PARASITES AFFECTING THE SKIN 35 
for about two days, when it loses its clinging power and 
drops off. Some of the ticks complete their life-cycle 
on one animal, and in these the piroplasm is transmitted 
through the egg. It now proceeds to moult, and becomes 
the nymph, with eight legs, but differing from the 
adult in being destitute of sexual organs. It again 
seeks the summit of a blade of grass, and becomes 
attached to another animal host, on which it remains for 
about four days. It again gorges, and becomes black 
with blood, when it falls off, to again moult, and finally 
Fic, 7.—IxoDES REDUVIUS.* 
Enlarged. 
develop into the sexually adult tick. The females are now 
fertilized by the males, gorge, fall off, and lay their eggs. 
When full of blood, the ticks are dark in colour and 
opaque, and easily removed from their host. In the 
grass the tick abstains from food, and often fasts for 
a considerable period. In the asexual stages the tick 
shows no desire for any particular animal, but in the 
adult stage each variety of tick attaches itself to an 
animal of one definite species. In those ticks which 
require more than one host it is in the nymph stage 
* See p. 432 ‘‘Moussu and Dollar.” 
