Fossorial ITymcnoptera of North America. 99 



concolorous. wings slightly clouded on the upper half, fore femora 

 black, with a long triangular yellow stripe at tip, two hind pairs en- 

 tirely black; tibiae entirely yellow, except on hind pair which are 

 black at tip. thickly spinulated, spinules not however arising from tuber- 

 cles; tarsi all brown black. 



Abdomen long and narrow, convex above and beneath, a little 

 shorter than the head and thorax together ; basal ring considerably 

 swelled and separated by a well defined suture from the succeeding 

 segments. Lateral fasciae yellow, not sinuate, uone on basal ring, and 

 diminishing in size from first pair, and thus growing more remote 

 above. Two terminal joints of the abdomen unusually hirsute, tip 

 broadly spatulate, sides slightly ridged, surface broad and flat. 



Length of body, .30 ; head and thorax together, .18 ; abdomen, .1-4 

 inch. 



Illinois, (Coll. Mr. Norton). 



This interesting species may be at once known by its obsoletely bi- 

 dentate mandibles, its peculiar sculpturing of the propodeum, and its 

 broad spatulate hirsute tip. It is not usual for the fifth ring to be so 

 hirsute. Also the well spinulated tibise, the spinules not as usual 

 when present, arising from stout tubercles ; together with the inflated 

 basal ring of the abdomen, which is entirely jet black, — present tren- 

 chant characters which show it to be a transitional form connectinir C. 

 pauper and C. denticulatus and its allies, all being undersized species 

 with rather stout bodies, and the abdomen much stouter than the head 

 and thorax together — with Tlujreopus vicinus and the species allied 

 which have a short head, the abdomen longer than the head and thorax? 

 and a spatulate tip, not pinched up and deeply channelled as usual in 

 the more typical forms of the genus Crabro. The remarkable length of 

 the much compressed lingua, the tip of which extends an unusual dis- 

 tance beyond the lateral lobes, is an interesting characteristic of this 

 species. 



Group G. 



Crabro obscurus, Smith. 



Crabro obscurus, Smith, Cat. Hym. Br. Mua. iv. p. 41S. (1S.J6.) 



9 . Head a little less than one-half as long as broad, being trans- 

 versely oblong, but a little shorter than in 0. Q-maculatus ; vertex flat- 

 tened, a little depressed below the surface of the eyes, which reach nearer 

 the posterior edge of the occiput than in C. Q-maculatus, and thus this 

 portion of the vertex forms an imperceptible ridge behind the ocelli 

 which are arranged in an equilateral triangle; front encroaches slightly 



