362 



TICKS 



which requires two different hosts to complete the life cycle. 

 The six-legged larvae (Fig. 157B), of which there are about 5000 

 in a brood, attach themselves to any of the rodents which abound 



FIG. 156. Spotted fever tick, Dermacentor venustus, male () and female (9)- 



X 12. 



FIG. 157. Development of spotted fever tick, Dermacentor venustus; A, eggs; 

 B, larva; C, nymph. X 30. 



in the country where the ticks occur, especially squirrels of 

 various kinds. Usually the larvae, and the nymphs also, attach 

 themselves about the head and ears of their host. After a few 

 days the larvae drop, transform into nymphs (Fig. 157C) and 



