Montana Field Guide

For definitions and diagrams of bumble bee morphology please see the Montana State Entomology Collection's Bumble Bee Morphology page. A long-tongued medium-sized species: queens 19-21 mm in length, workers 11-19 mm. Hair moderately long, head long with cheek much longer than wide; mid leg basitarsus with back far corner just acute but rounded, hind leg femur out surface flat and hairless (except for fringe) forming a pollen basket; hair on head black (often with yellow tufts at base of antennae), top pf head yellow mixed with black hairs; side of thorax yellow at least in upper half; T1-2 yellow, T3 usually with traces of yellow near edges at sides, banding on T3-4 clearly defined. Males 13-17 mm in length; eyes similar in size and shape to eyes of any female bumble bee; antennae long, flagellum 4X the length of scape; hair color pattern similar to queens and workers but the black band between the wings extensively intermixed with yellow hairs; S2-6 almost entirely bright yellow (Williams et al. 2014).

Across the range, queens reported April to September, workers and males May to September (Williams et al. 2014). In Toulumne County, California, queens reported May to August, workers June to September, males July to September (Koch et al. 2012); elsewhere in California, queens early July to early August, workers late July to early September, males late July to late August (Thorp et al. 1983).

Please see the Montana State Entomology Collection's Key to Female Bumble Bees in Montana. Females told from other Montana Bombus by a combination of the hind leg outer surface concave and hairless (except fringe), pollen basket present; cheek much longer than wide; face predominantly with black hair; T1-2 with yellow hair, T4-5 with orange or pale orange hairs.

Mostly above treeline at high elevations in alpine tundra, but also in high subalpine forest meadows; also occupies open boreal areas and Arctic tundra (Macior 1974, Hobbs 1967, Williams et al. 2014).

Feeds on a variety of flowers, including Aster, Castilleja, Chionophila, Chrysothamnus, Delphinium, Epilobium, Erysimum, Gentiana, Geranium, Lupinus, Mertensia, Oxytropis, Pedicularis, Penstemon, Phacelia, Phlox, Polemonium, Polygonum, Primula, Sedum, Senecio, Solidago, Symphyotrichum and Trifolium (Macior 1974, Schmitt 1980, Bauer 1983, Shaw and Taylor 1986, Pyke et al. 2012, Koch et al. 2012, Miller-Struttmann and Galen 2014, Williams et al. 2014, Ogilvie and Thomson 2015).

Nests built mostly underground. Nests were established in two above-ground hives and 12 below-ground hives in alpine tundra of southern Alberta; nest building began during mid-June to mid-July. All eggs of first broods deposited in a single cell, average number of eggs was 11 (range 7-21), the number of larvae was 14 (12-15). All members of first broods are workers, males and queens produced in succeeding broods (Hobbs 1964). In Colorado, 27 queens and two nests reported at 3600-4090 m elevation (Macior 1974). Males patrol circuits in search of queens. Parasitism by cuckoo bumble bees not reported in North America, but parasitized by B. hyperboreus in Europe (Williams et al. 2014).