U S Fish and Wildlife Service


Past Featured Pollinators:
  Allen's Hummingbird
  Buff-bellied Hummingbird
  Calliope Hummingbird
  Costa's Hummingbird
  Crested Honeycreepers
  Dakota Skipper
  El Segundo blue butterfly
  Karner blue butterfly
  Lesser long-nosed bat

Mexican long-nosed bat

  Mitchell’s Satyr
  Monarch Butterfly
  Rufous Hummingbird
  Rusty patched bumble bee
  Taylor's checkerspot butterfly
More Pollinators:
  Fringed Orchids and Hawkmoths

Fun Fact:

The rusty patched bumble bee worker bees and males have the distinctive rusty patch on their abdomen, but the queens are incognito (no rusty patch).



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Featured Pollinator

image of a Female rusty patched bumble bee
  Female rusty patched bumble bee (photo: Tamara Smith, USFWS)

The rusty patched bumble bee (Bombus affinis) lives in a variety of habitats, including prairies, woodlands, marshes, farms, parks and gardens. Once found in 29 states and 2 Canadian provinces, its current range is limited to scattered locations within 10 states:  Illinois, Indiana, Iowa, Maine, Massachusetts, Minnesota, Ohio, Virginia, Wisconsin and Ontario. The rusty patched bumble bee is listed as endangered under the Endangered Species Act.

Rusty patched bumble bees are habitat generalists, but are typically found in areas that contain natural and semi-natural upland grassland, shrubland, woodlands, and forests. They may also be found in urban or suburban areas that contain nesting habitat, nectar and pollen resources, and overwintering habitat. In the spring they are often found in and near woodland habitats.

The rusty patched bumble bee has declined by 87 percent in the last 20 years. This bee is likely present in only 0.1% of its historical range. There are many potential reasons for the rusty patched bumble bee decline including: disease, habitat loss and degradation, pesticide use and climate change. These issues, plus competition with non-native bees, and the effects of small population dynamics are threats to the rusty patched bumble bee’s survival. With the odds seemingly stacked against it, there is a role for everyone in conserving this beneficial pollinator. Your actions will also help a host of bees, butterflies and birds that share resources with the rusty patched bumble bee.

image of a Wild blue lupine (Lupinus perennis)
Wild blue lupine (Lupinus perennis), a good early season nectar source for rusty patched bumble bees.
(Photo: Lisa Hupp. USFWS)

Bumble bees use nectar and pollen from a wide variety of flowering plant species. They typically forage within 0.6 miles of their nest. The rusty patched bumble bee is one of the first bumble bees to emerge early in the spring and the last to go into hibernation and it needs pollen and nectar during that entire time. The number of queens a colony can produce is directly related to the amount of pollen available. Nectar provides carbohydrates and pollen provides protein. The primary food of larvae is pollen. Bumble bee superfoods and/or immune building plants include wild bergamot (Monarda fistulosa), prairie clover (Dalea sp.), hyssop (Agastache sp.), goldenrod (Solidago sp.), asters (Symphyotrichum sp.), leadplant (Amorpha canescens), joe pye weed (Eutrochium sp.), coneflowers (Echinacea sp.), sunflowers (Helianthus sp.), white turtlehead (Chelone glabra), and native wild blueberries and cranberries (Vaccinium sp.). Diverse flowering plants are required to ensure that nectar and pollen are available throughout the colony’s long active flight season (from March or April through October). Rusty patched bumble bees may depend on woodland spring ephemeral flowers because of their early spring emergence. The USFWS, along with partners, developed a regionally and season-specific rusty patched bumble bee plant list.

The life cycle of the rusty patched bumble bee is similar to other bumble bees. In early spring, a solitary queen (or foundress) rusty patched bumble bee initiates a colony. Queens typically establish their nests in abandoned rodent burrows or other similar cavities, one to four feet below ground. Occasionally nests have been observed above ground. The queen produces female workers throughout the summer, and reproductive individuals (males and potential queens) in mid to late summer and early fall. The males and new queens (gynes, or reproductive females) disperse to mate at the end of summer into fall (September through mid-October). The original founding queen, males, and workers die. The new queens go into diapause over winter.

image of a Woodland Sunflower (Helianthus divaricatus)

Woodland Sunflower (Helianthus divaricatus), a good food source rusty patched bumble bees.
(Photo: Gary Stolz, USFWS)

Bumble bees overwinter in small chambers in loose soil and/or leaf litter just a few centimeters below the ground, or in compost or rodent hills/mounds. Little is known about the specific overwintering habitats of rusty patched bumble bee queens. Overwintering habitat is often associated with woodland edges, which provides proximity to woodland spring ephemeral wildflowers and early blooming trees and shrubs.

The following spring, the new queen searches for a suitable nest site and collects nectar and pollen from flowers to support the production of her eggs. Eggs are laid late in spring (roughly mid-March through April/May). The eggs are fertilized using sperm the queen has stored since mating the previous fall. The queen is solely responsible for establishing the colony. As the workers hatch and the colony grows, the workers assume the responsibilities of food collection, colony defense, and care of the young, while the queen remains within the nest and continues to lay eggs.



How to help!

Find more information about rusty patched bumble bees and Endangered Species Act guidance specific to the species at: https://www.fws.gov/midwest/Endangered/insects/rpbb/.

Last Updated: June 17, 2019
June 17, 2019