Bumble bees (Bombus spp.) are critical pollinators of both food crops and wild plants. Active from spring through fall, these large native bees can fly long distances and are able to forage in cool, wet temperatures by shivering their thoracic flight muscles to generate heat. Bumble bees are also known for their ability to “buzz pollinate”—a behavior in which vibration of the flight muscles at a specific frequency facilitates pollination of certain plants.
Over one fourth of North America’s 46 bumble bee species are threatened with extinction, including at least four species in Iowa, most notably the rusty-patched bumble bee (B. affinis), a federally endangered bee that has been lost from most of its range across northeastern North America, but still occurs in Iowa in low numbers.