New Years Office Closure
Colorado Parks and Wildlife offices will be closed on January 1.
American Bumble Bee
This large bumble bee is a low-elevation species, staying between 3,315 to 7,000 feet.
About This Species
The American bumble bee has a vast range across much of the United States, but in the last two decades it’s estimated to have declined by nearly 90%.
More Information:
Physical Characteristics
The American bumble bee is one of the largest bumble bee species in North America. It has a fully black face and a band of yellow across the thorax in front of the wings (there is sometimes a band of yellow behind the wings). The first segment of the abdomen is typically half or all black; the second and third abdominal segments are typically yellow; and the fourth, fifth and sixth abdominal segments are typically black.
Range
As its name suggests, the American bumble bee has a large range across most of the United States. However, it is largely absent from much of the mountain West.
Habitat
The American bumble bee is primarily found in grassland habitats but can also be found in urban environments.
Diet
Like all bumble bees, the American bumble bee is a generalist, visiting a vast diversity of flowers, depending on what is available on the landscape. Astragalus flowers, Cirsium, Cornus, dalea flowers, Echinacea, Helianthus, Kallstoemia, Liatris, Mentzelia, Silphium, Solanum, Trifolium, and Vicia have been identified as key food sources.
Reproduction
The American bumble bee has a single annual cycle, which means it is born, matures, reproduces and dies within one year. Mated queens emerge in spring from their hibernacula, where they spend the winter. (It’s thought that queens dig shallow holes in the ground to hibernate in.) After waking from hibernation, the queen seeks a suitable nest site, typically an old rodent burrow or natural cavity. The queen lays the first generation of eggs, forages nectar and pollen for the offspring, and tends them to adulthood. This first generation of daughters take over the responsibilities of foraging and tending the next generation, leaving the queen to continue egg laying. After the first generation of daughters reach their adult stage, the queen never leaves the nest again. The colony grows throughout the season until the fall when males and the next generation of queens emerge. These queens forage to build up their fat reserves and mate before hibernation, preparing for the following spring. Once they find a suitable hibernation location, these queens settle down underground and enter diapause (insect hibernation) for the winter. They emerge in the spring and begin the cycle anew.
Threats to Species
Commercially managed bees (both bumble bees and European honey bees) pose a significant threat to native bumble bees. Managed bees can drive disease spillover, when a disease jumps from one population to another. Ongoing research demonstrates that honey bees can outcompete native bumble bees for resources and disrupt their natural foraging behavior. Pesticides also pose a threat to the American bumble bee with both lethal and nonlethal consequences. The bees can be exposed both directly through contact and indirectly through pollen, nectar and residual chemicals in the soil. Habitat loss is another major threat to the American bumble bee as they require healthy populations of flowers throughout the growing season and access to suitable nest sites. Finally, climate change poses a significant threat to the American bumble bee in many ways, affecting the bees directly and indirectly through the ways their habitats will change.
Additional Information
There are a number of ways you can support this species: 1) plant native flowers incorporating species that bloom across the entire growing season, 2) avoid the use of pesticides (both herbicides and insecticides), and 3) participate in community science projects like iNaturalist or the Bumble Bee Atlas to help expand our understanding of species distribution and abundance.
If you would like to help CPW understand and protect our state's bumble bees, you can participate in the Mountain States Bumble Bee Atlas. CPW is partnering with the Xerces Society for Invertebrate Conservation to get the Mountain States Atlas off the ground. Learn more here about how to get involved. If you are not able to participate in the Bumble Bee Atlas formally, you can submit photos of bumble bees you spot as one-off observations to the Bumble Bee Watch.