Montana Field Guide

For definitions and diagrams of bumble bee morphology please see the Montana State Entomology Collection's Bumble Bee Morphology page. A small species: queens 17-18 mm, no workers. Hair medium length; hind leg tibia with convex outer surface and covered with hair (no pollen basket); Hair of face black with at most a few yellow hairs above antenna base; T1 often black in west and yellow in east; T2 black; T4 mostly yellow with a small patch of black at front; T5-6 black; T6 strongly curled under abdomen and pointing anteriorly. Male 11-15 mm; eye similar in size and shape to that of any bumble bee female; antennae medium length, flagellu 3X longer that scape; hair of face black; T1-3 sometimes nearly completely yellow; T4 yellow with at most a few black hairs near midline; T6-7 orange that often have paler tips (Kock et al. 2012, Williams et al. 2014).

Range-wide, queens active March to September, males May to September (Colla et al. 2011, Koch et al. 2012, Williams et al. 2014). In southern Ontario, queens active May to September, males June to September; earliest spring record 27 May (Colla and Dumesh 2010). In California, queens reported early April to early August, males early May to late September (Thorp et al. 1983).

Please see the Montana State Entomology Collection's Key to Female Bumble Bees in Montana. Outer surface of the hind tibia convex, densely hairy and lacking a pollen basket separates B. fernaldae from other Bombus except other cuckoo bumble bees. A combination of an occiput with predominantly yellow hairs, hairs of face predominantly black around the base of the antennae, and T6 often tightly curled forward under the abdomen, separate females of this species from other Bombus (Colla et al. 2011, Koch et al. 2012).

Poorly described. Openings and meadow edges in montane and boreal forest, including to near treeline or above (Ostevik et al. 2010, Wilson et al. 2010).

Visits a variety of of plants, including Arctostaphylos, Asclepias, Aster, Chrysothamnus, Cirsium, Eriogonum, Haplopappus, Helianthus, Hieracium, Melilotus, Potentilla, Rhododendron, Ribes, Rubus, Senecio, Smelowskia, Solidago, Tanacetum, Taraxacum, Trifolium, Vaccinium, Veratrum and Viguiera (Thorp et al. 1983, Wilson et al. 2010, Colla and Dumesh 2010, Colla et al. 2011, Koch et al. 2012, Williams et al. 2014).

Parasitic on other Bombus. Queens invade nests of host species, subduing or killing the host queen and nesting in colonies of other bumble bees, especially B. rufocinctus, but recorded from colonies of B. appositus and B. occidentalis (Hobbs 1965b, 1966b, 1968; Williams 2014). Also reported to parasitize particularly nests of bumble bees in the subgenus Pyrobombus, but host specificity not clear (Hobbs 1967). Host workers raise the parasite brood, so B. fernaldae produces no workers, only queens and males.