Bumble Bees of Montana
Bombus (Subterraneobombus) appositus Cresson, 1878 White-Shouldered Bumble Bee
Bombus appositus is a commonly collected bumble bee in Montana. In North America, it is considered a western bee, known to occur in the Rocky Mountain region from New Mexico to Alberta and British Columbia (Williams et al. 2014). In Montana, it has been most commonly collected in the western counties, though one specimen was recorded as far east as Valley County (MTEC).
Bombus appositus is a large bumble bee with pale yellow to gray-white hairs on the face. Abdominal T1-T5 are yellow to orange-brown. Its cheek is longer-than-wide and the hairs on the side of the thorax are predominantly black.
Bombus appositus is most easily confused with B. fervidus and B. borealis in Montana. However, B. fervidus has black hairs on the face and only T1-T4 are yellow. Bombus borealis has many black hairs on T5.