Bird-parasites and Bird-phylogeny. 255 



I do not wish to tliinist any wearisome entomological 

 details upon you, but, for the purposes of the thesis which I 

 propose to develop, I must outline a very few facts — first, 

 as to the relations and, secondly, as to the biology of these 

 insects. 



The Mallophaga are an order of minute insects, ranging 

 in length from one to^ in a few exceptional cases, upwards 

 often millimetres, the average being about two millimetres. 

 They find their nearest relatives, among free-living insects, 

 in the Psocids, or Book Lice ; while they are still more 

 intimately related to another parasitic group, the Anoplura, 

 or Sucking Lice. They are divisible into two suborders : 

 a more primitive one in which the antennae are hidden 

 beneath the head, and in which the tarsi carry two 

 functional claws ; and a more specialised one, in which the 

 antennae project freely laterally, and which has but one 

 functional claw upon the tarsus. These suborders arc, 

 respectively, the Amblycera and the Ischnocera. 



The Mallophaga are completely parasitic in all stages of 

 their life-history. Eggs are laid upon the feathers of the 

 host ; this gives rise to a larva, generally similar to the adult, 

 and which passes by successive moults through two later 

 larval stages to the adult condition. The insects feed upon 

 feather-barbules and epidermal detritus, and are incapable 

 of maintaining life for more than a couple of days off the 

 body of the host. The Amblycera, the more active sub- 

 order, usually leave the host upon its death; and, as it is 

 only under very exceptional cases that they can find a new 

 host, perish altogether. The Ischnocera fix themselves by 

 their mandibles to the feathers of the host, and die in 

 situ. Transference from host to host can, then, only take 

 place during actual contact, either at mating, or from 

 brooding mother to young, or, in the case of gregarious 

 birds, when roosting together, or on rare occasions of 

 accidental contact. 



Owing to the fact that these insects have lived for a very 

 long time under very equable conditions, on a nutriment of 



