AMERICAN DIPTERA. 387 



Habitat. — California (type). 



The wings are less black than in dives. The black areas are 

 not as extensive and not as dense. The female differs from 

 the female of dives in not possessing the pronounced broad 

 whitish pruinose bands along the lateral margins of the dor- 

 sum which are so noticeable in dives. 



Nicocles argentatus. 



Nicocles argentatus Coquillett, Can. Ent., XXV, 119, 1893. 



" ,j\ — Length 8-10 mm. — Black; the tibia? and apex of the sixth, 

 and sometimes of the fifth, abdominal segment, red. Front grayish- 

 brown pruinose; face nearly flat, white pruinose and sparse whitish 

 pilose; mystax on oral margin consisting of a few long yellowish hairs 

 interspersed among about fourteen stout yellow bristles; pile of palpi 

 and of occiput white, bristles of the latter yellow. First segment of 

 antennae slightly longer than the second, the third one and three- 

 fourths times as long as the first two taken together, of nearly equal 

 width, the style nearly half as long as the third segment. Thorax 

 marked with a broad median black stripe not extending on the posterior 

 fourth, and on each side of it is a large brown pruinose spot divided 

 by the suture and bounded in front by a black spot, also a brown spot 

 on the humeri; elsewhere the bloom is grayish- white; the pile very 

 sparse, white; the bristles brown; pleura? brown pruinose in front, 

 grayish- white pruinose behind; the fan-like row of hairs in front of 

 the halteres white. Scutellum brown pruinose, a black spot at the 

 base on each side; bearing two brown bristles. Abdomen smooth, 

 sparse grayish-black pruinose, that at the base and sides of segments 

 2 to 4 gray, the fifth and sixth segments wholly silvery pruinose; 

 second segment longer than wide, others wider than long, the fifth 

 being two and one-half times as wide as long; venter gray pruinose 

 and with median brown pruinose stripe, its pile and that of the legs 

 white, the bristles of the latter white and yellowish; hind tibia? within, 

 and the under side of their tarsi, densely silvery-white pruinose and 

 pubescent. Wings hyaline; an indefinite pale brown spot extends 

 from the tip of the axillary vein to the base of the fifth posterior cell, 

 darkest in the marginal and interrupted in the first submarginal cell; 

 a second brown spot covers the veins at bases of the first, second and 

 third posterior cells; a scarcely apparent brown spot at base of second 

 submarginal cell, and a large one filling apices of the marginal, first 

 and second submarginal, and of the first posterior cell, extending from 

 one-half to three-fourths the distance from the tip to the base of the 

 second submarginal cell, and sometimes connected with the first- 

 mentioned brown spot by a brown streak extending through the 

 middle of the marginal cell; all the posterior cells open, the anal cell 

 closed." 



" j* . — Same as the male, except that the apices of the fifth and 



TRANS. AM. ENT. SOC, XXXV. SEPTEMBER, 1909 



