Oregon Silverspot Butterfly
The Oregon silverspot butterfly (Speyeria zerene hippolyta) is a medium-sized butterfly, predominantly orange and brown with black veins and spots on its hindwings and bright silver spots on its forewings. The length of its forewings is about 1.1 in (2.9 cm). The female is usually slightly larger than the male. This butterfly is listed as threatened by the U. S. Fish and Wildlife Service and has been protected under the Endangered Species Act since 1980.
Inhabiting a very restricted range, the Oregon silverspot occurs only in salt spray meadows along the Pacific coast in Oregon and Washington. This habitat is characterized by heavy rainfall, fog, and mild temperatures. The most critical feature of this habitat, however, is the presence of the western blue violet (Viola adunca), the host plant of the butterfly's larva. For two months each spring, larval Oregon silverspots feed on violet leaves before entering the pupa stage of development. This butterfly was historically present at 17 locations along the coasts of Oregon and Washington, but now only five populations in Oregon are known to exist with certainty.
Housing developments and recreational uses of the coast that destroy or degrade butterfly habitat are the major threats to this subspecies's survival. Natural fire patterns in its meadow habitat have been suppressed, allowing nonnative vegetation to mix with native plants and changing the habitat's character. An area of Lane County, Oregon with a healthy population of Oregon silverspots has been designated critical habitat for this subspecies. Expansion of the population of western blue violets in this area will be encouraged by the control of saplings and other invading plants. Transplantation of western blue violets to other sites with suitable meadow habitat may also be attempted. A recovery plan was put into effect in 1999 and monitored through 2000. It was headed by Lewis and Clark College, the Oregon Zoo in Portland, and the Woodland Park Zoo in Seattle and consisted of rearing the larvae in captivity, then returning the butterflies to the wild. Although the Oregon silverspot butterfly is not in immediate danger of extinction, its specific habitat requirements and the vulnerability of that habitat to degradation and destruction, makes intervention necessary to ensure the long-term survival of this subspecies.
Resources
Books
Howe, W. H. The Butterflies of North America. Garden City, NY: Doubleday, 1975.
Other
U.S. Fish and Wildlife Service Revised Recovery Plan Published for the Oregon Silverspot Butterfly. November 29, 2001 [cited May 2002]. <http://news.fws.gov/NewsReleases/R1 /C71501ED-5742-4E26-965408A77BC0875F.ht ml>.
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