Shasta Blue
Icaricia shasta (W.H. Edwards, 1862)

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Diagnosis: The upperside in the male is violet blue, with wide brown borders and a row of dark marginal hindwing spots. The female has much wider borders and may be almost totally brown. The hindwing spots are surrounded by orange lunules, which in females form a wavy line. Males rarely have any orange on the hindwing above. In both sexes there is a dark bar at the end of the cell on both wings. The underside is light brown, with two rows of dark spots; the inner forewing row is black and the others are grey or dark brown. The marginal hindwing row has iridescent green centres and is capped with pale yellowish orange. Wingspan: 20 to 22 mm.

Subspecies: There are three subspecies but only subspecies minnehaha is found in Canada.

Range: Icaricia shasta flies in the northwestern U.S., reaching Canada only in southern Saskatchewan and Alberta.

Similar Species: The male of the Lupine Blue (I. lupini) has a pure blue forewing without a dark barshaped spot at the end of the forewing cell. Females of lupini and both sexes of shasta have this spot. Icaricia lupini has a wide orange border on the upper surface of the hindwing that forms a continuous band, wider in females; on the underside this band is bright orange. [compare images]

Early Stages: The eggs are laid singly, usually on leaves but also on stems and fruits. The green larvae eat leaves and fruits of the foodplants, many species of herbaceous Fabaceae, especially Trifolium, Lupinus, and Astragalus spp. According to Scott (1986) they have a two-year life cycle, hibernating as an egg the first winter and as an almost mature larva the second.

Abundance: The Shasta Blue tends to be local and spotty in distribution but can be common where it occurs.

Flight Season: Adults fly from late June and July in most areas, but as late as mid-August above treeline.

Habits: Colonies of the Shasta Blue in Canada are usually on dry ridges, hills, and sagebrush areas in the Prairies, but there are a number of colonies in alpine meadows in the mountains, at or above treeline. They have a very weak flight, and are usually seen in the mountains on bare rock or nectaring on clumps of cushion-plants. Bird et al. (1995) report that adults perch and nectar on yellow composites along the tops of the valley walls of the Oldman and Red Deer Rivers.

© 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.