BeeSpotter

Bombus affinis

Bombus affinis

Bombus affinis (the rusty-patched bumble bee)

Bombus affinis. DeWitt County, Illinois, 19 July.

Status in Illinois

Rare; apparently in decline.

Technical description (from Medler and Carney 1963)

Queen: Face black, with a few yellow hairs intermixed between and above the bases of the antennae; vertex with yellow and black hairs intermixed. Dorsum of thorax entirely covered with yellow hairs, except for a noticeable bare spot on the disc margined by a few scattered black hairs; pleura covered with yellow hairs to bases of the legs; scutellum entirely yellow. Abdomen with tergites 1 and 2 yellow, the posterior margin of yellow being shallowly notched at the middle; tergites 3, 4, 5, and 6 black. Ventral aspect of the abdomen and legs black, the apices of the tibiae and the tarsi largely rust-colored. Remarkably constant in coloration.
Worker: With markings similar to those of the queen, except that the dorsum of the thorax usually has a dark-colored interalar band of intermixed yellow and black hairs. Abdominal tergites 1 and 2 with a distinct brown-ferruginous appearance except where margined with yellow hairs at the sides and posterior margin of the segment.. May vary in the admixtures of yellow and black hairs on the thorax, and the brown-ferruginous hairs on the abdominal tergites.
Male: Face black; vertex with yellow hairs predominant. Interalar band of the thoracic dorsum distinctly black, but with some yellow hairs intermixed. Abdominal tergite 1 largely yellow, tergire 2 with sides and posterior margin yellow, the rest covered with ferruginous hairs. Venter of abdomen and legs largely black. May vary in the admixtures of yellow and black hairs on the thorax, and the brown-ferruginous hairs on the abdominal tergites.

Diagnosis

Queens of B. affinis can be confused with those of B. vagans, but B. vagans has long, shaggy hair and is much smaller than B. affinis.

Habits

This species commonly nests in urban areas, usually underground. Colonies often contain 200 or more workers. Medler and Carney (1963) noted that this species is of comparatively gentle disposition.

Flight periods

Queens appear early in spring, as early as April 21 in Wisconsin (Medler and Carney 1963); colonies are relatively long-lived, lasting until late summer.

Main flower preferences

Queens prefer willow, plum, and apple; workers, sweet clover and mnt; males, horsemint, goldenrod, sweet clover, and aster.

Return to Bombus