Mason Bees

Above: Female Red Mason bee

Mason bees are so-called, because they use mud in the construction of their nests, however, it is actually the common substitute name used to describe bees belonging to the genus ‘Osmia’ which are part of the family ‘megachilidae’.

They are a solitary species and are non-aggressive, only stinging if provoked. They are a friend to gardeners and farmers, and may be used alongside honey bees for pollinating crops. Increasinlgly, as with bumblebees, they are being reared commercially.

The 'Red Mason Bee', Osmia bicornis (previously named Osmia rufa), is one of the most common of these species in Britain and Europe.

Examples of species found in the Americas include the 'Orchard Mason Bee', Osmia lignaria, and the 'Blueberry Bee', Osmia ribifloris.

Mason Bee Nests


are cavity nesting bees. They make their nests in existing cracks and crevices in walls, but they also favour hollow plant stems, but have even been known to make use of empty snail shells!

They may also take up residence in holes created by other wood-boring insects. They they are unlikely to cause any damage where their nests are made. Once a brood cell has been made, mud is used to make partitions between each individual cell. The female uses a pair of ‘horns’ on her face to pack mud to close the cell. Hence, they need a source of mud – perhaps at the edge of a pond, or puddle from where they can gather small pellets for their nest.

Below is a photograph taken of solitary bees in my garden in a msaon bee house I received as a gift - you can just see a red mason bee to the right, and below that, a further nest made out of hollow canes.

Life Cycle

Similar to the leafcutter bee life cycle, adults emerge in spring following a period of development and hibernation in a cell. Males appear first, waiting eagerly for sight of the females with which they will mate. After mating has taken place, the males will soon die. The female will seek a suitable location for her nest. She then constructs the nest, providing pollen and nectar in each cell for a single larva. Eggs destined to become females are laid toward the back of the nest, whilst males are laid toward the front. They will usually make between 4 and 6 cells, although sometimes as many as 10. Four or five similar nests may be completed in a season.

There will be one generation per year. The larvae develop and pupate, emerging as adults the following Spring.

Mason Bee Houses

Providing an excellent pollination service, these bees are great to have in the garden. To encourage them to set up a home, site bundles of hollow canes or a log drilled with holes (do not use chemicals on the log), in a south facing position.

Ensure the holes are around 1cm in diameter or a little less, and about 10cm long. Ideally, there will be a source of mud nearby, and plenty of opportunities for foraging. 

It is possible to purchase some very nice ready-made mason bee houses like this one above, which is available from

This one pictured left is available on

Mason Bee Guard Tubes and Inserts are also available.

For several years now, we have had the pleasure of watching these wonderful little pollinators establish nests around our garden, providing excellent entertainment!

Bee differences
Learn about some of the key differences between honey bees, solitary bees and bumblebees.

Types of Bees
Find out more about the types of bees, such as information about the different bee families.

Bee Plants
Take a look at these calendarized lists of plants for bees, including garden plants, herbs, wildflowers, shrubs and trees.

Bee Pollination
Find out how the different types of bees are important for pollination.

Bees Nests
Found a bees nest and not sure what to do? Take a look at this simple Q&A.

Save the bees!
Bees are having a hard time. Here are 10 top tips to help save the bees - share them with your friends!

An excellent source of information can be found on here.

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1 alfalfa leafcutter bee can do the pollination job of 20 honey bees!

Source: US Agricultural Research Service

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