THE LICE 



79 



being a larval host of the common tapeworm of the dog, Dipylidium 

 cajiinum, as is also the dog flea, Ctenoceyhalus canis. Infection of the 

 louse by the larva {Cysticercus trichodedes) is readily brought about 

 through ingestion of the eggs of the tapeworm which may have col- 

 lected about the anus or in the litter of the kennel. 

 This tapeworm is occasionally found to be present in 

 the intestines of human beings, particularly children. 

 It is quite conceivable how such infestation might 

 occur in the fondling of lousy or flea-infested dogs, 

 especially if the person's food be about at the same 

 time to act as a vehicle for the insects containing the 

 larva. 



Pediculosis of the Cat 



Trichodectes subrostratus, the only louse harbored Fig. 47. — Tri- 

 by the cat, is about the same length as the biting louse ^'\°^f°^t1- ^^^^^ 

 of the dog (1 to 1.3 mm.), but is not so 

 broad, and is distinguished by its pointed 

 head, which is slightly longer than broad. 

 The abdomen is oval, with median bands. 

 The head and thorax are bright yellow in color, the abdo- 

 men whitish (Fig. 48). 



Lousiness is not often met with in the cat; when it does 

 occur it is usually the accompaniment to a debilitated 

 condition in young animals. 



(after Osborn, from 

 Denny, Bui. No. 5, 

 Bureau of Ento- 

 mology, U. S. Dept. 

 of Agr.). 



Fig. 48.— 

 Trichodectes 

 subrostratus 

 (after Os- 

 born, Bui. 

 No. 5, Bu- 

 reau of En- 

 tomology, 

 U. S. Dept. 

 of Agr.). 



Pediculosis of Man 



Three species of pediculi infest man, Pediculus humanus 

 {P. capitis), the head louse, P. corporis (P. vestimenti), the 

 body louse, and Phtkirius pubis (P. inguinalis) the pubic 

 or so-called "crab-louse." 



1. Pediculus humanis. Pedicuhdae (p. 70). — The head 

 is somewhat diamond-shaped, short, and about as broad 

 as long. The abdomen has seven distinct segments, each 



bearing stigmata laterally placed. Color gray with darkened margins. 



The color is said to vary from light to dark according to the color of 



the skin or hair of the host. The female is 2.5 to 3 mm. ; the male about 



2mm. in length. 



2. Pediculus corporis. Pedicuhdae (p. 70). — Resembles preceding 

 species, of which it is regarded by some authorities as merely a variety. 

 It is slightly larger. The color is grayish-white. It lives upon the 

 clothing of its host, crawhng upon the body to feed. 



3. Phthirius pubis. Pediculidae (p. 70). — Distinctly differs in ap- 

 pearance from the two preceding. The head is short and thick, fitting 



