256 



NORTH AMERICAN DII'TKRA. 



44. Species wholly or chiefly reddish or lutescent. ... 46 

 Black species, sometimes with luteous spots on face, humeri and 



basal angles of abdomen. ....... 45 



45. Scutellutn unusually large, nearly square in outline; males dichop- 



tic Chalcomyia. 



Scutellum oval; males holoptic (27). . . . Myiolepta. 



46. Face carinate; abdomen oval. . . . ' . Brachyopa. 

 Face tuberculate; abdomen more elongate. Hammerschmidtia. 



47. Epistoma produced into a long porrect snout. . . Rhingia. 

 Epistoma not produced (compare Paragus sp. if small); facial 



orbits limited by a slender groove (8). . . . Chilosia- 



48. Third vein bent deeply into the first posterior cell. . . 51 

 Third vein not bent deeply into first posterior cell; third antennal 



joint elongate. ......... 49 



49. Arista very densely plumose, appearing as a solid mass, the arista 



itself also thickened (14) . .... Copestylum. 



Arista feathery plumose. ....... 50 



50. Hairs of arista ret rorse; males dichoptic. . Megrametapon. 

 Hairs of arista not retrorse; males holoptic (12, 13, 36). 



Volucella. 



51. Hind femora with a sharp tooth-like projection below near distal 



end; sixth vein beyond anal cell strongly curved; large species 



(20) • Milesia. 



Hind femora without such tooth. ...... 52 



52. Frontal triangle of male strongly protuberant; rather large, dark- 



colored species (Priomerus, Doliosyrphus.) . Eristalis. 



Frontal triangle not protuberant. ...... 53 



53. Epistoma produced into a long porrect snout. 



Licastrirhyncha. 

 Epistoma not produced. ....... 54 



54. Thorax with distinct yellow markings; hind femora thickened; 



hypopygium enlarged. .... Meromacrus. 



Thorax not with distinct yellow markings, sometimes white-fas- 

 ciate; femora sometimes thickened; hypopygium not conspicu- 

 ously prominent (17). . Eristalis. 



55. Arista plumose. ......... 56 



Arista ban- or pubescent. ....... 60 



