Two-spotted Bumble Bee - Bombus bimaculatus
For definitions and diagrams of bumble bee morphology please see the Montana State Entomology Collection's Bumble Bee Morphology page
. A medium-tongued, medium-sized bumble bee: queens 18-22 mm in length, workers 10-16 mm. Head length medium, cheek just longer than wide; mid leg basitarsus with back far corner rounded, outer surface of hind leg tibia flat and hairless (except fringe) forming pollen basket; hair of face black or with only a few yellow hairs intermixed; upper surface of thorax with dense black spot between wings (often with yellow hairs intermixed), occasionally forming band, sides of thorax yellow; T1 yellow; T2 extensively black at sides of front and always with patch of yellow at mid line, the back edge forming a characteristic "W" shape; T3-5 black. Males 12-15 mm in length; eyes similar in size and shape eyes of any female bumble bee; antennae medium length, flagellum 3X longer than scape; hair color pattern similar to queens and workers, but yellow patch intermixed with black below antennae, T4-5 at sides with at least some yellow (Colla et al. 2011, Williams et al. 2014).
Across the range, queens reported February to October, workers March to October, males April to October (Colla et al. 2011, Williams et al. 2014). Earliest queen reported in Boston area by Plath (1934) was 7 April. In southern Ontario, queens reported April to October, workers May to August, males June to October; earliest record 13 April (Colla and Dumesh 2010).
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 outer surface of hind leg tibia concave and hairless (except fringe) forming pollen basket; hair on face predominantly black; cheek longer than wide; T2 with yellow hairs medially and black along sides (the yellow often in shape of "W"), T3 mostly black hairs, T4-6 with black hairs.
Resident Year Round
Recorded Montana Distribution
Click the map for additional distribution information.
East of the Great Plains from extreme southern Canada south to the Gulf Coast (Colla et al. 2011, Williams et al. 2014). Appears to be stable or increasing in abundance throughout its range (Colla and Packer 2008, Grixti et al. 2009, Cameron et al. 2011, Colla et al. 2012, Tripodi and Szalanski 2015), and possibly invading some natural areas previously occupied by Bombus affinus (Molumby and Przybylowicz 2015).
In and near oak woodlands, mixed deciduous forest, tallgrass prairie, dunes, farmland, fields and meadows, railroad margins, urban parks and gardens (Snider and Husband 1966, Macior 1968, Hines and Hendrix 2005, Colla and Dumesh 2010, Molumby and Przybylowicz 2012, Williams et al. 2014).
Feeds on a variety of flowers, including Aesculus, Ajuga, Amelanchier, Arabis, Asclepias, Berberis, Campanula, Ceanothus, Cirsium, Cotoneaster, Crataegus, Desmodium, Dicentra, Echinacea, Erythronium, Geranium, Helianthus, Hydrophyllum, Hypericum, Lineria, Lonicera, Lupinus, Mahonia, Melilotus, Medicago, Mertensia, Monarda, Pedicularis Penstemon, Phlox, Polemonium, Prunella, Prunus, Pyrus, Ribes, Rhododendron, Rosa, Rubus, Salix, Solanum, Solidago, Spiraea, Syringa, Taraxacum, Teucrium, Tilia, Trifolium, Vaccinium, Verbena, and Vicea (Plath 1934, Macior 1968, Colla and Dumesh 2010, Colla et al. 2011, Williams et al. 2014, Tripodi and Szalanski 2015).
Nests often built underground in rodent nests, sometimes on the ground surface. Plath (1934) reported 37 nests: 2 in stone walls, 9 on the ground surface, 26 underground. Most underground nests were built 15-30 cm below ground, with entrance tunnels 23-122 cm long. Other nests built 122 cm above ground in a stack of wooden crates and under a flat rock on the ground near a stone fence (Snider and Husband 1966). Colonies are relatively small; the largest of the colonies reported by Plath (1934) contained 1 old queen, 23 young queens, about 60 workers, and several cocoons. Newly emerged males share in brood care by incubating pupae during the first 36 hours (Cameron 1985). Males patrol circuits and pursue flying objects in search of queens (Plath 1934, Williams et al. 2014).
- Literature Cited AboveLegend: View Online Publication
- Cameron, S.A. 1985. Brood care by male bumble bees. Proceedings of the National Academy of Sciences 82:6371-6373.
- Cameron, S.A., J.D. Lozier, J.P. Strange, J.B. Koch, N. Cordes, L.F. Solter, and T.L. Griswold. 2011. Patterns of widespread decline in North American bumble bees. Proceedings of the National Academy of Sciences 108(2): 662-667.
- Colla, S., L. Richardson, and P. Williams. 2011. Bumble bees of the eastern United States. Washington, DC: USDA Forest Service, Pollinator Partnership. 103 p.
- Colla, S.R. and L. Packer. 2008. Evidence for decline in eastern North American bumble bees (Hymenoptera: Apidae), with special focus on Bombus affinis Cresson. Biodiversity Conservation 17: 1379-1391.
- Colla, S.R. and S. Dumesh. 2010. The bumble bees of southern Ontario: notes on natural history and distribution. Journal of the Entomological Society of Ontario 141: 39-68.
- Colla, S.R., F. Gadallah, L. Richarson, D. Wagner, and L. Gall. 2012. Assessing declines of North American bumble bees (Bombus spp.) using museum specimens. Biodiversity and Conservation 21: 3585-3595.
- Grixti, J.C., L.T. Wong, S.A. Cameron, and C. Favret. 2009. Decline of bumble bees (Bombus) in the North American Midwest. Biological Conservation 142: 75-84.
- Hines, H.M. and S.D. Hendrix. 2005. Bumble bee (Hymenoptera: Apidae) diversity and abundance in tallgrass priaire patches: effects of local and landscape floral resources. Environmental Entomology 34(6): 1477-1484.
- Macior, L.M. 1968. Bombus (Hymenoptera, Apidae) queen foraging in relation to vernal pollination in Wisconsin. Ecology 49:20-25.
- Molumby, A. and T. Przybylowicz. 2012. Bees (Hymenoptera: Apoidea) of the Chicago area: diversity and habitat use in an urbanized landscape. Great Lakes Entomologist 45:79-98.
- Plath, O.E. 1934. Bumblebees and their ways. New York, NY: Macmillan Company. 201 p.
- Snider, R.J. and R.W. Husband. 1966. Collembola found in bumblebee nests. Transactions of the American Microscopical Society 85:473-475.
- Tripoldi, A.D. and A.L. Szalanski. 2015. The bumble bees (Hymenoptera: Apidae: Bombus) of Arkansas, fifty years later. Journal of Melittology 50: doi: http://dx.doi.org/10.17161/jom.v0i50.4834
- Williams, P., R. Thorp, L. Richardson, and S. Colla. 2014. Bumble Bees of North America. Princeton, NJ. Princeton University Press.
- Additional ReferencesLegend: View Online Publication
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- Dolan, A.C., C.M. Delphia, K.M. O'Neill, and M.A. Ivie. 2017. Bumble Bees (Hymenoptera: Apidae) of Montana. Annals of the Entomological Society of America. 110(2): 129-144.
- Kearns, C.A. and J.D. Thomson. 2001. The Natural History of Bumble Bees. Boulder, CO. University Press of Colorado.
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