162 DIPTERA OF NORTH AMERICA. 



4. O. rapax Loew. % . — Pedes nigri, tibiis intermedin subdilatatis, 

 tarsorum intermediorum basi rufa, metatarso postico valde incrassato. 



Legs black, middle tibiae a little enlarged, middle tarsi red at the base, 

 first joint of the hind tarsi much swollen. Long. corp. 0.16. Long. al. 

 0.17. 



Very similar to Oclith. tuberculata in the form of the legs, only 

 the middle tibia? are of a less equal breadth, but become sensibly 

 broader towards their end. It is also very easily distinguished 

 from Ochth. tuberculata by its broader and shorter face showing 

 only an exceedingly flat elevation in the middle. Legs entirely 

 black, only at the base of the first joint of the middle tarsi there 

 is a slight red tinge; the first joint of the hindmost tarsi is still a 

 little shorter and thicker than in Ochth. mantis. The wings have 

 rather a more distinct blackish-gray clouding than in the other 

 species. It differs from Ochth. mantis by its shorter face, the flat- 

 ter elevation in the middle of it, and the much shorter and thicker 

 basal joint of its posterior tarsi. 



Hah. Carolina. (Zimmermann.) 



Gen. II. BRACHYDECTERA Loew. 



Eyes naked, proportionately rather large. Front exceedingly 

 broad. Second joint of the antenna? not unguiculated, as large 

 as the third, the latter rounded ; antennal bristle with unusually 

 • long rays. Upper part of the face deeply impressed on both sides, 

 and with a keel, resembling a nose, in the middle; the lower part 

 of it is very prominent. The anterior end of the oral margin very 

 much ascending and allowing the convex clypeus to appear. Be- 

 sides, the whole face is quite bare, with the cheeks descending 

 but very little beneath the eyes. Legs quite bare, rather slender 

 and long; anterior tarsi elongated and exceedingly slender; claws 

 small and delicate, pulvilli rather indistinct. Costal vein of the 

 wing reaching only to the tip of the third longitudinal vein; second 

 longitudinal vein exceedingly short and curved towards the costa 

 like an arch, so that the third segment of the costa is several times 

 longer than the second; the small transverse vein is unusually dis- 

 tant from the base of the wing; the posterior transverse vein is at 

 a little distance from the border of the wing and has a nearly per- 

 pendicular position ; the last segment of the fourth longitudinal 

 vein is much attenuated. 



