Northern Blue
Lycaeides idas (Linnaeus, 1761)

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Diagnosis: Males are bright purplish blue above, with very narrow black margins and sometimes faint dark marginal spots on the hindwing. In females, at least the outer half of the wing is dark brownish grey, with a bluish sheen and often with a trace of orange marginal spots. Both sexes are pale grey beneath, with black spots in the central area and a marginal row of black spots on both wings, with metallic blue centres and capped with orange and black on the hindwings. Wingspan: 17 to 28 mm.

Subspecies: There are about a dozen subspecies in North America, and six in Canada. Subspecies aster is found in Newfoundland; subspecies empetri, described from Baddeck, Nova Scotia, flies throughout the Maritime Provinces; subspecies scudderii occurs throughout most of the remainder of the Canadian range, except in the west. Subspecies ferniensis is found in the southern interior of British Columbia; subspecies anna occurs on the west coast and Vancouver Island; and subspecies alaskensis occurs in northern British Columbia and Yukon. In subspecies empetri the underside markings are much larger and more distinct than in the other subspecies. Adults of subspecies empetri and aster are smaller than those of western subspecies and feed on heaths (Ericaceae) rather than on legumes.

Range: Found in all provinces and territories, idas ranges from southern Nova Scotia, north to Hopedale, Labrador, Churchill, Manitoba, Herschel Island, Yukon, and Tuktoyuktuk, Northwest Territories. It is absent from Quebec south of about 47° N and Ontario south of about 48° N. It is also found in northern Europe and Asia.

Similar Species: The Melissa Blue (L. melissa) has a more continuous orange band near the margin of the hindwing underside. [compare images]

Early Stages: The pale grey-green eggs are laid singly on or under the foodplants, and overwinter. The larvae are not well known in North America, but are described as being green or brownish with an obscure lateral stripe (Pyle, 1981). Foodplants include Black Crowberry (Empetrum nigrum), especially in the Maritimes, Dwarf Blueberry (Vaccinium caespitosum), Labrador Tea (Ledum groenlandicum), and Sheep Laurel (Kalmia angustifolia) in the east and probably in Manitoba, and various Fabaceae farther west, including Astragalus, Lathyrus, and Lupinus spp.

Northern Blue (Lycaeides idas scudderi). Churchill, Man. J.T. Troubridge

Abundance: This blue is often abundant.

Flight Season: The Northern Blue flies from late June (the Prairies) to late August.

Habits: In the Maritimes, idas is most common on coastal headlands, where Black Crowberry is often a major constituent of the flora, and also, at least in southeastern Cape Breton, in bogs where the Crowberry is often almost overwhelmed by sphagnum. In both habitats, it flies as early as 8 a.m., and even in dense fog. Inland, it flies in a variety of habitats and uses other foodplants. North of Chibougamau, Quebec, a large colony was found at an old abandoned campsite with a dense growth of Sheep Laurel. On the Prairies it is usually found in sandy coniferous forest areas.

© 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.