Nick Baker’s hidden Britain
Red-tailed mason bee
Like some diminutive Harry Potter riding a broomstick, a small, fuzzy red bee came in low and heavy, dodging between grass and bramble, before crashing into a dark hole in the undergrowth. It appeared to be carrying a blade of grass several times longer than its body. This was my introduction to the wonderful world of Osmia bicolor, the red-tailed mason bee.
Of Britain’s 240 solitary bee species (the ones where each female makes a separate nest), the red-tailed mason is among the most endearing. It’s small and easy to miss, at just 12mm long, and looks superficially like many other solitary bees on the wing in spring. As both its scientific and common names suggest, it is a bee of two halves. Up front it is almost black, contrasting with the foxy red fur on its abdomen.
You can find this species
– and many other solitary bees – anywhere there is rough grassland studded with flowers, from the undisturbed corners of lawns to churchyards and verges. It is, however, restricted to the south.
In common with most solitary bees, the males emerge first, followed by the females a few weeks later. Once they’ve mated, a male’s short life ends, but, for a female, this is when the real work starts. Unlike other solitary bees, she doesn’t nest in the ground, dead wood or a wall. Instead, she is a helicophile (snail-loving) bee. This means she seeks out an empty snail shell – a rare choice of nest site in the bee world – which she ‘upcycles’ and puts to her own use.
When the female red-tailed mason finds a suitable shell, she shoves and tugs it into her preferred position with the entrance pointing down, then builds a nursery for her offspring inside. First, she constructs a series of brood cells (the number depends on the shell’s size). One at a time, she lays down a mastic of chewed-up plant material, lining the shell.
She stocks each cell with enough pollen-and-nectar mix to satisfy her future grub, before laying the egg and sealing it shut. Once she’s prepared all the cells, she creates a plug of coarse soil particles and stones, which she glues in place. Sometimes she’ll add a finishing flourish for camouflage – a dab of green mastic here or there on the outside of the shell. She may even partially bury the shell, if the soil is nice and soft.
This single mum still has the final, most impressive, touch to add to her nest. It is the most labour-intensive part of the whole operation, and the one that caught my eye in the first place. She starts to gather enough sticks and grass stems, and carries them, one at a time, to her snail-shell nest, where she proceeds to completely hide the shell under a loose thatch. I’ve watched a female making over 50 journeys, taking the best part of an hour. And to think she’ll stock several more snail shells in much the same way… it seems an exasperating amount of effort for such a small insect.
All going well, each brood of larvae will emerge, eat their provisions and pupate. In late summer or autumn, they hatch into adult bees, but stay sitting in their shell over winter, before chewing their way out this time next year, to start the process all over again.