Bombus affinis - Rusty Patched Bumble Bee

Description and Ecology

• The Rusty patched Bumble Bee or Bombus affinis, gets its name from the distinctly shaped bronze patch found on the worker bees. Like many other species in Bombus, they have yellow and black stripes. Yellow on the first abdominal section and lower half of the second abdominal sections. Another distinguishing factor is the interesting black mark on the thorax which extends out towards the wings and down to the abdominal sections. B. affinis, previously had a wide range of habitat and was a major pollinator species for wildflowers and shrubs, as well as many agricultural crops including plum, apple, and alfalfa. Unlike many bee species, they are generalists, which means they can feed on a wide variety of flowers and are not dependent on a single plant species for foraging. Another interesting characteristic found in most bumble bee species is their ability to fly in low temperatures and low light, while “buzz pollinating.” Buzz pollination is when a bee uses the vibrations of its wings to dislodge pollen while biting the flower’s anther.

Geographic and Population Changes

• In recent years Bombus affinis’ distribution has significantly decreased. Historically, they ranged across the eastern US and southern Canada, predominantly on the northeast coast but found as far west as Minnesota and south through Georgia. Since 2006 the drastic decline has shrunk their observed range down to mainly Wisconsin, Indiana, and Minnesota.

• Research is still needed to fully understand and document the current population size, however, observations have significantly decreased in many areas.

https://xerces.org/endangered-species/species-profiles/at-risk-invertebrates/bumble-bees/rusty-patched-bumble-bee

Listing Date and Type of Listing

• Bombus affinis was first listed as endangered on March 21, 2017 largely due to petitions from environmental organizations like the Xerxes Society.

Cause of listing and main threats to its continued existence

• Although the exact cause of B. affinis’ decline is still partially unknown, a combination of factors has all contributed to the problem. Some of the main threats come from pathogens and pesticides. Various studies have explored other cultivated bumble bee species bred in Europe which carry diseases causing declines in wild bee populations. The cultivated bumble bee species interact with wild species near greenhouse and fields spreading pathogens around the distribution ranges. The application of pesticides and herbicides also have a large impact on rusty patched bumble bees by direct toxicity and indirect loss of forage and habitat. The large increase of the herbicide glyphosate used for weed control in monoculture agriculture fields has killed off many wildflowers in the surrounding areas, eliminating available pollen sources. Overall habitat loss and degradation is also linked to ag and urban developments.

• Another aspect that has not been fully studied is climate changes direct impact on rusty patched bumble bee decline. However, increasing temperatures, climate variability and storm frequency all have some impact on decreasing habitat ranges and populations.

Description of Recovery Plan

• In early 2020 a recovery plan was published, outlining the major threats and actions needed to remove Bombus affinis from the critically endangered species list. The top priority action is to minimize disease and pathogen exposure from cultivated bumble bee species. This will be accomplished through monitoring non-native bee production for pathogens and implement systems to better contain them within greenhouses. Other actions include conducting species specific research on the impact of pesticides on individual populations and enhancing existing habitats.

What can you do?

• Although the fight for species conservation often looks grim, there are still ways that each of us can support these small species and help in their recovery. One of the main problems facing rare insect species is that the public knowledge of their existence is quite small. Learning about the various species of bumble bees and how to distinguish a common agricultural species from a wild native bee, helps create a base for their protection. Other ways to contribute to the conservation efforts of Bombus affinis is to donate to organizations like the Xerxes Society which protects pollinators and advocates for policy changes.

Other resources

• The Xerxes Society: for invertebrate conservation https://xerces.org/

References

Pollinators and climate change: Building climate ... (n.d.). Retrieved November 7, 2021, from https://xerces.org/sites/default/files/publications/19-044_Climate%20Change%20FS_web%20-%20Krystal%20Eldridge.pdf.

Rusty patched Bumble Bee. Rusty Patched Bumble Bee | Xerces Society. (n.d.). Retrieved November 7, 2021, from https://xerces.org/endangered-species/species-profiles/at-risk-invertebrates/bumble-bees/rusty-patched-bumble-bee.

Species profile. ECOS. (n.d.). Retrieved November 7, 2021, from https://ecos.fws.gov/ecp/species/9383.

U.S. Fish and Wildlife Service North Atlantic-Appalachian ... (n.d.). Retrieved November 7, 2021, from https://www.fws.gov/northeast/virginiafield/pdf/endspecies/R5_endangered_species_updates/ESA_Update_39.pdf.