American bumble bee (Bombus pensylvanicus) is an iconic, but declining bumble bee. This species is strongly associated with open lands like grasslands, prairies, and even barrier islands, but has become much harder to find in the northeast in recent years. It is thought to be almost completely extirpated from states in the northern part of its range in the east, likely due in part to widespread land use change and the disappearance of low-intensity agriculture. Females can be identified by the combination of short-even hairs, dark wings, and thorax and abdominal banding.
Active April through September. Queens are typically active later than those of other bumble bee species. Colonies begin producing males and gynes (future queens) by late July and August; one new generation of reproductive individuals per year.
Scarce throughout northeast. Formerly widespread, occurring in 47 out of the 48 lower U.S. states, but now hard to find, and possibly extirpated from New England states. Restricted to strongholds in Toronto, Canada and southern part of region (southern New Jersey, Maryland, and Delaware).
The subspecies Sonoran bumble bee Bombus pensylvanicus sonorus is found in the desert southwest and Mexico.
Size > honey bee
Females: generally larger than other bumble bees; long malar space; black vertex hairs; top half of thorax yellow and bottom half black; T1 bottom half yellow (sometimes entirely yellow), T2-T3 entirely yellow, T4+ all black; noticeably short, “evenly trimmed” hair across body; dark wings
Gynes: like workers, but much bigger (often yielding exclamations about its size compared to other bees)
Males: abdomen is often entirely yellow
- Bombus auricomus is similar sized but has yellow hairs on vertex, thin yellow band of hairs on posterior half of thorax, and mostly black hairs on T1.
- Bombus fervidus males are similar but note thinner black band across thorax and sides of thorax are usually darker.
Typically occupies open lands: meadows, sand prairies, farmland, and grasslands. In the east, can often be found in low elevation piedmont, Atlantic coastal plain, and on barrier islands.
Eusocial. Mated gynes (future queens) emerge early in spring and found small colonies in cavities, typically on ground surface in thatch and beneath grassy tussocks. Small colonies produce large female workers throughout the summer, then new queens and males in the fall.
Generalized. B. pensylvanicus is long-tongue species that seems to be found most often on Fabaceae (milk-vetch [Astragalus spp.], vetches [Vicia spp.], beach pea [Lathyrus spp.]), sunflowers (Helianthus spp.), St. John’s Wort (Hypericum spp.), and thistles (Cirsium spp.).
Bombus (Psithyrus) varibilis parasitizes B. pensylvanicus.
Page last updated:
February 22, 2023