Inside Region 3
Midwest Region
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Rusty patched bumble bee. Photo courtesy of Christy Stewart/Xerces Society.

Rusty patched bumble bee. Photo courtesy of Christy Stewart/Xerces Society.

Species of Concern: The Rusty Patched Bumble Bee

Did you know that there are 21 species of bumble bees in the eastern United States? Bumble bees are among the most important pollinators of tomatoes, as well as many wildflowers. Graced with imaginative names (i.e., indiscriminate bumble bee, confusing bumble bee, Fernald cuckoo bumble bee), these species range from the familiar - such as the eastern common bumble bee - to those that are uncommon, rare, or, like the variable cuckoo bumble bee, possibly even extinct.

The rusty patched bumble bee is one of those whose populations are declining. This relatively small bumble bee was once widely distributed across the eastern United States and Upper Midwest, from Maine and southern Quebec and Ontario, south to the northeast corner of Georgia and reaching west to the eastern edges of the Dakotas. The rusty patched bumble bee occupied grasslands and tallgrass prairies, where they gathered pollen and nectar from a wide variety of flowering plants. Unfortunately, much of this habitat has disappeared, lost to other land uses, or degraded and fragmented.

Rusty patched bumble bees feed on wildflowers, including sunflowers and goldenrod. The species emerges early in the spring and is among the last to go into hibernation, so it needs a constant and diverse supply of flowers that bloom from April to September. The rusty patch needs nesting areas, such as underground and abandoned rodent cavities or clumps of grass above ground. They also require undisturbed soil for hibernating queens to overwinter.

Colonies are made up of a solitary queen, which chooses a nest site in spring, collects nectar and pollen and begins laying eggs fertilized the previous fall. Workers hatch first and help grow the colony; new queens and males hatch in late summer. At the end of the season, the queen dies, males disperse and new queens overwinter.

In 2013, the Xerces Society petitioned the Service to list the rusty patched bumble bee as endangered, citing a 95 percent decline in the bumble bee’s abundance, and as much as an 87 percent reduction in its range. The petition suggested a variety of threats to the species, including loss of habitat, pathogens, pesticide use and climate change.

In response to the petition, the Service issued a positive 90-day finding in September 2015. The Midwest Region’s Twin Cities Field Office is leading the Service effort to assess the status of the rusty patched bumble bee and will make a finding by the end of September determining whether the species warrants Endangered Species Act listing.

By Georgia Parham
Regional Office - External Affairs

Last updated: June 8, 2020