Great yellow bumblebee

How to recognise it

A large bumblebee covered in even straw-yellow hair, with a single black band between the wing bases. There is no white tail, no red tail and no second yellow band — the uniformity is what makes it recognisable.

• Uniformly pale straw-yellow all over, with one black band across the thorax.
• Large — queens can exceed 20 mm.
• Restricted range: in Britain, essentially the Hebrides, Orkney, Caithness and Sutherland.
• Long-tongued, and seen feeding head-first on red clover, knapweed and vetches.

Body length 13–22 mm (typically 18 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

30–120 individuals

Colony lifespan

One short season, starting late.

Winter

Mated new queens overwinter alone in the ground.

Castes

Queen, Workers, Males, New queens

Nesting

Burrows in the ground

Nests underground in old rodent burrows, often in machair grassland and dune systems. It emerges late — often not until late May — which compresses the whole colony cycle into a short northern summer.

Carries pollen

Corbicula (pollen basket) on the hind leg

On the wing

May to September

Lifecycle

1. 1Late emergenceQueens emerge in late May or June, considerably later than most bumblebees, and have a short season in which to found a colony.Late May to June.
2. 2Short colony seasonA small colony builds through the northern summer and produces reproductives in August.
3. 3Reproduction and hibernationNew queens mate in late summer and hibernate; the colony dies.

Where it lives and what it does

Habitat

Machair — the flower-rich shell-sand grassland of the Hebrides — plus dunes, crofting land and unimproved hay meadow. It needs abundant legumes and a long uninterrupted flowering season.

Distribution

Formerly across much of Britain and Ireland, and now restricted to the Outer Hebrides, Orkney, the north Scottish mainland and a few Irish coastal sites. Still present across parts of northern Europe and Asia.

Behaviour

A slow, heavy flier that works legumes methodically. Its long tongue lets it feed properly from red clover and vetches, and its dependence on those plants is precisely why it has gone from everywhere they have.

Pollination role

An important pollinator of legumes in the machair crofting system, where traditional low-intensity rotation still produces the flower-rich swards it needs.

High on legumes, and now confined to too small an area to matter at national scale — which is itself the point.

What it forages on

A legume specialist in practice — red clover, vetches, bird's-foot trefoil and knapweed. Its narrow diet is a large part of its vulnerability.

Honey

Keeps only a few days of stores

A few days' worth in wax pots.

Relationship with people

How people interact with it

Its survival depends directly on crofting. Machair is a cultural landscape — created and maintained by low-intensity rotational cultivation with seaweed fertiliser — and the bee persists because that farming system does. It is one of the clearest cases anywhere of a species depending on the continuation of a traditional agricultural practice.

Conservation

A UK priority species and one of the most threatened bumblebees in northwest Europe. The cause is well understood: the loss of flower-rich hay meadow and of red clover from farming systems, following nitrogen fertiliser and silage. Where machair crofting persists, so does the bee.