Blue Mason Bee - Osmia caerulescens

Length 8 to 10 mm. The females have large box-shaped heads and a blue metallic lustre to the abdomen giving rise to its common name, with a black pollen basket on the hind legs. The males are bronze with pale yellow hairs and a shining slope at the front of the abdomen.

Males , Females

Forest edges and clearings, flower meadows, orchards, parks and gardens.

April to August/September.

Nests in holes, often existing cavities in dead wood and plant stems, rocks and mud walls. The female deposits her egg, adds food for the larvae, builds a small wall out of chewed leaves and creates the next chamber, where she will deposit the next egg.

Widespread in England and Wales but more common in the South.

Occasional in Leicestershire and Rutland.