186 



PKACTICAL PARASITOLOGY 



are long in shape, by its, square, compact body-form. In Pediculus 

 and Phthirius the eyes are well developed, while in Hcematopinus 

 they are either rudimentary or are absent altogether. In Hcema- 

 topinus the sucking organ is longer than in the other two. At the 

 sides of the head are the five-jointed antennae. The thorax bears 

 upon its under surface three short, powerful legs, the tarsi of which 

 consist of a single piece, modified into a strong, recurved, movable 

 hook. Opposed to this hook, upon the lower end of the tibia, is a 

 thumb-like process which bears a thorn of varying length. In 

 Phthirius the first pair of legs is slighter and less formidably armed. 

 The number of abdominal segments is said to differ in each genus, 

 thus : six in Phthirius, seven to eight in Pediculus, eight to nine in 



Hcematopinus ; but Enderlein be- 

 lieves that all Anoploura have nine 

 abdominal segments. In Phthirius, 

 the anterior abdominal segments 

 are crowded closely together, the 

 boundaries being barely recogniz- 

 able. The posterior segments are 

 flanked by well-marked lateral por- 

 tions, covered with long hairs. The 

 anal and genital openings are situ- 

 ated at the hinder end of the body, 

 which is pointed in the male but 

 indented in the female. The penis 

 is chitinous and is withdrawn into 

 the interior of the body. There are 

 six pairs of abdominal and one pair 

 of thoracic stigmata. 



With regard to the mouth-parts 

 of lice, authors differ considerably 



both in describing the parts and in interpreting their uses. It is 

 certain, however, that, in the act of biting, the anterior portion of the 

 lining of the oral cavity is everted and appears at the front of the 

 head as a blunt barrel- or club-shaped proboscis. The anterior portion 

 of this proboscis is covered with hairs, arranged in rows and directed 

 backwards, which, when the proboscis is withdrawn, lie within the 

 oral cavity. The proboscis, when everted, acts as a sheath through 

 the lumen of which a long, hair-like sting is projected. This sting 

 appears to be homogeneous, but is probably composed of several parts. 

 When not in use the sting is enclosed in a long, tube-like sheath of 

 the same length, which is placed ventrally of the intestine, in the 

 head, and communicates with the latter by means of an opening in 

 the floor of the oral cavity. During the sucking act, which is per- 



FIG. 97. Pediculus capitis. Male. 

 40: 1. 



