Issued September 9, 1912. U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF ANIMAL INDUSTRY.— Bulletin 152. A. D. MELVIN, CiiiEi^ or Bureau. B^*2 STUDIES ON THE BIOLOGY OF THE TEXAS-FEVER TICK. (SUPPLEMENTARY REPORT.). BY H. W. GRAYBILL, D. V. M., Assistant Zoologist, Zoological Division, AND W. M. LEWALLEN, Agent in Tick Eradication, Bureau of Anivial Industry. WASHINGTON: GOVERNMENT PRINTING OFFICE. 1912. -ti^. Glass SF 5 33 Book TVs- G^ ^ ^ I^siu'il September 9, 1912. U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF ANIMAL INDUSTRY.— Bulletin 152. A. D. MELVIN, Chief of Bureau. STUDIES ON THE BIOLOGY OF THE TEXAS-FEVER TICK. uui> (SUPPLEMENTARY REPORT.) ., - —- BY H. W. GRAYBILL, D. V. M., Assistant Zoologist, Zoological Division, AND W. M. LEWALLEN, Agent in Tick Eradication, Bureau of Aiiimal hidustry. WASHINGTON: GOVERNMENT PRINTING OFFICE. 1912. ^^ 6<^^^^ < BUREAU OF ANIMAL INDUSTRY. Chief: A. D. Melvin. Assistant Chief: A. M. Farrington. Chief Clerk: Charles C. Carroll. Animal Husbandry Division: George M. Kommel, chief. Biochemic Division: M. Dorset, chief. Dairy Division: B. H. Rawl, chief. Field Inspection Division: R. A. Ramsay, chief. Meat Inspection Division: Rice P. StjSDDOM, chief. 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 IIassall, Harry W. Graybill, Maurice C. Hall, and Howard Crawley. JumorZooZo^isf; WiNTHROP D. Foster. ' additional copies of this publication -t\- may be procured from the Superintend- ent OF Documents, Government Printing OflBco Washington, D. C, at 5 cents per copy. LETTER OF TRANSMITTAL. L^. S. Department of Agriculture, Bureau of Animal Industry, Washington, D. C, April 25, 1912. Sir: In Bulletin 130 of this bureau there were reported the results of one year's investigations of the biology of the Texas-fever tick which were carried on during 1907 and 1908 at Auburn, Ala., by cooperation between the Alabama Polytechnic Institute and this bureau. The work was continued for another year, and I have the honor to transmit herewith a supplementary report by Dr. H. W. Graybill and Mr. W. M. Lewallen, giving the results of the second year's experiments (1908-9). As this information has a bearing on the cooperative work now being carried on by the bureau and the authorities of certain States for the eradication of the cattle tick, I recommend its publication as a bulletin of this bureau. Respectfully, A. D. Melvin, Chief of Bureau , Hon. James Wilson, Secretary of Agriculture. CONTENTS. Page. Introduetion ^ 5 Methods of study " 5 Preoviposition period 6 O viposition period 6 Incubation period 7 Hatching period 8 Longevity period 8 Entire time of nonparasitic development 9 Number of eggs laid and percentage hatched 10 Comparison of results of indoor and outdoor experiments 10 Appendix 13 STUDIES ON THE BIOLOGY OF THE TEXAS-FEVER TICK. (SUPPLEMENTARY REPORT.) INTRODUCTION. During 1907-8 the Zoological Division of tlie Bureau of Animal Industry conducted a year's experiments on the life history of the Texas-fever tick at Auburn, Ala., in cooperation with the veterinary department of the Alabama Polyteclmic Listitute. The results obtamed during the course of those investigations have been pub- lished in Bulletin 130 of the Bureau of Animal Industry. The work was continued for another year (1908-9) along the same but some- what less extensive lines. Mr. W. M. Lewallen, who assisted in the first year's work, had charge of the experiments during the second year. The second year's work was undertaken for the purpose of obtain- ing additional data on the nonparasitic periods in the life history of the tick, and to determine what variations might take place in the duration of these as a result of yearly variations in weather contUtions. METHODS OF STUDY. The methods of study employed were the same as those used the first year. The indoor experiments were conducted by the use of incubation tubes, and these were checked by outdoor experiments conducted in field plots representing natural conditions. The incu- bation tubes used were the vertical type provided with a glass tube inserted into the bottom for the puqDose of supplying the sand with moisture, shown in figure 1, Bulletin 130, Bureau of Animal Industry. The field plots were the same as those used in the first year's work (fig. 3, Bulletin 130), being 2 feet square. They were protected from the intrusion of small animals by means of a wire-netting fence. In the indoor experiments the ticks were handled the same as during the first year. Four engorged ticks were collected at the beginning of each month, and each was j)laced in a dish by itself, where it remained until oviposition was completed. At the end of every 24 hours the eggs were removed from each tick, counted, and placed in an incubation tube marked with the number assigned the tick and the date the eggs were removed. The dates when the eggs in each tube began and completed hatching, and when the first and last larvae 5 6 BIOLOGY OF THE TEXAS-FEVER TICK. died, were recorded, and finally the per cent of eggs that liatched was determined. The indoor experiments were conducted in an unheated room, the windows of which were constantly open. In the outdoor experiments two sets of plots were run, one located in a place shaded a part of the day and the other in the sun. In each plot 10 engorged females were placed. PREOVIPOSITION PERIOD. The minimum preoviposition period noted was 2 days, which occurred in the case of ticks collected in August. Ticks collected in August the first year had a minimum period of 2 days, but the mini- mum for the year (1 day) was observed in the case of a tick collected in April. The maximum period (29 days) was exhibited by ticks collected December 2, and the maximum for the first year (98 days) was observed in the case of a tick collected November 30. From the table (last column) it will be noted that the average pre- oviposition periods increase month by month from the minimum to the' maximum, and then decrease again to the minimum. A similar increase and decrease were also shown in the case of averages for the first year's experiments in the horizontal tubes, but in the case of the ticks used for the vertical-tube experiments the averages for April and June were greater than for March. Preoviposition period — Range and average length of periods. Date ticks were collected. Number of ticks. Range of preovi- position periods. Average of preovi- position periods. Date ticks were collected. Number of ticks. Rangeof preovi- position periods. Average of preovi- position periods. 190S. Augusts 4 4 4 4 4 • Bays. 2 to 4 3 to 5 5 to 11 7 to 9 17 to 29 Days. 4 8!3 25.5 i 1909. January 1 February 4 Days. 22 to 24 18 to 20- 9 to 16 9 to 10 3 ^%- September 1 October 1 19.3 November 2 April 2 r 9 8 OVIPOSITION PERIOD. The longest oviposition period noted was 82 days, observed in the case of a tick which began ovipositing in January. A tick in the first year's, experiments which began to lay eggs in January had an ovi- position period of 91 days, but the longest period was exhibited by a tick which began ovipositing in November and continued to lay eggs for 152 days. The second year the shortest period (7 days), as weU as the longest, occurred in January. The tick giving this period, however, deposited only 305 eggs, an exceptionally small number. The shortest period the first year was 3 days, and this occurred in June. The average oviposition periods for the first year increased month by month from a minimum in June to a maximum in November, and INCUBATIOX PERIOD. 7 gradually decreased again in the succeeding months. During the second year the same tendency was shown, the periods increasing from a minimum in August to a maximum in November, and then, following a sudden decrease for December, there was an increase for January and February, after wliich the decrease was regular for the remauiuig months. Oviposition period — Range and average length of periods. Month oviposi- tion began. Number of ticks. Range of ovi- position periods. Average of ovi- position periods. Month oviposi- tion began. Number of ticks. Range of ovi- position periods. Average of ovi- position periods. 1908. August 4 Days. 13 to 15 9 to 18 13 to 35 56 to 63 30 to 42 7 to 82 Days. 14.3 14.8 25.3 59.5 34.5 45.8 1909. February March Days. 37 to 59 22 to 42 26 to 32 19 to 27 11 to 19 12 to 17 Days. 46.8 33.3 September April November M^y 23 8 December June 15.8 July 1909. INCUBATION PERIOD. The range of the incubation periods of the lots of eggs laid by each tick is given in the table in the Appendix. The range of the period for the second year was 18 to 176 days, as compared with 19 to 188 days for the first year. In the table below only the periods from the time the eggs were deposited until the first eggs hatched in each lot have been used, and these are referred to for convenience as the mini- mum incubation periods. The periods to the hatching of the last eggs in each lot have been included in the table in the Appendix. The longest minimum incubation period for both the first and the second year occurred in the case of lots of eggs deposited during the month of October, being 173 days for the second year and ISO days for the first year. The shortest period for the second year was 18 days and was observed in the case of lots of eggs deposited during the month of June, wliile the lots deposited during the same month of the first year gave a minimum period of 22 days. The shortest period for the first year (19 days) was furnished by lots of eggs depos- ited during the months of July and August. By comparing the averages in the table below it will be observed that they increase from August to October and decrease for the re- maining months, except in the case of the average for July, which shows a slight increase. In case of the averages for the first year it is noted that they increase for the months of August to October and decrease for the remaining months without interruption. 8 BIOLOGY OP THE TEXAS-FEVER TICK. Minimum incubation 'period — liange and average length of periods. Month eggs de- posited. Number of lots. Range of periods. Average of periods. Month egcs de- posited. Nunlber of lots. Range of periods. Average of periods. 1908. August 52 49 49 66 21 70 Days. 20 to 30 32 to 70 141 to 173 151 to 171 139 to 15S 103 to 141 Bays. 23.1 44.8 158. 7 157. 5 150.3 121. G 1909. February March 48 170 141 90 47 51 Days. 82 to 107 5Sto 90 38 to 65 26 to 39 IS to 26 22 to 27 Days. 95 5 April November Mav 30 6 July 94 5 19:9. HATCHING PERIOD. The maximum hatching period for the second year was 52 days and for the first year 49 days, and in the case of both years tliis period belonged to a tick whose eggs began to hatch during the month of October. The shortest hatcliing period for the second year was 6 days and occurred in the case of a tick whose eggs began to hatch in JMay, wliile for the first year the minimum period for the same month was 9 days. The shortest period during the first year (4 days) fell to the month of July, It is noted by referring to the averages in the table below that those for October and February are the same, and for the remaining months, with the exception of the break shown by May, there is a decrease, month by month, of the averages. In the first year's work the averages increased from that for July to the maximum, which is for the month of October, and decreased for the remaining months, except for a slight increase for the month of June. Hatching period — Range and average length of periods. Month hatching began. Number of ticks. Range of hatching periods. Average of hatch- ing periods. Month hatching began. Number of ticks. Range of hatching periods. Average of hatch- ' ing periods. 1908. August 4 4 1 , Days. ^ 17 to 27 47 to 52 50 Days. 21.5 50 SO' 1909. March 4 20 4 8 Days. 33 to 46 IS to 21 6 to 21 12 to IS 11 to 21 Days. 39 5 October 19.3 May 13.8 1909. 16 Pebruary July 14 5 LONGEVITY PERIOD. The longest and shortest longevity periods obtained for the lots of larvae belonging to each tick are given in the table in the Appendix. The time to the death of the first larvae in each lot is referred to in the table below as 'the minimum longevity period and that to the death of the last larvae as the maximum longevity period. The longest maximum longevity period for the second year was 249 days, as compared with 234 days for the first year, and both TIME OF XONPARASITIC DEVELOPMENT. 9 occurred in the case of lots of eggs which began to hatch (hn-ing the month of October. In referring to the averages it will be noted that there is no regular mcrease and decrease to and from the maximum, and the same was noted in the case of the first year's experiments. This is no doubt due to the fact that tem- perature, while it plays some part, is not a controllmg factor in the longevity of larvje as it is in the case of the preoviposition, oviposition, hatchmg, and incubation periods. The range of the averages for the months of August to November of the second year is 104.5 to 213.7 days, w^hereas the range for the same months of the first year is 56.2 to 167.4 days. The range of the averages for the rest of the months of the second year is 63.3 to 77.6 days, as com- pared with a range of 38.6 to 73.2 for the remaining months of tho first year. Longevity period. — Range of maximum and minimum longevity and average of maximum longevity. Month lots began to hatch. Ntim- bfir of lots. Range of minimum longevity periods." Range of maximum longevity l)eriods. Average of max- imum longe\"ity periods. Month lots began to hatch. Num- Range of Range of ber minimum maximum of longevity longevity periods. lots. periods. Days. Days. 72 (i to 60 31 to 110 355 8toS7 14 to 119 ISO 7 to 85 25 to 139 50 9 to 48 9 to lOG 42 7 to 47 31 to 118 Average of max- imum longev- ity periods. 1908. August September October... November, 1909. March Days. 10 to 30 6 to 02 13 to 155 51 to 146 Days. 99 to 192 50 to 218 80 to 249 58 to 223 Days. 121.8 104. 5 21.3. 7 149.9 1909. April May June July August Days. 75.: 77. 66. 63.: 64. ENTIRE TIME OF NONPARASITIC DEVELOPMENT. The entire time for each individual tick and its progeny, i. e., the time from dropping to the death of all the larvge, is given in the table in the Appendix. The longest entire time during the second year (297 days) was obtained m the case of ticks collected September 1, while the longest period for the first year (288 days) occurred in the case of ticks collected October 1. The shortest period for the second year was 96 days and for the first year 79 days, and both occurred in the case of ticks collected the first part of June. The averages for the first year increase month by month from June to a maximum for October, and then decrease for the remaining months, except that the averages for February and ]\Iarch are the same. The averages for the second year, given in the last column of the table below, do not increase to and decrease from the maximum without deviations, as do those for the first year. 10 BIOLOGY OF THE TEXAS-FEVEE TICK. Entire time of nonparasitic development. Date engorged females were collected. Number of engorged females. Range of entire-time periods. Average of periods. Date engorged females were collected. Number of engorged females. Range of entire-time periods. Average of periods. 1908. 4 4 3 4 4 Days. 143 to 254 258 to 297 271 to 280 274 to 288 257 to 268 Days. 206.5 280 279.3 282 264.8 1909. January 1 February 4 March 1 Days. 202 to 253 204 to 230 lS5-to207 139 to 164 140 to 185 96 to 127 110 to 149 Days. September 1 October 1 218.5 198 3 December 2 May 1(?) June2(?) July 2 156.5 117 NUMBER OF EGGS LAID AND PERCENTAGE HATCHED. During the second year the minimum number of eggs laid by a tick was 305 and the maximum 4,492. The average number of eggs laid by the various lots of ticks ranged from 1,885. to 4,262. The lowest percentage of eggs hatched was 3 per cent and the highest 98 per cent. The percentage of eggs hatched in the case of ticks collected during December, January, and February ranged from 3 to 60 per cent. For the first year the minimum number of eggs laid was 357 and the maximum number was 5,105, and the averages ranged from 1,811 to 4,089. The percentage of eggs hatched ranged from to 98 per cent. Egg laying and hatching — Total and average number of eggs laid and per cent hatched. Num- Date col- ber lected. of ticks. 1908. August 5... September 1 October 1 . . November 2 December 2 Number of eggs deposited. Average number of eggs. Per cent hatched. 3,962 to 4,492 2,797 to 3,654 1,588 to 3,848 2,215 to 3,329 1,496 to 2,201 4,262 3,252 2,768 2,975 1,885 48 to 97 92 to 98 9 to 61 52 to 71 11 to 27 Date col- lected. Num- ber of ticks. Number of eggs deposited. Average number of eggs. Per cent of eggs hatched. January!.. 4 305 to 3,723 2,615 February 4. 4 1,993 to 2,970 2, March 1.... 4 l,3S0to3,361 2,352 April 2 4 1,741 to 3,065 2,476 May 11 4 3.181 to 4,178 3,679 June 22 4 1,640 to 3,003 2,180 July 2 4 2,214 to 3,710 • Ticks were collected June 2, 3, 4, and 3 to 60 11 to 41 61 to 93 86 to 95 69 to 93 60 to 97 96 to 98 Ticks were collected May 1 and 2. COMPARISON OF RESULTS OF INDOOR AND OUTDOOR EXPERIMENTS. In the next table the dates when the first eggs hatched and when all the larv£e were dead in each month's experiments, indoors and outdoors,, are given for purposes of comparison. These dates are of much practical importance in eradication work when rotation methods are employed, since the dates when the first eggs hatched are those on which ticky cattle placed on tick-free land on dates corresponding to those on which the experiments were begun will be in danger of reinfestation, and the dates on which all larvae were dead are the COMPARISON" OF RESULTS. 11 dates on which pastures from which all animals have been removed will be free of ticks. Comparison of records of vertical tubes and field plots, Auburn, Ala., 1908-9. Vertical tubes. Date females were collected. Date first eggs hatched. Date aU larvae were dead. Field plots. Date first Date females were collected. \ eggs hatched. Date all larvae were dead. 1908. Augusts September 1 October 1 November 2 December 2 1909. January 1 February 4 March 1 April2 May 1-2 June 2-5 July2 Aug. 30 Oct. 7 Feb. 25 Apr. 22 May 11 May 19 May 21 May 24 May 28 June 10 July 2 July 28 Apr. 16 June 25 July 8 Aug. 17 Aug. 27 Sept. 11 Sept. 22 Sept. 24 Sept. 13 Nov. 2 Oct. 7 Nov. 28 August 5-C. . September 1. October 1 . . . November 2. 1909. Aug. 31 Nov. 23 Apr. 19 May 10 January 1 ] May 21 February 1-4 i May 20 March 1-3 ...do.... April 2 May 26 May 1-2 June 12 June2-5 June 28 July 1-2 July 26 Apr. 3 Mav 22 June 23 Do. Julv 30 Aug. 6 Aug. 25 Sept. 11 Do. Oct. 2 Nov. 13 In comparing the length of time required foj the first eggs to hatch in the indoor and outdoor experiments it was found that for all the months except March, April, June, and July the time was longer in the outdoor than in the indoor experiments, the differences ranging from 1 to 53 days, and for the above-mentioned months the time was shorter, the differences ranging from 1 to 4 days. The longer time obtained in the majorit}^ of the outdoor experiments may be due in part to unavoidable errors in observation because of the fact that it is frecj[uently difficult to determine with certainty when the fu"st eggs hatch, smce they are scattered and some may be hidden fi'om view. In the first year's experiments practically the same results were obtained. For two of the eight months for which comparisons could be made the time was the same in the indoor and outdoor experi- ments, and for the remaining months the time was longer in the out- door experiments, the differences ranging from 1 to 22 days. In view of the fact that in the two years' experiments the time to the hatching of the first eggs was longer in the outdoor experiments than in the corresponding indoor experiments in all except four instances, in which cases the differences were comparatively small, ranging from 1 to 4 days, it seems safe to assume that indoor experi- ments, if the temperature is maintamed uear that on the outside, will be safe to follow in practical work, provided a reasonable margin of safety be allowed to cover slight variations that might occur in the direction of a shorter time for hatclimg. In the second year's work, for all months the time required for all the larvae to die was longer in the mdoor than in the outdoor experi- ments, the differences ranging from 2 to 55 days, and the average 12 BIOLOGY OF THE TEXAS-FEVEK TICK. difference being 28 days. In the first year's experiments similar results were obtained; in all but one case the periods were longer in the indoor than the outdoor experiments, the differences ranging from 5 to 42 days, the average difference being 21 days. It there- fore appears that the time obtained indoors, with incubation tubes of the type employed, as a rule will be three to four weeks longer than that occurring under natural conditions. This is what would be expected, since ticks in tubes are not exposed to the wand, and when kept indoors are not subjected to the sun, in consequence of wliich they will not suffer the loss of body fluids and nourishment that ticks living in the open will. In addition to this, it is likely that the humidity in the tubes as a rule is higher than that of the outside air, which would tend to prolong longevity of the larvae. It is be- lieved that in using tubes such as were employed, the supply of moisture should not be excessive, the sand simply being kept moist. Unless this is done it is likely that the life of the larvae may be pro- longed far beyond that occurring under natural conditions. Unduly long periods for the death of all larvae, obtained by using incubation tubes, are safe but uneconomical, requiring the farmer to forego the use of his land longer than is necessary. It is important that the periods be ample, but it is likewise important that they be no more than this, since rotation methods are inconvenient and expensive at best m the majority of instances. In comparmg the time required for all the larvae to die for corre- sponding months in the indoor experiments for the two years it was found that for all but one month the time was longer the second year, the differences ranging from 3 to 45 days. The average difference was 25 days. A similar comparison of the outdoor experiments for the two years showed that in every instance the time was longer the second year, the differences ranging from 2 to 36 days. The average difference was 17 days. APPENDIX. Individual records of ticks used in experiments. Num- ber of tick. Date col- lected. ■Num- ber of e{;gs de- posited. Preovi- Oviposi- jwsition tion period, period. Hatch- ing period. Incubation period. Mini- Maxi- mum mum Entire lon- lon- time. gevity. gevity. Days. Days. Days. 15 116 143 12 218 254 17 141 182 6 207 247 58 249 286 15 237 279 21 902 258 13 249 297 10 ioo 280 10 87 271 112 278 11 107 285 6 98 274 14 110 281 18 106 288 18 100 268 8 97 19 100 268 8 87 257 16 104 243 16 113 253 21 103 242 49 64 202 17 98 204 21 114 225 111 230 28 106 215 25 116 205 14 107 196 25 97 185 25 119 207 20 106 164 23 95 154 15 101 159 11 81 139 19 118 158 17 96 140 25 100 143 14 139 185 18 80 114 20 95 127 20 62 96 9 84 117 12 118 149 13 94 125 20 81 110 ' 106 134 Per cent hatched. 1908. Aug. 5 ..do, ..do, ..do, Sept. 1 ..do.. ..do.. Oct. ..do.. ..do.. ..do.. Nov. ..do.. ..do.. ..do.. Dec. ..do.. ..do.. ..do.. 1909. Jan. 1 ...do.... ...do.... ...do.... Feb. 4 ...do.... ...do.... ...do.... Mar. 1 ...do.... ...do.... ...do.... Apr. 2 ...do.... ...do.... ...do... May 1 ...do.... ...do.... ...do.... June 22 ...do.... ...do.... ...do.... July 2 ...do.... ...do.... ...do.... 4,492 3,962 4,489 4,104 3,654 3,604 2,951 2,797 1,588 3,848 2,730 2,906, 3,187 3,329 3,167 2,215 1,858 1,985 2,201 1,496 3,723 3,460 2,970 305 2,601 2,970 2.706 1,993 2,994 1,674 3,361 1,380 2,607 3,065 1,741 2,491 4,178 4,040 3,181 3,296 2,311 3,003 1,765 1,640 3,452 3,710 2,214 2,416 Days. 3 4 Days. 15 13 15 14 16 IS 9 16 13 35 20 33 63 56 58 61 31 35 Days Days. 20 to 36 20 to 30 21 to 34 21 to 30 32 to 73 36 to 75 31 to 71 34 to 70 141 to 176 151 to 174 146 to 174 151 to 170 152 to 168 151 to 170 143 to 169 114 to 138 103 to 142 110 to 144 115 to 139 61 to 119 73 to 120 94 to 121 111 to 117 53 to 87 68 to 97 49 to 87 70 to 90 45 to 81 57 to 84 44 to 77 55 to 77 36 10 49 39 to 50 39 to 51 35 to 48 26 to 39 27 to 37 28 to 36 27 to 41 18 to 27 21 to 27 22 to 29 21 to 27 24 to 27 22 to 27 23 to 29 23 to 28 1 Ticks were collected May 1 and 2. 2 Ticks were collected June 2, 4, and 5. 13 O >v