Fossorial Ih/menoptera of North America. 397 



stout, much thickened towards the ends, joints large and heavy, third 

 joint trapezoidal in outline, subglobular; flagelhun unusually clavate, 

 thickened especially just before the tip. 



Thorax short and thick; prothorax short, very narrow transversely, 

 with a ridge above, which is interrupted by a slight mesial impression ; 

 meso-scutum broad and short, impressed line very faint, submesial 

 ridge obsolete ; parapsidal groove quite distinct. Scutellum smooth, 

 just twice as broad as long; meta-scutellum short, very transverse and 

 puncto-striated. Pterostigma small, third cell not triangular as in 

 Mimesa, but irregularly oval lanceolate, 2d subcostal cell nearly trian- 

 gular, as the upper or anterior side is much contracted, since the 

 two subcosto-median recurrents closely approximate, while in Mimesa 

 the area is regularly trapezoidal ; second median cell much more pro- 

 duced than in Mimesa; outer side of 2d submedian cell is much more 

 curved than in Mimesa ; propodeum much as in Mimesa, scarcely 

 differing, the enclosure being very distinctly and acutely triangular, 

 equilateral and acutely pointed ; posteriorly it is on each side full and 

 convex, rather short and well rounded downwards. Le^s not so stout 

 as in Mimesa; tarsi much slenderer. 



Abdomen with a long and slender pedicel, as long as the breadth of the 

 abdomen itself, the body of which is a little longer than the head and 

 thorax together, segments slightly emarginate, contracted at the su- 

 tures, tip very acute, point slightly channeled above. 



The species of this genus are generally almost entirely black. Com- 

 pared with Mimesa, the head is much more cubical, antennae less 

 clavate. eyes narrower, front broader, clypeus less rounded on the 

 front edge, thorax more spherical, abdomen much broader, the tip of the 

 abdomen more or less grooved in most of the species, while in Mimesa 

 it is flat and not grooved at all. It is thus much more closely allied to 

 Mimesa than the genera Pemphredon, Cemonus and Stigmus or Pas- 

 salaecus, by its more transverse head, and cephalic characters enu- 

 merated above, such as the transverse rather flat sublunate clypeus, 

 the vertex, which is antero-posteriorly compressed, and the very clavate 

 antennaa. In the wing-characters it also, with Mimesa, differs in pos- 

 sessing an additional subcostal cell, in the greatly lengthened median 

 cell, and the enlarged and broad 2d submedian cell, which thus shows 

 its analogy with the NyBSonidse. The two genera by their affinities 

 with the Nyssonidae, connect the Crabronidoe with that family, and afford 

 au easy passage into the former, as seen in the singular triangular en- 

 closure on the propodeum, which differs very considerably from 



