34 NORTH AMERICAN DIPTERA. 



5. Second submarginal cell longer than the first: ERIOPTERA Meigen. 

 First submarginal cell longer than the second. MOLOPHILUS Curtis. 



6. First submarginal cell short, not more than half the length of the 



second. . . . . . . . . . . . 7 



First submarginal cell more than half the length of the second. 10 



7. Marginal cross- vein present. -. . .. 8 



Marginal cross-vein absent. . . .- GONOMYIA Osten Sacken. 



8. Second submarginal cell in contact with the discal cell, the anterior 



cross- vein obsolete 9 



Anterior cross-vein present, the first posterior cell intervening between 

 the submarginal and the discal cells. . EMPEDA Osten Sacken. 



9. Anal cell closed; no empodia (Asia, Africa and West Indies). 



MONGOMA Westwood. 

 Anal cell open; empodia present (Central and South America). 



PARATKOPESA Schiner. 



10. Seventh longitudinal vein conspicuously bisinuate. SYMPLECTA Meigen. 

 Seventh longitudinal vein straight. -. 11 



11. Length of the auxiliary vein beyond the cross-vein at least twice that 



of the posterior cross-vein. . . TRIMICRA Osten Sacken. 



The cross-vein situated near the end of the auxiliary vein. 



GNOPHOMYIA Osten Sacken. 



LIMNOPHILINI. 



1. Discal cell open ; antenna? apparently 28-jointed in the $ . 



POLYMERA Wiedemann. 

 Discal cell closed .2 



2. Marginal cross-vein wanting. . . PHYLLOLABIS Osten Sacken. 

 Marginal cross-vein present 3 



3. Wings pubescent ULOMORPHA Osten Sacken. 



Wings bare 4 



4. Seventh vein very short, abruptly incurved toward the anal angle. 



TRICIIOCERA Meigen. 

 Seventh vein not unusual . . 6 



5. A supernumerary cross-vein between the auxiliary vein and the costa. 



EPIPHRAGMA Osten Sacken. 

 No such supernumerary cross-vein. . . LIMNOPHILA Macquart. 



