184 SOME MINUTE ANIMAL PARASITES 



their first hosts to the ground, and remain practically 

 motionless until they moult. Meanwhile the first 

 hosts of the larvae pass on. When the larvae have 

 moulted they become nymphs, and possess eight legs 

 instead of six. Once again they climb the foliage 

 near them and await victims. Again they obtain a 

 meal from their hosts, and in return, infect them. 

 A further wait on the ground to which they have 

 dropped leads to a second moult, and the fully mature 

 ticks emerge, to await a final victim, from which they 

 obtain a meal, on which they mate, and which they 

 may infect while feeding. Ixodes ricinus thus needs 

 three hosts in order to complete its own develop- 

 ment. 



The disease appears in cattle about nine to twelve 

 days from the time when the} 7 were bitten by the in- 

 fected ticks. The larvae of Boophilus are infective as 

 well as the adults. The tick Ixodes ricinus, that carries 

 European redwater, is interesting, as the larvae from 

 the eggs of an infected mother are already infected 

 and can infect cattle at their first meal. The dog 

 ticks responsible'for the spread of Babesia canis, do 

 not appear to have acquired complete hereditary 

 infection. Neither the larvae of R. sanguineus, the 

 common dog tick of India, nor of Hcemaphysalis 

 leachi, which is the carrier of piroplasmosis in South 

 Africa, seem to transmit frequently as larvae ; but if 

 the said larvae have fed on infected dogs, they can 

 carry over the disease when they become nymphs 

 and also as adults. 



The problem of what happens to the parasite 

 when within the tick is still incompletely solved. 



