174 BULLETIN 116, UNITED STATES NATIONAL MUSEUM. 



Thorax green with coppery reflections on the dorsum, which some- 

 times form a distinct median vitta; dorsum shghtly dulled with an 

 almost invisible gray pollen, more conspicuous along the front; 

 pleurae dulled with a little white pollen. Abdomen green with 

 bronze reflections; the white pollen on its sides extending upon the 

 dorsum. Hypopygium black: its lamellae (fig. 121) of moderate 

 size, oval, whitish, with a black border on apical and upper margins, 

 a little jagged and bristly at apex, fringed above with short black 

 hairs. 



Coxae black with yellow tips; fore coxae with white pollen and little 

 black hairs on their anterior surface. Femora and tibiae yellow. 

 Middle and hind femora each with one preapical bristle, the latter 

 ciliated on lower inner edge for nearly their whole length with black 

 hairs, which appear brown in certain lights, the longest of these hairs 

 scarcely as long as the width of the femora. Posterior tibiae black 

 at tip for nearly one-fourth their length, a little thickened; the 

 glabrous stripe on upper surface distinct, inner surface glabrous on 

 basal half and with a narrow glabrous line just inside of inner row 

 of bristles on apical half. Fore tarsi (fig. 121a) about one and a half 

 times as long as their tibiae, the first three joints yellow, slender, of 

 decreasing length, the first being as long as the two following taken 

 together; last two joints black, compressed, fourth about three- 

 fourths as long as third, not as wide at apex as long, fifth joint much 

 widened, notched at apex, somewhat cordate, the lobes being of 

 nearly equal size; a little longer than third joint and nearly as wide 

 over the two lobes at tip as the length of the third joint. Middle 

 tarsi about one and a third times as long as their tibiae, black from 

 the tip of the first joint, which has a large bristle above near apical 

 fourth. Hind tarsi wholly black, about one and a half times as long 

 as their tibiae. Calypters and halteres yellow, the former with black 

 cilia. 



Wings grayish; costa enlarged at tip of first vein, tapering to its 

 tip; last section of fourth vein considerably bent before its middle, 

 sometimes this bend bears a slight stump-vein; hind margin of wing 

 scarcely indented at tip of fifth vein; anal angle prominent. 



Female. — Face a little wider than in the male and more whitish; 

 hind femora not ciliated; their tibiae not glabrous on inner surface; 

 fore tarsi plain, as long as their tibiae, black from the tip of the first 

 joint; middle tarsi a little longer than their tibiae, bristle on first 

 joint placed at apical third; their tibiae with three bristles below, one 

 pair at apical third and one bristle at basal third. 



Rcdescribed from numerous males and females. Idaho, taken 

 July to October (Aldrich) ; Utah, July; Colorado Springs, Colorado, 

 June 9; Washington, May to July (Melander); Yellowstone Lake, 

 Montana, July 9; Sheridan, Wyoming, June; Hood River, Oregon, 



