North Amehican Diptera. 63 



iipproxiniated to the first longitudinal voin. Head prolonged in two 

 lateral apoplivses bearing the eyes ; front bristly only on the upper 

 part ; border of the mouth with no vibrissa3. Anterior femora in- 

 crassated. 



Piopn I L 11)^. 

 The auxiliary vein, on its whole length, is coalescent with the 

 first longitudinal vein ; witli this exeeption the neuration of the 

 wings is complete. Front with some small bristles above only ; bor- 

 der of the mouth with a vibrissa on each side; clypeus rudimentary ; 

 legs rather stout, almost of the structure of those of the Sciomy- 

 zidie; middle tibiiu with spurs; all the tibiae without erect bristle 

 on the exterior side before the tip. 



E P II Y D R I D JE. 



Face convex, with no distinct furrows for the reception of the 

 antenna' and without vibrissje, though frequently beset with hairs or 

 bristles ; cl^'peus very much developed ; opening of the mouth large ; 

 proboscis incrassated with a swollen chin. Neuration of the wings 

 incomplete; the auxiliary vein distinct only at its base; the fore- 

 most of the two small basal cells reunited with the discal cell. Mid- 

 dle tibiaj with spurs. 



G E o M y z I D ^. 

 Front with stout bristles above ; border of the mouth with vibris- 

 sae. Clyi)eus rudimentar}'. Middle tibia3 with spurs ; all the tibise 

 with a small erect hair on the exterior side before the tip. Wings 

 with bristles on the costa ; first longitudinal vein exceedingly abbre- 

 viated, and the auxiliary vein so approximated to it that it is dis- 

 tinctly separated from it only towards the base ; the two posterior 

 basal cells very small. 



1) R O S O P H I L I D iE. 



Front with bristles above ; face with distinct sub-antennal furrows ; 

 at the border of the mouth there is a feeble, frequently rather indis- 

 tinct small vibrissa. Middle tibiae with very feeble spurs ; on the 

 exterior side of the tibiaj there is either a very small or no erect 

 bristle before the tip. Wings without bristles on the costa; the first 

 longitudinal vein is exceedingly abbreviated ; of the auxiliary vein 

 there is only a rudiment; the discal cell is usually, but not in all 

 genera, united with the foremost of the two small basal cells. 

 Claws and pulvilli very small. 



08CINID.E. 



Front without bristles, the crown having only a few short ones ; 

 border of the mouth without vil)rissa3, which, however, are repre- 

 sented sometimes by a small hair on each side. Middle tibiic with 

 small spurs ; all the tibiae without erect bristle on the exterior side 

 before the tip. Costa of the wings without bristles. The auxiliary 

 vein is completely wanting ; the anterior of the two small basal cells 

 is united with the discal cell, the posterior one is totally wanting. 



