Sitka Bumble Bee - Bombus sitkensis
For definitions and diagrams of bumble bee morphology please see the Montana State Entomology Collection's Bumble Bee Morphology page
. A medium-tongued, small-sized bumble bee: queens 15-20 mm in length, workers 9-14 mm. Hair long, shaggy, uneven; head length medium, cheek as long as wide; mid-leg basitarsus with back far corner rounded, hind-leg tibia outer surface flat and hairless (except fringe) forming pollen basket; hair on upper surface of thorax yellow but densely intermixed with black especially between wings and on scutellum; T1 yellow, T2 with yellow often narrowly interrupted by black especially at back or intermixed with black, T5 almost entirely pale brownish yellow (yellow and orange hairs intermixed). Males 9-14 mm in length; eyes similar in size and shape to eyes of any female Bombus
; antennae medium length, flagellum 3X longer than scape; hair color pattern similar to queens and workers, but upper side of thorax with more yellow hair intermixed with black between wings; T3 usually with pale fringe of yellow hair at back or entirely yellow (Koch et al. 2012, Williams et al. 2014).
Across the range, queens reported March to September, workers April to September, males April to October (Williams et al. 2014). In Washington, queens reported March to August, workers May to October, males April to October (Koch et al. 2012); in California, queens late January to early December, workers early March to late September, males early April to early September (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-leg tibia outer surface concave and hairless (except fringe) forming a pollen basket; T1-2 and T4-5 with yellow and/or orange hairs; cheek as long or slightly longer than wide; scutum cloudy (yellow and black hairs intermixed); scutellum distinctly darker than scutum (many black hairs intermixed throughout).
Resident Year Round
Recorded Montana Distribution
Click the map for additional distribution information.
Along the Pacific Coast from southern Alaska to central California in the Cascade Mountains and Coast Ranges, and inland in the Rocky Mountains from central British Columbia and Alberta south through northern Idaho, western Montana, to extreme northwestern Wyoming (Koch at al. 2012, Williams et al. 2014). Some possible declines in urban range due to competition with Bombus vosnesenskii (McFrederick and LeBuhn 2006).
Open grassy prairie, montane meadows, urban gardens and parks, commercial blueberry and cranberry cropland (McFrederick and LeBuhn 2006, Ratti et al. 2008, Wojcik et al. 2008, Williams et al. 2014).
Feeds on a variety of flowers, including Aquilegia, Brassica, Ceanothus, Cirsium, Epilobium, Lupinus, Phacelia, Rhododendron, Ribes, Rosa, Rubus, Salix, Solidago, Vaccinium and Vicea (Thorp et al. 1983, Wilson et al. 2010, Koch et al. 2012, Williams et al. 2014). A minor pollinator in crops of commercial Vaccinium (highbush blueberry and cranberry) in southern British Columbia (Ratti et al. 2008).
Little information. Nests built underground, presumably in rodent burrows (McFrederick and LeBuhn 2006). Males patrol circuits in search of queens (Williams et al. 2014).
- Literature Cited AboveLegend: View Online Publication
- Koch, J., J. Strange, and P. Williams. 2012. Bumble bees of the western United States. Washington, DC: USDA Forest Service, Pollinator Partnership. 143 p.
- McFrederick, Q.S. and G. LeBuhn. 2006. Are urban parks refuges for bumble bees Bombus spp. (Hymenoptera: Apidae)? Biological Conservation 129: 372-382.
- Ratti, C.M., H.A. Higo, T.L. Griswold, and M.L. Winston. 2008. Bumble bees influence berry size in comercial Vaccinium spp. cultivation in British Columbia. Canadian Entomologist 140(3): 348-363.
- Thorp, R.W., D.S. Horning, and L.L. Dunning. 1983. Bumble bees and cuckoo bumble bees of California (Hymenoptera: Apidae). Bulletin of the California Insect Survey 23:1-79.
- Williams, P., R. Thorp, L. Richardson, and S. Colla. 2014. Bumble Bees of North America. Princeton, NJ. Princeton University Press.
- Wilson, J.S., L.E. Wilson, L.D. Loftis, and T. Griswold. 2010. The montane bee fauna of north central Washington, USA, with floral associations. Western North American Naturalist 70(2): 198-207.
- Wojcik, V.A., G.W. Frankie, R.W. Thorp, and J.L. Hernandez. 2008. Seasonality in bees and their floral resource plants at a constructed urban bee habitat in Berkeley, California. Journal of the Kansas Entomological Society 81: 15-28.
- Additional ReferencesLegend: View Online Publication
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- Kearns, C.A. and J.D. Thomson. 2001. The Natural History of Bumble Bees. Boulder, CO. University Press of Colorado.
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