388 



LICE 



proj.m 



B 



General Structure. 



Lice are small wing- 

 less insects constituting 

 the order Siphunculata. 

 They were formerly class- 

 ified 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 

 FIG. 171. Mouthparts of a body louse; A, f our needle-like organs, 



longitudinal section through head; B, mouthparts , . , . , , ,. 



from sac under pharynx and oesophagus; buc. t., One Ot which IS the Qell- 

 buccal tube; m., mouth cavity; ph., pharynx; ces., ca t e salivary duct, which 

 oesophagus; retr. sac., retractile sack for mouth- vuj 



parts; prot. m., protractor muscles of pharynx; Can be Withdrawn into 

 ret. m., retractor; dil. m., dilators; d. p., dorsal a little pouch Under the 

 piercer; sal. d., salivary duct; v. p., ventral piercer; rru -n-ri A \ 



v. pi., ventral plate =labium(?). (Adapted from pharynx (* Ig. 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 lice and bird 



FIG. 172. Head of bird louse (from golden ,. , -111 



eagle); ant., antenna. Note breadth of head as hce Show a considerable 

 compared with thorax, a feature which readily resemblance t O each 

 distinguishes bird lice from sucking lice. 



other, and are now gen- 

 erally believed to be closely related. These two orders of lice are 

 sometimes combined in an order Anoplura. The feet of the true 

 lice are armed each with a very large curved claw, quite gro- 



