HYDROPHORUS. 211 



tudinal vein there is a larger rounded blackish-gray spot, which is 



less sharply defined on the side turned towards the tip of the wing. 



Hah. Fort Resolution, Hudson's Bay Territory. (Keunicott.) 



Gen. XXXVII. HYDROPHORUS. 



Characters. The first joint of the antennae short, bare ; the 

 second very short j the third rounded, more or less distinctly 

 notched under its tip ; arista dorsal, two-jointed, apparently bare. 

 Front a little excavated on the vertex, narrower anteriorly. Eyes 

 large, higher than broad, encased below in the cheeks, which in 

 their structure resemble those of Ortkochile, and are broader than 

 in the other genera. The face reaches somewhat below the lower 

 comer of the eyes ; it is scarcely narrower in the male than in the 

 female, its two upper thirds are usually a little concave ; the lowest 

 third is separated from the upper one by two knotlike elevations 

 Rear the eyes, is convex and ends in a sharp rounded edge. Pro- 

 boscis of moderate thickness ; palpi incumbent, in both sexes 

 rather small. Upper side of the thorax only with moderately 

 long hairs upon its middle. Scutellum rather flat, though some- 

 what elevated along its middle line, in all species known to me 

 with four bristles. Abdomen broad and rather flat, very short, 

 without bristles ; it has five segments in both sexes. The hypopy- 

 gium of the male is small and imbedded ; at its lower end there 

 are two small, dark-colored lamella?, obliquely turned down, and 

 so closely approximated that they seem to form but one clumsy 

 dentiform protuberance ; usually no other appendages are seen 

 besides these. Feet generally bare ; middle and hind feet much 

 longer and more slender than the fore feet ; fore femora gradually 

 rather thickened towards the root ; on their under side, either in 

 both sexes or at least in the male, with short, thornlike bristles ; 

 sometimes they are beset with a few longer and thornlike bristles j 

 fore tibiae on the under side densely beset with very short thorn- 

 like bristles ; middle tibia? never beset with longer hairs, even in 

 the male ; tarsi plain, their joints very much decreasing in length ; 

 the empodium very distinct. Wings long and narrow ; the pos- 

 terior transverse vein close to the margin of the wing ; the third 

 and fourth longitudinal veins usually somewhat converging towards 

 their ends ; in some species they are parallel ; the sixth longitudi- 

 nal vein usually apparent as far as the middle of its course. 



