234 HYMENOPTERA OF AMERICA. [PART I. 



c. A yellow spot on each side between the eye and the clypeus. 



d. Prothorax slightly bordered with yellow on its anterior 

 angles. 



e. Prothorax not bordered with yellow, with quite golden 

 reflections. 



f. Antenna? quite black. (Bahia.) 



g. Tibiae with yellow lines or wholly black. 



% . Clypeus polygonal, argenteous, widely margined with yellow 

 on both sides; its anterior margin widely truncate. Antennae 

 fulvous beneath; the scape with a yellow line; lower part of the 

 eyes bordered with yellow. 



Var. Clypeus quite yellow, with a black spot or line in the 

 middle. 



Mexican variety. 9- — Mandibles black to the end. Antenna? 

 ferruginous beneath, except at the extremity, and becoming 

 brown ferruginous. Tibia? all ornamented with yellow. There 

 are often two yellow dots on the front; the teeth of the clypeus 

 only, red. — Mexico. 



Small variety. 9. — Of the size of the 0. brevithorax, but offer- 

 ing the same characters as the above variety. Borders of the 

 metathorax more rounded. — %. Antenna? and legs as in the 9 

 variety. — Mexico. 



Bess. a. diff. — This species differs from the 0. brevithorax, 

 in its greater size, in its thorax longer than wide although very 

 square, in its clypeus 9 less wide, but strongly bidentate, in the 

 disk of the mesothorax a little attenuated before, having the 

 latero-anterior borders a little sinuate. The male differs, by its 

 polygonal clypeus, truncate, not bidentate. 



It approaches yet more closely to 0. simplicicornis. — Com- 

 pare these species. 



Hab. Tropical America. I possess a great number of speci- 

 mens. 1st. From the hot parts of Mexico (Huasteca, Oriental 

 ( lordillera, Michoacan, etc.); 2d. From Colombia and Venezuela ; 

 3d. From Bahia and Brazil. They do not appear to me to differ 

 specifically. 



Although the description given by Latreille of his 0. nasidens 

 does not agree well with our specimens, we do not retain any 

 doubl as to the identity of the species. The description of Lat- 

 reille is evidently a hybrid description, being partly of a female, 

 partly of a male. When he said that the clypeus was bidentate, 



