Rusty-patched bumble bee
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Rusty-patched bumble bee
Rusty-patched bumble bee
Scientific Name
Scientific Name
(Bombus affinis)
(Bombus affinis)
The rusty-patched bumble bee historically ranged across eastern North America, from Maine to Georgia, west towards North Dakota, and north into Canada (1, 2). Unfortunately, the species has since declined from ~ 87% of its historical range (1, 2, 3). It is thought that pathogens from commercial bumble bees have spread to B. affinis (1, 2). In Maryland, the species has not been reported in about two decades (2, 3).
Identification
Identification
The rusty-patched bumble bee is specifically named for the rust-colored patch on the middle of its second abdominal segment that most of the species has (1, 4). While females may vary, males will always have a rusty patch (4). Another distinct feature is the patch of black hair on the back of the thorax that extends towards the wings and downwards in a V-shape (1, 4).
Individuals that lack the rust-colored patch, such as the queens of this species, can be difficult to tell apart from other bumble bees in the state. However, B. affinis still has other features that distinguish them, such as the facial structure (1). Click this page by the Xerxes Society and this guide (see pages 46-49) on bumble bees of the eastern US for further identification tips.
Male. Photo by USGS Bee Inventory and Monitoring Lab from Beltsville, MD, USA.Public Domain.This image has been modified from the original.
Worker. Photo by USGS Bee Inventory and Monitoring Lab from Beltsville, MD, USA.Public Domain.This image has been modified from the original.
Queen. Photo by USGS Bee Inventory and Monitoring Lab from Beltsville, MD, USA.Public Domain.This image has been modified from the original.
Bombus vagans (shown below) and B. bimaculatus are distinct from B. affinis in having a longer face.
Bombus vagans. Photo by USGS Bee Inventory and Monitoring Lab from Beltsville, MD, USA.Public Domain.This image has been modified from the original.
The bumble bees, B. griseocollis (shown below), B. impatiens, and B. bimaculutus are distinct in having the patch of black hair on the back of their thorax not extended towards the wings like it does for B. affinis. Their abdomens are also more covered in black hairs.
Bombus grisecocollis. Photo by USGS Bee Inventory and Monitoring Lab from Beltsville, MD, USA.Public Domain.This image has been modified from the original.
Life cycle
Life cycle
After hibernating, queen bees emerge in spring and search for food and a place to begin their colonies. They initially give birth to worker bees who help feed the young. Into the summer, once the colony has enough workers, males and potential new queens are also born, who leave the nest and mate. The new queens then prepare for hibernation as the rest of the colony succumbs to the winter (2).
Bumble bees are generalists and have a long activity period. Bombus affinis adults are active from April to October allowing them to be the primary pollinators of many essential plants (2). Specifically, it is an excellent pollinator of cranberry, apple, alfalfa, onion, and wildflowers (1, 2).
Habitat
Habitat
The species requires a temperate climate although it is relatively cold-tolerant compared to other bumble bees, even being found at higher elevations in the southern parts of its range. It usually nests underground in abandoned rodent burrows and forages in a variety of areas including farmland, marshes, woodlands, and sand dunes. Queen bees likely hibernate underground or in logs similar to other bumble bees (2).
Distribution in Maryland
Distribution in Maryland
Data from Maryland Biodiversity Project and Discover Life. Includes historical records and may overrepresent the current range of the species.
How you can help?
How you can help?
As bumble bees are generalists, they do not depend on just one type of plant, however many plants depend on them, and the rusty-patched bumble bee specifically, for pollination (1). Growing a variety of plants throughout the season, especially those that bloom quickly and early on in the spring as B. affinis queens are some of the first to emerge, is helpful. As with most bee species, the reduction of pesticides is essential (5).
Examples of Plants
Examples of Plants
Common dandelion
Common dandelion
(Taraxacum officinale)
Alfalfa
Alfalfa
(Medicago sativa)
References
References
- Thorp, R. W., E. Evans, S. Jepsen, and S. H. Black. 2018. Rusty Patched Bumble Bee. The Xerces Society of Invertebrate Conservation. https://www.xerces.org/endangered-species/species-profiles/at-risk-invertebrates/bumble-bees/rusty-patched-bumble-bee. Last accessed 20 April 2022.
- Colla, S. R, and L. Packer. 2010. COSEWIC Assessment and Status Report on the Rusty-patched bumble bee Bombus affinis in Canada. Committee on the Status of Endangered Wildlife in Canada.
- Martin, S. 2017. TU's Bombus affinis collection is the bees' knees. Towson University. https://www.towson.edu/news/2017/beecollection.html. Last accessed 20 April 2022.
- Colla, S. R., L. L. Richardson, and P. H. Williams. 2011. Bumble Bees of the Eastern United States. U.S. Department of Agriculture and Pollinator Partnership. https://www.xerces.org/sites/default/files/2018-05/12-052_01_Eastern_Bumble_Bee.pdf. Last accessed 20 April 2022.
- Parham, G. 2021. Saving the rusty patch – one garden at a time. U.S. Fish & Wildlife Service. https://fws.gov/story/saving-rusty-patch. Last accessed 20 April 2022.
© 2020 Price Lab for Entomology, Min Oo, and Dana L. Price
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