4o6 THE BIOLOGY OF INSECTS 



maggot, the female brings forth a ripe larva which quickly 

 pupates ; by this means the preparatory stages of the normal 

 insect transformation with their accompanying risks are 

 largely eliminated from the Hfe-history. It will be realised 

 that the animals on which these insects live and feed, are 

 such as afford through their family or social life- relations, 

 opportunity for the passage of the parasites from one host 

 to another. 



There are two orders of wingless parasitic insects, allied 

 to some of the winged groups that display the open type of 

 wing-growth (Exopterygota) and undergo through their 

 development a series of moults without any marked change 

 of form. These are the Mallophaga (biting-lice) with 

 mandibulate jaws, and the Anoplura (true or sucking lice) 

 with highly specialised piercing and suctorial mouth. They 

 all have very special parasitic relations with warm-blooded 

 vertebrates, the vast majority of the Mallophaga being 

 attached to birds and the small minority to mammals, while 

 the Anoplura are found on mammals only. The Anoplura 

 are blood-suckers, piercing the skin of their hosts to obtain 

 food, while Mallophaga bite the feathers or hairs of their 

 hosts, and eat the surface layers of the skin and its hardened 

 secretions, sometimes causing such abrasion as to draw 

 blood. In the Anoplura and the mammal-infesting Mallo- 

 phaga the relatively short, stout foot has only a single strong 

 claw, which in conjunction with a pad on the tarsal segment, 

 clasps the hair of the host-animal ; these insect parasites 

 therefore cling very closely. Their eggs are cemented to 

 the hairs or feathers and the whole life-cycle is usually 

 passed on the same beast or bird, though the habits of the 

 host being often social, the insects may have opportunities 

 of transferring themselves to fresh carriers. Each species 

 of these parasites usually infects some definite host, and in 

 most cases, it is impossible to discern any special reason for 

 their slight but constant specific differences. Not infre- 

 quently, however, the same kind of mallophagan is found 

 to live indifferently on several allied species of beast or bird. 

 Docophorus communis has indeed been recorded from a 



