Vestal cuckoo bumblebee

How to recognise it

Superficially like a buff-tailed bumblebee, with a yellow collar and a white tail, and distinguished by two consistent features: darker smoky wings, and hind legs that are hairy all over rather than carrying a bare shiny pollen basket. Yellow patches flank the white tail.

• No pollen baskets — the hind leg is hairy all over rather than bare and concave. This is diagnostic.
• Darker, smokier wings than the host.
• Sparser hair over a visibly harder, shinier abdomen.
• Emerges several weeks after buff-tailed queens, which is essential to its strategy.

Body length 15–22 mm (typically 18 mm).

Biology

Social organisation

Cleptoparasitic — lays in other bees' nests

Builds no nest and gathers no pollen for her own young, laying instead in another bee's provisioned cell. Sometimes called cuckoo bees.

Nesting

Builds no nest

Builds nothing. The female locates a buff-tailed bumblebee colony by scent, enters it, and takes it over — killing the host queen in most cases. She has no worker caste of her own and produces only males and new females, so the host colony rears her reproductives and none of its own.

Carries pollen

Carries no pollen for young

On the wing

March to September

Lifecycle

1. 1Late emergenceFemales emerge from hibernation several weeks after their hosts, which is essential — the host colony must already have a workforce before invasion is worthwhile.April to May.
2. 2InvasionShe enters a host nest and takes it over, surviving attack by host workers. Her cuticle is markedly thicker and her sting stronger than a true bumblebee's for exactly this reason.
3. 3Brood rearing by proxyHost workers rear her offspring. She produces only reproductives, so the host colony's own reproduction ends.

Where it lives and what it does

Habitat

Wherever buff-tailed bumblebees nest — gardens, farmland, hedgerow, woodland edge and urban parks.

Distribution

Across Europe and into North Africa and western Asia, following its host.

Behaviour

Slow, heavy and unhurried in flight, with no brood to provision and nowhere in particular to be. Females are often seen flying low and searching over ground where host colonies are likely.

Pollination role

Modest. It visits flowers only for its own fuel and carries no pollen deliberately. Its significance is as an indicator of a large and stable host population.

Incidental only.

What it forages on

Visits flowers for its own nectar and is unfussy about which.

Honey

Produces no honey

None. No nest, no colony of its own, no stores.

Relationship with people

How people interact with it

Routinely misidentified as an ordinary bumblebee and otherwise unknown. There is no pest relationship — a cuckoo bumblebee in a garden indicates enough bumblebees to sustain a parasite.

Conservation

Common and stable in southern Britain, in step with its abundant host. Cuckoo bumblebees generally decline faster than their hosts, and this species is an exception because the buff-tailed bumblebee is thriving.