Abundant.

Queen: Face with a mixture of black and yellow hairs; vertex largely yellow, a few black hairs intermixed. Disc of thorax with a narrow linear bare space; interalar region with a few black hairs, giving this area a darkened appearance, remainder of thoracic dorsum and pleura to the bases of the legs covered with yellow hairs. Abdominal tergite 1 yellow, the yellow hairs slightly concave at the middle posterior margin; remainder of tergites black. Abdominal venter black, legs largely black with a sprinkling of yellow hairs on the trochanters and bases of the femora.
Worker: Marked mostly like the queen, except may have fewer yellow hairs on the face.
Male: Face largely bearing yellow-white hairs; vertex with a triangular patch of yellow hairs, a few black hairs may be intermixed. Thorax and abdomen marked as in the females, the venter with considerable yellow hairs. VARIATION: There is remarkably little variation in the species.

This species can be differentiated from the superficially-similar B. griseocollis and B. bimaculatus by the absence of yellow on the 2nd tergite, and by the distinct notch in the yellow on the apical margin of the 1st tergite.

Nesting occurs underground in this species. Colonies are very large, with up to 450 workers. According to Medler and Carney (1963), the species has a "vicious" temperament. It is parasitized by Bombus (Psithyrus) citrinus.

Queens: . Workers: . Males: .

Queen: willow, red clover; workers: red clover; males: goldenrod, asters.