Blue Mason Bee Osmia caerulescens
Mason Bees nest in small holes in wood, e.g. unused beetleholes in trunks, hollow stems etc. The female deposits her egg, adds food for the larvae, builds a small wall and creates the next chamber, where she will deposit the next egg. The Blue Mason Bee is quite common. However it never appears in great numbers and is on the wing later than the Red Mason Bee. By then there are plenty pollinators around, so the Blue Mason Bee is less useful in agriculture.