Total length 17-23 mm. A yellow pilose species, with the scutellum and first segment of the abdomen with black hairs and bristles. There is considerable reddish pile mingled with the yellow pile on the abdomen. Related to B. fernaldi Back, from which it may be distinguished by the even distribution of the red hair on the abdomen, not restricted to certain areas as in fernaldi, and the first segment of the abdomen being always black-haired in contrast to the second which is thickly yellow pilose.

Male.--Head black, yellow pilose, except hairs of upper part of occiput, and a few hairs in lower part of mystax, beard, and on palpi which are black. Pronotum with black bristles. Mesonotum thickly dark yellow pilose. A yellow tuft of hairs in front of wings and in front of halteres. Coxae yellow-haired; considerable black on posterior pair. Legs black with black hairs, except the hairs on posterior aspect of front femora, the dorsal aspect of the first and second pair of tibiae, and a few hairs on the dorsal aspect of the basal portion of the hind tibiae, which are yellow. Wings and halteres light brownish. Scutellum and first segment of abdomen with black hairs and bristles. Segments 2-6 above densely yellow pilose with reddish hairs uniformly intermingled. Genitalia black or with some black and some pale hairs and bristles.

Female.--Similar, except black hairs predominate in beard and on coxae. The apex of the abdomen from the 7th segment on is black-haired, with a few yellowish hairs on ovipositor.