California Giant-Skipper (Agathymus stephensi [Skinner])
Wing span: 2 - 2 1/4 inches (5.1 - 5.7 cm).
Identification: Fringes are distinctly checkered. Upperside is brown-black with yellowish scales at the wing bases and cream-colored spots. Hindwing spot band is curved and there is usually a spot in the cell. Underside of hindwing is mottled gray with irregular bands of cream-colored spots.
Life history: The adults roost on bushes, the males usually in canyon bottoms. From early morning to noon males perch near host plants to wait for receptive females. Eggs are laid singly on the host and fall to the base of the plant. A young caterpillar crawls to a leaf tip and burrows inside where it eats pulp and then hibernates. In the spring the caterpillar make a new burrow in a leaf base where it feeds on sap until ceasing activity for the summer. Before pupating, the caterpillar enlarges the opening of its burrow and makes a silk trap door from which the adult can emerge.
Flight: One brood from September-October.
Caterpillar hosts: Desert agave (Agave deserti).
Adult food: Females do not feed; males sip moisture from mud.
Habitat: Sonoran desert.
Range: The Colorado Desert in Riverside and San Diego counties, California; Baja California Norte.
Conservation: Populations and their habitats should be conserved wherever found.
The Nature Conservancy Global Rank: G2 - Imperiled globally because of rarity (6 to 20 occurrences), or because of other factors demonstrably making it very vulnerable to extinction throughout its range. (Endangered throughout its range).
Management needs: Conserve habitat and discourage overgrazing.
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. 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.