Issued Jurul4, ,1911. U. S. DEPARTMENT OF j\GRICULTURg, BUREAU OF ANIMAL INDUSTRY. BULLETIN 130. & =- <4 A. D. MELVIN, CHIEF OF BUREAU. JDIES ON THE BIOLOGY OF THE TEXAS-FEVER TICK. BY H. W. GRAYBILL, Assistant Zoologist, Zoological Division, Bureau of Animal Industry. UNIVERSITY OF CALIFORNIA* LOS ANGELES SEP 23 1952 LIBRARY GOYT. PUBS. ROOM WASHINGTON: GOVERNMENT PRINTING OFFICE. 1911. Ksm-il June 14, 1911. U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF ANIMAL INDUSTRY. BULLETIN 130. A. D. MELVIN, CHIEF OF BUREAU. STUDIES ON THE BIOLOGY OF THE TEXAS-FEVER TICK. BY H. W. GRAYBILL, Assistant Zoologist, Zoological Division, Bureau of Animal Industry. WASHINGTON: GOVERNMENT PRINTING OFFICE. 1911. THE BUREAU OF ANIMAL INDUSTRY. Chief: A. D. MELVIN. Assistant Chief: A. M. FARRINGTON. Chief Clerk: CHARLES C. CARROLL. Animal Husbandry Division: GEORGE M. ROMMEL, chief. Biochemic Division: M. DORSET, chief. Dairy Division: B. H. RAWL, chief. Inspection Division: RICE P. STEDDOM, chief; MORRIS WOODEN, R. A. RAMSAY, and ALBERT E. BEHNKE, associate chiefs. Pathological Division: JOHN R. MOHLER, chief. Quarantine Division: RICHARD W. HICKMAN, chief. Zoological Division: B. H. RANSOM, chief. Experiment Station: E. C. SCHROEDER, superintendent. Editor: JAMES M. PICKENS. ZOOLOGICAL DIVISION. Chief: B. H. RANSOM. Assistant Zoologists: ALBERT HASSALL, HARRY W. GRAYBILL, and MAURICE C. HALL. Junior Zoologists: HOWARD CRAWLEY and WINTHROP D. FOSTER. LETTER OF TRANSMITTAL. U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF ANIMAL INDUSTRY, Washington, D. C., September 28, 1910. SIR: I have the honor to transmit for publication the accompanying manuscript entitled "Studies on the Biology of the Texas-fever Tick," by H. W. Graybill, assistant zoologist in the Zoological Divi- sion of this bureau. A large number of publications have been issued from time to time regarding the investigations of this bureau concerning the Texas- fever tick and its disastrous effect upon the cattle industry of the South, and the extermination of the parasite has in recent years been vigorously pushed both by the Federal Government and the several States involved. In order that this work of extermination may be the more intelligently and successfully carried out it is necessary that it should be based upon the most accurate knowledge possible of the life history, habits, etc., of the tick. Accordingly the experiments herein described were projected in order to add further information relative to certain biological features of the tick which may have a bearing upon the eradication work. The experi- ments were carried out in cooperation with the veterinary depart- ment of the Alabama Polytechnic Institute, at Auburn, Ala. I recommend that the paper be published in the bulletin series of this bureau. Respectfully, A. D. MELVIN, Chief of Bureau. Hon. JAMES WILSON, Secretary of Agriculture. CONTENTS. Page. Introduction 7 Historical 7 Methods of study 9 Periods of the nonparasitic portion of development 12 The preoviposition period 12 The oviposition period 13 Incubation period 14 Hatching period 15 Longevity period 16 Total time of nonparasitic development 17 Number of eggs laid and percentage hatched 18 Experiments with horizontal tubes 19 Records obtained from the field plots 20 Per cent of females ovipositing 22 Effect of immersion in water on engorged females 23 The influence of moisture on the incubation period 23 Periods in the parasitic portion of development 24 Observations on the movement of ticks after the first and second molt 26 . Change of location after first molt 26 Change of location after second molt 27 Early distinguishing of female nymphs by males 27 Experiments in transferring ticks on cattle 27 Experiments in rearing unfertilized females 29 The occurrence of dead ticks on cattle 31 Host relations of the cattle tick 31 Infestation experiments on rabbits 32 Infestation experiments on a cat 33 Infestation experiment on a dog 33 Infestation experiments on sheep 33 The natural occurrence of the cattle tick on sheep 34 The progeny of females matured on sheep noninfectious 36 Man as a host of the tick 37 Bibliography 3S Appendix: TABLE 1 . Individual records of ticks used in experiments 40 TABLE 2. Data on parasitic development of ticks on animals 42 5 ILLUSTRATIONS. Page. FIG . 1 . Vertical tube used for incubating eggs of tick 3 9 2. Horizontal tube used for incubating eggs of ticks 10 3. Arrangement of field plot for incubating tick eggs under outdoor con- ditions 12 6 STUDIES ON THE BIOLOGY OF THE TEXAS-FEVER TICK. INTRODUCTION. The eradication of the cattle tick ( Margaropus annulatus) from the States below the quarantine line has been shown to be entirely feasible as a result of the work carried on during the past five years by the Bureau of Animal Industry in cooperation with the State authorities. The work of extermination must, obviously, be preceded by and based upon a knowledge of the life history of the tick, its habits, and the manner in which it is affected by climatic and other environmental conditions. In order to supply possibly useful data relative to the biology of the tick, additional to that already collected by different observers, a series of investigations was arranged for and carried out under cooperation between the Zoological Division of this bureau and the veterinary departhient of the Alabama Polytechnic Institute at Auburn, Ala. In the observational part of these investigations, the results of which are recorded in the present paper, the writer was assisted by Mr. W. M. Lewallen. Some of the results of the work at Auburn have been briefly mentioned in an earlier paper (Graybill, 1909) 10 . a HISTORICAL. Up to the time that Dr. Cooper Curtice 2 (1891) of this bureau established the fundamental facts in the life history of the cattle tick it was commonly assumed that the life history of this species corre- sponded to that of certain other ticks, which fall from their host before shedding their skins in transforming from one stage to another. Curtice, however, showed that the cattle tick remains on the host from the time it attaches as a larva until it falls as an engorged female to deposit its eggs, and established other facts relative to the duration of some of the periods in the life cycle and the changes in structure occurring at the time of the first and second molts, which were supplemented in a second paper 3 (1892) by further data concern- ing the life history, habits, and structure of the tick. Smith and Kilborne 22 (1893), who were the first to demonstrate and prove the connection between the tick and Texas fever, published a number a Citations to literature are given In bibliography on page 3S. 89053 Hull. 13011 2 8 BIOL.OGY OF THE TEXAS-FEVER TICK. of important facts on the biology of this parasite, and Schroeder 18 > 19 (1900 and 1907) and Schroeder and Cotton 20 - 21 (1900 and 1907) in several articles issued by this bureau have presented considerable data bearing on the life history of the tick and its relationship to the disease which it transmits. Curtice 5 (1896) was among the first to urge the undertaking of eradication measures, and (1897) 6 was the first to show how cattle could be freed from, ticks by rotation methods. Doctor Curtice's work in North Carolina, continued by Dr. Tait Butler, clearly demonstrated at an early date the feasibility of tick eradication, which has been fully confirmed by the experience of the more extensive campaign now under way in various parts of the tick-infested area. Several investigators connected with State experiment stations have studied the tick with reference to its life history. Dinwiddie 8 (1892), of the Arkansas Experiment Station, was an early investigator, who more recently (1908) 9 has published further observations. Morgan (in Dalrymple, Morgan, and Dodson, 7 1898) reported investigations conducted in Louisiana having to do with various stages of the tick, especially with regard to the influence of heat, cold, and light and the effects of water upon the tick and its eggs. Later the same author 14 ' 15 (1903, 1905) discussed and emphasized the practicability of freeing cattle and pastures of ticks by following pasture-rotation methods based upon known facts in the life history. Newell and Dougherty 16 (1906), of the State Crop Pest Commission of Louisiana, made a comprehensive study of various periods in the life cycle, obtaining valuable data on the duration of the incubation period and the vitality of the larvas, at different times of the year. Their work was conducted at Baton Rouge, La., and they formulated a pasture-rotation method for ridding cattle and farms of ticks, adapted to conditions prevailing in Louisiana. Cotton 1 (1908), of the Ten- nessee Experiment Station, has published life-history notes based on investigations conducted at Knoxville, Tenn., and has suggested a number of rotation methods for tick eradication. Recently the Bureau of Entomology of this department has under- taken life-history studies of the tick and has issued Bulletin 72, by Hunter and Hooker 12 (1907), in which are incorporated the results of comprehensive investigations conducted by these authors at Dallas, Tex. The results obtained by these investigators are confirmatory of the earlier work of the Bureau of Animal Industry and other observers, and in addition have largely increased our knowledge of the biology of the tick, supplying data concerning all stages of development, time required for the completion of these stages at different seasons of the year, and the influence of variations in environment, together with suggestions for the practical application of the information given. THE EGG INCUBATION TUBES. METHODS OF STUDY. The plan pursued in determining the incubation period of dggs and the longevity of seed ticks in the investigations at Auburn was essen- tially that followed by Newell and Dougherty 1 " :100G). A number of engorged females were collected at the beginning of each month. After oviposition began the eggs laid by each tick were removed at the end of every 24 hours. After they were counted each lot was placed in an incubation tube marked with the date when removed and a number indicating the tick which deposited them. Careful observations were made on the tubes and a record was kept of the time when the eggs in each tube began to hatch and when the hatching was completed, also when the larva 1 began to die and when all of them were dead. At the outset of the work the incubation tubes used were test tubes of the type employed in bacteriological work. These were filled half full of moist sand. A cardboard disk cut so as to fit the tube was pressed down on the sand. On top of this was placed a small cube of cork, and on the latter was placed another disk similar to the first. The eggs were placed on the upper disk. It was found necessary to use these disks in order to prevent the eggs and seed ticks from becoming mixed with the sand, which would have rendered observation very difficult and also would have made the counting of the unhatched eggs and dead seed ticks, for the purpose of deter- mining the percentage of eggs hatching, an almost impossible task. Furthermore, if only one disk is used the development of the eggs is frequently endangered by the growth of mold. When the two are used, separated in the manner indi- cated, mold frequently grows on the lower one, but does not often attack the upper one in such a manner as to endanger the eggs. These tubes, however, were not found entirely satisfactory on account of the fact that there was no practicable way of adding more water to the sand and thus keeping the tube supplied with moisture. To obviate this defect a new tube was devised which was found very satisfactory in most re- spects (see fig. 1). It is so constructed that it is possible to add water to the sand at any time. The new tubes are made of glass cylinders 11.5 cm. long and about 20 mm. in outside diameter. One end of the cylinder is closed by a cork, pierced in the middle by a FIG. ]. Vertical tul>e u for incubating ejrtrs ticks. 10 BIOLOGY OF THE TEXAS-FEVER TICK. hole about 5 mm. in diameter. Into this opening is fitted one arm of a piece of glass tubing bent in the form of a hook. This arm should be long enough to pass through the cork and the bend should be just so broad that the long arm runs up close to the outside of the glass cylinder. The long arm should reach to about the middle of the tube. Water is added through this portion of the tubing. The cardboard disks are arranged in the same manner as in the test tubes previously described, the only modification necessary being to pierce the disks with a needle in order to permit the escape of air from below upward when water is added. In case the short arm of the tubing becomes clogged with sand the tubing is easily removed and flushed out with water. The incubation tubes were closed on top by means of muslin held in place by rubber bands. Cheese cloth is not satisfactory for this purpose, being so loosely woven that the larvse escape through the openings. During the course of the work a much simpler method than the above for obtaining records on the nonparasitic stages of the tick FIG. 2. Horizontal tube for incubating eggs of ticks. was devised. In this method a horizontal tube is used (see fig. 2). This is made of a glass cylinder like that described above. A cork is inserted in one end. On the bottom of the cork a rectangular piece of cardboard is fastened so that one of its Jong sides projects a little beyond the edge of the cork and serves as a support for the tube, preventing it rolling from side to side. The tube contains a tray constructed as follows: A rectangular piece of rather thick paper, with a width equal to one-half the inside circumference of the tube and a length equal to the internal length of the tube, is provided for the bottom and. sides. The ends are made of thin disks of cork having a diameter a little less than the internal diameter of the tube. The rectangular piece of paper is rolled into a half cylinder and the cork ends are pinned or glued into position, each tilting a little toward the other. One of the disks is placed some little distance from the end of the tray, a fingerhold being thus afforded for withdrawing it from the tube. The end of the tube is covered with a piece of muslin. METHODS OF STUDY. 11 This particular form of horizontal tube was kept when in use beneath a bell jar supplied with moisture. Another variety with sand in the end next the cork and fitted with a piece of glass tubing for the addition of w r ater, as in the vertical incubation tubes, was also used. These latter tubes furnished conditions practically identical with those in the vertical tubes. Various modifications of these horizontal tubes were used, some being made of ordinary test tubes, but they are hardly of sufficient importance to be described here. The method of using the horizontal tube is as follows: An en- gorged female is placed in the tray, which is put in the tube. The tilted ends prevent the tick from crawling up. After oviposition begins the tick moves slowly backward, leaving a long mass of eggs in front of it. When oviposition is nearly completed the female is removed from the eggs to the opposite end of the tray, so as to facili- tate observation of the remainder of the process. The newly laid eggs are removed from her each day and placed at the end of the egg mass until oviposition is completed. The hatching proceeds along the mass of eggs until the last hatch, unless, as sometimes happens, there is a displacement of the eggs. The dates when the female was collected, when oviposition began and ended, when hatching began and was completed, and when the first and the last larvae died are recorded. This method requires such a small amount of time daily in attending to the tubes that a very large number of ticks can be kept under observation at one time and under various conditions. For the purpose of checking the results obtained in the tubes indoors, experiments were conducted outside in sunny and shady places presenting ordinary pasture conditions. In these experiments small plots in a pasture were used (fig. 3). Each plot consisted of an area 2 feet square inclosed by boards 3 inches wide set edgewise. In the center of the plot an ordinary cigar box with the lid and bottom removed was sunk halfway into the turf. This was done so -as to confine the female ticks and thus facilitate observation on them. The box was provided with a cover made of screen wire, which, during the progress of the experiment was covered over with dead leaves or other litter. The plots were protected from surface drainage by properly arranged ditches. Each was surrounded by a fence of wire netting to keep out animals. There were two series of these plots, one in a place shaded by trees for a part of the day and the other in an unshaded place. The indoor experiments were conducted in an unheated room with the windows open at all times as high as was practicable. The tem- perature and humidity were thus made to correspond very closely to outdoor conditions. The experiments in the plots were run parallel with the indoor experiments Usually two plots were started at the beginning of 12 BIOLOGY OF THE TEXAS-FEVER TICK. each month. Ordinarily 10 engorged ticks were confined in the box described above and observations were continued on each plot until it became free of seed ticks. PERIODS OF THE NONPARASITIC PORTION OF DEVELOPMENT. The various periods in the nonparasitic portion of the development of the tick which will receive consideration in the following pages are, the preoviposition period, the oviposition period, the incubation period, the hatching period, and the longevity of the larvae; also the FIG. 3. Arrangement of field plot for Incubating tick eggs under outdoor conditions. entire period from the time the female drops until all the larvae are dead. Unless otherwise specified the records given hereafter refer to the experiments in the vertical tubes. THE PREOVIPOSITION PERIOD. This period, so named by Hunter and Hooker 12 (1907, p. 14), extends from the time the female tick drops until she begins to oviposit. Its duration was found to vary greatly for the different months of the year, depending largely on the temperature. The average length of the period, as shown in the following tables, ranged from 3 to 49.3 days. The maximum period observed was 98 days and the minimum 1 day. The latter is not included in the tables, THE OVIPOSTTION PERIOD. 13 as it was observed outside the course of the regular experiments. It occurred in the case of a moderate-sized tick collected April 29, 190X, which had been placed in a flask along with some others. During the preoviposition period the ticks under observation were kept either in petri dishes, the bottoms of which were lined with paper, in pasteboard boxes, or in horizontal tubes. The results obtained relative to the preoviposition period, arranged according to the months during which the ticks were collected, are given in the following tables: Preoviposition period Range and average length of periods. VERTICAL-TUBE EXPERIMENTS. Date ticks were collected. Number of ticks. Range of periods. A verage of periods. Date ticks were collected. Number of ticks. Range of periods. Average of periods. 1907. June 1 7 Days. tj to 9 Days. 1 1908. Jan. 1 29 and 30... Days. 34 to 1)3 Day*. 41.2 July 1 7 3 to 4 3.9 Feb. 3, 4, 27, and 28. 8 to 30 22.2 \ug. 1 and 31 14 2 to 4 3.1 Mar. 20 and 29. ... 9 4 to 8 5.2 Oct 1 7 4 to ti 4 3 Apr. 29 14 4 to 7 5 9 Nov. 1 and 30. Dec. 29 11 3 7 to 9S 39 to 03 30.5 49.3 HORIZONTAL-TUBE EXPERIMENTS. 1907. Aug 31 4 3 3 1908. Feb. 3, 24,27,and28. , 10 to 33 18.3 Oct 1 4 4 Mar. 1, 3, 23, and 25. 7 5 to 11 7 Nov. 1 and 26 5 9 to 33 18.2 Apr. 29 and 30. 10 5 to 8 6.5 Dec 25 2 27 to 33 30 May 1 5 to 9 C.I In both tables it is seen that the highest average is for the mont h of December and the lowest for the month of August. THE OVIPOSITIOX PERIOD. The duration of this period depends on the temperature, and to a less degree on a number of other things, such as state of engorgement, number of eggs laid, etc. The ticks used were always good specimens, as near complete engorgement as it was practicable to obtain. The average oviposition period for different months of the year, as shown in the following table, ranged from 8.3 days for June, 1907, to 127.5 days for November of the same year. The maximum period noted was 152 days and the minimum 3 days, observed in the case of ticks which began ovipositing in November and June, respectively. 14 BIOLOGY OF THE TEXAS-FEVER TICK. Oviposition period Range and average length of periods. VERTICAL-TUBE EXPERIMENTS. Month oviposition began. Number of ticks. Range of periods. Average of periods. Month oviposition began. Number of ticks. Range of periods. Average of periods. 1907. June Days. 3 to 14 Days. 8 3 1908. January 2 Days. 54 to 87 Days. 70 5 July 4 to 20 12 9 3 37 to 63 46 7 August 12 to 19 15.6 March 14 17 to 43 30 2 September 14 to 19 16.5 April 7 14 to 35 24 9 October 21 to 37 32 9 Mav 14 19 to 27 22 8 November 78 to 151 98.4 HORIZONTAL-TUBE EXPERIMENTS. 1907. September (j 9 to 21 15 1908. January 4 73 to 91 79 October .... 4 22 to 37 29.7 March 16 26 to 49 34.6 November 4 83 to 152 127.5 April 1 24 24 Mav 16 15 to 24 20.8 INCUBATION PERIOD. The duration of this period depends principally on the temperature. It was found to range from 19 days in the summer to 180 days begin- ning in the fall. Low temperatures not only retard but even may arrest temporarily or permanently the development of the eggs. Moisture, although necessary to development, has but a small influ- ence, if any, on the rate at which this takes place. The conditions essential to the development and eventual hatch- ing of eggs are a proper supply of moisture and a favorable tempera- ture. All that is required in the way of moisture is a sufficient atmospheric humidity to prevent eggs losing moisture by evaporation. With regard to temperature it may be said that the maximum, mini- mum, and optimum temperatures for development of the eggs have not been determined. Hunter and Hooker 12 (1907) have assumed 43 F. as the minimum, but this has not yet been verified by experi- ment. Eggs are frequently killed by the low temperatures occurring during the winter months, although those that have been incubated for a time are less susceptible to the ill effects of cold than those newly laid. As has been previously stated, the eggs were removed from each female tick at the end of every 24 hours and placed in vertical tubes. A record was kept of the date each lot was laid, the date the eggs began to hatch, and the date they completed hatching. The latter date is, however, only approximately correct, since it is not possible to determine accurately when all the eggs of a lot have hatched, on account of the fact that some eggs having all the marks of viability frequently fail to hatch. By using the three dates just mentioned, two incubation periods were determined for each lot of eggs, which THE HATCHING PERIOD. 15 are referred to here as the maximum and minimum. The range of the incubation periods of the eggs laid by each tick is given in Table 1 of the Appendix. The range of the minimum incubation periods and the averages for each month, from June, 1907, to May, 1908, are given in the following table: Incubation period Range and average length of minimum incubation periods. Month eggs deposited. Number of lots. Range of periods. Average of periods. Month eggs deposited. Number oflots. Range of periods. Average of periods. 1907. June 60 Days. 22 to 27 Days. 24.5 1908. February 1 Days. 80 Days. 80 July 82 19 to 24 20.5 March 270 46 to 63 52.7 August 90 19 to 24 21.2 April 197 36 to 53 43.6 September 81 28 to 64 35.9 May 279 23 to 34 26.3 October 145 165 to 180 173.1 November 31 148 to 170 155.5 December 7 117 to 139 128. 6 From the above table it is seen the averages increase from July to October, 1907, and decrease from November, 1907, to May, 1908. The average for June, 1907, being higher than for July, which marks the beginning of the increase, indicates that the average for the latter month is the lowest that would have been obtained had the experi- ments covered the first part of the year. The longest minimum incubation period was 180 days and the shortest 19 days. HATCHING PERIOD. The eggs deposited by a female do not all hatch at the same time, but approximately in the sequence in which they are laid. The time required for all of the eggs to hatch after hatching begins may be called the hatching period. This may be considered normal in length only when approximately ah 1 the eggs hatch or a goodly portion of the first and the last eggs deposited hatch. Because of the low percentage of eggs which hatched in the case of some of the ticks the hatching periods of these have no significance and are, therefore, not considered in the following table. The average period for different months of the year is seen in the following table to range from 10.6 days for July, 1907, to 36 days for October of the same year. The maximum period observed was 49 days and the minimum 4 days. The eggs of all the ticks collected previous to October, 1907, hatched in the fall and those laid by ticks collected October 1 did not begin to hatch until the following March, and of course the eggs of those collected during November and the succeeding months did not begin to hatch until later, consequently no hatching periods were obtained during the colder part of the year. It is therefore evident that the maximum period observed is much less than might occur with a slightly different winter season, or if ticks had been collected 89053 Bull. 13011 3 16 BIOLOGY OF THE TEXAS-FEVER TICK. on such a date that the hatching of the eggs would have begun in the fall and not been completed until the following spring. Hatching period Range and average length of periods. VERTICAL-TUBE EXPERIMENTS. Month hatching began. Number of ticks. Range of periods. Average of periods. Month hatching began. Number of ticks. Range of periods. Average ofperiods. 1907. July 14 Days. 4 to 17 Days. 10 6 1908. March 6 Days. 21 to 31 Days. 26 August 7 8 to 16 13.4 April 8 16 to 27 23.6 October 6 31 to 49 36 May 11 12 to 18 14 3 June. 14 12 to 22 17 2 HORIZONTAL-TUBE EXPERIMENTS. 1907. October 5 18 to 37 23.6 1908. March 31 21 to 24 22 3 April 7 i 10 to 27 21.3 May... 12 ' 9 to 21 15.6 June 16 j 5 to 18 11.4 LONGEVITY PERIOD. The longevity of the larvae depends on individual vitality, humid- ity, and temperature. Some larvae do not have sufficient vitality to disengage themselves from the ruptured eggshell and die partly inclosed within it. This was especially noticeable in eggs laid during the winter, so it would seem that a low temperature may affect the vitality of unhatched larvae. Other larvae die very soon after emerging. Cold prolongs longevity because of the fact that the tick remains quiescent, and as a result the body fluids and nourish- ment are conserved. A high relative humidity prolongs longevity by hindering the loss of body moisture by evaporation and also by causing the ticks to remain more quiescent than when the air is dry. In addition to these factors certain instincts of the larvae promote longevity. They respond negatively to light. In sunny places they collect on the under or the shady side of leaves, stems, and other objects, thus protecting themselves from the direct heat of the sun. They also manifest an interesting adaptation in being able to detect the presence of a possible host at a distance of several feet. This fact was observed and verified many times with larvae located on plots outdoors. Larvae that were quiescent when one approached within 3 or 4 feet of a plot, in the course of a half to several minutes became very active and extended their front legs upward in a divergent position, waving them violently in an evident attempt to seize onto a host. This instinct is probably dependent on an olfactory sense resident in the organ of Haller located on the tarsi of the first pair of legs. It may possibly be THE LONGEVITY PERIOD. 17 connected with a thermal sense, but this hardly seems probable, since the reaction was found to occur just as readily on extremely warm days as on cool days. The response takes place more quickly when one is located on the windward side of the larvae. .This instinct permits the larvae to remain quiescent without reducing their chances for reaching a host. The periods of inactivity conserve the vitality of the tick and consequently must prolong longevity. In making observations on the longevity > the date when the larvae in each tube began to die and when all of them were dead was re- corded. In determining the longevity of the larvae resulting from each lot of eggs, the date when the eggs began to hatch, together with the two dates just mentioned above, were used, thus obtaining a min- imum and maximum longevity period. The range of the maximum and the minimum longevity and the average of the former for lots of larvae hatched during the different months of the year, are given in the following table: Longevity period Range of maximum and minimum longevity and average of maximum longevity. Range of Range of Average Range of Range of Average Month hatched. Num- ber of lots. mini- mum lon- gevity maxi- mum lon- gevity of maxi- mum lon- gevity Month hatched. Num- mini- ber of mum Ion- lots, gevity maxi- mum lon- gevity of maxi- mum lon- gevity- periods. periods. periods. periods. periods. periods. 1907. Days. Days. Days. 1908. Days. Days. Days. July 106 4 to 39 7 to 85 38.6 March 24 5 to 22 57 to 94 73.2 August 83 9 to 36 9 to 192 84.9 April 189 3 to 63 19 to 99 65.1 September . 44 4 to 35 9 to 190 56.2 May. 406 2 to 57 4 to 103 62.3 October 75 5 to 163 30 to 234 167.4 June 380 4 to 55 8 to 128 65.1 November... 5 21 to 70 33 to 135 85 The eggs which hatched during July, August, and September were kept in tubes which were not supplied with water other than that originally added to the sand. This may account for the rather low averages for July and September. It is noted that the highest average is for the lots hatched during the month of October, and this month also gave the longest maximum period; the lowest average is for July, which likewise gave the shortest maximum longevity period. TOTAL TIME OF NON PARASITIC DEVELOPMENT. The period of nonparasitic development is the time from the date the female drops until all the resulting larvae are dead. It is of prime importance from a practical standpoint, since it indicates the length of time animals must be kept out of an infested pasture in order for it to become tick free. A summary of the data on this period is given in the table following. 18 BIOLOGY OF THE TEXAS-FEVER TICK. Total time from dropping of female until all resulting larvse are dead. Date engorged females were collected. Number of en- gorged, females. Range of entire-time periods. Average of pe- riods. Date engorged females were collected. Number of en- gorged females. Range of entire-time periods. Average of pe- riods. Junel, 1907. ... Julyl, 1907. ... Aug. 1, 1907. .. 7 7 Days. 79 to 100 82 to 112 172 to 221 Days. 86.9 101 199.6 Dec. 29, 1907, to Jan. 1,1908 Jan. 29 to Feb. 4, 3 Days. 181 to 207 Days. 196.3 Aug. 31, 1907 6 230 to 272 250.7 1908 7 156 to 189 173 1 Oct. 1, 1907. ... Nov. 1, 1907. ... Nov. 30, 1907 . . . 7 7 . 3 276 to 288 200 to 253 187 to 249 279.6 232.7 217 Feb. 27 to 28, 1908. Mar. 26 to 29, 1908. Apr. 29, 1908 2 9 14 143 to 162 144 to 161 122 to 173 152.1 152.1 142.8 In the above table the averages are seen to increase from 86.9 days for June, to 279.6 days for October, 1907, and to decrease from the latter month for the rest of the time. The maximum periods likewise increased from 100 days for June to 288 days for October and there- after steadily decreased each month until March. NUMBER OF EGGS LAID AND PERCENTAGE HATCHED. The eggs laid by each female (except in the case of controls, which are referred to below) were counted when they were removed and before the}' were placed in the incubation tubes. And furthermore, after all the larvse in each tube had perished, the unhatched eggs were removed and counted. The purpose of this was twofold, first to determine the number of eggs laid by a female, and, second, to calcu- late the percentage of eggs which hatched. In the case of certain ticks, the eggs of which were left uncounted for the purpose of serving as controls on the counted eggs, it was necessary, in addition to count- ing the unhatched eggs, to count the dead larvse in order to determine the number of eggs laid. The data obtained are given in columns 3 ;ind 11, respectively, of Table 1, Appendix. A summary showing the range in the number of eggs laid by each lot of ticks, the average number of eggs laid and per cent hatched, is presented in the following table: Egg laying and hatching Total and average number of eggs laid and per cent hatched. Date ticks col- lected. Num- ber of ticks. Eggs laid. Aver- age eggs laid. Eggs hatched. Date ticks col- lected. Num- ber of ticks. Eggs laid. Aver- age eggs laid. Eggs hatched June 1, 1907. . July 1, 1907. . Aug 1, 1907. . . Aug31, 1907.. Oct 1,1907.. . Novl, 1907. . Nov 30, 1907 . . 7 6 7 7 4 Number. 630-3,095 1.858-3,820 1,851-3.683 2.049-2,809 960-3,385 991-2,961 357-3, 20; Number 1,811 2,919 2, WO 2,405 2,563 2,129 2,173 Per ct. 73-95 90-97 90-98 57 97 Dec. 29, 1907, to Jan. 1,1908... Jan 29, to Feb. 4, 1908 4 7 2 9 9 Number. 1,970-4,272 806-4.276 2,302-2,925 2.680-4,559 3, 246-5, 105 Number 3,149 3,331 2,614 3,507 4,089 Perct. 0-35 14-86 62-96 66-97 33-98 77-92 1-7 0-18 Feb. 27-28, 1908. Mar. 26-29. 1908. Apr. 29, 1908.... EXPERIMENTS WITH HORIZONTAL, TUBES. 19 The minimum number of eggs laid was, as the above table indicates, 357, and the maximum number 5,105. The average number ranges from 1,811 to 4,089. The percentage of eggs hatching in the case of ticks collected from November 1, 1907, to January 1, 1908, ranged from to 35, and for the rest of the time from 14 to 98. In counting the eggs they were placed on white paper and arranged in a long row one egg deep and several eggs wide. In order to injure them as little as possible and reduce the chances of crushing them, small spatulas made of thin paper were used in handling them. The counting was done with the aid of a pocket lens. For the purpose of determining whether the manipulation involved in counting the eggs reduced the percentage that hatched, two ticks in each of the first six sets of experiments were selected as controls, their eggs not being counted. The results are given in the following table: Percentage of eggs hatching from counted and uncounted lots. Date ticks collected. Num- ber of ticks. Eggs counted or uncounted. Per cent hatched. Date ticks collected. Num- ber of ticks. Eggs counted or uncounted. Per cent hatched. 1907. June 1 5 Counted . . 92. 1 1907. Aug. 31 6 Counted .... 79.5 Do ... 2 Uncounted. 84.9 Do 1 Uncounted.. 97 July 1 5 Counted 95.3 Oct. 1 Counted 85.5 Do... 2 Uncounted. 95 Do 2 Uncounted.. 85.7 Aug. 1 ... 5 Counted ... 95.3 Nov. 1 -5 Counted. . . a4 Do 2 Uncounted. 95.8 Do 2 Uncounted.. Two of the above averages for the controls are less and four are more than the corresponding averages for the counted eggs. Disre- garding, however, slight differences ranging from 0.2 to 1.6 per cent, which have little significance, the corresponding average may be said to be the same in all except two cases. In one of these the average for the control is 17.5 per cent more and in the other 7.2 per cent less. It seems safe to say from the above results that the manipulation involved in counting, when done with moderate care, does not appre- ciably lower the per cent of eggs hatching, and that this has not materially affected the percentage of eggs hatched in the course of the present experiments. EXPERIMENTS WITH HORIZONTAL TUBES. The tubes used in these experiments have already been described on page 10 (see fig. 2). Those referred to below as being supplied with moisture were either kept in a moist chamber or were of the type having sand in one end. A summary of the data is given in the table following. 20 BIOLOGY OF THE TEXAS-FEVER TICK. Summary of the data obtained from the experiments with horizontal tubes. Total time from date Date ticks were collected . Preoviposi- tion period. Oviposi- t i on period. Incubation period. Hatching period. Longevity of larvae. Conditions of experiment. females were col- lected to death of larvse. 1907. Days. Days. Days. Days. Days. Days. AUK 31 3 9 to 17 30 to 31 18 to 22 a 195 to 217 Moisture 299 to 250 Oct. 1 4 22 to 37 165 to 167 21 to 24 78 to 92 do 247 to 261 Nov. 1 9 to 20 130 to 152 167 16 70 do 246 Nov. 26.. 20 to 33 (6) do Dec. 25 27 to 33 74 to 78 88 to 94 10 to 25 62 to 83 . do. . . 204 1908. Feb. 3 29 to 33 35 to 49 53 to 59 20 to 27 87 to 109 do 172 to 194 Feb. 24 to Mar. 3.. 10 to 16 .50 to 40 50 to 56 16 to 24 71 to 105 ...do... 131 to 168 Mar. 23 to25 5 to 6 26 to 31 43 to 48 9 to 15 49 to 71 do. .. 103 to 121 Apr. 29 to 30.. 5 to 8 21 to 24 29 to 32 5 to 18 79 to 111 do 114 to 147 May 1 5 to 9 15 to 21 29 to 31 6 to 10 15 to 17 No moist- 50 to 53 ure. o After all the eggs had hatched the larvae were placed on vegetation outdoors. 6 Only a few eggs were laid, all of which shriveled. The minimum entire time when the tubes were kept moist occurred hi the case of ticks collected March 23 to 25, 1908, and the maximum with the ticks collected October 1, 1907. In the case of the vertical tubes the maximum entire time also fell to the ticks collected October 1 . For the purpose of determining the influence of moisture on the duration of the entire time some ticks collected May 1, 1908, were kept in tubes which were not supplied with moisture. Other ticks collected April 29 and 30 were supplied with moisture as usual. The difference in the result is very striking, the duration in the latter case being nearly three times as long as in the former. RECORDS OBTAINED FROM THE FIELD PLOTS. In the indoor experiments the conditions were made to correspond as nearly as possible with those existing outside. It was evident, however, even before the work presented in this bulletin was taken up, that this could only be accomplished in a very imperfect manner and that it would be well to conduct a parallel set of experiments outside under natural conditions for the purpose of checking the indoor experi- ments. Natural conditions are far from being uniform, however. Even in the same pasture a variety of environments may be present and the duration of the various periods in the life history of the tick be quite different under each. Furthermore, climatic conditions may vary considerably from year to year in the same place. The impor- tant thing, however, from a practical standpoint is to determine the environments that will give maximum and minimum periods. An attempt was made to obtain such periods by running two sets of field plots, one on well drained, sunny ground and the other on moist, partly shady ground. The character of the plots and the method of INFLUENCE OF ENVIRONMENT. 21 confining the ticks have been described on page 11. In these experi- ments it was not possible to make notes on individual ticks, and con- sequently the data are not as complete as those of the indoor work. The data of economic importance are the date the first eggs hatched and the date all the larvae were dead. In four of the plots located in the sun, started June 3, July 1, August 1, and August 31, 1907, the engorged ticks were destroyed by small red ants; in two started November 1, 1907, and January 31 to February 1, 1908, eggs were deposited but no larvae appeared; and in three started November 26 and December 16, 1907, and January 1, 1908, all the females died without ovipositing. In the case of plots located under partly shady conditions, in three of them started on August 31, October 1, and November 1, 1907, eggs were deposited but no larvae appeared; in two started November 26 and December 16, 1907, all the females died without depositing eggs. In all the plot experiments started between November 1, 1907, and January 1, 1908, inclusive (see second table below), no larvae appeared, either for the reason that the females succumbed to the severe weather or that the eggs deposited failed to hatch. The records of the last three plots located in the sunlight and in the shade furnish an interesting comparison with regard to the influence of environment on the eggs and larvae. They are given in the following table: Influence of environment on eggs and larvae. In sunlight In shade. Date ticks were collected. Date first eges hatched Date all larvse wore dead. Date ticks were collected. Date first eggs hatched. Date all larvae were dead. 1908. Mar. 1-2 May 8 July 31 1908. Feb 28-29 Mav 18 Aug. 3 Mar. 27-28 Mav 20 Aug. 8 Mir. 27 June 8 Aug. 23 Apr. 27 June 5 July 28 Apr. 27 June 18 Sept. 5 Larvae appeared from 10 to 19 days earlier in the sunny plots than in the shady ones and succumbed 3 to 39 days earlier. a Specimens of this ant were sent to Prof. \V. M. Wheeler, of Harvard University, for identification, and found to be one of our small "Thief ants,"* Solcnopsis m^lrfla Say, which is common in pastures and fields, where it leads a subterranean life and feeds on larvae and pupas of other ants, on sprouting seeds, dead insects, etc. 22 BIOLOGY OF THE TEXAS-FEVER TICK. In the following table a comparison is made of the results obtained in the vertical tubes and in the field plots: Comparison of records of vertical tubes and field plots, Auburn, Ala., 1907-8. Vertical tubes. Field plots. Date females were collected. Date first eggs hatched. Date all larvse were dead. Date females were collected. Date first eggs hatched. Date all larvae were dead. June 1 1907 July 4 July 28 Aug. 27 Oct. 3 Mar. 19 Apr. 17 May 4 Apr. 28 Apr. 27 Apr. 28 May 19 June 4 Sept. 9 Oct. 21 Mar. 9 May 29 July 15 July 11 Aug. 5 July 23 Aug. 11 Aug. 7 Sept. 3 Oct. 19 June 4, 1907 July 7 July 29 Aug. 30 (a) Aug. 29 Oct. 8 Mar. 27 July 1, 1907 July 1, 1907 Aug 1 1907 Aug. -1, 1907 Aug 31, 1907 Aug. 31, 1907 Oct. 1, 1907 Oct. 1, 1907 Apr. 10 (a) ( 6 ) () W May 14 May 8 May 20 June 5 June 8 Nov 1 1907 Nov. 1, 1907 ... Nov. 30 1907 Nov. 26, 1907 Dec. 29, 1907 to Jan. 1, 1908 Jan 29 to Feb. 4, 1908 Dec 16 1907 Jan. 1, 1908 Feb. 1 and 2, 1908 July 22 Aug. 3 Aug. 23 Sept. 5 Feb 27 and 28 1908 Feb 28 to Mar 2, 1908 Mar. 26 to 29 1908 Mar 27 and 28, 1908 . . . Apr. 29, 1908 Apr. 27, 1908 No larvae appeared. & All died without ovipositing. From the above table it will be noted that the period from the col- lection of the ticks to the tune the first eggs hatched in the case of the indoor experiments started June 1 and March 26-29 (33 and 54 days, respectively) is the same as for the corresponding outdoor ex- periments. In the case of the remaining experiments the time is shorter 1 to 22 days for the indoor than for the outdoor experiments. In all the experiments, except the one begun August 1 , the time from the collection of the ticks to the death of all the larvae was longer by from 5 to 42 days in the indoor than in the corresponding outdoor experiments. PER CENT OF FEMALES OVIPOSITING. The data obtained on this point are not very extensive. In each of the lots of ticks collected on the dates indicated in the second column of Table 1, Appendix, 100 per cent oviposited except in the case of the ticks collected November 30 and December 29, 1907, to January 1, 1908, of which 80 and 33 per cent, respectively, oviposited. Tick No. 27, collected August 31, 1907, deposited but 39 eggs, none of which hatched. This tick was very probably abnormal, but the ticks that failed to oviposit were no doubt unfavorably affected by low temperature. Of the ticks kept in the horizontal tubes only one failed to oviposit. This was collected February 3, 1908. The majority of the engorged females placed in the plots outside during the latter part of the fall and the winter of 1907-8 failed to oviposit. They appeared to suc- cumb as a result of low temperature and excessive moisture. The first indication of abnormality usually noticed was a reddish tinge EFFECT OF IMMERSION IN WATER. 23 appearing over the Malpighian tubules, which normally appear as yellow streaks through the integument o*f the tick. Then the tick began to swell, becoming very tightly distended, tiie color became dark, and finally, if not punctured by some enemy, the integument ruptured of itself and a sanguineous fluid issued from the opening. EFFECT OF IMMERSION IN WATER ON ENGORGED FEMALES. A number of tests were carried out to determine what effect immer- sion in water, both before and after the beginning of oviposition, has on engorged females. On May 1, 1908, eight engorged females were placed in separate wide-mouthed bottles and covered with distilled water. All of them died without ovipositing. The following tests were made in the Zoological Laboratory, Washington, D. C. : August 11, 1908, 10 engorged females were collected and placed in tap water. All died without ovipositing. August 13, 9 engorged females (collected August 12) were submerged in normal salt solution. All died without ovipositing. September 15, 13 engorged females (collected September 10) that had begun to deposit eggs were submerged in tap water. None of them continued to deposit eggs. September 15, 10 engorged females (collected September 10) that had begun to oviposit were placed in a Petri dish and half covered with tap water. None of them continued to deposit eggs. September 21, 8 engorged females (collected September 15) that had begun to oviposit were placed in tap water. All died without depositing additional eggs. The first effect of water on engorged ticks is to cause them to become distended, and later the coloring matter of the blood within the body escapes and colors the water. In some instances the dis- tention of the tick is so great that its form is almost spherical. This was not so pronounced in normal salt solution as in tap water. Hunter and Hooker 12 (1907) found that females submerged con- tinuously in tap water failed to oviposit. In one experiment, how- ever, they found that two out of five ticks submerged during October for 91^ hours deposited viable eggs, but ticks submerged for 115J hours failed to deposit eggs. THE INFLUENCE OF MOISTURE ON THE INCUBATION PERIOD. For the purpose of determining what influence moisture might have on the duration of the incubation period, eggs were subjected to different degrees of moisture. The eggs used each day had been deposited by a number of females during the previous 24 hours. Some of the lots were placed in the regular incubation tubes and others in test tubes containing wet sand. In the former case the eggs rested on cardboard that was never more than moist, while in the latter case they rested directly on wet sand. In one instance, referred to 24 BIOLOGY OF THE TEXAS-FEVER TICK. below, the eggs of a tick (No. 138, Table 1) were floated on water. This is considered a condition which will furnish a maximum amount of moisture. In determining the results of the tests the incubation periods of lots of eggs deposited on the same date and kept in regular incuba- tion tubes were averaged, and the same was done in the case of the eggs placed on moist sand. The averages for lots deposited on 12 days during March, 1908, are as follows: Average incubation periods of eggs under different moi:ture conditions. Mar. 9. Mar. 10. Mar. 11. Mar. 12. Mar. 13. Mar. 14. Mar. 16. Mar. 17. Mar. 18. Mar. 19. Mar. 20. Mar. 24. On cardboard Days. 55 Days. 53 Days. 54 Days. 53 Days. 53 Days. 52 Days. 51 Days. 51 Days. 53 Days. 53 Days. 53 Days. 51 On moist sand 51 52 3 52 51 50 50 49 53 51 55 51 It is seen that nine of the averages for eggs kept on moist sand run from one to four days less, two are the same and one is two days more than the corresponding averages for eggs on cardboard. The mean average for the eggs on wet sand is approximately one day less than for those on moist cardboard. The averages for 169 lots of eggs placed in regular incubation tubes and 101 lots placed on moist sand and on water (82 on moist sand and 19 on water), deposited from May 6 to 26, inclusive, 1908, show the following result : Five of the averages for eggs on moist sand and on water considered together are from one to two days less, thirteen are the same, and three are one day more than the corresponding aver- ages for eggs resting on cardboard. The average for all the lots of eggs on moist sand and water is three-tenths of a day less than for those on cardboard. From these tests, so far as they go, it appears that an abundance of moisture shortens the incubation period so little that for all practical purposes its influence may be disregarded. PERIODS IN THE PARASITIC PORTION OF DEVELOPMENT. There are three stages in the parasitic portion of the development of the tick, viz, larval, nymphal, and adult. Until the latter stage is reached males and females are not recognizable with certainty. The duration of each of these stages and the duration of a single infestation upon cattle during different portions of the year are of great practical importance. Upon the duration of an infestation depends the time animals must be kept on tick-free fields in order to become free from ticks. Tick-free animals were infested at nine different times, as indicated in column 1, Table 2, of the Appendix. It was found that the mini- mum larval period ranged from 5 to 7 days; the minimum nymphal PERIODS IN PARASITIC DEVELOPMENT. 25 period of females, 9 to 11 days; the adult period, from a minimum of 5 to a maximum of 33 days. The duration of each infestation, as given in the last column of the table, ranged from 30 to 66 days. The lower temperature during the fall and winter retarded the second molt of some of the ticks, prolonging the time that nymphs were present, and increasing the duration of infestation. It seems pos- sible also that the latter result may be partly due to delayed fertiliza- tion of the females, which could readily obtain in case the atmospheric temperature w r as such as to reduce the activity of the males. The maximum numbers in column 9 of the table (length of nymphal period) indicate the time from the molting of the first larva to the molting of the last nymph, and consequently represent the time that nymphs were present on the animal. This time in all probability is much longer than the nymphal period of any individual tick. A number of days previous to the second molt it is possible to dis- tinguish male and female nymphs with a fair degree of certainty. The former are somewhat smaller than the latter and also differ slightly in color and shape. The first nymphs to molt are males. The first female nymphs molt from one to several days later. All the male nymphs molt before the last female molts if they originally attached to their host on the same date. In the infestations made on February 29, April 4, and May 23, after the larvae had attached themselves a certain number were marked and observed from day to day. The range of the periods observed in these instances follow. Lenyth of period*, and total duration of para'itic development. Date larvae applied. Sex. Length of larval period. Length of nymphal period. Length of adult period. Duration of para- sitic period. 1908. Feb. 29 Females... Males . . Days. 8 to 9 7 to J 7 to 1 Days. 10 to 15 S to 10 Da>/s. 5 to 13 Days. 25 to 34 Do Do... (?)... A pr. 4 . . . Females.. Males . (i to 5 to 8 9 to 14 Mo 12 9 to 12 8 to 13 4 to 9 25 to 20 Do Mav 2:? Fomalps. (i O '.1 22 to 25 "Do Males Nineteen larva? were marked in the infestation of February 2<*. One of theses died previous to the first molt, three disappeared after the first molt, and one female died three days after the second molt. The male located beneath the latter left on the following day. Twenty- six larvae of the April infestation were marked. Sixteen of these disappeared previous to the first molt, one after the first molt, and one after the second molt. In the infestation of May 23, 23 larva 1 were marked. None disappeared previous to the first molt, four disappeared after the first molt, none disappeared after the second molt. . 26 BIOLOGY OF THE TEXAS-FEVER TICK. There seems to be no satisfactory explanation for the disappearance of the ticks, particularly those in the larval stage. Of course, ticks shortly after the first and second molt could easily be rubbed off. In comparing the maximum parasitic period in each of the three cases given in the above table with the duration of the same infestations given in Table 2, Appendix, it is noted that all the latter are longer. The difference for the infestation made February 29 is 10 days; for both April 4 and May 23, 12 days. The reason for tin's great differ- ence is not clear. It may be due to one or several causes, such as larva? remaining on the cattle for some days without attaching them- selves (this has been noticed in several instances) or ticks after the first and second molt not reattaching immediately or becoming dislodged and later reaching the host again. OBSERVATIONS ON THE MOVEMENT OF TICKS AFTER THE FIRST AND SECOND MOLT. Ransom 17 (1906, p. 5) pointed out the fact that Ifargaropus annitfatus, though remaining on the host, must reattach itself after the first and second molt just as other species do which drop from their host and molt on the ground. Hunter and Hooker 12 (1907, p. 29) state that repeated careful observations show that they do not actu- ally detach themselves at either molt. As this question has a more or less important bearing on the dissemination of ticks, and also, pos- sibly, the transmission of Texas fever, as pointed out by Ransom " (1906) , some observations were made along this line. Since the cuticle shed at molting remains attached to the skin of the host for some time thereafter, particularly following the second molt, it is an easy matter to determine whether the rostrum of the tick is embedded at the origi- nal point of attachment or elsewhere. The following observations indicate that reattachnient may take place after both the first and the second molt. Xot many specific observations were recorded with regard to the movement of young females, but general observations such as are recorded for August 7 were made at various times. The nymphs referred to below were marked early in their larval stage by clipping the hair surrounding them and were observed daily. CHANGE OF LOCATION AFTER THE FIRST MOLT. January 10, 1908, one newly molted nyuiph reattached 6 mm. from original point of attachment of larva. January 11. three newly molted nymphs reattached 3 to 6 mm. from original point. May 28, one nymph just molted reattached 3 mm. from original point. May 29, one nymph just molted reattached 8 mm. from original point. May 29, two nymphs just molted reattached 2 mm. from original point. May 29. four nymphs just molted reattached 4 mm. from original point. May 30, two nymphs just molted reattached 2 mm. from original point. May 30. six nymphs just molted reattached 4 mm. from original point. DISTINGUISHING MALE AND FEMALE NYMPHS. 27 CHANGE OF LOCATION AFTER SECOND MOLT. On July 18, 1907, a cow was infested with larvae. August 7, all the nymphs had molted. No females could be found that had wan- dered any great distance. In many instances, however, females were found located a fraction of a millimeter to 1 mm. posterior and several millimeters to one side of the place where previously attached. In the case of a cow infested August 17, 1907, on September 4 a newly molted female was observed attached 3 mm. to one side of its nymphal skin. In the case of a cow infested November 19, an unattached newly molted female was observed December 19. She was in the hair just above a male which was attached beneath a nymphal skin. On December 20 the female was found attached near the male. EARLY DISTINGUISHING OF FEMALE NYMPHS BY MALES. Some interesting observations were made which show how early the male tick may distinguish a nymph as a female and locate beneath it. On November 19, 1907, a cow was infested with larvae. Novem- ber 28, three males belonging to a previous infestation were found on the right side of the dewlap, and on November 29 and December 2 two more were found, making five in all. On the latter date two of them were located beneath nymphs, and on December 3 and 4 two more located themselves beneath nymphs. December 5 the first male nymphs of the new infestation molted. They \vere located on the posterior part of the body. December 6 the male of the previous in- festation that had not sought a nymph had disappeared and a male was found beneath a nymph on the opposite side of the dewlap. This was very likely the male of the previous infestation which had disappeared from its former location, as none of the nymphs of the new infestation had molted on this region of the body. The nymphs selected by the five males molted from December 9 to 16 and proved to be females. As observed in this case, therefore, female nymphs were sought out by males 13 to 17 days after the former had been placed on a cow as larvae, and 3 to 7 days or more before they molted the second time. EXPERIMENTS IN TRANSFERRING TICKS ON CATTLE. The following experiments were undertaken for the purpose of determining whether ticks which have accidentally dropped to the ground after molting or have been dislodged in some manner will reattach and develop, provided they reach a host. Ransom n (1906) showed that ticks removed shortly after the first and second molt, or just previous to the second molt, and permitted to molt in the 28 BIOLOGY OF THE TEXAS-FEVER TICK. laboratory will reattach themselves. Hunter and Hooker 12 (1907), after repeated attempts, succeeded in getting two ticks to reattach One was a female one-half engorged and the other an adult which molted in the laboratory. The former remained attached six days and then released its hold, although not fully engorged. It deposited several hundred eggs, which failed to hatch. The failure to hatch was not attributed to the reattachment of the tick. Experiment No. 1. December 7, 1907, a female recently molted was removed and placed on the dewlap. December 8, female had taken hold. December 13, female was still present. No further record. Experiment No. 2. December 8, a recently molted female was removed and placed on the outside of the left ear. December 9, tick had disappeared. Experiment No. 3. December 9, a female was removed and placed on the median line between the shoulders. December 10, female had taken hold. A male was placed with it. December 11, male had disappeared. December 13, a male had located beneath the female. December 14, male had disappeared. December 17, female was shriveled. Experiment No. 4- December 14, removed a female one-sixth grown and placed it on the median line between the shoulders. December 15, female had disappeared. Experiment No. 5. January 22, 1908, removed four females recently molted and placed them on the escutcheon of a cow free from ticks. January 23, two of the ticks had attached themselves. The others had disappeared. January 25, one tick had disappeared. February 14, 'the remaining tick dropped from host, but died without depositing eggs. Experiment No. 6. January 24, transferred two young females to a new host. January 25, ticks had disappeared. Experiment No. 7. January 27, transferred three females just molted to a cow. They were removed as nymphs January 25 and molted January 27. They were placed on the escutcheon and in about half an hour had apparently attached themselves. January 28, ticks had disappeared. Experiment No. 8. January 30, placed a female just molted on a cow. Female was removed as a nymph January 25 and kept in the laboratory. Molted January 30. January 31, tick still present. February 2, tick had disappeared. Experiment No. 9. February 23, placed a female, which molted in the laboratory February 22, on the escutcheon of a tick-free cow. February 24, female had dis- appeared. Experiment No. 10. February 26, placed two females, which molted in the labora- tory February 24 and 25, on the escutcheon of a cow. At the end of 30 minutes they had apparently attached themselves. February 27, ticks had disappeared. Experiment No. 11. March 2, a female which was removed February 24 and molted in the laboratory March 1 was placed on a cow. At the end of three hours it was observed attached to the udder. March 4, tick had disappeared. Experiment No. 12. March 5, placed two females on the dewlap of a cow. They were removed as nymphs on February 24 and March 2 and molted in the laboratory March 5. March 6, ticks had disappeared. Experiment No. 13.- March 7, placed two females on the escutcheon of a cow. They had been removed as nymphs March 2 and 4 and molted March 7. March 8, ticks had disappeared. Experiment No. 14. March 9, placed a female, which was removed as a nymph March 2 and molted March 8, on the left shoulder of a cow. March 10, tick had dis- appeared. BEARING UNFERTILIZED FEMALES. 29 Experiment No. 15. March 18, placed three females on the flank of a cow. They had been removed as nymphs March 17 and molted March 18. They had disappeared half an hour later, apparently having been licked off. Experiment No. 16. March 19, three females, collected as nymphs March 17 and molted March 19, were placed on the neck of a cow. March 20, one tick waa attached to the shoulder, one to the dewlap, and the other had disappeared. March 21, the tick on the shoulder had disappeared. March 29, tick was about one-third engorged. April 1, tick was dead. Experiment No. 17. March 26, placed a female, which was collected as a nymph March 17 and molted March 26, on the neck of a cow. The tick disappeared the same day. Experiment No. 18. April 1, two females, which were collected as nymphs March 17 and molted March 31 and April 1, were placed on the neck of a cow. April 2, ticks had disappeared. Experiment No. 19. April 2, placed a female, which was collected as a nymph from a horse and molted April 2, on neck of a cow. April 4, tick was present. April 5, tick had disappeared. In the above experiments 32 ticks, shortly after the second molt, were applied with special care. Twenty-four of them disappeared either on the same or the following day and 8 remained attached for periods ranging from 2 to 23 days. The one that was attached for 23 days (Experiment No. 5) became nearly engorged and dropped, but failed to deposit eggs. None of the remainder approached engorgement. Two of them died attached to the host, while the rest simply dropped off. Unfortunately no tests were made with ticks in the stage just after the first molt. It seems likely that ticks in this stage, on account of their smaller size, would attach themselves with much greater facility and develop to maturity more frequently than do adult females. A female one-sixth grown, mentioned in Experiment No. 4, failed to attach. In addition to this test, on April 13, 1908, five females, which had just been collected from a horse, ranging in size from just after the second molt to one-sixth grown, were placed on a cow, but none of them became attached. EXPERIMENTS ON REARING UNFERTILIZED FEMALES. It is next to impossible to arrange an experiment for rearing unfertilized females that entirely excludes the possibility of error. Perhaps the most reliable method would be to obtain an animal free of all ticks and infest it with females that have molted in the laboratory. Unfortunately all the experiments described in the preceding section to rear females to engorgement by this method were unsuccessful except in the case of one female transferred to a new host shortly after molting (see Experiment No. 5, p. 28), which, however, failed to deposit eggs. In some additional work attempted along this line a different method was used. An animal free of ticks was 30 BIOLOGY OF THE TEXAS-FEVER TICK. infested with a small number of larvae. The male nymphs were removed as soon as the sexes could be distinguished. The animal was examined twice a day, but in spite of the greatest care some males escaped and were occasionally found beneath females. In such cases both were removed and destroyed. The females kept under obser- vation were examined as a rule both morning and evening. It can not definitely be asserted that they were unfertilized, since the method used did not exclude this possibility, but at no time were males found beneath them. The- results, while they prove nothing with regard to undoubtedly unfertilized females, show at least two interesting things which will be mentioned below. April 19, 1908, a cow was infested with larvae. About one hundred were placed on the right side of the neck and the same number on the inside of the left thigh. All the nymphs that, so far as could be judged, were males were removed as soon as possible. On May 12 a female with a male beneath her was removed. Both were destroyed. May 22 a female dropped. It was not as large as an ordinary engorged female. Length 8 mm., width 5 mm., very thin in the dorso- ventral axis, color yellow. This tick began to oviposit May 27. The eggs developed white spots but failed to hatch. On May 24 one female dropped but could not be found. On May 26 another female dropped and was lost. No more ticks were collected from this animal. A cow was infested May 27. Larvae were placed on the escutcheon and right side of neck. Male nymphs were removed as soon as possible but some males escaped. June 20, removed a fully engorged female beneath which a male was never seen. Oviposition began June 24. Eggs hatched. June 22, removed a fully engorged female beneath which a male was never seen. Oviposition began June 24. Eggs hatched. June 26, a fully engorged female dropped. A male was never observed with it. Oviposition began June 29 and eggs hatched . June 26-27, night, a female nearly engorged dropped. A male was never noticed with her. Oviposition began June 29 and the eggs hatched . June 29, removed two females nearly engorged; males were never seen with them. Both oviposited and though the white urinary vesicle appeared in the. eggs not more than half a dozen hatched. July 18, removed a female two-thirds engorged. Eggs did not hatch. July 24, removed the last two females. They were not fully engorged and had grown very slowly. One died without ovipositing and the other laid a normal number of eggs but these failed to hatch. From the above observations it can be concluded that females which at least have not had males with them for any length of time (and possibly not at all) will as a rule deposit a normal number of viable eggs. It should be mentioned that Morgan 13 (1899, p. 129) records observations on a presumably unfertilized female which laid viable eggs. Another thing indicated is that the parasitic period may be prolonged by excluding males, and in consequence of this the period that an animal remains infested is increased. In the case of the animal infested May 27, the duration of the infestation was 58 days or about one and a half times as long as occurred in the case of a cow infested May 23 of the same year. That the adult period is not THE OCCURRENCE OF DEAD TICKS. 31 always prolonged, however, is indicated by the experiment with a newly molted female that was transferred to an animal January 22 and dropped February 14, after an adult period of 23 days (Experi- ment No. 5, p. 28). This comes within the range (8 to 33 days) of the adult period obtained at about the same time on another animal (Table 2, Appendix) . The tick obtained from the cow infested April 19 remained on the cow 33 days and the one that dropped May 26, 37 days, which is 5 days and 1 day less, respectively, than the dura- tion of an infestation of another animal made April 4. THE OCCURRENCE OF DEAD TICKS ON CATTLE. Dead ticks are frequently found attached to cattle. In some instances, especially in the case of partially or fully engorged females, they have clearly been crushed by the host rubbing or coming in contact with fences, buildings, etc. In man}' instances, however, dead ticks are found that have not been injured in this manner, and a microscopical examination of a number of such ticks failed to reveal a fungus or anything that might have caused death. In observations made from November 6, 1907, to March. 26, 1908, on animals used in the life-history studies, dead nymphs were noticed most frequently, females next, and only one male and one larva were found dead. The dead ticks did not occur uniformly over the entire body. The greater number were foil ml on the neck and shoulders, and then in the order named, on the tail, dewlap, vulva, and flank. The following is a record of dead ticks found on cattle: November 6, 1907, one nymph on tail. November 10, one nymph on tail. Decem- ber 6, one nymph on side of neck. December 14, one nymph on side of neck. De- cember 30, one nymph on dewlap. February 1, 1908, one nymph near vulva. Feb- ruary 14, one nymph on neck. February 20, female one-sixth grown, on shoulder. February 21, three nymphs on neck. February 22, one female on neck. February 23, two nymphs on neck. February 26, female, nearly grown, at root of tail. February 27, two nymphs on neck. March 5, one larva on shoulder. March 17, one nymph on neck. March 19, one nymph on shoulder. March 19, one male on neck. March 24, one nymph on dewlap. March 25, a female attached near the edge of a pustule on the right flank. March 26, female about one-third down on tail. She had a male beneath her. HOST RELATIONS OF THE CATTLE TICK. Ixodes annulatus ( M. annulatus) was first reported by Say (1821) from a deer (Cervus virginianusCariacus amcncanus] from east Florida. There are specimens in the collection of the zoological laboratory of this bureau collected from a deer in Santa Barbara County, Cal., and at San Simeon, San Luis Obispo County, Cal. Besides cattle, this tick occurs frequently on horses and mules running on infested pastures. Hunter 11 (1907) reports the tick on sheep (Oris aries) in Jackson, Calhoun, and Victoria Counties, Tex. During the summer and fall of 1907, in the course of the work upon which the 32 BIOLOGY OF THE TEXAS-FEVER TICK. present paper is based the cattle tick was collected from sheep at the Alabama Experiment Station, Auburn, and also in Wilcox County, Ala. There are specimens in the zoological laboratory of this bureau from a goat (Capra Tiircus) collected in Elmore County, Ala. Ransom 17 (1906) in an account of an experimental infestation of a cat reports ticks present in the larval and nymphal stage. Only one nymph molted a female that never became engorged. Males and females that molted in the laboratory attached themselves to a tame rabbit, but the females failed to develop further. Din- widdie 9 (1908) reared experimentally the cattle tick on a dog. The females failed to reach the usual size but deposited viable eggs. In the course of the investigations reported in the present paper larvae were applied to the rabbit, cat, dog, and sheep. INFESTATION EXPERIMENTS ON RABBITS. Experiment No. 1. A white rabbit was infested July 25, 1907, with larvae hatched June 28-July 13. July 26, one larva attached to ear; four or five found crawlin'g about through the hair. July 27, five larvse found attached to body and ears. July 30. one of the larvae found on ear continues to develop; one on the body dead, having developed very little. August 1, one larva in the act of molting. August 6, a nymph found on ear. August 12, nymph on ear still present, but not developing. A male nymph had molted. August 17, no ticks could be found. Experiment No. 2. August 19, 1907, white rabbit infested with larvae hatched June 28-July 13. August 20, many larvae found attached to the ears. August 26, one larva found on tip of right ear. August 29, one nymph found on inside of the tip of the right ear. September 4, nymph still present. September 9 and 16, no ticks could be found. Experiment No. 3. September 25, 1907, white rabbit infested with larvae, the progeny of ticks collected August 16 from a horse. October 8. no ticks could be found. Experiment No. 4- December 12, 1907, placed two females recently molted on a white rabbit. The rabbit was also infested with larvae. December 13, no ticks present. December 14, placed two more females recently molted on the rabbit. December 15, the two transplanted females have disappeared. December 19, 30, and January 17, 1908, no ticks present. Experiment No. 5. January 20, 1908, a black and white rabbit infested with larvae. Examinations made January 22. 30, and February 11 revealed no ticks. Experiment No. 6. March 2, 1908, a black and white rabbit infested with larvae. March 4, three dead larvae on the ears two attached and one in the hair. Two live larvae seen crawling over the hair of the head and face. March 13, two dead larvae noted. Neither showed any development. March 27, no ticks present. Experiment No. 7. June 18, 1908, white rabbit infested with larvae. July 2, four nymphs and a female just molted located on the ears. July 6, female had disappeared. All the nymphs were dead. Experiment No. 8. June 18, 1908, a white and gray rabbit was infested with larvae. July 11, three dead nymphs were found on ears, one in stage of molting. A nymphal skin was attached to the right ear. but the tick that had issued from it could not be found. It is evident from the above experiments that the rabbit is not an appropriate host for the cattle tick. Out of a large number of HOST RELATIONS OF THE CATTLE TICK. 33 larvae placed on each rabbit none in sonic cases, in others compara- tively few, attached themselves. It also appears that adults either resulting from nymphs dislodged from cattle, or themselves dislodged from cattle, would not be likely to attach to a rabbit in case an opportunity were presented. Larvae, nymphs, and adults (males and females) were reared on rabbits, but in no case did females develop beyond the second molt. The blood of the rabbit, or something else peculiar to the animal, is unfavorable to the tick. This is evidenced by the fact that many of the larvae and nymphs die without reaching the point of molting. It seems possible, however, that in rare cases females might attain partial or complete engorgement on rabbits, but the chances against the tick on the rabbit are so great that such a possibility seems negligible for all practical purposes. In the above experiments only tame rabbits were used. An attempt was made to raise a wild rabbit in captivity for use in the experiments, but this was unsuccessful. A number of wild rabbits obtained in the vicinity of Auburn, Ala., and in Wilcox County, Ala., were examined for cattle ticks with negative results. Farmers and stockmen in the South frequently state that they have found cattle ticks on wild rabbits, but observation and experiment tend to show that these must be other species of ticks, probably most commonly Ilxmaphysalls leporis-palustris. INFESTATION EXPERIMENTS ON A CAT. Experiment No. 9. July 24, 1907, a kitten was infested with larvae hatched June 28-July 13. July 25, one larva was found attached to the inside of thigh. July 26, larva on thigh still present and another located on left ear. July 29, larvae still present. July 31, larva on thigh molted. August 6. nymph still present. August 10, nymph disappeared. August 17, no ticks found. Experiment No. 10. August 19. kitten infested with larvae hatched June 28-July 13. August 20, a few larvae attached to the ears and abdomen. Examinations on August 26, 30, and September 4 revealed no ticks. Experiment No. 11. A third infestation of the kitten was made December 12 without result. It appears so far as the above experiments go that the cat is even a less favorable host than the rabbit. INFESTATION EXPERIMENT ON A DOG. Experiment No. 12. A dog was infested August 30, 1907, without result. INFESTATION EXPERIMENTS ON SHEEP. Seven attempts were made at various times to infest sheep with the tick, and six of these were unsuccessful. In the case of one of the unsuccessful attempts, made May 15, 1908, the animal was shorn on a In July, 1910, 20 cottontails and 6 jack rabbits were shot on the Rincon Ranch. Gregory . Tex., and examined for cattle ticks, with negative results. The rabbit tick (Ilsrmaphyaalis leporis-palu.*/ris) was found on both jacks and cottontails, but was much more abundant on the former. 34 BIOLOGY OF THE TEXAS-FEVER TICK. the previous day to allow the larvae to reach the skin with greater ease. In another, made September 25, the progeny of females matured on a horse were used. The record of the one infestation that was partially successful is as follows : July 24, 1907, a sheep was infested with larvae hatched June 28-July 13. July 27, several larvae were attached to the ventral surface of the body. August 10, one female tick a little over one-fourth grown was located on theoutside of the left ear. August 12, tick had disappeared. There was a bloodstain where the tick had been attached, sug- gesting that it may have been crushed. In two of the negative experiments dead larvae were found in the wool and also attached to the skin. At each infestation thousands of larvae were applied, and, in most cases, to all parts of the body. The very small number of larvae that attached themselves indicates that sheep are not favorable hosts for the tick. The presence of dead larvae seems to indicate that there are conditions on the surface of the body or substances in the skin and blood unfavorable to the tick. THE NATURAL OCCURRENCE OF THE CATTLE TICK ON SHEEP. In order to determine to what extent, under natural conditions, sheep serve as hosts for the cattle tick, some field experiments were carried out, and in addition to this a considerable number of sheep running on infested pastures were inspected. In one of the field experiments six native sheep were allowed to run with two cattle on an infested pasture containing about 4 acres, from July 18, 1907, to November 6 of the same year. No ticks were found at any time on the sheep, although the two cattle carried a moderate infestation until shortly before the close of the experiment, when the weather had become cool. In a second experiment six native sheep were allowed to run alone on an infested pasture similar to the above from July 18 to November 26, 1907. A ram and ewe were carefully examined on September 7. The ewe was free of ticks and the ram had six ticks, as follows : One engorged female, two males, and a dead female shortly after the sec- ond molt, on the neck, one female about one-eighth grown on the outside of the upper portion of one fore leg, and another female one- sixth grown on the abdomen where hair was present. The engorged female was unattached, but entangled in the wool in such a manner that it could not drop from the host. It had been in this condition for several days, as it had begun to oviposit. All of the sheep were examined with great care on November 26, when the experiment was closed, and were found free of ticks. Through the kindness of Prof. D. T. Gray it was possible to inspect sheep for cattle ticks at the experiment station at Auburn. The sheep were running on an infested pasture, mostly woodland, along with a few cattle. HOST RELATIONS OF THE CATTLE TICK. 35 On September 26, 1907, five sheep were subjected to a hand inspec- tion and two were found infested. A native ewe had a female tick on its ear; and a Dorset ram carried a number of males, females, and one nymph. Some of the males were dead. They were unattached and located in the wool. One female just after the second molt had a male beneath her. The largest female collected was possibly a little more than one-sixth grown. Most of the ticks were located on hairy parts of the body, especially the legs. On one native ewe two dead larvae were found. On October 3, 12 native ewes and the Dorset ram in the above flock were inspected. The ewes were free (one harbored a dead larva) and the Dorset ram harbored two males. The skin of 7 of the ewes was oily, that of the other 5 was moderately oily, and that of the Dorset ram was not oily. On October 12 the ram was inspected again. The wool and skin were very free from oil. Ticks were found as follows: Two females one-third and one-sixth grown with males beneath them on one hind leg a short distance above the hoof; a fe- male just after the second molt on the posterior surface of the thigh with a male situated some little distance below it; a female one- fourth grown with a male, located on the scrotum; and a dead male in the wool. On October 14 one of the females on the leg and the one on the scrotum had become nearly engorged and were removed. The former was crushed in removing. On October 16 another female nearly engorged was removed from the hind leg. Both of the uninjured ticks laid viable eggs. On November 12 to 13, 1907, 36 sheep, principally grade South- downs, in Wilcox County, Ala., were subjected to a careful hand inspection. These sheep had been running continuously during the summer and fall with 240 head of cattle that were grossly infested with ticks prior to October 24, when they had been dipped. All the sheep were in high flesh. All but one of them were free from ticks. Thirteen of the sheep had wool that was not oily; 14 had moderately oily wool; and S had oily wool. The one infested, a ram with moderately oily wool, had a female tick one-half grown on the hairy portion of the scrotum. On November 14 to 18 a flock of 125 sheep in the same locality was inspected. They had been running continuously during the summer ami fall in a pasture of several hundred acres with over 200 cattle which, at the time of the inspection, were grossly infested with ticks. Three sheep, or about 2 per cent of the entire flock, were found in- fested with live ticks. Dead ticks alone were found on 31 sheep, or 25 per cent of the flock. Rams were the hosts for the live ticks in all three cases, and in the case of two of them the ticks were attached to the scrotum. One ram had two ticks, a female just after the second molt and another one-third engorged; another had but one tick, a 36 BIOLOGY OF THE TEXAS-FEVER TICK. female, newly molted, and the remaining one had a half-grown female on the hairy portion of the leg. The wool of the first was moderately oily and that of the other two not oily. Dead ticks were found on 32 sheep. This includes one that also had live ticks. Ticks in the larval stage were found on all these sheep, and in addition one dead male was present in each of four instances. The larvae were attached to the skin of the woolly regions of the body. When they were removed a small scale of epidermis of the host was brought way with the mouth parts, indicating that the larvae had actually taken hold. The males were found unattached in the wool. The condition of the wool of the entire flock was noted for the purpose of determining, if possible, whether the amount of oil on the wool plays any part in preventing ticks attaching to sheep. Eighty-six sheep, or 69 per cent, had wool not oily; 38 sheep, or 30 per cent, had wool moderately oily; and 1 sheep, or about 1 per cent, had oily wool. Twenty-seven per cent of the first class, 29 per cent of the second class, and zero per cent of the third class of sheep carried ticks either dead or alive. From this it would appear that the relative amount of oil on the wool bears no important relation to the presence of ticks. Summarizing the results of the observations on the natural infesta- tion of sheep, it may be said that live ticks were found on the ears, neck, legs, abdomen, and scrotum. In no case were they present in great numbers. Rams seem to be much more favorable hosts than ewes. Taking into account all the inspections made, ticks were found on rams eight times and on ewes twice. In view of the large number of ewes inspected as compared with the rams this result can not be considered accidental. THE PROGENY OF FEMALES MATURED ON SHEEP NONINFECTIOUS. As previously stated, two of the female ticks that matured on sheep laid viable eggs. One collected October 16, 1907, began to lay October 23, 1907; hatching began April 9. and ended April 17, 1908. The other, collected October 14, 1907, began to lay October 22 and hatching began April 11, 1908. On May 2, 1908, the larvae from the above ticks were placed on a northern cow (No. 603) about 10 years old, at the Bureau of Animal Industry Experiment Station, Bethesda, Md. Six hundred and forty-three females matured, but the cow continued well and in good condition, the temperature and number of erythrocytes remain- ing normal. On July 15, 1908, the progeny of ticks collected from the above cow, May 28, 1908, were placed on two northern cattle, a bull (No. 585) and a heifer (No. 591), each about 1 year old. The temperature of both animals remained normal. MAN AS A HOST OF THE TICK. 37 On September 14, 1908, and a number of times thereafter three northern heifers (Xos. 582, 583, 584), each about 1J years old, were infested with the progeny of ticks collected from bull No. 585, August 8, 1908, but none of them developed fever. The above experiments show that the larvae were noninfectious, but it is not known, of course, whether the two females of which they were the progeny belonged to an infectious brood, and further- more, if this were the case, it could not be known whether the two females were infectious or not in their larval state, since it is fair to assume that only a certain per cent of the progeny of infectious ticks are infectious. Since, however, the particular sheep from which they were collected ran on a pasture where infectious ticks undoubtedly occurred and since ticks had been observed on this sheep a number of times, the chances are, if the Texas-fever parasite could survive in the blood of sheep, the blood of this one would have been infectious and at least some of the progeny of the two females would have proved infectious. MAN AS A HOST OF THE TICK. So far as known the cattle tick in its larval stage does not attack man. Persons handling these larvae in the laboratory and passing through fields infested with only cattle ticks are not attacked. Ran- som 17 (1906) reports two experimental and one accidental attachment of adults that molted in the laboratory. Below are records of the attachment of ticks to man, obtained in the course of the present investigations. On June 18, 1907, 11.30 a. m., a female specimen of Margaropus annulatus about one-third engorged was placed on the calf of the leg. Shortly after noon it attached itself. It was removed June 19, 2.45 p. m., having drawn blood for more than 24 hours. At this time it- had attained two-thirds of the usual size of an engorged tick. The place where it was attached became highly inflamed, acquiring a purplish color. On August 13, 1907, a female that had molted in the laboratory on August 7 was placed on the thigh. The tick attached itself, but thereafter changed its location many times. It was present for several days and then. disappeared. On August 27 a nymph, shortly after the iirst molt, was placed on the arm. It attached itself and remained so for several hours and then disappeared, probably having been dislodged by the clothing. 38 BIOLOGY OF THE TEXAS-FEVER TICK. BIBLIOGRAPHY. The following list contains only works referred to in this bulletin: 1. COTTON, E. C. Tick eradication. The life history and habits of the North American fever tick with special reference to eradication. Tennessee Agricul- tural Experiment Station of University of Tennessee, Bulletin 81. Knox- ville, 1908. 2. CURTICE, COOPER. The biology of the cattle tick. Journal of Comparative Medicine and Verterinary Archives, vol. 12, No. 7, pp. 313-319. New York, July, 1891. 3. About cattle ticks. Journal of Comparative Medicine and Veterinary Archives, vol. 13, No. 1, pp. 1-7. New York, January, 1892. 4. The cattle tick (Boophilus boi'is Rileysp.). Texas Agricultural Experiment Station, Bulletin 24. Bryan, 1892. 5. On the extermination of the cattle tick and the disease spread by it. Journal of Comparative Medicine and Veterinary Archives, vol. 17, No. 9, pp. 649-655. Philadelphia, September, 1896. 6. The cattle-tick plague, and what may be done to prevent it. Southern Planter, vol. 58, No. 1, pp. 24-27. Richmond, January, 1897. 7. DALRYMPLE, W. H., MORGAN, H. A., and DODSON, W. R. Cattle tick and Texas fever. Louisiana Agricultural Experiment Station, Bulletin 51, Second series. Baton Rouge, 1898. 8. DINWIDDIE, R. R. Animal parasitism. Some Texas fever experiments, Arkan- sas Agricultural Experiment Station, Bulletin 20. Little Rock, 1892. 9. Notes on the cattle tick and the tick fever of cattle. Arkansas Agricultural Experiment Station, Bulletin 101. Fayetteville, 1908. 10. GRAYBILL, H. \V. Methods of exterminating the Texas-fever tick. United States Department of Agriculture, Farmers' Bulletin 378. Washington, 1909. 11. HUNTER, W. D. Note on the occurrence of the North American fever tick on sheep. United States Department of Agriculture, Bureau of Entomology, Circular 91. Washington, 1907. 12. HUNTER, W. D., and HOOKER, W. A. Information concerning the North Ameri- can fever tick, with notes on other species. United States Department of Agriculture, Bureau of Entomology, Bulletin 72. Washington, 1907. 13. MORGAN, H. A. Ticks and Texas fever. Louisiana Agricultural Experiment Station, Bulletin 56, second series. Baton Rouge, 1899. 14. The cattle-tick situation. Proceedings of the Society for Promotion of Agricultural Science, Twenty-fourth Annual Meeting, pp. 72-74. Washing- ton, 1903. 15. The Texas fever cattle-tick situation and the eradication of the tick by a pasture rotation system. Louisiana Agricultural Experiment Station, Bulletin 82, second series. Baton Rouge, 1905. 16. NEWELL, WILMON, and DOUGHERTY, M. S. The cattle tick (Boophilus annulatus). Studies of the egg and seed-tick stages. A simple method of eradicating the tick. Louisiana State Crop Pest Commission, Circular 10. Baton Rouge, 1906. 17. RANSOM, B. H. Some unusual host relations of the Texas-fever tick. United States Department of Agriculture, Bureau of Animal Industry, Circular 98. Washington, 1906. 18. SCHROEDER, E. C. A note on the vitality of the southern cattle tick. United States Department of Agriculture, Bureau of Animal Industry, Sixteenth Annual Report, 1899, pp. 41-42. Washington, 1900. BIBLIOGRAPHY. 39 19. SCHKOEDER, E. C. Notes on the cattle tick and Texas fever. United States Department of Agriculture, Bureau of Animal Industry, Twenty-second Annual Report, 1905, pp. 49-70. Washington, 1907. 20. SCHROEDER, E. C., and COTTON, W. E. The growing of noninfected ticks and afterwards infecting them. United States Department of Agriculture, Bureau of Animal Industry, Sixteenth Annual Report, 1899, pp. 33-41. Washington, 1900. 21. The persistence of the Texas-fever organism in the blood of southern cattle. United States Department of Agriculture, Bureau of Animal Industry, Twenty second Annual Report, 1905, pp. 71-78. Washington, 1907. 22. SMITH, THEOBALD, and KJLBORNE, F. L. Investigations into the nature, causa- tion, and prevention of Texas or southern cattle fever. United States Depart- ment of Agriculture, Bureau of Animal industry, Bulletin 1. Washington, 1893. APPENDIX. TABLE 1. Individual records of ticks used in experiments. Num- ber of tick. Date col- lected. Number of eggs de- posited. Preovi- position period. Ovi- position period. Incuba- tion pe- riod. Hatch- ing pe- riod. Mini- mum longev- ity. Maxi- mum longev- ity. Entire time. Per cent hatched. I... 2 1907 June 1 do. 630 2,276 Days. Days. 4 10 Days. 24 to 32 24 to 31 Days^ 11 Days. 13 9 Days. 50 46 Days. 83 79 86 94 3. do. . 877 7 5 24 to 32 5 52 85 x 93 4 ..do.... 3,095 6 13 23 to 31 12 4 48 83 91 5 do 1,036 7 3 25 to 34 11 15 54 88 93 6 a... do . 2,150 9 9 23 to 31 10 7 65 100 73 7 a... . do 2,614 6 14 22 to 33 10 3 55 90 95 8 9. July 1 .do... . 3,000 3,562 4 4 17 18 20 to 25 20 to 25 11 17 22 16 ' 82 62 112 91 % 96 10... ...do.... 1,863 4 5 20 to 27 9 20 85 112 97 11. do 3,515 4 20 19 to 25 15 16 103 95 12 13a.... ...do. .. ...do.... 1,858 3,820 4 4 4 16 20 to 25 19 to 25 4 15 24 20 55 67 82 98 90 94 14<J do 2,814 3 10 20 to 25 9 19 79 109 % 15 16 Aug. 1 . .do 3,683 2,972 3 3 15 18' 20 to 25 20 to 24 8 15 22 10 160 187 187 218 90 96 17 do 2,536 3 15 20 to 25 15 4 15'-> 180 97 18 19 ...do ...do 2,820 2,700 3 3 17 12 19 to 25 20 to 27 16 14 9 11 170 192 198 221 98 97 20a ... 21o.... 22 23. . ...do.... ...do Aug. 31 do . 1,851 2,267 2,809 2,699 3 3 3 3 13 19 19 18 20 to 25 21 to 26 28 to 54 29 to 48 12 14 39 31 6 9 5 13 144 192 224 204 172 221 258 240 98 94 83 95 24. ... ...do.... 2,049 4 15 30 to 50 31 7 1% 234 66 25 do. 2,266 3 19 30 to 66 49 11 219 270 57 26. .do .. 2,262 4 14 29 to 52 34 i 234 272 95 27 a do 39 4 9 ( 6 ) 28 a do 2,344 2 14 29 to 50 32 7 192 230 97 34 35... . Oct. 1 ...do.... 2,780 2,942 4 4 36 34 167 to 182 170 to 185 21 26 5 8 91 85 276 276 90 87 36 do 2,838 4 36 166 to 186 31 5 94 276 92 37. .do. . 2,570 4 37 169 to 186 25 4 92 281 77 38 ...do.... 3,383 4 35 170 to 186 24 4 99 288 82 39" do 960 6 21 173 to 188 16 3 98 281 80 40 ... 45 46 . ..do.. . . Nov. 1 do . 2,467 2,961 1,936 4 7 9 31 99 81 165 to 185 151 to 170 139 to 158 29 13 11 3 8 9 90 69 60 279 239 236 84 6 4 47. . ...do... 2,281 10 80 118 to 125 7 21 37 213 .09 48 do 991 20 118 154 25 25 200 .1 49 do . 2,855 8 151 138 to 158 13 13 76 244 4 50a ...do.... 1,985 9 82 117tol68 15 21 78 253 3 51 a . do 1,896 9 78 122 to 169 18 5 73 244 / 61 Nov 30 (c) 62 do 3,207 58 54 57 4 20 27 187 1 63 do 2,103 98 20 50 to 60 11 10 91 249 18 64. .. ..do... 3,023 38 87 51 to 68 11 7 57 215 4 65 do 357 70 40 (b) 72 Dec 29 (c) 73 .. do 3,180 63 18 56 to 66 14 13 46 181 1 74 .do. 4,272 39 63 48 to 80 25 7 73 207 35 75 do 1 970 46 37 (6) 76 77 1908 Jan. 1 1907 Dec 30 3, 173 (c) 63 24 48 to 07 14 8 69 201 25 82... 83 1908 Feb. 4 Feb. 3 4,276 3,900 28 29 39 36 48 to 65 45 to 62 26 25 4 6 99 76 189 172 81 86 a Eggs were not counted, larvae had died. 6 Eggs failed to hatch, c Did not oviposit. 40 The unhatched eggs and the larvae in each tube were counted after all the APPENDIX. 41 TABLE 1. Individual records of ticks used in experiments Continued. Num- ber of tick. Date col- lected. Number of eggs de- posited. Preovi- posilion period. Ovi- posit ion period. Incuba- tion pe- riod. Hatch- ing pe- riod. Mini- mum longev- ity. Maxi- mum longev- ity. Entire time. Per cent hatched. 84... 85 87 1908 Feb. 4 Jan. 30 .do 806 3,620 3,725 Days. 36 35 34 Days. 22 33 43 Days. 53 to 63 49 to 63 48 to 64 Days. 14 26 26 Days. 6 7 2 Days. 77 86 81 Days. 177 186 176 39 t>5 72 88<J.. . 89a. Jan. 29 do 3,269 3,718 37 37 36 41 48 to 65 47 to 65 25 18 7 21 59 64 156 156 34 14 95 98o.... 105.... 106 Feb. 27 Feb. 28 Mar. 26 do 2,302 2,925 4,559 2,680 10 8 5 6 24 36 34 24 47 to 64 45 to 62 36 to 53 43 to 53 18 27 13 12 4 2 7 7 94 80 90 98 162 143 149 155 62 96 77 78 107 . .do 2,731 8 14 43 to 52 15 12 101 161 66 108 do 3,024 5 17 44 to 53 12 11 101 159 89 109 do 4,035 6 23 39 to 53 14 6 97 155 95 liofc.. lllfr. . 1126 Mar. 29 ...do do 3,712 3,405 3.622 4 5 4 35 27 26 37 to 52 38 to 51 39 to 51 14 16 14 13 5 5 92 89 88 146 144 144 92 92 97 113 fr do . 3,796 4 25 37 to 51. 15 10 103 156 93 125.... 126 Apr. 29 ...do 4,244 3,966 4 6 22 19 24 to 36 26 to 34 18 12 5 6 113 89 152 128 96 33 127 do 3,929 6 25 24 to 33 18 4 118 156 98 128 do . 4.385 4 24 25 to 36 16 9 116 156 96 129 .do 5,105 6 24 24 to 33 18 7 116 154 84 130 &. . ...do 3,942 6 23 24 to 33 17 9 105 145 98 1316.. ...do... 3,949 7 19 23 to 33 13 10 93 133 98 132 b . . 1336. ...do .do 4,035 3,246 6 7 27 21 24 to 33 24 to 32 17 18 6 10 128 79 173 122 98 93 134 o .. ..do 6 24 23 to 33 22 5 92 131 135 a. . ...do... 5 22 25 to 34 19 11 % 138 136 a do G 21 24 to 33 16 6 91 131 137 a do. 6 26 25 to 34 17 19 94 131 138 c. . ...do 22 24 to 32 20 108 149 a Eggs were placed in test tubes directly on moist sand. No water was added to the sand after the tube was made. ft Eggs were placed in test tubes provided with two cardboard disks. No water was added to the sand after the tube was made. c Eggs were floated on water in test tubes. 42 BIOLOGY OF THE TEXAS-FEVER TICK. ~ a OOOO COIN'WCO'O |2222 22222 -gee" 1 C^ft > o o o o ooooo o to << "3 2 N i-l IN * tin S-s. a a 2 o ,26 ai o> g