A. W. Rymer Roberts 



205 



as it probably only represents a portion of the clypeus it is perhaps better 

 to adopt Henriksen's term of nasale. This also, like the mandibles, is 

 much subject to erosion and though the three denticles are visible as a 

 sharply pronged trident in some specimens, in others they are worn 

 down to a level with the base. Variation appears to take place to some 

 extent in regard to this organ, one specimen having been found bearing 

 four denticles. 



Ventral to the "nasale," nearly apposed to it, and also extending 

 outwardly, is another chitinous process, semi-lunar in shape and bearing 



Fig. 2 a. Cephalic plate of larva. 



b. Nasale and subnasal process from beneath. 



c. Anterior portion of maxilla. 



d. Hypopharynx. 



e. Nasale of larva in first instar. 



some seven teeth (Fig. 2 6). It does not extend so far as the nasale, the 

 points of the teeth reaching little beyond the base of the nasale. The 

 teeth are asymmetrically disposed and of unequal length. They may 

 also, with the nasale, be supposed to provide a gripping surface in 

 apposition to the mandibles. No suture has been found between the 

 nasale and this process to indicate that it is a separate sclerite, though 

 so much fusion appears to have taken place between the sclerites on the 

 dorsal surface of the head, that it may possibly represent the labrum of 

 other insects. A similar process has been found in the larva of Dichiro- 



