212 II Y MEN OPT ERA OF AMERICA. [ PART I. 



Subgenus ODYNERUS 1 Latr. (sensu strictiore). 



Leionotus Sauss. Et. Vesp. I, 151. — Odynerus propr. diet. Sauss. 



ibid. Ill, 223. 



First segment of the abdomen without any transverse suture. 

 Antennae of mates terminated by a hook, or simple (or a 

 tittle varied at the extremity, only in Hypodynerus). 

 Mandibles of the males simple. 



This subgenus contains insects of the most varied forms; types 

 stubbed or elongate, with the abdomen sessile and conical or 

 subpetiolate with the first segment funnel-shaped. 



The species with a quite sessile abdomen have been detached 

 into the genus Bhynchium, and that with the most petiolate 

 abdomen into the genus Nortonia. 



The limits between this subgenus and the subgenus Epipona 

 are not clearly defined. In subgenus Odynerus the abdomen is 

 conical, ovate-conical or subpetiolate, spindle-shaped. In sub- 

 genus Epipona it is depressed oval, lenticular as in Pterochilus. 

 In Odynerus the thorax is more square, its anterior margin being 

 straight or concave, its angles often sharp, and the metathorax is 

 generally excavated in the middle. In Epipona, the thorax is 

 short, ovate ; its anterior margin rather convex ; the metathorax 

 convex and rounded. 



The two groups can be easily distinguished by the appearance, 

 but not readily by the description alone. "YYe separate the sub- 

 genus Odynerus into four divisions for the better, arrangement 

 of the species. Unfortunately the transitions from one form to 

 another are so gradual, that it seems impossible to define them 

 clearly enough. But this is the greatest difficulty in all the 

 divisions of the genus Odynerus. 



These four divisions are as follows: — 



1. Hypodynerus. — Body depressed or stubbed. Thorax not 

 angulate before. Abdomen rather petiolate or sessile, depressed ; 

 the first segment either quite funnel-shaped as in Montezumia 

 or peculiarly cut, so that its triangular anterior face fits against 

 the metathorax and its superior face is transverse, very short, 

 parted by a groove; the separating ridge rounded or swelled like 

 a transverse pad. Post-scntel not distinctly truncate. 



1 Consult, at the end of the genus, the list of the species incertce sedis and 

 of the species dubice. 



