North American Butterflies and Moths List

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Butterflies of North America

Shasta Blue (Plebeius [Icaricia] shasta)
JPG -- species photo

Shasta Blue (Plebeius shasta [W. H. Edwards])

Wing span: 7/8 - 1 1/8 inches (2.2 - 3 cm).

Identification: Upperside of male lilac blue with a wide dark border; female darker, may have orange band at outer margin of hindwing. Both sexes with dark cell bars on fore- and hindwings. Underside of both sexes gray with black postmedian spots; other spots are dark gray. Hindwing outer margin with iridescent green spots capped by a light band.

Life history: Males fly just above the ground to search for females. Eggs are laid singly on leaves of host plants; caterpillars feed on leaves and flowers. Where found above timberline, these butterflies require 2 years to mature, spending their first winter as eggs and the second winter as mature caterpillars.

Flight: One brood from June-August.

Caterpillar hosts: Various Astragalus, Lupinus, and Trifolium species of the pea family (Fabaceae).

Adult food: Flower nectar.

Habitat: Cushion-plant communities in forest openings, sagebrush hills, high plains, prairies, and alpine fell-fields.

Range: High elevations from Washington east to North Dakota and Nebraska; south to central California and Colorado.

Conservation: Not usually of conservation concern.

The Nature Conservancy Global Rank: G5 - Demonstrably secure globally, though it may be quite rare in parts of its range, especially at the periphery.

Management needs: Not reported.


Scott, J. A. 1986. The butterflies of North America. Stanford  University Press, 
    Stanford, Calif. 583 pages, 64 color plates.

Tilden, J. W. 1986. A field guide to western butterflies.  Houghton-Mifflin Co., 
    Boston, Mass. 370 pages, 23 color plates.

Author: Jane M. Struttmann

Shasta Blue (Plebeius [Icaricia] shasta)
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