Bumblebees

How to recognise it

Round, densely furred and typically 10-25 mm long, banded in black with yellow, white, orange or red. Queens are conspicuously larger than workers of the same species, sometimes startlingly so. The colour bands are the basis of most field identification, and several species share the same pattern.

• Round and thickly furred, entirely unlike the slim banded honey bee.
• Pollen carried as a moist packed pellet on a bare, shiny hind-leg surface fringed with hairs — the corbicula, as in honey bees.
• The tail colour (white, buff, red) combined with the number and position of bands identifies most common species.
• Audibly loud in flight, and active in cool, dull and drizzly weather when honey bees stay in.

Body length 8–25 mm (typically 16 mm).

Biology

Social organisation

Eusocial, colony dies each autumn

A true colony with a queen and workers, but only for one season: everyone dies in autumn except mated new queens, who overwinter alone. Bumblebees.

Colony size at peak

50–400 individuals

Colony lifespan

One season. Founded by a single queen in spring and dead by autumn, with only newly mated queens surviving.

Winter

Mated new queens overwinter alone, usually a few centimetres down in loose soil or a north-facing bank, and emerge the following spring to start again. Every bumblebee colony in the world begins with one insect working alone.

Castes

Queen, Worker, Male

Nesting

Burrows in the ground; Existing cavities and tubes

Most species use an existing cavity rather than digging: abandoned rodent burrows above all, but also compost heaps, tussocks, bird boxes, cavity walls and the space under a shed. Nests hold a disorderly cluster of wax cells rather than an ordered comb.

Carries pollen

Corbicula (pollen basket) on the hind leg

On the wing

February to November

Queens of some species emerge remarkably early — buff-tailed bumblebee queens are regularly seen in February, and in mild urban areas some colonies now run through the winter on garden flowers.

Lifecycle

1. 1Overwintering queenA mated queen spends the winter dormant underground, living on fat reserves laid down the previous autumn.Six to nine months, depending on species and latitude.
2. 2Nest foundingShe emerges, feeds, finds a cavity, and builds a wax cup for nectar and a lump of pollen on which she lays her first eggs. She incubates them against her own body, shivering to keep them warm, and forages for them herself. This is the most precarious stage in the life cycle and most attempts fail.Several weeks in early spring.
3. 3Worker phaseThe first workers take over foraging and the queen stays in to lay. The colony grows through the summer.Roughly two to three months.
4. 4Reproductive phaseThe colony switches to producing males and new queens. They leave, mate, and the founding queen and all her workers die.Late summer into autumn.

Where it lives and what it does

Habitat

Grassland, moorland, mountain, woodland edge, farmland and gardens. Strongly associated with cool and temperate climates — bumblebee diversity peaks in mountains and at high latitudes, and they reach further north than any other bee.

Distribution

Throughout the temperate northern hemisphere, with species reaching the Arctic. Native to South America in the Andes, absent from most of Africa, and introduced to New Zealand, Tasmania and elsewhere for crop pollination.

Behaviour

Two capabilities matter most. Bumblebees generate their own heat by shivering flight muscles before take-off, which lets them fly at air temperatures near freezing and forage in rain and low light — several hours a day more than a honey bee, and months more each year. And they buzz-pollinate: gripping a flower and vibrating at a frequency that shakes pollen out of anthers that will not release it any other way. Tomatoes, aubergines, blueberries and cranberries all depend on this, and honey bees cannot do it at all. Individual bumblebees also learn flower handling, improving measurably at complex flowers over repeated visits.

Pollination role

Disproportionately important, and in several crops irreplaceable. Long tongues in some species reach nectar honey bees cannot; buzz pollination unlocks whole plant families; cold tolerance covers the early spring window when fruit trees flower and honey bees are still clustered. Commercial bumblebee colonies are now produced industrially for glasshouse tomato pollination, which is a straightforward admission that honey bees will not do the job.

Per visit, on the crops they suit, bumblebees frequently outperform honey bees by a wide margin.

What it forages on

Tongue length sorts the genus. Short-tongued species work open flowers and sometimes rob deep ones by biting a hole at the base; long-tongued species — the ones in steepest decline — depend on deep tubular flowers like red clover, foxglove and vetches, which is precisely the flora that disappeared from improved grassland.

Honey

Keeps only a few days of stores

Bumblebees do make honey, and the fact that most people confidently believe otherwise is a good example of how much 'bee' has come to mean 'honey bee'. They store ripened nectar in small wax pots near the nest entrance — enough for a few days of bad weather, never more, because an annual colony has no winter to provision for. There is nothing to harvest and it has never been a crop.

Relationship with people

How people interact with it

Not kept for honey and never have been. Reared commercially since the late 1980s for glasshouse crop pollination, in an industry now worth a great deal and carrying its own risks — commercially reared colonies have spread pathogens to wild populations, and escapees have established as invasive species in some regions.

Conservation

The genus is in well-documented decline across Europe and North America, and the pattern within it is instructive: long-tongued species dependent on flower-rich grassland have fared far worse than short-tongued generalists. Two British species have gone extinct nationally. The drivers are habitat loss, agricultural intensification, pesticides, pathogens and — for montane and northern species particularly — a warming climate that removes the cool conditions they are built for.