AEDE8 NIGKOMACULIS 657 



stripe, on posterior half a narrow stripe each, side of antescutellar space, humeral 

 angles broadly deep golden brown sealed, scales about antescutellar space paler. 

 Scutellum trilobate, blackish, clothed with narrow curved pale yellow scales, each 

 lobe with a group of rather fine pale bristles. Postnotum broadly elliptical, 

 prominent, black, nude. Pleurae and coxae black, clothed with elliptical, flat, 

 white scales, the setae small and not abundant, mostly whitish. 



Abdomen subcyliadrical, tapering posteriorly, the last segment slender ; dor- 

 sum clothed with dull black and sordid white scales, the white scales form a 

 median stripe, a band at the base of each segment widening into lateral tri- 

 angular patches, and a narrow apical band ; upon the sides the white scales are 

 nearly continuous, only a few of the black ones reaching through to the apical 

 angles ; first segment with a large patch of flat white scales and with many pale 

 hairs; last segment almost wholly white; venter clothed with yellowish-white 

 scales, a few black ones intermixed. 



Wings rather broad, hyaline ; petiole of second marginal cell slightly shorter 

 than its cell, that of second posterior cell about equal to its cell ; basal crossrvein 

 distant less than its own length from anterior cross- vein ; vestiture of black and 

 white scales, costa white scaled on basal fourth, then black to tip ; the subcostal 

 and first veins have the black and white scales about evenly intermixed, the other 

 veins are almost wholly black scaled, only a few white ones are visible on the 

 base of the fourth vein ; the outstanding scales on outer half of wing long and 

 rather broadly linear ; fringe blackish, unicolorous, appearing mottled black and 

 whitish according to direction of light. Halteres with whitish stems and black- 

 ish knobs. 



Legs moderate ; femora with yellowish- white and black scales evenly inter- 

 mixed, the black ones predominating just before tip, the apex narrowly white ; 

 tibiae with black and white scales, the tips black; hind tarsi black, each joint 

 with a broad basal pure white ring, the first with some white scales intermixed 

 on basal half, forming a broad, diffused whitish mark, last joint black with 

 white scales on basal half ; front tarsi with last three joints unmarked ; mid tarsi 

 with last two unmarked. Claw formula, 1.1-1.1-1.1. 



Length : Body about 4.5 mm. ; wing 4.5 mm. 



Male. — Proboscis slender, straight, unicolorous. Palpi long, somewhat ex- 

 ceeding the proboscis ; tip of long joint and last two joints somewhat thickened 

 and clothed with long blackish hairs ; vestiture of dark-brown scales, the last 

 two joints with narrow white basal rings, the long joint with a white ring below 

 middle. Antennae plumose, the last two joints long and slender, rugose, pilose, 

 black, the others short, whitish, thickened at insertions of hair-whorls; hairs 

 long, dense, brown. Coloration similar to the female. Abdomen elongate, de- 

 pressed, sides with long, abundant, pale ciliation. Wings narrower than in the 

 female, the stems of the fork-cells longer, the vestiture sparse. Claw formula, 

 2.1-2.1-1.1. 



Length: Body about 5.5 mm.; wing 4.5 mm. 



Genitalia (plate 33, fig. 313) : Side-pieces three times as long as wide, 

 slender, uniform, rounded at tips; basal lobe small, rounded, prominent, setose. 

 Clasp-filament slender, uniform, with a long terminal spine. Harpes elliptical, 

 concave, inner margin thickened, tip bent and pointed. Harpagones with a 

 rather short slender straight stem, and slender filament, about as long as stem. 

 TJnci forming a cone, basally placed. 



Life history and habits unknown. 



Arid regions of west-central United States to Mexico. 



Tort Keogh, Montana, September, 1906 (through C. S. Ludlow) ; Cascade, 

 Montana, July 35, 1907 (W. E. Britton) ; Bigtimber, Montana, August 25, 

 1908 (E. A. Cooley) ; Fort McKinley, Wyoming (through C. S. Ludlow) ; 



