Metallic green sweat bee

How to recognise it

Small to medium, from 7 to 14 mm, with a brilliant metallic green or blue-green head and thorax. Females are metallic throughout; males in many species carry a yellow-and-black banded abdomen that looks wasp-like.

• Brilliant metallic green — no North American bee of similar size is more conspicuous.
• Males often with yellow-and-black striped abdomens against a green thorax.
• Ground-nesting, frequently in aggregations on bare sunny soil.
• Unlike many sweat bees, several species are not strongly attracted to perspiration.

Body length 7–14 mm (typically 10 mm).

Biology

Social organisation

Communal — shared entrance, separate cells

Several females share a nest entrance but each provisions her own cells. Cooperation over the door, not over the brood.

Nesting

Burrows in the ground

Digs burrows in bare or sparsely vegetated soil, often in aggregations. Several species are communal — many females share a single entrance and burrow system while each provisions her own cells, and in some cases a female guards the shared entrance while others forage.

Carries pollen

Scopa — dense hairs on the hind leg

On the wing

March to October

Lifecycle

1. 1EmergenceOverwintered mated females emerge in spring and dig or reoccupy burrows.March to May.
2. 2Communal nestingSeveral females may share one entrance, each maintaining separate cells. Guarding behaviour at the shared entrance is a step towards sociality without a caste system.
3. 3ReproductionMales and new females produced through summer; mated females overwinter.

Where it lives and what it does

Habitat

Prairie, meadow, gardens, farmland, roadsides and desert across the Americas.

Distribution

North, Central and South America, from Canada to Argentina.

Behaviour

Fast, conspicuous and generalist. The communal nesting is the point of scientific interest: shared entrances with independent provisioning sit between true solitary living and eusociality, and the guarding behaviour shows cooperation emerging without a queen.

Pollination role

Important generalist pollinators across the Americas, particularly of prairie flora and of small-flowered crops. Their abundance makes them collectively significant.

High in aggregate through abundance and season length.

What it forages on

Broad generalists, favouring composites and open flowers.

Honey

Produces no honey

None. Communal at most, with provisions sized per cell and no colony to overwinter.

Relationship with people

How people interact with it

Frequently photographed and rarely identified. Their brilliance makes them one of the better gateway species for anyone starting to notice bees other than honey bees.

Conservation

Widespread and not threatened as a genus. Like all ground-nesting bees they depend on bare sunny soil, which paving, dense turf and landscape fabric remove.