64 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



region and a large area above the pleurae and before the wing covered with 

 thick reddish brown dust. Pleurae, sides and venter of abdomen covered 

 with frosty white or gray dust. Abdomen truncated posteriorly; hypopygial 

 appendages black, thick, short and projecting. Coxae concolorous with the 

 lower pleurae; fore and middle pairs with abundant yellow hairs on their fore 

 faces. Legs blackish bronze green; tarsi black; all the pulvilli enlarged, 

 flesh-colored; fore femora and tabiae covered with long yellowish hairs, the 

 former rather slender for a male; inner lower surface of fore femur with only 

 six or seven graduated black spines on the proximal half Denticular spines 

 on the lower (inner) surface of the tibia short and distinct only on the distal 

 half, fading away proximally; tip of the fore tibia without a tooth or projec- 

 tion, but the hairs of the strigil near the tip are long and distinct. Wings 

 gray, in some cases brownish or blackish towards the base along the second 

 and third veins. Venation normal, veins black throughout. There is a con- 

 spicuous round black spot near the middle of the distal segment of the fourth 

 vein and another of about the same size covering the anterior half of the pos- 

 terior cross-vein. Halteres yellow, knob distinctly infuscated. Tegulae 

 brownish, with light yellow cilia. 



Female. Length 3.5 mm.; length of wing 4,5 mm. Coloration like that 

 of the male. Spines on the fore femora shorter and less numerous than 

 those of the male, spines on the fore tibia longer and more numerous, 

 extending the whole length of the inner surface. 



Three males and one female collected in sweepings in 

 the Two-gwo-te-ee Pass, Western Wyoming, September 12, 

 1895. 



This species resembles the European H. bifunctatus 

 Lehm. in having bimaculate wings. The female of the 

 European species is described as la(*king the femoral spines. 

 H. algens may yet prove to be the same as Walker's H. 

 chrysologus or his H. glaher. 



64. Hydrophorus parvus Loeiv. 



Plate IV, Fig. 119. 



A male and female Hydrofhorus taken by me in a marsh 

 near Worcester, Mass., April i, 1891, agree very closely 

 with Loew's description of this species. The abdomen of 

 the male is about as long as the thorax, and truncated 

 behind; the two anterior hypopygial appendages project 

 downwards and backwards. The fore leg of the male is 

 represented in fig. 119. The third and fourth veins are 

 parallel as described by Loew, but their extreme tips diverge 

 in joining the costa. There is a slight swelling at the 



