Fossorial Hymenoptera of North America. • 355 



Synopsis of Species. 



A. Vexhillura present. 



a. Antennae broad and flattened, dentate. 



% . Vexhillum leaf-like, tip very acute T. latipes, Smith. 



% . Vexhillum suborbicular, lobulated, leaf-like T. coloradensis, Pack. 



% . Vexhillum obtusely triangular, scutellate, very con- 

 vexly lobed behind, covered with dots; anterior 

 margins obsolete T. cribrellifer, Pack. 



%. Vexhillum acutely triangular, semicordate. Ungues 



present T. argus, (Harr.) 



6. Antennae subsimple. 



% . Vexhillum short sub-orbicular, scutellate; fuscous 



yellow spots on the thorax T. signifer. Pack. 



c. Antennae simple. 



% . Vexhillum less triangular, expansion short, half as 



long as joint itself T. pegasus, (Harr.) 



%. Vexhillum scpiare, brown, with a few yellow stripes, 

 antennae slightly fusiform; basal joint of abdomen 

 faseiate T. discifer, Pack. 



%. Vexhillum rboniboidal, anterior edge concave, poste- 

 rior convex; abdomen with the basal joint tumid, 

 black T. tumidus, Pack. 



B. Vexhillum absent, and instead a brush of hairs. 



%. Basal joint of abdomen with a yellow band T. singulatus, Pack. 



J. Very large, with large yellow fascia on second ring 



beneath. % unknown T. monticola. Pack. 



9- Fore femora tipped with yellow T. advenus, Smith. 



9. Unusually large broad band on basal abdominal ring, 



but one terminal continuous band T. conspicuus, Cress. 



9 . One-half as large as preceding, thorax black, abdomen 



with two slight basal sinuate fasciae T. succinctus. Cress. 



9. Yellow stripe on meso-scutellum, but one terminal 



band T. vemalis, Pack. 



Thyreopus latipes. 



Crabro gryphus, Harr. Cat. Ins. Mass. p. 68. (1835.) 

 Crabro latipes, Smith, Cat. Hym. B. M. IV. p. 396. (1856.) 

 not C. latipes, Cresson, Proc. iv, p. 477. (1S65). 



% . Closely resembles C. coloradensis, while the head is more 

 transverse and smaller than in T. cribrellifer ; surface puncto-striated, 

 but not so distinctly striated as in C. coloradensis, with a slight hir- 

 suties between the ocelli and antennal groove; clypeal region a little 

 longer and narrower than in C. coloradensis ; clypeus yellow on each 

 side of the carina, mandibles yellow on the basal half, tips rufous, an- 

 tennae as in T. coloradensis, flagellum being much wider than in T. 

 cribrellifer ; scape compressed, yellow beneath, black above, flagellum 

 black. 



Prothorax punctured, with a denticle on the side anteriorly, with a 



