Fossorial Ilymenoptera of North America. 53 



scutellum are as in Cerceris, gradually rounded, the upper edges next 

 to. the scutum being horizontal. 



In the fore wings there are generally four sub-costal spaces, except 

 in Pemphredon and allies when there are but three. The wiug neura- 

 tion follows in its variation the groups of genera before mentioned, 

 and in each group the variation is very remarkably slight. 



In Ccrccris and allies the second costal space is oval lanceolate, both 

 ends being much alike in form. The second s. c. is small, triangular and 

 does not reach to the second costal, being pedunculated. The two 

 lower sides of the discal space are subequal. In Philanthus, outer 

 half shorter; in Mellinus, shorter still, and in Gorytes longer again. 

 The first median is long and narrow, shorter in Philanthus, rhouiboi- 

 dal (regularly) in Pemphredon and Mellinus, and long again in Gorytes. 

 In the secondaries, the median is continuous beyond its second ner- 

 vules with its base, but in the remaining genera the nervure is much 

 curved upwards after leaving its second or longest nervule. In Phi- 

 lanthus and Pemphredon, the second costal space is triangular, becom- 

 ing oval lanceolate again in Gorytes. In Philanthus, the second sub- 

 costal cell is sub-quadrate. In Pemphredon, the outer recurrent is want- 

 ing. In the second median space the outer side is nearly half shorter 

 than the lower, and the greatest length is to the internal in Cerceris, 

 Philanthus, while in Pemphredon the two sides are equal and parallel 

 to the costa. In Mellinus and Gorytes, they oppose Cerceris and 

 Philanthus more. 



The legs are the most spined, and the tibiae most trigonate in Cer- 

 ceris, slender in Philanthus, and short and slender in Ptmplmcdon, and 

 stout, approaching Crabro in Gorytes. 



There are three genera in the sub-family. 



The species of Cerceris have transversely oblong heads, the first 

 being straight above, smooth, flat fronts, a sub-globular thorax, and 

 long sub-cylindrical abdomen longer than head and thorax, the rings 

 contracted, and the first ring nearly half narrower than the suc- 

 ceeding ones. They approach nearest to the Vespidse by their toothed 

 jaws, fronts and clypeus, globose thorax, like them they are highly 

 colored, but they do not sting. The genus Eucerceris combines the 

 characters of the two other genera. 



Philanthus has a short head, but sub-oval transversely, since the 

 front seen from above is convex, the thorax is much as in Cerceris t 

 with the sessile abdomen shorter thau in C.j the first joint nearly 



