190 INSECTS AND MAN 



curious that they should show such anxiety to leave a 

 dead bird, and it is probably due to the falling temperature 

 of the host's body. 



Aquatic birds, contrary to expectation, are not free 

 from Mallophaga, and, more remarkable still, their lice 

 are not specially modified to enable them to withstand im- 

 mersion in water. The explanation for this apparent 

 lapse of nature is probably that sufficient air always 

 remains entrapped between the feathers of the host to 

 enable them to exist in this unaccustomed element. 



Of the other parasites attacking poultry, we need only 

 mention the red mite, Dermanyssus gallince ; the chicken- 

 itch mite, Sarcoptes nutans; and the fowl tick, Argas 

 persicus. Of these, so far as is known, only the latter 

 transmits disease, but the others do considerable mechanical 

 damage by sucking blood, etc. 



Red mites are about one-twenty-fifth of an inch in 

 length, and, except when red after engorgement with 

 blood, they are of a light grey colour. In habit they are 

 particularly stealthy ; very active and also voracious, they 

 hide by day, issuing at night to feed on their hosts, and 

 returning to shelter after repletion. These mites can 

 hardly be termed true parasites semi-parasites is a better 

 term for their eggs are laid and hatched in their hiding 

 places and not on the host. Their attacks lead to loss 

 of flesh and general want of tone in chickens of all ages, 

 whilst in those newly hatched they cause a mortality often 

 as high as ninety per cent., and their not infrequent attacks 

 on man result in an eczematous skin disease. 



The chicken-itch mite, Sarcoptes nutans, causes a serious 

 and common disease in its host. Making its attack between 

 the scales of legs and feet of the chicken, it gives them a 

 tendency to stand up on end and separate, whilst between 

 them a chalky secretion is formed. Beneath these scales 

 and excretions the mites live and breed. 



Argas persicus (fig. 53) is a brownish-red tick about eight 



