One of the more common large Ectemnius species easily identified in both sexes by the densely striate mesoscutum with transverse striae on the front half.

The distribution of this species is significantly different from that published by Richards (1980), due to the separation in Britain of two species, T. nitidus and T. unicolor from the one taxon previously recognised as T. unicolor.

There is considerable confusion regarding the correct use of this name. As interpreted here this is the scarcer species of the two, apparently restricted to IOW and Dorset.

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).

A medium-sized species of Ectemnius.

One of the smaller Ectemnius species, resembling a small E. continuus, but much less frequent.

A large Ectemnius closely resembling the common E. continuus, but considerably scarcer. Formerly known under the names zonatus (Panzer, 1797), saundersi (Perkins, R.C.L., 1899) and quadricinctus (misidentification). The last name was also shared with E. cephalotes, making some old records impossible to assign.

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.