Dingy Fritillary (Boloria improba [Butler])
Wing span: 1 1/8 - 1 3/8 inches (3 - 3.5 cm).
Identification: Small. Upperside dull orange-brown, darker at wing bases; markings faded and indistinct. Underside hindwing dark orange-brown at base, often grayish on outer half. Hindwing with ivory white costa and ivory dash between costa and cell.
Life history: Males patrol near the ground in the vicinity of host plants. Eggs are laid singly on stems of host plant; caterpillars eat leaves. Two years are required for development from egg to adult; newly hatched caterpillars hibernate the first winter, fourth-stage caterpillars the second winter.
Flight: One brood from late June-early August.
Caterpillar hosts: Dwarf willows including Salix arctica and S. reticulata nivalis.
Adult food: Flower nectar.
Habitat: Moist tundra with dwarf willows.
Range: Holarctic. Alaska east through Northwest Territories to Baffin Island, south to Yukon Territories and northern British Columbia. Isolated populations in central Canadian Rockies, southwest Wyoming, and southwest Colorado.
Conservation: The Uncompahgre Fritillary (Boloria improba acrocnema) is a listed United States Endangered Species found in the San Juan Mountains of southwest Colorado.
The Uncompahgre Fritillary has The Nature Conservancy Global Rank of G1 - Critically imperiled globally because of extreme rarity (5 or fewer occurrences, or very few remaining individuals), or because of some factor of its biology making it especially vulnerable to extinction. (Critically endangered throughout its range).
The other subspecies of Boloria improba have The Nature Conservancy Global Rank of G5 - Demonstrably secure globally, though it may be quite rare in parts of its range, especially at the periphery.
Management needs: Monitoring and recovery actions are ongoing for the Uncompahgre Fritillary..
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:
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.