Although the Sanderson's bumble bee is deprioritized in terms of conservation, bumble bees that were once common, such as B. affinis, can rapidly decline. One of the main reasons B. sandersoni is under-reported in its range is due to the difficulty in telling it apart from other bumble bee species (1). It is also at higher risk as it has a low tolerance for changes in climate. The species ranges from Maine to Tennessee and west towards Minnesota extending into Canada (2). In Maryland, it is rare in the western panhandle and Frederick County (3, 4).
The species can be difficult to identify as it is similar to other bumble bees, most notably the half-black bumble bee (Bombus vagans) and confusing bumble bee (Bombus perplexus). The Sanderson's bumble bee has a primarily yellow thorax, the sides colored yellow while the backside between the wings has a black patch. The first two abdominal segments are yellow, with the second one having a few scattered black hairs while the rest of the abdomen is primarily black. The species is smaller in body size when compared with B. vagans (5, 6). Click here for further identification tools (see pages 31–33).
After hibernating, queen bees emerge in May and search for food and a place to begin their colonies. They initially give birth to worker bees who help feed the young. Into the summer, once the colony has enough workers, males and potential new queens are also born, who leave the nest and mate. The new queens then prepare for hibernation as the rest of the colony succumbs to the winter (2, 6).
Bumble bees are generalists and have a long activity period. The B. sandersoni queens are active from May to July, while workers and males start and end one month later (6). Examples of plants this species pollinate include those of the Epilobium, Monarda, and Rubus genera (2, 5, 6).
The species is found in or near wooded areas such as the temperate and boreal forests of its range, as well as the Great Plains and tundra (2, 3, 5). It can be found at higher elevations such as along the Appalachian Mountains (2, 4). It usually nests underground in abandoned rodent burrows, but can also nest above ground in grass, abandoned bird nests, rocks, or dead trees (2).
In general, bumble bees are vulnerable due to manmade causes. Preserving habitats for nesting and foraging as well as reducing the use of pesticides are key to helping them (2).
(Monarda punctata)
(Epilobium coloratum)
© 2022 Price Lab for Entomology, Min Oo, and Dana L. Price