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