ODYNERUS. 220 



abdomen is perfectly sessile, conical ; its first segment is wide, 

 often quite as wide as the 2d, squarely truncate at its base, which 

 permits the distinction of an anterior and a superior face ; the 

 transverse ridge which results from this truncation is sometimes 

 blunted, sometimes sharp. The superior face is always transverse, 

 wider than long. The abdomen is sometimes velvety, sometimes 

 smooth, shining, not rugose, and the first segment is wholly 

 smooth, less punctured than the 2d. 



It is fitting to say that for each one of these characters, there 

 may be met some exception among this and that species. 



Of all the Odynerus, the species of this Division have the most 

 cubical thorax and the most conical abdomen. Yet they have 

 almost the same form as a great part of the species of the Division 

 Odynerus which follows, and are only distinguished from them 

 by the antennae of the males, which are destitute of the terminal 

 hook. Owing to this circumstance the Pachodynerus occupy 

 among the Odyneri a sort of typical position like that of the 

 Eumenes of Division Omicron, these being also distinguished 

 from the other Eitmenes by the simple flagellum of the antennas 

 of the males. The Pachodynerus are also, like the Eumenes of 

 the Division Omicron, peculiar to tropical and temperate America. 



The Pachodynerus cannot easily be confounded with the Sleno- 

 dynerus, because of their thick body and conical, thick abdomen. 

 But, to make certain, one should consult the tables of the spe- 

 cies of the Division Odynerus, which are placed before these 

 Divisions. 



Table to assist in distinguishing the species of the Division Pachodynercs. 



1. Ornaments of the body all yeilow. 



2. Abdominal segments all margined with yellow, except the first. 



3. Thorax wholly black. 



4. Metathorax rounded, destitute of lateral angles. 



u'9. argentinus. 



4, 4. Metathorax forming an angle on each side. 



5. Thorax elongate, metathorax with four spines ; insect black. 



cH>. diabolicus. 

 5,5. Thorax cubical; metatliorax with two angles; insect vel- 

 vety, grayish. 66. brevi thorax. 



66. i brevitho\ 

 3,3. Thorax with yellow ornaments. nasidens. 



b'S. * sii 



