Photo: Pjt56 / CC BY-SA 4.0

Osmia bicornis

Red Mason Bee

One of the most familiar and widespread solitary bees in Europe, the Red Mason Bee was voted Insect of the Year 2019 for Germany, Austria, and Switzerland. Females (10–12 mm) have a robust black body with a metallic blue-green shimmer, a greyish-brown hair pile on the thorax, and an orange-red-haired abdomen. Males are similar but smaller with longer antennae and abundant whitish-yellow facial hairs. Both sexes have two distinctive inwardly curved horns on the clypeus. It is a cavity nester of astonishing flexibility, occupying pre-existing holes in dead wood, hollow stems, old walls, soft mortar joints, bee hotels, and even door locks and curtain rails. Cell partitions and nest plugs are constructed from moist mud. It is broadly polyleptic, visiting flowers from 19 plant families, making it a valuable orchard pollinator, especially for almonds and cherries. In Switzerland it is very common in gardens, parks, and settlements across the lowlands and montane regions, and is classified as Least Concern on the national Red List.