CHAP. XVII 



PSOCIDAE 



391 



Fig. 242. — Traijsverse horizontal section 

 of head of Psocus : f, foric or pick ; 

 t, lingua ; mx, left maxilla ; c, cardo ; 

 Py stipes ; 7}i,vi, muscles ; m.s^ socket 

 of mandible. 



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



more, about tliirteen 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, 



but Burgess thinks it more prob- 

 ably an independent organ,^ as it 



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 

 ci '^c.m to a distinct clypeus, behind 



Fio.243.— A,FrontofheadofPsoc«sfefeTO- which there is a remarkable 



rfiorphus J cZ, post clypeus ; a, epicran- , , , , . ,, 



lum : B, transverse horizontal section pOSt-clypeUS, whlch IS usually 



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



clypeus ; c.jti, clypeal muscles ; g^ epi- 7 



cranium ;c tendons ;?.m, labial muscle in inner face are attached Several 

 section ; oe oesophagus ; oe.Joes^pha- niuscles wMch 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 



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



