Male. Large, yellowish pilose species, in shape globose. Antennae reddish black, the first joint about as long as the following two together; second joint not one-third as long as the third. Face dark metallic green, shining, thickly covered with golden yellow pile. Front black, with similar pile, narrowed in the middle. Eyes bare. Thorax and scutellum deep metallic green, with long, thick, golden pile; scutellum gently emarginate, the small obtuse tubercles approximate. Abdomen short and broad, black, moderately shining; first two segments and the hypopygium somewhat green; pile at base yellow, elsewhere short, black. Legs black, with black pile; front tibiae and their metatarsi, on the inner side, with short golden pile; hind metatarsi incrassate and longer than the three following joints taken together. Wings uniformly subinfuscate; veins at the outer part of the first posterior and discal cells sinuous and rounded.
Length 12 millimeters. One specimen.
Chrysotoxum derivatum Walker.
Eight specimens from Colorado, which vary not a little from each other and from Williston’s description. They seem to belong here, however, better than elsewhere. In one specimen, the second joint of the antennae is shorter than the first, and only one-fourth the length of the third. In five examples the second abdominal cross-band is not interrupted; in the others it is distinctly parted. In two, the third band does not reach the yellow of the broad hind margin; in two others it barely touches it; in five, the two bands broadly coalesce. The yellow of the fifth segment, in four specimens, incloses a black, inverted V; in two others an inverted Y.
Paragus bicolor Fabr.
Three specimens, Colorado. These may be located under Schiner’s variety taeniatus.
Melanostoma stegnum Say.
- Syrphus stegnus Say, Journ. Acad. Phil. vi, p. 163.
- Melanostoma tigrina Osten Sacken, Western Diptera, p. 323.
- Melanostoma stegnum Williston, Biol. Centr.-Amer. Diptera, iii, p. 10.
Eleven specimens, Colorado, which answer well to the descriptions. The metallic band of the fourth abdominal segment is sometimes interrupted, and there is usually a triangular opaque black spot near the anterior border of the fifth segment. “The female, hitherto unknown, has the front broad above, pollinose, except on the upper part, and with black pile; the thorax more shining metallic blue; the tibiae yellow, and on the third and fourth abdominal segments there is a narrow shining stripe, bisecting the black, as in the fourth segment of the male. The male has some long black hairs on the outer side of the front and middle tibiae, which are inconspicuous in the female. It is evident, from the lighter color of the tibiae, that Say’s specimens were females.” Williston, l. c.