Canada Sulphur
Colias canadensis Ferris, 1982

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Diagnosis: This variable species is usually a pale yellowish orange and looks like a pale form of the Hecla Sulphur but with narrower dark borders. The black discal spot in the centre of the forewing and the orange one on the hindwing may be prominent or virtually absent. The underside of the hindwing is dusky yellow or pale yellowish green, and the red streak extending out from the rim of the white discal spot is not prominent. Females most commonly are white (but pale orange forms occur) with a wide dark forewing border containing a row of large pale spots. Wingspan: 32 to 47 mm.

Range: The Canada Sulphur occurs in Yukon, Alaska, and western Northwest Territories southward to northern British Columbia and Alberta and in the Rocky Mountains to Highwood Pass in Alberta.

Similar Species: Males of the Canada Sulphur closely resemble the Hecla Sulphur but are a paler yellowish-orange colour above, without the violet iridescence of hecla, the black outer margin tends to be narrower, and the hindwing is paler on the underside with a less prominent red streak extending out from the discal spot. Females resemble white females of Colias philodice subspecies vitabunda, but can be recognized by the red streak extending from the discal spot on the hindwing below and by the lack of dark dots on the underside along the wing margins. See also Booth's Sulphur (C. tyche). [compare images]

Early Stages: These are unknown, but the Canada Sulphur belongs to the legume-feeding group of sulphurs.

Abundance: This butterfly is fairly common in its restricted northwestern range.

Flight Season: Adults fly from early May to early August in Alberta and from late May until mid-July in the north.

Habits: The Canada Sulphur occurs in open taiga forests and in wet shrub tundra among stunted trees at and near treeline in the mountains and the north.

Remarks: This species was originally described as a subspecies of hecla, but it was later discovered that the ranges of hecla and canadensis overlap widely in Yukon and Alaska, so canadensis was elevated to distinct species status by Ferris (1988). The range of canadensis abuts that of boothii in the north, so some workers suspect that it may be a subspecies of boothii. JDL has observed hecla, canadensis, and boothii occurring together in the British Mountains in northern Yukon and all three were readily identifiable with no evidence of hybridization. They had different peak flight seasons and different preferred habitats but all occurred together, so we continue to treat canadensis as a valid species. Where they occurred together the sequence of species was canadensis, then boothii, and finally hecla.

© 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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