ENTOGNATIIY IN APTERYGOTES — TUXEN 



391 



given by Hoffmann in his two papers on Tomocerus pliimheus L. 

 (1905 and 1908). 



The important points to be noted are the following : The mandibles 

 and the maxillae are hollow at the inner and upper sides just as in 

 Campodea; a closer comparison of the single mouth parts will be 

 given in a later section. The mandibles do not extend so far back 

 as in Campodea, the relative position of these mouth parts being 

 "normal" ; on the other hand they extend more dorsally, very near to 

 the roof of the head. A fulcrum is found similar to that of Campodea. 



— rtidh 



Fig. 7. — Campodea plusiochacta Silv. Head in side view. Mandible and 

 maxilla dotted. 



The pouch is broadest posteriorly surrounding both pairs of mouth 

 parts (see figs. 8 and 11) and narrowing anteriorly, the anterior split 

 of the atrium (the "mouth") being much narrower than in Cam- 

 podea. The sternal wall of the head is coalesced in the middle line 

 with the labium in the hind part of the head (Denis, 1928, figs. 37-38 ; 

 unfortunately it is often difficult to make clear where the sections are 

 laid), but free more anteriorly where the hypopharynx is found 

 (Denis, fig. 31). The maxillae intrude between the lingua and super- 

 linguae of hypopharynx (Denis, loc. cit. ; my figs. 10 and 11). 



The labium is the well-known triangular piece far anterior on the 

 under side of the head. The part behind this piece (or rather pair of 

 pieces) is commonly regarded as the submentum, but a limit between 

 submentum and plicae orales is not found and Hoffmann (1911) men- 



