Diagnosis: The upperside is bright yellow at the base with a broad orange band on the outer two-thirds. The underside is olive yellow. There is an uncommon white female form with little black on the border of the wings. Wingspan: 35 to 52 mm.
Subspecies: There are three subspecies in Canada. The nominate subspecies christina occurs in most of the Canadian range; subspecies astraea, with duller orange on the forewings and a more olive underside, occurs in the western U.S. northward to northern Montana, where it forms a cline with the nominate subspecies in southwestern Alberta. Subspecies kluanensis occurs in southwestern Yukon; it is discussed below under Remarks.
Range: This butterfly is found from Wyoming north to Gillam in central Manitoba (one record from Churchill), in southern Saskatchewan west through Alberta and northeastern British Columbia and north into Yukon and western Northwest Territories.
Similar Species: The distinctive orange and yellow pattern differentiates it from most other Colias species. The Orange Sulphur (C. eurytheme) has orange shading to the wing base and the silver spot on the underside of the hindwing has a double pink rim. Booth's Sulphur (C. tyche) and the Hecla Sulphur (C. hecla) have little if any yellow on the wings and there is a distinctive short red streak extending away from the white distal spot on the underside of the hindwing [compare images].
Early Stages: Larvae have been reared on sweet-vetch (Hedysarum spp.) at The Pas, Manitoba, and JDL has seen christina laying eggs on this plant in Kluane National Park in Yukon. The larvae are similar to those of Queen Alexandra's Sulphur (C. alexandra).
Abundance: This sulphur is usually fairly common.
Flight Season: The Christina Sulphur is on the wing from May to September, with the major flight in July in most of the Canadian range.
Habits: The Christina Sulphur is mainly a woodland species, flying in open areas and along roadsides where legumes are found.Remarks: There has been a great deal of debate over the status of this butterfly, but it appears to be distinct from Queen Alexandra's Sulphur. Ultraviolet reflectance in males coincides with the orange areas of the wings. Ferris (1993) segregated Krauth's Sulphur (Colias krauthii Klots) from the Black Hills in South Dakota as a species separate from Colias christina and associated kluanensis Ferris with Colias krauthii as a subspecies. Typical kluanensis differs from christina in several characters: the underside of the hindwing is a dark mossy green rather than the olive colour produced by dark speckling over the yellow ground colour; the white spot in the middle of the hindwing underside is small and thinly rimmed in pink; females have a relatively complete dark border on the forewing, and are heavily dusted with dark scales, especially on the hindwing. Ferris examined specimens of kluanensis from along the Alaska Highway between Whitehorse and the Alaskan border. He also saw several specimens from the Dawson area in the Canadian National Collection that he labelled "near christina." We now have many more Yukon specimens of this group from the Alaska Highway east of Whitehorse and from the Klondike Highway that runs from Whitehorse to Dawson. These specimens show a complete cline in all of the characters that separate kluanensis from christina, so we treat it as a subspecies of Colias christina rather than as a separate species. There are several prairie species that are disjunct in the steppe habitat near Kluane and this appears to be another example of this phenomenon. It is possible that the construction of the Alaska Highway provided a corridor of habitat that has allowed the ranges of subspecies christina and subspecies kluanensis to come together and intergrade.
Some researchers have suggested that Colias christina should be treated as an eastern subspecies of Colias occidentalis, based primarily on the occurrence of possible hybrid populations in eastern Oregon. The differences between the species discussed by Ferris (1993) and diagnosed above, and the local nature of the possible hybrid population, suggest that it is best to retain their status as distinct species. Many of our Colias species seem to hybridize with their closest relatives under certain conditions.
© 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: 2010-05-31