Studies of North American Bees 59 



Males 



Joint 3 of antennae fully two-thirds as long as 4, or more; lateral face 

 marks extending up along orbits to summit of eye i 



Joint 3 of antennae distinctly less than two-thirds as long as 4, usually 

 about one-half as long; lateral face marks not nearly attain- 

 ing the summit of the eye 2 



I. Legs red, the anterior legs in front and anterior face of middle 

 tibiae yellow, the coxae behind and stripes on the hind femora 

 and tibiae, black ; usually only one or two submarginal cells 



in one or both wings ; 6-9 mm obliterata 



I. Legs yellow, with contrasting black spots or stripes on the coxae, 

 trochanters and femora behind, typically without any reddish 

 sufifusion except on the hind tarsi but sometimes with reddish 

 margins to the black spots on the posterior face of the femora 

 and tibiae and reddish areas on the anterior face of the pos- 

 terior femora and tibiae ; wings with three submarginal cells ; 

 9-10 mm civilis 



•2. Joint 3 of antennae very short, not over one-third as long as 4, and 

 joining 4 obliquely : legs mostly red, only the anterior legs in 

 front and the knees Yellowish, the coxae, last four trochanters 

 and femora, and a stripe on hind tibiae marked with black on 

 posterior face ; continuous, clear-cut yellow bands on tergites 

 1-6, narrowed medially on 2 and 3 ; 7.5-8 mm fragilis 



2. Joint 3 of antennae about one-half as long as 4 3 



3. Legs yellow, the coxae and trochanters behind and the posterior 

 coxae in front, a small spot at extreme base of anterior femora 

 and areas involving almost all of posterior face of hind femora 

 and their anterior face except the apex, black, the middle 

 femora except knees and stripes on last four tibiae reddish to 

 dusky; elevated portions of mesoscutellum and metanotum and 

 a large transverse pleural spot, bright yellow; tergites 1-6 

 with broad complete yellow bands, only slightly narrowed on 



2, apex wholly yellow ; 9 mm citrina flavomargiiiata 



3. Legs red, not heavily marked with yellow or black; mesoscutellum 

 with two red or yellow spots of variable size, rarely coalesced ; 

 pleural spot smaller, confined to anterior portion of meso- 

 pleura 4 



4. Clypeus practically bare ; legs with distinct yellowish sufifusions on the 

 anterior pair in front, on all the knees and tarsi, and on the 

 middle tibiae in front on most specimens, sometimes all these 

 are concolorous ; 8.5-10 mm crawfordi 



4. Clypeus rather densely covered with silky appressed silvery hair; legs 



much less inclined to yellowish suffusions ; 7-9 mm 5 



5. Mesoscutum and mesopleura black ; vertex black ; propodeum black 



59 



