132 FLEAS, FLUKES AND CUCKOOS 



claws adapted for clinging to the feathers, and the head large to accom- 

 modate the heavy strong mandibles and their supporting framework 

 (Plate XXI). Such fat-bodied forms on other parts of the body 

 would be easily picked off by the bird or crushed by its bill. The eggs 

 are laid on the feathers of the head and neck, singly or in bunches, and 

 need no special modifications to protect them as they are out of reach 

 when the bird is preening. 



On the wings and back, where the louse is always in danger from 

 the bill, a flattened elongate, long-legged type is found (Plate XXI lie) 

 which is able to move rapidly, mainly by slipping sideways across the 

 feathers. The eggs, which are laid on the wing feathers, are elongated 

 and usually placed between the barbs, which protect them during 

 preening. 



Apart from these two extremes — the large-headed, short-bodied and 

 the flattened elongate forms — there are many others which are 

 intermediate in body form and have different habits. These presumably 

 occupy different habitats on the bird, but our knowledge of the ter- 

 ritory- of the majority of lice in general is lamentably small. In 

 some birds, such as the common mallard, there is one head louse 

 {Anatoecus) and one wing louse (Anaticola) , but in other birds there may 

 be two or more genera occupying the same habitat. In the game-birds, 

 for instance, there are two genera apparently adapted to life on the 

 wings. 



The Mallophaga we have just been discussing belong to the super- 

 family Ischnocera (Plate XXII). The majority of birds also harbour one 

 or more species of genera belonging to the other superfamily, the Am- 

 blycera. The members of this superfamily have, in general, become less 

 closely adapted to particular habitats on the bird's body. They are nearly 

 all fast runners and probably move freely all over the host's body, and are 

 not specialised for life on particular feathers. This absence of specialisa- 

 tion results in less well marked divergence, and the Amblycera are thus 

 divided into far fewer genera than the Ischnocera. Using the term 

 genus in its broad sense the Ischnocera are represented by about forty 

 genera on British birds and the Amblycera by twenty-two. Again, if the 

 nine genera found on the British game-birds are considered, we find 

 that six of these belong to the Ischnocera and only three to the Ambly- 

 cera. It is usually believed that the Amblycera have retained more of 

 the habits and hence the morphological characters of the primidve 

 ancestral Mallophaga. The most specialised character of the Amblycera 



