Colias Baeckeri

''Colias'' is a genus of butterflies in the family Pieridae. They are often called clouded yellows; the North American name "sulphurs" is elsewhere used for Coliadinae in general. The closest living relative is the genus '' Zerene'', which is sometimes included in ''Colias''.

This genus occurs throughout the Holarctic, including the arctic regions. They are also found in South America, Africa, China and India. Their caterpillars feed on certain Fabaceae, for example vetches (''Vicia''). While most are thus beneficial by keeping weeds at bay, some occasionally become nuisance pests on crops like alfalfa. In some species, the wings of males have brilliant ultraviolet reflection, while those of females do not. Adults of both sexes have various colour forms.

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.

Notable lepidopterologists who did many studies on this genus included Julius Röber, J. Malcolm Fawcett, George B. Johnson and Henry Rowland-Brown.

Systematics

Hybridization runs rampant in these polytypic and clinal butterflies, confounding molecular phylogenetics studies. In general, cladistic analyses of only one type of data (particularly mtDNA sequences) cannot be considered reliable. Regardless, the evolutionary distance within some "species" is so large that cryptic speciation rather than (or in addition to) interbreeding seems to be the cause. For example, the Beringian populations traditionally assigned to the northern clouded yellow (''C. hecla'') could warrant recognition as a species; hybridization between North American and Asian populations seems to have played a role in their evolution, but as a whole they appear to be a rather old and distinct lineage.

Species

Listed alphabetically:
* ''Colias adelaidae'' Verhulst, 1991
* ''Colias aegidii'' Verhulst, 1990
* ''Colias alfacariensis'' Ribbe, 1905 – Berger's clouded yellow
* ''Colias alexandra'' W. H. Edwards, 1863 – Queen Alexandra's sulphur, Alexandra sulfur, or ultraviolet sulfur
* '' Colias alpherakii'' Staudinger, 1882
* '' Colias aquilonaris'' Grum-Grshimailo, 1899
* ''Colias arida'' Alphéraky, 1889
* ''Colias audre'' (Hemming, 1933)
* ''Colias aurorina'' Herrich-Schäffer, 1850 – Greek clouded butterfly or dawn clouded yellow
* '' Colias baeckeri'' Kotzsch, 1930
* ''Colias behrii'' W. H. Edwards, 1866 – Behr's sulphur or Sierra green sulfur
* ''Colias berylla'' Fawcett, 1904 – Everest clouded yellow
* ''Colias canadensis'' Ferris, 1982 – Canada sulphur
* ''Colias caucasica'' Staudinger, 1871 – Balkan clouded yellow
* ''Colias chippewa'' W. H. Edwards, 1872 – heath sulphur
* ''Colias chlorocoma'' Christoph, 1888
* ''Colias christina'' W. H. Edwards, 1863 – Christina sulphur
* ''Colias christophi'' Grum-Grshimailo, 1885
* '' Colias chrysotheme'' (Esper, 1781) – lesser clouded yellow
* ''Colias cocandica'' Erschoff, 1874
* ''Colias croceus'' (Geoffroy, 1785) – dark clouded yellow or common clouded yellow
* '' Colias dimera'' Doubleday, 1847 – dimera sulphur
* ''Colias diva'' Grum-Grshimailo, 1891
* '' Colias dubia'' Fawcett, 1906 – dwarf clouded yellow
* ''Colias electo'' (Linnaeus, 1763) – African clouded yellow
* ''Colias elegans'' Schultz, 1904
* ''Colias elis