''Bombus appositus'' is a species of

bumblebee A bumblebee (or bumble bee, bumble-bee, or humble-bee) is any of over 250 species in the genus ''Bombus'', part of Apidae, one of the bee families. This genus is the only extant group in the tribe Bombini, though a few extinct related gener ...

known commonly as the white-shouldered bumblebee.Hatfield, R., et al. 2015
''Bombus appositus''.
The IUCN Red List of Threatened Species. Downloaded on 04 March 2016.NatureServe. 2015
''Bombus appositus''.
NatureServe Explorer Version 7.1. Accessed 4 March 2016. It is native to western

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

, including western Canada and the western United States. This species lives in open habitat, such as meadows and slopes. It nests underground or on the surface. Males congregate to seek mates. It feeds on a variety of plant taxa, including giant hyssops,

thistle Thistle is the common name of a group of flowering plants characterised by leaves with sharp prickles on the margins, mostly in the family Asteraceae. Prickles can also occur all over the planton the stem and on the flat parts of the leaves. ...

s, gentians, owl's clovers, locoweeds,

penstemon ''Penstemon'' , the beardtongues, is a large genus of roughly 250 species of flowering plants native mostly to the Nearctic, but with a few species also found in the North American portion of the Neotropics. It is the largest genus of flowering ...

s, and

clover Clover or trefoil are common names for plants of the genus ''Trifolium'' (from Latin ''tres'' 'three' + ''folium'' 'leaf'), consisting of about 300 species of flowering plants in the legume or pea family Fabaceae originating in Europe. The genus ...

s. It especially favors subalpine larkspur (''Delphinium barbeyi'') and it serves as one of the plant's main pollinators.Manson, J. S., et al. (2013)
Dose‐dependent effects of nectar alkaloids in a montane plant–pollinator community.
''Journal of Ecology'', 101(6), 1604-1612. This species is a host to ''

Bombus insularis ''Bombus insularis'' is a species of bumblebee in the subgenus ''Psithyrus'', the psithyrus, cuckoo bumblebees. It is native to northern and western North America, where it occurs throughout Canada, Alaska, the northern United States, and some we ...

'', a species of

cuckoo bumblebee Cuckoo bumblebees are members of the subgenus ''Psithyrus'' in the bumblebee genus ''Bumblebee, Bombus''. Until recently, the 28 species of ''Psithyrus'' were considered to constitute a separate genus. They are a specialized Social parasitism (b ...

References

Bumblebees Hymenoptera of North America Insects described in 1878 {{bombus-stub