Fairy bees

How to recognise it

Tiny, from under 2 mm to about 9 mm, and mostly hairless with a shining body often marked with cream or yellow on the face and thorax. Many are wasp-like in appearance, and Perdita minima is pale and so small it is routinely overlooked entirely.

• Extremely small — most under 5 mm, and the smallest under 2 mm.
• Sparsely haired and shining, often with cream or yellow markings.
• Found in the deserts and arid grasslands of North America and almost nowhere else.
• Usually seen on one specific plant genus, because most species will use nothing else.

Body length 1.8–9 mm (typically 4 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 sandy desert soil, often in aggregations, with cells provisioned with a firm pollen loaf. Perdita minima's cells are correspondingly minute, and the whole nest of a species this small is easy to walk over without noticing.

Carries pollen

Scopa — dense hairs on the hind leg

On the wing

March to September

The genus spans the season while any one species flies for only a few weeks.

Lifecycle

1. 1Emergence timed to one plantMost species emerge for a short window synchronised to the flowering of their host plant, which in a desert may itself depend on a particular rainfall event.Often only two to four weeks.
2. 2NestingThe female provisions cells alone with pollen from her host plant, working through her brief adult life.
3. 3DiapauseLarvae may remain dormant underground for more than one year, emerging only when conditions and host flowering coincide — a bet-hedging strategy that suits a landscape where rainfall fails for years at a time.

Where it lives and what it does

Habitat

Deserts, arid grassland, sand dunes and semi-arid scrub, overwhelmingly in North America.

Distribution

North America, with the greatest diversity in the southwestern United States and northern Mexico. Perdita minima is known from the Sonoran Desert of Arizona.

Behaviour

Rapid, tiny and almost impossible to follow. Most species are strict specialists provisioning cells with pollen from one plant genus, which makes the genus a striking illustration of how finely bee diversity can be partitioned — over 600 species dividing the flora of one arid region between them.

Pollination role

Effective pollinators of their specific host plants, several of which are visited by very little else. The very small body size limits how much pollen any individual carries, but a specialist visiting one plant repeatedly is efficient in the way that matters.

Moderate per individual and high on the specific host plants, several of which have few alternative pollinators.

What it forages on

Overwhelmingly oligolectic — most species provision cells with pollen from a single plant genus and will not substitute. Perdita minima is associated with small-flowered desert euphorbias.

Honey

Produces no honey

None. One tiny pollen loaf per cell, and no colony of any kind.

Relationship with people

How people interact with it

Effectively none, and that is the point worth making. A genus of over 600 species, including the smallest bee in the world, is almost entirely unknown outside specialist entomology — which is a reasonable illustration of how much bee diversity sits outside the handful of species anyone can name.

Conservation

Poorly known and structurally vulnerable. Specialists tied to one plant in an arid landscape have no buffer: lose the plant, or shift the rainfall pattern the plant depends on, and the bee goes with it. Very few Perdita species have any conservation assessment at all.