Colias is a genus of butterflies in the familyPieridae. They are often called clouded yellows in the Palearctic and sulphurs (a name also used for other coliadine genera) in North America. The closest living relative is the genus Zerene,[4] which is sometimes included in Colias.
Most if not all species of this genus, as usual for Coliadinae, do not sequester toxins or other noxious compounds from their food plants. They are therefore a well-loved prey item of insectivores as compared to Pieris of the related Pierinae. They make up this disadvantage by being more nimble and better able to evade attacks by would-be predators.[7]
^Bjorn Petersen, 1963. The male genitalia of some Colias species.Journal of Research on the Lepidoptera 1: 135-156.[1]Archived 2017-06-03 at the Wayback Machine
^Lucien A Berger, 1986 Systématique du genre Colias F: Lepidoptera-Pieridae Bruxelles: Imprimerie des Sciences, 1986.