CHAPTER VIII 



THE LICE 



There has been much disagreement among various authors as to the 

 systematic arrangement of the lice. The classification given here, if 

 faulty, will perhaps at least serve the purposes of this work until exacting 

 systematists have better settled the matter. 



Order III. Siphunculata. — Insecta (p. 15). The Sucking Lice. — ^The 

 lice of the order Siphunculata have the suctorial mouth parts at the 

 anterior border of the head, the movable proboscis being formed of the 

 upper and lower lips (Fig. 38). Within this is the sucking-tube which is 

 projected beyond its sheath and buried in the skin when used to aspirate 

 blood. The eyes are two simple ocelli, one on each side. The antennae 

 are short. The thorax is usually broader but shorter than the head, with 

 indistinct division into three segments. The legs are short and thick, the 

 tarsi terminating in a single claw. There are no wings. The abdomen 

 is large and generally elliptical in outline. The last abdominal segment 

 is rounded in the male with an opening for the penis. In the female 

 this segment is notched and has two small terminal appendages. The 

 female is from L5 to 5 mm. in length, the male somewhat smaller. 



Life History. — The metamorphosis is incomplete. The young, which 

 leave the eggs by an operculum, have the shape of the adults but do not 

 acquire the adult color and consistency until after several molts. 



The eggs as they are extruded from the female are glued fast to the 

 hairs of the host by means of a viscid secretion. In this position they 

 are commonly referred to as nits, which, with the aid of a hand glass, 

 will be observed to have somewhat the shape of a barrel with the at- 

 tached end rounded and a blunt free extremity (Fig. 40, e). 



Hatching occurs in from five to six days, the young in general re- 

 sembling the adults excepting in size. They become mature in about 

 four weeks. 



The sucking lice come into one family, the Pediculidse. All are per- 

 manent parasites, the entire life cycle being spent upon the host. All 

 are limited to a specific host, and will only accidentally inhabit a host of a 

 different species. Therefore if the host is known, the specific identity 

 of the parasite is readily determined. 



The characteristics of the species are here given under their respective 

 host animals. It may be said of the sucking lice in general that the head 

 is inserted directly on the thorax, their antennae are five-segmented; the 



