THE LIFE OF A CATTLE TICK 183 



cycle may be considered. The order of events is as 

 follows : Both sexes of ticks are found on the same 

 cow, the male being very small and the female very 

 large and gorged heavily with blood. After mating, 

 the female drops to the ground and proceeds to lay 

 her eggs. In the case of the cattle tick, the ovaries 

 of the mother are infected by the Babesia, and when 

 the young develop within the egg, the parasites gain 

 entry into their organs, so that the young tick is 

 born infected. After a time, varying with the 

 weather conditions, the larva hatches out. It is a 

 small, remarkably active, six-legged animal, and 

 rapidly makes its way up the neighbouring vegeta- 

 tion as high as it can, and remains there until the 

 advent of cattle gives it an opportunity to reach a 

 host. As the cattle push through the vegetation, 

 the larvae leave the plants with great agility, fasten 

 their mouth parts into their hosts, and proceed to 

 gorge themselves. On the same host the larvae 

 moult and become nymphs, and after a further 

 moult the adult forms are assumed. 



The sheep tick, Rhipicephalus bursa, feeds on the 

 same host as larva and nymph, and moults once 

 upon the sheep. The nymph falls off when fully 

 gorged, undergoes metamorphosis upon the ground, 

 and then attacks a second host. The larvae of 

 R. bursa do not seem to be infective, but the adults 

 are. 



Supposing the cattle tick, Ixodes ricinus, is the 

 one concerned, from hatching to larva the sequence 

 of events is like that in Boophilus, but when the 

 larvae are fully distended with blood, they drop from 



