Alkali bee

How to recognise it

A medium-sized bee of about honey bee size, dark with striking iridescent bands across the abdomen that shift between green, blue and yellow depending on the light. The metallic banding is unlike anything else in North America at that size.

• Iridescent green-blue abdominal bands that change colour with the viewing angle.
• Roughly honey bee size but with a flatter, more banded appearance.
• Found in vast aggregations on flat salt-crusted alkaline soil, often adjoining alfalfa seed fields.
• Restricted to western North America.

Body length 10–14 mm (typically 12 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

Nests in flat, bare, alkaline soil with a specific and narrow requirement: subsurface moisture wicking up through a dry salt-crusted surface. Females dig burrows 15-30 cm deep and nest in enormous aggregations — a single managed bed can hold millions of nests. The moisture requirement is what makes the beds engineerable: growers lay gravel and salt over a buried irrigation system to reproduce the conditions deliberately.

Carries pollen

Scopa — dense hairs on the hind leg

On the wing

June to August

Lifecycle

1. 1EmergenceAdults emerge from the beds in early summer, timed to alfalfa bloom, in numbers dense enough that the ground appears to move.June to July.
2. 2NestingFemales dig and provision cells alone in the shared bed, working through the alfalfa flowering.Six to eight weeks.
3. 3OverwinteringLarvae develop and overwinter underground as prepupae, emerging the following summer.Roughly ten months.

Where it lives and what it does

Habitat

Alkaline flats, playas and salt-crusted soils in the arid American west, and the artificial beds built to imitate them.

Distribution

Western North America, from the Great Basin north into Washington, Oregon, Idaho and Utah.

Behaviour

Fast-flying, tolerant of extreme heat, and — decisively for agriculture — willing to trip alfalfa flowers rather than robbing them from the side. Like the leafcutter bee, its economic value rests on a behavioural tolerance the honey bee lacks.

Pollination role

One of the most effective alfalfa pollinators known, and in the Walla Walla valley it underpins some of the highest alfalfa seed yields in the world. Its per-visit pollination rate on alfalfa exceeds the honey bee's by a wide margin because it opens the flower properly.

Very high on alfalfa specifically, which is what it is managed for.

What it forages on

A generalist that strongly favours legumes, and alfalfa above all.

Honey

Produces no honey

None. Solitary, one provision per cell, no colony.

Relationship with people

How people interact with it

Unique. Alkali bee management is habitat engineering rather than husbandry: growers construct, salt and sub-irrigate nesting beds and then protect them, sometimes for decades, treating the bed as permanent capital. Washington State even reroutes traffic and posts signs around the beds, because vehicle strikes on foraging females are a measurable cause of loss.

Management

Beds are built by laying a buried irrigation line under gravel and salt to maintain subsurface moisture with a dry crust above. They take years to build up a population and can be destroyed in one season by insecticide drift, flooding or the wrong tillage. Growers coordinate spray timing across whole valleys to protect them.

Conservation

Locally abundant where beds are maintained and dependent on a habitat type — natural alkaline flats — that is limited and easily lost to development, cultivation and altered hydrology. It is a species whose fortunes are almost entirely in the hands of a small number of farmers.