ROCKY MOUNTAIN BEES 187 



COLLETOIDEA [Colletiformes] 



Prosopididae 



(Two submarginal cells; no polleniferous scopa) 



COLLETIDAE 



(Three submarginal cells; polleniferous scopa present) 



B. Tongue filiform; no facial foveae; maxillary palpi shorter than blade of maxilla. 



1 Two submarginal cells; labrum longer than wide. 



TRYPETOIDEA [Megachiliformes] 



Stelididae [Stelidinae and Anthidiinae] 



(Claws cleft, inner tooth subapical) 



Megachilidae [Megachilidae, excluding Stelidinae and Anthidiinae] 



(Claws simple, sometimes with a basal tooth) 



2 Three submarginal cells; labrum wider than long. 



a Apex of sixth abdominal segment with a spine or mucro, 

 a little concave before the point; maxillary palpi 6-jointed. 



CERATINOIDEA [Xylocopiformes] 



Ceratinidae (Stigma large) 



Xylocopidae (Stigma obsolete) 



b Apex of sixth abdominal segment obtuse, without a spine 

 or mucro. 



APOIDEA [Apiformes] 

 Apidae (hind basitarsus shorter than tibia) [Apidae and Bombidae] 



PYGIDIALIA [Andreniformes] 

 (Sixth abdominal segment exserted or retracted, with a pygidial area) 



A. Tongue acute, fiat, rarely filiform; second to fourth joints of labial palpi simple; 

 stigma large, rarely middle-sized. 



ANDRENOIDEA 



Tegulae very large; labial palpi simple; tongue lance-linear, acuminate. 



Nomiidae [Nomiinae] 

 Tegulae ordinary. 1 



1 Labrum free from mandibles, as large as clypeus, shorter than wide, 

 transversely striate, without basal process; labial palpi simple. 



Dufoureidae [Halictoides] 

 Labrum ordinary. 2 



2 Hind tibia and basitarsus broad, with dense simple hairs; labial 

 palpi simple. Macropodidae [not in our fauna] 

 Hind tibia and basitarsus ordinary. 3 



3 Marginal cell truncate; two submarginal cells (three in Protan- 

 drena); facial foveae present. Panurgidae 

 Marginal cell pointed; usually three submarginal cells. 



4 



4 No facial foveae; basal nervure strongly bent or arcuate. 



Halictidae [Halictinae] 

 Facial foveae present; basal nervure slightly arcuate. 



Andrenidae [Andreninae] 



B. Tongue filiform; first two joints of labial palpi flat; labrum large, without basal pro- 

 cess; stigma small or middle-sized, rarely large. 



