THE BIOLOGIES AND HABITS OF TICKS 



435 



proper occurs in southern United States and parts of Mexico while 

 varieties of this species are present in tropical America, Africa, Australia, 

 and other parts of the world. It is not only a species wliich produces heavy 

 losses on account of its occurrence in tremendous numbers, but it is espe- 

 cially important on account of being the intermediate host of the piro- 

 plasma which produces Texas or splenetic fever in cattle. 



Our form is very restricted in host relations. It can complete develop- 

 ment only on cattle, horses, mules, and deer, rarely on a few smaller ani- 

 mals. This liabit has greatly facilitated eradication. The molts are 



Plate XXVII. — The cattle tick, Boophilus anmilntus. Fiff. 1 (Left)— Fully engorged 

 female. Fig. 2 (Right) — Engorged female depositing eggs. (Bishopp.) 



passed on the host. The females deposit from 2,500 to 4,500 eggs. In 

 summer these hatch in from 20 to 30 days, while in the fall and winter 

 the incubation period may extend to 200 days. The longevity of the seed 

 tick varies according to temperature and humidity from about two to 

 eight months, and the period from dropping of tlie engorged female to 

 the death of all of her progeny, or the nonparasitic period, ranges from 

 28 days in summer to 279 day.s in cooler weather. The period of attach- 

 ment of the seed tick to the host until the engorged female detaches 

 ranges from 20 to 59 days. Both of these periods are of considerable 

 importance in connection with control by the so-called pasture rotation 

 methods. 



The Genus Rhipicephalus. — This group, though small, contains many 



