Williams, Paul H., Robbin W. Thorp, Leif L. Richardson, and Sheila R. Colla. Bumble Bees of North America: An Identification Guide. Princeton University Press, 2014. http://www.jstor.org/stable/j.ctt6wpzr9.
- has the best modern color guides for identification of both sexes, microscopic identification characters, range and natural history notes.
Extracted from Jonathan Koch, James Strange ,Paul Williams.2012. Bumble Bees of the Western United States. A product of the U.S. Forest Service and the Pollinator Partnership with funding from the National Fish and Wildlife Foundation
Distribution: Pacific coast, east to the Colorado Rocky Mountains; north to Alaska; primarily associated with high elevations and northern latitudes
Can be confused with B. frigidus
Thorax predominantly clouded with yellow and black,
T1 yellow, T2 yellow sometimes black apically, T3 orange sometimes black basally, T4-5 orange, face square.
Mid leg basitarsus with the distal posterior corner rounded. Cheek as long as broad. Hair of the face black and yellow intermixed, corbicular fringes extensively pale orange. T2 anterolaterally sometimes with scattered black hairs intermixed. Hair length
medium and uneven.
Extracted from Bumble Bees and Cuckoo Bumble Bees of California by Thorp, R. (1983).
Discussion. B. mixtus belongs to the group of species which includes B. edwardsii, melanopygus, sitkensis, and sylvicola. It appears a Sarcophagidae fly is the principal parasite in nests of B. mixtus.
Extracted from: Laverty T.M., & Harder L.D., (1988). The Bumble Bees of Eastern Canada. Can. Ent. 120: 965-987.
Description. All castes range from small to medium in body size. Head slightly elongate; malar space square in female, longer than wide in male. Tongue short. Color pattern as in Figure 11. Some females have black pile on the posterior margins of T2.