208 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 6 



Valley show that the adults of this tick are capable of a longevity 

 greater than 641 days. This record was made on a lot containing 

 eight males and two females which emerged from the nymphal stage 

 July 9-10, 1910. All of the ticks were alive August 10, 1910, when 

 four males were removed. The remaining four males and two females 

 were still alive April 10, 1912, when the last observation was made. 

 A single male, in another lot containing six males and ten females, 

 which became adult on July 18-19, 1910, was alive on April 10, 1912, 

 when last observed. In another lot consisting of eight females, seven 

 were still alive on the elate of last observance, April 10, 1912. In each 

 of the last two lots the longevity exceeded 632 days. In a large series 

 of tests at Dallas, Texas, of adults which molted from nymphs during 

 1910 and 1911 the longevity of many specimens ranged from nine 

 to fifteen months. It has been found that adults which were collected 

 in Montana in the spring readily attached and became engorged the 

 following spring. These individuals undoubtedly hibernated as 

 adults and were therefore a year and six or seven months old. 



Life Cycle 



The question of the time required for this tick to complete its life 

 cycle has been considerably discussed. It was thought that one 

 generation developed annually. However, the investigations con- 

 ducted by the Bureau of Entomology in cooperation with the Montana 

 Experiment Station early indicated that this is not the normal cj^cle. 

 As pointed out by Cooley^ and more full}^ discussed by Hunter and 

 Bishopp,^ the life cycle often, if not usually, requires two years for its 

 completion. More recently Rucker^ has made the statement that 

 "Additional experimental evidence seems needful to prove this." 

 The question is not if the life cj^cle sometimes requires two years, but 

 is it ever completed in one year? In other words, the two-year life 

 cycle is the usual, if not the only course followed b}- the tick in the 

 Bitter Root Valley. Since it has been proved conclusively by experi- 

 mentation that adults will not under natural conditions become 

 engorged during the same season in which they transform to that stage, 

 there is no likelihood of the completion of a cycle developing from 

 overwintered nymphs. The same habit prevents the completion of 

 a generation from overwintered larvae as well as from individuals 

 which may pass the winter as engorged nymphs. 



A study of the data on the number of n.vmphs present on various 



'Bull. 85, Mont. Exp. Sta., 1911, p. 25. 



sBull. 105, Bur. of Ent. U. S. Dept. Agr., 1911, pp. 23-27. 



^Public Health Repts., Vol. XXVII, No. 36, 1912, p. 13. 



