252 IIYMENOrTERA OF AMERICA. [PART T. 



13, 13. Edges of the concavity of metathorax 

 more blunted. 105. molestus. 



12, 12. Scutel black. 



13. Fascia of the first abd. segment narrow; 

 ornaments pale. 103. leucomelas. 

 13, 13. Fascia of the first abd. segment wider; 

 yellow. 102. if oraminatus. 



107. ^-flavopictus. 

 10, 10. Second segment with lateral yellow maculae oi 

 fascia. 104. blandus. 



8, 8. Superior angles of metathorax not produced behind 

 the post-scutel or scarcely produced. 

 9. Second segment without lateral yellow spots. 

 10. Metathorax strongly excavated, rough ; all the 

 segments margined with yellow. 



105. molestus. 

 10, 10. Metathorax not strongly excavated, not rough ; 

 2, 3 segments margined with yellow. 



109. Romandinns. 

 9, 9. Second segment with lateral yellow spots or fasciae. 



104. blandus. 



Description of the species. 



Section I. — Post-scutel sharply truncate; its transverse edge 

 often crenulate. Abdomen conical? or ovate-conical ; the 

 second segment not strangulated at base ; the first segment 

 including it very naturally. 



1. Posterior plate of metathorax angulate, forming on each side 

 a lateral dentiform angle. (Thorax square, angulate, poste- 

 riorly wide, not contracted. Abdomen very conical.) 



A. Concavity of the metathorax polygonal, margined with straight 

 or arcuate ridges, which form at their meeting a sharp angle. 

 TJie superior lateral edges superiorly terminating in a, tooth 

 or eminence, separated from the p)ost-scutel by a deep fissure, 

 or by a notch. 



These teeth are more distinct in the males than in the females, 

 sometimes obsolete in the females. 1 Comp. Sec. B. 



a. Ridges of the metathorax vertj salient ; its posterior face excavated. 



* Posterior margin of 2d and 3d abdominal segments reflexed. 



82. O. Hidalgi Sahps. — Niger, crasse cribri instar punctatus ; clypeo 

 in utroque sexu truncato ; metanoto valde concavo, biangulato, cauthis 



1 Principally in Odyn. Boscii and dorsalis. 



