194 UNIVERSITY OF COLORADO STUDIES 



65 Abdomen wholly or largely red. 66 

 Abdomen not red, or if at all red, that color due to hair. 67 



66 Basal nervure strongly arched; small species. Sphecodes (43) 

 Basal nervure nearly straight. Andrena (36, 4q) 



67 Second recurrent nervure with a strong double curve, approaching an S-shape; tongue 

 short and emarginate; hairy bees. Colletes (42) 

 Second recurrent nervure not so formed, straight or with a single gentle curve. 



68 



68 Lower inner corner of second submarginal cell produced; large hairy bees with very 

 long tongue. 69 



Second submarginal cell not thus formed. 70 



69 Females with shining pollen-collecting surfaces on hind legs. Bombus (45) 

 Females with unmodified hind legs, covered with hair. Psithyrus (44) 



70 Basal nervure strongly arched; stigma well developed; tongue dagger-like. 



Halictus (35) 

 Basal nervure straight or almost. 71 



71 Hind margins of abdominal segments with beautiful pale greenish tegumentary bands, 

 the other parts of the abdomen strongly punctured (Boulder). 



Nomia universitatis Ckll. 

 Abdomen without greenish bands. 72 



72 Stigma well developed; apex of marginal cell on or very near costal margin. 



73 



Stigma little developed; apex of marginal cell away from costal margin. 



74 



73 Posterior face of metathorax flat, shining, sharply separated from basal area, which 

 is strongly rugose; tibiae and tarsi bright ferruginous; hind tibiae of male deformed, 

 wings yellowish, apical margin strongly dusky (Boulder, September 16, Rohwer; 

 Denver, at flowers of Solidago, August 24, Mrs. C. Bennett). Nomia bakeri Ckll. 

 Posterior face of metathorax not thus differentiated; tibiae of male not deformed. 



Andrena (36, 49) 



74 Vertex smooth, brilliantly shining; form compact; male abdomen bidentate at extreme 

 apex. Diadasia (41) 

 Vertex less shining; abdomen otherwise formed at apex. 75 



75 Maxillary palpi 6-jointed; scopa of hind legs in female simple. Tetralonia (37) 

 Maxillary palpi 4-jointed; scopa plumose. Melissodes (38, 48) 

 Maxillary palpi 5-jointed. Xenoglossa (39) and Xenoglossodes (40) 

 The following table separates a series of females of the last two genera: 



Abdomen red; large robust species (New Mexico) . 



Xenoglossa patricia Ckll. 

 Abdomen not red. 1 



1 Lower margin of clypeus broadly yellow (New Mexico). 



Xenoglossodes gutierreziae Ckll. 

 Clypeus without yellow. 2 



2 Flagellum bright ferruginous beneath, except at base (Roswell, New 

 Mexico). Xenoglossodes excurrens Ckll. 



