Montana Field Guide

For definitions and diagrams of bumble bee morphology please see the Montana State Entomology Collection's Bumble Bee Morphology page. A short-tongued, medium-sized bumble bee: queens 19-21 mm in length, workers 10-15 mm. Head short, face round, cheek just shorter than wide; mid-leg basitarsus back far corner rounded, outer surface of hind-leg tibia flat and hairless (except fringe) forming pollen basket; hair of head black or with minority of short pale hairs intermixed; hairs of thorax between wings black or predominantly so; T1 black, T2-3 yellow (rarely with black on central front edge of T2), T4 black, T5 black or yellow-brown; wings slightly brown. Males 13-15 mm in length; eyes similar in size and shape to eyes of any female bumble bee; antennae short, flagellum just over 2X longer than scape; hair color pattern similar to queens and workers (Colla et al. 2011, Koch et al. 2012, Williams et al. 2014).

Across the range, queens reported April to September, workers May to September, males May to October (Williams et al. 2014). In North Dakota, queens reported April to August, workers May to September, males June to October (Koch et al. 2012); in southern Ontario, queens April to September, workers May to September, males May to October, with the earliest record 24 April (Colla and Dumesh 2010).

Please see the Montana State Entomology Collection's Key to Female Bumble Bees in Montana. Females differ from other Montana Bombus by a combination of outer surface of hind-leg tibia concave and hairless (except fringe) forming pollen basket; cheek shorter than wide; hairs between wing bases completely or predominantly black; T1 black, T2-3 yellow.

Near and within deciduous and conifer woodlands, orchards, hay fields, bogs, riparian woodland, boreal forest, treeline conifer forest and tundra patches (Hobbs 1968, Heinrich 1976, Batra 1993a, Colla and Dumesh 2010, Williams et al. 2014).

Feeds on a variety of flowers, including Asclepias, Astragalus, Berberis, Centaurea, Cirsium, Eurybia, Hieracium, Hypericum, Lactuca, Linaria, Medicago, Melilotus, Prunus, Rhus, Ribes, Rosa, Salix, Solanum, Solidago, Sonchus, Symphyotrichum, Taraxacum and Vicia (Plath 1934, Hobbs 1968, Heinrich 1976, Colla and Dumesh 2010, Colla et al. 2011, Koch et al. 2012, Williams et al. 2014). Frequently robs nectar from long-corolla flowers. An important pollinator of alfalfa and certified seed potatos (Hobbs 1968, Batra 1993b), forages to a lesser extent on flowers of commercial highbush blueberry and cranberry (Vaccinium corymbosum and V. macrocarpon) in the eastern United States (MacKenzie and Averill 1995, MacKenzie and Eickwort 1996). Also reported feeding on honeydew produced by nymph and adult balsam twig aphids, Mindarinus abietinus, in balsam fir (Abies balsamea) krummholz at and above treeline in New York (Batra 1993a).

Nests are usually built underground. Of 20 nests discovered by Plath (1934) in New England, one was in an a box of straw in an abandoned greenhouse, the remaining 19 were underground at depths of 15-48 cm, with entrance tunnels of 15-91 cm in length. Two nests built in hives in southern Alberta were subterranean; one of these was initiated 23 May (Hobbs 1968). Colonies may be moderately large, but others no more than about 50 bees. One reported by Plath (1934) consisted of an old queen, more than 50 young queens, and more than 50 workers, as well as many pupae (cocoons). Counts for 32 colonies in Ontario were 0-58 queens (mean = 11), 5-154 workers (mean = 47), and 4-170 males (mean = 67) (Owen et al. 1980). Eggs hatch in about 5 days. Larvae are fed pollen; development times for first brood workers is about 19-21 days, about 21 days for workers of second broods and 20-22 days for workers of third broods. Duration of the larval stage is positively related to adult body size and access to pollen resources (Sutcliffe and Plowright 1990). Life expectancy of a newly-hatched worker is estimated at 13.2 days; as workers grow older, age-specific mortality increases (Rodd et al. 1980). Males patrol circuits in search of queens. Parasitized by the cuckoo bumble bees Bombus bohemicus [=ashtoni], B. insularis, and B. suckleyi (Hobbs 1968, Williams et al. 2014). Host queens do not fight invading parasite queens, but host workers may attack and kill them; larger colonies with a larger worker caste are more successful at preventing invasion by parasitic cuckoo bumble bees (Fisher 1984).

On March 16, 2016, the U.S. Fish and Wildlife Service published a notice in the Federal Register that determined Yellow-banded Bumble Bee (Bombus terricola) may be warranted for listing under the Endangered Species Act. On August 12, 2019, a notice was published that after a thorough review of the best available scientific and commercial information the species is not warranted for listing. Additional information on the species' management can be found on the U.S. Fish and Wildlife Service's Species Account