Horned mason bee

How to recognise it

Large for a mason bee, with a black head and thorax covered in dense black hair and a bright orange-red abdomen. Females carry two prominent horns on the face; males have a distinctive tuft of white facial hair.

• Sharply two-toned: black front, orange-red abdomen.
• Two visible horns on the female's face.
• Large — bigger than the red mason bee.
• Flies very early, from February in southern Europe, on fruit blossom.

Body length 11–16 mm (typically 14 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 cavities of 8-10 mm — beetle borings, hollow stems, wall crevices and managed nesting blocks. Cells are separated by mud partitions tamped into place with the facial horns, and sealed with a thick mud plug.

Carries pollen

Scopa on the underside of the abdomen

On the wing

February to June

Lifecycle

1. 1Very early emergenceMales emerge first, from February in southern Europe and March further north — among the earliest cavity-nesting bees.February to March.
2. 2NestingFemales provision cells for four to six weeks and die before their offspring hatch.
3. 3Managed overwinteringIn commercial use, cocoons are harvested, cleaned, screened for parasites and held cold to time emergence with blossom.Roughly ten months.

Where it lives and what it does

Habitat

Orchards, gardens, woodland edge, old walls and Mediterranean scrub.

Distribution

Central and southern Europe, North Africa and western Asia. Widely used in orchards in Spain, Italy and central Europe.

Behaviour

Fast, early and tolerant of cool weather, which is exactly what fruit blossoming in March requires. Like other mason bees it works blossom clumsily and moves between trees readily, which spreads pollen between varieties rather than around one.

Pollination role

An outstanding orchard pollinator, managed commercially for almond, apple, pear, cherry and plum across southern Europe. Per individual it moves several times more pollen than a honey bee.

Among the most effective fruit pollinators known, per individual.

What it forages on

Spring blossom, particularly the rose family and almond.

Honey

Produces no honey

None. One pollen loaf per cell, no colony.

Relationship with people

How people interact with it

One of a small number of genuinely managed solitary bees. Cocoons are bought, refrigerated and released to coincide with bloom — an industry that looks nothing like beekeeping.

Management

Managed with nesting blocks, autumn cocoon harvest, washing to control pollen mites, and cold storage to time emergence. Skipping the cleaning step is what turns a nesting block from a help into a parasite reservoir.

Conservation

Not threatened. The concern is the reverse: moving cocoons between regions is a plausible route for spreading parasites into wild Osmia populations.