Quite excited about this spot in the garden today.
Found in a wide variety of open habitats: woodland and shrubland, lowland heaths, chalk quarries, coastal cliffs, gardens and cemeteries. Often found flying around the nest sites of its hosts: mud, walls, holes in mortar, dead wood, old wooden posts, and snail shells.
Univoltine. Males are found during May and June, and rarely in July. Females occur mainly during June, often during May and July, or more rarely in April and August.
Cleptoparasitic on bees of the genus Osmia (O. bicornis (Linnaeus), O. leaiana (Kirby) and O. aurulenta (Panzer), O. caerulescens
The female enters the nest of the host and lays an egg on or near the egg of the host. Gauld and Bolton (1988) indicate that the sting is used to penetrate the cell wall, thus acting as an ovipositor. P Westrich (pers.com., 1999) says that the egg is placed directly in the cell. On hatching, the first instar larva, which has large mandibles, eats the egg of the host. Later instars have smaller mandibles and feed on the stored food of the host