388 ERNEST A. BACK. 



sixth abdominal segments are never red, the bloom covering these 

 segments is never silvery, and the hind tibiae and tarsi are destitute 

 of silvery bloom and pubescence." 



Type. — U. S. N. M., Cat. No. 928. Type series consists of 

 nine males and eight females. 



Habitat. — Los Angeles and San Bernardino Counties, Cal. 

 (April). 



Nicocles dives. 



Pygostolus dives Loew, Cent., VII, 29, 1866. 



% 9 • — Length 8.4-13 mm. — Translation. — Black; last two segments 

 of abdomen of male silvery- white pruinose; wings beautifully varie- 

 gated with black, third basal cell hyaline; third antennal segment a 

 trifle more than twice as long as the style. Fifth abdominal segment 

 of the male about four times as wide as it is long. 



% ■ — Black; head of uniform color; lower margins of the face whitish 

 pruinose; mystax thin, white, the bristles on the oral margin stout, 

 reddish-brown. Antennas black; terminal style almost equal to half 

 the length of the third segment. Thoracic dorsum black, oqaque, 

 with obsolete stripes. Abdomen metallic black, polished, the spots 

 on the lateral margin very small, whitish pruinose; the fifth and sixth 

 segments wholly silvery- white pruinose. Legs brown or reddish-brown, 

 femora largely black. Wings varied with black, the basal third ex- 

 cepting the extreme base and the anal cell, hyaline. 



9 . — Thoracic dorsum brownish-black pruinose, the (indistinct) 

 median line abbreviated (posteriorly and divided by a line of light 

 bloom), the lateral margins broadly grayish, and the scutellum grayish. 

 Lateral spots of the abdomen larger than in the male, the last segment 

 not pruinose. Wings hyaline with the transverse veins bordered with 

 black, so that the posterior median fascia is more dilutely marked, 

 the broad border of the apex,, and the four spots between are black. 

 In other respects the female agrees with the male. 



Type.—U. C. Z. 



Habitat. — The Geysers, Cal. (Osten Sacken, May 5-7) ; Seat- 

 tle, Wash. (June 4). 



The female wing is black, as follows: — Extreme base, mid- 

 dle of costa and becoming less so in a band extending across 

 to the posterior margin, the tip of wing broadly, and four 

 spots, one on the anterior, and two on the posterior cross- 

 veins, and one at the furcation of the third longitudinal cell. 

 These spots show up well in the hyaline space between the 

 median and apical black bands. The anal cell of the male 

 wing is blackish, and the bristles of the body are reddish- 

 brown. 



