388 



LICE 



d^' salS 



'''^■"*- General Structure. — 



Lice are small wingless 

 insects constituting the 

 order Anoplura. They 

 were fornierlj* classified 

 as a sul)order of the 

 Heniiptera 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 can be withdrawn into 

 a little pouch under the 

 pharynx (Fig. 171 A). 

 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 

 mandil)les fitted for bit- 

 ing instead of sucking, 

 and these parasites feed 

 only on hair, feathei's, 

 etc., and not at all on 

 blood. In other respects 

 the sucking lice and l)ird 

 lice show a considerable 

 resemlilance to each 

 other, and are now gen- 

 (M'ally believed to l)e 

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

 very large curved claw, quite grotesque in appearance in some 



Fig. 171. Mouthparts of a body louse; .4, 

 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 nmscles of pharynx; 

 ret. m., retractor; dil. ra., dilators; d. p., dorsal 

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

 V. pi., ventral plate = labium (?). (Adapted from 

 Harrison.) 



jaw 



cnt, 



Fig. 172. Head of bird louse (from golden 

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

 compared witli thorax, a feature which readily 

 distinguishes bird lice from sucking lice. 



