88 NOliTH AMERICAN DIPTERA. 



52. Frontal triangle of $ strongly protuberant (Doliosijrphus Bigot, Central 



and South America). .... Priomerus Macquart. 

 Frontal triangle not prominent. 53 



53. Epistonia proiluced into a long porrected snout (Central and South 



America). Lycastrirhyncha Bigot. 



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



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



enlarged (Pteroptila) Meromacrus Rondani. 



Thorax without distinct yellow markings; liind femora sometimes 

 thickened; hypopygium not prominent. . Eristalis Latreille. 



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



Arista hare or pubescent. ........ 58 



50. Antennic elongated Phalacromyia Rondani. 



AntennjE short. .......... 57 



57. Thinly pilose ; abdomen with yellow bands. Sericomyia Meigen. 

 Tiiickly pilose; abdomen without yellow. Arctophila Schiner. 



58. Third longitudinal vein bent deeply into the first posterior cell; hind 



femora thickened 59 



Third vein only gently curved "64-^(3 i 



59. Face carinate; hind femora with an angular protuberance below near 



the outer end. Tropidia Meigen. 



Face tuberculate or arched, not carinate 60 



(iO. Abdomen much narrowed at the base (Central and Soutii America). 



Ceriogaster Williston. 

 Abdomen not narrowed at the base 61 



61. Antennae elongate (Mexico and Europe). Platynoch.^etus Wiedemann. 

 Antennaj short 62 



(52. Thorax and scutellum densely pollinose above 1'terallastes Loew. 



Tiiorax and scutellum not densely pollinose above. . . . 63 ^ 



63. Third joint of the antenna) broad ; tliorax not vittate. . . T5T-^ 

 Third joint of the antennai oval; thorax usually vittate. . . 64 



64. Ocelli remote from eacli other. . . . Asemosyrphus Bigot. 

 Ocelli not remote from each other. . . Helophilus Meigen. 



65. Tiiickly pilose species. Mallota Meigen. 



'J'liinly pilose. .......••■ ^'^ 



