32 NORTH AMERICAN DirTERA. ^ dCu^f^^,^ O ^S 



?>. Posterior cross-vein situated before tiie middle of tlie wing; tlirce pos- 

 terior cells present (West Indies). . . ^-5^«*Mi5tiA Willlftloiir- 

 Posterior cross-vein not situated before the middle of the win;/. . 4 



4. A single subniarginal cell present. . . . . . . 5 



Two submarginal cells present. ....... 7 



5. Antennse 14-jointed Limxobiini. 



Antenna? 16-jointed. ......... 6 



6. Tibiae with spurs at the tip ; the first longitudinal vein usually ends in 



the second. ....... Cyi.indrotomini. 



Tibial without spurs ; the first vein ends in the costa. . Antochini. 



7. Tibia? without spurs at the tip Erioptkrixi. 



Tibiae with spurs at the tip. ........ 8 



8. Tlie subcostal cross- vein is beyond the origin of the second longitudi- 



nal vein. ........... 9 



The subcostal cross-vein is before the origin of the second longitudinal 

 vein AiM.\LOPiNi. 



9. Antenna? composed of sixteen joints. . . . Limnophilini. 

 Antenna^ composed of from six to ten joints, often much elongated. 



Anisomkrixi. 



LTMNOBIIXI. 



1. I'roboscis longer than the head and thorax together. 



Gerano:myia Ilaliday. 

 •'^;- Proboscis shorter than the head and thorax together. . . . '1 



2. Antennae pectinate or sub|)ectinate, at least, in the male. 



IvuiPiDiA ^leigen. 

 Antenna^ not pectinate. ......... ^J 



;>. A supernumerary cross-vein between the sixth and seventh veins. 



T^ROCHOBOLA ( >sten Sacken. 

 No cross-vein connecting the sixth and seventh veins. ... 4 



4. Tip of the auxiliary viin usually opi)osite, or before, or only a short 

 distance beyond the origin of the second vein ; marginal cross- 

 vein always at the tip of the first longitudinal vein ; legs slender. 



DiCRANOMViA Stephens. 

 'J'ij) of the auxiliary vein usually far beyond the origin of the second 

 vein; marginal cross-vein sometimes at the tip but often some dis- 

 tance before the tip of the first vein; legs comparatively stout. 



LiMNoiuA Meigen. 



