Northwestern Fritillary (Speyeria hesperis [W.H. Edwards])
Wing span: 2 - 2 3/4 inches (5 - 7 cm).
Identification: Quite variable. Upperside orange-brown, often darker at base, with black outer margins especially on forewing; male has black scales on veins. Underside of hindwing with basal disk or light brown orange-brown with pale submarginal band; spots silvered or unsilvered.
Life history: Males patrol during the day in open areas. Eggs are laid singly on leaf litter near host plant. Unfed first-stage caterpillars overwinter, emerging in spring to feed on leaves.
Flight: One flight from June-October, mainly July-August.
Caterpillar hosts: Violets.
Adult food: Flower nectar including Gaillardia, rabbitbrush, purple mints, and shrub cinquefoil.
Habitat: Forest openings, meadows, and open hillsides.
Range: Western mountains from central western Alaska, Yukon, and Northwest Territories south to central California, Arizona, and New Mexico.
Conservation: Not usually of conservation concern. Subspecies elko Austin and hanseni Emmel and Emmel are of conservation concern because of their small ranges. The former may be threatened by invasive alien weeds including smooth brome and/or cheatgrass.
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: None reported.
Ferris, C.D. and F.M. Brown. 1981. Butterflies of the Rocky Mountain States. University of Oklahoma Press, Norman. 442 pages. Garth, J.S. and J.W. Tilden. 1986.California Butterflies. University of California Press, Berkeley and Los Angeles. 246 pp, 24 plates. Layberry, R.A., P.W. Hall, and J.D. Lafontaine. 1998. The Butterflies of Canada. University of Toronto Press, Toronto. 282 pages, 32 color plates. Opler, P.A. 1999. A field guide to western butterflies. Houghton-Mifflin Co., Boston, Mass. 540 pages, 44 color plates. Scott, J. A. 1986. The butterflies of North America. Stanford University Press, Stanford, Calif. 583 pages, 64 color plates. Stanford, R. E. and P. A. Opler. 1993. Atlas of western USA butterflies including adjacent parts of Canada and Mexico. Denver and Fort Collins, CO.
Author: Paul A. Opler
State and Regional References:
Brown, F.M., Eff, J.D., and B. Rotger. 1957. Colorado Butterflies. Denver Museum of Natural History, Denver. Ferris, C.D. and F.M. Brown. 1980. Butterflies of the Rocky Mountain States. University of Oklahoma Press. Norman. 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.