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Mason Bee

Osmia spp.

Mason Bee, Masonry Bee, Mortar Bee

A close up of a mason bee from genus osmia emerging from a nest

Osmia cornifrons.5.1.08.w

by Beatriz Moisset. CC BY-SA 3.0

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Mason Bees get their common names after the materials they use to build their nests. They will use mud, or clay, to build nests for their young. The Latin name, Osmia, can be translated to the English word 'Odor'; and they are named this because they mark the nest entrances with a lemony scent. Each scent will differ ever so slightly so each female can quickly locate her own nest. These bees aren't social, but solitary; caring for broods alone. These bees are significantly docile, and the females will rarely sting. They can do substantial pollination, improving yields of veg, fruit and nut crops. Combined with their ease of transport, this makes them a popular bee for commercial growers all around the world.
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Professional garden pollinators visiting hundreds of flowers in a day.
Occasionally they'll nest in human-made structures.


Adults: The Mason Bees are a diverse genus containing bees that range from brown and black, to iridescent green and blue. They're never red or yellow striped, as seen in some solitary bees. Some possess bare, shiny abdomens, whereas others are highly furry. Additionally, some will have plumes of yed and yellow hairs on the face, too. They display an array of nesting behaviours, readily nesting in bee blocks and hotels. Some species prefer nesting in hollow stems whereas others will nest in human-made structures. They use clay-type soil to partition nest cells. They're slightly smaller than your average garden bumblebee. Larvae and Eggs: A female bee will lay an egg in each cell, with a little ball of pollen and nectar. When the eggs hatch they become bigger until ready to pupate, emerging as mature bees the following year.


Will nest in naturally occurring gaps in trees and plants. Sometimes, they'll nest in gaps of human-made structures. They are clumsy pollinators and may do a little damage to delicate flower types. They become covered in pollen in the process!












Biological treatment

These bees are effective pollinators, bringing benefits to gardens. Encourage these bees to your garden by planting bee-friendly flowers and fruits. These bees are solitary, so readily make use of insect and bee hotels. Likewise, they'll happily nest in things like wood blocks, too! Make sure you do your research on hotel placement and hygiene!

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.


Orchard owners and farmers have been known to have a good relationship with mason bees; they can pollinate a large number of flowers in just one day, so are bought commercially for this specific purpose.
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