AEDE8 CTJRRIEI 637 



largely white-scaled along outer and inner side, last joint white ; fore tarsi with 

 narrow basal and apical ring on first joint and basal ring on second ; mid tarsi 

 with narrow rings at bases and apices of first and second joints, and basally on 

 third. Claw formula, 1.1-1.1-1.1. 



Length : Body about 5 mm. ; wing 4.7 mm. 



Male. — Palpi exceeding the proboscis by nearly the length of the last joint, 

 which is somewhat swollen ; vestiture blackish with white scales intermixed, the 

 black scales predominating at ends of joints and middle of long joint; end of 

 long joint and the last two joints densely clothed with long blackish-brown and 

 golden-brown hairs. Antennae plumose, the last two joints long pilose, the rest 

 short, blackish at insertions of hair-whorls ; hairs long, brown and black. Color- 

 ation similar to the female. Wings narrower than in the female, the stems of the 

 fork-cells a little longer; vestiture less abundant. Abdomen long, depressed, 

 with dense, long, whitish lateral ciliation. Claw formula, 3.1-1.1-1.1. 



Length : Body about 6 mm. ; wing 4 mm. 



Genitalia (plate 38, fig. 189) : Side-pieces more than twice as long as wide, 

 apical lobe well developed, rounded uniformly down to base; basal lobe quadrate, 

 protuberant, clothed with short coarse setae from tubercular bases, from its 

 lower angle a stout, thick spine and a shorter one. Clasp-filament slender, 

 long, uniform, tips serrate outwardly and bearing several short setae, a long 

 slender articulated terminal spine. Harpes rather narrow, concave, slightly 

 curved, margins revolute, inner one thickened, curved over at tip in a short 

 point. Harpagones slender, columnar, uniform, with an articulated filament 

 at apex which is ligulate, a little expanded beyond middle and tapered to a 

 point at tip, shaft with a few setoe. Unci approximate with revolute margins, 

 forming a short stout cone. Basal appendages narrow with stout short spines 

 at tip. 



Larva, Stage IV (plate 181, fig. 417). — Head transverse, rounded, widest 

 through eyes ; antennae moderate, uniform, spinose, a small tuft near middle ; 

 both pairs of dorsal head-hairs multiple, the tuft next the antenna multiple. 

 Lateral comb of eighth segment of about twenty-five scales in an irregular patch, 

 each scale fringed on the sides and with a longer central spine. Air-tube about 

 three times as long as wide, slightly tapering outwardly ; pecten of fine imiform 

 teeth running nearly to middle, followed at a slight interval by a single small 

 tuft of several hairs. Anal segment longer than wide, with a dorsal plate reach- 

 ing well down the sides and enlarged before, bearing a single hair at its posterior 

 angles; dorsal tuft a long hair and tuft on each side; ventral brush well de- 

 veloped, with small tufts preceding the barred area. Anal gills rather small, 

 tapered, the two pairs nearly equal. 



Egg. — Slenderly fusiform, uniform, the micropylar end less strongly taper- 

 ing than the other and with an annular cushion ; color dull black, the surface 

 covered with closely crowded, small flattened granulations. 



The eggs are deposited singly on the ground where the water will collect from 

 melting snow or rains, and remain unhatched until the following season. The 

 larvae live in temporary pools. In the north there is but a single annual genera- 

 tion in the snow-water of early spring. Southward the appearance of the larvae 

 is governed by the formation of pools by heavy rains and consequently occurs at 

 irregular intervals. Irrigation operations may also produce conditions under 

 which development takes place. The species inhabits the open arid country, its 

 stronghold being the Montana region, although its range extends over the 

 prairies eastward to Illinois and westward nearly to the Pacific Ocean. In 

 Saskatchewan Mr. Knab found larvae in the early spring in a small swamp, in 

 several ditches along a railroad, and in pools of alkaline water that left a white 



