26 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I42 



ture, such as that of the larva of Silpha (fig. 13 A), and trace the 

 evolution of a head plate known as the gula. In the silphid larva the 

 basal plate of the labium (Smt) is attached on the cranial margins 



Poc Cvx 



PoR. Poc 



B 



Fig. 12. — Coleopterous larvae with postgenae lengthened and united proximal to 

 the tentorial pits (A, B), or also distal to the pits (C, D). 



A, Thinopirms pictiis, Staphylinidae. B, StapJiylinus sp. C, Scarites sp., 

 Carabidae. D, Enjcronia stygica, Carabidae. 



immediately distal to the tentorial pits (pt). Proximal to it the lower 

 ends of the postocciput are united in a median sclerotization (Gu) in 

 the ventral wall of the neck. This is the beginning of the gula. In 

 many beetles, both larval and adult (B, C) and in some other in- 

 sects (D), the gula becomes lengthened distal ly accompanying a 

 lengthening of the postgenae proximal to the tentorial pits. As the 

 gula enlarges, the tentorial pits (B, C, D, pt) maintain their primary 



