LARVAL HEAD OF SOME CHIRONOMIDAE — GOUIN 



197 



It is therefore interesting to look for the correlations of the 

 mandible with the other structural elements, especially the hypochilum. 

 Alluding to the disposition of the points of the articulations, Schrem- 

 mer claims that when the mandibles move in a horizontal plane, they 

 are not "segmented." This is precisely the case in Tanypinae larvae : 



1-7 / \, 



MPIdl 



MPrm 



Fig. 15. — Macropelopia cf. nebulosa Mg. 



Part of a nearly median sagittal section. It shows the relationships of the 

 structural elements of the ventral cephalic region, innervation of a labial palpus ; 

 premental sclerite and its hinge of articulation; the salivary pump and the 

 insertion of its muscle on its ventral sclerite. The labroepipharyngeal muscles 

 (MLE) ; the club-shaped maxillary bristles (Lac) are grazed. Detail of the 

 "pseudoradula" (psr) on the right. 



their mandibles are opposed to each other and the hypochilum, nor- 

 mally constituted, is membranous. 



But in other Nematocera, the mandibles move in intermediate 

 planes between the frontal and sagittal ones. It is then established 

 that the unsegmented mandible exists in the types of which the 

 hypochilum is well formed, sclerotized, and is the fixed jaw of pincers 



