METHOD OF DETERMINING GENERA. 177 



Three submarginal cells to the wings. 



Abdomen truncated at base . . . COLLETES (I). 

 Abdomen ovate. 



Abdomen entire at apex ; maxil- 

 lary palpi as long or longer than 



the maxillfe ANDRENA (4). 



Abdomen entire at apex ; maxil- 

 lary palpi half the length of the 



maxillae CILISSA (5). 



Abdomen with a vertical incision 



at the apex HALTCTUS (7). 



Posterior tibia ivithout hair to convey pollen. 

 Two submarginal cells to the wings f . PROSOPTS (2). 

 Three submarginal cells to the wings . SPHECODES (3). 



APID^E (Normal Bees) . 



TONGUE AS LONG OR LONGER THAN THE MAXILL.E, IN- 

 FLECTED BENEATH, AND COVERED BY THE MAXILLAE IN 

 REPOSE. 



Without polliniferous organs. 



Two submarginal cells to the wings. 



Abdomen at apex rounded . . . STELTS (17). 

 Abdomen at apex conical .... C(ELIOXTS (18). 

 Three submarginal cells to the wings. 



Abdomen lanceolate NOMADA (14), 



Abdomen subtruncate at base. 



Abdomen obovate, thorax glabrous EPEOLUS (16). 

 Abdomen subconical, thorax hir- 

 sute MELECTA (15). 



Entire body densely hairy . . . APATHUS (25). 



With polliniferous organs, 



Pollen conveyed on the venter. 



Two submarginal cells to the wings of all. 



