188 NORTH AMERICAN DIPTERA 



KEY TO GENERA 



1. Body largely clothed with scales (4, 5) Chromolepida Cole 



Body with tomentum but never with irridescent scales 2 



2. Third antennal segment appearing annulated; labrum narrow (Mexico). 



Ozodiceromyia Bigot 

 Third antennal segment not annulated, usually with a terminal style 

 or short spine 3 



3. First antennal segment longer than the head and bristled (Mexico; 



cf. Metaphragma Coq.) Euphycus Krober 



First antennal segment rarely as long as the head 4 



4. Five posterior cells 5 



Four posterior cells (Bombyliidse) Caenotus Cole 



5. Parafacials bare 8 



Parafacials with pile 6 



6. Basal antenna! segment long and greatly swollen, much larger than 



the second and third combined (1, 7) *Tabuda Walker 



Basal antennal segment not unusually large, never greatly swollen. . 7 



7. Third and fourth veins connected by a crossvein beyond the furcation 



of the third vein (6) Metaphragma Coquilletc 



Wings without such crossvein (8) Thereva Zetterstedt 



8. Third antennal segment not more than twice as long as the first. ... 9 

 Third antennal segment at least two and a half times as long as the 



first (Southern) (13, 14) Henicomyia Coquillett 



9. Basal antennal segment large and shining (15, 16, 17). .Nebritis Coquillett 

 Basal antennal segment pollinose 10 



10. Basal antennal .segment swollen and hairy (1) 11 



Basal antennal segment not strongly swollen 12 



11. Males dichoptic; lower front pilose (1, 7) *Tabuda Walker 



Males holoptic or nearly so; lower front bare of pile. .Dialineura Kondani 



12. Intercallary and fifth veins reaching the wing margin 13 



Intercallary and fifth veins not reaching the wing margin (10, 11, 12). 



Pherocera Cole 



13. Antennal style projecting from under the tip or from the apex of the 



third segment 14 



Style arising from a hollow near the apex of the third segment (9). 



Epomyia Cole 



14. Antennal style projecting from under the tip of the third segment. 



Furcifera Krober 

 Antennal style apical (2, 3) Psilocephala Zetterstedt 



* Tabuda fulvipcs Walker, 1852, is a synonym of Thereva nervosa Walker, 1848. The 

 latter becomes the genotype. 



