CHAPTER VII 



THE ORDER ANOPLURA: LICE 



THE Anoplura constitute a small order of blood-sucking insects 

 which are entirely parasitic on mammals. Both in their structure and 

 life history they exhibit in a high degree those features which are 

 commonly associated with the parasitic habit, and form in this respect 

 an interesting comparison with the less specialized fleas. The body 

 is compressed in the dorso-ventral direction, so as to oppose as little 

 resistance as possible when the insect moves about among the hairs 

 or fur of the host, and is enclosed in a tough and leathery integument 

 which is not easily ruptured. They are wingless, and have the legs 

 very strongly developed ; the feet are armed with powerful claws to 

 enable the parasite to retain its hold. The metamorphosis is incom- 

 plete ; the young resemble the adults, and the eggs are laid among 

 the hairs of the host, to which they are attached by an adhesive 

 substance secreted by the female, so that the entire life cycle is passed 

 upon one animal. Further, the separate species are usually limited 

 to a particular species of host, and cannot thrive on any other. 



The relationship of the Anoplura to other groups of insects has 

 long been in dispute. They have been placed near the Mallophaga 

 or bird lice,* which they resemble very closely in body form and 

 general appearance, but from which they are sharply distinguished by 

 the structure of the mouth parts ; the Mallophaga are provided with 

 a pair of strong mandibles, easily recognized under the microscope on 

 account of their dark pigmentation, and live on solid food, while the 

 true lice have a complex sucking and piercing apparatus, and live 

 exclusively on blood. Enderlein regards the Anoplura as closely allied 

 to the Rhynchota, mainly on account of a similarity which, it is 

 claimed, exists between the mouth parts of the two groups. The 

 mouth apparatus of the louse is, however, very complex and difficult 

 to study, and as no common agreement has as yet been reached with 

 regard to the homology, or even the mechanism, of the parts, 

 too much stress should not be laid on such a criterion ; one has, 



* A few Mallophaga occur on mammals. 



