Pink-edged Sulphur
Colias interior Scudder, 1862

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Diagnosis: A medium-sized sulphur with a bright pink edge on all four wings. The upperside is bright yellow with a black border, narrower on the hindwing, with the black spot in the forewing cell faint or absent. The spot in the middle of the hindwing above is usually orange. The underside silvery spot is single and pink-rimmed. The female has greatly reduced black borders on the upperside and has a rare white form. Wingspan: 35 to 47 mm.

Subspecies: Although some authors have recognized several subspecies in the past, none is currently recognized.

Range: This is a Boreal Zone species that also occurs in the U.S. in the west to Oregon and in the east from New England south in the Appalachians to Virginia. It is widespread in all provinces and into southern Northwest Territories at Fort Smith and Little Buffalo River.

Similar Species: The Giant Sulphur (C. gigantea) and the Pelidne Sulphur (C. pelidne). [compare images]

Early Stages: The yellow-green larva has light stripes on the back and a white lateral stripe with a red line through it, partially margined by blue. The larva feeds on blueberry (Vaccinium spp.) and overwinters.

Abundance: Although widespread, the Pink-edged Sulphur tends to be local and uncommon in blueberry bogs and barrens.

Flight Season: Depending on location, the butterflies can be found on the wing from late May into early September; there is only one brood.

Habits: Because its larva feeds on blueberry, it is most often seen in scrubby openings in wooded areas and bogs where blueberries grow. It is regularly encountered in recently cleared or burnt-over areas.

Remarks: In 1978, RAL collected a very striking and rare bilateral gynandromorph near Luskville, Quebec. The left side is a typical yellow male while the right side is a white female; it is in the Canadian National Collection.

© 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.