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 17-21 mm in length, workers 11-14 mm. Hair medium, head length medium with cheek just longer than wide; mid-leg basitarsus with back far corner rounded, hind-leg tibia outer surface flat and lacking long hair (except fringe), pollen basket present; hair of face black; upperside of head (occiput) yellow especially centrally; upper surface of thorax yellow with a central black dot between wings, sides of thorax entirely yellow; T2 mostly yellow at front, sometimes black along back; T3-4 and S3-5 usually black at the sides unless T3-4 black on upper surface. Male 11-14 mm in length; eyes similar in size and shape to eyes of any female Bombus; antennae medium length, flagellum 3X longer than scape; hair of face yellow with black intermixed at least around base of antennae; upper surface of thorax predominantly yellow; T3 usually black in the middle, T5-6 often yellow at the sides (Colla et al. 2011, Koch et al. 2012, Williams et al. 2014).

Across the range, queens reported April to October, workers May to November, males May to November (Colla et al. 2011, Williams et al. 2014). In eastern Washington, queens reported April to July, workers May to November, males July to November (Koch et al. 2012).

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-leg tibia outer surface concave and hairless (except or fringe), pollen basket present; cheek longer than wide; face predominantly with black hairs; T2 yellow, T3 mostly black, T4-6 black; sides of thorax predominantly yellow.

Forests, wetlands, urban parks and gardens, tall grass prairie, irrigated prairie and woodland riparian, prairie parkland, foothill grassland-forest ecotone (Hobbs 1967, Hines and Hendrix 2005, Grixti et al. 2009, Williams et al. 2014).

Feeds on a wide variety of plants (more than 60 genera), including Anaphalis, Apocynum, Aquilegia, Aralia, Arctium, Asclepias, Astragalus, Berberis, Carduus, Centaurea, Cichorium, Cirsium, Claytonia, Clematis, Cornus, Crataegus, Daucus, Delphinium, Dicentra, Dipsacus, Dodecatheon, Echium, Ellisia, Erythronium, Eupatorium, Eurybia, Fragaria, Geranium, Helianthus, Hesperis, Hydrophyllum, Hypericum, Impatiens, Ipomoea, Lactuca, Ledum, Leonurus, Liatris, Linaria, Lonicera, Lotus, Lupinus, Malus, Medicago, Melilotus, Mentha, Mertensia, Mimulus, Monarda, Nepeta, Nymphaea, Onobrychis, Onopordum, Pedicularis, Penstemon, Phlox, Physostegia, Polemonium, Prunella, Prunus, Rhododendron, Ribes, Rubus, Salix, Satureja, Scrophularia, Scutellaria, Silene, Sisyrinchium, Solanum, Solidago, Sonchus, Spiraea, Stachys, Symphoricarpos, Symphyotrichum, Symphytum, Tamarix, Taraxacum, Teucrium, Tradescantia, Trifolium, Vaccinium, Verbascum, Verbena, Veronica, Vicia, Viola and Zizia (Plath 1934, Macior 1968, Heinrich 1976, MacKenzie and Averill 1995, Mayer et al. 2000, Colla and Dumesh 2010, Colla et al. 2011, Koch et al. 2012, Williams et al. 2014).

Nests built mostly underground, although occasionally on the surface or above ground (Hobbs 1967, Colla et al. 2011, Williams et al. 2014). In southern Alberta, nests established mid to late June; mean number of pupae in first broods is 8-10 (Hobbs 1967). Males patrol circuits in search of queens. Nests sometimes parasitized by the cuckoo bumble bee Bombus citrinus.