NO. 3 



INSECT HEAD — SNODGRASS 



129 



tinuoLis with the postocciptal rim of the cranium (Poc), which is set 

 oft' by the postoccipital suture (pos) ending ventrally in the tentorial 

 pits ipt, pt). 



NMb 



B 



Poc 



Fig. 49. — Evolution of the " gula " in Coleoptera. 



A, Postero-ventral view of the head of a scarabaeid larva, Popillia japonica. 

 B, same of a silphid larva, Silpha ohscura. C, ventral surface of an adult 

 meloid, Epicauta pcunsylvanica. D, same of a carabid larva, Scaritcs. 



a. posterior articulation of mandible; Cd, cardo; cv, cervical sclerite; e, an- 

 terior articulation of mandible ; Gu, gula ; Pge, postgena ; Poc, postocciput ; 

 PoR, postoccipital ridge; pos, postoccipital suture; pt, posterior tentorial pit; 

 Sml, submentum. 



The characteristic structure of an adult coleopteran head is well 

 illustrated in the head of a meloid beetle (fig. 49 C). The form of the 

 cranial capsule here differs principally from that of the scarabaeid 

 or silphid larva in the lengthening of the postgenal regions between 

 the foramen magnum and the articulations of the cardines {e, e). 



