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
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. edwardsU, melanopygus, sUkensis, and sylvicola. It appears to be most closely (Sarcophagidae) as the principal parasite in nests of B. mixtus.