Colias viluiensis viluiensis Menetries, 1859
• RANGE . From Transbaikalia to the Chukot Peninsula.
• DISTRIBUTION AND VARIATION. The nominate subspecies (= chilkana Austaut, 1898) flies in the Amur region. The other known forms are: ssp. dahurica Austaut, 1899 - Transbaikalia; ssp. aquilonaris Grum-Grshimailo, 1899 - the Chukot Region, N. Siberia. Populations from the Far East probably represent a distinct subspecies.
•TAXONOMIC NOTES. The taxon aquilonaris may prove to deserve full specific rank but at present the material is too scarce to arrive at a final conclusion.
• HABITAT AND BIOLOGY. A resident of water-meadows and shrubby tundras. Flight period: June-July.
• SIMILAR SPECIES. C. hecia: UPS ground colour orange with dark border different. C. hyperborea: FW apex pointed; UPH base usually with an androconial spot.
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