258 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



segment with a short, appressed tomentum, forming a yelloT\'ish- white 

 cross-band ; the remaining segments, beginning with the posterior mar- 

 gin of the second, are covered with long, semi-erect, black ijile, across 

 which, in the middle of the abdomen, there is a triangular fignre formed 

 by similar pile, but white ; the apex of the white triangle rests on the 

 hind margin of the second segment ; the oblique stripes of white pile, 

 forming the sides of the triangle, run downward toward the venter; the 

 innier side of the triangle is filled, partly with black, partly with white 

 pile, the latter chiefly occupying the end of the abdomen; the venter 

 is clothed anteriorly with white, posteriorly with black pile. Legs red- 

 dish ; tarsi darker; hind tibiae and tarsi reddish-brown. Knob of halteres 

 yellow. Wings grayish-hyaline ; base as far as the basal cross- veins 

 brownish ; costal cell pale yellowish. Length 11-12™^. 



Mah. — Waco, Texas (Belfrage). A single female. The specimen is in 

 Mr. E. Burgess's collection in Boston. 



LORDOTUS. 



LoRDOTUS GiBBUS Loew, Centur., iv, 53. — Dr. Loew described a fe- 

 male from Matamoras. I have a dozen specimens from Denver, Colo. 

 (Uhler, August 18), Cheyenne, Wyo. (myself, August 21), and California 

 (San Francisco and Shasta district, H. Edwards). The color of the 

 antennfe is variable. In all the specimens from California (six females), 

 the two basal joints are red. One of the specimens from Denver has the 

 second joint red toward the tip only, as described by Dr. Loew. In the 

 other specimens from Denver, and also in those which I took near 

 Cheyenne, the antennge are altogether black, although the basal joints 

 are grayish-poUinose. Well preserved specimens show two grayish 

 stripes on the thorax. The brownish-red color at the base of the wings 

 and in the costal cell is often extended to the first basal and submarginal 

 cells. A gray cloud is often visible on the cross- vein at the base of the 

 fourth posterior cell. The costa in all my specimens is reddish, and not 

 black, as described by Dr. Loew. 



I have only a single male, taken near Cheyenne, Wyo. The eyes are 

 closely contiguous on a rather long line, down to very near the bas@ of 

 the antennas. The difference between the upper larger facets and the 

 lower smaller ones is well marked, although the line of division between 

 them is not very sharp (in the female, the facets are uniform); frontal 

 triangle very small, glabrous. On the last abdominal segments, begin- 

 ning with the fifth, many black hairs are mixed with the yellow ones, 

 especially on the sides. The femora, except the last quarter, are black ; 

 the tarsi altogether black. The body is smaller and much more slender 

 than that of the female. 



As one of the specimens from Denver has been communicated to Dr. 

 Loew, there can be no doubt about the specific identity. 



L()RDOTUS(?) PLANUS n. sp. — I place provisionally in this genus a 

 Californian species, of which I have only a single male specimen, and 



