CHAP. XVII 



PSOCIDAE 



391 



The antennae consist of eleven to twenty-five joints, or even 

 more, about thirteen being the 

 usual number; the basal two are 

 thicker than the others, and are 

 destitute of setae or pubescence 

 such as the others possess. The 

 maxillae and labium are remark- 

 able. The former possesses a 

 peculiar hard pick or elongate 

 rod ; this is considered by many 



naturalists to be the inner lobe, FIG. 242. Transverse horizontal section 

 -I.T-) *.!_ i__- A T, of head of Psocus : f. fork or pick ; 



but Burgess thinks it more prob- t> lingua . ma . left m illa . c> J^ : 

 ably an independent organ, 1 as it P> sti P es ; m -m, muscles ; m.s, socket 



, . . , , . -, i of mandible. 



has no articulation of any kind 



with the outer lobe. The latter is remarkably thick and fleshy ; 



the palpus is 5 -jointed. Other 

 authorities consider the pick to 

 be certainly the inner lobe ; if 

 it be not, the latter is quite 

 wanting. Hagen agrees with 

 Burgess in stating that the 

 pick slides in the outer lobe as 

 : in a sheath. The labium has 

 a large mentum and a ligula 

 divided anteriorly into two lobes; 

 at each outer angle in front 

 there is a globular projection, 

 which is doubtless the labial 

 palpus ; reposing on the labium 

 there is a large free lingua. 

 The labrum is large, attached 

 to a distinct clypeus, behind 



Fia.243. A,Frontofheadofp5ocM5Ae<ero- which there is a remarkable 



morphus ; cl, post clypeus; g, epicran- , . , ,- 



ium: B, transverse horizontal section pOSt-ClypCUS, Which IS Usually 



of post -clypeus of PSOCUS: cl, post- prominent as if inflated; to its 



clypeus ; c.m, clypeal muscles ; g, epi- 7 



cranium;)!, tendons ;l.m, labial muscle in inner face are attached several 



section ; oc .oesophagus ; r.6, oesopha- musc l es w hich converge to be 

 geal bone. (After Burgess and Bertkau.) . 



inserted on a plate placed below 

 the anterior part of the oesophagus, and called by Burgess the 



1 P. Boston Soc. xix. 1878, p. 292. 



