Boisduval's Blue
Icaricia icarioides (Boisduval, 1852)

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Diagnosis: The upperside in the male is bright blue with dark wing margins, wider on the forewing. In the female it varies from dark brown to blue with wide dark margins. Males usually lack any trace of a dark discal spot at the end of the cell on both wings, and usually have only a trace of dark marginal spots on the hindwing. The underside is pale grey with two irregular rows of white-ringed black spots, much larger on the forewing, with the outer row a series of tiny black dots; on the hindwing the black in both rows is often so reduced that the spots are white, with or without a tiny black centre. Wingspan: 21 to 32 mm.

Subspecies: There are about a dozen subspecies, but only three occur in Canada. Subspecies pembina is found from the Prairies to eastern British Columbia; subspecies montis occurs at high elevations in the interior of British Columbia; and subspecies blackmorei is found on the west coast and Vancouver Island.

Range: Icaricia icarioides ranges throughout the western U.S., reaching Canada from southern Saskatchewan to Vancouver Island, north to Lake Louise in Alberta and Wells Grey Provincial Park in British Columbia.

Similar Species: The Greenish Blue (Plebejus saepiolus) and the Silvery Blue (Glaucopsyche lygdamus). [compare images]

Early Stages: The eggs are laid singly on any part of the plant. Larvae eat leaves, but transfer later to flowers and fruits. They hibernate in the second instar, and then eat the fresh new shoots of the foodplant in the spring. Larvae are reddish purple, or green with purplish dorsal stripes and white diagonal stripes on the sides. Foodplants are many different species of lupines (Lupinus spp.), although densely hairy species are preferred to less hairy ones (Scott, 1986).

Abundance: Boisduval's Blue is abundant within colonies, scarce between them; it seems that there is relatively little travel between colonies.

Flight Season: Adults are on the wing from mid-June to early September, with two generations per year.

Habits: Boisduval's Blue is found in prairie, sagebrush and woodland clearings, usually in localized colonies.

© 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.