MITES AND TICKS 197 



other hand, a mite fails to meet with a suitable host it climbs to the 

 top of some object such as a rock or the tip of a branch where it 

 comes to rest with other nymphs. If a snake happens to crawl over 

 a clump of these resting mites, they become active and climb on to 

 the snake and conceal themselves beneath its scales. After feeding 

 to engorgement, the protonymphs drop off and crawl about until 

 they find a dark, moist crevice. Here males and females sometimes 

 pair off and remain paired until they reach maturity. Ecdysis 

 follows soon after repletion and the newly moulted deutonymphs, 

 although active, usually remain in the humid area until the next 

 ecdysis. The deutonymph males and females usually pair if this 

 has not occurred in the previous stage. After moulting to the adult 

 stage, the mites remain in the moist crevices until their integu- 

 ment has hardened and then begin to wander about until they 

 come in contact with a suitable host, to which they respond by 

 their reactions to gravity, temperature and odour. Male mites will 

 copulate after feeding but are not attracted by replete females. 

 These unfecunded females lay eggs which develop partheno- 

 genetically into males. Females normally lay from 60 to 80 eggs, 

 feeding two or three times at intervals of one or two weeks. 



The blood-sucking mites of the genus Haemolaelaps are mammal 

 and bird parasites and seem to show a preference for rodents. They 

 are probably ovoviviparous and give birth to the first nymphal 

 form. As in most parasitic mites the males probably do not feed on 

 the blood of the host, but haemoglobin has been demonstrated in 

 both pro to- and deutonymphs which leave the host immediately 

 after feeding and moult in the nest. 



Ticks are parasitic during the greater part of their lives, but all 

 leave the host in order to deposit their eggs. These are laid on the 

 ground in enormous numbers and hatch into six-legged larvae. 

 The young ticks remain clustered together for several days but 

 then climb the nearest blade of grass and await the coming of their 

 host. Many die in the attempt, but some succeed in attaching them- 

 selves to a passing animal and proceed to gorge themselves with 

 blood. After feeding for a few days the larvae drop off, seek a hiding 

 place and moult into nymphs which behave in much the same way. 

 The adult stage is reached after one more moult. 



Lees and Beament (1948) have shown that'the egg of the sheep tick 



