Over all length 8 - 10mm. The male is black with creamy-white markings on its abdomen. The female is similar but the second and third segments of the abdomen are red.
A wide range of habitats are used, where ever its hosts, Osmia bees, can be found. It lays an egg in its hosts egg chamber and the larva eats the host's egg and then its food store.
Status and distribution
Fairly common and widespread in southern Britian, rare further north. Fairly common in Nottinghamshire and recorded once at Netherfield Lagoons.
Best time to see
May to July.