Diagnosis: This is an extremely variable species that can generally be described as looking intermediate between the Hecla Sulphur (C. hecla) and the Labrador Sulphur (C. nastes). The wings have a narrow irregular dark border, with the ground colour either orange tinged with green (subspecies boothii) or pale green (subspecies thula). The female is heavily dusted with dark scales and has a wide forewing border with large yellow spots. The underside is greenish yellow with heavy dark scaling. The white spot in the centre of the hindwing has a red rim, which is extended as a streak towards the wing edge. Wingspan: 28 to 43 mm.
Subspecies: The nominate subspecies, described from Lake Baikal, Russia, occurs through northern Eurasia. Subspecies thula is pale green; it occurs in northern Alaska and in Canada on Banks, Victoria, and Melville Islands. Subspecies boothii is pale orange with varying amounts of pale yellow-green shading on the hindwing and on the outer part of the forewing; it occurs in the remainder of the Canadian range.
Range: Booth's Sulphur occurs from Baffin Island west along the Hudson Bay and arctic coasts of the Nunavut and Northwest Territories mainland and the southern tier of Arctic Islands to northern Yukon, Alaska, and Eurasia.
Similar Species: This species generally looks intermediate between the Hecla and Labrador Sulphurs and can be confused with both. Subspecies thula looks like a large, pale form of nastes, but flies in wetter, more boggy habitats. Subspecies boothii resembles hecla, but has more yellow shading on the wings and a narrower, dark forewing border. Where the Canada Sulphur (C. canadensis) occurs with Booth's Sulphur, the Canada Sulphur is larger and has more orange on the wings than boothii. [compare images]
Early Stages: These are still largely unknown. Booth's Sulphur belongs to the legume-feeding group of sulphurs.
Abundance: This is a fairly common butterfly, but is rarely collected because it occurs in remote areas of the Arctic.
Flight Season: Adults fly from June until August.
Habits: Booth's Sulphur flies near treeline and north of it in boggy tundra, frequently in areas where there are scattered stunted trees and shrubs.
Remarks: This species has been an enigma for arctic lepidopterists. It has long been considered a hybrid between the Hecla and Labrador Sulphurs, but recent fieldwork in northern Canada indicates that it is a separate species, although there may be some hybridization among the three species. Research on this species in Russia, where it also occurs with hecla and nastes, further supports its status as a separate species and has shown that the correct name for the species is Colias tyche (Mikkola, in litt.). Adults are generally on the wing about a week before the other two species.
© 2002. This material is reproduced with permission from The Butterflies of Canada by Ross A. Layberry, Peter W. Hall, and J. Donald Lafontaine. University of Toronto Press; 1998. Specimen photos courtesy of John T. Fowler.
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Date Modified: 1969-12-31