298 ERNEST A. BACK 



hairs on its edge; a semi-circular impressed line parallel to this edge 

 is very distinct. Abdominal segments 2-6 at the base each with a 

 pair of semi-circular brown spots, gradually diminishing in size on 

 each subsequent segment; a vestige of such spots is also visible on the 

 seventh segment. Hypopygium of the male black, beset with whitish 

 pile and with an appressed tuft of yellow hairs above the forceps. In 

 the female, the eighth segment is black, polished. Legs yellowish- 

 gray, with short appressed whitish pile and yellowish- white bristles. 

 Wings with a slight brownish tinge; the small cross- vein before the 

 middle of the discal cell; second posterior cell sometimes very narrow, 

 in some specimens even petiolate; the fourth posterior in some spec- 

 imens, coarctate toward the end, even closed ; these characters are 

 very inconsistent." 



Type. — M. C. Z. Four males and four females; two pairs 

 of which are in coitu. 



Habitat.— San Francisco, Cal., on the sands about Lone 

 Mountain, April 6, and again June 29. (Osten Sacken). 



This species and opaculus are similar in size and in spots of 

 the abdomen, but arenicola possesses more pile and bristles 

 than opaculus, and they are wholly pale, while the bristles of 

 opaculus are chiefly black. 



Lasiopogoii bivittatus. 



Lasiopogon bivittatus Loew, Cent., VII, 57, 1866. 



Lasiopogon bivittatus Loew, Berl. Ent. Zeitsch., XVIII, 370, 



1874 (note). 

 Daulopogon bivittatus Osten Sacken, West. Dipt., 310, 1877. 



(^ 9- — Length 8 min. — Translation. Black; brownish-gray pruin- 

 ose, the two narrow thoracic stripes black, separated by a broad inter- 

 val, the median transverse vein of the vein projecting beyond the 

 middle of the discal cell. Length of body 4 lin; of wing 3-7-12 lin. 



Wholly black; mystax, pile of palpi, antennae, front and vertex, 

 black; beard whitish. Thoracic dorsum covered with brownish bloom, 

 black pilose, and marked with two narrow black stripes, separated by 

 a broad interval, diverging anteriorly and subabbreviated; scutellum 

 of the same color, black pilose, with the same depressed line as Osten 

 Sacken mentions in his description of arenicola; pleurae more grayish 

 prviinose, with a little white pile; pile in front of the wings and the 

 trichostical bristles black. Abdomen black, polished; the first segment 

 almost wholly, the posterior margin and sides of the remaining seg- 

 ments, broadly grayish-white pruinose. Pile of the abdomen rather 

 longer, sordid whitish; the posterior margin of the first segment to- 

 ward the sides with a few black bristles. Venter grayish pruinose 

 with whitish pile. Hypopygium large, black, polished, with black 



