Bumblebees are familiar insects in our gardens and backyards. Still, you might be surprised by how much you don't know about these important pollinators. The genus name, Bombus, comes from the Latin for booming.
Most people recognize the large, furry bees that visit backyard flowers as bumblebees. Fewer probably know that they are social bees, with a caste system of queen, workers, and reproductives cooperating to meet the needs of the colony.
Bumblebees range in size from about half an inch to a full inch in length. Patterns in their bands of yellow and black, along with the occasional red or orange, help indicate their species. However, bumblebees of the same species can vary quite a bit. Entomologists rely on other features, such as genitalia, to confirm a bumblebee's identity.
Cuckoo bumblebees, genus Psithyrus, resemble other bumblebees but lack the ability to gather pollen. Instead, these parasites invade Bombus nests and kill the queen. The Psithyrus bees then lay their eggs in the collected pollen in the conquered nest. This group is sometimes included as a subgenus of Bombus.
Bumblebees feed on pollen and nectar. These efficient pollinators forage on both wildflowers and crops. Adult females use modified hind legs equipped with corbicula to carry pollen to their offspring. Nectar is stored in the honey stomach, or crop, in the digestive system. Larvae receive meals of regurgitated nectar and pollen until they pupate.
Like other bees, bumblebees undergo a complete metamorphosis with four stages to the life cycle:
Egg – The queen lays eggs in a pollen clump. Then she or a worker bee incubates the eggs for four days.
Larva – The larvae feed on pollen stores, or on regurgitated nectar and pollen provided by the worker bees. In 10-14 days, they pupate.
Pupa – For two weeks, the pupae remain inside their silk cocoons. The queen incubates the pupae as she did her eggs.
Adult – Adults assume their roles as workers, male reproductives, or new queens.
Special Adaptations and Defenses:
Before flying, a bumblebee's flight muscles must be warmed to around 86 °F. Since most bumblebees live in climates where cool temperatures may occur, they cannot rely on the ambient warmth of the sun to achieve this. Instead, bumblebees shiver, vibrating the flight muscles at a high speed but keeping the wings still. The familiar buzz of the bumblebee comes not from the wings themselves, but from these vibrating muscles.
The bumblebee queen must also generate heat when she incubates her eggs. She shivers muscles in the thorax, then transfers the heat to her abdomen by contracting muscles down her body. The warmed abdomen stays in contact with the developing young as she sits on her nest.
Female bumblebees come equipped with stingers, and will defend themselves if threatened. Unlike their cousins the honey bees, bumblebees can sting and live to tell about it. The bumblebee's sting lacks barbs, so she can easily retrieve it from the flesh of her victim and attack again, if she chooses.
Good bumblebee habitat supplies adequate flowers for foraging, especially early in the season when the queen emerges and prepares her nest. Meadows, fields, parks, and gardens all provide food and shelter for bumblebees.
Members of the genus Bombus live mostly in temperate areas of the globe. Range maps show Bombus spp. throughout North and South America, Europe, Asia, and the Arctic. Some introduced species are also found in Australia and New Zealand.
- Bumble bees - The Great Sunflower Project (article no longer available online)
- Bombus Biology
- Bumblebees: Their Behavior and Ecology, by Dave Goulson