388 



LICE 



dt\,m. 



M^.m. 



d.yii sal.ii npj ttplj 



General Structure. — 



Lice are small wingless 

 insects constituting the 

 order Anoplura. They 

 were formerly classified 

 as a suborder of the 

 Hemiptera or true bugs, 

 but recent studies have 

 shown the erroneousness 

 of this grouping. The 

 mouthparts are adapted 

 for piercing and sucking. 

 The piercing apparatus 

 (Fig. 171B) consists of 

 four needle-like organs, 

 one of which is the deli- 

 cate salivary duct, which 

 can be withdrawn into 



Fig. 171. Mouthparts of a body louse; A, 

 longitudinal section through head; B, mouthparts 

 from sac under pharynx and oesophagus; buc. t., 

 buccal tube; m., mouth cavity; ph., pharynx; oes., 

 oesophagus; retr. sac, retractile sack for mouth- 

 parts; prot. m., protractor muscles of pharynx; 

 ret. m., retractor; dil. m., dilators; d. p., dorsal g^ JJ^^Jg pouch under the 

 piercer; sal. d., salivary duct; V. p., ventral piercer; 

 V. pi., ventral plate = labium (?). (Adaptedfrom pharynx (Fig. 171 A). 



Harrison.) This type of mouthparts 



readily distinguishes the 

 true lice from the bird 

 lice, which constitute 

 the order Mallophaga 

 (Fig. 172). In the latter 

 there are nipper - like 

 mandibles fitted for bit- 

 ing instead of sucking, 

 and these parasites feed 

 only on hair, feathers, 

 etc., and not at all on 

 blood. In other respects 

 the sucking Hce and bird 

 Hce show a considerable 



- ^aw 



-- ont, 



Fig. 172. 



Head of bird louse (from golden 

 eagle); ant., antenna. Note breadth of head as resemblance tO each 

 compared with thorax, a feature which readily 

 distinguishes bird lice from sucking lice. 



other, and are now gen- 

 erally believed to be 

 closely related. The feet of the true lice are armed each with a 

 very large curved claw, quite grotesque in appearance in some 



