312 HYMEXOPTERA OF AMERICA. [PART I. 



2 magna 1 in basi secnndi abdominis segnienti, albklse. Alae nigro- 

 violacese. — Longit. 20 mm. ; alse, 17 mm. 



Odijn. luctuosus Sadss. Et. Vespid. Ill, 220, 114 (1854). 



This Odynerus lias many characters in common with the O, 

 4-sectus; tubercle of 2d segment (here much m redeveloped); 

 form of clypeus, brush of vertex, superior termination of meta- 

 thorax : but it differs from it by the strong rugosities, by the form 

 of the striae of the head and thorax, and by its metathorax which 

 offers no trace of latero-superior ridges, so that the lateral ridges 

 are continued with the inferior ridges, in forming lateral trenchant, 

 but not acute angles. 



The first abdominal segment is a little funnel-shaped, truncate. 

 The maxillary palpi have the 2d article long and slender, and the 

 last three quite small, although longer taken together than the 3d. 



The two spots of the abdomen might cause this Odynerus to 

 be taken for the 0. bidens, if its form and punctuation were not 

 wholly different. 



JJab. America. Which part, not known. 



II. Metathorax not forming creel spines or crests behind the 

 post-scutel. Its superior face not produced behind the post- 

 scutel. This last not posteriorly truncate, bid angular. 

 Post-scutel generally yellow, scutel usually black. 



The groat number of species composing this group, and the 

 intimate relations which they boar to, each other, make me 

 doubtful of my success in defining them with certainty. — The 

 species arc all of moderate or small size. 



1. Bodij slender, cylindrical. Concavity of the metathorax 

 wide, sometimes rather distinctly limited. First abdominal 

 segment bell-shaped, rather elongate, widely rounded ante- 

 riorly, sessile or subsessile. Thorax rather elongate, 

 vaulted, subcylindrical. 



(Group of 0. conjormis.) 



This group represents the true Slenodynerus with elongate, 

 slender, cylindrical forms Among the Stenancistrocerus this 

 has quite a corresponding faeiesinthe group oi A.fulvipes, so that 

 oue may find it difficult to distinguish some of the corresponding 



