Blue orchard bee

How to recognise it

A stocky bee of roughly honey bee size with a metallic blue-black sheen through sparse pale hair. Females carry pollen dry on the underside of the abdomen. Males are smaller with a tuft of pale facial hair and longer antennae.

• Metallic blue-black body, quite unlike the gingery European red mason bee.
• Pollen carried on the underside of the abdomen, never on the legs.
• Seen carrying mud into tubes and holes in early spring, and gone by June.
• In North America, extremely abundant around managed nesting blocks in orchards.

Body length 8–14 mm (typically 11 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

Existing cavities and tubes; Hollow stems and plant cavities

Uses existing tubular cavities of 7-8 mm — beetle borings, hollow stems, and in managed systems drilled wooden blocks, paper straws and laminated trays that can be opened for cocoon harvesting. Cells are separated by mud partitions with a thicker plug at the entrance, and female eggs are laid at the back with males at the front.

Carries pollen

Scopa on the underside of the abdomen

On the wing

February to June

Lifecycle

1. 1Managed emergenceCocoons are overwintered at controlled temperature and warmed to time emergence precisely with bloom. Males emerge first and wait; females follow days later.February to April depending on the crop.
2. 2NestingA female works alone for four to six weeks, completing one or two cells a day, and dies before her offspring hatch.
3. 3Harvest and storageIn managed systems the completed cocoons are harvested in autumn, washed to remove pollen mites, candled or X-rayed for parasites, and stored cold until the following spring.

Where it lives and what it does

Habitat

Orchards, woodland edge, gardens and riparian scrub across North America.

Distribution

Western and eastern North America, with two subspecies broadly split between the Rockies.

Behaviour

Fast, low and clumsy inside a blossom, tumbling about rather than working it neatly — and that clumsiness is exactly why the pollination is so effective. Dry abdominal pollen sheds readily onto the next flower, and the bee moves between trees and varieties rather than working one methodically.

Pollination role

Outstanding on tree fruit — almond, apple, cherry, pear and plum. Per individual it moves several times more pollen than a honey bee, and it flies at temperatures and in light rain that ground honey bees entirely. Its commercial deployment in almonds is a direct response to the risk of a cold wet February.

Among the most effective tree-fruit pollinators known, per individual.

What it forages on

A generalist with a strong preference for spring tree blossom, particularly the rose family.

Honey

Produces no honey

None. One pollen loaf per cell, no colony and no winter to store for.

Relationship with people

How people interact with it

One of a small handful of genuinely managed bees, and the clearest North American example of a non-honey-bee pollinator being deployed commercially. Cocoons are bought, stored in a refrigerator and released to coincide with bloom, which is beekeeping in no recognisable sense.

Management

Managed by providing nesting blocks or tubes, harvesting cocoons in autumn, and cleaning them to control pollen mites and parasitic wasps. The cleaning step is what separates a sustainable population from a declining one, and it is the step hobbyists most often skip.

Conservation

Not threatened. The relevant concern runs the other way — dense managed populations and the movement of cocoons between regions are a plausible route for spreading parasites and pathogens into wild Osmia populations.