American bumble bee queens are between 21 and 25.5 mm long while workers and drones are smaller, between 14 and 19 mm and 16 and 22 mm, respectively. The queen's head is entirely black with a few gray hairs. The thorax is yellow towards the head and black towards the abdomen; the abdomen is yellow and black. Workers resemble the queen. A drone has a grayish-white face, a black head with some gray, and a thorax with similar coloration to the queen. On a drone, the first part of the abdomen is yellow, and the rest is variable.
- Discover Life - Apidae: Bombus pensylvanicus (DeGeer, 1773) (Discover Life)
- Bombus pennsylvanicus (Degeer), Bumble bee - Biodiversity of Great Smoky Mountains National Park (Discover Life in America, Great Smoky Mountains National Park All Taxa Biodiversity Inventory)
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