Fossorial ITymcnoptera of North America. 79 



Colorado Territory, Ridings, (Coll. Ent. Soc. Phil.) 

 This is a very slender species, the most so of any observed in this 

 section of the genus. The large stout teeth of unusual proportions, 

 the long narrow clypeus, the finely crested prothorax and black meso- 

 notum, and black body generally, the black femora, the coarsely sculp- 

 tured propodeum and the long, slender produced abdomen, together 

 with the great differences in coloration between the two anterior and 

 posterior pairs of tarsi will distinguish this from all the other species 

 of this section of the genus. 



Group B. 

 Crabro 10-maculatus, Say. 



C. lQ-maculatu8, Say, West. Quart. Rep. ii. p. 78. (1823.) 

 Harris, Cat. Ins. Mass. p. 68. (1835.) 



9 . Head a little more cubical, being a little longer than in C. arcu- 

 atits. Eyes larger, sculpturing the same. Front not hairy; antennal 

 groove nearly covered in by the golden pubescence extending from the 

 orbits, which is of a deeper hue on the clypeus, but on the lateral lobes 

 is silvery; clypeus and the lateral pieces as described in G. arcuatus ; 

 mandibles yellow, black at tip, tridentate, two outer teeth nearly equal 

 in size, inner the more minute of the two, and on the basal half a stout 

 triangular tooth. Antennae long, slender, clavate; scape long, slightly 

 dilated within, entirely yellow, basal joint and base of second joint of 

 the flagellum yellow; remaining joints black; sutures distinct as usual, 

 but tip not dilated as usual. 



Prothorax strongly banded with yellow, the two bands more conti- 

 guous than usual ; on the flanks two yellow spots, one the tubercle, the 

 other a square oblique yellow spot behind it; scutellum and meta-scu- 

 tellum yellow, the scutellum appendiculated by two lateral yellow spots 

 yling contiguous to it. Thorax more coarsely punctured than in G. 

 arcuatus. Enclosure of the propodeum coarsely punctured, but. with 

 hardly any radiating lines; on the scutum are a few coarse, transverse 

 rugfe, with coarse punctures betweeu them. Wiugs as in G. arcuatus, 

 anterior legs yellow, femora black on the upper side, and tips of tarsal 

 joints slightly ferruginous; middle and hind femora colored much alike, 

 black at base, shading into ferruginous, and then becoming yellow at 

 tip; tibiae entirely yellow, tarsi yellow, tips of terminal joints becoming 

 ferruginous. Abdomen with ten yellow fasciae, basal pair sinuate, of 

 the same distance apart above as in G. arcuatus; last pair most conti- 

 nuous; tip mucronate, narrower than in G. arcuatus; a smooth space 

 above on the preceding ring. 



