Plants and Animals

Bombus affinis Rusty-patched bumble bee

Key Characteristics

Rusty-patched males and workers are medium-sized bumblebees, averaging .5 inches in length, with stocky, round head, face, and area between the wings being black in color, while the remainder of the thorax is yellow.  Abdominal coloration varies. Typically, the first segment (fused to the thorax) is yellow, and the second segment half yellow and half brown, but in some individuals both segments are brown. Rarely, there will be reddish pile on other abdominal segments (3-6). Queens are larger (about .8 inches), with the thorax and first two abdominal segments being yellow, while the remainder of the abdomen is dark black.

Status and Rank

US Status: LE - Listed Endangered
State Status: SC - Special Concern (rare or uncertain; not legally protected)
Global Rank: G1 - Critically imperiled
State Rank: SNR - Not ranked

Occurrences

CountyNumber of OccurrencesYear Last Observed
Allegan11955
Barry11955
Clinton11955
Ingham11964
Kent11937
Lenawee11979
Mecosta11965
Ottawa11954

Information is summarized from MNFI's database of rare species and community occurrences. Data may not reflect true distribution since much of the state has not been thoroughly surveyed.

Habitat

With foraging habitat that includes dunes, marshes, forests, farmland and urban areas, the rusty-patched bumble bee is considered a habitat generalist. Nests are usually underground, in old rodent burrows. Most Bombus queens overwinter in rotten wood or underground (COSEWIC 2010).

Natural Community Types

  • Unknown

For each species, lists of natural communities were derived from review of the nearly 6,500 element occurrences in the MNFI database, in addition to herbarium label data for some taxa. In most cases, at least one specimen record exists for each listed natural community. For certain taxa, especially poorly collected or extirpated species of prairie and savanna habitats, natural community lists were derived from inferences from collection sites and habitat preferences in immediately adjacent states (particularly Indiana and Illinois). Natural communities are not listed for those species documented only from altered or ruderal habitats in Michigan, especially for taxa that occur in a variety of habitats outside of the state.

Natural communities are not listed in order of frequency of occurrence, but are rather derived from the full set of natural communities, organized by Ecological Group. In many cases, the general habitat descriptions should provide greater clarity and direction to the surveyor. In future versions of the Rare Species Explorer, we hope to incorporate natural community fidelity ranks for each taxon.

Management Recommendations

Common and widespread in its distribution prior to the mid-1990s, this species, along with several other North American bumblebees of the same subgenus, has recently experienced dramatic declines throughout its range (COSEWIC 2010). These losses are primarily attributed to three main threats: the widespread use of neonicotinoids, a pesticide group highly toxic to bees, on cropland since the early 1990s; both nesting and foraging habitat loss due to increased urbanization and intensified agricultural landscapes, particularly the conversion of pasture to corn and soybeans; and the spread of pathogens from bumblebees used as pollinators in commercial greenhouse operations to wild populations nearby (Colla and Packer 2008, COSEWIC 2010, Grixti et al. 2009). Conservation strategies for bumblebees center around preserving healthy natural habitat areas, reducing pesticide/herbicide use, and promoting native wildflower reestablishment within urban and agricultural landscapes. Additionally, planting hedgerows and restoring native grasses along field margins, and in urban parks and residential yards provides habitat for small mammals, whose abandoned holes will in turn become bumblebee nesting and hibernating habitat (Goulson 2010).

Active Period

Active from third week of April to fourth week of October

Survey Methods

Surveys typically involve capturing foraging bumblebees with an aerial net and identifying the individual species (Colla and Packer 2008, Grixti et al. 2009).

Aerial net, visual survey

Survey Period: From third week of April to fourth week of October

Time of Day: Daytime

References

Survey References

  • Colla, S.R. and L. Packer. 2008. Evidence for decline in eastern North American bumblebees (Hymenoptera: Apidae), with special focus on Bombus affinis Cresson. Biodiversity and Conservation 17: 1379-91.
  • Grixti, J.C., L.T. Wong, S.A. Cameron and C. Favret. 2009. Decline of bumble bees (Bombus) in the North American Midwest. Biological Conservation 142: 75-84.

Technical References

  • Colla, S.R. and L. Packer. 2008. Evidence for decline in eastern North American bumblebees (Hymenoptera: Apidae), with special focus on Bombus affinis Cresson. Biodiversity and Conservation 17: 1379-91.
  • COSEWIC. 2010. COSEWIC assessment and status report on the Rusty-patched Bumble Bee Bombus affinis in Canada. Commitee on the Status of Endangered Wildlife in Canada. Ottawa. 34pp.
  • Goulson, D. 2010. bumblebees: behavior, ecology and conservation. Second Edition. Oxford University Press, New York. 317pp.
  • Grixti, J.C., L.T. Wong, S.A. Cameron and C. Favret. 2009. Decline of bumble bees (Bombus) in the North American Midwest. Biological Conservation 142: 75-84.