MALE. Black, densely golden red pilose. Frontal triangle, face and cheeks deep black, shining, covered thickly with black pile, save a median facial stripe. Antennae black, basal third of third joint on the under side red; first joint short; second joint not more than half as long as the first; third joint three times as long as the first and second joints taken together; gradually broadened for a third of its length, and then attenuated; style white. Eyes thickly clothed with golden pile. Thorax and abdomen covered everywhere with long golden red pile. Legs black; tarsal joints below and at their articulations reddish. Wings nearly hyaline, brownish on the anterior basal portion; stigma yellow. Length 11 millimeters. Three specimens, Colorado. The genus may be distinguished from _Pelecocera_, in Williston’s dichotomic table of the genera of North American Syrphidae, by the pilose eyes. =Microdon megalogaster, n. sp.=, Plate vii, f. 1. 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.