Summer unit nesters

L-R Orange-vented mason bee (Osmia leaianna) and Common yellow-face bee (Hylaeus communis)

We had 2 bees nesting in the summer unit bee observation box which we put up in the garden for the first time this year.

One is an Orange-vented mason bee (Osmia leaianna) who we confused for a Blue mason bee (Osmia caerulescens) . They are a similar size (8mm) and both carry pollen on the underside of their abdomen. They could both be confused for a leafcutter bee, but they divide their birthing cells and plug the entrance of their nest with chewed up leaf, whereas the leafcutter uses whole pieces of leaf. The easiest way to tell the Orange-vented and Blue mason bee apart is to observe the colour of their pollen brushes after the pollen has been deposited. You’ll see that Orange-vented mason bees have orange pollen brushes and Blue mason bees’ pollen brushes are black.

Watch some amazing footage of her in action

The other nester is a much smaller bee, the 5mm Common yellow-face bee (Hylaeus communis) – black apart from yellow marking on her face and legs. She nested in the cavity with a smaller entrance hole underneath the mason bee.

It’s amazing to be able to see 2 very different species of bee creating nests in very different ways. You won’t see pollen on the hind legs or under the tummy of a yellow-face bee because, unusually, they carry pollen back to the nest in a special stomach, called a crop and regurgitate it to make a semi-liquid mixed with nectar to feed their brood (larvae).

Left – Top right: pollen-packed cells of the Orange-vented mason bee; Middle: Orange-vented mason bee Bottom: Common yellow-face bee creating cellophane-like bags and depositing nectar and pollen and an egg in each waterproof cell.

Right: Top right: second row of eggs and pollen created by the Orange-vented mason bee Middle: Eggs have hatched into larvae in some of the Common yellow-face bee cells and she is making more cells

Orange-vented larvae developing ,

Our Orange-vented mason bee used three cavities and the Yellow face-bee one before unprecedented heat hit our garden and the adult bees disappeared. Hopefully, they had finished their work and died naturally. The summer unit was in full sun, so we’re not sure if the brood has survived or was cooked alive!

We will keep an eye on them to see if they develop further by spinning a cocoon and pupating over winter.

These summer units can be purchased from a variety of suppliers. We got ours from George Pilkington at Nurturing Nature They really do open up a hitherto hidden world.

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