Arrowhead Blue (Glaucopsyche piasus [Boisduval])
Wing span: 1 1/8 - 1 3/8 inches (2.9 - 3.5 cm).
Identification: Checkered fringes. Upperside of male violet blue with a wide border; female duller. Underside gray with many small black spots. Hindwing with postmedian band of white "arrowheads" pointing inward.
Life history: Males patrol during the day near host plants. Females lay eggs on flower buds of host plant; caterpillars eat flowers and fruits. Chrysalids hibernate.
Flight: One brood from March-July.
Caterpillar hosts: Lupine (Lupinus) and milkvetch (Astragalus) species in the pea family (Fabaceae).
Adult food: Flower nectar.
Habitat: Coastal dunes and lowlands in California; mountains elsewhere: scrub, openings in woods, roadsides, trails, meadows, clearings, streamsides.
Range: Local and uncommon. British Columbia and southern Alberta south through the mountains of western North America to southern California, northern Arizona, and western Nebraska.
Conservation: Populations in southern California need assessment; elsewhere populations are probably not in jeopardy.
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
State and Regional References:
Opler, Paul A. 1999. Peterson Field Guide to Western Butterflies, revised edition. Houghton Mifflin Co., Boston, Mass. Stanford, R.E. and P.A. Opler. 1993. Atlas of Western USA Butterflies. Privately published, Denver, Colo.