18 NORTH AMERICAN DIPTERA. 



4. Fifth vein furcate. LASIOSOMA Winnertz. 



Fifth vein not furcate. . . . . ST^EGERIA V. d. Wulp. 



5. Proximal end of the posterior fork (fifth vein) before or opposite the 



anterior cross-vein. . . . NEOEMPHERIA Osten Sacken. 

 Proximal end of the posterior fork beyond the anterior cross-vein. 



POLYLEPTA Winnertz. 



MYCETOPHILIN^E. 



1. Three ocelli present. ... . . . . . 3 

 Only two ocelli, one situated near the margin of each eye. . . 2 



2. The costal vein is continued beyond the tip of the third vein. 



EUDICRANA Loew. 

 The costal vein reaches only to the tip of the third vein. 



MYCETOPHILA Meigen. 



3. The costal vein is continued beyond the tip of the third vein. . 4 

 The costal vein reaches only to the tip of the third vein. . . 11 



4. Fifth longitudinal vein not furcate, the fourth furcate. 



ACNE.VIIA Winnertz. 

 Fifth vein furcate. . , 5 



5. Furcation of the fifth vein before or opposite the furcation of the 



fourth 



Furcation of the fifth vein distinctly more distal than that of the fourth. 



PHTHINIA Winnertz. 



6. Proboscis elongate. GNORISTE Meigen. 



Proboscis not elongate. 7 



7. Auxiliary vein connected with the first longitudinal vein by a cross- 



vein 8 



Auxiliary vein not connected with the first vein by a cross-vein. 9 



8. Ocelli of nearly equal size; the auxiliary vein terminates in the cross- 



vein connecting it with the first longitudinal. SYNTEMNA Winnertz. 



Ocelli of unequal size; the auxiliary continuous beyond the cross-vein, 



terminating in the costa BOLETINA Staeger. 



9. First basal cell very long, reaching bej'ond the middle of the wing; the 



beginning of the upper branch of the forks obsolete. X LEIA Meigen. 



First basal cell of moderate length, not reaching the middle of the 



wing; forks complete. . _ . ' 10 



10. Anterior forked cell acute proximally, the branches but little divergent. 



EI'ICYPTA Winnertz. 

 Anterior forked cell less acute, the branches strongh" divergent. 



DOCOSIA Winnertz. 



11. Fifth longitudinal vein forked. . . . ZYGOMYIA Winnertz. 

 Fifth vein not forked. 12 



