Giant Sulphur
Colias gigantea Strecker, 1900

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Diagnosis: This is one of the largest (wingspan: 37 to 55 mm) sulphurs found in Canada. It is bright, lemon yellow above with a narrow black border on the upperside in the male. The dark border is largely absent in the female; some females are white. There is a yellow spot in the centre of the hindwing and a bright pink fringe on the wings. The yellow underside has almost no dark shading and a silver, brown-rimmed spot in the middle of the hindwing.

Subspecies: The nominate subspecies gigantea occurs in most of the Canadian range. Subspecies harroweri, which is smaller, occurs from Wyoming into southwestern Alberta north to Crowsnest Pass. Some authors believe that the larger form from southern Manitoba, mayi F. & R. Chermock, should be recognized as a separate subspecies (Klassen et al., 1989), but the differences are slight.

Range: A widespread western species, it is found from the Arctic Ocean in Yukon, east along the northern limit of the boreal forest to the western shores of Hudson Bay and James Bay, and southward into the western U.S. It is absent from open prairie habitats and from most of southern British Columbia, except for a small area around Jesmond and 100 Mile House.

Similar Species: Queen Alexandra's Sulphur (C. alexandra) lacks the pink fringe on the wings. The Pink-edged Sulphur (C. interior) is smaller, with more rounded wings, and has an orange spot in the middle of the hindwing above. The Pelidne Sulphur (C. pelidne) is smaller, and has dusky shading on the underside of the hindwing, often with pink shading over the white spot. [compare images]

Early Stages: The larvae feed on a variety of willows (Salix spp.).

Giant Sulphur (Colias gigantea gigantea). Churchill, Man. J.T. Troubridge

Abundance: The Giant Sulphur is localized to willow bogs, but is widespread in western Canada. It is described as common in northern Manitoba (Klassen et al., 1989).

Flight Season: Adults are on the wing from June into early August.

Habits: In the northern boreal forests and southern tundra, the Giant Sulphur is found in moist areas with willows. Farther south it is restricted to willow bogs and their immediate surroundings. It is an active species that flies swiftly around its chosen territory, stopping to feed on a variety of flowers, including asters.

Remarks: Some authors treat gigantea as a subspecies of the western U.S. mountain species Scudder's Sulphur (C. scudderi Reakirt, 1865).

© 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.

The Toronto Entomologists' Association thanks Agriculture and Agri-Food Canada for providing the content and computer code for this web page.