Synonyms and other taxonomic changes
Often treated as a subspecies of Bombus pensylvanicus
Similar to the very closely related pensylvanicus, but in sonorus the dorsum of the thorax is yellow posteriorly and there is a distinct black interalar band, whereas in typical pensylvanicus the dorsum of the thorax is largely or entirely black posteriorly. Unlike B. fervidus, T4 of females is black.
sw US from CA-TX, north to southern NV and southwestern UT; south to southern Mexico. Widespread in southern California but more local in northern California where best known from the Central Valley and adjacent valleys in the foothill zone (see below for status). The common bumble bee of the Sonoran and Chihuahuan deserts.
Mostly low elevations including deserts and cultivated valleys.
Strongly associated with sunflowers (Helianthus annuus
) but also visits many other plants, notably nightshades (Solanum
) and globe mallows (Sphaeralcea
). The Hosts section of its Discover Life species page
lists known floral associations based on specimen records and images.
Has declined severely in its northern California range and no longer detected at sites where it was abundant in the 1990s. Still regularly found in the Sonoran and Chihuahuan deserts but number vary greatly between years depending, reflecting in part availability of its favorite host plants whose bloom depends on irregular rainfall. Texas Parks & Wildlife considers this to be a "Species of Greatest Conservation Need" (SGCN) (1)
Warriner, M.D. (In press). Bumble bees (Hymenoptera: Apidae) of Texas: historical distributions. Southwestern Naturalist.