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Contact information
For information on Wisconsin's rare vertebrate animals, contact:
Rich Staffen
Conservation Biologist
For information on Wisconsin's rare invertebrates, contact:
Jay Watson
Conservation Biologist

Rusty Patched Bumble Bee (Bombus affinis)



Rusty Patched Bumble Bee (Bombus affinis), listed as Federally Endangered and State Special Concern, is extremely rare in Wisconsin and is considered both state- and globally-imperiled. This bee relies on diverse and abundant flowering plant species in proximity to suitable overwintering sites for hibernating queens, which include, but are not limited to non-compacted and often sandy soils or woodlands, but does not include wetlands. Suitable active season habitat includes but is not limited to prairies, woodlands, marshes/wetlands, agricultural landscapes, and residential parks and gardens. Nectar plants include Aesculus (buckeye), Agastache (hyssops), Asters, Helianthus (sunflowers), Lonicera (honeysuckles), Monarda (bee balms), Physotegia (obedient plant), Prunus (plums/cherries), Solidago (goldenrods), and Vaccinium (blueberry). Queens emerge from hibernation in April and the colony is active through October. In Wisconsin, recent observation are mostly from the southern half of the state.

The USFWS has created a Rusty Patched Bumble Bee High Potential Zone to show where there is a high likelihood for the species to be present. If a project overlaps with this zone then steps should be taken to determine if suitable habitat is present for the bee and if necessary surveys can be conducted. Shapefiles of the zone can be found on the FWS bee guidance page.

State status

Status and Natural Heritage Inventory documented occurrences in Wisconsin

The table below provides information about the protected status - both state and federal - and the rank (S and G Ranks) for Rusty Patched Bumble Bee (Bombus affinis). See the Working List Key for more information about abbreviations. Counties shaded blue have documented occurrences for this species in the Wisconsin Natural Heritage Inventory database. The map is provided as a general reference of where occurrences of this species meet NHI data standards and is not meant as a comprehensive map of all observations.

Note: Species recently added to the NHI Working List may temporarily have blank occurrence maps.

Documented locations of Bombus affinis in the Natural Heritage Inventory Database as of July 2015.
Summary Information
State StatusSC/FL
Federal Status in WisconsinLE
State RankS1
Global RankG2
Tracked by NHIY

Species guidance

The USFWS has put together guidance documents that can be followed to determine if suitable habitat is present on site and the next steps to take if you believe your project may impact the bee.

Wisconsin Natural Heritage Inventory Screening Guidance for the Rusty Patched Bumble Bee [PDF]



Rusty Patched Bumble Bee

Worker on wild bergamot (Monarda fistulosa)

Photo by Jay Watson, WDNR.

Rusty Patched Bumble Bee

Gyne nectar robbing on obedient plant (Physostegia virginiana)

Photo by Jay Watson, WDNR.

Rusty Patched Bumble Bee

Photo © Susan Carpenter.

Rusty Patched Bumble Bee

Photo © Susan Carpenter.

Wildlife Action Plan

Wisconsin Wildlife Action Plan graphic

Natural community (habitat) associations

The table below lists the natural communities that are associated with Rusty Patched Bumble Bee. Only natural communities for which Rusty Patched Bumble Bee is "high" (score=3) or "moderate" (score=2) associated are shown. See the key to association scores for complete definitions. Please see the Wildlife Action Plan to learn how this information was developed.

Natural community Score

Ecological landscape associations

The table below lists the ecological landscape association scores for Rusty Patched Bumble Bee. The scores correspond to the map (3=High, 2=Moderate, 1=Low, 0=None). For more information, please see the Wildlife Action Plan.

This map shows the probability of Rusty Patched Bumble Bee occurring in each of Wisconsin's Ecological Landscapes.  Actual scores can be found in the table to the left.

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Landscape-Community combinations of highest ecological priority*

Ecological priorities are the combinations of natural communities and ecological landscapes that provide Wisconsin's best opportunities to conserve important habitats for a given Species of Greatest Conservation Need. The 10 highest scoring combinations are considered ecological priorities and are listed below. More than 10 combinations are listed if multiple combinations tied for 10th place. For more information, please see the Wildlife Action Plan.

* Ecological priority score is a relative measure that is not meant for comparison between species. This score does not consider socio-economical factors that may dictate protection and/or management priorities differently than those determined solely by ecological analysis. Further, a low ecological priority score does not imply that management or preservation should not occur on a site if there are important reasons for doing so locally.

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Issues/threats and conservation actions

Conservation actions respond to issues or threats, which adversely affect species of greatest conservation need (SGCN) or their habitats. Besides actions such as restoring wetlands or planting resilient tree species in northern communities, research, surveys and monitoring are also among conservation actions described in the WWAP because lack of information can threaten our ability to successfully preserve and care for natural resources.

Threats/issues and conservations actions for rare animals

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Last revised: Thursday, October 08, 2020