Invertebrates
Bumblebee
Bombus terrestris · also called bumblebee, bumble bee
The bumblebee is the big, fuzzy, unhurried bee of gardens and meadows, and it is built for cold. It shivers its flight muscles to warm up, works flowers in rain and wind that keep honeybees indoors, and shakes pollen loose with a blast of vibration that greenhouse tomato growers pay for.
Overview
Bumblebees are mostly bees of the cooler Northern Hemisphere, with a few reaching the Arctic and high mountains and some native to South America. Queens of the larger species are about 2 cm long, rounded and densely furry in bands of black and yellow. Colonies are small and annual: a lone queen founds a nest, often in an old rodent burrow, and it grows to only 50–400 workers before producing next year’s queens.
Buzz pollination
A bumblebee can grip a flower and vibrate its flight muscles without beating its wings, shaking pollen out of flowers that lock it inside tight tubes — tomatoes, blueberries, cranberries, and many wildflowers. Honeybees cannot do this, which is why bumblebee colonies are sold to greenhouse growers.
Warm-blooded, for an insect
By shivering, a bumblebee raises its body temperature well above the air, letting it fly in cold, dull, wet weather and at dawn and dusk. That makes it the key pollinator in mountains and the far north.
A bee that solves puzzles
In experiments, bumblebees have learned to pull strings and roll balls to a target for a sugar reward, can copy the trick from other bees, and will roll balls even with no reward — which some researchers call play.
Status
Bumblebees overall are Least Concern, but the picture varies by species: habitat loss, pesticides, disease from managed bees, and climate change have driven sharp declines in many, and a few, like the rusty patched bumblebee, are now endangered.
Bumblebee: common questions
What is the difference between a bumblebee and a honeybee?
They are related but distinct. Bumblebees are larger, rounder, and much furrier, and their colonies are small, last only a single year, and are founded each spring by a lone queen. Honeybees are slimmer, live in colonies of tens of thousands that persist for years, store large quantities of honey, and swarm to reproduce. Bumblebees can perform buzz pollination and forage in cold or wet conditions that ground honeybees, but they do not communicate food locations with a dance and do not produce a surplus of honey worth harvesting. Both are important pollinators, and both include species in decline.
How does buzz pollination work?
Some flowers, including those of tomatoes, potatoes, blueberries, cranberries, and many wildflowers, keep their pollen inside narrow tubes in the anthers and release it only when shaken at the right frequency. A bumblebee lands on such a flower, curls around the anthers, grips them, and then contracts its flight muscles rapidly while keeping its wings still, producing an audible high-pitched buzz and a strong vibration. This shakes a cloud of pollen out onto the bee's body, some of which it grooms into its pollen baskets and some of which is carried to the next flower. Honeybees cannot do this, which is why commercial growers of greenhouse tomatoes buy bumblebee colonies.
Do bumblebees sting, and do they die if they sting you?
Female bumblebees, meaning queens and workers, can sting, and unlike honeybees they have a smooth stinger and can sting more than once without dying. Male bumblebees cannot sting at all. In practice bumblebees are very reluctant to sting and will usually only do so if grabbed or if their nest is seriously disturbed. A threatened bumblebee often rolls onto its back and raises a middle leg as a warning first. Stings are painful but for most people not dangerous unless they are allergic.
Why are bumblebees declining?
Several pressures acting together. Intensive agriculture has removed much of the flower-rich grassland and hedgerow that bumblebees feed in and the rough ground and old burrows they nest in, and it has left long gaps in the flowering season. Some pesticides, particularly neonicotinoids, impair bumblebee navigation, foraging, and colony growth even at low doses. Diseases have spread from commercially reared bumblebees and honeybees into wild populations. And climate change is shifting the timing of flowering and pushing cool-adapted species out of the warmer, southern parts of their ranges faster than they can expand northward.