Western White (Pontia occidentalis [Reakirt])
Wing span: 1 1/2 - 2 1/8 inches (3.8 - 5.3 cm).
Identification: Upperside of forewing has marginal markings that are lighter than the submarginal stripe. Below, forewing tip and hindwing have veins outlined with gray-green. Short-day spring and fall forms have more prominent markings.
Life history: Males patrol hilltops and ridges for receptive females. Females lay eggs singly on host plants. Caterpillars will feed on leaves but prefer buds, flowers, and fruits. Chrysalids hibernate.
Flight: One flight from June-July in far north; two flights from May-August in the south.
Caterpillar hosts: Flowers and fruits of various members of the mustard (Brassicaceae) family.
Adult food: Flower nectar.
Habitat: Mountain peaks, slopes, hilltops, railroad yards, open plains, roadsides.
Range: Alaska south to central California, northern Arizona and northern New Mexico; east to North Dakota and central Ontario.
Conservation: Not usually required.
Management needs: None noted.
The Nature Conservancy Global Rank: G5 - Demonstrably secure globally, though it may be quite rare in parts of its range, especially at the periphery.
Opler, P. A. and V. Malikul. 1992. A field guide to eastern butterflies. Peterson field guide #4. Houghton-Mifflin Co., Boston. 396 pages, 48 color plates. 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:
Emmel, T.C. Editor. 1998. Systematics of western North American butterflies. Mariposa Press, Gainesville, Florida. Layberry, R.A., Hall, P.W. & Lafontaine, D.J., 1998. The Butterflies of Canada. University of Toronto Press, Toronto, ON. 280 pp. 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. Tilden, J.W. and A.C. Smith. 1986. A Field Guide to Western Butterflies. Houghton Mifflin Co., Boston, Mass.