Oil-collecting bees

How to recognise it

Small to medium black bees, around 8-10 mm, with pale hair bands and — in the females — conspicuously dense, specialised hair pads on the front and middle legs used to mop up floral oil. Males have pale facial markings.

• Found on yellow loosestrife and essentially nowhere else during the flight period.
• Females with dense oil-collecting hair pads on the front and middle legs.
• Small black bees with neat pale abdominal bands, flying June to August.
• Nests in damp ground close to the host plant, which no other bee does.

Body length 7–11 mm (typically 9 mm).

Biology

Social organisation

Solitary

Each female builds and provisions her own nest with no workers and no caste. Most of the world's bee species.

Nesting

Burrows in the ground

Digs burrows in damp, often almost waterlogged ground close to stands of the host plant — which is only possible because the cells are lined with the floral oil the bee collects. The oil waterproofs the cell in exactly the way a Colletes bee's cellophane secretion does, from a completely different source.

Carries pollen

Scopa — dense hairs on the hind leg

On the wing

June to August

Lifecycle

1. 1EmergenceAdults emerge in early summer, timed precisely to the flowering of yellow loosestrife.June to July.
2. 2Oil and pollen collectionThe female visits loosestrife flowers, mops floral oil from glandular hairs using specialised leg pads, and mixes it with pollen to form the larval provision. She also uses it to line the cell.
3. 3OverwinteringThe larva develops on the oil-and-pollen provision and overwinters underground, emerging the following summer.Roughly ten to eleven months.

Where it lives and what it does

Habitat

Wet ground with stands of yellow loosestrife — fen, marsh, ditch margins, pond edges and damp woodland rides.

Distribution

Europe, temperate Asia and North America, always tracking the distribution of Lysimachia.

Behaviour

Fast and highly localised. A Macropis population exists as a small satellite of a loosestrife stand, and the bee is essentially never found away from it. Its cuckoo, the Epeoloides bee, is one of the rarest bees in Europe and North America precisely because it depends on a specialist that depends on one plant.

Pollination role

The primary pollinator of yellow loosestrife, which offers oil rather than nectar and is therefore visited by very little else. Beyond that its pollination contribution is minor — this is a tightly specialised relationship rather than a broad one.

High on its host plant and essentially zero elsewhere — the definition of an obligate specialist.

What it forages on

Obligately dependent on Lysimachia — yellow loosestrife and its relatives — for the floral oil that provisions the cells. It takes nectar from other plants for its own fuel, but cannot reproduce without loosestrife.

Honey

Produces no honey

None, and the provision is not even the usual pollen-and-nectar mixture — it is pollen mixed with plant oil, which is a genuinely different larval food from anything else in the catalogue.

Relationship with people

How people interact with it

Almost entirely unknown outside entomology, and important out of proportion to its profile. The Melittidae sit near the base of the bee family tree, and oil collecting is thought to be an ancient trait — which makes this small group a window onto what early bees may have been doing.

Conservation

Localised and declining with the drainage of wet ground and the loss of yellow loosestrife. Its own cleptoparasite, Epeoloides coecutiens, is among the rarest bees in Europe and was believed extinct in Britain — a specialist on a specialist on one plant is about as fragile as an ecological relationship gets.