Identification keys are given in Morgan (1984). General biology is given in Morgan (1984) and Falk (1991). The latter treats this species as a variety of C. ignita. However, C. ruddii is readily recognised by the small punctures on the second gastral tergite, relative to those on the first tergum, which are of uniform size and dispersion except at the rear of the tergum.
England,Wales, Scotland and the Isle of Man.
Overseas, it occurs in Europe (including Norway, Sweden, Finland, Denmark, The Netherlands, Belgium, Luxembourg, France, Germany, Switzerland, Italy, Poland, Hungary) and Asia Minor.