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Bombus pensylvanicus (De Geer, 1773)
American Bumblebee
Federal Protection: No US federal protection
State Protection: No Georgia state protection
Global Rank: G3G4
State Rank: SNR
Element Locations Tracked in Biotics: Yes
SWAP 2015 Species of Greatest Conservation Need (SGCN): No
SWAP 2025 Species of Greatest Conservation Need (SGCN): Yes
2025 SGCN Priority Tier: High Conservation Concern
Element Occurrences (EOs) in Georgia: 85
Habitat Summary for element in Georgia: Grasslands, fields, and urban areas
Bombus pensylvanicus is a large bumble bee species that has been experiencing considerable population declines in recent years. The queens and workers have a similar color pattern with a black head, a black band in the middle of the thorax that extends into the first segment of the abdomen, and a black tail. The males look similar but are usually more yellow. Generally, queens measure 21-25 mm, workers measure 14-18 mm and males measure 16-22 mm in length.
*See graphic at the bottom of the page*
The most similar species are Bombus fraternus, the Southern Plains Bumble Bee, Bombus auricomus, the Black and Gold Bumble Bee, and Bombus terricola, the Yellow-banded Bumble Bee due to similar coloration and size. The American Bumble Bee can usually be distinguished from B. fraternus and B. auricomus by having a black band that begins halfway down the thorax and extends onto the first segment of the abdomen. With the other species, the black band does not typically extend onto the abdomen. B. terricola can be distinguished from this species by having a yellow band on the lower part of the tail. In contrast, B. pensylvanicus has a completely black tail.
The American Bumble Bee thrives in grassland habitats and can be found in farmland, fields, and urban areas. This bumble bee nests as a colony on the surface of the ground, in tufts of grass, in abandoned birds' nests, rocks, etc.
B. pensylvanicus nectars on a variety of wildflowers including vetches (Vicia), clovers (Trefoilium), goldenrods (Solidago), St. John’s wort (Hypericum perforatum), and boneset (Eupatorium) (Kelly Rourke, https://www.fs.fed.us).
Like other bumble bees, B. pensylvanicus is eusocial meaning they practice an organized social system. A mated queen will spend the winter hibernating and then emerge to start her new colony in the spring. She will forage and collect nectar and pollen to feed her first brood of workers. When mature, worker bees will assist the queen with foraging and colony maintenance. The queen will continue to lay eggs throughout the summer. Males, also known as drones, and new queens will emerge at the end of summer. Newly mated queens will hibernate and find new nest locations to restart the cycle.
Survey where preferred flowers are present. Photography, sweep nets, bee bowls, malaise traps, and vane traps can be used to survey this species. However, due to species declines, no-kill survey methods are preferred.
The current range of the American Bumble bee has narrowed significantly and is now mostly limited to Florida, west to Colorado, Texas, and New Mexico (Kelly Rourke, https://www.fs.fed.us).
The current Georgia range is still being studied, but it likely occurs throughout the state.
The major threats to this species are disease, habitat destruction due to commercial, residential, and agricultural development, pesticide use, climate change, fire, and fire suppression (https://www.iucnredlist.org).
Multiple studies have found that the American Bumble Bee has been experiencing disease and parasitism which may be factoring in their decline. Gillespe (2010) performed a study in Massachusetts and found that B. pensylvanicus and B. fervidus had higher levels of the parasite Nosema bombi than other common species. A similar study done by Cameron et al (2011) detected lower genetic diversity and higher levels of N. bombi in B. pensylvanicus compared to other stable, co-occurring species.
Pathogen spillover from commercial to wild bumble bees as explained in Colla et al. (2006) could contribute to disease spread in this species. This study found that bumble bees collected near commercial greenhouses were more commonly infected with C. bombi and N. bombi than the bees collected at other sites. Commercially reared species usually carry higher pathogen loads which can spill over into wild bumble bees when species come into contact while foraging.
The conversion of grassland habitats to commercial, residential, or agricultural lands is also a likely factor in the population decline of the American Bumble Bee and other bumble bee species. For instance, a study by Grixti et al. (2009) has correlated the increase in agricultural practices in the mid-1900s with the decline of B. pensylvanicus in Illinois. This species is said to be particularly vulnerable to habitat loss since it prefers nesting above ground (Hatfield et al. 2012).
Pesticides such as neonicotinoids also pose a threat to bumble bees like the American Bumble Bee. Neonicotinoids work differently than other pesticides because they are taken up by plant tissues including nectar and pollen that bumble bees consume. This poisons bees in small doses over time which can affect their ability to navigate, forage, and carry out basic tasks. (https://wisconsinbumblebees.entomology.wisc.edu).
| Threat 1 | Threat 2 | Threat 3 | |
|---|---|---|---|
| General Threat | Human intrusions & disturbance | Climate change & severe weather | Invasive & other problematic species, genes & diseases |
| Specific Threat | Work & other activities | Habitat shifting & alteration | Problematic species/diseases of unknown origin |
SNR - Unranked—Georgia conservation status not yet assessed.
Grassland habitats should be preserved and managed to mitigate the decline of this species. This should be executed by protecting grasslands from land conversion and using prescribed burning and other approved land management techniques. Reducing the use of pesticides in farmlands, fields, and urban areas would also help prevent further decline.
To slow disease spread in this species, commercial beekeepers could attempt to reduce pathogen spread in their colonies by proper cleaning and decontamination techniques. Culling infected individuals may also slow the spread.
About Bumble Bees. Xerces Society. n.d.. Retrieved from https://www.xerces.org/bumblebees/about.
Bombus pensylvanicus. Discover Life. n.d.. Retrieved from https://www.discoverlife.org/mp/20q?search=Bombus%2Bpensylvanicus.
Buchanan, S. (n.d.). Bumble Bees of the Eastern United States. US Forest Service. Retrieved May 13, 2022, from https://www.fs.fed.us/wildflowers/features/posters/EasternBumblebeesPoster_reduced.pdf
Bumble Bee FAQ. Bumble Bees of Wisconsin. (n.d.). Retrieved June 2, 2022, from https://wisconsinbumblebees.entomology.wisc.edu/bumble-bee-faq/
Cameron, S.A., Lozier, J.D., Strange, J.P, Koch, J.B., Cordes, N., Solter, L.F. and Griswold, T.L. 2011. Patterns of widespread decline in North American bumble bees. Proceedings of the National Academy of Science (USA) 108(2): 662-667.
Colla, S. R., Otterstatter, M. C., Gegear, R. J., & Thomson, J. D. 2006. Plight of the bumble bee: Pathogen spillover from commercial to wild populations. Biological Conservation, 129(4), 461–467. https://doi.org/10.1016/j.biocon.2005.11.013
Colla, Sheila & Richardson, Leif & Williams, Paul. 2011. Bumblebees of the eastern United States.
Gillespie, S. 2010. Factors affecting parasite prevalence among wild bumblebees. Ecological Entomology 35: 737-747.
Grixti, J.C., Wong, L.T., Cameron, S.A. and Favret, C. 2009. Decline of bumble bees (Bombus) in the North American Midwest. Biological Conservation 142: 75-84.
Hatfield, R., Jepsen, S., Mader, E., Black, S.H. and Shepherd, M. 2012. Conserving Bumble Bees. Guidelines for Creating and Managing Habitat for America's Declining Pollinators. The Xerces Society for Invertebrate Conservation., Portland, OR.
Hatfield, R., Jepsen, S., Thorp, R., Richardson, L., Colla, S. & Foltz Jordan, S. 2015. Bombus pensylvanicus. The IUCN Red List of Threatened Species 2015: e.T21215172A21215281. https://dx.doi.org/10.2305/IUCN.UK.2015-4.RLTS.T21215172A21215281.en.
Rourke, K. (n.d.). The American Bumble Bee (Bombus pensylvanicus). U.S. FOREST SERVICE. Retrieved May 13, 2022, from https://www.fs.fed.us/wildflowers/pollinators/pollinator-of-the-month/american-bumble-bee.shtml
Reagan Montalvo
6/7/2022
