638 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.51. 



pharyngeal bridge is strongly chitinized; the inner portion of the base 

 of the mandible is molar-shaped; the retinaculum is present, in some 

 genera well chitinized, in others delicate and simple. The apex of the 

 mandible varies within the tribe. It is simple in Curinus, Axion, and 

 Exochomus, but bifurcate in Egius, Orcus, and Chilocorus. This 

 development of the mandible may indicate a division of the tribes into 

 two natural groups, and other characters support the same view. 



In the first group no epicranial suture is present, the posterior angle 

 of the frons reaching the occiput; no medio-posterior spine on each 

 side of the tergum of pro thorax; one to four marginal spines; no 

 scutal spine or only a rudiment of it on mesothorax and metathorax 



In the second group a very conspicuous epicranial suture is present 

 (fig. 85a, pi. 121) ; one rather short medio-posterior spine on each side 

 of the tergum of pro thorax; four or more marginal spines; a scutal 

 spine is always developed on mesothorax and metathorax. 



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1 1 am indebted to Miss Margaret M. Fagan, of the Division of Forest Insects, who has compiled these 

 references for me. 



