396 



LICE 



form a little pus, sufficient in vcr}' negligent individuals to make 

 the hair mat together. According to Stiles, if this is allowed to 

 run on, a regular carapace may form, called trichoma, in which 

 fungous growths may develop, and under which the lice abound, 

 and the head may exude a fcEtid odor. 



Crab Louse. — The crab louse, Phthirius pubis (Fig. 176), is 

 quite distinct from the other two species of human lice. It has 

 a very broad short body with long, clawed legs, presenting the 

 general appearance of a tiny crab, from which it derives its name. 

 The first pair of legs are smaller than the others and do not 



Fig. 176. Crab louse, Phthirius pubis, 9 • X 35. 



possess a " thumb " in apposition to the curved claw. The 

 abdomen is composed of six segments, and is markedly festooned 

 along the sides. This louse is grayish white in color, with dark 

 shoulder patches and slightly reddish legs. The females are 

 about yV of an inch in length, the males somewhat smaller. The 

 favorite haunts are the pubic regions and other parts of the body 

 where coarse hair grows, as in the armi)its and in tlie beard and 

 eyebrows. Unlike the other human lice this species is almost 

 exclusively confined to the Caucasian race. 



The females produce from ten to 15 eggs and glue them, one 

 at a time, to \hv coarse hairs among which thev Hve. A number 



