A large Ectemnius resembling the common E. cavifrons but scarce in most areas. Formerly known under the names nigrifrons (Cresson, 1865) and planifrons (Thomson, 1870).

Historically the less common of our two Mellinus species and possibly now extinct in Britain. In M. crabroneus, the abdominal markings are ivory coloured and not yellow (as in M. arvensis)

Identification keys and hosts are given in Morgan (1984) and Archer (2003). Kunz (1994) treats this species as synonymous with C. ignita. Niehuis (2000) considers C. angustula to be a valid species consisting of two subspecies.

This wasp is an obligate social parasite of V. rufa in Europe and Asia. In North America its host is V. acadica. Called the 'cuckoo wasp', only queens and males are found since workers are not reared. See Spradbery (1973), Archer (1979, 1996b, 1997), Edwards (1980) and Else (1994) for keys and biology.

This species was previously included in the genus Astata.

This is probably not a native British mainland species.

Identification keys and general biology are given in Malyshev (1968), Richards (1980), Gauld & Bolton (1988), Falk (1991) and Yeo & Corbet (1995).

Identification keys and general biology are given in Richards (1980), Gauld & Bolton (1988) and Yeo & Corbet (1995). Females are wingless, but males are fully-winged.