A mainly Holarctic genus that extends into southeast Asia and ranges to Australia. Due to extensive geographical variation and seasonal polyphenism, there is a good deal of disagreement among authors about the circumscription of species, particularly for the argiolus complex. Lamas (2004), for example, views all the North American species to be part of a Holarctic C. argiolus, while others restrict that name to the Palearctic populations. The names of narrowly-circumscribed taxa are listed here to inspire a phylogenetic analysis.