Habitat: Coastal areas, heaths (wherever the host Megachile maritima is found)
Species account: The cuckoo of Megachile maritima, and only to be found where this species is present. Females have a white coating of hair and the hair bands on tergites 2-5 are broadly interrupted. There are no erect setae on the face and there is a distinct ridge between the eyes. Males share the white hair and interrupted hair bands.
Similar species: The white hair and interrupted hair bands should allow separation from the other coelioxys species, but beware of old individuals where the hair bands may have worn off