68 



TEXT-BOOK OF ENTOMOLOGY 



let 



FIG. 63. Seliutilriii larva, common on 

 Carya porcina, with details of mouth-parts : 

 leg, leg ; mx, maxilla ; gal, galea ; lao, lacinia. 



mx.p 



of which is unknown, but would appear to be usually that of 



smell. 



The second maxillae. - - The " under-lip " or labium of insects is 



formed by the fusion at the basal portion of what in the embryo are 



separate appendages, and which 

 arise in the same manner as the 

 first maxillae. They are invariably 

 solidly united, no cases of partial 

 or incomplete fusion being known. 

 The so-called labium is situated 

 in front of the gula or gular region, 



T vr* " \ / and is bounded on each side b y 



ivfe 8 ^ K the gena> or cheek - As already 



\( V J T observed, the second maxillae ap- 

 pear to be the appendages of the 

 last or occipital segment of the 

 head. 



The second maxillae are very 

 much differenti- 

 ated and vary 



greatly in the different orders, being especially 



modified in the haustellate or suctorial orders, 



notably the Hymenoptera and Diptera. In the 



mandibulate orders, particularly the Orthoptera, 



where they are most generalized and primitive in 



shape and structure, they consist of the following 



parts : the gula (a post-gula is present in Dermap- 



tera), submentum (lora of Cheshire, i, p. 91), men- 

 turn, palpifer, the latter bearing the palpi; the 



lingua (I i gula) and paraglossce, while the hypo- 



pharynx or lingua is situated on the upper side. 



The labial palpi are of the same general shape as 



those of the first maxillae, but shorter, with very 



rarely more than three joints, though in Ptero- 



narcys there are four. Leon has detected vestigial 



labial palpi in several Hemiptera (Fig. 73). As 



to the exact nature and limits of the gula, we 



are not certain ; it is not always present, and may ,;.'m 



be only a differentiation of the submentum, or the ^;_^ ar do.- After 



latter piece may be regarded as a part of the gula. 



We are disposed to consider the second maxillae as morphologically 



nearly the exact equivalents of the first pair of maxillae, and if we 



Fm. f4. Maxilla ol 



3ms 



