CHAP, xvir 



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,-r j.i'1'j. 1 of head of Psocus : f. fork or pick ; 



but Burgess thmks it more prob- ^^ Hngua ; mx, left maxilla ; c, cardo \ 



ably an independent organ ,-^ as it P^ stipes ; m.m, muscles ; m.s, socket 



1 .., .. o 1-1 of mandible. 



nas no articulation 01 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 mentuni 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 

 which there is a remarkable 



viorphus ; d, post clypeus ; g, epicran- . i i n 



ium : B, transverse horizontal section pOSt-clypeus, Whlch IS USUally 



of post -clypeus of Psocus: ci, post- prominent as if inflated I to its 



clypeus ; cm, clypeal muscles ; g, epi- T p 



cranium;^, tendons ;^.m, labial muscle in inner lace are attached Several 



section ; a. oesophagus ; oe.Joesopha- ^luscles which Converge tO be 

 geal bone. (Alter 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. 



Fig. 243. 



-A, Front of head oi Psocus hetero- 



