ROCKY MOUNTAIN BEES 1 93 



5 1 Fifth segment of female abdomen with large patch of silvery hair. Triepeolus (29) 

 Silvery patch reduced to a lumule or band; insects usually smaller. Epeolus 



52 Mandibles simple. Nomada 1 (30) 

 Mandibles with an inner tooth. Nomada, subgenus Gnathias (30) 



53 Head and thorax with metallic colors, blue or green. 54 

 Head and thorax black, rarely with some red, never metallic. 58 



54 Head and thorax brilliant emerald green or blue green; basal nervure strongly arched. 



55 



Head and thorax dark green or blue. 56 



55 First recurrent nervure joining second submarginal cell near middle; male abdomen 

 banded with yellow and black, female abdomen green or black. Agapostemon (34) 

 First recurrent nervure reaching apex, or very near apex, of second submarginal cell; 

 abdomen green like thorax in both sexes. Augochlora (32) 



56 Small, shining dark green bees; first recurrent nervure joining second submarginal 

 cell near apex; tongue long; face in female with an ivory spot, in male with a large 

 tri-lobed ivory mark. Ceratina (^) 

 Minutely punctured bees, with the head and thorax hairy; face without light markings 

 in either sex or (in male Halictus) with a small light band on clypeus; tongue 

 dagger-like. 57 



57 Basal nervure strongly arched; abdomen often not metallic. Halictus (35) 

 Basal nervure hardly arched. Andrena (36, 49) 



5 8 Mouth-parts greatly elongated, held under the body when at rest, like the beak of an 

 Hemipteron (Denver, Colo.). Melitoma grisella Ckll. and Porter 



Mouth folded and concealed when at rest. 59 



59 Marginal cell sharply truncate at tip, the lower corner with an appendicular nervure; 

 face largely pale yellow. Protandrena 

 Marginal cell not thus truncate, but obtuse or pointed. 60 



60 Face more or less yellow or white, the color tegumentary; basal nervure nearly 

 straight. 2 61 



Face without light tegumentary color. 65 



61 Stigma nearly always well developed; male antennae not greatly elongated; tongue 

 dagger-like. Andrena (36, 49) 

 Stigma little developed; male antennae usually elongated; tongue very long, linear. 



62 



62 Antennae very long, black; maxillary palpi 6-jointed. Tetralonia (37) 

 Antennae usually shorter, though long, and more or less reddish (in a few species black) ; 

 maxillary palpi with less than six joints. 63 



63 Maxillary palpi 4-jointed (many species). Melissodes3 (38, 48) 

 Maxillary palpi 5-jointed. 64 



64 Maxillary palpi comparatively long and slender. Xenoglossa (39) 

 Maxillary palpi shorter (genus not known in Boulder County). Xenoglossodes (40) 



1 For a table of Rocky Mountain Nomada, see Bulletin 04, Colorado Agricultural Experiment Station. 



* Some male Halictines have yellow on clypeus; these have the basal nervure strongly arched. If bright 

 green with yellow and black abdomen they are Agapostemon; if dark green, Halictus. 



3 Anthedon, a genus scarcely distinct from Melissodes, has the male antennae with the last joint elongated. 

 The scopa of the female is simple. 



