Bumble Bees of Montana
Bombus auricomus (Robertson, 1903) Black and Gold Bumble Bee
Bombus auricomus is a common eastern North American bumble bee species. It is known to occur throughout eastern temperate forests west to the Great Plains (Williams et al. 2014). Prior to The Bumble Bees of Montana in 2016, the westernmost records of B. auricomus were along the western borders of North Dakota and South Dakota, though Milliron (1971) predicted its occurrence in Montana. Now, B. auricomus has been documented as far west as Pondera County.
Recorded Montana Distribution
Diagnosis
Bombus auricomus is a large bumble bee with a longer-than-wide cheek, black hairs on the face, and yellow hairs on abdominal T2 and T3. Abdominal T1 may be yellow, black, or a mixture of both. The top of the thorax in front of the wings is yellow and there is a strong black band of black hairs between the wings. However, in some individuals, the thorax behind the wings may also be black so that the only yellow on the top of the thorax is in front of the wings.
Similar Species
Bombus auricomus is most easily confused with B. nevadensis, which also has a longer-than-wide cheek, black hairs on the face, and yellow hairs on T2 and T3. However, B. nevadensis has many yellow hairs between and behind the wings so that the only black hairs on the top of the thorax are found in a small, central circle.