You are probably aware of bug hotels with drilled wooden blocks and bee nesting tubes with bamboo bundles or narrow cardboard tubes, but what uses them?
There are several bee species – mason bees (genus Osmia), leaf-cutter bees (genus Megachile) and a few others, but the commonest is the Red Mason Bee (Osmia bicornis) which is active in spring, and is the one that tube manufacturers mention. If you’ve seen the nest tube on the small tool shed recently, it’s been very busy with bees coming and going. It can look like a small swarm but they are solitary (close neighbours rather than a hive) and they don’t sting. So, what are they doing?
Unlike social species like honey bees, each mason bee has its nest in a single tube. The female produces cells in a line, like a tube of sweets, using mud or other materials to build partitions and then seal the entrance. She even has little blunt horns to tamp the mud in place and sometimes you can see the marks these leave when the mud dried. In the absence of artificial nests (preferably south-facing, approx 1-2m above the ground), they use existing holes, and may expand them, including in soft mortar which hasn’t always been popular with householders; however, modern mortar is harder, hence the need for tubes – just like bird boxes. There are a few Osmia species that use empty snail shells instead, sealing up the entrance in just the same way.
Like many insects, they are useful pollinators, especially of fruit trees and can even be bought commercially for this purpose. So, enjoy them, thank them for helping grow fruit, and don’t worry when walking past them, however much they are buzzing about!
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