Tri-colored Bumble Bee - Bombus ternarius
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 17-19 mm in length, workers 9-13 mm. Head length medium, cheek very slightly shorter than wide; mid-leg basitarsus with far back corner rounded, outer surface of hind-leg tibia flat and lacking hair (except fringe) forming a pollen basket; hair of face and upper surface of head predominantly black with patches of yellow hair; upper side of thorax with yellow and black hairs intermixed on scutum, but front edge of black band between wings always sharply defined, and extended backwards in the middle in a dark wedge; T1 yellow, T2-3 orange, T4 yellow, T5 black. Males 10-14 mm in length; eyes similar in size and shape of any female bumble bee; antennae medium long, flagellum 2.5-3X the length of scape; hair color pattern similar to queens and workers, but black wedge on upper surface of thorax less obvious (Colla et al. 2011, Williams et al. 2014).
Across the range, queens reported March to September, workers April to October, males July to October (Colla et al. 2011, Williams et al. 2014). In southern Ontario, queens reported April to September, workers May to September, males July to October; earliest record 15 April (Colla and Dumesh 2010). One of the earliest bumble bees to become active in spring in the eastern United States, with an early date of 5 April (Plath 1934)
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 outer surface concave and hairless (except fringe) forming pollen basket; cheek as long as wide; face with yellow hairs at least centrally; scutum with yellow and black hairs intermixed, giving a cloudy appearance; scutellum with yellow or pale yellow hairs divided by line or wedge of black hair; T2-3 orange, T5 black, hairs short and even; coxae often with yellow hair.
Resident Year Round
Recorded Montana Distribution
Click the map for additional distribution information.
Primarily across southern Canada and the adjacent region of the United States, from Quebec and New England to the Rocky Mountains of Alberta (Colla et al. 2011, Williams et al. 2014). Continues to persist throughout much of range in eastern North America, increasing locally at some sites but extirpated at others (Colla and Packer 2008, Grixti et al. 2009, Colla et al. 2012)
Near and in woodlands, old fields, irrigated grassland and forested riparian, aspen parkland (Hobbs 1967, Richards 1978, Johnson 1986, Colla and Dumesh 2010).
Feeds on a variety of flowers, including Agastache, Aralia, Asclepias, Astragalus, Centaurea, Cirsium, Claytonia, Daucus, Epilobium, Eupatorium, Hypericum, Geranium, Impatiens, Iris, Ledum, Medicago, Melilotus, Mentha, Potentilla, Prunus, Rhodora, Rhododendron, Rosa, Rubus, Salix, Solidago, Spiraea, Symphyotrichum, Syringa, Taraxacum, Tilia, Trifolium, Vaccinium, Verbascum, Verbena, and Vicia (Plath 1934, Heinrich 1976, Johnson 1986, Colla and Dumesh 2010, Colla et al. 2011, Williams et al. 2014).
Nests most often underground (Williams et al. 2014). In southern Alberta, 84% of 19 nests reported were built underground. Nests initiated in late May to early June (Hobbs 1967, Richards 1978). Plath (1934) reported a nest excavated in September; the nest had an entrance tunnel 183 cm long leading to the nest 61 cm below the ground surface. This nest contained 23 young queens, 16 males, more than 100 workers, and at least 75 queen pupae (cocoons). Number of pupae in first broods in southern Alberta averaged 9.2; number of eggs laid per cell in second and third broods averaged 3.7 (Hobbs 1967). Males patrol circuits in search of queens. Nests sometimes parasitized by the cuckoo bumble bee Bombus insularis (Williams et al. 2014).
- Literature Cited AboveLegend: View Online Publication
- 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.
- Heinrich, B. 1976. Resource partitioning among some eusocial insects: bumblebees. Ecology 57(5): 874-889.
- Hobbs, G.A. 1967. Ecology of species of Bombus Latr. (Hymenoptera: Apidae) in southern Alberta. VI. Subgenus Pyrobombus. Canadian Entomologist 99: 1271-1292.
- Johnson, R.A. 1986. Intraspecific resource partitioning in the bumble bees Bombus ternarius and B. pennsylvanicus. Ecology 67:133-138.
- Plath, O.E. 1934. Bumblebees and their ways. New York, NY: Macmillan Company. 201 p.
- Richards, K.W. 1978. Nest site selection by bumble bees (Hymenoptera: Apidae) in southern Alberta. Canadian Entomologist 110(3): 301-318.
- 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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- Kearns, C.A. and J.D. Thomson. 2001. The Natural History of Bumble Bees. Boulder, CO. University Press of Colorado.
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