Bumble bees are not as aggressive as other types of bee, wasps, and hornets and rarely sting unless their nest is disturbed (Schweitzer et al. 2012).
There is a single record in New York since 2000 from Saratoga County and a few records from the 1990s (Richardson 2013 and Yanega 2013). There is evidence of a sharp decline in New York, both short-term and long-term (Richardson 2013 and Yanega 2013). In addition, this subgenus (Thoracobombus) has been shown to be significantly more infected by the pathogen Nosema bombi than bumble bees of other subgenera (Cameron et al. 2011).
Species in the subgenus Thoracobombus have declined 99-100% in most of the Northeast (Schweitzer and Sears 2013). The same is true for New York when comparing known post-2000 records to the number of records in the decade prior based on presence of B. pensylvanicus in proportion to the bumble bee populations in those years as a whole (data from Richardson 2013 and Yanega 2013).
Species in the subgenus Thoracobombus have declined 99% in NY when comparing known post-2000 records to the number of all records pre-2000 based on presence of B. pensylvanicus in proportion to the bumble bee populations in those years as a whole (data from Richardson 2013 and Yanega 2013).
The primary threat to species in the subgenus Thracobombus leading to their rapid, recent decline has been attributed to exotic pathogens. Cameron et al. (2011) showed a higher proportion of B. pensylvanicus individuals infected by the pathogen Nosema bombi than other bumble bees with stable global populations. In addition, habitat loss, insecticides, and urbanization are known long-term threats for many bumble bees (Schweitzer et al. 2012).
Any efforts to protect wild bumble bee populations from pathogen exposure would benefit American bumble bees. Suggested actions would include using mesh to prevent escape of bees from commercial breeding greenhouses, proper disposal of commercial bees, sanitation in greenhouses, and development of molecular screening. Tight restrictions on importing bumble bees and elimination of parasites from commercial populations has been suggested as ideal (Meeus et al. 2011, Schweitzer et al. 2012).
Limiting exposure of American bumble bee to insecticides would also benefit them. Suggested actions include avoidance of application to flowers that bumble bees are attracted to and application of solutions or soluble powders (rather than dusts or wettable powders) to the ground in calm wind and warmer tempertures during periods of dewless nights to minimize the impact to resident bumble bee populations (Schweitzer et al. 2012). Organic farming has also been suggested to benefit bumble bees.
Ensuring habitat resources for foraging, nesting, and overwintering will also benefit B. pensylvanicus. Habitats for these needs should be within close proximity to each other and without road or railroads between them, which may be barriers to dispersal. Suggested actions for habitat managment should include ensuring nectar availability throughout the spring and summer by improving flower abundance and species richness and species with overlapping blooms. Select food plants for B. pensylvanicus include vetches, clovers, goldenrods, Hypericum, and Eupatorium (Colla et al. 2011). If mowing of fields occurs, summer is the best time and mower blades should be raised to avoid ground nests. Staggering cutting times in different field areas will ensure nectaring sources are always available. Increasing available nesting habitat may be accomplished by reducing tillage in fields, leaving unplowed strips vegetated, or even providing artificial nesting boxes. Managing for rodents and ground-nesting birds should also benefit bumble bees (Schweitzer et al. 2012).
Further research is needed to determine more information on habitat requirements, threats, climate change effects, and insecticide effects for American bumble bee.
Bumble bees are generalist foragers and need nesting habitat in the spring, flowers for adult and larval nutrition throughout the spring and summer, and sites for queens to overwinter. Bumble bees that nest above ground such as this species often use long grass or hay stacks. Foraging habitat should include flower abundance and species richness with overlapping blooms to ensure nectar availability throughout the growing season (Schweitzer et al. 2012). Select food plants for B. pensylvanicus include vetches, clovers, goldenrods, Hypericum, and Eupatorium(Colla et al. 2011). Suitable sites for bumble bees to overwinter may include rotting logs, mulch, or loose soil (Schweitzer et al. 2012).
The American bumble bee has suffered rapid, recent declines in New York but was once common statewide (Colla et al. 2012). Its decline has been attributed mainly to exotic pathogens and insecticide use, but it also faces other threats (Schweitzer et al. 2012, Cameron et al. 2011). More inventories are needed to determine the full extent of its statewide range, as there is a single museum record from post-2000 in New York from Saratoga County.
Before 1998, American bumble bee was known from southern Quebec and Ontario west to South Dakota, south to Texas, California, and Mexico and east to Florida. Its more recent range appears to have contracted to a core range in the central U.S. (NatureServe 2015).
American bumble bee queens and workers have yellow hair on the front of the thorax and abdominal segments two and three and the rear edge of segment one. Other areas are black. Males have similar coloration to females, with the addition of yellow hair on the rear of the thorax and yellow on abdominal segments one through five (Colla et al. 2011, Evans 2009).
Bumble bee queens hibernate over the winter, emerge in the spring, locate a nest site, and rear young (workers, males, and new queens). After new queens and males mate, all males, workers, and old queens die by the beginning of winter and new queens settle into sites to overwinter (Schweitzer et al. 2012).
The time of year you would expect to find American Bumble Bee active and reproducing in New York.
American Bumble Bee
Bombus pensylvanicus (De Geer, 1773)
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Meeus, I., Brown, M.J.F., DeGraaf, D.C., and G. Smagghe. 2011. Effects of invasive parasites on bumble bee declines. Conservation Biology 25(4): 662-671.
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New York Natural Heritage Program. 2020. New York Natural Heritage Program Databases. Albany, NY.
Richardson, L. 2013. Compilation of specimen records for Bombus species of North America from the American Museum of Natural History, Harvard Museum of Comparative Zoology, among several other museums. Unpublished data.
Schweitzer, D. and N. Sears. May 1, 2013. Bumble bee ranking guidelines. NatureServe, Arlington, VA.
Schweitzer, D.F., N.A. Capuano, B.E. Young and S.R. Colla. 2012. Conservation and management of North American bumble bees. NatureServe, Arlington, Virginia, and USDA Forest Service, Washington, D.C. 17 pp.
Yanega, D. 2013. Compilation of specimen records for Bombus species of North America from the University of California Riverside Entomology Research Museum, the Essig Museum of Entomology, University of California Berkeley, the Natural History Museum of Los Angeles County and the California State Collection of Arthropods. Unpublished data.
This guide was authored by: Erin L. White
Information for this guide was last updated on: March 27, 2015
Please cite this page as:
New York Natural Heritage Program. 2020. Online Conservation Guide for Bombus pensylvanicus. Available from: https://guides.nynhp.org/american-bumble-bee/. Accessed December 3, 2020.