Bombus vagans is a long-haired, medium-tongued bumble bee species. In Minnesota, gynes begin emerging from hibernation in early May, then establish a nest belowground in abandoned mouse nests or rodent burrows or less often aboveground. Workers begin emerging at the end of May, males mid-July, and new gynes at the beginning of August.
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Distinguishing Bombus vagans from Bombus sandersoni is difficult in the field, but detailed photos that include views of the side of the head for females and antennae for males can help. Bombus vagans females have a longer face and malar space than Bombus sandersoni. Sometimes B. vagans females have a more distinct black spot on the thorax versus black hairs between the wing bases for Bombus sandersoni. Bombus vagans males have a long third flagellum (segment of the antennal flagellum is 2 times longer than broad) and lack hair on underside of first and second flagellomere; B. sandersoni males have a shorter third flagellum (1.5 times longer than broad) and short hairs on the first and second flagellomere. Bombus vagans has yellow hairs on the first and second tergites (T1 and T2), and for males, often additional light hairs on the outer edges of the third through sixth (T3-T6) tergites. In addition, the southern parts of Minnesota are outside of the documented range for B. sandersoni. Both males and females have yellow hairs on the vertex; females have black hairs mixed with scattered light hairs on the face, males have yellow hairs on the face. 

female