570 



PSYCHE. 



f December 1S93. 



merit and the clubbed genitalia mostly black. 

 Hair of abdomen yellowish-white, except 

 upon the dark parts, where it is more 

 brownish. 



Legs obscure metallic green, the tarsi 

 black; fore coxae very long, cylindrical, with 

 delicate white hairs and a subapical row of 

 black bristles; second joint of fore tarsi one 

 fourth as long as the third, wider than the 

 others, on the underside with a pad of dense 

 short hairs (tubercles?). 



Wings hyaline, a trace of gray across the 

 middle portion, third longitudinal vein curved 

 back to meet the margin behind the apex; 

 beyond this point the margin is a little excised, 

 and close against it lies an almost semi- 

 circular, opaque spot, snow-white in certain 

 lights; this spot is a little nearer the third 

 than the fourth vein; it is enclosed on the 

 proximal side by a distinct, narrow, curved 

 brown spot, beginning behind in the corner 

 of the second posterior cell and continuing 

 around into the marginal, where it gradually 

 fades away along the border of the wing. The 

 fourth longitudinal vein curves strongly back- 

 ward just before reaching the posterior cross- 

 vein, where it makes an angle; there is 

 another backward curve just at the end, in the 

 brown spot. That section of the fifth longi- 

 tudinal vein lying beyond the crossvein is 

 about one sixth the length of the crossvein 

 and almost obsolete. The border of the wing 

 is excised deeply behind the termination of 

 the fourth vein, and immediately behind this 

 is produced into a point, minutely blackened 

 at its apex and bearing a pencil of fine black 

 hairs resembling a small bristle. At the end 

 of the fourth vein is another of these pencils, 

 much larger, and the two are convergent, 

 projecting outward and downward. 



Length 8.5 to 9 mm.; of wing, 7.5 mm. 

 $ . Eyes more widely separated; upper 

 half of the face metallic blue, covered with 

 fine corrugations diverging downward ; lower 

 half green, more whitish dusted. Palpi large, 

 longer than in the male, grayish-yellow 

 dusted, with black hair. Abdomen of mod- 



erate length, borders of the segments more 

 shining green or bronze than black. No dis- 

 tinct spots on the wing, but a very faint cloud 

 at the apex and the same median cloud as in 

 the male. Margin of wing regular in outline ; 

 last section of fifth vein distinct, tarsi plain. 



Length 7 mm. ; of wing, 7 mm. 



Black Hills, S. D. ; elevation over 5000 feet. 

 Numerous specimens of both sexes. 



Closely related to genual is Loew, but 

 readily separated by the yellow knees of 

 the latter, and by the marked differences 

 in the wings of the males. 



I believe this is the largest species of 

 the family Dolichopodidae so far known ; 

 certainly it is the largest North American 

 species. 



The habits of this species deserve 

 notice. Schiner says the genus is found 

 in the moist places about waterfalls. I 

 found hydropliilus in two places near 

 Custer, S. D., last August. Following 

 up a little rill in a meadow east of town, 

 its' origin is found in a deep, round pool, 

 thirty feet across, at the head of a small 

 ravine. This pool is just at the foot of 

 a ledge of rocks some fifteen feet high. 

 From several seams in the rock there is 

 a gentle flow of almost ice-cold water, 

 which covers a considerable area of 

 vertical rock in a thin sheet. Standing 

 in this icy water were my flies ! They 

 would scarcely alight on the neighboring 

 dry warm rock at all, but when disturbed 

 merely moved to another part of the 

 water. The second place was between 

 Custer and Harvey Peak. Here a small 

 stream flows through a narrow gap in a 

 high palisade of rock. A dam twenty 

 feet high in the gap creates a small 

 artificial lake. Below the dam is an 



