312 HOIEX0PTERA OF AMERICA. [PART I. 



2 magnse in basi secundi abdominis segmenti, albidse. Alse nigro- 

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



Odyn. luctuosus Sauss. Et. Vespid. Ill, 220, 114 (1854). 



This Odynerus has many characters in common with the O. 

 i-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. biclens, if its form and punctuation were not 

 wholly different. 



Hah. America. Which part, not knowm. 



II. Metathorax not forming erect spines or crests behind the 

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

 sciitel. This last not posteriorly truncate, but angular. 

 Post-scutel generally yellow, scutel usually black. 



The great number of species composing this group, and the 

 intimate relations which they bear to each other, make me 

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

 species are all of moderate or small size. 



1. Body 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. Tliorax rather elongate, 

 vaulted, subcylindrical. 



(Group of 0. conformis.) 



This group represents the true Stenodynerus with elongate, 



slender, cylindrical forms Among the Stenancistrocerus this 



has quite a corresponding facies in the group ot A.fulvipes, so that 



one may find it difficult to distinguish some of the corresponding 



