304 HYMENOPTERA OF AMERICA. [PART I. 



A. Upper face of thorax prolonged beyond the post-scutel, involving it 

 behind. Stenodynerus. 



B. Thorax not prolonged superiorly behind the post acutel. 



0. Post-scutel entire, angulate behind. Stenodynerus. 

 b. Post-scutel truncate posteriorly, having a posterior face. 



f First abdominal segment short, truncate anteriorly, its superior 



face wider than long. Odynerus. 



ft First abd. segment subpedunculate, funnel-shaped or cup-shaped. 



Stenodynerus. 



C. Abdomen thick, conical, widest anteriorly. Odynerus. 



D. Abdomen not so conical. 



a. First segment truncate anteriorly. 

 a. Its superior face wider than long. 



* Post-scutel truncate ; abdomen ovate-conical. Odynerus. 



** Post-scutel not truncate ; abdomen slender 1st segment more 

 punctured than the 2d. Stenodynerus. 



8. Its superior face about as long as wide. Stenodynerus. 



b. Abdomen slender, cylindrical; first segment bell-shaped, sessile, 

 rounded anteriorly, as long as wide. Stenodynerus. 



c. Abdomen more ovate, first segment smaller, cup-shaped. 



Stenodynerus. 



d. Abdomen slender, spindle-shaped; first segment funnel-shaped. 



Stenodynerus. 



E. First abd. segment less punctured than the 2d, or equally punctured 

 with it. Odyni rus. 



F. First abd. segment more punctured than the 2d or equally with it. 



Stenodynerus. 



G. Post-scutel entire, angulate behind. Stenodynerus. 

 II. Post-scutel truncate posteriorly. 



a. Abdomen sessile, or subsessile, truncate at base. Odynerus. 



b. Abdomen subpedunculate, 1st segment funnel-shaped. 



Stenodynerus. 



It is almost superfluous to say that these distinctions arc not 

 mathematical, nature always forming transitions which oblige us 

 to admit a certain latitude in the exceptions and in the meaning 

 of the definitions. 



Table to assist in the determination of the Stenodyneri. 



1. Wings black, with violet iridescence. 111. lucluosus. 

 1, 1. Wings cloudy, ferruginous, or subhyaline. 



2. A crest or two erect spines behind the post-scutel. 

 3. Metathorax strongly biangulate, and bidentate superiorly. 



112. spin if er. 



3, 3. Metathorax superiorly margined with a semicircular ridge. 



113. araucanus. 



