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Blue Mason Bee

Osmia caerulescens

Blue Mason Bee

A close up of a Blue Mason Bee Osmia Caerulescens on a flower

Solitary bee on scabious, Sandy, Bedfordshire (7615501134)

by Orangeaurochs. CC BY 2.0

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The blue mason bee, not to be confused with the blue orchard bee, is a small species of solitary bee. Like many mason bees, this species will use mud and chewed up petals and leaves to construct the walls of the nest. These tiny bees fall just under 1cm in length and are an iridescent blue under sunlight, displaying tones of blues, greens and turquoise when the light reflects from them. These small bees enjoy nectar from the smaller flowers, such as lavender, catmint and snapdragons, to name a few.
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Blue mason bees are attractive bees.
They may take bites from the petals of some flowers.


Adults: Osmia caerulescens are below 1cm, so it can be challenging to spot if you're not looking out for them. They can appear black but when the light shines on them, appear an iridescent blue, sometimes showing tones of greens and blues under sunlight. If you can get close enough, you may be able to spot the white leg-hairs. The pollen-collecting hairs beneath the abdomen are black.


These bees may bite into flower petals, however, in most cases they won't cause significant damage.











These bees are steadily distributed throughout the UK, although not too abundant. They're also found in South East Asia and Northern America.

Biological treatment

These bees are effective pollinators, bringing benefits to gardens. Encourage these bees to your garden by planting bee-friendly flowers, and they especially like plants that produce fruit crops!

Chemical treatment

It's not advised to treat gardens with bees. Plants which are in flower should not be sprayed if possible. Bees can be affected even if they weren't intended to be.


These bees enjoy the nectar of short-petaled flowers.


Antirrhinum spp.


Lavandula spp.

Red Clover

Trifolium pratense

Bird's Foot Trefoil

Lotus corniculatus

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