May 2023

THE RED MASON BEE

These bees belong to a large group collectively known as solitary bees. Unlike honey bees and Bumblebees, solitary bees don’t nest communally, neither do they have workers or queens. Each female solitary bee hatches, mates, creates her own nest and lays her eggs, all in one season. She then dies, leaving the next generation to overwinter as pupae or adults in their individual cells before emerging the following spring. Another difference is that rather than having pollen baskets on their legs, social bees collect pollen using an array of specially modified hairs called scopae, either on their legs or abdomen.

There are about 250 species of solitary bees in the UK, but one of the most common is the Red Mason Bee. These are the species most often attracted to insect hotels because unlike mining bees, they prefer to use pre-existing cavities, rather than excavate their own. They will utilize hollow plant stems, beetle borings in dead wood, cavities in crumbling masonry etc. Within this space they create a number of cells, each containing one egg, supplied with nectar and pollen to feed the larvae once they hatch. Each nest will contain about 6 to 8 chambers depending on the depth of the cavity. Having provisioned the cell and laid an egg, the female builds a partition wall using different materials according to the species: Leaves, fine hairs, or in the case of the Red Mason Bee, mud. The photo shows a female mason bee collecting mud in her mandibles. 

That brings me onto something we observed in the Rec a couple of weeks ago. A fox, or dog had dug a small hole in the ground on the edge of one of the flower beds and the exposed sides were like a mini crumbling, cliff face. We were about to fill it in when we noticed a number of bees flying to and from the site. They appeared to be burrowing into the mud walls, and initially I thought they were mining bees excavating their nests. Subsequently I found out that these bees usually create vertical tunnels in the ground with side chambers leading off. There is also, as a rule, a small pile of the excavated material around the opening. Having dismissed that theory, I went on to identify the bees in the photos as female Red Mason bees, and again assumed they were nesting. Although they don’t form colonies, they often nest in very close proximity to one another. But studying the photos more closely, I think they were actually using the exposed, soft mud as a source material to take back to their nests. 

The Red Mason Bee gets its name from the gingery hairs covering the body of both males and females (although the colour does fade with age and wear). The males are smaller and more slender, and have a dense tuft of white hair on the front of their heads. Their only role is to mate with as many females as possible. The female has a larger, black head which is more square in shape. It carries the substantial muscles needed to operate the powerful jaws used for excavating mud. The female also has inward curved ‘horns’ on the top of her head, as well as the antennae, and this isn’t seen in any other British species. Pollen collected on the scopae beneath her abdomen, known as a pollen brush, can be seen from above as brightly fringing it.

I suspect these bees may be nesting in our bug hotel. But don’t worry, they are pretty harmless, and the females, will only give a mild sting if very severely provoked. So take a good look next time you’re in the Rec and you may see these amazing, industrious creatures flying back and forth with mouthfuls of glorious mud!

Words and Photographs by Denise Long

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