Studies of North American Bees 19 



received through Mr. O. A. Stevens which I beHeve are repre- 

 sentative of five species, separable as follows : 



Males 



Joint 3 of antennae subequal to 4. 



Mesoscutum red with a median line and narrow anterior and posterior 

 margins black; larger species, 6-8.5 mm. long; apical margins of 

 tergites usually not strongty infuscated, if at all. 

 Tergites 2 and 3 merely with lateral spots. 



Propodeum with broad red bands, tergite i with a trilobed 

 black mark at base; sutural black of mesopleura not en- 

 croaching on the disk; black of face below antennae con- 

 fined to the clypeal and supraclypeal sutures, leaving the 

 supraclypeus red ; tergites 2 and 3 always with yellow spots, 



6 always immaculate ; larger, 7-8.5 mm riibi 



Propodeum wholly black, or (25 per cent.) merely with red 

 spots or stains on the enclosure; basal one-third of tergite 

 I black right across ; black of mesopleura encroaching on 

 the disk, usually leaving a large red patch anteriorly and a 

 small subtegular spot; face above clypeus, except the narrow 

 orbital margins, black; tergites 2 and 3 with lateral spots, 

 those on 3 (8 per cent.) sometimes lacking, 6 often (28 

 per cent.) with two yellow spots; smaller, 5.5-8 mm.. subrubi 

 Tergites 2-3 with complete or narrowly medially interrupted yellow 



bands ; 6-7 mm lepida var. 



Mesoscutum black or with four red lines ; very small, only 5 mm. 

 long; apical margins of tergites infuscated so as to form transverse 



bands ; 5 mm. long fuscicincfa 



Joint 3 of antennae only about one-half as long as 4; scape swollen; 5-6.5 

 mm. long hydrophylli 



Females 



Mesoscutellum deeply bilobed ; upper clypeal and supraclypeal sutures 

 broadly black ; mesoscuturrt unilineate ; 7-9 mm. long. 



Tergite 3 with small lateral yellow spots, the base of tergite i with the 

 black mark small and trilobed, with the lateral lobes longer; pro- 

 podeum red on the posterior face except for a median band on en- 

 closure; third submarginal cell usually narrowed to a point above, or 

 almost so ; size larger, 8-9 mm., usually 9 mm rubi 



Tergite 3 normally immaculate, occasionally (8 per cent.) with small 

 lateral yellow spots, the base of tergite i black i-ight across or nearly 

 so ; propodeum normally black with large red areas on the upper 

 posterior face, these sometimes involving all of the posterior face 



^73 



