foundation laid Ijy Riley, the work of the 
 Division (now the Bureau) of Entomology has steadily pro- 
 gressed, under the leadership of Dr. Leland O. Howard. With 
 a comprehensixe and linn grasp of his snhject, alert to discover 
 and develoj) new possibilities, energetic and resourceful in 
 management. Dr. Howard has brought the go\-ernment work 
 in applied entomology to its present position of commanding 
 importance. Admirably organized, the Bureau now maintains 
 a corps of about fifty experts, and the total output of the Divi- 
 sion and the Bureau now amounts to nearly one hundred bul- 
 letins and more than half as many circulars. 
 
 The Department of Agriculture has recently succeeded in 
 starting a new and important industry in California — the cul- 
 ture of the Smyrna fig. The superior flavor of this variety 
 is due to the presence of ripe seeds, or, in other words, to 
 fertilization, and for this it is necessary for pollen of the wdld 
 fig, ox " caprifig," to be transferred to the flowers of the 
 Smyrna fig. Normally this pollination, or " caprification," 
 is dependent upon the services of a minute chalcid, BlastopJi- 
 aga grossoniiit, which develops in the gall-like flow'ers of 
 the caprifig. The female insect, wdiich in this exceptional in- 
 stance is winged while the male is not, emerges from the gall 
 co\'ered with pollen, enters the young flowers of the Smyrna 
 fig to oviposit, and incidentally pollenizes them. 
 
 After many discouraging- attempts. Blastophaga, imported 
 from Algeria, has now been established in California, and the 
 new industry is developing rapidly. 
 
 Canada. — The development of economic entomology in 
 Canada has been due largely to the eft'orts of Dr. James 
 Fletcher, of the Dominion Experimental Earms, Ottawa, 
 whose annual reports and other writings indicate ability of an 
 exceptional order. His work has been furthered in every way 
 by the " eminent director of the experimental farms system. 
 Dr. William Saunders, himself a pioneer in economic ento- 
 mology in Canada and the author of one of the most valuable 
 treatises upon the subject that has ever been published in 
 America." 
 
408 ENTOMOLOGY 
 
 Outside of this, the work in Canada centers around the 
 Entomological Society of Ontario, whose excellent publica- 
 tions, sustained by the government, are of great scientific and 
 educational importance. In addition to its annual reports, this 
 society issues the Canadian Entomologist, one of the leading 
 serials of its kind, edited by its founder, the Rev. C. J. S. 
 Bethune, whose devoted services are appreciated by every 
 entomologist. 
 
 The Association of Official Economic Entomologists. — 
 Organized in 1889 by a few energetic workers, this association 
 has had a rapid and healthy growth and now numbers among 
 its members all the leading economic entomologists of America 
 and a large number of foreign workers. The annual meetings 
 of the association impart a vigorous stimulus to the individual 
 worker and tend to promote a well-balanced development of 
 the science of economic entomology. 
 
 Conclusion. — While working for the material welfare of 
 the agriculturist, the economic entomologist discovers phe- 
 nomena which are of the highest value to the purely scientific 
 mind. Indeed it is remarkable to notice the extent to which 
 the professedly practical entomologist is animated — not to say 
 dominated — by the same spirit which has led many of the most 
 profound thinkers that the world has ever produced to devote 
 their lives to the study of life itself. 
 
LITERATURE 
 
 The literature on entomological subjects now numbers scarcely less than 
 100.000 titles. The works listed below have been selected chiefly on 
 account of their general usefulness and accessibility. Works incidentally 
 containing important bibliographies of their special subjects are designated 
 each by an asterisk — *. 
 
 BIBLIOGRAPHICAL WORKS 
 
 Hagen, H. A. Bibliotheca Entomologica. 2 vols. Leipzig, 1862-1863. 
 
 Covers the entire literature of entomology up to 1862. 
 Engelmann, W. Bibliotheca Historico-Naturalis. i vol. Leipzig, 1846. 
 
 Literature, 1700-1846. 
 Carus, J. v., and Engelmann, W. Bibliotheca Zoologica. 2 vols. Leipzig, 
 
 1861. Literature, 1846-1860. 
 Taschenberg, 0. Bibliotheca Zoologica. 5 vols. Leipzig, 1887-1899. 
 
 Vols. 2 and 3, entomological literature, 1861-1880. 
 The Zoological Record. London. Annually since vol. for 1864. 
 Catalogue of Scientific Papers, Royal Society. London. Since 1868. 
 Zoologischer Anzeiger. Leipzig. Fortnightly since 1878. Bibliographica 
 
 Zoologica, annual volumes since 1896. 
 Concilium Bibliographicum. Zurich. Card catalogue of current zoological 
 
 literature since 1896. 
 Archiv fiir Naturgeschichte. Berlin. Annual summaries since 1835. 
 Journal of the Royal Microscopical Society. London. Summaries of the 
 
 most important works, beginning 1878. 
 Zoologischer Jahresbericht. Leipzig. Yearly summaries of literature 
 
 since 1879. 
 Zoologisches Centralblatt. Leipzig. Reviews of more important litera- 
 ture since 1895. 
 Psyche. Cambridge, Mass. Records of recent American literature. Also 
 
 earlier records, beginning 1874. 
 Entomological News. Philadelphia, 1890 to date. Records of current lit- 
 erature up to 1903. 
 Bibliography of the more important contributions to American Economic 
 
 Entomology. 8 parts. Pts. 1-5 by S. Henshaw ; pts. 6-S by N. 
 
 Banks. 1318 pp. Washington, 18S9-1905. 
 Catalogue of Scientific Serials, 1633-1876. S. H. Scudder. Cambridge, 
 
 Mass. Harvard University, 1879. 
 A Catalogue of Scientific and Technical Periodicals, 1665-1895. H. C. 
 
 Bolton. Washington, Smithsonian Institution, 1897. 
 
 409 
 
41 ENTOMOLOGY 
 
 A List of Works on North American Entomology. N. Banks. Bull. U. S. 
 Dept. Agric, Div. Ent., no. 24 (n. s.j, 95 pp. Washington, 1900. 
 
 GENERAL ENTOMOLOGY 
 
 Kirby, W., and Spence, W. 1822-26. An Introduction to Entomology. 
 
 4 vols. 36 + 2413 pp., 30 pis. London. 
 Burmeister, H. 1832-55. Handbuch der Entomologie. 2 vols. 28 -|- 1746 
 
 pp., 16 taf. Trans, of Band i : 1836. W. E- Shuckard. A Man- 
 ual of Entomology. 12 + 654 pp.. 32 pis. London. 
 Westwood, J. 0. 1839-40. An Introduction to the Modern Classification 
 
 of Insects. 2 vols. 23 + 620 pp., 133 figs. London. 
 Graber, V. 1877-79. Die Insekten. 2 vols. 8+1008 pp., 404 figs. 
 
 ]\Iimchen. 
 Miall, L. C, and Denny, A. 1886. The Structure and Life-History of the 
 
 Cockroach. 6 + 224 pp., 125 figs. London, Lovell Reeve & Co. ; 
 
 Leeds, R. Jackson. 
 Comstock, J. H. 1888. An Introduction to Entomology. 4 + 234 pp., 201 
 
 figs. Ithaca, N. Y. 
 Kolbe, H. J. 1889-93. Einfiihrung in die Kenntnis der Insekten. 12 + 
 
 709 pp., 324 figs. Berlin. F. Diimmler.* 
 Packard, A. S. 1889. Guide to the Study of Insects. Ed. 9, 12 + 715 
 
 pp., 668 figs., IS pis. New York. Henry Holt & Co. 
 Hyatt, A., and Arms, J. M. 1890. Insecta. 23 + 300 pp.. 13 pis., 223 figs. 
 
 Boston. D. C. Heath & Co.* 
 ICirby, W. F. 1892. Elementary Text-Book of Entomology. Ed. 2. 8 + 
 
 281 pp., 87 pis. London. Swan Sonnenschein & Co. 
 Comstock, J. H. and A. B. 1895. A Manual for the Study of Insects. 
 
 7 + 701 pp., 797 figs., 6 pis. Ithaca, N. Y. Comstock Pub. Co. 
 Sharp, D. 1895, 1901. Insects. Cambr. Nat. Hist., vols. 5, 6. 12+ 1 130 
 
 pp., 618 figs. London and New York. Macmillan & Co.* 
 Comstock, J. H. 1897, 1901. Insect Life. 6 + 349 PP-- 18 pis., 296 figs. 
 
 New York. D. Appleton & Co. 
 Packard, A. S. 1898. A Text-Book of Entomology. 17 + 729 pp., 654 
 
 figs. New York and London. The Macmillan Co.* 
 Carpenter, G. H. 1899. Insects; their Structure and Life. 11 + 404 pp., 
 
 184 figs. London. J. M. Dent & Co.* 
 Packard, A. S. 1899. Entomology for Beginners. Ed. 3. 16 + 367 pp., 
 
 273 figs. New York. Henry Holt & Co.* 
 Howard, L. 0. 1901. The Insect Book. 27 + 429 pp., 48 pis., 264 figs. 
 
 New York. Doubleday, Page & Co. 
 Hunter, S. J. 1902. Elementary Studies in Insect Life. 18 + 344 PP- 
 
 234 figs. Topeka. Crane & Co. 
 Henneguy, L. F. 1904. Les Insectes. INIorphologie, Reproduction, Em- 
 
 bryogenie. 18 + 804 pp., 622 figs., 4 pis. Paris. Masson et Cie.* 
 Kellogg V. L. 1905. American Insects. 7 + 674 pp., 13 pis., 812 figs. 
 
 New York. Henry Holt & Co. 
 
LITERATURE 4I I 
 
 PIIYLOGENY AND CLASSIFICATION 
 
 Kirby, W., and Spence, W. 1822-26. An Introduction to ICntomology. 
 
 4 vols. 36 4" -413 PP" 30 pis. London. 
 Burmeister, H. 1832. Handbuch der Entomologie. 2 vols. 284-1746 
 
 pp., 16 laf. Berlin. Translation of Band i : 1836. W. E. Shuck- 
 
 ard. A .Manual of Entomology. 12 + 654 PP-. 32 pis. London. 
 
 Contains useful synopses of the older systems of classification. 
 Westwood, J. 0. 1839-40. An Introduction to the Modern Classification 
 
 of Insects. 2 vols. 234-620 pp., 133 figs. London. 
 Miiller, F. 1864. Fiir Darwin. Leipzig. Trans. : 1869. W. S. Dallas. 
 
 l'"acts and Figures in aid of Darwin. London. 
 Brauer, F. 1869. Betrachtungen fiber die Verwandlung der Insekten im 
 
 Sinne der Descendenz-Theorie. Varh. zool.-bot. Gcsell. Wien, bd. 
 
 19. pp. 299-318; bd. 28 (1878), 1879, pp. 151-166. 
 Lubbock, J. 1873. On the Origin of Insects. Journ. Linn. Soc. Zool, 
 
 vol. II, pp. 422-425. 
 Packard, A. S. 1873. Our Common Insects. 225 pp., 268 figs. Boston. 
 
 Estes & Lauriat. 
 Lubbock, J. 1874. On the Origin and Metamorphoses of Insects. 164- 
 
 108 pp., 63 figs., 6 pis. London. Macmillan & Co.* 
 Mayer, P. 1876. Lfeber Ontogenie und Phylogenie der Insekten. Jenais. 
 
 Zeits. Naturw., bd. 10, pp. 125-221, taf. 6-6c. 
 Wood-Mason, J. 1879. Morphological Notes bearing on the Origin of 
 
 Insects. Trans. Ent. Soc. London, pp. 145-167, figs. 1-9. 
 Haase, E. 1881. Beitrag zur Phylogenie und Ontogenie der Chilopoden. 
 
 Zeits. Ent. Breslau, bd. 8, heft 2, pp. 93-115. 
 Lankester, E. R. 1881. Limulus an Arachnid. Quart. Journ. Micr. Sc, 
 
 vol. 21 (n. s.), pp. 504-548, 609-649, pis. 28. 29, figs. 1-20. 
 Packard, A. S. 1881. Scolopendrella and its Position in Nature. Amer. 
 
 Nat., vol. 15, pp. 698-704, fig. I. 
 Kingsley, J. S. 1883. Is the Group Arthropoda a valid one? Amer. 
 
 Xat., vol. 17, pp. 1034-1037. 
 Packard, A. S. 1883. The Systematic Position of the Orthoptera in rela- 
 tion to Other Orders of Insects. Third Rept. LI. S. Ent. Comm., 
 
 pp. 286-304. 
 Brauer, F. 1885. Systematisch-zoologische Studien. Sitzb. Akad. Wiss. 
 
 Wien, bd. 91, PP- 237-413.* 
 Grassi, B. 1885. I progenitori degli Insetti e dei Mi.riapodi. — Morfologia 
 
 delle Scolopendrelle. Atti. Accad. Torino, t. 21, pp. 48-50. 
 Haase, E. 1886. Die Vorfahren der Insecten. Sitzb. Abh. Isis Dresden, 
 
 pp. 85-91. 
 Claus, C. 1887. On the Relations of the Groups of Arthropoda. Ann. 
 
 'Slag. Nat. Hist., ser. 5, vol. 19, p. 396. 
 Kingsley, J. S. 1888. The Classification of the Myriapoda. Amer. Nat., 
 
 vol. 22, pp. 1118-1121. 
 
412 ENTOMOLOGY 
 
 Haase, E. 1889. Die Abdominalanhjinge der Insekten mit Beriicksichti- 
 
 gung der ]\Iyriopoden. Morpli. Jalirb., bd. 15, pp. 331-435, taf. 
 
 14, 15- 
 Fernald, H. T. 1890. The Relationships of Arthropods. Studies Biol. 
 
 Lab. Johns Hopk. Univ., vol. 4, pp. 431-513, pis. 48-50. 
 Hyatt, A., and Arms, J. M. 1890. Insecta. 23 -|- 300 pp., 13 pis., 223 
 
 figs. Boston. D. C. Heath & Co.* 
 Cholodkowsky, N. 1892. On the Morphology and Phylogeny of Insects. 
 
 Ann. Mag. Nat. Hist., ser. 6, vol. 10, pp. 429-451. 
 Grobben, C. 1893. A Contribution to the Knowledge of the Genealogy 
 
 and Classification of the Crustacea. Ann. Mag. Nat. Hist., ser. 
 
 6, vol. II, pp. 440-473. Trans, from Sitzb. Akad. Wiss. Wien, 
 
 math.-nat. CI., bd. loi, heft 2, pp. 237-274, taf. i. 
 Hansen, H. J. 1893. A Contribution to the Morphology of the Limbs 
 
 and Mouth-parts of Crustaceans and Insects. Ann. Mag. Nat. 
 
 Hist., ser. 6, vol. 12, pp. 417-434. Trans, from Zool. Anz., jhg. 
 
 16, pp. 193-198, 201-212. 
 Pocock, R. I. 1893. On some Points in the Morphology of the Arachnida 
 
 (s. s.) with Notes on the Classification of the Group. Ann. Mag. 
 
 Nat. Hist., ser. 6, vol. 11, pp. 1-19, pis. i, 2. 
 Pocock, R. I. 1893. On the Classification of the Tracheate Arthropoda. 
 
 Zool. Anz., jhg. 16, pp. 271-275. 
 Bernard, H. M. 1894. The Systematic Position of the Trilobites. Quart. 
 
 Journ. Geol. Soc. London, vol. 50, pp. 411-434, figs. 1-17. 
 Kingsley, J. S. 1894. The Classification of the Arthropoda. Amer. 
 
 Nat., vol. 28, pp. 118-135, 220-235.* 
 Kenyon, F. C. 1895. The Morphology and Classification of the Pauro- 
 
 poda, with Notes on the Morphology of the Diplopoda. Tufts 
 
 Coll. Studies, no. 4, pp. 77-146, pis. 1-3. 
 Schmidt, P. 1895. Beitrage zur Kenntnis der niederen Myriapoden. 
 
 Zeits. wiss. Zool., bd. 59, pp. 436-510, taf. 26, 27. 
 Wagner, J. 1895. Contributions to the Phylogeny of the Arachnida. 
 
 Ann. Mag. Nat. Hist., ser. 6, vol. 15, pp. 285-315. Trans, from 
 
 Jenais. Zeits. Naturw., bd. 29, pp. 123-156. 
 Miall, L. C. 1895. The Transformations of Insects. Nature, vol. 53, pp. 
 
 152-158. 
 Sedgwick, A. 1895. Peripatus. Camb. Nat. Hist., vol. 5, pp. 1-26, figs. 
 
 1-14. 
 Sinclair, F. G. 1895. Myriapoda. Camb. Nat. Hist., vol. 5, pp. 27-80, 
 
 figs. 15-46. 
 Sharp, D. 1895, 1901. Insects. Camb. Nat. Hist., vols. 5, 6. 12-1-1130 
 
 pp., 618 figs. London and New York. Macmillan & Co.* 
 Comstock, J. H. and A. B. 1895. A Manual for the Study of Insects. 
 
 7 -|- 701 pp., 797 figs., 6 pis. Ithaca, N. Y. Comstock Pub. Co. 
 Heymons, R. 1896. Zur Morphologic der Abdominalanhange bei den 
 
 Insecten. Morph. Jahrb., bd. 24, pp. 178-204, i taf. 
 
LITERATURE 4I3 
 
 Heymons, R. 1897. Mittheilungen ul)ei- die Segmentierung und den 
 
 Kr)rpcrbau der ]\Iyriopoden. Sitzb. Akad. Wiss., Berlin, bd. 40, 
 
 pp. 9i5-9-'3. 2 figs. 
 Hansen, H. J., and Sorensen, W. 1897. The Order Palpigradi Thor. and 
 
 its Relationship lo the Arachnida. Knt. Tidsk., arg. 18, pp. 223- 
 
 240, pi. 4. 
 Button, F. W., and others. 1897. Are the Arthropoda a Natnral Gronp? 
 
 Nat. Sc, \nl. 10, p\i. 97-1 1/- 
 Lankester, E. R. 1897. Are the Arthropoda a Natnral Gronp? Nat. 
 
 Sc, vol. ID, pp. 264-268. 
 Packard, A. S. 1898. A Text-Book of Entomology. 17 + 729 pp., 654 
 
 figs. New York and London. The IMacmillan Co.* 
 Packard, A. S. 1899. Entomology for Beginners. Ed. 3. 16 + 367 
 
 pp.. 273 figs. New York. Henry Holt & Co.* 
 Von Zittel, K. A. 1900, 1902. Text-Book of Palaeontology. 2 vols. 
 
 Trans. C. R. Eastman. London and New York. Macmillan 
 
 & Co.* 
 Folsom, J. W. 1900. The Development of the Month Parts of Anurida 
 
 maritima Gner. Bull. Alus. Comp. Zool., vol. 36, pp. 87-157, pis. 
 
 i-S.* 
 Hansen, H. J. 1902. On the Genera and Species of the Order Panropoda. 
 
 \"idensk. Mcdd. Natnrh. Foren. Kjobenhavn (1901), pp. 323-424, 
 
 pis. 1-6. 
 Carpenter, G. H. 1903. On the Relationships between the Classes of the 
 
 Arthropoda. Proc. R. Irish Acad., vol. 24, pp. 320-360, pi. 6* 
 Enderlein, G. 1903. Ueber die Morphologie, Gruppierung und systemat- 
 
 ische Stellung der Corrodentien. Zool. Anz., bd. 26, pp. 423- 
 
 437, 4 figs. 
 Hansen, H. J. 1903. The Genera and Species of the Order Symphyla. 
 
 Quart. Journ. INIicr. Sc, vol. 47, pp. i-ioi, pis. 1-7. 
 Packard, A. S. 1903. Hints on the Classification of the Arthropoda; the 
 
 Group, a Polyphyletic One. Proc. Amer. Phil. Soc, vol. 42, pp. 
 
 142-161. 
 Lankester, E. R. 1904. The Structure and Classification of the Arthro- 
 poda. Quart. Journ. Micr. Sc, vol. 47 (n. s.), pp. 523-582, pi. 
 
 42. (From Encyc. Britt., ed. 10.) 
 Carpenter, G. H. 1905. Notes on the Segmentation and Phylogeny of the 
 
 Arthropoda, with an Account of the Maxillse in Polyxenus lag- 
 
 urus. Quart. Journ. Micr. Sc, vol. 49, pt. 3, pp. 469-491, pi. 28.* 
 
 GENERAL ANATOMY 
 
 De Reaumur, R. A. F. 1734-42. Memoires pour servir a I'histoire des 
 
 insectes. 7 vols. Paris. 
 Lyonet, P. 1762. Traite anatomique de la Chenille, qui rouge le Bois 
 
 de Saule. Ed. 2. 22 -f 616 pp., x8 pis. La Haye. 
 Straus-Diirckheim, H. 1828. Considerations generates sur I'anatomie 
 
 comparee des aniniaux articules, etc. 19-1-434 PP- 10 pis. Paris. 
 
414 ENTOMOLOGY 
 
 Newport, G. 1839. Insecta. Todd's Cyclopaedia Anat. Phys., vol. 2, pp. 
 853-994, figs. 329-439- 
 
 Leydig, F. 1851. Anatomisches nnd Histologisches iiber die Larve von 
 • Corethra plumicornis. Zeits. wiss. Zool., bd. 3, pp. 435-451, taf. 
 16, iigs. 1-4. 
 
 Leydig, F. 1855. Zum feineren Ban der Arthropoden. Miiller's Archiv 
 Anat. Phys., pp. 376-480, taf. 3. 
 
 Leydig, F. 1857. Lehrbuch der Histologic des Menschen und der Thiere. 
 124-551 pp., figs. Frankfurt. 
 
 Leydig, F. 1859. Zur Anatomic der Insectcn. Miiller's Archiv Anat. 
 Phys., pp. 33-89, 149-183, taf. 3. 
 
 Leydig, F. 1864. Vom Ban des tierischen Korpers. Tiibingen. 
 
 Huxley, T. H. 1877. A Manual of the Anatomy of Invcrtebrated Ani- 
 mals. London. J. and A. Churchill. 1878. New York. D. 
 Appleton & Co. 
 
 Packard, A. S., and Minot, C. S. 1878. Anatomy and Embryology [of 
 the locust]. First Rept. U. S. Ent. Comm., pp. 257-279, figs. 
 12-18. Washington. 
 
 Lubbock, J. 1879. On the Anatomy of Ants. Trans. Linn. Soc. Zool., 
 sen 2, vol. 2, pp. 141-154, pis. 
 
 Riley, C. V., Packard, A. S., and Thomas C. 1880, 1883. Second and 
 Third Repts. U. S. Ent. Comm. Washington. 
 
 Minot, C. S. 1880. Histology of the Locust (Caloptenus) and the Cricket 
 (Anabrus). Second Rept. V. S. Ent. Comm., pp. 183-222, pis. 
 2-8. Washington. 
 
 Brooks, W. K. 1882. Handbook of Invertebrate Zoology, pp. 237-269, 
 figs. 129-141. Boston. S. E. Cassino. 
 
 Viallanes, H. 1882. Rechcrches sur I'histologic des insectes. Ann. Sc. 
 nat. Zool., ser. 6, t. 14, pp. 1-348, pis. 1-18. 
 
 Leydig, F. 1883. Untersuchungen zur Anatomic und Histologic der 
 Thiere. 174 pp., 8 taf. Bonn. 
 
 Miall, L. C, and Denny, A. 1886. The Structure and Life-history of the 
 Cockroach. 6 -(- 224 pp., 125 figs. London, Lovell Reeve & 
 Co. ; Leeds, R. Jackson. 
 
 Schaeffer, C. 1889. Beitrage zur Histologic der Lisektcn. Zool. Jahrb., 
 ]\Iorph. Abth.. bd. 3, pp. 611-652, taf. 29, 30. 
 
 Lowne, B. T. 1890-92. The Anatomy, Physiology, Morphology and De- 
 velopment of the Blow-fly (Calliphora crythroccphala). A Study 
 in the Comparative Anatomy and Morphology of Insects. 8 4- 
 778 pp., 108 figs., 21 pis. London.* 
 
 Lang, A. 1891. Text-Book of Comparative .\natomy. Trans, by H. M. 
 and M. Bernard. Pt. i, pp. 43S-508, figs. 301-356. London and 
 New York. Macmillan & Co.* 
 
 Comstock, J, H., and Kellogg, V. L. 1899. The Elements of Insect Anat- 
 omy. Rev. ed. 134 pp., 11 figs. Ithaca, N. Y. Comstock Pub- 
 lishing Co. 
 
LITERATURE 4^5 
 
 HEAD AND APPENDAGES 
 
 Schaum, H. 1863. Uber die Ziisammensetzung des Kopfes und die Zahl 
 
 del- Alxloniinalsegmente bci den Insekten. Archiv Naturg., jhg. 
 
 29, 1)(I. I. pp. 247-260. 
 Basch, S. 1865. Skclctt und iNInskcln des Kopfes von Termes. Zeits. 
 
 wiss. Zool., b(l 15, pp. 55-/5, i t^f- 
 Breitenbach, W. 1877. Vorlaiifige Mitteilung uber einige ncuc Unter- 
 
 suchungen an Schmetterlingsriisseln. Arcbiv mikr. Anat., bd. 14, 
 
 pp. 308-317. I taf. 
 Breitenbach, W. 1878. Unter.sucbungen an Scbmetterlingsriisseln. Ar- 
 
 cliiv mikr. Anat., bd. 15, pp. 8-29, i taf. 
 Breitenbach, W. 1879. Ueber Schmetterlingsriissel. Ent. Nachr., jbg. 5, 
 
 pp. 237-243. 
 Burgess, E. 1880. Contributions to tbe Anatomy of tbc Milk-weed But- 
 
 terBy (Danais arcbippus Fabr.). Anniv. Mem. Bost. Soc. Nat. 
 
 Hist., 16 pp., 2 pis. 
 Meinert, F. 1880. Sur la conformation de la tete et sur I'interpretation 
 
 des organes buccaux cbez les Insectes, ainsi que sur la systema- 
 
 tique de cet ordre. Ent. Tidsk., arg. i, pp. 147-150. 
 Dimmock, G. 1881. The Anatomy of the jNIouth Parts and of the Suck- 
 ing Apparatus of some Diptera. 50 pp., 4 pis. Boston. A. 
 
 Williams & Co.* 
 Geise, 0. 1883. Die Mundtheile der Rbynchoten. Archiv Naturg., jbg. 
 
 49, bd. I, pp. 315-373. taf. 10. 
 Kraepelin, K. 1S83. Zur Anatomic und Physiologic des Riissels von 
 
 jMusca. Zeits. wiss. Zool, bd. 39, pp. 683-719, taf. 40, 41. 
 Briant, T. J. 1884. On the Anatomy and Functions of the Tongue of the 
 
 Honey Bee (worker). Journ. Linn. Soc. Zool., vol. 17, pp. 408- 
 
 417, pis. 18, 19. 
 Wedde, H. 1885. BeitrJige zur Kenntniss des Rhynchotenriissels. Ar- 
 chiv Naturg., jhg. 51, bd. i, pp. 1 13-143, taf. 6, 7. 
 Walter, A. 1885. Beitrage zur Morphologic der Schmetterlinge. Jenais. 
 
 Zeits. Naturw., bd. 18, pp. 751-807, taf. 23, 24. 
 Walter, A. 1885. Zur Morphologic der Schmetteflingsmundtheile. 
 
 Jenais. Zeits. Naturw., bd. 19, pp. 19-27. 
 Breithaupt, P. F. 1886. Ueber die Anatomic und die Functionen der 
 
 Bienenzunge. Archiv Naturg., jhg. 52, bd. i, pp. 47-112, taf. 4, 5.* 
 Blanc, L. 1891. La tete du Bombyx mori a I'etat larvaire, anatomic et 
 
 physiologic. Trav. Lab. fitud. Soie, 1889-1890, 180 pp., 95 figs. 
 
 Lyon. 
 Smith, J. B. 1892. The Mouth Parts of Copris Carolina; with Notes on 
 
 the Homologies of the Mandibles. Trans. Amer. Ent. Soc, vol. 
 
 19, pp. 83-87, pis. 2, 3. 
 Hansen, H. J. 1893. A Contribution to the Morphology of the Limbs 
 
 and Mouth Parts of Crustaceans and Insects. Ann. Mag. Nat. 
 
 Hist., ser. 6, vol. 12, pp. 417-434. Trans, from Zool. Anz., jhg. 
 
 16, pp. 193-198, 201-212. 
 
41 6 ENTOMOLOGY 
 
 Kellogg, V. L. 1895. Tlie ]\Iouth Parts of the Lepidoptera. Amer. Nat.. 
 
 vol. 29, pp. 546-556, pi. 25, figs. I, 2. 
 
 Smith, J. B. 1896. An Essay on the Development of the Mouth Parts 
 
 of certain Insects. Trans. Amer. Phil. Soc, vol. 19 (n. s.), pp. 
 
 175-198, pis. 1-3. 
 Folsom, J. W. 1899. The Anatomy and Physiology of the Mouth Parts 
 
 of the Collembolan, Orchesella cincta L. Bull. Mus. Comp. Zool., 
 
 vol. 35, pp. 7-39, pis. 1-4.* 
 Janet, C. 1899. Essai sur la constitution morphologique de la tete de 
 
 I'insecte. 74 pp., 7 pis. Paris. G. Carre et C. Naud. 
 Kellogg, V. L. 1899. The Mouth Parts of the Nematocerous Diptera. 
 
 Psyche, vol. 8, pp. 303-306, 327-220, 346-348, 355-359, 363-365, 
 
 figs. I-II. 
 Folsom, J. W. 1900. The Development of the Mouth Parts of Anurida 
 
 maritima Guer. Bull. Mus. Comp. Zool., vol. 2i^, pp. 87-157, pis. 
 
 1-8.* 
 Comstock, J. H., and Kochi, C. 1902. The Skeleton of the Head of In- 
 sects. Amer. Nat., vol. 36, pp. 13-45, figs. 1-29.* 
 Kellogg, V. L. 1902. The Development and Homologies of the Mouth 
 
 Parts of Insects. Amer. Nat., vol. 36, pp. 683-706, figs. 1-26. 
 Meek, W. J. 1903. On the Mouth Parts of the Hemiptera. Kansas 
 
 Univ. Sc. Bull, vol. 2 (12), pp. 257-277, pis. 7-1 1.* 
 Holmgren, N. 1904. Zur Morphologic des Insektenkopfes. Zeits. wiss. 
 
 Zool., bd. 76, pp. 439-477, taf. 27, 28.* 
 Kulagin, N. 1905. Der Kopfbau bei Culex und Anopl^eles. Zeits. wiss. 
 
 Zool., bd. 83, pp. 285-335, taf. 12-14.* 
 
 THORAX AND APPENDAGES; LOCOMOTION 
 
 Audouin, J. V. 1824. Recherches anatomiques sur le thorax des animaux 
 articules ct celui des insectes hexapodes en particulier. Ann. Sc. 
 nat. Zool, t. I. pp. 97-135, 416-432, figs. 
 
 MacLeay, W. S. 1830. Explanation of the comparative anatomy of the 
 thorax in winged insects, with a review of the present state of 
 the nomenclature of its parts. Zool. Journ., vol. 5, pp. 145-179, 
 2 pis. 
 
 Langer, K. i860. Ueber den Gelenkbau bei den Arthrozoen. Vierter 
 Beitrag zur vergleichenden Anatomic und Mechanik der Gelenke. 
 Denks. Akad. Wiss. Wien.,'Phys. CL, bd. 18, pp. 99-140, 3 taf. 
 
 "West, T. 1861. The Foot of the Fly; its Structure and Action; eluci- 
 dated by comparison with the feet of other Insects, etc. Trans. 
 Linn. Soc. Zool, vol. 23, pp. 393-421, pis. 41-43. 
 
 Plateau, F. 1871. Qu'est-ce que I'aile d"un Insecte? Stett. ent. Zeit., 
 jhg. 32, pp. 33-42, pi. I. 
 
 Plateau, F. 1872. Recherches experimentales sur la position du centre 
 de gravite chez les insectes. Archiv. Sc. phys. nat. Geneve, nouv. 
 per., t. 43, pp. 5-37. 
 
LITERATURE 417 
 
 Pettigrew, J. B. 1874. Animal Locomotion. 13 + 264 pp., 130 figs. New 
 
 York. D. Appleton & Co. 
 Marey, E. J. 1874, 1879. Animal Mechanism. 16 + 283 pp., 117 figs. 
 
 New York. D. Appleton & Co. 
 Hammond, A. 1881. On the Thorax of the Blow-fly (Musca vomitoria). 
 
 Journ. T,inn. Soc. Zool., vol. 15, pp. 9-31, pls. i, 2. 
 Von Lendenfeld, R. 1881. Der Plug der Libellen. Kin Beitrag zur Anat- 
 omic und Physiologic der Plugorgane der Insecten. Sitzb. Akad. 
 
 Wiss. Wien., bd. 83, pp. 289-376, taf. 1-7. 
 Brauer, F. 1882. Ueber das Segment mediaire Latrcillc's. Sitzb. Akad. 
 
 \\'iss. Wien, bd. 85, pp. 218-244, taf. 1-3. 
 Dahl, F. 1884. Beitriige zur Kenntnis des Baues vmd der Fiinktionen der 
 
 Insektenbeine. Archiv Naturg., jhg. 50, bd. i, pp. 146-193. taf. 
 
 II-I3- 
 Dewitz, H. 1884. Ueber die Portbewegung der Thiere an senkrechten 
 
 glattcn I'liichen vermittelst eines Sekretes. Pflitger's Archiv ges. 
 
 Phys., bd. 33, pp. 440-481, taf. 7-9. 
 Graber, V. 1884. Ueber die Mechanik des Insektenkorpers. L Mechanik 
 
 der Peine. Biol. Centralbl., bd. 4, pp. 560-570. 
 Amans, P. 1885. Comparaisons des organes du vol dans la serie animale. 
 
 Ann. Sc. nat. Zool., sen 6, t. 19, pp. 1-222, pis. 1-8. 
 Redtenbacher, J. 1886. Vergleichende Studien iiber das Pliigelgeader der 
 
 Insecten. Ann. naturh. Hofm. Wien, bd. i. pp. 153-232, taf. 
 
 9-20. 
 Amans, P. C. 1888. Comparaisons des organes de la locomotion aqua- 
 
 tique. Ann. Sc. nat. Zool., ser. 7, t. 6, pp. 1-164, pis. 1-6. 
 Carlet, G. 1888. Sur le mode de locomotion des chenilles. Compt. rend. 
 
 Acad. Sc, t. 107, pp. 131-134- 
 Ockler, A. 1890. Das Krallenglied am Insektenfuss. Archiv Naturg., 
 
 jhg. 56, bd. I, pp. 221-262, taf. 12, 13. 
 Demoor, J. 1891. Recherches sur la marche des Insectes et des Arach- 
 
 nides. Archiv. Biol., t. 10, pp. 567-608, pis. 18-20. 
 Hoffbauer, C. 1892. Beitrage zur Kenntnis der Insektenfliigel. Zeits. 
 
 wiss. Zool;. bd. 54, pp. 579-630, taf. 26, 27, 3 figs.* 
 Spuler, A. 1892. Zur Phylogenie und Ontogenie des Pliigelgeader der 
 
 Schmetterlinge. Zeits. wiss. Zool., bd. 53, pp. 597-646, taf. 25, 26. 
 Comstock, J. H. 1893. Evolution and Taxonomy. Wilder Quarter- 
 
 Centurj' Book, pp. 37-114, pls. i-3- Ithaca, N. Y. 
 Kellogg, V. L. 1895. The Affinities of the Lepidopterous Wing. Amer. 
 
 Nat., vol. 29, pp. 709-717, figs. i-io. 
 Marey, E. J. 1895. Movement. 15 + 3^3 PP-, 204 figs. New York. D. 
 
 Appleton & Co. 
 Comstock, J, H., and Needham, J. G. 1898-99. The Wings of Insects. 
 
 Amer. Nat., vols. 32, 33, pp. 43-48, 81-89, 231-257, 335-340, 413- 
 
 424, 561-565, 769-777, 903-911, 117-126, 573-582, 845-860, figs. 1-90. 
 
 Reprint, Ithaca, N. Y. Comstock Pub. Co. 
 Walton, L. B. 1900. The Basal Segments of the Hexapod Leg. Amer. 
 
 Nat., vol. 34, pp. 267-274, figs. 1-6. 
 
41 « ENTOMOLOGY 
 
 Verhoeff, K. W. 1902. Beitrage zur vergleichenden Morphologic des 
 Thorax der Insekten mit Beriicksichtigung der Chilopoden. Nova 
 Acta Leop. -Carol. Akad. Naturf., bd. 81, pp. 63-110, taf. 7-13. 
 
 Voss, F. 1904-05. Uber den Thorax von Gryllus domesticus. Zcits. 
 wiss. Zool., bd. 78, pp. 268-521, taf. 15, 16, 25 figs. 
 
 ABDOMEN AND APPENDAGES 
 
 Lacaze-Duthiers, H. 1849-53. Rechcrches sur Tarmure genitalc femelle 
 
 des insectes. Ann. Sc. nat Zool., ser. 3, t. 12-19, pls. Several 
 
 papers. 
 Fenger, W. H. 1863. Anatomic nnd Physiologic des Giftapparates bei 
 
 den Hymenopteren. Archiv Naturg., jhg. 29, bd. i, pp. 139-178, 
 
 I taf. 
 Schaum, H. 1863. Ueber die Zusammensetziing des Kopfes und die Zahl 
 
 der Abdominalsegmente bei den Insekten. Archiv Naturg., jhg. 
 
 29, bd. I, pp. 247-260. 
 Sollmann, A. 1863. Der Bienenstachel. Zeits. wiss. Zool., bd. 13, pp. 
 
 528-540, I taf. 
 Packard, A. S. 1866. Observations on the Development and Position of 
 
 the Hymenoptera, with Notes on the Morphology of Insects. 
 
 Proc. Bost. Soc. Nat. Hist., vol. 10, pp. 279-295, figs. 1-4. 
 Goossens, T. 1868. Notes sur les pattes membraneuses des Chenilles. 
 
 Ann. Soc. ent. France, ser. 4, t. 8, pp. 745-748. 
 Packard, A. S. 1868. On the Structure of the Ovipositor and Homol- 
 ogous Parts in the Male Insect. Proc. Bost. Soc. Nat. Hist., vol. 
 
 II, pp. 393-399, figs. i-ii. 
 Graber, V. 1870. Die Aehnlichkeit im Baue der ausseren weiblichen 
 
 Geschlechtsorgane bei den Locustiden und Akridiern dargestellt 
 
 auf Grund ihrer Entwicklungsgeschichte. Sitzb. Akad. Wiss. 
 
 Wien, math.-naturw. CL, bd. 61, pp. 597-616, taf. 
 Scudder, S. H., and Burgess, E. 1870. On Asymmetry in the Appendages 
 
 of Hexapod Insects, especially as illustrated in the Lepidopterous 
 
 Genus Nisoniades. Proc. Bost. Soc. Nat. Hist., vol. 13, pp. 282- 
 
 306, I pi. 
 Krapelin, C. 1873. Untersuchungen iiber den Bau, Mechanismus und die 
 
 Entwicklungsgeschichte des Stachels der bienenartigen Thiere. 
 
 Zeits. wiss. Zool, bd. 23, pp. 289-330, taf. 15, 16. 
 Dewitz, H. 1875. Ueber Bau und Entwickelung des Stachels und der 
 
 Legescheide einiger Hymenopteren und der grihien Heuschrecke. 
 
 Zeits. wiss. Zool., bd. 25, pp. 174-200, taf. 12, 13. 
 White, F. B. 1876. On the Male Genital Armature in the Rhopalocera. 
 
 Trans. Linn. Soc. Zool., ser. i, vol. i, pp. 357-369, 3 pis. 
 Adler, H. 1877. Lege-Apparat und Eierlegen der Gallwespen. Deuts. 
 
 ent. Zeits., jhg. 21, pp. 305-332, taf. 2. 
 Dewitz, H. 1877. Ueber Bau und Entwickelung des Stachels der Amei- 
 
 sen. Zeits. wiss. Zool., bd. 28, pp. 527-556, taf. 26. 
 
LITERATURE 419 
 
 Davis, H. 1879. Notes on the Pygidia and Ccrci of Insects. Jonrn. R. 
 
 INIicr. Soc, vol. 2, pp. 252-255. 
 Kraatz, G. 1881. Ueber die Wichtigkeit der Untcrsuclunig des miinn- 
 
 lichen Begattungsgliedes der Krifer fur die Systcmatik und Artun- 
 
 terscheidung. Dents, ent. Zeits., jhg. 25, pp. 113-126. 
 Dewitz, H. 1882. Ueber die Fiihrung an den Korperhiingen der Insecten. 
 
 P.crlin ent. Zeits., bd. 26, pp. 51-68, fig. 
 Gosse, P. H. 1882. On the Clasping Organs ancillary to Generation in 
 
 certain Groups of the Lepidoptera. Trans. Linn. Soc. Zool, ser. 
 
 2, vol. 2, pp. 265-345, 8 pis. 
 Von Hagens, D. 1882. Ueber die mannlichen Genitalien der Bienen-Gat- 
 
 tung Sphecodes. Dents, ent. Zeits., jhg. 26, pp. 209-228, taf. 6, 7. 
 Radoszkowski, 0. 1884. Revision des armures copulatrices des males du 
 
 genre Bombus. Bull. Soc. Nat. Moscou, t. 49, pp. 51-92, 4 pls. 
 Saunders, E. 1884. Further notes on the terminal segments of Aculeate 
 
 Hynienoptera. Trans. Ent. Soc. London, pp. 251-267. 
 Haase, E. 1885. Ueber sexnelle Charactere bei Schmetterlingen. Zeits. 
 
 Ent. Breslau, n. f, bd. 9. PP- 15-19; bd. 10, pp. 36-44- 
 Radoszkowski, 0. 1885. Revision des armures copulatrices des males de 
 
 la famille des Mutillidje. Horse Soc. Ent. Ross., t. 19, pp. 3-49. 
 
 9 pis. 
 Von Ihering, H. 1886. Der Stachel der Meliponen. Ent. Nachr., jhg. 12, 
 
 pp. 177-188, taf. 8. 
 Goossens, T. 1887. Les pattes des Chenilles. Ann. Soc. ent. France, ser. 
 
 6, t. 7. pp. 385-404. pl- 7- 
 Graber, V. 1888. Ueber die Polypodie bei Insekten-Embryonen. Morph. 
 
 Jahrb., bd. 13, pp. 586-615, taf. 25, 26. 
 Haase, E. 1889. Ueber Abdominalanhange bei Hexapoden. Sitzb. Gesell. 
 
 naturf. Freunde, pp. 19-29. 
 Haase, E. 1889. Die Abdominalanhange der Insekten mit Beriicksichti- 
 
 gung der Myriopoden. Morph. Jahrb., bd. 15, pp. 331-435. taf. 
 
 14, 15. 
 Radoszkowski, 0. 1889. Revision des armures copulatrices des males de 
 
 la tribu des Chrysides. Horse Soc. Ent. Ross., t. 23, pp. 3-40, pis. 
 
 1-6. 
 Beyer, 0. W. 1890. Der Giftapparat von Formica rufa, ein reduziertes 
 
 Organ. Jenais. Zeits. Naturw., bd. 25, pp. 26-112, taf. 3, 4. 
 Carlet, G. 1890. Memoire sur le venin et I'aiguillon de I'abeille. Ann. 
 
 Sc. nat. Zool., ser. 7, t. 9, pp. 1-17, pi. i. 
 Packard, A. S. 1890. Notes on some points in the external structure 
 
 and phylogeny of Lepidopterous larvse. Proc. Bost. Soc. Nat. 
 
 Hist., vol. 25, pp. S2-114, pis. I, 2. 
 Sharp, D. 1890. On the structure of the terminal segment in some male 
 
 Hemiptera. Trans. Ent. Soc. London, pp. 399-427, pis. 12-14. 
 Wheeler, W. M. 1890. On the Appendages of the first abdominal Seg- 
 ment of embryo Lisects. Trans. Wis. Acad. Sc, vol. 8, pp. 87- 
 
 140, pis. 1-3.* 
 
420 ENTOMOLOGY 
 
 Escherich, K. 1892. Die biologische Bedeutung der Genitalanhange der 
 
 Insektcn. Verb, zool.-bot. Ges. Wien, bd. 42, pp. 225-240, taf. 4. 
 Graber, V. 1892. Ueber die morphologische Bedeutung der Abdominalan- 
 
 bange der Insekten-Embrvonen. Alorpb. Jabrb., bd. 17, pp. 467- 
 
 482. 
 Escherich, K. 1894. Anatomiscbe Studien iiber das mannUcbe Genital- 
 system der Coleopteren. Zeits. wiss. Zool., bd. 57, pp. 620-641, 
 
 taf. 26, 3 figs. 
 Janet, C. 1894. Sur la Morphologie du squelette des segments post- 
 
 thoraciques chez les Myrmicides. Note 5. Mem. Soc. acad. Oise, 
 
 t. 15, pp. 591-61 1, figs. 1-5. 
 Perez, J. 1894. De I'organe copulateur male des Hymenopteres et de sa 
 
 valeur taxonomique. Ann. Soc. ent. France, t. 63, pp. 74-81, figs. 
 
 1-8. 
 Verhoeff, C. 1894. Vergleicbende Untersucbungen iiber die Abdominal- 
 
 segmente der weiblichen Hemiptera-Heteroptera und Homoptera. 
 
 Verb. nat. Ver. Bonn, jhg. 50, pp. 307-374. 
 Heymons, R. 1895. Die Segmentirung des Insectenkorpers. Anb. Abb. 
 
 Preuss. Akad. Wiss. Berlin, 39 pp., i taf. 
 Heymons, R. 1895. Die Embryonalentwickelung von Dermapteren und 
 
 Ortbopteren unter besonderer Beriicksicbtigung der Keimblatter- 
 
 bildung. 136 pp., 12 taf., 33 figs. Jena. 
 Peytoureau, S. A. 1895. Contribution a I'etude de la morpbologie de 
 
 I'armure genitale des Insectes. 248 pp., 22 pis., 43 figs. Paris. 
 Verhoeff, S. 1895. Beitrage zur vergleicbenden Morpbologie des Abdo- 
 mens der Coccinelliden, etc. Arcbiv Naturg., jbg. 61, bd. i, pp. 
 
 1-80, taf. 1-6. 
 Verhoeff, C. 1895. Vergleicbend-morpbologiscbe Untersucbungen iiber 
 
 das Abdomen der Endomychiden, Erotyliden und Languriiden 
 
 (im alten Sinne) und iiber die Muskulatur des Copulationsap- 
 
 parates von Triplex. Arcbiv Naturg., jbg. 61, bd. i, pp. 213-287, 
 
 taf. 12, 13. 
 Verhoeff, C. 1895. Cerci und Styli der Tracbeaten. Ent. Nacbr., jhg. 
 
 21. pp. 166-168. 
 Heymons, R. 1896. Grundziige der Entwickelung und des Korperbaues 
 
 von Odonaten und Ephemeriden. Anb, Abb. Akad. Wiss. Berlin, 
 
 66 pp., 2 taf. 
 Heymons, R. 1896. Zur Morphologie des Abdominalanhange bei den 
 
 Insekten. Morpb. Jabrb., bd. 24, pp. 178-204, taf. i. 
 Verhoeff, C. 1896. Zur Morphologie der Segmentanbange bei Insecten 
 
 und Myriopoden. Zool. Anz., bd. 19, pp. 378-383, 385-388. 
 Goddard, M. F. 1897, On the Second Abdominal Segment in a few Libel- 
 
 lulidse. Proc. Amer. Phil. Soc, vol. 35, pp. 205-212, 2 pis. 
 Janet, C. 1897. Limites morphologiques des anlieaux post-cephaliques et 
 
 Musculature des anneaux post-thoraciques chez la Myrmica rubra. 
 
 Note 16. 35 pp., 10 figs. Lille. 
 Verhoeff, C. 1897. Bemerkungen iiber abdominale Korperanhange bei 
 
 Insecten und Myriopoden. Zool. Anz., bd. 20, pp. 293-300. 
 
LITERATURE 42 1 
 
 Janet, C. 1898. Aignillon de la ]\Iyrmica rubra. Appareil dc fcrmeture 
 de la glande a venin. Note 18, 27 pp., 3 pis. Paris. 
 
 Zander, E. 1903. Bcitriige zur Morphologic der mannlichen Geschlechts- 
 anhange der Lepidopteren. Zcits. wiss. Zool., bd. 74, pp. 557- 
 615, taf. 29, figs. 1-15.* 
 
 INTEGUMENT 
 
 Dufour, L. 1824-26. Recbcrches anatomiques siir les Carabiques et sur 
 
 plusieurs autres Coleopteres. Ann. Sc. nat. ZooL, t. 2-8, pis. 
 
 Several papers. 
 Karsten, H. 1848. Harnorgane des Brachinus complanatus. Miiller's 
 
 Archiv Anat. Phys., pp. 367-374, fig- 
 Leydig, F, 1855. Zum feineren Ban der Arthropodcn. Miiller's Archiv 
 
 Anat. Phys., pp. 376-480, taf. 3- 
 Semper, C. 1857. Beobachtungen iiber die Bildung der Fliigcl, Schuppen 
 
 und Haare bei den Lepidopteren. Zeits. wiss. Zool, bd. 8, pp. 
 
 326-339. taf. IS. 
 Sirodot, S. 1858. Recherches sur les secretions chez les Insectes. Ann. 
 
 Sc. nat. ZooL, ser. 4, t. 10, pp. 141-189, 251-334, 12 pis. 
 Claus, C. 1861. Ueber die Seitendriisen der Larve von Chrysomela 
 
 populi. Zeits. wiss. Zool., bd. 11, pp. 309-314, taf. 25. 
 Landois, H. 1864. Beobachtungen iiber das Blut der Insecten. Zeits. 
 
 wiss. Zool., bd. 14, pp. 55-70, taf. 7-9. 
 Landois, H. 1871. Beitrage zur Entwicklungsgeschichte der Schmetter- 
 
 lingsflugel in der Raupe und Puppe. Zeits. wiss. Zool., bd. 21, 
 
 pp. 305-316, taf. 23. 
 Candeze, E. 1874. Les moyens d'attaque et de defense chez les Insectes.. 
 
 Bull. Acad. roy. Belgique, ser. 2, t. 38, pp. 787-816. 
 Chun, C. 1876. Ueber den Bau, die Entwickelung und physiologische 
 
 Bedeutung der Rektaldriisen bei den Insekten. Abb. Senckenb. 
 
 naturf. Gesell., bd. 10, pp. 27-55, 4 taf. Separate, 1875, 31 pp., 4 
 
 taf. Frankfurt a. M. 
 Miiller, F. 1877. Ueber Haarpinsel. Filzflecke und ahnliche Gebilde auf 
 
 den Fliigeln mannlicher Schmetterlinge. Jenais Zeits. Naturw., 
 
 bd. II, pp. 99-114- 
 Scudder, S. H. 1877. Antigeny or Sexual Dimorphism in Butterflies. 
 
 Proc. Amer. Acad. Arts Sc, vol. 12, pp. 150-158. 
 Edwards, W. H. 1878. On the Larvpe of Lye. pseudargiolus and atten- 
 dant Ants. Can. Ent., vol. 10, pp. 131-136, fig. 8. 
 Forel, A. 1878. Der Giftapparat und die Analdriisen der Ameisen. 
 
 Zeits. wiss. Zool., bd. 30, supp., pp. 28-68, taf. 3, 4. 
 Miiller, F. 1878. Die Duftschuppen der Schmetterlinge. Ent. Nachr., 
 
 jhg. 4, pp. 29-32. 
 Saunders, E. 1878. Remarks on the Hairs of some of our British Hy- 
 
 menoptera. Trans. Ent. Soc. London, pp. 169-172, pi. 6. 
 
42 2 ENTOMOLOGY 
 
 Schneider, R. 1878. Die Schuppen aus den verschiedenen Fliigel- und 
 
 Korperteilen der Lepidopteren. Zeits. gesammt. Naturw., bd. 51, 
 
 pp. 1-59. 
 Weismann, A. 1878. Ueber Duftschuppen. Zool. Anz., jhg. i, pp. 98, 99. 
 Goossens, T. 1881. Des chenilles urticantes, etc. Ann. Soc. ent. France. 
 
 t. I, pp. 231-236. 
 Scudder, S. H. 1881. Butterflies; Their Structure, Changes and Life- 
 Histories,, with Special Reference to American Forms. 9 -j- 2,22 
 
 pp., 201 figs. New York. Henry Holt & Co. 
 Dimmock, G. 1882. On some Glands which open externally on Insects. 
 
 Psyche, vol. 3, pp. 387-401.* 
 Klemensiewicz, S. 1882. Zur naheren Kenntniss der Hantdriisen bei den 
 
 Raupen und bei Malachius. Verb. zool. -hot. Gesell. Wien, bd. 32, 
 
 pp. 459-474, 2 taf. 
 Dimmock, G. 1883. The Scales of Coleoptera. Psyche, vol. 4, pp. i-ii, 
 
 23-27, 43-47, 63-71, figs. i-ii. 
 Osten-Sacken, C. R. 1884. An Essay on Comparative Chaetotaxy, or the 
 
 Arrangement of characteristic Bristles of Diptera. Trans. Ent. 
 
 Soc. London, pp. 497-517. 
 Simmermacher, G. 1884. Untersuchungen fiber Haftapparate an Tarsal- 
 
 gliedern von Insekten. Zeits. wiss. Zool., bd. 40, pp. 481-556, taf. 
 
 25-27, 2 figs. 
 Dahl, F. 1885. Die Fussdrusen der Insekten. Archiv mikr. Anat., bd, 
 
 25, pp. 236-263, taf. 12, 13. 
 Witlaczil, E. 1885. Die Anatomic der Psylliden. Zeits. wiss. Zool., bd. 
 
 42, pp. 569-638, taf. 20-22. 
 Goossens, T. 1886. Des chenilles vesicantes. Ann. Soc. ent. France, sen 
 
 6, t. 6, pp. 461-464.* 
 Minot, C. S. 1886. Zur Kenntniss der Insektenhaut. Archiv mikr. Anat., 
 
 bd. 28, pp. 37-48, taf. 7. 
 Schaffer, C. 1889. Beitrage zur Histologic der Insekten. Zool. Jahrb., 
 
 Abth. Anat. Ont., bd. 3, pp. 611-652, taf. 29, 30. 
 Fernald, H. T, 1890. Rectal Glands in Coleoptera. Amer. Nat., vol. 24, 
 
 pp. 100, loi, pis. 4, 5. 
 Packard, A. S. 1890. Notes on some points in the external structure and 
 
 phylogeny of lepidopterous larvae. Proc. Bost. Soc. Nat. Hist., 
 
 vol. 25, pp. 82-114, pis. I, 2. 
 Borgert, H. 1891. Die Hautdriisen der Tracheaten. 81 pp.. taf. Jena. 
 Thomas, M. B. 1893. The Androconia of Lepidoptera. Amer. Nat., vol. 
 
 27, pp. 1018-1021, pis. 22, 23. 
 Cuenot, L. 1894. Le rejet de sang comme nioyen de defense chez quel- 
 
 ques Coleopteres. Compt. rend. Acad. Sc, t. 118, pp. 875-877. 
 Kellogg, V. L. 1894. The Taxonomic Value of the Scales of the Lepidop- 
 tera. Kansas Univ. Quart., vol. 3, pp. 45-89, pis. 9, 10, figs. 1-17. 
 Packard, A. S. 1894. A Study of the Transformations and Anatomy of 
 
 Lagoa crispata, a Bombycine Moth. Proc. Amer. Phil.' Soc, vol. 
 
 32, pp. 275-292, pis. 1-7. 
 
LITERATURE 423 
 
 Lutz, K. G. 1895. Das Bluten der Coccinelliden. Zool. Anz., jhg. 18, 
 
 pp. 244-255, I fig. 
 Packard, A. S. 1895-96. The Eversible Repugnatorial Scent Glands of 
 
 Insects. Journ. N. Y. Ent. Soc, vol. 3, pp. 1 10-127, pi. 5; vol. 4, 
 
 pp. 26-32.* 
 Spuler, A. 1895. Beitrag zur Kenntniss des feineren Baues und der Phy- 
 
 logenie der Fliigelbedeckung der Schmetterlinge. Zool. Jahrb., 
 
 Abth. Anat. Ont., bd. 8, pp. 520-543, taf. 36. 
 Mayer, A. G. 1896. The Development of the Wing Scales and their Pig- 
 ment in Butterflies and Moths. Bull. Mus. Comp. Zool, vol. 29, 
 
 pp. 209-236, pis. 1-7.* 
 Bordas, L. 1897. Description anatomique et etude histologique des 
 
 glandes a venin des Insectes hymenopteres. 53 pp., 2 pis. Paris. 
 Cuenot, L. 1897. Sur la saignee reflexe et les moyens de defense de 
 
 quelques Insectes. Arch. Zool. exp., ser. 3, t. 4, pp. 655-680, 4 figs. 
 Hilton, W. A. 1902. The Body Sense Hairs of Lepidopterous Larvae. 
 
 Amer. Nat., vol. 36, pp. 561-578, figs. 1-23.* 
 Tower, W. L. 1902. Observations on the Structure of the Exuvial Glands 
 
 and the Formation of the Exuvial Fluid in Insects. Zool. Anz., 
 
 bd. 25, pp. 466-472, figs. 1-8. 
 Tower, W. L. 1903. The Development of the Colors and Color Patterns 
 
 of Coleoptera, with Observations upon the Development of Color 
 
 in Other Orders of Insects. Univ. Chicago, Decenn. Publ., vol. 
 
 10, 140 pp., 3 pis. 
 Plotnikow, W. 1904. Uber die Hautung und iiber einige Elemente der 
 
 Haut bei den Insekten. Zeits. wiss. Zool., bd. 76, pp. 333-3^6, 
 
 taf. 21, 22, 2 figs. 
 
 MUSCULAR SYSTEM 
 Lyonet, P. 1762. Traite anatomique de la Chenille, qui ronge le Bois de 
 
 Saule. Ed. 2. 22 -f- 616 pp., 18 pis. La Haye. 
 Straus-Diirckheim, H. 1828. Considerations generales sur I'anatomie 
 
 comparee des animaux articules, etc. 434 pp., 10 pis. Paris. 
 Newport, G. 1839. Insecta. Todd's Cyclopaedia Anat. Phys., vol. 2, pp. 
 
 853^94. figs. 329-439- 
 Lubbock, J. 1859. On the Arrangement of the Cutaneous Muscles of the 
 
 Larva of Pygasra bucephala. Trans. Linn. Soc. Zool, vol. 22, pp. 
 
 163-191, 2 pis. 
 Basch, S. 1865. Skelett und Muskeln des Kopfes von Termes. Zeits. 
 
 wiss. Zool., bd. 15, pp. 55-75, I taf. 
 Plateau, F. 1865, 1866. Sur la force musculaire des insectes. Bull. Acad. 
 
 roy. Belgique, ser. 2, t. 20, pp. 732-757; t. 22, pp. 283-308. 
 Merkel, F. 1872, 1873. Der quergestreifte Muskel. Archiv mikr. Anat., 
 
 bd. 8, pp. 244-268, 2 taf. ; bd. 9, pp. 293-307. 
 Lubbock, J. 1877. On some Points in the Anatomy of Ants. Month. 
 
 Micr. Journ., vol. 18, pp. 121-142, pis. 189-192. 
 Lubbock, J. 1879. On the Anatomy of Ants. Trans. Linn. Soc. Zool., 
 
 ser. 2, vol. 2, pp. 141-154, 2 pis. 
 
424 ENTOMOLOGY 
 
 Poletajeff, N. 1879. Du developpement des muscles d'ailes chez les Odo- 
 nates. Horse Soc. Ent. Ross., t. 16, pp.- 10-37, 5 pls- 
 
 Von Lendenfeld, R. 1881. Der Flug der Libellen. Ein Beitrag zur Anat- 
 omic vmd Physiologie der Flugorgane der Insecten. Sitzb. Akad. 
 Wiss. Wien, bd. 83, pp. 289-376, taf. 1-7. 
 
 Luks, C. 1883. Ueber die Brustmuskulatur der Insecten. Jenais. Zeits. 
 Naturw., bd. 16, pp. 529-552, taf. 22, 23. 
 
 Dahl, F. 1884. Beitrage zur Kenntnis des Baues und der Funktionen der 
 Insektenbeine. Archiv Naturg., jhg. 50, bd. i, pp. 146-193, taf. 
 II-I3- 
 
 Van Gehuchten, A. 1886. fitude sur la structure intime de la cellule mus- 
 culaire striee. La Cellule, t. 2, pp. 289-453, pls. 1-6. 
 
 Miall, L. C, and Denny, A. 1886. The Structure and Life-history of the 
 Cockroach. London and Leeds.* (See pp. 71-84.) 
 
 Kblliker, A. 1888. Zur Kenntnis der quergestreiften Muskelfasern. 
 Zeits. wiss. Zool., bd. 47, pp. 689-710, taf. 44, 45. 
 
 Biitschli, 0., und Schewiakoff, W. 1891. Ueber den feineren Ban der 
 quergestreiften Muskeln von Arthropoden. Biol. Centralb., bd. 
 II, PP- 33-39, figs. 1-7- 
 
 Rollet, A. 1891. Ueber die Streifen N (Nebenscheiben), das Sarko- 
 plasma und Contraktion der quergestreiften Muskelfasern. Ar- 
 chiv mikr. Anat., bd. ZT, pp. 654-684, taf. zi- 
 
 Janet, C. 1895. fitudes sur les Fourmis, les Guepes et les Abeilles. 
 Note 12. Structure des Membranes articulaires des Tendons et 
 des Muscles (Myrmica, Camponotus, Vespa, Apis). 26 pp., w 
 figs. Limoges. 
 
 Janet, C. 1895. Sur les Muscles des Fourmis, des Guepes et des Abeilles. 
 Compt. rend. Acad. Sc, t. 121, pp. 610-613, i fig. 
 
 NERVOUS SYSTEM 
 
 Newport, G. 1832, 1834. On the Nervous System of the Sphinx Ligustri 
 Linn., and on the changes which it undergoes during a part of the 
 Metamorphoses of the Insect. Phil. Trans. Roy. Soc. London, 
 vol. 122, pp. 383-398, 2 pis.* Part II. Phil. Trans.. Roy. Soc. 
 London, vol. 124, pp. 389-423, 5 pis. 
 
 Blanchard, E. 1846. Recherches anatomiques et zoologiques sur le sys- 
 teme nerveux des animaux sans vertebres. Du systeme nerveux 
 des insectes. Ann. Sc. nat. Zool., ser. 3, t. 5, pp. 273-379, 8 pis. 
 
 Leydig, F. 1857. Lehrbuch der Histologic des Menschen und der Thicre. 
 12 -|- 551 pp., figs. Frankfurt. 
 
 Leydig, F. 1864. Vom Bau des Ticrischeii Korpers. Tubingen. 
 
 Brandt, E. 1876. Recherches anatomiques et morphologiques sur le sys- 
 teme nerveux des Insectes Hymenoptercs. Compt. rend. Acad. 
 Sc, t. 83, pp. 613-616. 
 
 Dietl, M. J. 1876. Die Organisation des Arthropodengehirns. Zeits. 
 wiss. Zool, bd. 27, pp. 488-517, taf. 36-38. 
 
LITERATURE 4-5 
 
 Flogel, J. H. L. 1878. Ucbcr den einlicitlichen Bau des Gfliirns in den 
 
 verschiedenen Insecten-Ordnungcn. Zeits. wiss. Zool., bd. 30, 
 
 SuppL, pp. 556-592, taf. 23, 24. 
 Brandt, E. 1879. [Many articles on the nervous system.] IIor?e Soc. 
 
 Ent. Ross., hd. 14-15. taf.* 
 Newton, E. T. 1879. On the Brain of the Cockroach, Blatta orientaHs. 
 
 Quart. Journ. Micr. Soc, n. s., vol. 19, pp. 340-356, pis. 15, 16. 
 Michels, H. 1880. Beschrcibung des Nervensystems von Oryctes nasicor- 
 
 nis im Larven-, Puppen- und Kaferzustandc. Zeits. wiss. Zool, 
 
 bd. 34, pp. 641-702, taf. 33-36. 
 Packard, A. S. 1880. The Brain of the Locust. Second Rcpt. U. S. Ent. 
 
 Comm.. pp. 223-242, pis. 9-15, fig. 9. Washington.* 
 Cattie, J. T. 1881. Beitriige zur Kenntnis der Chorda supra-spinalis der 
 . Lepidoptera und des ccntralen, peripherischen und sympathischen 
 
 Nervensystems der Raupen. Zeits. wiss. Zool., bd. 35, pp. 304- 
 
 320, taf. 16. 
 Koestler, M. 1883. Ueber das Eingeweidenervensystem von Periplaneta 
 
 oricntalis. Zeits. wiss. Zool., bd. 39, pp. 572-595, taf. 34. 
 Viallanes, H. 1884-87. fitudes histologiques et organologiques sur les 
 
 centres nerveux et les organes des sens des animaux articules. 
 
 ^lem. 1-5. Ann. Sc. nat. Zool., ser. 6, t. 17-19; sen 7, t. 2, 4; 
 
 22 pis. 
 
 Leydig, F. 1885. Zelle und Gewebe. Nene Beitrage zur Histologie des 
 
 Tierkorpers. 219 pp., 6 taf. Bonn. 
 Viallanes, H. 1887. Sur la morphologic comparee du cerveau des Insectes 
 
 et des Crustaces. Compt. rend. Acad. Sc, t. 104, pp. 444-447. 
 Binet, A. 1894. Contribution a I'etude du system nerveux sous-intestinal 
 
 des insectes. Journ. Anat. Phys,, t. 30, pp. 449-580, pis. 12-15, 
 
 23 figs. 
 
 Pawlovi, M. I. 1895. On the Structure of the Blood-Vessels and Sympa- 
 thetic Nervous System of Insects, particularly Orthoptera. Works 
 Lab. Zool. Cab. Imp. Univ. Warsaw, pp. 96 -|- 22, tab. 1-6. In 
 Russian. 
 
 Holmgren, E. 1896. Zur Kenntnis des Hauptnervensystems der Arthro- 
 poden. Anat. Anz., bd. 12, pp. 449-457, 7 figs. 
 
 Kenyon, F. C. 1896. The Brain of the Bee. Journ. Comp. Neurol., vol. 
 6. pp. 133-210, pis. 14-22. 
 
 Kenyon, F. C. 1896. The meaning and structure of the so-called "mush- 
 room bodies " of the hexapod brain. Amer. Nat., vol. 30, pp. 643- 
 650, I ^g. 
 
 Kenyon, F. C. 1897. The optic lobes of the bee's brain in the light of 
 recent neurological methods. Amer. Nat., vol. 31, pp. 369-376, 
 pi. 9- 
 
 SENSE ORGANS; SOUNDS 
 
 Miiller, J. 1826. Zur vergleichenden Physiologie des Gesichtsinnes der 
 Menschen und der Tiere. 462 pp., 8 taf. Leipzig. 
 
426 ENTOMOLOGY 
 
 Von Siebold, C. T. E. 1844. Ueber das Stimm- und Gehor-Organ der 
 
 Orthopteren. Archiv Naturg. jhg. 10, pp. 52-81, fig. 
 Gottsche, C. M. 1852. Beitrag zur Anatomic und Phj'siologie des Anges 
 
 der Krebse und Fliegen. Miiller's Archiv Anat. Phys., pp. 483- 
 
 492. 
 Claparede, E. 1859. Zur jMorphologie der zusammengesetzten Augen bei 
 
 den Arthropoden. Zeits. wiss. ZooL, bd. 10, pp. 191-214, 3 taf. 
 Hensen, V. 1866. Ueber das Gehororgan von Locusta. Zeits. wiss. Zool., 
 
 bd. 16, pp. 190-207, I taf. 
 Landois, H. 1868. Das Gehororgan des Hirschkafers. Archiv mikr. 
 
 Anat., bd. 4, pp. 88-95. 
 Schultze, M. 1868. Untersuchungen iiber die zusammengesetzten Augen 
 
 der Krebse und Insekten. 8 + 32 pp., 12 taf. Bonn. 
 Scudder, S. H. 1868. The Songs of the Grasshoppers. Amer. Nat., vol. 
 
 2, pp. 1 13-120, 5 figs. 
 Scudder, S. H. 1868. Notes on the Stridulation of Grasshoppers. Proc. 
 
 Bost. Soc. Nat. Hist., vol. 11, pp. 306-313. 
 Graber, V. 1872. Bemerkungen iiber die Gehor- und Stimmorgane der 
 
 Heuschrecken und Cicaden. Sitzb. Akad. Wiss. Wien, math.- 
 
 naturw. CI., bd. 66, pp. 205-213, 2 figs. 
 Paasch, A. 1873. Von den Sinnesorganen der Insekten im Allgemeinen, 
 
 von Gehor- und Geruchsorganen im Besondern. Archiv Naturg., 
 
 jhg. 39, bd. I, pp. 248-275. 
 Forel, A. 1874. Les fourmis de la Suisse. Neue Denks. allg. Schweiz. 
 
 Gesell. Naturw., bd. 26, 480 pp., 2 taf. Separate, 1874, 4 + 457 
 
 pp., 2 taf. Geneve. 
 Mayer, A. M. 1874. Experiments on the supposed Auditory Apparatus 
 
 of the Mosquito. Amer. Nat., vol. 8, pp. 577-592, fig. 92. 
 Ranke, J. 1875. Beitrage zu der Lehre von den Uebergangs-Sinnesor- 
 
 ganen. Das Gehororgan der Acridier und das Sehorgan der 
 
 Hirudineen. Zeits. wiss. ZooL, bd. 25, pp. 143-164, taf. 10. 
 Schmidt, 0. 1875. Die Gehororgane der Heuschrecken. Archiv mikr. 
 
 Anat., bd. 11, pp. 195-215, taf. 10-12. 
 Graber, V. 1876. Die tympanalen Sinnesapparate der Orthopteren. 
 
 Denks. Akad. Wiss. Wien, bd. 36, pp. 1-140, 10 taf. 
 Graber, V. 1876. Die abdominalen Tympanalorgane der Cicaden und 
 
 Gryllodeen. Denks. Akad. Wiss. Wien, bd. 36, pp. 273-296, 2 taf. 
 Mayer, P. 1877. Der Tonapparat der Cikaden. Zeits. wiss. Zool., bd. 
 
 28, pp. 79-92, 3 figs. 
 Forel, A. 1878. Beitrag zur Kenntniss der Sinnesempfindungen der In- 
 sekten. Mitth. Miinch. ent. Vereins, jhg. 2, pp. 1-21. 
 Lowne, B. T. 1878. On the Modifications of the Simple and Compound 
 
 Eyes of Insects. Phil. Trans. Ro}-. Soc. London, vol. 169, pp. 
 
 577-602, pis. 52-54. 
 Graber, V. 1879. Ueber neue, otocystenartige Sinnesorgane der Insekten. 
 
 Archiv mikr. Anat., bd. 16, pp. 35-37, 2 taf. 
 
LITERATURE 427 
 
 Grenacher, H. 1879. Untersuchungen iiber das Sehorgan der Arthro- 
 
 poden, insbesondere der Spinnen, Insckten und Crustaceen. 8 + 
 
 188 pp., II laf. Gottingen. 
 Hauser, G. 1880. Physiologische und histiologische Untersuchungen uber 
 
 das Geruchsorgan der Insekten. Zeits. wiss. Zool, bd. 34, pp. 
 
 367-403, taf. 17-19. 
 Graber, V. 1882. Die chordotonalen Sinnesorgane und das Gehor der 
 
 Insecten. Archiv mikr. Anat., bd. 20, pp. 506-640, taf. 30-35, 6 
 
 figs.; bd. 21, pp. 65-145. 4 figs.* 
 Lubbock, J. 1882. Ants, Bees and Wasps. 19 -f- 448 pp., 5 pis., 31 figs. 
 
 London. 1884, 1901, New York. D. Appleton & Co. 
 Graber, V. 1883. Fundamentalversuche iiber die Helligkeits- und Far- 
 
 bencmpfindlichkeit augenloser und geblendeter Tiere. Sitzb. 
 
 Akad. Wiss. Wien, bd. 87, pp. 201-236. 
 Carriere, J. 1884. On the Eyes of some Invertebrata. Quart. Journ. 
 
 Micr. Sc, vol. 24 (n. s.), pp. 673-681, pi. 45. 
 Graber, V. 1884. Grundlinien zur Erforschung des Helligkeits und Far- 
 
 bensinnes der Tiere. 8 -J- s^2 pp. Prag und Leipzig. 
 Lee, A. B. 1884. Bemerkungen iiber den feineren Bau der Chordotonal- 
 
 Organe. Archiv mikr. Anat., bd. 23, pp. 133-140, taf. 7b. 
 Lowne, B. T. 1884. On the Compound Vision and the Morphology of the 
 
 Eye in Insects. Trans. Linn. Soc. Zool, vol. 2, pp. 389-420, pis. 
 
 40-43- 
 Carriere, J. 1885. Die Sehorgane der Thiere, vergleichend anatomisch 
 
 dargestellt. 6 -\- 205 pp., I taf., 147 figs. Miinchen und Leipzig. 
 
 R. Oldenbourg. 
 Hickson, S. J. 1885. The Eye and Optic Tract of Insects. Quart. Journ. 
 
 INIicr. Sc, vol. 25, pp. 215-251, pis. 15-17- 
 Plateau, F. 1885. Experiences sur le role des palpes chez les Arthro- 
 
 podes maxilles. Palpes des Insectes broyeurs. Bull. Soc. zool. 
 
 France, t. 10, pp. 67-90. 
 Plateau, F, 1885-88. Recherches .experimentales sur la vision chez les 
 
 Insectes. Bull. Acad. roy. Belgique, ser. 3, t. 10, 14, 15, 16. Mem. 
 
 Acad. roy. Belgique, t. 43, pp. 1-91. 
 Will, F. 1885. Das Geschmacksorgan der Insekten. Zeits. wiss. Zool., 
 
 bd. 42, pp. 674-707, taf. 27. 
 Forel, A. 1886-87. Experiences et remarques critiques sur les sensations 
 
 des Insectes. Rec. zool. Suisse, t. 4, pp. 1-50, 145-240, pi. i. 
 Graber, V. 1887. Neue Versuche iiber die Funktion der Insektenfiihler. 
 
 Biol. Centralb., bd. 7, pp. 13-19. 
 Mark, E. L. 1887. Simple Eyes in Arthropods. Bull. Mus. Conip. Zool., 
 
 vol. 13, pp. 49-105, pis. 1-5- 
 Patten, W. 1887. Eyes of Molluscs and Arthropods. Journ. Morph., 
 
 vol. I, pp. 67-92, pi. 3. 
 Will, F. 1887. A. Forel. Sur les Sensations des Insectes. Ent. Nachr., 
 
 jhg. 13, pp. 227-233. 
 
428 ENTOMOLOGY 
 
 Patten, W. 1887, 1888. Studies on the Eyes of Arthropods. I. Develop- 
 ment of the Eyes of Vespa, with Ohservations on the Ocelli of 
 
 some Insects. Journ. Morph., vol. i, pp. 193-226, i pi. II. Eyes 
 
 of Acilius. Journ. Morph.. vol. 2, pp. 97-190, pis. 7-13. 
 Lubbock, J. 1888, 1902. On the Senses, Instincts and Intelligence of 
 
 Animals, with Special Reference to Insects. 29 -|- 292 pp., 118 
 
 figs. New York. D. Appleton & Co. 
 Vom Rath, 0. 1888. Ueher die Hautsinnesorgane der Insekten. Zeits. 
 
 wiss. Zool, bd. 46, pp. 413-454- taf. 30, 31. 
 Ruland, F. 1888. Beitriige zur Kenntnis der antennalen Sinnesorgane der 
 
 Insekten. Zeits. wiss. Zool., bd. 46, pp. 602-628, taf. 21- 
 Lowne, B. T. 1889. On the Structure of the Retina of the Blowfly (Cal- 
 
 liphora erythrocephala). Journ. Linn. Soc. Zool., vol. 20, pp. 406- 
 
 417, pi. 27. 
 Packard, A. S. 1889. Notes on the Epipharynx, and the Epipharyngeal 
 
 Organs of Taste in ]\Iandibulate Insects. Psyche, vol. 5, pp. 193- 
 
 199, 222-228. 
 Pankrath, 0. 1890. Das Auge der Raupen und Phryganidenlarven. 
 
 Zeits. wiss. Zool, bd. 49, pp. 690-708, taf. 34, 35. 
 Stefanowska, M. 1890. La disposition histologique du pigment dans les 
 
 yeux des Arthropodes sous I'influence de la lumiere directe et de 
 
 I'obscurite complete. Rec. zool. Suisse, t. 5, pp. 151-200, pis. 8, 9. 
 Watase, S. 1890. On the Morphology of the Compound Eyes of Arthro- 
 pods. Studies Biol. Lab. Johns Hopk. Univ., vol. 4, pp. 287-334, 
 
 pis. 29-35. 
 Weinland, E, 1890. Ueber die Schwinger (Halteren) der Dipteren. 
 
 Zeits. wiss. Zool, bd. 51, pp. 55-166, taf. 7-11. 
 , Exner, S. 1891. Die Physiologie der fazettierten Augen von Krebsen 
 
 und Insekten. 8 + 206 pp., 8 taf., 23 figs. Leipzig und Wien. 
 Von Adelung, N. 1892. Beitrage zur Kenntnis des tibialen Gehorapparates 
 
 der Locustiden. Zeits. wiss. Zool., bd. 54, pp. 316-349, taf. 14, 15. 
 Nagel, W. 1892. Die niederen Sinne der Insekten. 68 pp., 19 figs. 
 
 Tubingen. 
 Child, C. M. 1894. Ein bisher wenig beachtetes antennales Sinnesorgan 
 
 der Insekten, mit besonderer Beriicksichtigung der Culiciden und 
 
 Chironomiden. Zeits. wiss. Zool, bd. 58, pp. 475-528, taf. 30, 31. 
 Mallock, A. 1894. Insect Sight and the Defining Power of Composite 
 
 Eyes. Proc. Roy. Soc. London, vol. 55, pp. 85-90, figs. 1-3. 
 Vom Rath, 0. 1896, Zur Kenntnis der Hautsinnesorgane und des sen- 
 
 siblen Nervensystems der Arthropoden. Zeits. wiss. Zool., bd. 61, 
 
 PP- 499-539, taf. 23, 24. 
 Redikorzew, W. 1900. Untersuchungen iiber den Bau der Ocellen der 
 
 Insekten. Zeits. wiss. Zool., bd. 68, pp. 581-624, taf. 39, 40, figs. 
 
 1-7- 
 Reuter, E. 1896. Ueber die Palpen der Rhopaloceren, etc. Acta Soc. Sc. 
 
 Fenn., t. 22, pp. 16 + 578, 6 tab. 
 
LITERATURE 4-9 
 
 Hesse, R. igoi. Untersuchungen iiber die Organe dei" Lichtcmpfindung 
 bei niederen Thieren. VII. Von den Arthropoden-Augen. Zeits. 
 wiss. Zool., bd. 70, pp. 347-473, taf. 16-21, figs, i, 2. 
 
 Schenk, 0. 1903. Die antennalen Hautsinnesorgane einiger Lepidopteren 
 iind Hymenopteren mit besonderer Beriicksichtigimg der sexuellen 
 Unterschiede. Zool. Jalirb., Al)th. Anat. Ont., bd. 17, pp. 573-6i8. 
 taf. 21, 22, 4 figs.* 
 
 DIGESTIVE SYSTEM 
 
 Dufour, L. 1824-60. [Many important papers.] Am. Sc. nat. Zool. 
 Basch, S. 1858. Untcrsucbungen iiber das cbylopoetiscbc tmd uropoctiscbe 
 
 System der Blatta orientalis. Sitzb. Akad. Wiss. Wien, math.- 
 
 naturw. CI., bd. 33, pp. 234-260, 5 taf. 
 Sirodot, S. 1858. Rechercbes sur les secretions cbez les Insectes. Ann. 
 
 Sc. nat. Zool., ser. 4, t. 10, pp. 141-189, 251-334, 12 pis. 
 Leydig, F. 1859. Zur Anatomie der Insecten. Midler's Arcbiv Anat. 
 
 Pbys., pp. 33-89, 149-183, 3 taf. 
 Fabre, J. L. 1862. 6tude sur le role du tissu adipeux dans la secretion 
 
 urinaire cbez les Insectes. Ann. Sc. nat. Zool., ser. 4, t. 19, pp. 
 
 351-382. 
 Plateau, F. 1874. Recbcrcbes sur les pbenomenes de la digestion cbez 
 
 les Insectes. Mem. Acad. roy. Belgique, t. 41, 124 pp., 3 pis. 
 De Bellesme, J. 1876. Physiologie comparee. Rechercbes experimentales 
 
 sur la digestion des insectes et en particulier de la blatte. 7 -j- 
 , 96 pp.. 3 pis. Paris. 
 Helm, F. E. 1876. Ueber die Spinndriisen der Lepidopteren. Zeits. wiss. 
 
 Zool., bd. 26, pp. 434-469, taf. 27, 28. 
 Plateau, F. 1877. Note additionelle au Memoire sur les pbenomenes de 
 
 la digestion cbez les Insectes. Bull. Acad. roy. Belgique, ser. 2, 
 
 t. 44, pp. 710-733- 
 Wilde, K. F. 1877. Untersuchungen iiber den Kaumagen der Orthop- 
 
 teren. Arcbiv Naturg., jhg. 43, bd. i, pp. 135-172, 3 taf. 
 De Bellesme, J. 1878. Travaux originaux de Physiologie comparee. I. 
 
 Insectes. Digestion, Metamorphoses. 252 pp., 5 pis. Paris. 
 Schindler, E. 1878. Beitrage zur Kenntniss der Malpighi'schen Gefasse 
 
 der Insecten. Zeits. wiss. Zool., bd. 30, pp. 587-660, taf. 38-40. 
 Krukenberg, C. F, W. 1880. Versuche zur vergleichenden Physiologie 
 
 der Verdauung und vergleichende physiologische Beitrage zur 
 
 Kenntnis der Verdauungsvorgange. Unters. pbys. Inst. Univ. 
 
 Heidelberg. 
 Frenzel, J. 1882. Ueber Bau und Tbatigkeit des Verdauungskanals der 
 
 Larve des Tenebrio molitor mit Beriicksichtigung anderer Artbro- 
 
 poden. Berl. ent. Zeits., bd. 26, pp. 267-316, taf. 5.* 
 Leydig, F. 1883. Untersuchungen zur Anatomie und Histologic der 
 
 Tbiere. 174 pp., 8 taf. Bonn. 
 
430 ENTOMOLOGY 
 
 Metschnikoff, E. 1883. Untersuchungen iiber die intrazellulare Verdau- 
 
 ung bei wirbellosen Tieren. Arb. zool. Inst. Wien, bd. 5, pp. 141- 
 168. 2 taf. 
 Schiemenz, P. 1883. Ueber das Herkommen des Futtersaftes und die 
 
 Speicheldriisen der Biene nebst einem Anhange iiber das Riech- 
 
 organ. Zeits. wiss. Zool, bd. 38, pp. 71-135, taf. 5-7. 
 Locy, W. A. 1884. Anatomy and Physiology of the family Nepidse. 
 
 Amer. Nat., vol. 18, pp. 250-255, 353-367, pls. 9-12. 
 Witlaczil, E. 1885. Zur Morphologic und Anatomie der Cocciden. Zeits. 
 
 wiss. Zool. bd. 43, pp. 149-174, taf. 5. 
 Frenzel, J. 1886. Einiges iiber den Mitteldarm der Insekten, sowie iiber 
 
 Epithelregeneration. Archiv mikr. Anat., bd. 26, pp. 229-306, taf. 
 
 7^- 
 Kniippel, A. 1886. Ueber Speicheldriisen von Insecten. Archiv Natnrg., 
 
 jhg. 52, bd. I, pp. 269-303, taf. 13, 14. 
 Cholodkovsky, N. 1887. Sur la morphologic dc I'apparcil urinairc des 
 
 Lepidoptercs. Archiv. Biol., t. 6, pp. 497-514, pi. 17. 
 Faussek, V. 1887. Beitrage zur Histologic des Darmkanals der Insekten. 
 
 Zeits. wiss. Zool., bd. 45, pp. 694-712, taf. 36. 
 Kowalevsky, A. 1887. Beitrage zur Kenntnis der nachcmbryonalen Ent- 
 
 wicklung der IMusciden. Zeits. wiss. Zool., bd. 45, pp. 542-594, 
 
 taf. 26-30. 
 Schneider, A. 1887. Ueber den Darmcanal der Arthropoden. Zool. Beitr. 
 
 von A. Schneider, bd. 2, pp. 82-96, taf. &-10. 
 Emery, C. 1888. Ueber den sogenannten Kaumagen einiger Ameisen. 
 
 Zeits. wiss. Zool., bd. 46, pp. 378-412, taf. 27-29. 
 Macloskie, G. 1888. The Poison Apparatus of the Mosquito. Amer. 
 
 Nat., vol. 22, pp. 884-888, 2 figs. 
 Blanc, L. 1889. fitude sur la secretion de la sole et sur la structure du 
 
 brin et dc la have dans le Bombj^x mori. 56 pp., 4 pis. Lyon. 
 Kowalevsky, A. 1889. Ein Beitrag zur Kenntnis der Exkretionsorgane. 
 
 Biol. Centralb., bd. 9, pp. 33-47, 65-76, 127-128. 
 Van Gehuchten, A. 1890. Recherches histologiques sur I'apparcil digestif 
 
 dc la larve dc la Ptychoptcra contaminata. I Part, fitude du 
 
 revetement epithelial ct recherches sur la secretion. La Cellule, 
 
 t. 6, pp. 183-291, pis. 1-6. 
 Gilson, G. 1890, 1893. Recherches sur Ics cellules secretantes. La soie 
 
 et les appareils sericigenes. I. Lepidoptercs; II. Trichopteres. 
 
 La Cellule, t. 6, pp. 1 15-182, pis. 1-3; t. 10, pp. 37-63, pi. 4. 
 Blanc, L. 1891. La tetc du Bombyx mori a I'etat larvaire, anatomie et 
 
 physiologic. Trav. Lab. fitud. Soie, 1889-1890, 180 pp., 95 figs. 
 
 Lyon. 
 Wheeler, W. M. 1893. The primitive number of Malpighian vessels in 
 
 Insects. Psyche, vol. 6, pp. 457-460, 485-486, 497-498, 509-510, 
 
 539-541, 545-547, 561-564. 
 
LITERATURE 43 ^ 
 
 Bordas, L. 1895. Apparcil glandulaire dcs Hymenopteres. (Glandes 
 
 salivaircs, tul)e discstif, tubes de JNIalpislii et glandes venimeuses.) 
 
 362 pp., 1 1 pis. Paris. 
 Cuenot, L. 1895. fitndes physiologiques sur les Orthopteres. Arch. 
 
 Biol. t. 14. pp. 293-341, pis. 12, 13. 
 Bordas, L. 1897. L'appareil digestif des Orthopteres. Ann. Sc. nat. ZooL. 
 
 ser. 8, t. 5, pp. 1-208, pis. 1-12. 
 Needham, J. G. 1897. The digestive epithelium of dragon fly nymphs. 
 
 Zo(5l. P.ull., vol. T, pp. 103-113, figs. i-io. 
 
 CIRCULATORY SYSTEAI 
 Newport, G. 1839. Insecta. Todd's Cyclopaedia Anat. Phys., vol. 2, pp. 
 
 853^94. figs. 329-439- 
 Newport, G. 1845. On the Structure and Development of the Blood. 
 
 Ann. Mag. Nat. Hist., vol. 15, pp. 281-284. 
 Verloren, M. C. 1847. [Memoire sur la circulation dans les insectes.] 
 
 jNIem. Acad. roy. Belgique, t. 19, 93 pp., 7 pis. 
 Blanchard, E. 1848. De la circulation dans les insectes. Ann. Sc. nat. 
 
 Zool., ser. 3, t. 9, pp. 359-398, 5 pis. 
 Ley dig, F. 1851. Anatomisches und Histologisches fiber die Larve von 
 
 Corethra plumicornis. Zeits. wiss. Zool, bd. 3, pp. 435-451, taf. 
 
 16. 
 Scheiber, S. H. i860. Vergleichende Anatomic und Physiologie der 
 
 CEstriden-Larven. Sitzb. Akad. Wiss. Wien, math.-naturw. CI., 
 
 bd. 41, pp. 409-496, 2 taf. 
 Landois, H. 1864. Beobachtungen fiber das Blut der Insekten. Zeits. 
 
 wiss. Zool., bd. 14, pp. 55-70- 3 taf. 
 Graber, V. 1871. Ueber die Blutkorperchen der Insekten. Sitzb. Akad. 
 
 Wiss. Wien, math.-naturw. CI., bd. 64, pp. 9-44- 
 Moseley, H. N. 1871. On the circulation in the wings of Blatta orientalis 
 
 and other insects, and on a new method of injecting the vessels 
 
 of insects. Quart. Journ. Micr. Sc, vol. 11 (n. s.), pp. 389-395. 
 
 I pi. 
 Graber, V. 1873. Ueber den propulsatorischen Apparat der Insekten. 
 
 Archiv mikr. Anat., bd. 9, pp. 129-196, 3 taf. 
 Graber, V. 1873. Ueber die Blutkorperchen der Insekten. Sitzb. Akad. 
 
 Wiss. Wien, math.-naturw. CI., bd. 64 (1871), pp. 9-44. 
 Graber, V. 1876. Ueber den pulsierenden Bauchsinus der Insekten. Ar- 
 chiv mikr. Anat., bd. 12, pp. 575-582, i taf. 
 Dogiel, J. 1877. Anatomic und Physiologie des Herzens der Larve von 
 
 Corethra plumicornis. Mem. Acad. St. Petersbourg, ser. 7, t. 24, 
 
 ^i'] pp., 2 pis. Separate, Leipzig. Voss. 
 Jaworovski, A. 1879. Ueber die Entwicklung des Riickengefasses und 
 
 speziell der Muskulatur bei Chironomus und einigen anderen In- 
 sekten. Sitzb. Akad. Wiss. Wien, math.-naturw. CI, bd. 80, pp. 
 
 238-258. 
 
432 ENTOMOLOGY 
 
 Plateau, F. 1879. Communication preliminaire sur les mouvements et 
 
 I'innervation de I'organe central de la circulation chez les animaux 
 
 articules. Bull. Acad. roy. Belgique, ser. 2. t. 46, pp. 203-212. 
 Zimmermann, 0. 1880. Ueber eine eigenthiimliche Bildung des Riicken- 
 
 gefasses bei einigen Ephemeridenlarven. Zeits. wiss. Zool., bd. 34, 
 
 pp. 404-406, figs. 1-4. 
 Burgess, E. 1881. Note on the aorta in lepidopterous insects. Proc. 
 
 Bost. Soc. Nat. Hist, vol. 21. pp. 153-156, figs. i-5- 
 Vayssiere, A. 1882. Recherches sur I'organisation des larves des Ephe- 
 
 merines. Ann. Sc. nat. Zool., ser. 6, t. 13, pp. 1-137, pls. i-ii. 
 Viallanes, H. 1882. Recherches sur Thistologie des Insectes, et sur les 
 
 phenomenes histologiques qui accompagnent le developpement 
 
 post-embryonnaire de ccs animaux. Ann. Sc. nat. Zool., ser. 6, t. 
 
 14, pp. 1-348, 4 pis. Bibl. ficole, bd. 26, 348 pp., 18 pis. 
 Creutzburg, N. 1885. Ueber den Kreislauf der Ephemerenlarven. Zool. 
 
 Anz., jhg. 8, pp. 246-248. 
 Poletajewa, 0. 1886. Du cceur des insectes. Zool. Anz., jhg. 9, pp. 13-15. 
 Von Wielowiejski, H. R. 1886. Ueber das Blutgewebe der Insekten. 
 
 Zeits. wiss. Zool., bd. 43, pp. 512-536. 
 Dewitz, H. 1889. Eigenthatige Schwimmbewegung der Blutkorperchen 
 
 der Gliederthiere. Zool. Anz., jhg. 12, pp. 457-464, i fig. 
 Kowalevsky, A. 1889. Ein Beitrag zur Kenntnis der Excretionsorgane. 
 
 Biol. Centralb., bd. 9, pp. 33-47, 65-76, 127-128. 
 Schaffer, C. 1889. Beitrage zur Histologic der Insekten. H. Ueber 
 
 Blutbildungsherde bei Insektenlarven. Zool. Jahrb., Abth. Anat. 
 
 Ont.. bd. 3. pp. 626-636, taf. 30. 
 Lankester, E. R. 1893. Note on the Qulom and Vascular System of 
 
 Mollusca and Arthropoda. Quart. Journ. Micr. Sc, vol. 34 (n. 
 
 s.), pp. 427-432. 
 Pawlowa, M. 1895. Ueber ampullenartige Blutcirculationsorgane im 
 
 Kopfe verschiedener Orthopteren. Zool. Anz., jhg. 18, pp. 7-13, 
 
 I fig. 
 
 FAT BODY 
 
 Dufour, L. 1826. Recherches anatomiques sur les Carabiques et sur plu- 
 
 sieurs autres Insectes Coleopteres. Du tissu adipeux splanch- 
 
 nique. Ann. Sc. nat. Zool., t. 8, pp. 29-35. 
 Meyer, H. 1848. Ueber die Entwicklung des Fettkorpers, der Tracheen 
 
 und der keimbereitenden Geschlechtstheile bei den Lepidopteren. 
 
 Zeits. wiss. Zool., bd. i, pp. 175-197, 4 taf. 
 Fabre, J. H. 1863. fitude sur le role du tissu adipeux dans la secretion 
 
 urinaire chez les Insectes. Ann. Sc. nat. Zool., ser. 4, t. 19, pp. 
 
 351-382. 
 Landois, L. 1865. Ueber die Funktion des Fettkorpers. Zeits. wiss. 
 
 Zool., bd. 15, pp. ?,7^-27^- 
 
LITERATURE 433 
 
 Schultze, M. 1865. Zur Kenntniss der Leuchtorgane von Lampyris 
 
 splcndidnla. Archiv mikr. Anat., bd. i, pp. 124-137, taf. 5, 6. 
 Gadeau de Kerville, H. 1881, 1887. Les insectes phosphorescents. T. i, 
 
 55 pp., 4 pis. ; t. 2, 13s pp. Rouen.* 
 Von Wielowiejski, H. R. 1882. Studien iiber Lampyriden. Zcits. wiss. 
 
 Zool., bd. Z7, pp. 354-428, taf. 23, 24. 
 Von Wielowiejski, H. 1883. Ueber den Fettkorper von Corcthra plumi- 
 
 cornis und seine Entwicklimg. Zool. Anz., jhg. 6, pp. 318-322. 
 Emery, C. 1884. Untersuchungen iiber Luciola italica L. Zeits. wiss. 
 
 Zool., bd. 40, pp. 338-355. taf. 19. 
 Emery, C. 1885. La luce della Luciola italica osservata ron microscopio. 
 
 Bull. Soc. Ent. Ital., anno 17, pp. 351-355- tav. 5. 
 Dubois, R. 1886. Contribution a I'etude de la production de la lumiere 
 
 par les etres vivants. Les Elaterides lumineux. Bull. Soc. zool. 
 
 France, ann. 11, pp. 1-275, pls. i-9- 
 Heinemann, C. 1886. Zur Anatomic und Physiologic der Leuchtorgane 
 
 niexikanischer Cucuyo's. Archiv niikr. Anat., bd. 27, pp. 296-382. 
 Von Wielowiejski, H. R. 1886. Ueber das Blutgewebe der Insekten. 
 
 Zeits. wiss. Zool., bd. 43, pp. 512-536. 
 Schaffer, C. 1889. Beitrage zur Histologic der Insekten. H. Ueber 
 
 Blutbildungsherde bei Liscktenlarven. Zool. Jahrb., Abth. Anat. 
 
 Out., bd. 3, pp. 626-636, taf. 30. 
 Von Wielowiejski, H. R. 1889. Beitrage zur Kenntnis der Leuchtorgane 
 
 der Insecten. Zool. Anz., jhg. 12, pp. 594-600. 
 Wheeler, W. M. 1892. Concerning the "blood tissue" of the Insecta. 
 
 Psyche, vol. 6, pp. 216-220, 233-236, 253-258, pi. 7. 
 Cuenot, L. 1895. fitudes physiologiques sur les Orthopteres. Arch. Biol, 
 
 t. 14, pp. 293-341, pis. 12, 13. 
 Schmidt, P. 1895. On the Luminosity of Midges (Chironomidse). Ann. 
 
 IXLig. Nat. Hist., ser. 6, vol. 15, pp. 133-141. Trans, from Zool. 
 
 Jahrb., Abth. Syst., etc., bd. 8, pp. 58-66, 1894. 
 
 RESPIRATORY SYSTEM 
 
 Dufour, L. 1825-60. [^lany papers on respiratory system.] Ann. Sc. nat. 
 Zool. 
 
 Dutrochet, R. J. H, 1833. Du mecanisme de la respiration des Insectes. 
 Ann. Sc! nat. Zool., t. 28, pp. 31-44. 1838. Mem. Acad. Sc. Paris, 
 t. 14, pp. 81^3. 
 
 Newport, G. 1836. On the Respiration of Insects. Phil. Trans. Roy. Soc. 
 London, vol. 126, pp. 529-566. 
 
 Grube, A. E. 1844. Beschreibung einer auffallendcn an Siisswasser- 
 schwammen lebenden Larve. (Sisyra.) Archiv Naturg., jhg. 9, 
 pp. 331-337. figs. 
 
 Newport, G. 1844. On the existence of Branchiae in the perfect State of 
 a Neuropterous Insect, Pteronarcys regalis Newm. and other spe- 
 cies of the same genus. Ann. Mag. Nat. Hist., vol. 13, pp. 21-25. 
 29 
 
434 ENTOMOLOGY 
 
 Platner, E. A. 1844. ^littheilungen iiber die Respirationsorgane und die 
 Haut der Seidenraupen. Miiller's Archiv Anat. Phys., pp. 38-49, 
 figs. 
 
 Dufour, L. 1849. Des divers modes de respiration aquatique dans les 
 insectes. Compt. rend. Acad. Sc, t. 29, pp. 763-770. 1850. Trans. 
 Ann. "Slag. Nat. Hist., sen 2, vol. 6, pp. 112-118. 
 
 Newport, G. 1851. On the Formation and the Use of the Airsacs and 
 dilated Tracheae in Insects. Trans. Linn. Soc. Zool, vol. 20, pp. 
 419-423. 
 
 Newport, G. 1851. On the Anatomy and Affinities of Pteronarcys regalis 
 Newm., etc. Trans. Linn. Soc. Zool, vol. 20, pp. 425-453, i pi. 
 
 Dufour, L. 1852. fitudes anatomiques et physiologiqnes et observations 
 sur les larves des Libellules. Ann. Sc. nat. Zool., ser. 3, t. 17, pp. 
 65-110, 3 pis. 
 
 Hagen, H. A. 1853. Leon Dnfour iiber die Larven der Libellen mit 
 Beriicksichtigung der friiheren Arbeiten. (Ueber Respiration der 
 Insecten.) Stett. ent. Zeit., bd. 14, pp. 98-106, 237-238, 260-270, 
 311-325, 334-346. 
 
 Williams, T, 1853-57. Oi'' the Mechanism of Aquatic Respiration and on 
 the Structure of the Organs of Breathing in Invertebrate Ani- 
 mals. Trans. Ann. Mag. Nat. Hist., ser. 2, vols. 12-19, ^7 p's- 
 
 Barlow, W. F. 1855. Observations of the Respiratory Movements of In- 
 sects. Phil. Trans. Roy. Soc. London, vol. 145, pp. 139-148. 
 
 Lubbock, J. i860. On the Distribution of the Tracheae in Insects. Trans. 
 Linn. Soc. Zool., vol. 23. pp. 23-50, pi. 4. 
 
 Rathke, H. 1861. Anatomisch-physiologische Untersuchungen iiber den 
 Athmungsprocess der Insecten. Schrift, phys.-oek. Gesell. Kon- 
 igsberg, jhg. i, pp. 99-138, taf. i. 
 
 Scheiber, S. H. 1862. Vergleichende Anatomic und Physiologic der 
 Q^striden-Larven. Respirationssystem. Sitzb. Akad. Wiss. Wien, 
 math.-naturw. CI., bd. 45, pp. 7-68, 3 taf. 
 
 Reinhard, H. 1865. Zur Entwicklungsgeschichte des Tracheensystems der 
 Hj-menopteren mit besonderer Beziehung auf dessen morpholo- 
 gische Bedeutung. Berl. cnt. Zeits., jhg. 9, pp. 187-218, taf. i, 2. 
 
 Landois, H., und Thelen, W. 1867. Der Tracheenverschluss bei den In- 
 sekten. Zeits. wiss. Zool., bd. 17, pp. 187-214, i taf. 
 
 Oustalet, E. 1869. Note sur la respiration chez les nymphes des Libel- 
 lules. Ann. Sc. nat. Zool., ser. 5, t. 11, pp. 370-386, 3 pis. 
 
 Pouchet, G. 1872. Developpement du systeme tracheen de I'Anophele 
 (Corethra plumicornis). Archiv. Zool. exper., t. i, pp. 217-232, 
 I fig. 
 
 Gerstacker, A, 1874. Ueber das Vorkommen von Tracheenkiemen bei 
 ausgebildeten Insecten. Zeits. wiss. Zool., bd. 24, pp. 204-252, i 
 taf. 
 
 Packard, A. S. 1874. On the Distribution, and Primitive Number of 
 Spiracles in Insects. Amer. Nat., vol. 8, pp. 531-534- 
 
LITERATURE 435 
 
 Palmen, J. A. 1877. Zur ^Morphologic des Tracheensystcms. 10 -f- 149 
 
 pp., 2 taf. Helsingfors. 
 Sharp, D. 1877. Observations on the Respiratory Action of the Carnivo- 
 rous Water Beetles (Dytiscidse). Journ. Linn. Soc. ZooL, vol. 13, 
 
 pp. 161-183. 
 Haller, G. 1878. Kleinere Bruchstiicke zur vergleichenden Anatomic der 
 
 Artliropoden. I. Ueber das Atmungsorgan der Stechmiicken- 
 
 larvcn. Archiv Natnrg., jhg. 44, bd. i, pp. 91-101, taf. 2. 
 Hagen, H. A. 1880. Beitrag zur Kenntnis des Tracheensystcms der Libel- 
 
 len-Larven. Zool. Anz., jhg. 3, pp. 157-161. 
 Hagen, H. A. 1880. Kiemenubcrreste bei einer Libelle ; glatte Muskel- 
 
 fascrn bei Insectcn. Zool. Anz., jhg. 3, pp. 304-305- 
 Poletajew, 0. 1880. Quelques mots sur les organes respiratoires des lar- 
 
 ves des Odonates. Horse Soc. Ent. Ross., t. 15, pp. 436-452, 2 pis. 
 Viallanes, H. 1880. Sur Tapparcil respiratoire et circulatoire de quelques 
 
 larvos de Dipteres. Compt. rend. Acad. Sc, t. 90, pp. 1180-1182. 
 Krancher, 0. 1881. Der Ban der Stigmen bei den Insekten. Zeits. wiss. 
 
 Zool, bd. 35, pp. 505-574- taf. 28, 29. 
 Vayssiere, A. 1882. Recherches sur I'organisation des larves des Ephe- 
 
 merines. Ann. Sc. nat. Zool., sen 6, t. 13, pp. 1-137, pis. i-ii. 
 Macloskie, G. 1883. Pneumatic Functions of Insects. Psyche, vol. 3, pp. 
 
 375-378. 
 Macloskie, G. 1884. The Structure of the Trachese of Insects. Amer. 
 
 Nat., vol. 18, pp. 567-573. figs. 1-4. 
 Plateau, F. 1884. Recherches experimentales sur les mouvements res- 
 piratoires des Insectes. Mem. Acad. roy. Belgique, t. 45, 219 pp., 
 
 7 pis., 56 figs. 
 Packard, A. S. 1886. On the Nature and Origin of the so-called " Spiral 
 
 Thread " of Trachese. Amer. Nat., vol. 20, pp. 438-442, figs. 1-3. 
 Comstock, J. H. 1887. Note on Respiration of Aquatic Bugs. Amer. 
 
 Nat., vol. 21, pp. 577-578. 
 Raschke, E. W. 1887. Die Larve von Culex nemorosus. Archiv Naturg., 
 
 jhg. 53. bd. I, pp. 133-163. taf. 5, 6. 
 Schmidt-Schwedt, E. 1887. Ueber Athmung der Larven und Puppen 
 
 von Donacia crassipes. Berlin, ent. Zeits., bd. 31, pp. 325-334, 
 
 taf. 5b. 
 Vogler, C. 1887. Die Tracheenkiemen der Simulien-Puppen. Mitt. 
 
 schweiz. ent. Gesell., bd. 7, pp. 277-282. 
 Dewitz, H. 1888. Entnehmen die Larven der Donacien vermittclst Stig- 
 men oder Athemrohren den Luftraumen der Pflanzen die sauer- 
 
 stoffhaltige Luft? Bed. ent. Zeits., bd. 32, pp. 5-6, figs, i, 2. 
 Haase, E. 1889. Die Abdominalanhange der Insekten mit Beriicksichti- 
 
 gung der Myriopoden. Morph. Jahrb., bd. 15, pp. 331-43S, taf. 
 
 14. 15- 
 Cajal, S. R. 1890. Coloration par la methode de Golgi des terminaisons 
 
 des trachees et des nerfs dans les muscles des ailes des insectes. 
 
 Zeits. wiss. Mikr., bd. 7, pp. 332-342, taf. 2, figs. 1-3. 
 
43^ ENTOMOLOGY 
 
 Dewitz, H. 1890. Einige Beobachtungen, betreffend das geschlossene 
 Tracheensystem bei Insectenlarven. Zool. Anz., jhg. 13, pp. 500- 
 504, 525-531- 
 
 Von Wistinghausen, C. 1890. Ueber Tracheenendigungen in den Sericte- 
 ricn der Raupen. Zeits. wiss. Zool., bd. 49, pp. 565-582, taf. 27.* 
 
 Miall, L. C. 1891. Some Difficulties in the Life of Aquatic Insects. Na- 
 ture, vol. 44, pp. 457-462. 
 
 Stokes, A. C. 1893. The Structure of Insect Tracheae, with Special Ref- 
 erence to those of Zaitha fluminea. Science, vol. 21, pp. 44-46, 
 figs. 1-7. 
 
 Miall, L. C. 1895, 1903. The Natural History of Aquatic Insects. 11 + 
 395 PP-j 116 figs. London and New York. Macmillan & Co. 
 
 Sadones, J. 1895. L'appareil digestif et respiratoire larvaire des Odo- 
 nates. La Cellule, t. 11, pp. 271-325, pis. 1-3. 
 
 Gilson, G., and Sadones, J. 1896. The Larval Gills of the Odonata. 
 Journ. Linn. Soc. Zool., vol. 25. pp. 413-418, figs. 1-3. 
 
 Holmgren, E. 1896. Ueber das respiratorische Epithel der Tracheen bei 
 Raupen. Festsk. Lilljeborg, Upsala, pp. 79-96, taf. 5, 6. 
 
 REPRODUCTIVE SYSTEM 
 
 Dufour, L. 1824-60. [Many papers on reproductive system.] Ann. Sc. 
 
 nat. Zool. 
 Dutrochet, R. J. H. 1833. Observations sur les organes de la generation 
 
 chez les Pucerons. Ann. Sc. nat. Zool., t. 30, pp. 204-209. 
 Von Siebold, C. T. E. 1836. Ueber die Spermatozoen der Crustaceen, In- 
 
 sccten, Gasteropoden und einiger andern wirbellosen Thiere. 
 
 Miiller's Archiv Anat. Phys., pp. 15-52, 2 taf. 
 Von Siebold, C. T. E, 1836, Fernerer Beobachtungen iiber die Spermato- 
 zoen der wirbellosen Thiere. Miiller's Archiv Anat. Phys., p. 
 
 232. 1837, pp. 381-432, taf. I. 
 Doyere, L. 1837. Observations anatomiques sur les Organes de la genera- 
 tion chez la Cigale femelle. Ann. Sc. nat. Zool., t. 7, pp. 200-206, 
 
 figs. 
 Von Siebold, C. T. E. 1838. Ueber die weiblichen Geschlechtsorgane der 
 
 Tachinen. Archiv Naturg., jhg. 4, pp. 191-201. 
 Loew, H. 1841. Beitrag zur anatomischen Kenntniss der inneren Ge- 
 
 schlechtstheile der zweifliigligen Insecten. Germar's Zeits. Ent., 
 
 bd. 3, pp. 386-406, I taf. 
 Von Siebold, C. T. E. 1843. Ueber das Receptaculum seminis der Hy- 
 
 menopteren Weibchen. Germar's Zeits. Ent., bd. 4, pp. 362-388, 
 
 I taf. 
 Stein, F. 1847. Vergleichende Anatomic und Physiologie der Insecten. 
 
 I. Monographie. Ueber die Geschlechts-Organe und den Bau des 
 
 Hinterleibes bei den weiblichen Kafern. 8+139 pp., 9 taf. 
 
 Berlin. 
 
LITERATURE 437 
 
 Brauer, F. 1855. Beitriige zur Kcnntniss dcs inncrcn Raues und der 
 
 V^erwandlung der Neuroptercn. Verli. zool.-bot. Vor. Wicn, bd. 
 
 5, pp. 700-726, 5 taf. 
 Kolliker, A. 1856. Physiologische Studien iiber die Sanicnniissigkeit. 
 
 Zeits. wiss. Zool., bd. 7, pp. 201-272, i taf. 
 Huxley, T. H. 1858-59. (^n tbc Agamic Reproduction and Morpliology 
 
 (if Apliis. Trans. Linn. Soc. Zool., vol. 22, pp. 193-236, 5 pis. 
 Lubbock, J. 1859. On tbe Ova and Pseudova of Insects. Pbil. Trans. 
 
 Roy. Soc. London, vol. 149, pp. 341-369, pis. 16-18. 
 Landois, H. 1863. Ucbcr die Verbindung der Hoden niit dem Riickenge- 
 
 fjiss bei den Insekten. Zeits. wiss. Zool., bd. 13, pp. 316-318, i 
 
 taf. 
 Claus, C. 1864. Beobachtungen iibcr die Rildung des Insekteneies. Zeits. 
 
 wiss. Zool., bd. 14, pp. 42-54, r taf. 
 Pagenstecher, H. A. 1864. Die ungescblccbtlicbe Vermebnmg der Flie- 
 
 genlarven. Zeits. wiss. Zool, bd. 14, pp. 400-416, 2 taf. 
 Wagner, N. 1865. Ueber die viviparen Gallmiickenlarven. Zeits. wiss. 
 
 Zool, bd. 15, pp. 106-117. 
 Bessels, C. 1867. Studien fiber die Entwicklung der Sexualdriisen bei den 
 
 Lepidopteren. Zeits. wiss. Zool, bd. 17, pp. 545-564, 3 taf. 
 Leydig, F. 1867. Der Eierstock und die Samentascbe der Insekten. 
 
 Nova Acta Acad. Leop. -Carol., bd. 33, 88 pp., 5 taf. 
 Biitschli, 0. 1871. Nahere Mittheilungen iiber die Entwicklung und den 
 
 Bau der Samenfaden der Insecten. Zeits. wiss. Zool, bd. 21, pp. 
 
 526-534, taf. 40, 41. 
 Nusbaum, J. 1882. Zur Entwickelungsgeschichte der Ausfiihrungsgange 
 
 der Sexualdriisen bei den Insecten. Zool. Anz., jbg. 5, pp. 637- 
 
 643. 
 Palmen, J. A. 1883. Zur vergleicbenden Anatomic der Ausfiihrungsgange 
 
 der Sexualorgane bei den Insekten. Vorlaufige Mittheilung. 
 
 ]\Iorph. Jahrb., bd. 9, pp. 169-176. 
 Will, L. 1883. Zur Bildung des Eies und des Blastoderms bei den vivi- 
 paren Aphiden. Arbeit, zool.-zoot. Inst. Univ. Wiirzburg, bd. 6, 
 
 pp. 217-258, taf. 16. 
 Palmen, J. A. 1884. Ueber paarige Ausfiihrungsgange der Geschlechts- 
 
 organe bei Insecten. Ein morphologische Untersuchung. 108 pp., 
 
 5 taf. Helsingfors. 
 Gilson, G. 1885. fitude comparee de la spermatogenese chez les Arthro- 
 
 podes. La Cellule, t. i, pp. 7-188, pis. 1-8.* 
 Schneider, A. 1885. Die Entwicklung der Geschlechtsorgane der Insecten. 
 
 Zool. Beitr. von A. Schneider, bd. i, pp. 257-300, 4 taf. Breslau. 
 Spichardt, C. 1886. Beitrag zur Entwickelung der mannlichen Genitalien 
 
 und ihrer Ausfiihrgange bei Lepidopteren. Verb, naturh. Ver 
 
 Bonn, jbg. 43, pp. 1-34, taf. i. 
 La Valette St. George. 1886, 1887. Spermatologische Beitriige. Arch. 
 
 mikr. Anat., bd. 27, pp. 1-12, taf. i, 2; bd. 28, pp. 1-13, taf. 1-4; 
 
 bd. 30, pp. 426-434, taf. 25. 
 
438 ENTOMOLOGY 
 
 Von Wielowiejski, H. R. 1886. Zur ^Morphologic des Insectenovariums. 
 
 Zool. Anz., jhg. 9, pp. 132-139. 
 Korschelt, E. 1887. Ueber einige interessante Vorgange bei der Bildung 
 
 der Insekteneier. Zeits. wiss. Zool., bd. 45, pp. 327-397, taf. 18, 19. 
 Nassonow, N. 1887. The IMorphology of Insects of Primitive Organiza- 
 tion. Studies Lab. Zool. ]Mus. ]\Iosco\v, pp. 15-86, 2 pis., 68 figs. 
 
 (In Russian.) 
 Oudemans, J. T. 1888. Beitrage zur Kenntniss der Thysanura und Col- 
 
 lembola. Bijdr. Dierk., pp. 147-226. taf. 1-3. Amsterdam. 
 Bertkau, P. 1889. Beschreibung eines Zwitters von Gastropacha quercus, 
 
 nebst allgemeinen Bemerkungen und einem Verzeichniss der 
 
 beschriebenen Arthropodenzwitter. Archiv Naturg., jhg. 55, bd. i, 
 
 pp. 75-116, figs. 1-3.* 
 Leydig, F. 1889. Beitrage zur Kenntniss des thierischen Eies im unbe- 
 
 fruchteten Zustande. Zool. Jahrb., Abth. Anat. Ont., bd. 3, pp. 
 
 287-432, taf. 11-17. 
 Lowne, B. T. 1889. On the Structure and Development of the Ovaries 
 
 and their Appendages in the Blowfly (Calliphora erythrocephala). 
 
 Journ. Linn. Soc. Zool., vol. 20, pp. 418-442, pi. 28.* 
 Ballowitz, E. 1890. Untersuchungen iiber die Struktur der Spermato- 
 
 zoen, zugleich ein Beitrag zur Lehre vom feineren Bau der kon- 
 
 traktilen Elemente. Die Spermatozoen der Lisekten. (L Cole- 
 
 opteren.) Zeits. wiss. Zool., bd. 50, pp. 317-407, taf. 12-15. 
 Henking, H. 1890-92. Untersuchungen iiber die ersten Entwicklungsvor- 
 
 gange in der Eiern der Insekten. Zeits. wiss. Zool., bd. 49, pp. 
 
 503-564, taf. 24-26; bd. 51, pp. 685-736, taf. 35-37; bd. 54, pp. 
 
 1-274. taf. 1-12. figs. 1-12. 
 Ritter, R. 1890. Die Entwicklung der Geschlechtsorgane und des Dar- 
 
 mes bei Chironomus. Zeits. wiss. Zool., bd. 50, pp. 408-427, taf. 
 
 16. 
 Heymons, R. 1891. Die Entwicklung der weiblichen Geschlechtsorgane 
 
 von Phyllodromia (Blatta) germanica L. Zeits. wiss. Zool., bd. 
 
 53, pp. 434-536, taf. 18-20. 
 Koschewnikoff, G. 1891. Zur Anatomic der mannlichen Geschlechtsorgane 
 
 der Honigbiene. Zool. Anz., jhg. 14, pp. 393-396. 
 Ingenitzky, J. 1893. Zur Kenntnis der Begattungsorgane der Libellu- 
 
 liden. Zool. Anz., jhg. 16, pp. 405-407, 2 figs. 
 Escherich, K. 1894. Anatomische Studien fiber das mjinnliche Genital- 
 system der Coleoptcren. Zeits. wiss. Zool. bd. 57, pp. 620-641, 
 
 taf. 26, figs. 1-3. 
 Toyama, K. 1894. On the Spermatogenesis of the Silk Worm. Bull. 
 
 Coll. Agr. Univ. Tokyo, vol. 2, pp. 125-157. pis. 3, 4. 
 Verson, E. 1894. Zur Spermatogenesis bei der Seidenraupe. Zeits. wiss. 
 
 Zool., bd. 58, pp. 303-313. taf. 17. 
 Kluge, M. H. E. 1895. Das mannliche Geschlechtsorgan von Vespa ger- 
 manica. Archiv Naturg., jhg. 61, bd. i, pp. 159-198, taf. 10. 
 Peytoureau, A. 1895. Contributions a I'etude de la morphologic de I'ar- 
 
 mure genitale des Insectes. 248 pp., 22 pis., 43 figs. Paris. 
 
LITERATURE 439 
 
 Wilcox, E. V. 1895. Spermatogenesis of Caloptcnus fenuir-rubi-um and 
 Cicada libicen. Bull. Mus. Comp. ZooL, vol. 27, pp. 1-32, pis. 
 
 Wilcox, E. V. 1896. l""urtlicr Studies on the Spermatogenesis of Calop- 
 tcnus fcmur-rubruin. Bull. Mus. Comp. Zool, vol. 29, pp. 193- 
 _'o_'. pis. 1-3. 
 
 Fenard, A. 1897. Recherches sur les organes complementaires internes 
 de I'appareil genital des Orthoptcres. Bull. sc. France Belgique, 
 t. 29, pp. 390-533. pis. 24-28. 
 
 Gross, J. 1903. Untersuchungen iiber die Histologic des Insectenovari- 
 ums. Zool. Jahrb., Abth. Anat. Ont., bd. 18, pp. 71-186, taf. 6-14.* 
 
 Griinberg, K. 1903. Untersuchungen iiber die Keim- und Niihrzellen in 
 den Hoden und Ovarien der Lepidoptera. Zeits. wiss. Zool., bd. 
 74, pp. 327-395. taf. i(>-i8. 
 
 Holmgren, N. 1903. Ueber vivipare Insecten. Zool. Jahrb., bd. 19, pp. 
 431-468, 10 figs.* 
 
 EMBRYOLOGY 
 
 Rathke, H. 1844. Ueber die Eier von Gryllotalpa und ihre Entwickelung. 
 
 Miiller's Archiv Anat. Phys., bd. 2, pp. 27-37, figs. 1-5. 
 Meyer, G. H. 1848. Ueber Entw^icklung des Fettkorpers, der Tracheen 
 
 und der keimbereitenden Geschlechtstheile bei den Lepidopteren. 
 
 Zeits. wiss. Zool, bd. i. pp. 175-197, 4 taf. 
 Leuckart, R. 1858. Die Fortpflanzung und Entwicklung der Pupiparen 
 
 nach Beobachtungen an Melophagus ovinus. Abh. naturf. Gesell. 
 
 Halle, bd. 4, pp. 145-226, 3 taf. 
 Weismann, A. 1863. Die Entwicklung der Dipteren im Ei, nach Beobacht- 
 ungen an Chironomus spec, Musca vomitoria und Pulex canis. 
 
 Zeits. wiss. Zool., bd. 13, pp. 107-220, 7 taf. Separate, 1864, 263 
 
 pp., 14 taf. 
 Metschnikoff, E. 1866. Embryologische Studien an Insecten. Zeits. wiss. 
 
 Zool, bd. 16, pp. 389-500, 10 taf. 
 Brandt, A. 1869. BeitrJige zur Entwicklungsgeschichte der Libelluliden 
 
 und Hemipteren. Mem. Acad. St. Petersbourg. ser. 7, t. 13, pp. 
 
 1-33. 3 pis. 
 Melnikow, N. 1869. Beitrage zur Embryonalentwicklung der Insekten. 
 
 Archiv Naturg., jhg. 35, bd. i, pp. 136-189, 4 taf. 
 Biitschli, 0. 1870. Zur Entwicklungsgeschichte der Biene. Zeits. wiss. 
 
 Zool, bd. 20, pp. 519-564, taf. 24-27. 
 Kowalevsky, A. 1871. Embryologische Studien an Wiirmern und Ar- 
 
 thropoden. Mem. Acad. St. Petersbourg, ser. 7, t. 16, pp. 1-70, 
 
 12 pis. 
 Dohrn, A. 1875. Notizen zur Kenntniss der Insectenentwicklung. Zeits. 
 
 wiss. Zool., bd. 26, pp. 1 12-138. 
 Batschek, B. 1877. Beitrage zur' Entwicklungsgeschichte der Lepidop- 
 teren. Jenais. Zeits. Naturw., bd. n. 38 pp., 3 taf., 2 tigs. 
 
440 ENTOMOLOGY 
 
 Bobretzky, N. 1878. Ueber die Bildung des Blastoderms und der Keim- 
 
 blatter bei den Insecten. Zeits. wiss. Zool., bd. 31, pp. 195-215, 
 
 taf. 14. 
 Korotneff, A. 1883. Entwicklung des Herzens bei Gryllotalpa. Zool. 
 
 Anz., jhg. 6, pp. 687-690, figs. I, 2. 
 Packard, A. S. 1883. The Embryological Development of the Locust. 
 
 Third Rept. U. S. Ent. Comm., pp. 263-285, pis. 16-21, figs. lo-ii. 
 
 Washington. 
 Will, L. 1883. Zur Bildung des Eies und des Blastoderms bei den vivi- 
 
 paren Aphiden. Arbeit, zool.-zoot. Inst. Univ. Wiirzburg, bd. 6. 
 
 pp. 217-258, taf. 16. 
 Ayers, H. 1884. On the Development of QScanthus niveus and its Para- 
 site Teleas. ]Mem. Bost. Soc. Nat. Hist., vol. 3, pp. 225-281, pis. 
 
 18-25, figs. 1-41.* 
 Patten, W. 1884. The Development of Phryganids, with a Preliminary 
 
 Note on the Development of Blatta germanica. Quart. Journ. 
 
 Micr. Sc, vol. 24 (n. s.), pp. 549-602, pis. 36a, b, c. 
 Witlaczil, E. 1884. Entwicklungsgeschichte der Aphiden. Zeits. wiss. 
 
 Zool, bd. 40, pp. 559-696, taf. 28-34.* 
 Korotneff, A. 1885. Die Embrj^ologie der Gryllotalpa. Zeits. wiss. Zool, 
 
 bd. 41, pp. 570-604, taf. 29-31. 
 Schneider, A. 1885. Ueber die Entwicklung der Geschlechtsorgane der 
 
 Insecten. Zool. Beitr. von A. Schneider, bd. i, pp. 257-300, 4 
 
 taf. Breslau. 
 Blochmann, F. 1887. Ueber die Richtungskorper bei Insecteneiern. 
 
 iNIorph. Jahrb., bd. 12, pp. 544-574, taf. 26, 27. 
 Biitschli, 0. 1888. Bemerkungen iiber die Entwicklungsgeschichte von 
 
 [Nlusca. ]\Iorph. Jahrb., bd. 14, pp. 170-174, 3 figs. 
 Cholodkovsky, N. 1888. Ueber die Bildung des Entoderms bei Blatta 
 
 germanica. Zool. Anz., jhg. 11, pp. 163-166, figs, i, 2. 
 Graber, V. 1888. Ueber die Polypodie bei Insekten-Embryonen. Morph. 
 
 Jahrb.. bd. 13, pp. 586-615, taf. 25, 26. 
 Graber, V. 1888. Ueber die primare Segmentirung des Keimstreifs der 
 
 Insekten. Morph. Jahrb., bd. 14, pp. 345-368, taf. 14, 15, 4 figs. 
 Henking, H. 1888. Die ersten Entwicklungsvorgange im Fliegenei und 
 
 freie Kernbildung. Zeits. wiss. Zool., bd. 46, pp. 289-336, taf. 23- 
 
 26, 3 figs. 
 Will, L. 1888. Entwicklungsgeschichte der viviparen Aphiden. Zool. 
 
 Jahrb., Abth. Anat Ont., bd. 3, pp. 201-286, taf. 6-10. 
 Cholodkovsky, N. 1889. Studien zur Entwicklungsgeschichte der Insek- 
 ten. Zeits. wiss. Zool., bd. 48, pp. 89-100, taf. 8. 
 Graber, V. 1889. Ueber den Bau und die phylogenetische Bedeutung der 
 
 embryonalen Bauchanhange der Insekten. Biol. Centralb., jhg. 9, 
 
 PP- 355-363- 
 Heider, K. 1889. Die Embryonalentwicklung von Hydrophilus piceus L.. 
 
 I. Theil. 98 pp., 13 taf., 9 figs. Jena. 
 
LITERATURE 44^ 
 
 Leydig, F. 1889. Beitriigc zur Kenntniss dcs thicrischen Eies im unbc- 
 
 fnichteten Zustande. Zool. Jahrb., Abth. Anat. Out., bd. 3, pp. 
 
 287-43J, taf. 11-17. 
 Nusbaum, J. iSSg. Zur l-'rasc dcr Scgmentierung des Keimstreifens und 
 
 der Bauchanhangc dcr Insektenembryoncn. Biol. Centralb., jhg. 
 
 9, pp. 516-522, fig. I. 
 Voeltzkow, A. 1889. Entwickelung ini lu von Mu.sca vomitoria. Arbeit. 
 
 zool.-zoot. Inst. Uni\-. Wiirzbnrg, bd. 9, pp. 1-48, taf. 1-4. 
 Voeltzkow, A. 1889. ]\Iekjlontlia vulgaris. Ein Beitrag zur Entwickelung 
 
 ini Ei bci Insckten. Arbeit, zool.-zoot. Inst. Univ. Wiirzburg, bd. 
 
 9, pp. 49-64, taf. 5. 
 Wheeler, W. M. 1889. The Embryology of Blatta germanica and Dory- 
 
 phora decemlineata. Journ. JNIorph., vol. 3, pp. 291-386, pis. 15- 
 
 21, figs. 1-16. 
 Carriere, J. 1890. Die Entwicklung der Mauerbiene (Chalicodoma mur- 
 
 aria I\-d)r.) im Ei. Archiv mikr. Anat., bd. 35, pp. 141-165. taf. 
 
 8, 8a. 
 Henking, H. 1890-92. Untersuchungen iiber die ersten Entwicklungsvor- 
 
 giinge in der Eiern der Insckten. Zeits. wiss. Zool., bd. 49, pp. 
 
 503-564, taf. 24-26; bd. 51. pp. 685-736, taf. 35-37; bd. 54, PP- 
 
 1-274, taf. 1-12, figs. 1-12. 
 Nusbaum, J. 1890. Zur Frage der Rtickenbildung bei den Insektenem- 
 bryoncn. Biol. Centralb., jhg. 10, pp. 110-114. 
 Ritter, R. 1890. Die Entwicklung der Geschlechtsorgane und des Dar- 
 
 mes bei Chironomus. Zeits. wiss. Zool, bd. 50, pp. 408-427, taf. 
 
 16. 
 Wheeler, W. M. 1890. On the Appendages of the Eirst Abdominal Seg- 
 ment of Embryo Insects. Trans. Wis. Acad. Sc, vol. 8, pp. 87- 
 
 140, pis. 1-3.* 
 Cholodkowsky, N. 1891. Die Embryonalentwicklung von Phyllodromia 
 
 (Blatta germanica). Mem. Acad. St. Petersbourg, ser. 7, t. 38, 
 
 4 -f 120 pp., 6 pis., 6 figs. 
 Graber, V. 1891. Ueber die embryonale Anlage des Blut- und Eettgewebes 
 
 der Insekten. Biol. Centralb., jhg. 11, pp. 212-224. 
 Wheeler, W. M. 1891. Neuroblasts in the Arthropod Embryo. Journ. 
 
 Morph., vol. 4, pp. 337-343, i fig- 
 Graber, V. 1892. Ueber die morphologische Bedeutung der ventralen 
 
 Abdominalanhange der Insekten-Embryonen. Morph. Jahrb., bd. 
 
 17, pp. 467-482, figs. 1-6. 
 Korschelt, E., und Heider, K. 1892. Lehrbuch der vergleichenden Ent- 
 
 wicklungsgeschichte der wirbellosen Thiere. Heft 2, pp. 761-890, 
 
 figs. Jena.* Trans. : 1899. 'Si. Bernard and J\I. F". Woodward. 
 
 Text-Book of the Embryology of Invertebrates. 12 + 441 pp., 198 
 
 figs. London, Swan Sonnenschein & Co., Ltd. ; New York, The 
 
 ]Macmillan Co.* 
 Wheeler, W. M. 1893. A Contribution to Insect Embryology. Journ. 
 
 Worph., vol. 8, pp. 1-160, pis. 1-6, figs. 1-7. 
 
442 ENTOMOLOGY 
 
 Heymons, R. 1895. Die Embnonalentwickelung von Dermapteren und 
 
 Orthopteren unter besonderer Beriicksichtigung der Keimblatter- 
 
 bildung. 8+136 pp., 12 taf., 33 figs. Jena. 
 Heymons, R. 1896. Grundziige der Entwickelung und des Korperbanes 
 
 von Odonaten und Ephemeriden. Anh. Abh. Akad. Wiss. Ber- 
 lin, 66 pp., 2 taf. 
 Heymons, R. 1897. Entwicklungsgeschichtliche Untersuchungen an Le- 
 
 pisma saccharina L. Zeits. wiss. Zool., bd. 62, pp. 583-631, taf. 
 
 -29, 30. 3 figs. 
 Kulagin, N. 1897. Beitriige zur Kenntnis der Entwickkmgsgeschichte 
 
 von Platygaster. Zeits. wiss. Zool, bd. 63, pp. 195-235, taf. 10, 11. 
 Claypole, A. M. 1898. The Embr3'olog3' and Oogenesis of Anurida mari- 
 
 tima (Guer.). Journ. IMorph., vol. 14, pp. 219-300, pis. 20-25, 11 
 
 figs. 
 Uzel, H. 1898. Studien iiber die Entwicklung der apterygoten Insecten. 
 
 6 + 58 pp., 6 taf., 5 figs. Berlin. 
 Wilson, E. B. 1900. The Cell in Development and Inheritance. 21 -j- 
 
 483 pp., 194 figs. New York and London. The Macmillan Co. 
 
 POSTEMBRYONIC DEVELOPMENT. METAMORPHOSIS 
 Fabre, J. L. 1856. fitude sur I'instinct et les metamorphoses des Sphe- 
 
 giens. Ann. Sc. nat. Zool., ser. 4, t. 6, pp. 137-189. 
 Fabre, J. L. 1857. Memoire sur I'hypermetamorphose et les moeurs des 
 
 Meloides. Ann. Sc. nat. Zool., ser. 4, t. 7, pp. 299-365 ; i pi. ; 1858, 
 
 t. 9, pp. 265-276. 
 Miiller, F. 1864. Fiir Darwin. Leipzig. Translation: Facts and Fig- 
 ures in aid of Darwin, London, 1869. 
 Weismann, A. 1864. Die nachembryonale Entwicklung der INIusciden 
 
 nacli Beobachtungen an Musca vomitoria und Sarcophaga car- 
 
 naria. Zeits. wiss. Zool., bd. 14, pp. 187-336. 
 Weismann, A. 1866. Die Metamorphose von Corethra plumicornis. 
 
 Zeits. wiss. Zool., bd. 16, pp. 45-127, 5 taf. 
 Trouvelot, L. 1867. The American Silk Worm. Amer. Nat., vol. i, pp. 
 
 30-38, 85-94, 145-149, -4 figs., pis. 5- 6. 
 Brauer, F. 1869. Betrachtungen iiber die Verwandlung der Insekten im 
 
 Sinne der Descendenz-Theorie. Verb, zool.-bot. Gesell. Wien, bd. 
 
 19, pp. 299-318; bd. 28 (1878), 1879. pp. 151-166. 
 Ganin, M. 1869. Beitriige zur Kenntniss der Entwickelungsgeschichte 
 
 bei den Insecten. Zeits. wiss. Zool., bd. 19, pp. 381-451, 3 taf. 
 Chapman, T. A. 1870. On the Parasitism of Rhipiphorus paradoxus. 
 
 Ann. I\Iag. Nat. Hist., ser. 4, vol. 5, pp. 191-198. 
 Chapman, T. A. 1870. Some Facts towards a Life History of Rhipi- 
 phorus paradoxus. Ann. Mag. Nat. Hist., ser. 4, vol. 6, pp. 314- 
 
 326, pi. 16. 
 Landois, H. 1871. Beitriige zur Entwickkmgsgeschichte der Schmetter- 
 
 lingsfliigel in der Raupe und Puppe. Zeits. wiss. Zool., bd. 21, pp. 
 
 305-316, taf. 23. 
 
LITERATURE 443 
 
 Packard, A. S. 1873. Our Common Insects. 225 pp.. 268 figs. Boston. 
 
 Estes and Lauriat. 
 Lubbock, J. 1874, 1883. On the Origin and Metamorphoses of Insects. 
 
 16 -|- 108 pp., 6 pis., 63 figs. London. Macmillan & Co. 
 Ganin, M. 1876. [Materials for a Knowledge of the Postembryonal De- 
 velopment of Insects. Warsaw.] (In Russian.) Abstracts: 
 
 Anier. Nat., vol. 11, 1877, pp. 423-430; Zeits. wiss. Zool., bd. 28, 
 
 1877, pp. 386-389. 
 Riley, C. V. 1877. On the Larval Characters and Habits of the Blister- 
 beetles belonging to the Genera Macrobasis Lee. and Epicauta 
 
 Fabr. ; with Remarks on other Species of the Family Meloidse. 
 
 Trans. St. Loui.? Acad. Sc, vol. 3, pp. 544-562, figs. 35-39, pi. 5. 
 Dewitz, H. 1878. Beitriige zur Kenntniss der postembrj'onalen Glied- 
 
 massenbildung bei den Insecten. Zeits. wiss. Zool., bd. 30, suppl., 
 
 pp. 7S-105, taf. 5. 
 Packard, A. S. 1878. Metamorphoses [of Locusts]. First Rept. U. S. 
 
 Ent. Comm., pp. 279-284, pis. 1-3, figs. 19, 20. 
 Dewitz, H. 1881. Ueber die Fliigelbildung bei Phryganidcn und Lepi- 
 
 dopteren. Berl. ent. Zeits., bd. 25, pp. 53-60, taf. 3, 4. 
 Metschnikoff, E. 1883. Lhitersuchungen fiber die intracellulare Verdau- 
 
 ung bei wirbellosen Thieren. Arb. zool. Inst. Wien, bd. 5, pp. 
 
 141-168, taf. 13, 14. 
 Viallanes, H. 1883. Recherches sur I'histologie des Insectes et sur les 
 
 phenomenes histologiques qui accompagnent le developpement 
 
 post-embryonnaire de ces animaux. x\nn. Sc. nat. Zool., ser. 6, t. 
 
 14, 348 pp., 18 pis. 
 "Von Wielowiejsky, H. R. 1883. Ueber den Fettkorper von Corethra 
 
 plumicornis und seine Entwicklung. Zool. Anz., jhg. 6, pp. 318- 
 
 322. 
 Kowalevsky, A. 1885. Beitnige zur nachembryonalen Entwicklung der 
 
 Musciden. Zool. Anz., jhg. 8, pp. 98-103, 123-128, 153-157. 
 Schmidt, 0. 1885. Metamorphose und Anatomic des mannlichen Aspidi- 
 
 otus nerii. Archiv Naturg., jhg. 51, bd. i, pp. 169-200, taf. 9, 10. 
 Witlaczil, E. 1885. Zur Morphologic und Anatomic der Cocciden. Zeits. 
 
 wiss. Zool., bd. 43, pp. 149-174, taf. 5. 
 Kowalevsky, A. 1887. Beitrage zur Kenntniss der nachembryonalen Ent- 
 wicklung der Musciden. Zeits. wiss. Zool, bd. 45, pp. 542-594, 
 
 taf. 26-30. 
 Van Rees, J. 1888. Beitrage zur Kenntnis der inneren Metamorphose 
 
 von Musca vomitoria. Zool. Jahrb., Abth. Anat. Ont.. bd. 3, pp. 
 
 1-134, taf. I, 2, 14 figs. 
 Hyatt, A., and Arms, J. M. 1890. Insecta. 23 -|- 300 pp., 13 pis., 223 figs. 
 
 Boston. D. C. Heath & Co.* 
 Bugnion, E. 1891. Recherches sur le developpement post-embryonnaire. 
 
 I'anatomie, et les moeurs de I'Encyrtus fuscicollis. Rec. zool. 
 
 Suisse, t. 5, pp. 435-534. pis. 20-25. 
 
444 ENTOMOLOGY 
 
 Poulton, E. B. iSgi. The External Morphology of the Lepidopterous 
 
 Pupa : its Relation to that of the other Stages and to the Origin 
 
 and History of Metamorphosis. Trans. Linn. Soc. Zool., ser. 2, 
 
 vol. 5, pp. 245-263, pis. 26. 27. 
 Korschelt, E., und Heider, K. 1892. Lehrbuch der vergleichenden Ent- 
 
 wicklungsgeschichte der wirbellosen Thiere. Heft 2, pp. 761-890, 
 
 figs. Jena.* 
 Miall, L. C, and Hammond, A. R. 1892. The Development of the Head 
 
 of Chironomus. Trans. Linn. Soc. Zool, ser. 2, vol. 5, pp. 265- 
 
 279, pis. 28-31. 
 Pratt, H. S. 1893. BeitrJige zur Kenntnis der Pupiparen. Archiv Na- 
 
 turg., jhg. 59, bd. I, pp. 151-200, taf. 6. 
 Gonin, J. 1894. Recherches sur la metamorphose des Lepidopteres. De 
 
 la formation des appendices imaginaux dans la chenille du Pieris 
 
 brassicae. Bull. Soc. vaud. Sc. nat., t. 30, pp. 1-52, 5 pis. 
 Miall, L. C. 1895. The Transformations of Lisects. Nature, vol. 53, pp. 
 
 153-158. 
 Hyatt, A., and Arms, J. M. 1896. The Meaning of Metamorphosis. Nat. 
 
 Sc, vol. 8, pp. 395-403- 
 Kulagin, N. 1897. Beitrage zur Kenntnis der Entwicklungsgeschichte 
 
 von Platygaster. Zeits. wiss. Zool., bd. 63, pp. 195-235, taf. 10, 11. 
 Packard, A. S. 1897. Notes on the Transformations of Higher Hymen- 
 
 optera. Journ. N. Y. Ent. Soc, vol. 4, pp. 155-166, figs. 1-5; vol. 
 
 5, pp. 77-87. 109-120, figs. 6-13. 
 Pratt, H. S. 1897. Imaginal Discs in Insects. Psyche, vol. 8, pp. 15-30, 
 
 IT figs. 
 
 Packard, A. S. 1898. A Text-Book of Entomology. 17 -|- 729 pp., 654 
 
 ligs. New York and London. The Macmillan Co. 
 Boas, J. E. V. 1899. Einige Bemerkungen fiber die Metamorphose der 
 
 Insecten. Zool. Jahrb., Abth. Syst., bd. 12, pp. 385-402, taf. 20, 
 
 figs. 1-3. 
 Lameere, A. 1899. La raison d'etre des metamorphoses chez les Insectes. 
 
 Ann. Soc. ent. Belg., t. 43, pp. 619-636. 
 Perez, C. 1899. Sur la metamorphose des insectes. Bull. Soc. ent. France, 
 
 pp. 398-402. 
 Wahl, B. 1901. Ueber die Entwicklung der hypodermalen Imaginalschei- 
 
 ben im Thorax und Abdomen der Larve von Eristalis Latr. Zeits. 
 
 wiss. Zool., bd. 70, pp. 171-191, taf. 9, figs. 1-4. 
 Perez, C. 1902. Contribution a I'etude des metamorphoses. Bull. sc. 
 
 France Belg., t. 37, pp. 195-427, pis. 10-12, 32 figs. 
 Deegener, P. 1904. Dfe Entwicklung des Darmcanals der Insecten 
 
 wahrend der Metamorphose. Zool. Jahrb., Abth. Anat. Out., bd. 
 
 20, pp. 499-676, taf. 33-43* 
 Powell, P. B. 1904-05. The Development of Wings of Certain Beetles, 
 
 and some Studies of the Origin of the Wings of Insects. Journ 
 
 N. Y. Ent. Soc, vol. 12, pp. 237-243, pis. 11-17; vol. 13, pp. 5-22.=^ 
 
LITERATURE 445 
 
 AQUATIC INSECTS 
 Dufour, L. 1849. Des divers modes de respiration aqualique dans les 
 
 inscctes. Compt. rend. Acad. Sc, t. 29, pp. yC.W/O- Ann. Mag. 
 
 Nat. Hist, ser. 2, vol. 6, 1850, pp. 112-118. 
 Dufour, L. 1852. fitudes anatomiques et physiologiques et observations 
 
 sur les larves des Libellules. Ann. Sc. nat. Zool., ser. 3, t. 17, pp. 
 
 65-1 10, 3 pis. 
 Hagen, H. A. 1853. Leon Dnfonr iibcr die Larvcn der Lil^ellen mit 
 
 Beriicksichtigung der friiiiercn Arbciten. (Ucbcr Respiration der 
 
 Insecten.) Stett. cnl. Zeit., bd. 14, pp. 9S-106, 237-238, 260-270, 
 
 311-325, 334-34(^- 
 
 Williams, T. 1853-57. On tbe Mecbanism of Aquatic Respiration and on 
 tbe Structure of tbe Organs of Breatbing in Invertebrate Ani- 
 mals. Ann. Mag. Nat. Hist., ser. 2, vols. 12-19, 17 pis. 
 
 Oustalet, E. 1869. Note sur la respiration cbez les nynipbes des Libel- 
 lules. Ann. Sc. nat. Zool., ser. 5, t. 11, pp. 370-386, 3 pis. 
 
 Sharp, D. 1877. Observations on the Respiratory Action of the Carniv- 
 orous Water Beetles (Dytiscidae). Journ. Linn. Soc. Zool, vol. 
 13, pp. 161-183. 
 
 Poletajew, 0. 1880. Quelques mots sur les organes respiratoires des lar- 
 ves des Odonates. Horse Soc. Ent. Ross., t. 15, pp. 436-4S2, 2 pis. 
 
 Vayssiere, A. 1882. Recherches sur Torganisation des larves des Ephe- 
 merines. Ann. Sc. nat. Zool., ser. 6, t. 13, pp. i-i37, pls- i-H- 
 
 Macloskie, G. 1883. Pneumatic Functions of Insects. Psyche, vol. 3, pp. 
 375-378. 
 
 White, F. B. 1883. Report on the Pelagic Hemiptera. Rept. Sc. Res. 
 Voy. H. M. S. Challenger, 1873-1876, Zoology, vol. 7, 82 pp., 3 pis. 
 
 Comstock, J. H. 1887. Note on Respiration of Aquatic Bugs. Amer. 
 Nat., vol. 21, pp. 577-578. 
 
 Schwedt, E. 1887. Ueber Athmung der Larven und Puppen von Donacia 
 crassipes. Bed. ent. Zeits., bd. 31, pp. 325-334, taf. 5b. 
 
 Amans, P. C. 1888. Comparaisons des organes de la locomotion aqua- 
 tique. Ann. Sc. nat. Zool, ser. 7, t. 6, pp. 1-164, pis. 1-6. 
 
 Dewitz, H. 1888. Entnebmen die Larven der Donacien vermittelst Stig- 
 men oder Athemrohren den Luftraumen der Pflanzen die sauer- 
 stofifbahige Luft? Berl. ent. Zeits., bd. 32, pp. 5-6, 2 figs. 
 
 Garman, H. 1889. A Preliminary Report on the Animals of the Missis- 
 sippi Bottoms near Quincy, Illinois, in August, 1888. Bull. 111. 
 St. Lab. Nat. Hist., vol. 3, pp. 123-184. 
 
 Moniez, R. 1890. Acariens et Insectes marins des cotes du Boulonnais. 
 Rev. biol. nord France, t. 2, pp. 321, etc. 
 
 Miall, L. C. 1891. Some Difficulties in the Life of Aquatic Insects. Na- 
 ture, vol. 44, pp. 457-462. 
 
 Walker, J. J. 1893. On the Genus Halobates, Escb., and other Marine 
 Hemiptera. Ent. Mon. Mag., ser. 2, vol. 4 (29), pp. 2.2'j-2i2. 
 
 Carpenter, G. H. 1895. Pelagic Hemiptera. Nat. Sc, vol. 7, pp. 60-61. 
 
446 ENTOMOLOGY 
 
 Hart, C. A. 1895. On the Entomologj' of the IlHnois River and Adjacent 
 
 Waters. Bull. 111. St. Lab. Nat. Hist., vol. 4, pp. 149-273, pis. 
 
 I-I5- 
 Miall, L. C. 1895, 1903. The Natural History of Aquatic Insects. 11 -f 
 
 395 PP-. 116 figs. London and New York. Macmillan & Co.* 
 Sadones, J. 1895. L'appareil digestif et respiratoire larvaire des Odo- 
 
 nates. La Cellule, t. 11, pp. 271-325, pis. 1-3. 
 Gilson, G., and Sadones, J. 1896. The Larval Gills of the Odonata. 
 
 Journ. Linn. Soc. Zool., vol. 25, pp. 413-418, figs. 1-3. 
 Comstock, J. H. 1897, 1901. Insect Life. 6 + 349 pp., 18 pis., 296 figs. 
 
 New York. D. Appleton & Co.* 
 Needham, J. G. 1900. Insect Drift on the Shore of Lake Michigan. 
 
 Occas. Mem. Chicago Ent. Soc, vol. i, pp. 1-8, i fig. 
 Needham, J. G., and Betten, C. 1901. Aquatic Insects in the Adirondacks. 
 
 Bull. N. Y. St. ]\Ius., no. 47, pp. 383-612, 36 pis., 42 figs. 
 Needham, J. G., MacGillivray, A. D., Johannsen, 0. A., and Davis, K. C. 
 
 1903. Aquatic Insects in New York State. Bull. N. Y. St. Mus., 
 
 no. 68, 321 pp., 52 pis., 26 figs.* 
 
 COLOR AND COLORATION 
 
 Dorfmeister, G. 1864. LTeber die Einwirkung verschiedener, wahrend 
 den Entwicklungsperioden angewendeter Warmegrade auf die 
 Farbung und Zeichnung der Schmetterlinge. Mitth. naturw. Ver. 
 Steiermark, pp. 99-108, I taf. 
 
 Landois, H. 1864. Beobachtungen iiber das Blut der Insecten. Zeits. 
 wiss. Zool., bd. 14, pp. 55-70, taf. 7-9. 
 
 Wood, T. W. 1867. Remarks on the Coloration of Chr3'salides. Trans. 
 Ent. Soc. London, ser. 3, vol. 5, Proc, pp. 99-101. 
 
 Higgins, H. H. 1868. On the Colour-Patterns of Butterflies. Quart. 
 Journ. Sc, vol. 5, pp. 323-329, i pi. 
 
 Weismann, A. 1875. Studien zur Descendenztheorie. I. Ueber den 
 Saison Dimorphismus der Schmetterlinge. Leipzig. Trans.: 
 1880-81. R. Meldola. Studies in the Theory of Descent. 554 
 pp., 8 pis. London. 
 
 Scudder, S. H. 1877. Antigeny, or Sexual Dimorphism in Butterflies. 
 Proc. Amer. Acad. Arts Sc. vol. 12, pp. 150-158. 
 
 Dorfmeister, G. 1880. Ueber den Einfluss der Temperatur bei der Erzeu- 
 gung der Schmetterlingsvarietaten. Mitth. naturw. Ver. Steier- 
 mark, jhg. 1879, PP- 3-8, I taf. 
 
 Scudder, S. H, 1881. Butterflies; their Structure, Changes and Life- 
 Histories, with Special Reference to American Forms. 9 -|- 322 
 pp., 201 figs. New York. Henry Holt & Co. 
 
 Hagen, H. A. 1882. On the Color and the Pattern of Insects. Proc. 
 Amer. Acad. Arts Sc, vol. 17, pp. 234-267. 
 
 Dimmock, G. 1883. The Scales of Coleoptera. Psyche, vol. 4, pp. 3-1 1, 
 23-27, 43-47, 63-71, II figs.* 
 
LITERATURE 447 
 
 Krukenberg, C. F. W. 1884. [Colors and Pigments of Insects.] Ent. 
 Nachr., jhg. 10, pp. 291-296. 
 
 Poulton, E. B. 1884. Notes upon, or suggested by the Colours, Markings 
 and Protective Attitudes of certain Lepidoptcrous Larvce and 
 Pupje, and of a phytophagous hymenopterous larva. Trans. Ent. 
 Soc. London, pp. 27-60, pi. i. 
 
 Poulton, E, B. 1885. The Essential Nature of the Colouring of Phytopha- 
 gous Larvae and their Pupre, etc. Proc. Roy. Soc. London, vol. 
 38, pp. 269-315- 
 
 Poulton, E. B. 1885. Further Notes upon the Markings and Attitudes of 
 Lepidoptcrous Larvae. Trans. Ent. Soc. London, pp. 281-329, pi. 7. 
 
 Poulton, E. B. 1887. An Enquiry into the Cause and Extent of a Special 
 Colour-Relation between Certain Exposed Pupse and the Surfaces 
 which immediately surround them. Phil. Trans. Roy. Soc. Lon- 
 don, vol. 178, pp. 311-44T, pi. 26. 
 
 Chapman, T. A. 1888. On jNIelanism in Lepidoptera. Ent. Mon. Mag., 
 vol. 25, p. 40. 
 
 Dixey, F. A. 1890. On the Phylogenetic Significance of the Wing-Mark- 
 ings in certain Genera of the Nymphalidas. Trans. Ent. Soc. Lon- 
 don, pp. 89-129, pis. 1-3. 
 
 Merrifield, F. 1890. Systematic temperature experiments on some Lepi- 
 doptera in all their stages. Trans. Ent. Soc. London, pp. 131-159, 
 pis. 4. 5- 
 
 Poulton, E. B. 1890. The Colours of Animals. 13-1-360 pp., i pi., 66 
 figs. New York. D. Appleton & Co. 
 
 Seitz, A. 1890, 1893. Allgemeine Biologic der Schmetterlinge. Zool. 
 Jahrb., Abth. Syst., etc., bd. 5, pp. 281-343; bd. 7, pp. 131-186.* 
 
 Coste, F. H. P. 1890-91. Contributions to the Chemistry of Insect Colors. 
 Entomologist, vol. 23, pp. 128-132, etc. ; vol. 24, pp. 9-15, etc. 
 
 Hopkins, F. G. 1891. Pigment in Yellow Butterflies. Nature, vol. 45, 
 pp. 197-198. 
 
 Merrifield, F. 1891. Conspicuous effects on the markings and colouring 
 of Lepidoptera caused by exposure of the pupse to different tem- 
 perature conditions. Trans. Ent. Soc. London, pp. 155-168, pi. 9. 
 
 Urech, F. 1891. Beobachtungen iiber die verschiedenen Schuppenfarben 
 und die zeitliche Succession ihres Auftretens (Farbenfelderung) 
 auf den Puppenfliigelchen von Vanessa urticse und lo. Zool. 
 Anz., jhg. 14, pp. 466-473- 
 
 Beddard, F. E. 1892. Animal Coloration. 8 -f 288 pp., 4 pis., 36 figs. 
 London, Swan Sonnenschein & Co. New York, Macmillan & Co. 
 
 Gould, L. J. 1892. Experiments in 1890 and 1891 on the colour-relation 
 between certain lepidoptcrous larvfe and their surroundings, to- 
 gether with some other observations on lepidoptcrous larvae. 
 Trans. Ent. Soc. London, pp. 215-246, pi. 11. 
 
 Merrifield, F. 1892. The effects of artificial temperature on the colouring 
 of several species of Lepidoptera, with an account of some experi- 
 ments on the effects of light. Trans. Ent. Soc. London, pp. 33-44. 
 
44^ ENTOMOLOGY 
 
 Poulton, E. B. 1892. Further experiments upon the colour-relation be- 
 tween certain lepidopterous larvce. pupje, cocoons and imagines 
 and their surroundings. Trans. Ent. Soc. London, pp. 293-487, 
 pis. 14, 15. 
 
 Urech, F. 1892. Beobachtungen iiber die zeitliche Succession der Auf- 
 tretens der Farbenfelder auf den Puppenfliigelchen von Pieris 
 brassicas. Zool. Anz., jhg. 15, pp. 284-290, 293-299. 
 
 Urech, F. 1892. Ueber Eigenschaften der Schuppenpigmente einiger 
 Lepidopteren-Species. Zool. Anz., jhg. 15, pp. 299-306. 
 
 Weismann, A. 1892, 1898. The Germ-Plasm. Trans, by W. N. Parker 
 and H. Ronnfeldt. See pp. 399-409. on climatic variation in 
 butterflies. 
 
 Dixey, F. A. 1893. On the phjdogenetic significance of the variations 
 produced by difference of temperature in Vanessa atalanta. 
 Trans. Ent. Soc. London, pp. 69-73. 
 
 Merrifield, F. 1893. The effects of temperature in the pupal stage on the 
 colouring of Pieris napi, Vanessa atalanta, Chrysophanus phloeas. 
 and Ephyra punctaria. Trans. Ent. Soc. London, pp. 55-67, pi. 4. 
 
 Poulton, E. B. 1893. The Experimental Proof that the Colours of certain 
 Lepidopterous Larvse are largely due to modified plant Pigments 
 derived from Food. Proc. Roy. Soc. London, vol. 54. pp. 417- 
 430, pis. 3, 4. 
 
 Urech, F. 1893. Beitrage zur Kenntniss der Farbe von Insektenschuppen. 
 Zeits. wiss. Zool., bd. 57, pp. 306-384. 
 
 Bateson, W. 1894. Materials for the Study of Variation treated with 
 especial Regard to Discontinuity in the Origin of Species. 16 -j- 
 598 pp., 209 figs. London and New York. Macmillan & Co. 
 
 Dixey, F. A. 1894. Mr. Merrifield's Experiments in Temperature- Varia- 
 tion as bearing on Theories of Heredity. Trans. Ent. Soc. Lon- 
 don, pp. 439-446. 
 
 Hopkins, F. G. 1894. The Pigments of the Pieridas. Proc. Roy. Soc. 
 London, vol. 57, pp. 5-6. 
 
 Kellogg, V. L. 1894. The Taxonomic Value of the Scales of the Lepidop- 
 tera. Kansas Univ. Quart., vol. 3, pp. 45-89, pis. 9, 10, figs. 1-17. 
 
 Merrifield, F. 1894. Temperature Experiments in 1893 on several species 
 of Vanessa and other Lepidoptera. Trans. Ent. Soc. London, pp. 
 425-438, pi. 9. 
 
 Hopkins, F. G. 1895. The Pigments of the Pieridse: A Contribution to 
 the Study of Excretory Substances which function in Ornament. 
 Phil. Trans. Roy. Soc. London, vol. 186, pp. 661-682. 
 
 Spuler, A. 1895. Beitrag zur Kenntniss des feineren Baues und der Phy- 
 logenie der Fliigelbedeckung der Schmetterlinge. Zool. Jahrb., 
 Abth. Anat. Ont., bd. 8, pp. 520-543, taf. 36. 
 
 ■Standfuss, M. 1895. On the Causes of Variation and Aberration in the 
 Lnago Stage of Butterflies, with Suggestions on the Establishment 
 of New Species. Trans, by F. A. Dixey. Entomologist, vol. 28, 
 pp. 69-76, 102-114, 142-150. 
 
LITERATURE 449 
 
 Mayer, A. G. 1896. The Development of the Wing Scales and their Pig- 
 ment in Butterflies and iSIoths. Bull. Mus. Comp. Zool., vol. 29, 
 pp. 209-236, pis. 1-7. 
 
 Weismann, A, 1896. New Experiments on the Seasonal Dimorphism of 
 Lepidoptera. Trans, by W. E. Nicholson. The luitomologist, 
 vol. 29, pp. 29-39, etc. 
 
 Brunner von Wattenwyl, C. 1897. Betrachtungen iiber die Farbenpracht 
 der Insekten. 16 pp., 9 taf. Leipzig. Trans, by E. J. Bles : 
 Observations on the Coloration of Insects. 16 pp., 9 pis. Leipsic. 
 
 Fischer, E. 1897-99. Bcitriige zur e.xpcrimentellen Lepidopterologie. 
 illustr. Zeits. Ent., 1x1. 2-4. 12 taf. 
 
 Mayer, A. G. 1897. On the Color and Color-Patterns of Moths and 
 Butterflies. Proc. Bost. Soc. Nat. Hist., vol. 27, pp. 243-330, pis. 
 i-io. Also Bull. jNIus. Comp. Zool., vol. 30, pp. 169-256, pis. i-io. 
 
 Von Linden, Grafin M, 1898. Untersuchungen iiber die Entwicklung der 
 Zeichnung des Schmetterlingsfliigels in der Puppe. Zeits. wiss. 
 Zool, bd. 65, pp. 1-49, taf. 1-3. 
 
 Newbigin, M. I. 1898. Colour in Nature. 12 -(-344 PP- London. John 
 Alurray.* 
 
 Von Linden, Grafin M. 1899. Untersuchungen iiber die Entwickelung der 
 Zeichnung der Schmetterlingsfliigels in der Puppe. lUustr. Zeits. 
 Ent., bd. 4, pp. 19-22. 
 
 Urech, F. 1899. Einige Bemerkungen zum zeitlichen Auftreten der 
 Schuppen-Pigmentstofife von Pieris brassicae. Illustr. Zeits. Ent., 
 bd. 4, pp. 51-53. 
 
 Von Linden, la Comtesse M. 1902. Le dessin des ailes des Lepidopteres. 
 Recherches sur son evolution dans I'ontogenese et la phylogenese 
 des especes, son origine et sa valeur systematique. Ann. Sc. nat. 
 Zool., ser. 8, t. 14, pp. 1-196, pis. 1-20. 
 
 Weismann, A. 1902. Vortriige iiber Descendenztheorie. 2 vols. 12 -\- 
 456 pp., 95 figs.; 6 -|- 462 pp., 3 pis., 36 figs. Jena. G. Fischer. 
 See pp. 65-102. 
 
 Von Linden, Grafin M. 1903. Morphologische und physiologisch-chemische 
 Untersuchungen iiber die Pigmente der Lepidopteren. i. Die 
 gelben imd roten Farbstofife der Vanessen. Archiv ges. Phys., bd. 
 98, pp. 1-89, I taf., 3 figs. 
 
 Poulton, E, B. 1903. Experiments in 1893, 1894 and 1896 upon the col- 
 our-relation between lepidopterous larvae and their surroundings, 
 and especially the efifect of lichen-covered bark upon Odontopera 
 bidentata, Gastropacha quercifolia, etc. Trans. Ent. Soc. London, 
 pp. 311-374. pis. 16-18. 
 
 Tower, W. L. 1903. The Development of the Colors and Color Patterns 
 of Coleoptera, with Observations upon the Development of Color 
 in other Orders of Insects. Univ. Chicago Decenn. Publ., vol. 10, 
 pp. 1-40, pis. 1-3. 
 
 30 
 
450 ENTOMOLOGY 
 
 Vernon, H. M. 1903. Variation in Animals and Plants. 9-1-415 pp. 
 
 New York. Henry Holt & Co. 
 Enteman, W. M. 1904. Coloration in Polistes. Publ. Carnegie Inst. 
 
 Washington, no. ig, 88 pp., 6 pis., 26 figs.* 
 Von Linden, Grafin M. 1905. Physiologische Untersuchungen an Schmet- 
 
 terlingen. Zeits. wiss. Zool., bd. 82, pp. 411-444, taf. 25.* 
 
 ADAPTIVE COLORATION 
 Bates, H. W. 1862. Contributions to an Insect Fauna of the Amazon 
 
 Valley. Lepidoptera : Heliconidje. Trans. Linn. Soc. Zool., vol. 
 
 23, PP- 495-566, pis. 55, 56. 
 Wallace, A. R. 1867. [Theory of Warning Coloration.] Trans. Ent. 
 
 Soc. London, ser. 3, vol. 5, Proc, pp. 80-81. 
 Butler, A. G. 1869. Remarks upon certain Caterpillars, etc., which are 
 
 unpalatable to their enemies. Trans. Ent. Soc. London, pp. 27-29. 
 Trimen, R. 1869. On some remarkable Mimetic Analogies among Afri- 
 can Butterflies. Trans. Linn. Soc. Zool., vol. 26, pp. 497-522, pis. 
 
 42. 43- 
 Meldola, R. 1873. On a certain Class of Cases of Variable Protective 
 
 Colouring in Insects. Proc. Zool. Soc. London, pp. 153-162. 
 Miiller, F. 1879. Ituna and Thyridia ; a remarkable case of Mimicry in 
 
 Butterflies. Trans., R. Meldola, Proc. Ent. Soc. London, pp. 20- 
 
 29, figs. 1-4. 
 Blackiston, T., and Alexander, T. 1884. Protection by Mimicry — A 
 
 Problem in Mathematical Zoology. Nature, vol. 29, pp. 405-406. 
 Poulton, E. B. 1884. Notes upon or suggested by the Colours, Markings 
 
 and Protective Attitudes of certain Lepidopterous Larvje and 
 
 Pupae, and of a phytophagous hymenopterous larva. Trans. Ent. 
 
 Soc. London, pp. 27-60, pi. i. 
 Poulton, E. B. 1885. Further notes upon the markings and attitudes of 
 
 lepidopterous larvae. Trans. Ent. Soc. London, pp. 281-329, pi. 7. 
 Poulton, E. B. 1887. The Experimental Proof of the Protective Value 
 
 of Colour and Markings in Insects in reference to their Vertebrate 
 
 Enemies. Proc. Zool. Soc. London, pp. 191-274. 
 Wallace, A. R. 1889. Darwinism. 16 -f 494 PP, Zl figs. London and 
 
 New York. Macmillan & Co. 
 Poulton, E. B. 1890. The Colours of Animals. 13 -|- 360 pp., i pL, 66 
 
 figs. New York. D. Appleton & Co. 
 Beddard, F. E. 1892. Animal Coloration. 8-I-288 pp., 4 pis., 36 figs. 
 
 London, Swan Sonnenschein & Co. New York, Macmillan & Co. 
 Haase, E. 1893. Untersuchungen iiber die Mimicry auf Grundlage eines 
 
 natiirlichen Systems der Papilioniden. Bibl. Zool., Heft 8, Theil 
 
 I, 120 pp., 6 taf.; Theil 2, 161 pp., 8 taf. Trans. Theil 2, C. M. 
 
 Child, Stuttgart, 1896, 154 pp., 8 pis. 
 Finn, F. 1895-97. Contributions to the Theory of Warning Colours and 
 
 Mimicry. Journ. Asiat. Soc. Bengal, vols. 64-67. 
 Dixey, F. A. 1896. On the Relation of Mimetic Patterns to the Original 
 
 Form. Trans. Ent. Soc. London, pp. 65-79, pls. 3-5^ 
 
LITERATURE 45 1 
 
 Piepers, M. C. 1896. Miinetisme. Cong. Intern. Zool, 3 Sess., Leyden, 
 pp. 460-476. 
 
 Dixey, F. A. 1897. iMimctic Attraction. Trans. Ent. Soc. London, pp. 
 ,1' 7-33 1, pl- 7- 
 
 Mayer, A. G. 1897. On the Color and Color-Patterns of Moths and 
 Butterflies. Proc. Best. Soc. Nat. Hist., vol. 27, pp. 243-330, pis. 
 i-io. Also Bull. Mus. Comp. Zool., vol. 30, pp. 169-256, pis. i-io.* 
 
 Trimen, R. 1897. Mimicry in Insects. Proc. Ent. Soc. London, pp. 74- 
 97.* 
 
 Webster, F. M. 1897. Warning Colors, Protective Mimicry and Protec- 
 tive Coloration. 27tli. Ann. Rept. Ent. Soc. Ontario (1896), pp. 
 80-86, figs. 80-82. 
 
 Newbigin, M. I. 1898. Colour in Nature. 12 -(-344 pp. London. John 
 Murray.* 
 
 Poulton, E. B. 1898. Natural Selection the Cause of Mimetic Resem- 
 blance and Conmion Warning Colors. Journ. Linn. Soc. Zool., 
 vol. 26, pp. 558-612, pis. 40-44, figs. 1-7. 
 
 Judd, S. D. 1899. The Efficiency of Some Protective Adaptations in 
 Securing Insects from Birds. Amer. Nat., vol. 33, pp. 461-484. 
 
 Marshall, G. A. K., and Poulton, E. B. 1902. Five Years' Observations 
 and Experiments (1896-1901) on the Bionomics of South African 
 Insects, chiefly directed to the Investigation of Mimicry and 
 Warning Colours. Trans. Ent. Soc. London, pp. 287-584, pis. 
 9-^3- 
 
 Shelford, R. 1902. Observations on some Mimetic Insects and Spiders 
 from Borneo and Singapore. Proc. Zool. Soc. London, 1902, vol. 
 2, pp. 230-284, pis. 19-23. 
 
 Weismann, A. 1902. Vortrage iiber Descendenztheorie. 2 vols. 12 -f 
 456 pp., 95 figs. ; 6 + 462 pp., 3 pis., 36 figs. Jena. G. Fischer. 
 See pp. 103-133. 
 
 Piepers, M. C. 1903. Mimikry, Selektion und Darwinismus. 452 pp. 
 Leiden. E. J. Brill. 
 
 Poulton, E. B. 1903, Experiments in 1893, 1894 and 1896 upon the colour- 
 relation betvi^een lepidopterous larvae and their surroundings, and 
 especially the effect of lichen-covered bark upon Odontopera 
 bidentata, Gastropacha quercifolia, etc. Trans. Ent. Soc. London, 
 PP- 311-374, pis. 16-18. 
 
 Packard, A. S. 1904. The Origin of the ^Markings of Organisms (Poecilo- 
 genesis) due to the Physical rather than to the Biological Envi- 
 ronment ; with Criticisms of the Bates-Miiller Hypothesis. Proc. 
 Amer. Phil. Soc, vol. 43, pp. 393-450.* 
 
 ORIGIN OF ADAPTATIONS AND OF SPECIES 
 
 Darwin, C. 1859, 1869. The Origin of Species by means of Natural 
 Selection. 11 -j- 440 pp. London. New York. D. Appleton & 
 Co. 
 
452 ENTOMOLOGY 
 
 Spencer, H. 1866-67. The Principles of Biology. 2 vols. 16 + 1041 pp., 
 
 306 figs. New York. D. Appleton & Co. 
 Wallace, A. R. 1870. Contributions to the Theory of Natural Selection. 
 
 16-1-384 pp. London and New York. Macmillan & Co. 
 Weismann, A. 1880-81. Studies in the Theory of Descent. Trans, by 
 
 R. Meldola. 554 pp., 8 pis. London. 
 Cope, E. D. 1887. The Origin of the Fittest. 19 + 467 pp., 18 pis., 81 
 
 figs. New York. D. Appleton & Co. 
 Henslow, G. 1888. The Origin of Floral Structures through Insect and 
 
 other Agencies. 19 -|- 349 pp., 88 figs. New York. D. Appleton 
 
 & Co. 
 Wallace, A. R. 1889. Darwinism. 16 -{-494 pp., ^7 figs. London and 
 
 New York. Macmillan & Co. 
 Eimer, G. H. T. 1890. Organic Evolution as the Result of the Inheritance 
 
 of Acquired Characters according to the Laws of Organic Growth. 
 
 Trans, by J. T. Cunningham. 28 -|- 435 pp. London and New 
 
 York. Macmillan & Co. 
 Weismann, A. 1891, 1892. Essays upon Heredity and Kindred Biological 
 
 Problems. Ed. by E. B. Poulton, S. Schonland and A. E. Ship- 
 ley. Vol. I, 15 -(-471 pp.; vol. 2, 8-I-226 pp. Ed. 2. Oxford. 
 
 Clarendon Press. 
 Romanes, G. J. 1892, 1897, 1901. Darwin and After Darwin. Vol. i. 
 
 The Darwinian Theory, 14 4-460 pp., 125 figs.; vol. 2, Heredity 
 
 and Utility, 10 -|- 344 pp., 4 figs. ; vol. 3, Isolation and Physiological 
 
 Selection, 8-|-i8i pp. Chicago. Open Court Pub. Co. 
 Weismann, A. 1892, 1898. The Germ-Plasm. A Theory of Heredity. 
 
 Trans, by W. N. Parker and H. Ronnfeldt. 22 -|- 477 pp., 24 figs. 
 
 New York. C. Scribner's Sons. 
 Romanes, G. J. 1893. An Examination of Weismannism. 9 -|- 221 pp. 
 
 Chicago. Open Court Pub. Co. 
 Bateson, W. 1894. Materials for the Study of Variation treated with 
 
 especial Regard to Discontinuity in the Origin of Species. 16 -}- 
 
 598 pp., 209 figs. London and New York. Macmillan & Co. 
 Baldwin, J. M. 1895. Consciousness and Evolution. Science, vol. 2 (n. 
 
 s.), pp. 219-223. 
 Delage, Y. 1895. La structure du protoplasma et les theories sur I'here- 
 
 dite et les grands problemes de la biologie generale. 16 -f 878 pp. 
 
 Paris. C. Reinwald et Cie.* 
 Baldwin, J. M. 1896. Physical and Social Heredity. Amer. Nat., vol. 30, 
 
 pp. 422-428. 
 Baldwin, J. M. 1896. A New Factor in Evolution. Amer. Nat., vol. 30, 
 
 pp. 441-451- 536-553- 
 Baldwin, J. M. 1896. Heredity and Instinct. Science, vol. 3 (n. s.), pp. 
 
 438-441, 558-561. 
 Cope, E. D. 1896. The Primary Factors of Organic Evolution. 16 + 547 
 
 pp., 120 figs. Chicago. Open Court Pub. Co. 
 Morgan, C. Lloyd. 1896. On Modification and Variation. Science, vol. 4 
 
 (n. s.), pp. 733-740. 
 
LITERATURE 453 
 
 Morgan, C. Lloyd. 1896. ir;il)it and Instinct. 351 pp. London and New 
 
 York. v.. Arnold. 
 Osborn, H. F. 1896. Ontoscnic and Plixlogcnic Variation. Science, vol. 
 
 4 (n. s.), pp. 786-789, 
 Bailey, L. H. 1896, 1897. The Survival of the Unlike. 515 pp. New 
 
 York and London. The Macmillan Co. 
 Baldwin, J. M. 1897. Organic Selection. Science, vol. 5 (n. s.), pp. 
 
 634-6;.(i. 
 De Vries, H. 1901-3. l^ie Mutalionstheorie. 14 + 752 pp.. 12 pis., 159 
 
 figs. Leipzig. Veit & Co.* 
 Baldwin, J. M. 1902. Development and Evolution. 16 -{-395 pp. New 
 
 York and London. The Macmillan Co. 
 Weismann, A. 1902. Vortriige iiber Descendenztheorie. Bd. i, 12 -j- 456 
 
 pp., 95 figs.; bd. 2, 6 + 462 pp., 36 figs., 3 taf. Jena. G. Fischer. 
 Morgan, T. H. 1903. Evolution and Adaptation. 13 + 470 pp., 5 figs. 
 
 New York and London. The ALacmillan Co. 
 Vernon, H. M. 1903. Variation in Animals and Plants. 9 + 415 pp. 
 
 New York. Henry Holt & Co. 
 Kellogg, V. L., and Bell, R. G. 1904. Studies of Variation in Lisects. 
 
 Proc. Wash. Acad. Sc, vol. 6, pp. 203-332, figs. 1-81. 
 Metcalf, M. M. 1904. An Outline of the Theory of Organic Evolution. 
 
 22 + 204 pp., loi pis., 46 figs. New York and London. The 
 
 ■\Lacmillan Co.* 
 Weismann, A. 1904. The Evolution Theory. Trans, by J. A. Thomson 
 
 and ^I. R. Thomson. 2 vols. 16 + 821 pp., 131 figs. London. E. 
 
 Arnold. 
 De Vries, H. 1905. Species and Varieties : their Origin by Mutation. 
 
 Ed. by D. T. MacDougal. 18 + 847 pp. Chicago. Open Court 
 
 Pub. Co. 
 Gulick, J. T. 1905. Evolution, Racial and Habitudinal. 12+ 269 pp. 
 
 Carnegie Inst. Washington. 
 Reid, G. A. 1906. The Principles of Heredity. Ed. 2. 13 + 379 pp. 
 
 London. Chapman & Hall, Ltd. 
 
 INSECTS IN RELATION TO PLANTS 
 
 Darwin, C. 1877. The Eflfects of Cross and Self Fertilisation in the Vege- 
 talile Kingdom. 8 + 482 pp. New York. D. Appleton & Co. 
 
 Lubbock, J. 1882. On British Wild Flowers considered in Relation to 
 Insects. Ed. 4. 16+186 pp., 130 figs. London. Macmillan & 
 Co. 
 
 Mijller, H. 1883. The Fertilisation of Flowers. 12 + 669 PP-i 1S6 figs. 
 London. ^Macmillan & Co. 
 
 Darwin, C. 1884. The Various Contrivances by which Orchids are fer- 
 tilised by Insects. Ed. 2. 16 + 300 pp., 38 figs. New York. D. 
 Appleton & Co. 
 
 Darwin, C. 1884. Insectivorous Plants. 10 + 462 pp., 30 figs. New 
 York. D. Appleton & Co. 
 
454 ENTOMOLOGY 
 
 Cheshire, F. R. 1886. Bees and Bee-keeping. 2 vols. Vol. i, 7 + 336 
 pp., 71 figs., 8 pis.; vol. 2, 652 pp.. 127 figs., I pi. London. L. 
 Upcott Gill. 
 
 Forbes, S. A. 1886. Studies on the Contagious Diseases of Insects. Bull. 
 111. St. Lab. Nat. Hist., vol. 2, pp. 257-321, i pi. 
 
 Thaxter, R. 1888. The Entomophthorese of the United States. Mem. 
 Bost. Soc. Nat. Hist., vol. 4. pp. 133-201, pis. 14-21. 
 
 Robertson, C. 1889-99. Flowers and Insects. I-XIX. Bot. Gaz., vols. 
 14-22, 25, 28. 
 
 Seitz, A. 1890, 1893, 1894. Allgemeine Biologic der Schmetterlinge. 
 Zool. Jahrb., Abth. Syst., etc., bd. 5, pp. 281-343; bd. 7, pp. 131- 
 186, 823-851.* 
 
 Eckstein, K. 1891. Pflanzengallen und Gallentiere 88 pp., 4 taf. Leip- 
 zig. R. Freese. 
 
 Robertson, C. 1891-96. Flowers and Insects. Trans. Acad. Sc, St. 
 Louis, vols. 5-7. 
 
 Cooke, M. C. 1892. Vegetable Wasps and Plant Worms. 5 -)- 364 pp., 4 
 pis., 51 figs. London. 
 
 Riley, C. V. 1892. Some Interrelations of Plants and Insects. Proc. 
 Biol. Soc. Wash., vol. 7, pp. 81-104, figs. 1-15. 
 
 Riley, C. V. 1892. The Yucca Moth and Yucca Pollination. Third Ann. 
 Rept. Mo. Bot. Garden, pp. 99-158, pis. 34-43. 
 
 Moller, A. 1893. Die Pilzgarten einiger siidamericanischer Ameisen. 
 Bot. Mitt, aus den Tropen, heft 6. 7-I-127 pp., 7 taf., 4 figs. 
 Jena. G. Fischer. 
 
 Trelease, W. 1893. Further Studies of Yuccas and their Pollination. 
 Fourth Ann. Rept. Mo. Bot. Garden, pp. 181-226, pis. 1-23. 
 
 Adler, H., and Straton, C, R. 1894. Alternating Generations. A Biolo- 
 gical Study of Oak Galls and Gall F"lies. 40 -j- 198 pp., 3 pis. 
 Oxford. Clarendon Press."** . 
 
 Webster, F. M. 1894. Vegetal Parasitism among Insects. Journ. Colum- 
 bus Hort. Soc, pp. 1-19, pis. 3-5, figs. I, 2. 
 
 Heim, F. L. 1898. The Biologic Relations between Plants and Ants. 
 Ann. Rept. Smiths. Inst. 1896, pp. 411-455, pis. 17-22. Trans. 
 from Compt. rend. 24me Sess. Ass. fr. I'av. Sc. 1895, pp. 31-75. 
 
 Schimper, A. F. W. 1898. Pflanzen-Geographie auf physiologischer 
 Grundlage. 18 -|- 876 pp., 502 figs., 5 plates, 4 maps. Jena. G. 
 Fischer. (See pp. 147-170.)* Trans: 1903. W. R. Fisher. 
 Plant-Geography upon a Physiological Basis. 30-4-839 pp., 502 
 figs., 4 maps. Oxford, Clarendon Press. (See pp. 126-156.)* 
 
 Benton, F. 1899. The Honey Bee: A Manual of Instruction in Apicul- 
 ture. Bull. LT. S. Dept. Agric, Div. Ent., no. i (n. s.), pp. 1-118, 
 pis. i-ii, figs. 1-76.* 
 
 Needham, J. G. 1900. The Fruiting of the Blue Flag (Iris versicolor L.). 
 Amer. Nat., vol. 34, pp. 361-386, pi. i, figs. 1-4. 
 
 Gibson, W. H. 1901. Blossom Hosts and Insect Guests. 19 + 197 pp., 
 figs. New York. Newson & Co. 
 
LITERATURE 
 
 455 
 
 Connold, E. T. 1902. British Vegetable Galls. 12 + 312 pp., 130 pis., 10 
 
 figs. New York. E. P. Button & Co. 
 Cook, M. T. 1902-04. Galls and Insects Producing Them. Pts. I-IX. 
 
 Ohio Nat., vols. 2-4, pis. Same, Bull. Ohio St. Univ., ser. 6, no. 
 
 15; ser. 7. no. 20; ser. 8, no. 13. 
 Needham, J. G. 1903. Button-Bush Insects. Psyche, vol. 10, pp. 22-31. 
 Cowan, T. W. 1904. The Honey Bee: its Natural History, Anatomy and 
 
 Physiology. ]*2d. 2. 12 + 220 pp.. Jt, figs. London. Iloulston & 
 
 Sons.* 
 Rossig, H. 1904. Von welchen Organen der Gallwespenlarven geht der 
 
 Reiz zur Bildung der Pflanzengalle aus? Zool. Jahrb., Abth. 
 
 Syst., etc., bd. 20, pp. 19-90, taf. 3-6.* 
 
 INSECTS IN RELATION TO OTHER ANIMALS 
 
 Aughey, S. 1878. Notes on the Nature of the Food of the Birds of 
 
 Nebraska. First Rept. U. S. Ent. Cpmni., Appendix, 2, pp. 13-62. 
 Forbes, S. A. 1878. The Food of Illinois Fishes. Bull. 111. St. Lab. Nat. 
 
 Hist., vol. I, no. 2, pp. 71-89. 
 Forbes, S. A. 1880. The Food of Birds. Trans. 111. St. Hort. Soc, vol. 
 
 13 (1879), pp. 120-172. 
 Forbes, S. A. 1880. On Some Interactions of Organisms. Bull. III. St. 
 
 Lab. Nat. Hist., vol. i, no. 3, pp. 3-17. 
 Forbes, S. A. ijBBo. The Food of Fishes, Bull. III. St. Lab. Nat. Hist., 
 
 vol. I, no. 3, pp. 18-65. 
 Forbes, S. A. 1880. On the Food of Young Fishes. Bull. 111. St. Lab. 
 
 Nat. Hist., vol. i, no. 3, pp. 66-79. 
 Forbes, S. A. 1880. The Food of Birds. Bull. 111. St. Lab. Nat. Hist., 
 
 vol. I, no. 3, pp. 80-148. 
 Forbes, S. A. 1883. The Regulative Action of Birds upon Insect Oscilla- 
 tions. Bull. 111. St. Lab. Nat. Hist., vol. i, no. 6, pp. 2i-2,^- 
 Forbes, S. A. 1883. The Food of the Smaller Fresh-Water Fishes. Bull. 
 
 111. St. Lab. Nat. Hist., vol. i, no. 6. pp. 65-94. 
 Forbes, S. A. 1883. The First Food of the Common White-Fish. Bull. 
 
 III. St. Lab. Nat. Hist., vol. i, no. 6, pp. 95-109. 
 Dimmock, G. 1886. Belostomidse and some other Fish-destroying Bugs. 
 
 Ann. Rept. Fish Game Comm. Mass., pp. 67-74, i fig.* 
 Forbes, S. A. 1888. Studies on the Food of Fresh-Water Fishes. Bull. 
 
 111. St. Lab. Nat. Hist., vol. 2. pp. 433-473- 
 Forbes, S. A. 1888. On the Food Relations of Fresh-Water Fishes : a 
 
 Summary and Discussion. Bull. 111. St. Lab. Nat. Hist., vol. 2, 
 
 PP- 475-538. 
 Wilcox, E. V. 1892. The Food of the Robin. Bull. Ohio Agr. Exp. Sta., 
 
 no. 43, pp. 115-131- 
 Beal, F. E. L. 1897. Some Common Birds in their Relation to Agricul- 
 ture. Farmer's Bull. U. S. Dept. Agric, no. 54, pp. 1-40, figs. 
 
 1-22 
 
45^ ENTOMOLOGY 
 
 Kirkland, A. H. 1897. The Habits, Food and Economic Value of the 
 
 American Toad. Bull. Hatch Exp. Sta. Mass. Agr. Coll., no. 46, 
 
 pp. 3-30, pl. 2. 
 Judd, S. D. 1899. The Efficiency of Some Protective Adaptations in 
 
 Securing Insects from Birds. Amer. Nat., vol. 33, pp. 461-484. 
 Palmer, T. S. 1900. A Review of Economic Ornithology. Yearbook 
 
 U. S. Dept. Agric. 1899, pp. 259-292. 
 Judd, S. D. 1901. The Food of Nestling Birds. Yearbook U. S. Dept. 
 
 Agric. 1900, pp. 411-436, pis. 49-53. figs. 48-56. 
 Forbes, S. A. 1903. Studies of the Food of Birds, Insects and Fishes. 
 
 Second Ed. Bull. 111. St. Lab. Nat. Hist., vol. i, no. 3. 
 Weed, C. M., and Dearborn, N. 1903. Birds in their Relations to Man. 
 
 8-I-380 pp., figs. Philadelphia and London. J. B. Lippincott 
 
 Co.* 
 
 INSECTS IN RELATION TO DISEASES 
 
 Blandford, W. F. H. 1896. Jhe Tsetse fly-disease. Nature, vol. 53, pp. 
 566-568, figs. I, 2. 
 
 Sternberg, G. M. 1897. The Alalarial Parasite and other Pathogenic 
 Protozoa. Pop. Sc. Mon., vol. 50, pp. 628-641, figs. 1-3. 
 
 Kanthack, A. A., Durham, H. E., and Blandford, W. F. H. 1898. On 
 Nagana, or Tsetse fly disease. Proc. Roy. Soc. Lond., vol. 64, 
 pp. 1 00-118. 
 
 Finlay, C. J. 1899. Mosquitoes considered as Transmitters of Yellow 
 Fever and Malaria. Psyche, vol. 8, pp. 379-384. 
 
 Nuttall, G. H. F. 1899. On the role of Insects, Arachnids and Myriapods, 
 as carriers in the spread of Bacterial and Parasitic Diseases of 
 Man and Animals. A Critical and Historical Study. Johns 
 Hopk. Hosp. Rept, vol. 8, no. i, 154 pp., 3 pis. 
 
 Ross, R. 1899. Life-History of the Parasites of Malaria. Nature, vol. 
 60, pp. 322-324. 
 
 Christy, C. 1900. Mosquitos and Malaria : a summary of knowledge on 
 the subject up to date; with an account of the natural history of 
 mosquitos. 9 -|- 80 pp., 5 pis. London. 
 
 Howard, L. 0. 1900. Notes on the Mosquitoes of the United States: giv- 
 ing some account of their structure and biology, with remarks on 
 remedies. Bull. U. S. Dept. Agric, Div. Ent., no. 25 (n. s.), 70 
 pp., 22 figs. 
 
 Howard, L. 0. 1900. A contribution to the study of the insect fauna of 
 human excrement (with especial reference to the spread of typhoid 
 fever by flies). Proc. Wash. Acad. Sc, vol. 2, pp. 541-604, pis. 
 30, 31, figs. 17-38- 
 
 Ross, R. 1900. Malaria and Mosquitoes. Nature, vol. 61, pp. 522-527. 
 
 Ross, R., and Fielding-Ould, R. 1900. Diagrams illustrating the Life- 
 history of the Parasites of Malaria. Quart. Journ. Micr. Sc, vol. 
 43 (n. s.), pp. 571-579, pis. 30, 31- 
 
 Grassi, B. 1901. Die Malaria-Studien eines Zoologen. 8 -{-250 pp., 8 
 taf. Jena. G. Fischer. 
 
LITERATURE 457 
 
 Howard, L. 0. 1901. AFosquitocs; how tliey live; how they carry disease; 
 how they are chissitied ; how they may be destroyed. 15 -|- 241 
 pp., 50 tigs., I pi. New York. McChire, Philhps & Co. 
 
 Sternberg, G. M. 1901. Tlie Transmission of Yellow l-Y'ver ])y Mos- 
 quitoes. Pop. So. IMon., vol. 59, pp. 225-241. 
 
 Howard, L. 0. 1902. Insects as Carriers and Spreaders of Disease. Year- 
 hook V. S. Dept. Agric. 1901, pp. 177-192, figs. 5-20. 
 
 Braun, M. 1903. Die thierischen Parasiten des Menschen. Rev. Ed. 
 12 + 360 pp., 272 figs. Wiirzburg. 
 
 Sternberg, G. M. 1903. Infection and Immunity; with special Reference 
 to the Prevention of Infectious Diseases. 5 + 293 pp., 12 figs. 
 New York and London. G. P. Putnam's Sons. 
 
 Blanchard, R. 1905. Les Moustiques, histoire naturelle et medicale. 
 673 pp., 316 figs. Paris. De Rudeval. 
 
 INTERRELATIONS OF INSECTS 
 
 Van Beneden, P. J. 1876. Animal Parasites and Messmates. 28 + 274 
 
 pp.. 83 figs. New York. D. Appleton & Co. 
 McCook, H. C. 1877. Mound-making Ants of the Alleghenies, their 
 
 Architecture and Habits. Trans. Amer. Ent. Soc, vol. 6, pp. 253- 
 
 296, figs. 1-13. 
 Fabre, J. H. 1879-1905. Souvenirs entomologiques. fetudes sur I'instinct 
 
 et les moeurs des insectes. 9 Series. Paris. C. Delagrave. 
 
 Trans, of Sen I: 1901. Fabre, J. H. Insect Life. 12 + 320 pp., 
 
 16 pis. London and New York. The Macmillan Co. 
 Forbes, S. A. 1880. Notes on Insectivorous Coleoptera. Bull. 111. St. 
 
 Lab. Nat. Hist., vol. i, no. 3, pp. 153-160. Second Ed., 1903. 
 McCook, H. C. 1880. The Natural History of the Agricultural Ant of 
 
 Texas. 310 pp.. 24 pis. Philadelphia. J. B. Lippincott & Co. 
 Webster, F. M. 1880. Notes upon the Food of Predaceous Beetles. Bull. 
 
 111. St. Lab. Nat. Hist., vol. i. no. 3. pp. 149-152. Second Ed., 
 
 1903. 
 McCook, H. C. 1881. Note on a new Northern Cutting Ant. Atta septen- 
 
 trionalis. Proc. Acad. Nat. Sc. Phila. 1880, pp. 359-363, i fig. 
 McCook, H. C. 1881. The Shining Slavemaker. Notes on the Architec- 
 ture and Habits of the American Slave-making Ant. Polyergus 
 
 lucidus. Proc. Acad. Nat. Sc. Phila. 1880, pp. 376-384. pi. 19. 
 Lubbock, J. 1882, 1901, 1904. Ants, Bees and Wasps. 19 -|- 448 pp., 31 
 
 figs., 5 pis. New York. D. Appleton & Co. 
 McCook, H. C. 1882. The Honey Ants of the Garden of the Gods, and 
 
 the Occident Ants of the American Plains. 188 pp., 13 pis. 
 
 Philadelphia. J. B. Lippincott & Co. 
 Forbes, S. A. 1883. The Food Relations of the Carabidas and Coccinel- 
 
 lidse. Bull. 111. St. Lab. Nat. Hist., vol. i, no. 6, pp. 33-64. 
 Cheshire, F. R. 1886. Bees and Bee-keeping. 2 vols. Vol. 1,74- 336 
 
 pp., 8 pis., 71 figs. ; vol. 2, 652 pp., 127 figs., I pi. London. L. 
 
 Upcott Gill. 
 
45° ENTOMOLOGY 
 
 Seitz, A. 1890, 1893, 1894. AUgemeine Biologic der Schmetterlinge. 
 
 Zool. Jahrb., Abth. Svst., etc., bd. 5, pp. 281-343; bd. 7, pp. 131- 
 
 186, 823-851.* 
 Verhoeff, C. 1892. Beitrage zur Biologic der Hymenoptera. Zool. Jahrb., 
 
 Abth. Syst., etc., bd. 6, pp. 680-754, taf. 30, 31. 
 Wasmann, E. 1894. Kritisches Verzeichnis der myrmekophilen und ter- 
 
 mitophilen Arthropoden. 231 pp. Berlin. F. L. Dames. 
 Grassi, B., and Sandias, A. 1896-97. The Constitution and Development 
 
 of the Society of Termites, etc. Trans, by W. F. H. Blandford. 
 
 Quart. Journ. Micr. Sc, vol. 39, pp. 245-322, pis. 16-20; vol. 40, 
 
 PP- 1-75- 
 Janet, C. 1896. Les Fourmis. Bull. Soc. zool. France, vol. 21, pp. 60-93. 
 
 Sep., 37 pp., Paris. 
 Howard, L. 0. 1897. A Study in Insect Parasitism. Bull. U. S. Dept. 
 
 Agric, Div. Ent., tech. ser. no. 5, pp. 1-57, figs. 1-24. 
 Peckham, G. W., and E. G. 1898. On the Instincts and Habits of the 
 
 Solitary Wasps. Bull. Wis. Geol. Nat. Hist. Surv., no. 2, sc. ser. 
 
 no. I, 4 + 245 pp., 14 pis. 
 Wasmann, E. 1898. Die Gaste der Ameisen und Termiten. lUustr. ' 
 
 Zeits. Ent., bd. 3, i taf. 
 Benton, F. 1899. The Honey Bee : A Manual of Instruction in Apicul- 
 ture. Bull. U. S. Dept. Agric, Div. Ent., no. i (n. s.), pp. 1-118, 
 
 pis. i-ii, figs. 1-76.* 
 Fielde, A. M. 1901. A Study of an Ant. Proc. Acad. Nat. Sc. Phila., 
 
 vol. 52, pp. 425-449- 
 Fielde, A. M. 1901. Further Study of an Ant. Proc. Acad. Nat. Sc. 
 
 Phila., vol. 53, pp. 521-544- 
 Wheeler, W. M. igoi. The Compound and jNIixed Nests of American 
 
 Ants. Amer. Nat., vol. 35, pp. 431, 513, 701, 791, figs. 1-20. 
 Enteman, M. M. 1902. Some Observations on the Behavior of the Social 
 
 Wasps. Pop. Sc. Mon., vol. 61, pp. 339-351. 
 Fielde, A. M. 1902. Notes on an Ant. Proc. Acad. Nat. Sc. Phila., vol. 
 
 54, pp. 599-625. 
 Dickel, F. 1903. Die Ursachen der geschlechtlichen Diflferenzirung im 
 
 Bienenstaat. Archiv ges. Phys., bd. 95, pp. 66-106, fig. i. 
 Fielde, A. M. 1903. Supplementary Notes on an Ant. Proc. Acad. Nat. 
 
 Sc. Phila., vol. 55, pp. 491-495- 
 Heath, H. 1903. The Habits of California Termites. Biol. Bull., vol. 4, 
 
 pp. 47-63, figs. 1-3. 
 Janet, C. 1903. Observations sur les guepes. 85 pp., 30 figs. Paris. 
 
 C. Naud. 
 Melander, A. L., and Brues, C. T. 1903. Guests and Parasites of the 
 
 Burrowing Bee Halictus. Biol. Bull., vol. 5, pp. 1-27, figs. 1-7. 
 Fielde, A. M. 1904. Power of Recognition among Ants. Biol. Bull., vol. 
 
 7, pp. 227-250, 4 figs. 
 Fielde, A. M., and Parker, G. H. 1904. The Reactions of Ants to Material 
 
 Vibrations. Proc. Acad. Nat. Sc. Phila., vol. 56, pp. 642-650.* 
 
LITERATURE 459 
 
 Wheeler, W. M. 1904. A New Type of Social Parasitism among Ants. 
 Bull. Anier. JNIus. Nat. Hist., vol. jo, pp. 347-375- 
 
 INSECT BEHAVIOR 
 
 Pouchet, G. 1872. De I'influence de la lumiere sur les larves de dip- 
 
 leres privees d'organes exterieurs de la vision. Rev. Mag. Zool., 
 
 scr. 2, t. 23, pp. 110-117, etc., pis. 12-16. 
 Fabre, J. H. 1879-1905. Souvenirs entomologiques. fitudes sur I'instinci 
 
 et les moeurs des insectes. 9 Series. Paris. C. Delagrave. 
 
 Trans, of Ser. I: 1901. Fabre, J. H. Insect Life. 12 -(-320 pp., 
 
 16 pis. London and New York. The Macmillan Co. 
 Lubbock, J. 1882, 1884. Ants, Bees and Wasps. 19 + 448 pp., 31 ligs., 5 
 
 pis. New York. D. Appleton & Co. 
 Graber, V. 1884. Grundlinien zur Erforschung des Helligkeits- und Far- 
 
 bensinnes der Tiere. 8 -|- 322 pp. Prag und Leipzig. 
 Romanes, G. J. 1884. Animal Intelligence. 14 -|- 520 pp. New York. 
 
 D. Appleton & Co. 
 Lubbock, J. 1888. On the Senses, Instincts and Intelligence of Animals, 
 
 with Special Reference to Insects. 294-292 pp., 118 figs. New 
 
 York. D. Appleton & Co. 
 Plateau, F. 1889. Recherches experimentales sur la Vision chez les Ar- 
 
 thropodes. Mem. cour. Acad. roy. Belgique, t. 43, pp. 1-91. 
 Eimer, G. H. T. 1890. Organic Evolution as the Result of the Inheritance 
 
 of Accjuired Characters according to the Laws of Organic Growth. 
 
 28 -\- 435 pp. Trans, by J. T. Cunningham. London and New 
 
 York. Macmillan & Co. 
 Loeb, J. 1890. Der Heliotropismus der Thiere und seine Uebereinstim- 
 
 mung mit dem Heliotropismus der Pflanzen. 118 pp. Wiirzburg. 
 Seitz, A. 1890. Allgemeine Biologic der Schmetterlinge. Zool. Jahrb., 
 
 Abth. Syst., bd. 5, pp. 281-343. 
 Exner, S. 1891. Die Physiologic der facettirten Augen von Krebsen und 
 
 Insecten. 8 + 206 pp., 8 taf., 23 figs. Leipzig und Wien. 
 Loeb, J. 1 891. Ueber Geotropismus hei Thieren. Arch. ges. Phys., bd. 
 
 49, pp. 175-189, figs. 
 Morgan, C. Lloyd. 1891. Animal Life and Intelligence. 13 -|- 512 pp., 40 
 
 figs. Boston. Ginn & Co. 
 James, W. 1893. The Principles of Psychology. 2 vols. 18 + 1393 pp., 
 
 94 figs. New York. Henry Holt & Co. 
 Loeb, J. 1893. Ueber kunstliche Umwandlung positiv heliotropischer 
 
 Thiere in negativ heliotropische und umgekehrt. Arch. ges. Phys., 
 
 bd. 54, pp. 81-107. 
 Baldwin, J. M. 1896. Heredity and Instinct. Science, vol. 3 (n. s.), pp. 
 
 438-441, 558-561. 
 Morgan, C. Lloyd. 1896. Habit and Instinct. 351 pp. London and New 
 
 York. E. Arnold. 
 Davenport, C. B. 1897, 1899. Experimental [Morphology. 2 Pts. 32-)- 
 
 508 pp., 140 figs. New York and London. The Macmillan Co. 
 
460 ENTOMOLOGY 
 
 Loeb, J. 1897. Zur Theorie der physiologischen Licht- mid Schwerkraft- 
 
 wirkungcn. Arch. ges. Phys.. l)d. 64. pp. 439-466. 
 Bethe, A. i8g8. Diirfen wir den Ameisen und Bienen psychische Quali- 
 
 taten zuschreiben? Archiv ges. Phvs., bd. 70, pp. 15-100, taf. i, 2, 
 
 5 figs. 
 Peckham, G. W., and E. G. 1898. On the Instincts and Habits of the 
 
 Solitary Wasps. Bull. Wis. Geol. Nat. Hist. Surv., no. 2, sc. 
 
 ser. no. 1.4 + 245 pp., 14 pis. 
 Verworn, M. 1899. General Physiolog>'. An Outline of the Science of 
 
 Life. Trans, by F. S. Lee. 16 + 615 pp., 285 figs. London and 
 
 New York. IMacmillan & Co. 
 Wasmann, E. 1899. Die psj'chischen Fahigkeiten der Ameisen. Zoolog- 
 
 ica, heft 26, 6 + 132 pp., 3 taf. Stuttgart. E. Nagele. 
 Wheeler, W. M. 1899. Anemotropism and Other Tropisms in Insects. 
 
 Arch. Entw. Org., bd. 8, pp. 373-381. 
 Whitman, C. 0. 1899. Animal Behavior. Biol. Lect., Marine Biol. Lab., 
 
 Wood's Holl, Mass., 1898, pp. 285-338. Boston. Ginn & Co. 
 Loeb, J. 1900. Comparative Physiology of the Brain and Comparative 
 
 Psychology. 309 pp., 39 figs. New York, G. P. Putnam's Sons. 
 
 London, J. Murray.* 
 Morgan, C. Lloyd. 1900. Animal Behaviour. 8 + 344 pp., 26 figs. Lon- 
 don. E. Arnold. 
 Radl, E. 1901. Ueber den Phototropismus einiger Arthropoden. Biol. 
 
 Centralb., bd. 21, pp. 75-86. 
 Radl, E. 1901. L'^ntersuchungen iiber die Lichtreactionen der Arthro- 
 poden. Arch. ges. Phys., bd. 87, pp. 418-466. 
 Enteman, M. M. 1902. Some Observations on the Behavior of the Social 
 
 Wasps. Pop. Sc. Mon., vol. 61, pp. 339-351. 
 Weismann, A. 1902. Vortrage iiber Descendenztheorie. 2 vols. 12 -f 
 
 456 pp., 95 figs.; 6 + 462 pp., 3 pis., 36 figs. Jena. G. Fischer. 
 
 See pp. 159-181. 
 Kathariner, L. 1903. Versuche iiber die Art der Orientierung bei der 
 
 Honigbienc. Biol. Centralb., bd. 23, pp. 646-660, i fig. 
 Kellogg, V. L. 1903. Some Insect Reflexes. Science, vol. 18 (n. s.), pp. 
 
 693-696. 
 Morgan, T. H. 1903. Evolution and Adaptation. 134-470 pp., 5 figs. 
 
 New York and London. The ■Nlacmillan Co. 
 Parker, G. H. 1903. The Phototropism of the ]\Iourning-cloak Butterfly, 
 
 Vanessa antiopa Linn. Mark Anniv. Vol., pp. 453-469, pi. 33.* 
 Fielde, A. M., and Parker, G. H. 1904. The Reactions of Ants to Material 
 
 Vibrations. Proc. Acad. Nat. Sc. Phila., vol. 56, pp. 642-650.* 
 Forel, A. 1904. The Psychical Faculties of Ants and some other Insects. 
 
 Ann. Rept. Smiths. Inst. 1903, pp. 587-599. Trans, from Proc. 
 
 Fifth Intern. Zool. Congr. Berlin, 1901, pp. 141-169. 
 Jennings, H. S. 1904. Contributions to the Study of the Behavior of 
 
 Lower Organisms. 256 pp., 81 figs. Carnegie Inst. Washington.* 
 
LITERATURE 46 I 
 
 Carpenter, F. W. 1905. Tlic Reactions of the Pomace Fly (Drosophila 
 
 ampelophila Loew) to Light, Gravity, and ^Mechanical Stinnila- 
 
 tion. Anier. Nat., vol. 39, pp. 157-171.* 
 Hartman, C. 1905. Ohservations on the Habits of some Solitary Wasps 
 
 of Texas. I'ull. Univ. "i'c.xas, no. 65, sc. ser. no. 7, pp. 1-73, 4 pis. 
 Holmes, S. J. 1905. The Reactions of Ranatra to Light. Jonrn. Comp. 
 
 Neur, Psych., vol. 15, pp. 305-349, figs. 1-6. 
 Loeb, J. 1905. Studies in General Physiology. 2 vols. 24 -f- 782 pp., 162 
 
 figs. L^niv. Chicago Decenn. Pnbl., ser. 2, vol. 15, pts. i, 2. 
 Wasmann, E. 1905. Comparative Studies in the Psychology of Ants and 
 
 of Higher Animals. 10 + 200 pp. St. Louis and Freiburg, B. 
 
 Herder; London and Edinburgh, Sands & Co.* 
 
 GEOGRAPFHCAL DISTRIBUTION 
 
 Darwin, C. 1859, 1869. On the Origin of Species by means of Natural 
 Selection. Pp. 1 1 -\- 440. New York. D. Appleton & Co. See 
 pp. 302-357. 
 
 LeConte, J. L. 1859. The Coleoptera of Kansas and Eastern New Mex- 
 ico. Smithson. Contrib., vol. 11, 6 + 58 pp., 2 pis., map. 
 
 Bates, H. W. 1864. The Naturalist on the River Amazons. 12 -|- 466 
 pp., figs. London. J. Murray. 
 
 Wallace, A. R. 1865. On the Phenomena of Variation and Geographical 
 Distribution as illustrated by the Papilionidas of the Malayan Re- 
 gion. Trans. Linn. Soc. ZooL, vol. 25, pp. 1-71, pis. 1-8. 
 
 Wallace, A. R. 1869. The Malay Archipelago. 12 -{-638 pp., 51 figs., 10 
 maps. New York. Harper & Bros. 
 
 Murray, A. 1873. On the Geographical Relations of the Chief Coleop- 
 terous Faunas. Journ. Linn. Soc. ZooL, vol. 11, pp. 1-89. 
 
 Belt, T. 1874, 1888. The Naturalist in Nicaragua. 32 + 403 pp., figs. 
 London. J. Murray; E. Bumpus. 
 
 Wallace, A. R. 1876. The Geographical Distribution of Animals. 2 vols. 
 Vol. I, 214-503 pp., 13 pis., 5 maps; vol. 2, 8 -(- 607 pp., 7 pis,, 2 
 maps. New York. Harper & Bros. 
 
 Semper, K. 1881. Animal Life as affected by the Natural Conditions of 
 Existence. 16 -f 472 pp., 106 figs., 2 maps. New York. D. Apple- 
 ton & Co. 
 
 Wallace, A. R. 1881. Island Life, or the Phenomena and Causes of Insu- 
 lar Faunas and Floras, etc. 16 -|- 522 pp., 26 maps and figs. New 
 York. Harper & Bros. 
 
 Gill, T. 1884. The Principles of Zoogeography. Proc. Biol. Soc. Wash., 
 vol. 2, pp. 1-39. 
 
 Forbes, H. 0. 1885. A Naturalist's Wanderings in the Eastern Archi- 
 pelago. 19 + 536 pp., figs., pis., maps. New York. Harper & 
 Bros. 
 
462 ENTOMOLOGY 
 
 Schwarz, E. A. 1888. The Insect Fauna of Semitropical Florida, with 
 
 Special Regard to the Coleoptera. Ent. Amer., vol. 4, pp. 165- 
 
 175- 
 Merriam, C. H. 1890. Results of a Biological Survey of the San Fran- 
 cisco Mountain Region and Desert of the Little Colorado, Arizona. 
 
 U. S. Dept. Agric, Div. Ornith. Mamm., N. A. Fauna, no. 3, 
 
 6 + 136 pp., 13 pis., 5 maps, 2 figs. 
 Schwarz, E. A. 1890. On the Coleoptera common to North America and 
 
 other Countries. Proc. Ent. Soc. Wash., vol. i, pp. 182-194. 
 Seitz, A. 1890, 1893, 1894. Allgemeine Biologic der Schmetterlinge. 
 
 Zool. Jahrb., Abth. Syst., etc., bd. 5, pp. 281-343; bd. 7, pp. 131- 
 
 186, 823-851.* 
 Trouessart, E. L. 1890. La Geographie Zoologique. 11 -{-338 pp., 63 
 
 figs., 2 maps. Paris. 
 Wallace, A. R. 1890. A. Narrative of Travels on the Amazon and Rio 
 
 Negro, etc. Ed. 3. 14 -|- ^63 pp., 16 pis. London, New York and 
 
 Melbourne. Ward, Lock & Co. 
 Packard, A. S. 1891. The Labrador Coast. 513 pp., figs. New York. 
 
 N. D. C. Hodges. 
 Bates, H, W. 1892. The Naturalist on the River Amazons. Reprint. 
 
 89 + 395 PP-. figs. London. J. ]Murray. 
 Distant, W. L. 1892. A Naturalist in the Transvaal. 16 -\- 277 pp., pis., 
 
 figs. London. R. H. Porter. 
 Hudson, W. H. 1892. The Naturalist in La Plata. 8 -(-388 pp., figs. 
 
 London. Chapman & Hall. 
 Webster, F. M. 1892. Modern Geographical Distribution of Insects in 
 
 Indiana. Proc. Ind. Acad. Sc, pp. 81-88, map. 
 Merriam, C. H. 1893. The Geographic Distribution of Life in North 
 
 America, with special Reference to the Mammalia. Smithson. 
 
 Rept. 1891, pp. 365-415. From Proc. Biol. Soc. Wash., vol. 7, 
 
 pp. 1-64. 
 Elwes, H. J. 1894. The Geographical Distribution of Butterflies. Trans. 
 
 Ent. Soc. London, Proc, pp.. 52-84. 
 Hamilton, J. 1894. Catalogue of the Coleoptera common to North Amer- 
 ica, Northern Asia and Europe, with Distribution and Bibliogra- 
 phy. Trans. Amer. Ent. Soc, vol. 21, pp. 345-416 -|- 19. 
 Merriam, C. H. 1894. Laws of Temperature Control of the Geographic 
 
 Distribution of Terrestrial Animals and Plants. Nat. Geogr. 
 
 Mag., vol. 6, pp. 229-238, 3 maps. 
 Scudder, S. H. 1894. The Effect of Glaciation and of the Glacial Period 
 
 on the Present Fauna of North America. Amer. Journ. Sc, ser. 
 
 3, vol. 48, pp. 179-187- 
 Webster, F. M. 1894. Some Insect Immigrants in Ohio. Bull. Ohio Agr. 
 
 Exp. Sta., ser. 2, vol. 6. no. 51 (1893), pp. 1 18-129, figs. 17, 18. 
 Whymper, E. 1894. Travels amongst the Great Andes of the Equator. 
 
 24 -f 456 pp., 20 pis., 4 maps, 118 figs. New York. C. Scribner's 
 
 Sons. 1891. Suppl. Appendix. 22 -|- 147 pp., figs. London. J. 
 
 Murray. 
 
LITERATURE 463 
 
 Beddard, F. E. 1895. A Text-book of Zoogeograpliy. 84-246 pp., 5 
 maps. Cambridge, Eng. University Press. 
 
 Howard, L. 0. 1895. Notes on the Geographical Distribution within the 
 United States of certain Insects injuring CuUivated Crops. Proc. 
 Ent. Soc. Wash., vol. 3, pp. 219-226. 
 
 Webster, F. M. 1895. Notes on the Distrilxition of some Injurious In- 
 sects. Proc. Ent. Soc. Wash., vol. 3, pp. 284-290. 
 
 Webster, F. M. 1896. The Probable Origin and Difltusion of Blissus 
 leucopterus and Murgantia histrionica. Journ. Cine. Soc. Nat. 
 Hist., vol. 18, pp. 141-155. fig- I. Pl- 5- 
 
 Carpenter, G. H. 1897. The Geographical Distribution of Dragon-ilies. 
 Proc. Roy. Dublin Soc, vol. 8, pp. 439-468, pi. 17. 
 
 Heilprin, A. 1897. The Geographical and Geological Distribution of Ani- 
 mals. 12-)- 435 pp., map. New York. D. Appleton & Co. 
 
 Saville-Kent, W. 1897. The Naturalist in Australia. 15 + 302 pp., 50 
 pis., 104 figs. London. Chapman «& Hall. 
 
 Webster, F. M. 1897. Biological Effects of Civilization on the Insect 
 Fauna of Ohio. Fifth Ann. Kept. Ohio St. Acad. Sc, pp. 32-46, 
 2 figs. 
 
 Merriam, C. H. 1898. Life Zones and Crop Zones of the United States. 
 Bull. U. S. Dept. Agric, Div. Biol. Surv., no. 10, pp. 1-79, map. 
 
 Webster, F. M. 1898. The Chinch Bug. Bull. U. S. Dept. Agric, Div. 
 Ent., no. 15 (n. s.), 82 pp., 19 figs. (See pp. 66-82.) 
 
 Semon, R. 1899. In the Australian Bush and on the Coast of the Coral 
 Sea, etc. 15 + 55^ pp., 4 maps, 86 figs. London and New York. 
 Macmillan & Co. 
 
 Tower, W. L. 1900. On the Origin and Distribution of Leptinotarsa 
 decem-lineata Say, and the Part that some of the Climatic Fac- 
 tors have played in its Dissemination. Proc. Amer. Ass. Adv. 
 Sc, vol. 49, pp. 225-227. 
 
 Adams, C. C. 1902. Postglacial Origin and Migrations of the Life of the 
 Northeastern United States. Journ. Geogr., vol. i, pp. 303-310, 
 352-357, map. 
 
 Adams, C. C. 1902. Southeastern United States as a Center of Geograph- 
 ical Distribution of Flora and Fauna. Biol. Bull., vol. 3, pp. 115- 
 131.* 
 
 Tutt, J. W. 1902. The Migration and Dispersal of Insects. 132 pp. 
 London. E. Stock. 
 
 Webster, F. M. 1902. The Trend of Insect Diffusion in North America. 
 32d. Ann. Rept. Ent. Soc. Ontario (1901), pp. 63-67, maps 1-3. 
 
 Webster, F. M. 1902. Winds and Storms as Agents in the Diffusion of 
 Insects. Amer. Nat., vol. 36, pp. 795-801. 
 
 Webster, F. M. 1903. The Diffusion of Insects in North America. 
 Psyche, vol. 10, pp. 47-58, pi. 2. 
 
 Jacobi, A. 1904. Tiergeographie. 152 pp., 2 maps. Leipzig. 
 
464 ENTOMOLOGY 
 
 GEOLOGICAL DISTRIBUTION 
 
 Herr, 0. 1847-53. Die Insectenfauna der Tertiargebilde von Qiningen 
 und von Radoboj in Croatien. 3 Th. 644 pp., 40 taf. Leipzig. 
 From Neue Denks. scliweiz. Gesell. Naturw., bd. 8, 11, 13. 
 
 Scudder, S. H. 1880. The Devonian Insects of New Brunswick. Ann. 
 ^lem. Bost. Soc. Nat. Hist., 41 pp., i pi. 
 
 Scudder, S. H. 1882. A Bibliography of Fossil Insects. Bibl. Contrib. 
 Lilir. Harv. Univ., no. 13. 47 pp. Cambridge, ISIass.* 
 
 Scudder, S. H. 1885. The Earliest Winged Insects of America : a Re- 
 examination of the Devonian Insects of New Brunswick, etc. 8 
 pp., I pi., 2 figs. Cambridge, Mass. 
 
 Scudder, S. H. 1885. Systematische Uebersicht der fossilen Myriopoden, 
 Arachnoideen und Insekten. In K. A. Zittel : Handbuch der 
 Palseontologie, abth. i, bd. 2, pp. 721-831, figs. 894-1109. Trans. 
 1900. C. R. Eastman. Text-Book of Palaeontology, vol. i, pp. 
 682-691, figs. 1441-1476. London and New York. Macmillan & 
 Co.* 
 
 Scudder, S. H. 1886. The Cockroach of the Past. In L. C. Miall and 
 A. Denny. The Structure and Life-History of the Cockroach, pp. 
 205-220, figs. 1 19-125. London and Leeds.* 
 
 Scudder, S. H. 1886. Systematic Review of our Present Knowledge of 
 Fossil Insects. Bull. U. S. Geol. Surv., no. 31, 128 pp. Wash- 
 ington. 
 
 Scudder, S. H. 1889. The Fossil Butterflies of Florissant. Eighth Ann. 
 Rept. Dir. L'. S. Geol. Surv., pp. 433-474, pi. 53. Washington. 
 
 Scudder, S. H. i8go. The Work of a Decade upon Fossil Insects. 
 Psyche, vol. 5, pp. 287-295. 
 
 Scudder, S. H. 1890. A Classed and Annotated Bibliography of Fossil 
 Insects. Bull. U. S. Geol. Surv., no. 69, loi pp. Washington.* 
 
 Scudder, S. H. 1890. The Tertiary Insects of North America. U. S. 
 Geol. Surv. Terr., vol. 13, 734 pp., 28 pis., i map, 3 figs. Wash- 
 ington. 
 
 Scudder, S. H. 1891. Index to the Known Fossil Insects of the World, 
 including Myriapods and Arachnids. Bull. LI. S. Geol. Surv., no. 
 71, 744 pp. Washington.* 
 
 Scudder, S. H. 1892. Some Insects of Special Interest from Florissant. 
 Colorado, and other Points in the Territories of Colorado and 
 Utah. Bull. U. S. Geol. Surv., no. 93. 35 pp., 3 pis. Washington. 
 
 Scudder, S. H. 1893. Insect Fauna of the Rhode Island Coal Field. Bull. 
 LI. S. Geol. Surv., no. loi, 27 pp., 2 pis. Washington. 
 
 Scudder, S. H. 1893. The American Tertiary Aphidre, with a List of the 
 Known Species and Tables for their Determination. Thirteenth 
 Ann. Rept. U. S. Geol. Surv., pt. 2, pp. 341-372, pis. 102-106. 
 ^^^'lshington. 
 
 Scudder, S. H. 1893. Tertiary Rhynchophorous Coleoptera of the LInited 
 States. Monogr. U. S. Geol. Surv.. vol. 21, ii-|-2o6 pp., 12 pis. 
 Washington. 
 
LITERATURE 465 
 
 Brongniart, C. 1894. Rechcrches pour servir a I'histoire des inscctes fos- 
 siles des temps primaires, etc. 2 vols. 537 pp., 37 pis. St. 
 fitienne. 
 
 Scudder, S. H. 1894. Tertiary Tipulidse, with Special Reference to those 
 of Florissant, Colorado. Proc. Amer. Phil. Soc, vol. 32, 83 pp., 9 
 pis. 
 
 Scudder, S. H. 1896. Revision of the American Fossil Cockroaches, with 
 Descriptions of New Forms. Bull. U. S. Geol. Surv., no. 124, 176 
 pp., 12 pis. Washington. 
 
 Goss, H. 1900. The Geological Antiquit}' of Insects. Ed. 2. 4 + 5^ PP- 
 London. Ciurney & Jackson.* 
 
 Scudder, S. H. igoo. Adephagous and Clavicorn Colcoptera from the 
 Tertiary Deposits at Florissant, Colorado, etc. Monogr. U. S. 
 Geol. Surv., vol. 40, 148 pp., 11 pis. Washington. 
 
 Scudder, S. H. 1900. Canadian Fossil Insects. 4. Additions to the Cole- 
 opterous Fauna of the Interglacial Clays of the Toronto District, 
 etc. Contrib. Can. Pal, Geol. Surv. Can., vol. 2, pp. 67-92, pis. 
 6-15. Ottawa. 
 
 INSECTS IN RELATION TO MAN 
 
 Harris, T. W. 1862. A Treatise on Some of the Insects Injurious to 
 Vegetation. Third Ed. 11 +640 pp., 278 figs., 8 pis. Boston. 
 
 Lintner, J. A. 1882. Importance of Entomological Stud}-, etc. First 
 Ann. Rept. Inj. Ins., pp. 1-80, hgs. 1-12. 
 
 Saunders, W. 1883. Insects Injurious to Fruits. 436 pp., 440 figs. 
 Philadelphia. J. B. Lippincott & Co. 
 
 Henshaw, S., and Banks, N. 1 889-1 901. Bibliography of the more im- 
 portant Contributions to American Economic Entomology. 8 pts. 
 1318 pp. Washington.* 
 
 Packard, A. S. 1889. Guide to the Study of Insects. Ed. 9. 12 + 715 
 pp., 668 figs., 15 pis. New York. Henry Holt & Co. 
 
 Howard, L. 0. 1894. A Brief Account of the Rise and Present Condition 
 of Ofificial Economic Entomology. -Insect Life, vol. 7, pp. 55-107. 
 
 Sempers, F. W. 1894. Injurious Insects and the Use of Insecticides. 
 10 -j- 216 pp., I pL, 184 figs. Philadelphia. W. A. Burpee & Co. 
 
 Smith, J. B. 1896. Economic Entomology for the Farmer and Fruit- 
 Grower, etc. Pp. 12+11-481, 483 figs. Philadelphia. J. B. 
 Lippincott Co. 
 
 Howard, L. 0. 1899. The Economic Status of Insects as a Class. Sci- 
 ence, vol. 9 (n. s.), pp. 233-247. 
 
 Theobald, F. V. 1899. A Text-Book of Agricultural Zoology. 17-1-511 
 pp., 225 figs. Edinburgh and London. Wm. Blackwood & Sons. 
 
 Howard, L. 0. 1900. Progress in Economic Entomology in the United 
 States. Yearbook V. S. Dept. Agric, 1899, pp. 135-156. pi. 3. 
 31 
 
466 ENTOMOLOGY 
 
 Sanderson, E. D. 1902. Insects Injurious to Staple Crops. 10 + 295 
 pp., 163 figs. New York. John Wiley & Sons. 
 Most of the literature on the economic entomology of the United States 
 is contained in the following works : Reports U. S. Ent. Comm. ; Repts. 
 Govt. Entomologists; Bulletins U. S. Dept. Agric, Div. Ent; Insect Life; 
 Reports and Bulletins by the several State Entomologists ; Bulletins of the 
 various Experiment Stations. 
 
NDEX 
 
 An asterisk * denotes an illustration. 
 
 Abdomen, 65 ; appendages of, *67. 
 *i5o, *i52; extremity, 68; moditica- 
 tions, 66 ; segments, 65 
 
 Acacia, *272, 272 
 
 Accessory glands, *i40, *i4i, *i42 
 
 Achonites, *9, 10 
 
 Acquired characters, 243 
 
 Acridiida?, *io, 11 : moults of, 165; 
 spiracles, 66 
 
 Acridiiiiii, 27; respiratory muscles of, 
 *I39 
 
 Aculeata, 21 
 
 Adams, on dispersal, 383 
 
 Adaptations, of larv?e, 165 ; of legs, 51, 
 *53 ; of mandibles, 37, *38 ; origin 
 of, 237 ; protective, 297 
 
 Adaptive coloration, 216; classifica- 
 tion, 234 : evolution, 236 ; variation, 
 241 
 
 Adelung, von, 428 
 
 Adler, 418, 454 
 
 Adventitious resemblance, 219 
 
 Ageronia, 104 
 
 Aggressive resemblance, 235 
 
 As-rionidK, caudal gills of, *i34 
 
 Air-sacs, 133 
 
 Alary muscles, *i25 
 
 Albinism, 201 
 
 Alexander, 450 
 
 Alimentary tract (see Digestive Sys- 
 tem). 
 
 Alluring coloration, 235 
 
 Alternation of generations. 256 
 
 Amans, 417, 445 
 
 Amber insects, 385, 389 
 
 Ametabola, 159 
 
 Ammophila, *36o, 363 
 
 Amnion, *i48. 149. *i53 
 
 Aiiiphidasis. 199 
 
 Amphimixis, 243 
 
 Aiuphipyra. 347 
 
 Ampullaceum, *9S, 96 
 
 Anajapyx. *6, 22 
 
 Anal glands. 81, *ii7 
 
 Anasa. *i58 
 
 Androconia. *79, 80 
 
 Anemotropism, 347 
 
 Anergates. 336 
 
 Angrcrcnin, 262 
 
 Anisota, "171 
 
 Anisotropic, 87 
 
 Annelids, in relation to arthropods, 
 5. *7 
 
 Aiiomma, 335 
 
 .Inopheles, 302, 303 
 
 Anophthalmus, 114 
 
 Anosia berenice, 380 ; plc.vippits. an- 
 tenna of, *34 ; dispersal, 369 ; eclo- 
 sion, 172; so-called mandibles, 41; 
 mimicked, ^224, 232; pupa, *i68 ; 
 pupation, 168; scale, *77 ; wing, 
 *6o 
 
 Antecoxal piece, *49 
 
 Antennx, forms of, +34 ; functions of, 
 34 ; sexual differences in, *35 
 
 Antennal comb, *27'o, 271 ; neuromere, 
 *46 ; segment, 45 ; sensilla, 94, *9S 
 
 Anthonomns, 397 
 
 Anthrax, 306 
 
 Anthrenus. *77 
 
 Antigeny, 35, 205 
 
 Ant-plants, ^272 
 
 Ants, castes of, 330; color sense, 114; 
 facets, 32 ; general account, 330 ; 
 habits, 333 ; harvesting ants, 340 ; 
 honey ants, 2,36, ^2,37: hunting ants, 
 335: larvae, 331; leaf-cutting, 337, 
 ♦338 : nests, 331 : slave-making, 336 
 
 Annrida, development of mouth parts, 
 *iSi ; germ band, *iso ; habits, 191 ; 
 pigment, 197 
 
 Anus, *72, 121 
 
 Aorta, *I2S, *i26 
 
 Apanfeles, 310, *3ii 
 
 Apatetic colors, 234 
 
 Apatiira. scales, 193 ; colors, 195 
 
 Aphaniptera, 19, *2i 
 
 Aphid ins. 310 
 
 Aphids, galls of, ^255 : in relation to 
 ants, 341 
 
 Apis mellifera, antennal sensilla, *gs ; 
 cephalic glands, 122 ; comb, *222 ; 
 control of sex, 327 ; determination 
 of caste, 327 ; foot, *S4 ; general 
 account, 321 ; hair, *269 ; larvse, 
 *324 ; legs, +270 : mandible, +38 ; 
 mimicry, 225 : modifications in rela- 
 tion to flowers, *27o, 271 ; moults, 
 
 467 
 
468 
 
 165 ; mouth parts, *44 ; ocellus, 
 *i09, *iio; ovipositor, *70 ; repro- 
 ductive system, *i4i ; tongue, *97 ; 
 wax, *83, *322, *323 
 
 Apneustic, 134, 189 
 
 Apodemes, *so 
 
 Apodous larvae, 47, 55 
 
 Apophyses, *5o 
 
 Aporus, 363 
 
 Appendages, development of, *i49 
 
 Apple, insects of, 253 
 
 Aptera, 8 
 
 Apterygota, 10 
 
 Aquatic insects, adaptations of, 184; 
 food, 184; locomotion, 186; origin, 
 192 : respiration, 188 ; systematic po- 
 sition, 184 
 
 Arachnida, *2, 3 
 
 Arctic realm, 375 
 
 Arista, *34 
 
 Aristida, 340 
 
 Arms, J. M., 410, 412, 443, 444 
 
 Army worm, 383 
 
 Artemia, 243 
 
 Arthropoda, characters of, *i ; classes, 
 2 ; interrelationships, 5 ; naturalness 
 of phylum, 7 ; phylogeny, *7 
 
 Asclepias, *262, *263 
 
 Asecodcs, 312 
 
 Ashmead, on Hymenoptera of Hawaii, 
 373 
 
 Assembling, 102 
 
 Atemelcs, 342, *343 
 
 Attn, 335, 337, *338 
 
 Attacus, 27 
 
 Auditory, hairs, 107 ; organs, 106, *io7 
 
 Audouin, 416 
 
 Aughey, on insectivorous birds, 288, 
 455 
 
 Austral region, 377 
 
 Australian realm, 376 
 
 Atitonieris, 81 
 
 Ayers, on abdominal appendages, 67, 
 440 
 
 Bailey, 453 
 
 Balancers, 58 
 
 Baldwin, 452, 453, 459 
 
 Ballowitz, 438 
 
 Banks, 409, 410, 465 
 
 Barlow, 434 
 
 Barriers, 368 
 
 Basch, 415, 423, 429 
 
 Basement membrane, *74, 75, *79, *85, 
 
 *I2I 
 
 Basiconicum, 94, *95 
 Basidium, ^258 
 
 Basilarchia, mimicry, *224, 232 ; pro- 
 tective resemblance, 218 
 
 Bates, on mimicry, 225 ; 450, 461, 462 
 
 Batesian mimicry, 226 
 
 Bateson, 448, 452 
 
 Beal, on food of robin, 285, 455 
 
 Beddard, 447, 450, 463 
 
 Bees, color sense of, 114; hairs, *75 
 
 Beetles, sounds of, 104 
 
 Behavior of insects, 345 
 
 Bell, 453 
 
 Bellesme, de, 429 
 
 Belostoma, digestive system of, *i20 ; 
 predaceous, 185, 276 
 
 Belt, on leaf-cutting ants, 338, 461 
 
 Benacus, *i6; caecum, 120; mouth 
 parts, *4i ; predaceous, 185 
 
 Beneden, van, 457 
 
 Beneficial insects, 395 
 
 Benton, on honey bee, 324, 325, 454, 
 458 
 
 Berlese, on phagocytosis, 180 
 
 Bernard, H. M., 412 
 
 Bernard, M., 441 
 
 Bertkau, on hermaphroditism, 143, 438 
 
 Bessels, 437 
 
 Bethe, on behavior of ants, 334, 460 
 
 Bethune, 408 
 
 Beyer, 419 
 
 Binet, 425 
 
 Birches, insects of, 252 
 
 Birds, insectivorous, 284, 287, 291 ; 
 regulating insect oscillations, 289 
 
 Bittacomorpha, *i35, 189 
 
 Bittacus, *i7, 52 
 
 Black-flies, 276 
 
 Blackiston, 450 
 
 Blanc, 415, 430 
 
 Blanchard, 424, 431, 457 
 
 Blandford, 456 
 
 Blastoderm, *i47 
 
 Blastogenic variations, 241, 243 
 
 Blastophaga, 407 
 
 Blatta, muscles of, *86, 87 ; respira- 
 tion, *i38 
 
 Blattidse, 11 ; spiracles of, 66 
 
 Blind insects, 33 
 
 Blissiis leucopterus, distribution of, 
 382 ; losses through, 393 ; food of, 
 398 
 
 Blochmann, 440 
 
 Blood, corpuscles, 127; course of, 
 *i25, *i26 ; function, 127 
 
 Bluebird, food of, 286 
 
 Boas, 444 
 
 Bobretzky, 440 
 
 Bolton, 409 
 
 Bombus, antenna of, *34 ; general ac- 
 count, 328 : larva, *i62 ; mimicry, 
 *235 ; respiration, *i38; taste cup, 
 *99 
 
469 
 
 Bombyx mori, Malpighian tubes of, 
 
 *I24; mid intestine, *i2i ; cenocytes, 
 
 *i3i ; silk glands, *84, *85 
 Bordas, 423, 431 
 Boreal region, 376 
 Borgert, 422 
 Bot flies, 278 
 Brachiniis, 82 
 BraconidjE, 310 
 
 Brain. *9o. *9i ; functions of, 93 
 Branchial respiration, 190 
 Brandt, A., 439 
 Brandt, E., 424, 425 
 Brauer, on classification, 9 ; types of 
 
 larvK, 162; 411, 417, 437, 44^ 
 Braula, 309 
 Braun, 457 
 
 Breed, on phagocytosis, 180 
 Breitenbach, 415 
 Breithaupt, 415 
 Briant, 415 
 Brongniart, on Carboniferous insects, 
 
 384, 387, 46s 
 Brooks, 414 
 Brnchophagus, *iS9 
 Brues, 458 
 
 Brunner von Wattenwyl, 449 
 Bugnion, 182, 443 
 Bumble bees, general account, 328 
 Bureau of Entomology, 407 
 Burgess, 42, 415, 418, 432 
 Burmeister, 410, 411 
 Bursa copulatrix, ^142 
 Buthus, *2, 3 
 Butler, 450 
 
 Biitschli, 424, 437, 439, 440 
 Butterflies, eclosion of, 172; fossil, 
 
 *390 
 
 Cabbage butterfly (see Pieris rapcc) 
 
 Cseca, gastric, *ii6, *ii7, 119 
 
 Ccecilius, *i22, ^123 
 
 Cfficum, *i 19, *i20 
 
 Cajal, 435 
 
 Calliphora, compound eyes of, *iix, 
 
 *II2 
 
 Callosamia, antenna:, 35 ; assembling, 
 
 102; cocoon, 170; odor, 82; sexual 
 
 coloration, *207 
 Caloptenus , olfactory organ of, *99 ; 
 
 tympanal organ, *io7 
 Caloptcry.v, development of, *i53: 
 
 sexual coloration, 206 
 Campodca, 6, *8, 9, 22, 66, *i62 
 Candeze, 421 
 
 Canker worms, as food of birds, 289 
 Cannon, on phototaxis, 351 
 Canthon. *53 
 Capitate, *34 
 
 CarabidK, anal glands of, 81, *ii7; 
 
 predaceous, 308 
 Carabidoid larva, *i75 
 Carabus, alimentary tract of, *ii7 
 Carboniferous insects, 384, 386 
 Cardiac valve, *ii5, 116, 118, 119 
 Cardo, *38, 39 
 Carlet, 417, 419 
 Carpenter, F. W., 461 
 Carpenter, G. H., on relationships, 5, 
 
 7; 410, 413, 445, 463 
 Carriere, 427, 441 
 Carrion insects, 279 
 Carus, 409 
 Catbird, food of, 285 
 Caterpillar, 156; pupation of, 168 
 Catocala, scent tufts of, 54 ; protective 
 
 resemblance, *2i8 
 Catogenus, antenna of, 34 
 Cattie, 425 
 Caudal gills, 190 
 
 Cccidoniyia, egg of, *i59, 160; ovipos- 
 itor, *68, 69 ; psedogenesis, 145 
 Cecidomyiidre, galls of, 255 
 Cecropia adenopns, *273, ^274 
 Cccropia moth (see Saiiiia) 
 Centrolecithal, *i47 
 Ceramby.v, facets of, 32 ; ovipositor, 
 
 *68, 69 
 Ceratina, 316 
 Cerceris, 363 
 Cerci, *8, *67, *7i, *7t, 
 Cercopoda, 68 
 Centra, 82 
 
 Cervical sclerites, 30 
 Chseticum, 94, *95 
 Chalcididse, 27, 310 
 Chapman, 442, 447 
 Chelostoma, *75 
 Chemotropism, 345 
 Cheshire, on honey bee, *44, 71, 272. 
 
 322. 454, 457 
 Child, 428 
 Chilopoda, *4 
 Chinch bug, distribution of, 382 ;• food 
 
 of, 398 ; losses through, 393 
 Chionaspis. i6\ 
 Chirononius, nervous system of, *9i ; 
 
 pupal eggs, 14s ; food, 185 
 Chitin, 73 
 
 Chlorophyll, as a pigment, 195, 215 
 Cholodkovsky, 412, 430, 440, 441 
 Chordotonal organs, *io8 
 Chorion, *i46, *i6o 
 Christy, 456 
 Chromosomes, 146 
 Chrysalis, 157 
 Chrysobothris, integument of, *74 
 
470 
 
 INDEX 
 
 Chrysomelidas, silk glands of, 85 
 
 Chrysopa, *i7; cocoon of. *i6g\ lay- 
 ing eggs, *i6o; mandibles, *38 ; 
 predaceous, 308 ; silk glands, 85 
 
 Chun, 421 
 
 Cicada, metamorphosis of, *i58; 
 moults, 165 ; sound, 104 
 
 Cicindcla, leg of, *S3 ; mandible, *38 ; 
 predaceous, 308 ; variation in color- 
 ation, *2I3 
 
 Cimbex, repellent glands, 81 
 
 Circular muscles, *i2i 
 
 Circulation, *i26, 127 
 
 Circulatory system, 124 
 
 Claparede, 426 
 
 Claspers, *7i, *72 
 
 Claus, 411, 421, 437 
 
 Clavate, *34 
 
 Claypole, 442 
 
 Climatal coloration, 200 
 
 Clisiocampa, number of eggs of, 161 
 
 Clisodon, 268 
 
 Cloaca, 69 
 
 Clover, insects of, 252 ; pollination of. 
 266 
 
 Clypeus, 30, *42 
 
 Clytra, embryology of, *i47, *i48, 
 *iS4. *i55 
 
 Cnemidotus, 135 
 
 Coarctate pupa, 168 
 
 Coccinella, distribution of, 378 
 
 Coccinellidae, predaceous, 308 ; silk 
 glands, 85 
 
 Cockroach, cephalic ganglia of, *<)i 
 fossil, ^387, 388 ; mouth parts, *Z7 
 muscles, *56, *86 ; respiration, *i38 
 salivary gland, *i22; spermatozoon, 
 *i4i 
 
 Cocoon, 169, *i7o 
 
 Coeloconicum, 94, *95 
 
 Cnelom sacs, *i54 
 
 Coleoptera, 18, *2o, 24 
 
 C alias, albinism of, 201 ; color .sense, 
 115: sexual coloration, 205, *2o6 
 
 Collembola, alimentary tract of, *ii5; 
 defined, 10; furcula, 68; primitive 
 condition, 22 ; ventral tube, 68 
 
 Colletes, hairs of, *7S 
 
 Colon, 120 
 
 Colopha. gall of, *2SS 
 
 Color, effects of food on, 196 ; sources 
 of, 193 
 
 Coloration, adaptive, 216, 234; ch- 
 matal, 200; development of, 210: 
 effects of moisture and temperature 
 on, 199 ; seasonal, 201 : sexual, 205 : 
 variation in, 211 ; warning, 221 
 
 Color patterns, development of, 210; 
 
 origin, 208 
 Colors, combination, 195 ; pigmental, 
 
 194 ; structural, 193 
 Color sense, 114 
 Commissures, 90, *gi 
 Complete metamorphosis, 156 
 Compound eyes, *3i ; origin of, 114; 
 
 physiology, m; structure, *iio, 
 
 III, *II2 
 
 Comstock, A. B., on ants, 145. 331 ; 
 ■ 410, 412 
 Comstock, J. H., on venation, 58 ; 403, 
 
 406, 410, 412, 414, 416, 417, 435, 
 
 445, 446 
 Cone cells, iii, *ii2 
 Conidia, *258 
 Conidiophores, *258 
 Connold, 455 
 Cook, 455 
 Cooke, 454 
 
 Cope, on segmentation, 28 ; 452 
 Copidosoma, 311 
 Copris, spermatozoon of, *i4i 
 Coquillett, 404 
 Corbiculum, *27o, 271 
 Cordyceps, *2S7 
 Corethra, chordotonal organs of, *io8; 
 
 imaginal buds, *i79, 180 
 Corn insects, 253 
 Cornea, no, *iii, *ii2 
 Corrodentia, 11. 12 
 Corydaloides, 387 
 Costa, *59 
 Coste, 447 
 
 Cotton boll weevil, 397 
 Cotton worm, 393 
 Cowan, 455 
 Coxa, *49, *5i, *53 
 Cremaster, 168 
 Cremastogaster, 333 
 Creutzburg, 432 
 Cricket, stridulation of, 106 
 Crioceris, 381 
 Crop, *ii7, *ii8 
 Crustacea, 2 
 Cryptorhynchus, 381 
 Crystalline cone, no, in, *ii2 
 Ctcnocephahis, 19, *2i 
 Cubitus, *59 
 
 Cuenot, 422, 423, 431. 433 
 Culcx, antennae of, *36 ; characteristics 
 
 of, 303 ; filariasis transmitted by, 
 
 305 ; larva, *i88 ; mouth parts, *43 ; 
 
 respiration, *i88, 189 
 Cutaneous respiration, 189 
 Cuticula, -/T,, *74, *76 
 Cuticular colors, 194 
 
471 
 
 Cyaiiiris pscudargiolus, coloration of, 
 
 199; geographical varieties, Z7Z'- 
 
 melanism, 201 ; polymorphism,* 202 ; 
 
 sexual coloration, 206 
 
 Cybister, leg of, *i87; locomotion, 
 
 186. 188 
 Cyclints, stridulation of, 104 
 Cyllenc, metamorphosis of, *i56 
 Cynipidze, abdomen of, 66 ; galls, *254 ; 
 
 parthenogenesis, 145, 256 
 Cyrtophyllus, stridulation of, iu6 
 
 Dahl, 417, 422, 424 
 
 Dallinger, on acclimatization, 242 
 
 Darkness, as affecting pigmentation, 
 197 
 
 Darts, *7o 
 
 Darwin, on instinct, 361 ; natural se- 
 lection, 238 ; origin of species, 245 ; 
 451, 453, 461 
 
 Davenport, on phototaxis, 351 ; 459 
 
 Davis, 419 
 
 Dearborn, on insectivorous birds, 287, 
 289, 291, 456 
 
 Deegener, 444 
 
 Delage, 452 
 
 Demoor, 417 
 
 Denny, on chitin, 74 ; on muscles, 87 ; 
 410, 414, 424 
 
 Dermaptera, 1 1 
 
 Dermestids, 280 
 
 Deutocerebrum, 90, 152 
 
 Deutoplasm, *i46 
 
 Development, 146 
 
 Devonian insects, 384, 385 
 
 Dewitz, 417, 418, 419, 432, 435, 436, 
 443, 445 
 
 Diabrotica, distribution of, 380 
 
 Diacrisia, cocoon of, 170 
 
 Diaphcromcra, *2i7 
 
 Diastole, 128 
 
 Dibrachys, 312 
 
 Dichoptic, *22 
 
 Dickel, on control of sex, ^,27 ; on fer- 
 tilization, 145 ; 458 
 
 Dictyonenra, 387 
 
 Dietl, 424 
 
 Digestive system, 116 : of beetle, *ii7 ; 
 Bclostoma, *i2o; Collemljola, *ii5: 
 grasshopper, *ii6; histology, *i2i ; 
 moth, *ii9; Myri)ieleou, *ii8 
 
 Digoneutic, 204 
 
 Dimmock, on assembling, 103 ; on 
 mouth parts of mosquito. 42. *43 : 
 415, 422, 446, 455 
 
 Dimorphism, 202 
 
 Diuarda, 342 
 
 Diitcutiis, antenna of, *34 ; eyes of, 
 
 *3i 
 Diplopoda, *3 
 Diptera, 19, *20 ; eyes of, *32; hal- 
 
 teres, 116; mouth parts, 42, *43 ; 
 
 origin, 24; sounds, 103; spiracles, 
 
 66 
 Directing tube, 85 
 Direct metamorphosis, 157 
 Diseases, their transmission by in- 
 sects, 299 
 Dispersal, 366 ; centers of, 383 ; means 
 
 of, 367 ; in North America, 377 
 Dissosteira, protective resemblance of, 
 
 219 ; stridulation, 104 
 Distant, 462 
 Distribution, former highways of, 
 
 370; geographical, 366; geological, 
 
 384 
 Dixey, on evolution of mimicry, 233 ; 
 
 447, 448, 450, 451 
 Dogiel, 431 
 Dohrn, 439 
 
 Dolbear, on stridulation, 106 
 Dolichopodidie, 54 
 Donacia, 88, 184, 189 
 Dorfmeister, 446 
 Dorsal closure, 151, *iS4 
 Dorsal vessel, 124, *i25 
 Doyere, 436 
 
 Drift, insect, 191 
 
 Drone, *32i, 322 
 
 Drosera, 256 
 
 Drosophila, egg of, *i59 
 
 Dubois, 433 
 
 Ductus ejaculatorius, *i40, 141, 142 
 
 Dufour, 421, 429, 432, 433, 434, 436, 
 445 
 
 Durham, 456 
 
 Dutrochet, 433, 436 
 
 Dyar, on moults, 165 
 
 Dynastes Hercules, 27 ; tityiis, distri- 
 bution of, 380 
 
 Dytiscus, caecum of, 120 ; leg of, *53 ; 
 predaceous, 276 ; respiration, 189 
 
 Ecdysis, 159, 164 
 
 Eciton, *338 ; eyes of, 32 ; habits, 276, 
 
 331, 335 
 Eckstein, 454 
 Eclosion, 172 
 
 Economic entomologist, 398 
 Ectoderm, *i48 
 Edwards, on /. aja.v. 203 : on P. fharos, 
 
 204; 421 
 Egg-guide, *73 
 Egg-nucleus, *i46 
 
472 
 
 Eggs, form of, *i59; number, i6i ; 
 size, i6o 
 
 Eimer, 452, 459 
 
 Ejaculatory duct, *i40, 141, 142 
 
 Elaphnts. stridulation of, 104 
 
 Elimination of unfit, 240 
 
 Ellenia, protective resemblance of, 218 
 
 Elm, insects of, 252 
 
 Elwes, 462 
 
 Elytra, 58 
 
 Embia, 12 
 
 Embiidae, 11, *i2 
 
 Embryology, 146 
 
 Emery, 430, 433 
 
 Eniesa, 366 
 
 Empis. nervous system of, *9i 
 
 Empodium, 51 
 
 Empitsa, *258, 259 
 
 Enderlein, on Platyptera, 13, 23, 413 
 
 Endoskeleton, *so 
 
 Engelmann, 409 
 
 Enteman, on habits of Polistcs, 330, 
 36s : 450, 458, 460 
 
 Entoderm, 148, 154, *I5S 
 
 Entomophthoracese, *258 
 
 Environmental variations, 242 
 
 Ephemerida, 13, *i4; abdominal seg- 
 ments of, 66 ; eyes of, 33 ; origin, 23 
 
 Epicaiita, hypermetamorphosis of, 174, 
 *I7S _ 
 
 Epicranium, *2g 
 
 Epigamic colors, 235 
 
 Epimeron, 48, *49 
 
 Epipharynx, 37 
 
 Episternum, 48, *49 
 
 Epitheca, dorsal vessel of, *I2S, *i26 
 
 Erebus agrippina. 27 ; odora, distribu- 
 tion of, 367, 380 
 
 Ergatoid, 331 
 
 Eriocephala. mouth parts of, 42 
 
 Eristolis. mimicry by, *225 ; respira- 
 tion, 189 
 
 Eruciform larvae, 24, *i62, 163, 178 
 
 Erynnis manitoba, distribution of, *377 
 
 Escherich, 420, 438 
 
 Ethiopian realm, :i-/6 
 
 Etiolin, 215 
 
 Etoblattina, *387 
 
 Eudamtts proteus. distribution of, 377 
 
 Eugereon, 388, *389 
 
 Euphoria, moiith parts of, 38, *268, 
 269 
 
 Euplexoptera, 1 1 
 
 Euplaca. colors of, 195 
 
 Euproctis, 352 
 
 Euschistus, antenna of, *34 
 
 Eutermes, 320 
 
 Euthrips, *is 
 
 Everes, androconium of, *79 
 
 Excrements, 120 
 
 Exner, on compound eyes, iii, 112, 
 428, 459 
 
 Expiration, 139 
 
 Exuvi^e, 165 
 
 Eyes, compound, *3i, no; kinds of, 
 *3i ; simple, *t,2, *io9 ; sexual dif- 
 ferences in, *22, 
 
 Fabre, J. H., on Sphcx, 359 : 432, 457, 
 459 
 
 Fabre, J. L., 429, 442 
 
 Facets. *3i 
 
 Fat-body, distribution of, 128, *i29; 
 functions, 130 ; structure, *i30 
 
 Fat-cells, 129, *i3o 
 
 Faunje of islands, 371 
 
 Faunal realms, 374 
 
 Faussek, 430 
 
 Felt, E. P., 403 
 
 Female genitalia, *69 
 
 Femur, *49, *si, ^53 
 
 Fenard, 439 
 
 Fenestrate membrane, in, *ii2 
 
 Fenger, 418 
 
 Feniseca, 309 
 
 Fernald, C. H., on gypsy moth, 253, 
 402 
 
 Fernald, H. T., 412, 422 
 
 Fertilization, 147 
 
 Fidonia, antennal sensilla, *9S, 102 
 
 Fielde, on ants, 331, Z3i, 334, 35°, 
 458, 460 
 
 Filariasis, 305 
 
 Filiform, *34 
 
 Filippi's glands, *84 
 
 Finlay, 456 
 
 Finn, on mimicry, 230 ; warning col- 
 oration, 222, 450 
 
 Fire-flies, 131 
 
 Fischer, 449 
 
 Fishes, insectivorous, 281 
 
 Fitch. 403 
 
 Flagellum, *34 
 
 Fleas. 19, *2i, 278 
 
 Fletcher, 407 
 
 Flight, mechanics of, 62 
 
 Flogel, 425 
 
 Fluted scale, 395, 406 
 
 Follicles, 141, 143, *i44 
 
 Folsom, 413, 416 
 
 Food, its effects on color, 196 
 
 Food reservoir, 118, *ii9 
 
 Forbes, H. O., 461 
 
 Forbes, S. A., on corn root louse, 
 341 ; on economic entomologist, 
 398 ; food of Carabids, 308 ; insec- 
 
INDEX 
 
 473 
 
 tivorous birds, 284 ; insectivorous 
 
 fishes. 281 ; insect oscillations, 289 ; 
 
 interactions of organisms, 292 ; 
 
 404; 454, 455, 456, 457 
 Forbush, on gypsy moth, 253, 403 
 Fore intestine, *iis, *ii6 
 Forel, on ants, 331, ^^2 ; on taste, 96 : 
 
 421, 426, 427, 460 
 Forficulid.-E, 1 1 
 
 Formative cells, *76, 78, *79 
 Formica cxsectoidcs. mountls of, 332 ; 
 
 fitsca. 330, 335, 336; pratcnsis, eyes 
 
 of, a ; sangiiinea. 336 
 Fossil insects, localities for, 384 
 Fossilization, 384 
 Free pupa, 168 
 French, G. H., 404 
 Frenulum, 58 
 Frenzel, 429, 430 
 Front. *29 
 
 Frontal ganglion, *9i, ^^92 
 Functional variations, 242 
 Fundament, 150 
 Fungi of insects, *2S7, *258 
 Furcula, 68 
 
 Gadeau de Kerville, 433 
 
 Gad flies, 276 
 
 Galapagos Ids., Orthoptera of, 371 
 
 Galea, *37, *38, 39 
 
 Galerita, anal glands of, 82 ; antenna, 
 *34 : sternites, *49 
 
 Galls, *254 
 
 Ganglia, cephalic, ^^46, 90, *9i ; func- 
 tions of, 93 
 
 Ganglion, structure of, 92, *93 ; sub- 
 cesophageal, *90, *9i ; supracesopha- 
 geal, *90, *9i 
 
 Ganglion cells, 92, *93 
 
 Ganin, on Platygastcr. *i76, 442; 443 
 
 Garman, 445 
 
 Gastric caeca, *ii6, *ii7, 119 
 
 Gastropacha, larval coloration, 198 ; 
 stinging hair, *8i 
 
 Gastrophilns. 278 
 
 Gastrulation, *i48 
 
 Gehuchten, van, on digestion, 119; 
 424, 430 
 
 Geise, 415 
 
 Gens, 30 
 
 Geniculate, *34 
 
 Genitalia, 68 ; of female, *69 : grass- 
 hopper, *73 : male. *7i ; moth, *72 
 
 Geographical, distribution, 366 ; va- 
 rieties, 373 
 
 Geological distribution, 384 
 
 Geometridae, legs of larvre of. 55 
 
 Geotropism, 348 
 
 Gerephemera, 386 
 
 Germ band, *i47, *i48: types of. 151 
 
 Germ cells. 146 
 
 Germinal vesicle, 146 
 
 Gerris, *i85 ; locomotion of, 188 
 
 Gerstacker, 434 
 
 Gibson, 454 
 
 Gill. T.. 461 
 
 Gillette, 405 
 
 Gills, *i34, *I3S, *i90 
 
 Gilson, 430, 436, 437, 446 
 
 Girault, on numbers of eggs, 161 
 
 Gizzard. 118 
 
 Glaciation. its effects on distribution, 
 
 370 
 Glands, 80; accessory. *i4o. *i4i, 
 
 *i42 ; alluring, 82 ; repellent. 81 ; 
 
 salivary, 121, *i22: silk. 83, *84 ; 
 
 wax, *83 
 Glandular hairs, *8o, *8i 
 Glossa, *37, *39 
 Glossina, 276, 306 
 Glover. 406 
 Goddard, 420 
 Golgi, on malaria. 301 
 Goliathiis, endoskeleton of, *so 
 Gonapophyses, *69 
 Gongylus, 235 
 Gonin. 444 
 Goossens, 419, 422 
 Goss, 465 
 Gosse. 419 
 Gottsche. 426 
 Gould, 447 
 Graber, on chordotonal organ, *io8 ; 
 
 halteres, 116; hearing. *io7 ; 410. 
 
 417, 418, 419, 420, 426, 427. 43.1, 
 
 440. 441. 4Sq 
 Grasshopper, alimentary tract of. *i 16 ; 
 
 genitalia. *73 ; hearing, *io7 
 Grassi, on Tcniics. 317. 318; 411, 456, 
 
 458 
 Gregson. on coloration. 196 
 Grenacher, on the compound eye, iii, 
 
 114, 427 
 Grobben, 412 
 Gross. 439 
 Growth. 164 
 Grub. 157 
 Grube. 433 
 Griinberg, 439 
 Gryllidae, 11 
 Gryllotalpa, leg of. *53 : maternal care, 
 
 31S 
 GryUus, sense hairs. *ioi ; stridula- 
 
 tion. 106 
 Gula. 30. 39 
 
 Gulick, on isolation. 249. 453 
 Gypsy moth (see Porthetria). 
 
474 
 
 Gyrinidje, eyes of, *3i 
 Gyriiius, locomotion of, i88; respira- 
 tion, 189; tracheal gills, 135 
 
 Haase, 411, 412, 419, 435, 450 
 
 Haemolymph, 127 
 
 Hagen, on Tcniics, 318 : 409, 434, 
 435, 445. 446 
 
 Hagens, von, 419 
 
 Hairs, development of, *76 ; functions, 
 76 ; histology, *76 ; modifications, 
 *75. 76 ; pollen-gathering, *269 ; pro- 
 tective, 298 ; tenent, *8o 
 
 Halisidota, distribution of, 379 
 
 Haller, 435 
 
 Halobates, 191, 366 
 
 Halteres, 58, 116 
 
 Hamilton, on holarctic beetles, 375, 
 462 
 
 Hammond, 417, 444 
 
 Hamuli, 58 
 
 Hansen, 412, 413, 415 
 
 Harpalus, labium of, *39 ; maxilla, *38 
 
 Harris, 402, 465 
 
 Hart, 446 
 
 Hartman, 461 
 
 Hatching, 161 
 
 Hatschek, 439 
 
 Hauser, on smell, 98, 427 
 
 Haviland, on termites, 320 
 
 Hawaii, beetles of, 2,72 ; Hymenop- 
 tera, 373 
 
 Hay ward, on stridulation, 106 
 
 Head, 28 ; segmentation of, 44, *46 
 
 Hearing, 106 
 
 Heart, *i25, *i26 
 
 Heath, on Tcnnopsis, 318: 458 
 
 Heer, on fossil insects, 385. 389, 464 
 
 Heider, 440, 441, 444 
 
 Heilprin, 463 
 
 Heim, 454 
 
 Heinemann. 433 
 
 Heliconiid?e, mimicry, 225 
 
 Heliophila, 383 
 
 Helm, 429 
 
 Hemelytra, 58 
 
 Hemerocampa, parasites of, 312 
 
 Hemimeridas, 1 1 
 
 Hemiinenis, *io ; hypopharynx of, *40 
 
 Hemiptera, defined, *i6: mouth parts, 
 
 40, *4i ; odors, 82 ; origin, 2;^ 
 Henking, 438, 440, 441 
 Henneguy, 410 
 Hensen, 426 
 Henshaw, 409, 465 
 
 Henslow, on self-adaptation, 243, 452 
 Hcptagcnia, hypopharynx, *4o 
 Hermaphroditism, 143, *i44 
 
 Hesse, 429 
 
 Hessian fly, losses through, 393 
 
 Hetcrrins, 343 
 
 Heterocera, defined, 18 
 
 Heterogeny, 145 
 
 Heterometabola, 157 
 
 Heterophaga, 21 
 
 Heteroptera, defined, *i6 ; spiracles of, 
 66 
 
 Hcxageiiia. 13, *i4 : male genitalia. 
 *7x ; tracheal gills, *i34 
 
 Hexapoda, defined, 4 
 
 Heymons, 412, 413, 420, 438, 442 
 
 Hicks, on olfactory pits, loi 
 
 HicKson, 427 
 
 Higgins, 446 
 
 Hilton, 423 
 
 Hind intestine, *ii7, *i20 
 
 Histogenesis, 180 
 
 Histolysis, 180 
 
 Hoffbauer, 417 
 
 Holarctic realm, 375 
 
 Holcaspis, galls of, *254 
 
 Holmes, 461 
 
 Holmgren, 416, 425, 436, 439 
 
 Holometabola, 156 
 
 Holopneustic, 134, 188 
 
 Holoptic, *T,T, 
 
 Homoptera, defined, 16 
 
 Honey, 326 
 
 Honey ants, 336, *i27 
 
 Honey bee (see Apis mcUifera) 
 
 Hopkins, A. D., 405 
 
 Hopkins, F. G., on pigments, 196, 
 447. 448 
 
 Hoplia, sexual coloration of, 207 
 
 Horn, on Cicindela, 214 
 
 House fly (see Musca) 
 
 Howard, on Crioceris, 381 ; economic 
 entomology, 402, 407 ; parasitism, 
 312: 410. 456, 457, 458, 463, 465 
 
 Hubbard, on parasitism, 313 
 
 Huber, on wax, 322 
 
 Hudson, 462 
 
 Humboldtia, 27Z 
 
 Hunter, 410 
 
 Hutton, 413 
 
 Huxley, on aphids, 238 ; 414, 437 
 
 Hyaloplasm, 88 
 
 Hyatt and Arms, quoted, 22 ; on accel- 
 eration of development, 178; 410, 
 412, 443, 444 
 
 Hybcniia, 196 
 
 Hydnopliytiiin, *275 
 
 HydrophiJus, 18, *20, *i85 ; antennae, 
 35 : leg, *i87 ; locomotion, 186 ; male 
 genitalia. *7i : respiration, 189 
 
 Hydrotropism, 346 
 
INDEX 
 
 475 
 
 Hydrous, tergites of, *48 
 
 Hylastes, 381 
 
 Hylobius, glandular hairs of, *8o 
 
 Hymenoptera, defined, 19 ; cephalic 
 glands, 122; eyes of sexes, *33 ; in- 
 ternal metamorphosis, 182 ; month 
 parts, *44 ; ocelli, ^2 : origin, 24 ; 
 sounds, 103 ; wing, *6i 
 
 Hypermetamorphosis, 174 
 
 Hyperparasitism, 311, 312 
 
 Hyphre, 259 
 
 Hyphantria, 298 
 
 Hypodcrma, larva of, *i62; Uncata. 
 habits of, 278 ; losses through, 394 
 
 Hypodermal colors. 194 
 
 Hypodermis, ^74, 75, *y6, *79 
 
 Hypognathous, 11 
 
 Hypopharynx, *i7, 39, *43 
 
 Icerya, 406 
 
 Ichneumonids, 310 
 
 Ihering, von, 419 
 
 Ileum,. *i2o 
 
 Imaginal buds, *i79, *i8o 
 
 Imago, 156 
 
 Incomplete metamorphosis, 157 
 
 Indirect metamorphosis, *is6 
 
 Ingenitzky, 438 
 
 Inheritance of acquired characters, 243 
 
 Injuries, transmission of, 241 
 
 Injurious insects, 393 ; introduction 
 
 of, 397 
 Ino, antennal sensilla of, *95 
 Inquilines, 256, 320 
 Insecta, defined, 4 
 Insectivorous birds, 284 ; fishes, 281 : 
 
 plants, 256 ; vertebrates, 280 
 Inspiration, 139 
 Instar, 159 
 Instinct, 356 ; apparent rationality of, 
 
 357: basis of, 357; flexibility, 360: 
 
 inflexibility, 359 ; modifications, 358 : 
 
 origin, 361; stimuli, 357; and tro- 
 
 pisms, 361 
 Integument, 73 
 Intelligence, 362 
 Interactions of organisms, 292 
 Intercalary, appendages, *iso ; neuro- 
 
 mere, *46 ; segment, 45 
 Interglacial beetles, 391 
 Interrelations, of insects, 307 : of 
 
 orders, 21 
 Intima, *85, *i2i, *i37 
 Iphiclidcs ajax, polymorphism of, 202 
 Iridescence, 193 
 Iris pigment, *i09, *iii 
 Iris "versicolor, *26o, *26i 
 Irritants, 298 
 
 Isaria, 258 
 
 Ischnoptera, moutli parts of, *37 
 
 Isia, cocoon of, 170; hairs, 76, 167; 
 
 moults, 165 
 Island faunae, 371 
 Isolation, 249, 374 
 Isoptera, 11 
 IsosODia, 31 1 
 Isotropic, 87 
 Ithomiina:, mimicry, 225, 226 
 
 Jacobi, 463 
 
 James, W., 459 
 
 Janet, on Lepisniina, *344 ; muscles, 
 86, *87; 416, 420. 421, 424, 45S 
 
 Japyx, 9, 22 ; spiracles of, 66 
 
 Jaworovski, 431 
 
 Jennings, 460 
 
 Judd, on food of bluebird, 287 : mim- 
 icry, 232 ; protective adaptations, 
 297 ; protective resemblance, 221 ; 
 warning coloration, 222; 451, 456 
 
 Jurassic insects, 385, 389 
 
 Kalliiua, protective resemblance of, 
 216 
 
 Kanthack, 456 
 
 Karsten, 421 
 
 Kathariner, 460 
 
 Katydid, stridulation of, 106 
 
 Kellogg, on Mallophaga, 277 ; mouth 
 parts, 42 ; phototropism, 354 ; pili- 
 fers, *42 ; scales, 78, 193; swarm- 
 ing, 327; 410, 414, 416, 417. 422. 
 448, 453, 460 
 
 Kenyon, 412, 425 
 
 Kidney tubes, 123, *i24 
 
 Kingsley, on Arthropoda, 7, 411, 412 
 
 Kirby, 410, 41 1 
 
 Kirkland, 456 
 
 Klemensiewicz, 422 
 
 Kluge, 438 
 
 Kniippel, 430 
 
 Koch, on malaria. 302 
 
 Kochi, 416 
 
 Koestler, 425 
 
 Kolbe, 410 
 
 Kolliker, 424, 437 
 
 Korotnel'f, 440 
 
 Korschelt, 438, 441, 444 
 
 Koschewnikoff, 438 
 
 Kowalevsky, 430, 432, 439, 443 
 
 Kraatz, 419 
 
 Kraepelin, 415, 418 
 
 Krancher, 435 
 
 Krause's membrane, *87, 88 
 
 Krukenberg, on chitin, 74 : 429, 447 
 
 Kulagin, 42, 416, 442, 444 
 
476 
 
 Labella, *43 
 
 Labial, neuromere, *46, 92, 152 ; seg- 
 ment, 45 
 Labium, 30, *3,7, *39. *43 
 Labrum, 30, 36, *Z7, *4^ 
 Lacaze-Duthiers, 418 
 Lachnosterna, antenna of, *34 ; cocoon, 
 
 169 : larva, *i62 
 Lacinia, *Z7, *38, 39 
 Lagoa. legs of, 55 ; stinging hairs, *8i 
 Lamarck, on instinct, 361 
 Lameere, 444 
 Lamellate, *34 
 Landois, 421, 426, 431, 432, 434, 437, 
 
 442, 446 
 Lang, 414 
 Langer, 416 
 
 Langley. on luminosity, 132 
 Lankester, 411, 413, 432 
 Larvce, 156 ; adaptations of, 165 ; legs, 
 55: nutrition, 166; parasitic, 314; 
 types, 162 
 Lasius, age of, 330 ; nest, 333 ; par- 
 thenogenesis, 145 
 Laveran, on malaria, 301 
 Leachia, eyes of, *3i 
 Leaping, 57 
 Le Baron, 404 
 Le Conte, 461 
 Lee, on halteres, 116, 427 
 Legs, adaptations of, 51, ^53 : larval, 
 55 : mechanics, *55, 56 ; muscles, 
 *S6 ; segments, *5i 
 Lendenfeld, von, 417, 424 
 Lens, *io9 
 
 Lepidocyrtus, scales of, ~y 
 Lepidoptera, defined, 17; internal 
 metamorphosis, *i82 ; moults. 165; 
 mouth parts, 41, ^42; origin, 24: 
 reproductive organs, *i4o, *i42 ; silk 
 glands, *84 ; spiracles, 66 
 Lepidotic acid, 196 
 Lepisma, *8, 9, 22, *i62: spiracles of, 
 
 66 
 Lepismina and ants. *344 
 Leptitiotarsa, color pattern of. 195, 
 208, *2i2; distribution, 379, 382; 
 dorsal wall, *i54 : entoderm, *i55 : 
 folding of wing, *62 : spread, 382, 
 398 : variation in coloration, *2i2 
 Leptocoris, 382 
 Lerenia, ocellus of, 32 
 Leuckart. 439 
 
 Leucocytes, *i25, 127, 131, 180 
 Leydig, 414. 421, 424, 425, 429. 431, 
 
 437. 438, 441 
 Libclliila. 13. *i5, *i62 
 
 Lice, biting, 12, *i3, 277 ; sucking, 16, 
 *i7, 277 
 
 Life zones, 376 
 
 Light, its effects on pigments, 197 
 
 Ligula, *39 
 
 Liinacodes. scale of, *77 
 
 Liua (see Mclasoma) 
 
 Linden, von, 449, 450 
 
 Lingua, *40 
 
 Linnaeus, on orders of insects, 8 
 
 Lintner, 403, 465 
 
 Lithomantis, 387, *388 
 
 Locality studies, 362, *363 
 
 Locustidse. 1 1 ; ovipositor, *69 ; sper- 
 matozoon, *i4i 
 
 Locy, 430 
 
 Loeb, on tropisms, 346, 347, 349, 351, 
 352, 356, 459. 460, 461 
 
 Loew, 436 
 
 Lomechusa, *342 
 
 Longitudinal muscles, *i2i 
 
 Losses through insects, 393 
 
 Low, on malaria, 303 
 
 Lowne, 414, 426, 427, 428. 438 
 
 Lubbock, on ants, 330, 331, 334, 336, 
 340, 341, 350 ; larval characters, 
 167; muscles, 86; vision. 113, 114; 
 411, 414, 423, 427, 428, 434, 437, 
 443. 453, 457, 459 
 Lncatuis. cocoon of. 169 : dorsal ves- 
 sel, *i25 ; spiracles, *i36 
 Lucilia, 349, 350 
 Lugger, 405 
 Luks, 424 
 Luminosity, 131 
 Lutz, 423 
 
 Lycariia. facets of. 32 
 Lycsenid larvre, alluring gland of, 83 
 Lycus. mimicked, 230, 231 
 Lyonet. on muscles, 86, 413, 423 
 
 Machilis.g, 22 : abdominal appendages, 
 
 *67 ; nervous system, *90 ; scales, 
 
 *77 : spiracles, 66 
 MacLeay. 416 
 Macloskie, 430, 435, 445 
 Madeira Ids., beetles of, 371 
 Maggot. *iS7 
 Malacopoda. defined, *3 
 Malaria, 299. *3oo 
 Male genitalia, *7i 
 Mallock, 428 
 
 Mallophaga, defined. 12. *i3: 277 
 Malpighian tubes. 123, *i24 
 Mandibles, *37 ; adaptations of, *38 ; 
 
 Culex. *43 ; Lepidoptera. *42 
 Mandibular, neuromere, *46, 92, 152;. 
 
 segment, 45 
 
477 
 
 Mandibulate mouth parts, 36 ; orders, 
 36 
 
 Mann, on Prionus, 161 
 
 Manson, on filariasis, 305 ; malaria, 302 
 
 Mantidse, 11, 307 
 
 Mautispa, 24 ; metamorphosis of, 
 *i63, 164 
 
 Maples, insects of, 252 
 
 Marey, on wing vibration, 63; 417 
 
 Marine insects, 190 
 
 Mark, 427 
 
 Marshall, on adaptive coloration, 230, 
 231. 451 
 
 Maternal provision, 314 
 
 Maturation, *i46 
 
 Maxillae, *37, *38 ; " second," 39 
 
 Maxillary, neuromere. *46, 92, 152; 
 segment, 45 
 
 Mayer, A. G., on color pattern, 211 ; 
 Papilio, 200 ; scales, 78 ; 423, 449, 
 451 
 
 Mayer, A. M., on Cnlcx, 107, 426 
 
 Mayer, P., 411, 426 
 
 May fly, male genitalia of, *7i ; wing, 
 *6i 
 
 McCook, on habits of ants, 332, 336, 
 339. 340, 457 
 
 Meconium, 172 
 
 Mecoptera, defined, *i7; origin, 24 
 
 Media, *S9 
 
 Median segment, 46, 66 
 
 Meek, 416 
 
 Megachile, hairs of. *75 
 
 Megalodacne, antenna of, *34 
 
 Mcgancura, 388 
 
 Megilla, 378 
 
 Meinert, 415 
 
 Melander, 458 
 
 Melanism, 201 
 
 Mclanoplus, alimentary tract of, *ii6; 
 facets, *3i ; genitalia, *73 ; mandi- 
 ble, *38 ; respiration, 139; skull, *29 
 
 Melanotus, larva of, *i62 
 
 Melasoma, color changes of, 215 ; dis- 
 tribution, 378; germ band, *i49 ; 
 glands, 82 
 
 Meldola, 450 
 
 Melnikow, 439 
 
 Meloe, antenna of, 35 ; hypermetamor- 
 phosis, 174 
 
 Melolontha, male reproductive system, 
 *i4o; olfactory pits, loi 
 
 Menopon, 12, *i3 
 
 Mentum, *37, *3g 
 
 Merkel, 423 
 
 Meron, 51, *52 
 
 Merriam, on life zones, 376 ; 462, 463 
 
 Merrifield, 447, 448 
 
 Mesenchyme, *i55 
 
 Mesenteron, *ii5, *ii6, *ii7, *ii8, 
 155 
 
 Mesoderm, 148, *iS4 
 
 Meso-entoderm, *i48 
 
 Mesothorax, 46 
 
 Metabola, 159 
 
 Metamorphosis, defined, 156; external, 
 156; internal, 179; kinds, 23; sig- 
 nificance, 177; systematic value, 23 
 
 Metatarsus, *27o 
 
 Mctathorax, 46 
 
 Metcalf, 453 
 
 Metschnikoff, 430, 439, 443 
 
 Meyer, G. H., 439 
 
 Meyer, H., 432 
 
 Miall, on chitin, 74 ; muscles, 87 ; 410, 
 412, 414, 424, 436. 444. 445, 446 
 
 Miastor, paedogenesis of, *I4S 
 
 Michels, 425 
 
 Microcentnim, stridulation of, 104, 
 *io5 
 
 Microptcryx, mouth parts of, 42 
 
 Micropyle, 147, 160 
 
 Mid intestine, *ii7, *ii9 
 
 Milkweed, pollination of, *262 
 
 Mimicry, 224 ; evolution of, 233 
 
 Minot, 414, 422 
 
 Miocene insects, 385, 390 
 
 Moisture, its effects on coloration, 199 
 
 Molanna, 17, *i8 
 
 Moles, insectivorous, 280 
 
 Moller, on leaf-cutting ants, 338, 454 
 
 Mollock, on vision, 113 
 
 Moniez, 445 
 
 Moniliform, *34 
 
 Mononychus, 268 
 
 Mordella, facets of, 32 
 
 Morgan, C. Lloyd, on food of birds, 
 232 ; 452, 453, 459, 460 
 
 Morgan, T. H., 453, 460 
 
 Morpho, scales of, 78, 193 
 
 Moseley, 431 
 
 Mosquito, antenna of, 35, *36 ; hear- 
 ing, 107; locomotion of larvae, 187; 
 in relation to malaria, 299 ; mouth 
 parts, *43 : respiration, *i88, 189 
 
 Moulting, 164 
 
 Moults, number of, 165 
 
 Mouth parts, dipterous, 42, *43 ; 
 hemipterous, 40, *4i ; hymenopte- 
 rous, *44 ; lepidopterous, 41, *42 : 
 mandibulate, 36, *37 ; orthopterous, 
 *37 ; suctorial, 40 
 
 Miiller, F., on mimicry, 227 ; wings, 
 57 ; 411, 421, 442, 450 
 
 Miiller, H., 453 
 
 Miillerian mimicry, 226, 227 
 
478 
 
 Miiller, J., "mosaic" theory of, iii, 
 
 42s 
 Murgantia, spread of, 382 
 Murray, 461 
 Musca, egg of, *i59 ; facets of, 32; 
 
 fungus of, *258 ; moults, 165 ; ovum, 
 
 *i46; in relation to typhoid fever, 
 
 305 
 Muscidse, cardiac valve of, *w): ima- 
 
 ginal buds of, *i79, 181 
 Muscles, circular and longitudinal, 
 
 *i2i : of cockroach, *s6, *86 : of leg, 
 
 *55. *S6 ; number, 85 ; structure, 
 
 ♦87 : of wing, 64, *65 
 Muscular, power, 88: system, 8s 
 Mutation theory, 247 ; versus natural 
 
 selection, 249 
 Mutilla, stridulation of, 104 
 Myriopoda, the term, 5 
 Myrmecocystus, *337 
 Myrmecodia, 27^ 
 Myrmecophana. mimicry by, *229 
 Myrmecophilism, 340 
 Myrmcdonia. 343 
 Myniideon, digestive system of. *ii8 ; 
 
 predaceous, 308 ; silk glands, 85 
 Myrmica, *343 
 Mystacidcs. androconia of, 80 
 
 Nagel, 428 
 
 Nassonow, 438 
 
 Natural selection, 238 
 
 Nearctic realm, 375 
 
 Necrophonts, 280, 314 
 
 Needham, on digestion, 119; venation, 
 
 58; 417, 431, 446, 455 
 Ncmobiiis, leg of, *53 
 Neotropical realm, 375 
 Ncpa, respiration of, 189 
 Nerves, of head, *9i ; structure, *93 
 Nervous system, 89 ; development of, 
 
 151, *i54, *iS5 
 Nervures, 58 
 
 Neuration, 58, *S9, *6o, *6i 
 Neurilemma, *93 
 Neuroblasts, *i54 
 Neuromeres, defined, 45. 152: of head, 
 
 ♦46, 90 
 Neuroptera, defined, 16; metamor- 
 phosis of, 24, *i63 
 Newbigin, 449, 451 
 Newport, on metamorphosis, 183 ; 
 
 muscles, 86; 414, 423, 424, 431, 
 
 433, 434 
 Newton, 425 
 
 Notolophus, olfactory organs of, 102 
 Notonecta, *i85 ; locomotion of, *i86; 
 
 respiration, 189 
 
 Notum, 47 
 
 Novius. 314, 395. 406 
 Nucleolus. 146 
 Number of insects, 27 
 Nusbaum, 437, 441 
 Nuttall, 456 
 Nymph, 159 
 
 Oaks, insects of, 252 
 
 Oberca. eyes of, 31 
 
 Obtect pupa, 167, *i68 
 
 Occipital foramen, *30 
 
 Occiput, 30 
 
 Ocelli, *32 ; structure of, *i09 ; vision 
 by, 109 
 
 Ockler, 417 
 
 Ocular, neuromere, *46 ; segment, 45 
 
 Odonata, abdominal segments of, 66 ; 
 copulation of, 71; defined, 13; 
 ocelli, 32 ; origin, 23 ; spiracles. 66 
 
 Odors, 82 ; efficiency of, 298 
 
 Odynents, 268 
 
 GLcanthus, abdominal appendages of, 
 67, *iS2; embryo, *i52; stridula- 
 tion, 105 
 
 CEcodoiiia. 337 
 
 CEcophylla, 333 
 
 CEdipoda, dorsal vessel of, *i25 
 
 CEneis, distribution of, 370 
 
 CEnocytes, *i3i 
 
 CEsophageal commissures, *gi 
 
 CEsophagus, *i 17 
 
 CEstridje, 278 
 
 Olfactory organs, 98, *99, *ioo, *ioi 
 
 Oligocene insects, 385, 389 
 
 OUgotouia, *i2 
 
 Ommatidium, no, *ii2 
 
 Onthophagus, mandible of, *38 
 
 OrchcUmnin, stridulation of, 105, 106 
 
 Orders of insects, 8, 21, *25 
 
 Orgyia, olfactory organs of, 102 ; para- 
 sites of, 312 
 
 Oriental realm, 376 
 
 Origin of Arthropods, *7 ; of insects, 6 
 
 Orthoptera, abdominal segments of, 
 66 : defined, *io ; origin, 22 ; stridu- 
 lation, 104, *io5, 106 
 
 Osborn, 453 
 
 Osmeterium, *82 
 
 Osinia. 268 
 
 Osiiwdcnua. cocoon of, 169 
 
 Osten-Sacken, 422 
 
 Ostium, *i25 
 
 Oudemans, 438 
 
 Oustalet, 434, 445 
 
 Ovaries, 140, *i4i, *i42 
 
 Ovariole, *i43 
 
 Oviducts, 140, *i4i, *i42 
 
479 
 
 Ovipositor, *69, *7o, *7i 
 Ovogenesis, 146 
 
 Ovum, of Mitsca, *i46: I'ancssa. *i44 
 Ox-warble, *i62, 278, 394 
 
 Paasch, 426 
 
 Packard, on Anophthalmus. 114: Ar- 
 thropoda, 7 ; classification, 9 : Man- 
 tissa. 24, 164; olfactory pits, loi ; 
 origin of Coleoptera, 24 ; relation- 
 ships of orders, 23, 24 ; segmenta- 
 tion, 28 ; types of larvae, 162 ; wings, 
 57 ; 402, 405 ; 410, 411, 413, 414, 
 418, 419. 4-'-^ 4-'3. 4-'5. 4-28. 434. 
 435. 440. 443. 444. 45 1 . 462, 465 
 
 P.-edogenesis, 145 
 
 Pagenstecher, 437 
 
 Palrearctic realm, 375 
 
 Polccohlattina. *38s 
 
 Pal?eodictyoptera, 392 
 
 Palmen, 435, 437 
 
 Palmer, 456 
 
 Palpifer, *Z7~ *38, 39 
 
 Palpiger. *t,7, *39 
 
 Palpus, *37, *38, *39, *42, *43, *44 
 
 Pankrath, 428 
 
 Panorpidse, *i7; legs of, 55 
 
 Papilio, colors of, 200; egg, *i59; 
 facets, 32; head of pupa, *i68 : 
 melanism, 201 : mimicry, 226, 228 ; 
 osmeterium, *82 ; protective resem- 
 blance, 218 ; merope. mimicry by, 
 226, 228 ; sexual coloration of. 206 
 
 Paraglossa, *37, *39 
 
 Paraponyx, *i3S, 190 
 
 Paraptera, 48 
 
 Parasita, defined, 16, *\y 
 
 Parasitic insects, lyy, 309, 314: in 
 relation to birds, 291 
 
 Parasitism, 278, 309 ; economic im- 
 portance of, 312 
 
 Parker, on phototropism, 353, 460 
 
 Parthenogenesis, 145, 256, ^27, 331 
 
 Passalus, cocoon of, 169 ; stridulation, 
 104 
 
 Patagia, 48 
 
 Patten, 42^, 428, 440 
 
 Pawlovi, 425 
 
 Pawlowa, 432 
 
 Peckham, on behavior, 360, 362, 364, 
 458, 460 
 
 Pectinate, *34 
 
 Pedicel, *34 
 
 Pediculidse, 2yy 
 
 Pediculus, 16, *i7, 277 
 
 Pelocoris, leg of. *53 
 
 Penis. *7i, *72, 142 
 
 Pcpsis. 315 
 
 Perez, C, 444 
 
 Perez, J., 420 
 
 Pericardial chamber, *i25, 126, *i39 
 
 Pcripatiis. characters of, *3 ; syste- 
 matic position. 5 
 
 Pcriplaneta, olfactory pits of, loi 
 
 Peripodal, cavity. 181 ; membrane. 
 181 ; sac, 181 
 
 Pcrla. olfactory pits of, loi 
 
 Perlidac, 12, 13, *i4; nymph, *i62; 
 tracheal gills, 135 
 
 Permian insects, 388 
 
 Petiolata, 21 
 
 Pettigrew, 417 
 
 Petunia. *26G, 267 
 
 Peytoureau, 420, 438 
 
 Phagocytes, 131, 180 
 
 Phancciis, legs of, 52, *S3 
 
 Pharynx, 117 
 
 Phasmidae, 11, *2i7 
 
 Plilegethontiiis, head of moth, *42 ; 
 larva, *54 ; moth, *266 ; parasitized 
 larva, 311 
 
 Pliorniia, antenna of, *34 : eyes, *22 ; 
 metamorphosis, *i57; phototropism, 
 354 
 
 PJwrodon, multiplication of, 238 
 
 Phosphorescence, 131 
 
 Photinns . luminosity of, 131, 132 
 
 Photogenic plate, 131 
 
 Photopathy, 350, 351 
 
 Photophil. 351 
 
 Photophob. 351 
 
 Phototaxis. 350. 351 
 
 Phototropism, *349 
 
 Phragmas. *5o 
 
 Phthirias, 277 
 
 Phyciodes, coloration of, 199, *203, 
 204 
 
 Phylloxera, 393. 397 
 
 Phylogeny, 5. *7, 21, *25, 391 
 
 Physopoda, 13, *i5 ; origin of, 2t,. * 2$ 
 
 Phytonomus, legs of, 55 ; spread of, 
 381 
 
 Phytophaga, 20, *2i 
 
 Pictet, on coloration, ig6, 200 
 
 Piepers, 451 
 
 Pieris. color sense of, 115 : dispersion, 
 366: fat-cells, *i3o; imaginal buds, 
 *i8o; olfactory organs, *ioi : scale, 
 *77 ; napi, temperature experiments 
 on, 204 ; protodice, sexual coloration 
 of, *2o6 ; rapce, androconium of, 
 *79 ; developing wing, *i8i ; distri- 
 bution, 381 ; eggs, *i6o ; food plants, 
 253 ; hair, *76 ; larval tissues, *i2g ; 
 pupal coloration, 198 : wing vibra- 
 
48o 
 
 tion, 64 : xanthodice, distribution of, 
 
 366 
 Pigmental colors, 194 
 Pigments, of eyes, *iio, *iii, *ii2, 
 
 *ii3; nature of, 195; of Pieridee, 
 
 196 
 Pilifers, *42 
 Pimpla, 312 
 Pine, insects of, 252 
 Pingnicula/2Z7 
 Placodeum, *9S 
 Planta, *27o 
 Plants, insectivorous, 256 ; insects in 
 
 relation to, 252 
 Plasma, 127 
 Plasmodium, *30o, 301 
 Plateau, on color sense, 115; muscu- 
 lar power, 88; respiration, 139; 
 
 416, 423, 427, 429, 432, 435, 459 
 Platephemera, *386 
 Plathemis, abdominal appendages of, 
 
 *72 ; antenna, *34 
 Platner, 434 
 Platygaster, hypermetamorphosis of, 
 
 167, *i76 
 Platypsyllus, 278 
 Platyptera, defined, 11, *i2; origin of, 
 
 23, *25 
 Plecoptera, defined, 13, *i4; nymph, 
 
 *i62 ; origin, 23, *2S 
 Pleistocene insects, 385, 391 
 Pleurites, 48, *49 
 Pleuron, 47 
 Plotnikow, 423 
 Pocock, 412 
 Podical plate, *73 
 
 Podisus, egg of, *iS9 ; predaceous, *307 
 PoecilocapS'us, color changes of, 215 
 Pogonotnyrmcx, 340 
 Polar bodies, ^146 
 Poletajeff, N., 424 
 Poletajew, O., 435, 445 
 Poletajewa, 432 
 Polistes, behavior of, 360, 365 ; habi*s, 
 
 329 ; wing vibration, *64 
 Polites, on Iris, *267 
 Pollenizers, insect, 266 
 Pollination, 259, 266 ; of Iris, *26o, 
 
 *26i ; milkweed, *262 ; orchids, 262 ; 
 
 Yucca, *264 
 Pollinia, *262 
 Polybia, 328 
 Polyergus, 336 
 Polygoneutic, 204 
 Polygonia, dimorphism of, 202 ; egg, 
 
 *i59 
 Polymorphism, 202, 330 
 Polynema, 177 
 
 Polyphemus (see Telea) 
 
 Polyphylla, assembling of, 103 
 
 Polyrhachis, 333 
 
 Pompilus, behavior of, 360, 364 
 
 Porthctria dispar, damage by, 397 ; 
 hermaphroditism, *i44 : tracheae, 
 *i38 
 
 Post-gense, 30 
 
 Postscutellum, *48 
 
 Potato beetle (see Leptinotarsa) 
 
 Pouchet, 434, 459 
 
 Poulton, on adaptive coloration, 230, 
 231, 234; on colors of larvae and 
 pups, 197, 198; 444, 447, 448, 449, 
 450, 4SI 
 
 Powell, 444 
 
 Pratt, 444 
 
 Predaceous insects, 276, *307 ; in rela- 
 tion to birds, 291 
 
 Premandibular, appendages, *i5o; seg- 
 ment, 45 
 
 Primitive insects, 21, 22 
 
 Primitive streak, 148 
 
 Primordial insect, 21 
 
 Prionus. assembling of, 103 ; eggs, 161 
 
 Proljoscis, *42 
 
 Procephalic lobes, *i49, *i50, *iS2 
 
 Proctodaeum, 117, *i20, *i49 
 
 Proctotrypidje, 27, 311 
 
 Prodoxns, 266 
 
 Prodryas, *390 
 
 Prognathous, 1 1 
 
 Promcthca (see Callosamia) 
 
 Pronotum, *48 
 
 Pronuba, ^264, ^265 
 
 Propodeum, 46, 66 
 
 Propolis, 323 
 
 Protective, adaptations, 297 ; mimicry, 
 *224, 233 ; resemblance, *2i6, 220 
 
 Prothorax, 46 
 
 Protocerebrum, 90, 152 
 
 Protoplasm, adaptive, 243 
 
 Proventriculus, 118 
 
 Pseudocone, *ii2 
 
 Pseudomyrma, 273 
 
 Psocidae, *i2 
 
 Pteronarcys, 13, *i4; tracheal gills of, 
 13s 
 
 Pterygota, 10 
 
 Ptilodactyla, antenna of, *34 
 
 Pulvillus, 51, *54 
 
 Punktsubstanz, *93 
 
 Pupae, 156, 167; emergence of, 171; 
 protection, 169 ; respiration, 169 
 
 Pupal stage, significance of, 177, 183 
 
 Puparium, 168 
 
 Pupation of a caterpillar, 168 
 
 Putnam, on habits of Bombus, 328 
 
48 1 
 
 Pyloric valve, 120 
 Pyrophila, thigmotropism of, 347 
 Pyroplwnis. luminosity of, 131 
 Pyrrharctia (see Isia) 
 
 Quaternary insects, 391 
 Qucdiiis. 343 
 
 Queen, honey bee, *32i, 322; termite, 
 *3i7 
 
 Radius, *59 
 
 Radl, 460 
 
 Radoszkowski, 419 
 
 Ranatra, 185 ; respiration of, 189 
 
 Ranke, 426 
 
 Raschke, 435 
 
 Rath, von, on sense hairs, *ioi, 428 
 
 Rathke, 434, 439 
 
 Rationality, apparent, 357 ; lack of, 
 
 36s • 
 Realms, faunal, 374 
 Reaumur, de, 413 
 Receptaculum seminis, *i4i, *i42 
 Recognition markings. 235 
 Rectal respiration, 135, 190 
 Rectum, 120 
 
 Recurrent nerve, *9i, *92 
 Redikorzew, on ocelli, *i09, 428 
 Redtenbacher, 417 
 Reed, on yellow fever, 304 
 Rees, van, 443 
 
 Reichenbach, on ants, 145, 331 
 Reid, 453 
 Reinhard, 434 
 Relationships, of arthropods, s, *7 ; of 
 
 orders, 21, *2S 
 Repellent glands, 81 
 Replacements, 214 
 Reproductive system, 140 
 Respiration, 137, 169 
 Respiratory system, *i33 
 Retina, *i09 
 
 Retinula, 109, *iio, iii, *ii2 
 Reuter, 428 
 
 Rhabdom, 109, *iio, iii, *ii2 
 Rheotropism, 347 
 Rhipiplwnis, 174, 176 
 Rhopalocera. 18 
 Rhyphus. *6o 
 Riley, on hypermetamorphoses, 174; 
 
 losses through insects, 393, 394 ; 
 
 multiplication of hop aphid, 238 ; 
 
 pollination of Yucca, 264 ; pupation, 
 
 168; 404, 405. 406; 443, 454 
 Ritter, 438, 441 
 Robertson, 454 
 Robin, food of, 284 
 
 32 
 
 Rocky Mountain locust ; dispersion of, 
 
 366 ; as food of birds, 288 
 Rollet, 424 
 Romanes, on instinct, 361 ; isolation, 
 
 249, 250, 251 ; 452, 459 
 Ross, on malaria, 302, 303, 456 
 Rossig, 455 
 
 Rostrimi, 40 
 Roaitcs. *339 
 Ruland, 428 
 
 Sadones, 436, 446 
 
 Saliva of Dytiscus. 123 ; mosquito, 123 
 
 Salivary glands, 121, *i22, *i23 
 
 Sambon, on malaria, 303 
 
 Saiiiia cecropia, antennae of, *3S ; 
 cocoon, *i7o ; egg, 160 ; food plants, 
 253; genitalia, *72 ; head of larva, 
 *84 ; Malpighian tubes, *i24; ocelli, 
 *T,2 : odor, 82 ; scales, *78 
 
 Sanderson, 466 
 
 Sandias. 458 
 
 San Jose scale, 397 
 
 Sanninoidea, sexual coloration of, 206 
 
 Sarcolemma, *87 
 
 Sarcophaga, nervous system of, *gi 
 
 Saturnia, hairs of, *y6 
 
 Saunders, E., 421 
 
 Saunders, \V., 407, 465 
 
 Saville-Kent, 463 
 
 Scales, arrangement of, *78 ; develop- 
 ment, 78, *79 ; form, *7-, 78 : occur- 
 rence, 77 ; uses. 79 
 
 Scape, *34 
 
 Scarabseidoid larva, 175 
 
 Scavenger insects, 279 
 
 Schaffer, on scales, 78 ; 414, 422, 432. 
 433 
 
 Schaum, 415, 418 
 
 Scheiber, 431. 434 
 
 Schenk. on sensilla, 94, *95, 102, 429 
 
 Schewiakoff, 424 
 
 Schiemenz, 430 
 
 Schimper, 454 
 
 Schindler, 429 
 
 Schistocerca, distribution of, 367, 383 ; 
 of Galapagos ids., 371 : isolation, 
 
 250, 374 
 Schiaoneura. wax of, 83 
 
 Schiziira, protective resemblance of, 
 
 *2I9 
 
 Schmankewitsch. on Artcmia, 243 
 Schmidt, O., 426 
 Schmidt, P., 412, 433 
 Schmidt-Schwedt, 435 
 Schneider, A., 430, 437, 440 
 Schneider, R., 422 
 Schultze, 426, 433 
 
482 
 
 Schwarz, on distribution, 378, 380 ; 
 
 myrmecophilism, 343 : 462 
 Schwedt, 445 
 Sclerite, 29 
 Scolopendra, *4 
 ScolopendreUa, *6, 22 
 Scudder, on albinism, 201 ; coloration. 
 
 210; fossil insects, 385, 386, 390, 
 
 391, 392 ; glaciation, 370 ; mimicry, 
 
 227 ; Orthoptera of Galapagos Ids., 
 
 371, 374; spread of P. rapcc, 3S1 ; 
 
 stridulation, 106; 409, 418, 421, 
 
 422. 426, 446, 462, 464. 465 
 Scutellum, *48 
 Scutum, *48 
 Seasonal coloration, 201 
 Second maxillae, the term, 39 
 Sedgwick. 412 
 Segmentation, of arthropods, 27 ; germ 
 
 band, *i49, *iSo, *i52: head. 44, 
 
 *46 
 Segments of abdomen, 65, 66 
 Seitz, 447, 454, 458, 459, 462 
 Sematic colors, 234 
 Seminal, ducts, *i40, 141 ; receptacle, 
 
 *i4i, *i42; vesicle, *I40, 142 
 Semon, 463 
 
 Semper, C, on scales, 78. 421 
 Semper, K., 461 
 Sempers, 465 
 Sense organs, 94 
 Sensilla, 94, *95 
 Serosa, *i48, 149, *i53 
 Sessiliventres, 20, *2\ 
 Setaceous, ^34 
 Setje, modifications of. 76 
 Seventeen-year locust, number of 
 
 moults, 165 
 Sexual coloration, 205 
 Sharp, on Atta, 335 ; Hawaiian beetles, 
 
 372; metamorphosis, 177: 410, 412. 
 
 419, 435, 445 
 Sheath. *7o 
 Shelford, 451 
 Siebold, von, 426, 436 
 Silk, 8s 
 
 Silk glands, 83, *84, *85 
 Silkworm (see Bomhyx mori) 
 Silpha, distribution of, 379 
 Silurian insects, *385 
 Silvestri, on Anajapy.v , *6 
 Simmermacher, 422 
 Siinnliinn, 276 ; respiration, *i90 
 Sinclair, 412 
 Siphonaptera, 19. *2i : origin of, 24. 
 
 *25 
 Sirex, ovipositor of, *70 
 Sirodot, 421, 429 
 
 Sitaris. 174 
 
 Size of insects, 27 
 
 Skin, 73 
 
 Skull, *29 
 
 Skunk, insectivorous, 280 
 
 Slingerland, on losses through insects, 
 
 394; 403, 405 
 Smell, 98; end-organs of, *99. *ioo, 
 
 *IOI 
 
 Siuiufluirus, *9, 10 
 
 Smith. J. B., 405, 415, 416, 465 
 
 Smith, T., on Texas fever, 306 
 
 Snodgrass, on Orthoptera of Galapa- 
 gos Ids., 371, 374 
 
 Snow flea, *9 
 
 Soldier, ants, 330 ; termites, *3i6 
 
 Sollmann, 418 
 
 Somatic cells, 146 
 
 Somatogenic variations, 241 
 
 Sorensen, 413 
 
 Sounds, 103 
 
 Species, origin of, 245 
 
 Spence, 410, 411 
 
 Spencer, 452 
 
 Spermatheca. *i4i. *i42 
 
 Spermatogenesis, 146 
 
 Spermatophores, 142 
 
 Spermatozoa. *i4i, 142 
 
 Sperm-nucleus, *i46 
 
 Speyer, on hermaphroditism, 143 
 
 Sphecina, 315 
 
 Sphecius, 315 
 
 Sphex, *263 ; behavior of, 359. 362, 
 *363 
 
 Sphingidse. as pollenizers, 262, *266 
 
 Sphinx, alimentary tract of, *ii9 : dis- 
 persal, 367 ; pulsations of heart, 
 128; transformation, *i82 
 
 Spichardt. 437 
 
 Spines, 76 
 
 Spinneret, *84 
 
 Spiracles, closure of, *i36; number, 
 66, 136 
 
 Spirobolus, *3, 4 
 
 Spongioplasm, 87 
 
 Sporotrichum, 259 
 
 Spuler, on scales, 78; 417, 423, 448 
 
 Spur, *S3 
 
 Squama, 58 
 
 Squash bug. metamorphosis of, *i58 
 
 Stadium, 159 
 
 Staginoiiiaiitis, leg of, *S3 
 
 Standfuss, temperature experiments 
 of, 205. 373 ; 448 
 
 Stefanowska, on pigment, 113, 428 
 
 Stegoniyia. in relation to yellow fever, 
 304 
 
 Stein, 436 
 
483 
 
 of, 
 
 456, 
 
 Stcnaiiinia, 334 
 
 Steitobothnis. blood corpuscles 
 
 *I25 ; stridulation of. 104 
 Sternberg, on malaria. 30J. 303 ; 
 
 45- 
 Sternum, *47, 48, *49, 66 
 Stigmata (see Spiracles) 
 Sting of honey bee, *70 
 Stinging hairs, *8i 
 Stings, efficiency of. 298 
 Stipes. *^7, *38, 39 
 Stokes, 436 
 Stomach, *ii9 
 Stomachic ganglion, *g2 
 Stomatogastric nerve, *g2 
 StomodKum, *ii6, *ii7, *i49 
 Straton, 454 
 Straus-Diirckheim, on muscles. 
 
 413. 4^3 
 Strength, muscular. 88 
 Stridulation. 104, *io5, 106 
 Strongylonotus. 336 
 Structural colors, 193 
 Struggle for existence, 239 
 Styloconicum. 94. *95 
 Stylops. hypermetamorphosis of, i 
 Subcosta, *5g 
 Subgalea, *38 
 Submentum, *^7, *3g 
 Suboesophageal ganglion, *90, *9i 
 Suctorial mouth parts, 40 
 Suffusion, 199 
 Superlingure, *4o. 150. *i5i 
 Superlingual, neuromere, *46, 92, 
 
 segment, 45 
 Supranesophageal ganglion, *90, 
 
 93 
 Suranal plate, 68, *73 
 Surface film. 187 
 Suspensor. *i43 
 Suspensory muscles. *i25 
 Swarming, 327 
 Symbiosis, 343 
 
 Sympathetic system, *9o, *gi, *g. 
 Synaptera, 10 
 
 Syrphidse, silk glands of, 85 
 Systole, 128 
 
 Tabanidae, 276 
 
 Tabaniis, nervous system, *9i ; olfac- 
 tory organ, *ioo 
 
 Tactile hairs, 76, *94, *95, 96 
 
 Tfenidia, *I37 
 
 Tarsus, *49, *5i, *S3 
 
 Taschenberg, 409 
 
 Taste. 96 ; end-organs of, *97, *98, 
 *99 
 
 Taxis, 345 
 
 Tegmina, 58 
 
 TeguL-e, 48 
 
 Tclca polyf^hciuiis. cocoon of, 170; 
 eclosion, 172; larval growth, 164; 
 silk glands, 84; spinning, 170 
 
 Teleas, 177 
 
 Temperature, its effects on coloration, 
 199 
 
 Tenent hairs, *8o 
 
 Tenthredinid;e. 25 ; larval legs of, 55 
 
 TctUhrcdopsis. larva of, *i62 
 
 Tentorium, *3o 
 
 Terebrantia, 20, *2i 
 
 Tergites, *48 
 
 Tergum, 47, 66 
 
 Tcnnes fiavipes. 318: liicifugiis. *3i6, 
 317. 318 : obesus, *3i7 
 
 Termites, American species of, 318; 
 architecture, *3i9, *320 ; classes, 
 *3i6: "compass," 319, *32o ; food, 
 318: mandibles, *38 : origin of 
 castes. 318: (|ueen, *3i7; ravages, 
 320 _ 
 
 Termitidpe. 11, 12 
 
 Termitophilism, 321 
 
 Teniwpsis, 318 
 
 Tertiary insects. 385, 389 
 
 Testes, *i40, 141 
 
 Texas fever, 306 
 
 Thalessa, *3io 
 
 Thanaos, androconia of, 80 ; claspers, 
 
 Thaxter, on Eiupiisa, *258. 259, 454 
 
 Thelen, 434 
 
 Theobald, 465 
 
 Thermotropism, 355 
 
 Thigmotropism, 346 
 
 Thomas, C, 404, 405 
 
 Thomas, M. B., on androconia, 80, 422 
 
 Thorax, differentiation of, 47 ; parts, 
 
 46 : sclerites, *47, *48 
 Thread-press, *84, 85 
 Thyridoptcryx, number of eggs of. 161 
 Thysanoptera. 13, *i5 : origin of. 23, 
 
 *25 
 
 Thysanura, *8, 9 : abdominal seg- 
 ments, 66 ; primitive, 21 
 
 Thysanuriform, 24, *i62, 178 
 
 Tibia, *49, *5i, *Si 
 
 Tipitia, 19, *20 
 
 Titanophasma, 27 
 
 Toad, insectivorous, 280 
 
 Tongue, 39 
 
 Touch, 96 
 
 Tower, on color patterns. 208 : cuticu- 
 lar colors, 194: distribution of Lep- 
 tiiwtarsa. 379; folding of wing, 61, 
 *62 ; integument, *74 ; origin of 
 
484 
 
 INDEX 
 
 wings, 57: structural colors, 194; 
 
 423, 449, 463 
 Toyama, 438 
 Tracheae, development of, 153, *iS5 ; 
 
 distribution, *i32, *i33: structure, 
 
 *i37 
 Tracheal gills, *i34, *i3S, 190 
 Tracheation, types of, 134 
 Trelease, 454 
 Treuicx, *2i 
 Triassic insects, 388 
 Trichius, 268 
 Trichodeum, 94, *95 
 Trichograiniua, 313 
 Trichoptera, 17, *i8 ; origin of, 24, 
 
 *25 : silk glands, 85 
 Trichopterygidffi, size of, 27, 311 
 Trimen, on dispersal, 367 ; on P. 
 
 inerope. 226, 228: 450, 451 
 Trimerotropis, protective resemblance 
 
 of, 219 
 Trimorphism, 202 
 Triphleps, egg of, *i59 
 Tritocerebrum, 91, 152 
 Triungulin, 174, *I75 
 Trochanter, *49, *si, *S2, *S3 
 Trochantine, 51 
 Tropcra luna, cocoon of, 170 
 Tropical region, 2i77 
 Tropisms, 345 
 Trouessart, 462 
 Trouvelot, on cocoon-spinning, 170; 
 
 eclosion, 172; larval growth, 164: 
 
 442 
 Tryphcrna, 197 
 Tsetse fly, 276 
 Tutt, 463 
 Typhoid fever, 305 
 
 Uhler, on distribution, 380 
 
 Urech, 447, 448, 449 
 
 Uric acid, 124; as a pigment, 196 
 
 Utricularia, 257 
 
 Uzel, 442 
 
 Vagina, 140, *i4i, *i42 
 
 Valette St. George, la, 437 
 
 Vanessa, development of scales of, 
 *79 ; head of butterfly, *42 ; antiopa, 
 298 ; phototropism, 353 ; atalanta, 
 color change, 214 ; car did, disper- 
 sion, 366, 371 ; geographical varia- 
 tion, 373 ; polychloros, coloration, 
 200 ; melanism, 201 ; urticw. colora- 
 tion, 196, 200 ; melanism, 201 ; tem- 
 perature experiments, 205 
 
 Variation in coloration, 211, *2i2, 
 
 *2I3 
 
 Variations, blastogenic, 243 ; classes 
 of, 214, 241; congenital, 243; en- 
 vironmental, 242 ; functional, 242 
 
 Vas deferens, *i40, 141 
 
 Vayssiere, 432, 435, 445 
 
 Vedalia (see Novins) 
 
 Veins, 58 
 
 Velum, *27o 
 
 Venation, 58, *S9, *6o, *6i 
 
 Ventral sinus, 126, * 139 
 
 Ventral tube, *68 
 
 Ventriculus, *ii8 
 
 Verhoeff, 418, 420, 458 
 
 Verloren, 431 
 
 Vernon, 450, 453 
 
 Verson, 438 
 
 Vertex, 30 
 
 Verworn, on phototropism. 351 ; 460 
 
 Vespa, nests of, 328, ^329 ; olfactory 
 organ, *ioo ; sensillum, *9S ; taste 
 cups, *98 : tongue, *97 
 
 Vespidje, 328 
 
 Viallanes, 414, 425, 432, 435, 443 
 
 Vision, 108 
 
 Vitelline membrane, *i46 
 
 Vitreous body, *io9 
 
 Voeltzkow, 441 
 
 Vogler, 435 
 
 Volucella, mimicry by, *235 ; preda- 
 ceous, 309 
 
 Voss, 418 
 
 Vries, de, mutation theory of, 247, 453 
 
 Wagner, J., 412 
 
 Wagner, N., 437 
 
 Wahl, 444 
 
 Walker, 445 
 
 Walking, 56 
 
 Wallace, on mimicry, 226 ; natural se- 
 lection, 238: 450, 452, 461, 462 
 
 Walsh, on losses through insects, 
 394 : 403 
 
 Walter, on mouth parts, 42, 415 
 
 Walton, on meron, 51, 417 
 
 Warning coloration, 221 
 
 Wasmann, on myrmecophilism, 340 ; 
 458, 460, 461 
 
 Wasps, 328 
 
 Watase, 428 
 
 Wax, glands, 83 ; pincers, *27o, 271 
 
 Webster, on dispersal, 368, 378, 381, 
 382 ; losses through insects, 394 ; 
 405 ; 451, 454, 457, 462, 463 
 
 Wedde, 415 
 
 Weed, on birds in relation to insects, 
 286. 287, 289, 291, 456 
 
 Weinland, 428 
 
 Weismann, on acquired characters. 
 
485 
 
 243 : conRcnital variations, 243 : 
 imaginal buds, 180: instinct, 361; 
 somatogenic variations, 241 ; tem- 
 perature experiments, 204 ; use and 
 disuse, 242 ; 422, 439, 442, 446, 448, 
 449, 451, 452, 453, 460 
 
 West, T., 416 
 
 Westwood, on Drachimts, 82; 410. 
 411 
 
 Wheeler, on harvesting ants, 340 ; 
 Malpighian tubes, 123 ; tropisms, 
 345, 346, 348, 349, 355 ; 4i9, 43o. 
 433, 441. 458. 459. 460 
 
 White, F. B., 418, 445 
 
 White grubs, 398 
 
 Whitman, 460 
 
 Whymper, on distribution, 366, 462 
 
 Wielowiejski, von, 432, 433, 438. 443 
 
 Wilcox, 439, 455 
 
 Wilde. 429 
 
 Will, F., on taste, 96, 427 
 
 Will, L., 437, 440 
 
 Williams, 434, 445 
 
 Wilson, 442 
 
 Wings, 57 ; folding of. 61, *62 ; modifi- 
 
 cations, 58 ; muscles, *65 ; vibration, 
 
 63, 103 
 Wistinghausen, von, 436 
 Witlaczil. 422, 430. 440. 443 
 Wollaston, on beetles of Madeira Ids., 
 
 371 
 Wood, T. W., 446 
 Wood-Mason, 411 
 Woodward, 441 
 Worker, ant, 330. 331 ; bee, *32i, 327, 
 
 328 ; termite, *3i6, 318 ; wasp, 329 
 
 Xanthophyll, as a pigment, 195, 215 
 
 Xenoiieiira, *386 
 
 XiphidiiiDi, stridulation of, 105 
 
 Yellow fever, 304 
 
 Yolk. *i46, *i47 
 
 Young, on luminosity, 132 
 
 Yucca, pollination of, *264, *265, 266 
 
 Zaitha. 191 
 Zander, 421 
 Zimmermann. 432 
 Zittel. von. 413 
 
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