Identification keys and general biology are given in Morgan (1984) and Falk (1991). Previously known as C. helleni Linsenmaier, 1959. Kunz (1994) considers C. bicolor Lepeletier, 1805 and C. illigeri to be the same species. Morgan (1984) separates these two names, with C. bicolor only known from Jersey.
Cornwall to Kent, and north to Leicestershire and West Norfolk. (Morgan (1984) also gives Nottinghamshire, but no data are available). Jersey.
Overseas, the wasp occurs in Europe (including Norway, Sweden, Finland, The Netherlands, Belgium, Luxembourg, France, Switzerland, Italy, Poland, Austria and Hungary).