1. Mandible of female with five or more teeth separated by acute notches; with the following combination of other characters: arolia absent; basal vein of forewing several vein widths basal to cu-v; base of propodeal triangle minutely roughened, punctate, hairy, without series of pits; postspiracular fovea of propodeum absent; juxtantennal carina absent....Anthidium
Mandible of female with three or four (rarely five) teeth, at least some of them separated by obtuse or rounded emarginations, rarely distal margin edentate except for small tooth near lower margin; without the combination of other characters listed above.....2
2. Middle tibia with two apical spines; scopa absent....Stelis
3. Propodeum with fovea delimited posteriorly by a carina behind spiracle; omaular carina present....4
Propodeum without fovea behind spiracle; omaular carina absent or weak....Trachusa
4. Apex of middle tibia without tibial spine or angular vestige of spine, but with convex carina (with dense short hairs beneath) across tibial apex, curving basad anteriorly, forming edge of broad, scoop-shaped concavity on apical tibial surface; apical margin of mandible of female strongly oblique, about half as long as mandible.... Paranthidium
Apex of middle tibia with angle or short spine on outer side, without preapical concavity; apical margin of mandible of female usually less oblique and often less than half as long as mandible....5
5. Subantennal suture long and distinctly arcuate outward; preoccipital ridge behind vertex strongly carinate and produced posteriad, covering pronotum; scutellum ending as sharply margined truncation (with small median emargination) overhanging metanotum and propodeum ....Anthidiellum
Subantennal suture more or less straight; preoccipital ridge behind vertex not or moderately carinate, not produced posteriad; scutellum not truncate, or, if so, then sharply margined only laterally.... (other characters: anterior margin of scutum abruptly declivous; posterior margin of metanotum, lateral to metanotal pit, with area of short white hairs) ....Dianthidium
