Montana Field Guide

For definitions and diagrams of bumble bee morphology please see the Montana State Entomology Collection's Bumble Bee Morphology page. A medium-tongued small species: queens 15-17 mm, workers 10-14 mm. Head length medium with cheek as long as broad; mid-leg basitarsus with back far corner rounded, hind-leg tibia outer surface flat and lacking hair except along fringes, forming a pollen basket; hair of face and underside black with small patches of yellow hair around the antennae bases and on top of head; upper surface of thorax mostly yellow at front, with a black band between the wings sharply defined at anterior edge, posterior part of upper thorax yellow on sides and not always divided along midline by black; T1 yellow, T2-3 usually orange, and if black then sometimes yellow medially; T4-5 predominantly yellow and often with some black in middle. Males 11-14 mm; eye similar in size and shape to eye of any female bumble bee; antennae medium length, flagellum 3X the length of scape; hair color pattern similar to queens and workers (Koch et al. 2012, Williams et al. 2014).

Late emerging relative to most other Bombus because of the high mountain habitats to which it is mostly restricted. Across the range, queens and workers reported May to September, males July to October (Koch et al. 2012, Williams et al. 2014). In California, queens reported early June to early September, workers late June to late September, males early July to early October (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 hind tibia concave and hairless, pollen basket present; scutum mostly yellow in front of wing bases; cheek as long as wide, the face with yellow hairs at least centrally; scutellum with yellow or pale yellow hairs divided by a line or triangle of black hairs; T2-3 orange; T5 with yellow hairs along edges, the hairs long and uneven; coxae mostly with black hairs.

Found in montane meadows, aspen woodlands, along montane stream courses, and alpine tundra (Hobbs 1967, Macior 1974).

Feeds on a variety of plants, including Allium, Arenaria, Besseya, Castilleja, Chionophila, Chrysothamnus, Cirsium, Dodecatheon, Epilobium, Erysimum, Frasera, Gentiana, Grindelia, Haplopappus, Helenium, Helianthella, Lupinus, Melilotus, Mentha, Mertensia, Onosmodium, Oxytropis, Pedicularis, Penstemon, Petasites, Phacelia, Phyllodoce, Polemonium, Polygonum, Primula, Sedum, Senecio, Symphyotrichum, Taraxacum, Trifolium and Wyethia (Beattie et al. 1973, Macior 1974, Schmitt 1980, Thorp et al. 1983, Bauer 1983, Koch et al. 2012, Pyke et al. 2012, Williams et al. 2014, Miller-Struttmann and Galen 2014, Ogilvie and Thomson 2015). Individual queens and workers are more generalist foragers, and plant species use broadens, along an altitudinal productivity gradient, particularly comparing montane and subalpine habitats with the alpine (Miller-Struttmann and Galen 2014).

Nests mostly underground (Williams et al. 2014), although 29% of 73 nests found in Alberta were established above ground in artificial hives (Hobbs 1967). In Colorado, all nests (3) and queens (56) were found in alpine tundra above 3620 m elevation (Macior 1974). Nests are established in mid- to late June above treeline in Alberta; the numbers of eggs, larvae and pupae in first broods are typically 9-10, respectively, with 3-5 eggs laid per cell in second and third broods (Hobbs 1967). Males patrol circuits in search of queens (Williams et al. 2014). Parasitism by cuckoo bumble bees not reported but possible (see comments in Hobbs 1967).