172 DIPTERA OF NORTH AMERICA. [PART IV. 



of the second ; the first is pointed, the latter square ; the great 

 cross-vein is some distance anterior to the discal cell ; all the 

 cross-veins, the origin of the pragfurca, and the tip of the first 

 longitudinal vein are clouded with brownish-gray. 



Common everywhere in the spring and in autumn. I possess 

 specimens from Washington, D. C. ; Mobile, Ala. ; New York ; 

 Canada ; Illinois (Kennicott). The supernumerary cross-vein of 

 the first submarginal cell is wanting in some specimens j the discal 

 cell is sometimes open. 



Gen. XXI. ' GNOPHOMYF4. 



Two submarginal cells ; four posterior cells ; a discal cell ; the second 

 longitudinal vein originates somewhat before the middle of the anterior 

 margin, a considerable distance anterior to the tip of the auxiliary vein ; 

 prsefurca very slightly arcuated at the basis, nearly straight ; subcostal 

 cross-vein at a small or moderate distance (hardly exceeding the length 

 of the great cross-vein) from the tip of the auxiliary vein ; seventh longi- 

 tudinal vein nearly straight. Wings glabrous (except an almost micro- 

 scopic pubescence in the apical cells of G. luctuosa). Antennae 16-jointed. 

 Tibiae without spurs at the tip ; tarsi with distinct empodia. The forceps of 

 the male (Tab. IV, fig. 19, forceps of G. trisiissima when open) consists 

 of two comparatively short basal pieces, and a pair of claw-shaped horny 

 appendages ; a second pair of horny appendages, below the first, is shorter 

 and stouter. 



Body and feet rather stout; the latter of moderate length, 

 their pubescence short ; femora slightly incrassated before the 

 tip. Front broad, very convex ; eyes glabrous, almost contigu- 

 ous on the under side ; rostrum short ; palpi of moderate length ; 

 last joint somewhat elongated. Antennae 16-jointed ; when bent 

 backwards they reach a little beyond the root of the wings in 

 both sexes ; joints of the flagellum elongated, subcylindrical in 

 G. tristissima ; short, subglobular in G. luctuosa; verticils much 

 longer in the former than in the latter. Collare somewhat 

 elongated in G. tristissima; short and stout in G. luctuosa. 

 Suture of the thorax distinct. The wings are rather broad in G. 

 luctuosa ; narrower in G. tristissima (Tab. II, fig. 5, wing of G. 

 tristissima). The marginal cross-vein is close by the inner end 

 of the first submarginal cell ; the great cross-vein is more or less 

 posterior to the inner end of the discal cell ; the latter elongated ; 

 the fifth, sixth, and seventh longitudinal veins are nearly straight 

 (more details about the venation and the differences between that 



