76 Descriptions of new species of Hymenoptera. 



a black spot, their tibiae dusky at tip and their tarsi yel- 

 low; abdomen black at tip and on the superior edge of 

 the second segment, which is at least as long as the first 

 segment. 



Length $ nearly three-fifths of an inch. 



3. 0. geminatus. Yellowish; vertex with a black spot; 

 larger central cellule of the wings obtuse at tip. 



Inhab. Indiana. 



Body dull yellowish; head yellow; verier black; an- 

 tennae somewhat shorter than the body, tinged witli 

 brown, the first joint yellow; icings hyaline, with fus- 

 cous nervures and honey-yellow somewhat dilated carpal 

 spot; larger central cellule obtuse at tip, the nervure of 

 the tip double; smaller central cellule very obtusely 

 rounded at the superior basal angle; pleura and pectus 

 pale yellowish ; abdomen, second segment obviously 

 shorter than the first, and not longer than the third. 



Length about two-fifths of an inch. 



This species closely resembles O. bilineatus, Nob. but 

 is much smaller, and the arrangement of the wing-ner- 

 vures prove it to be a different species. 



4. 0. emarginalus. Black ; antennas fuscous ; feet 

 honey-yellow. 



Inhab. Indiana. 



Body black, sericaous with short hair ; head convex 

 beneath the antennas, at the base of which the head is 

 much more prominent than immediately above the an- 

 tennas where the head is indented; antennae short, above 

 dark fuscous, beneath paler, first joint rather large; palpi 

 white; thorax immaculate; mctathorax with four longi- 

 tudinal slightly raised lines; wings hyaline with fuscous 

 nervures and carpal spot; larger central cellule obtuse or 



