THE LICE 71 



segments of the abdomen number eight or nine, and their tarsi are 

 terminated by a single claw. 



Order IV. Mallophaga 



The Biting Lice. — Insecta (p. 15). The members of the order of 

 biting lice resemble the sucking lice in general form, but differ from them 

 mainly in that they are much smaller and have the mouth parts adapted 

 for biting and mastication. They may be at once distinguished by the 

 head and mouth parts; the head is usually rounded, triangular, squared, 

 or crescent-shaped, and is broader than the thorax (Fig. 39). Upon the 

 under side of the head are located the mandibulate mouth pieces adapted 

 for cutting and feeding upon epidermic scales, hairs, feathers, and 

 other cutaneous products. The eyes are simple ocelli located back 

 of the short antennae and are often indistinct. The thorax is generally 

 narrow, the prothorax being distinct, the two posterior segments fused. 

 The legs are adapted for either clasping or running; in the first case the 

 tarsi terminate in a single claw (Philopteridae), in the second the tarsi 

 are long and terminate in two claws (Liotheidse). Wings are absent. 

 The abdomen is generally elliptical; it may be elongate, or short and 

 broad, approaching a globular outline. Their relatively small size and 

 hard, flattened bodies faciHtate their movement among the hairs close 

 to the body. 



In their breeding habits and life history the Mallophaga agree with 

 the preceding order. 



Although the order has been variously subdivided, it will be sufficient 

 here to place the biting lice according to their hosts in the two families 

 PhilopteridsB and Liotheidse, the former including the biting lice of 

 mammals and birds, the latter the lice of birds only. 



Biting lice, like the suctorial, are limited to a specific host, which as a 

 rule they do not voluntarily leave imless it is to crawl upon another 

 host of the same species, in which case the migration is ordinarily ac- 

 complished when the bodies of the host animals are in contact. Under 

 conditions of severe iafestation among poultry some of the parasites 

 may pass to the roosts and nests and, by contact, even to the body of a 

 mammalian host, but they will not survive such migrations for more than 

 a few hours. 



Pediculosis of Domestic Mammals 



The condition commonly known as lousiness is medically referred to 

 as pediculosis, a term correctly applied whether the condition be due 

 to the presence of either the sucking or the biting species. The term 

 phthiriasis should properly be restricted to infestation with the genus 

 Phthirius in particular. 



Lousiness is usually accompanied by an unthrifty condition, not 



