Oregon Silverspot Butterfly Speyeria zerene hippolyta General Information Official Status: Threatened, the Oregon silverspot butterfly is federally listed under the Endangered Species Act as threatened. Date Listed: effective October 15,1980; (pdf, 500 KB) Critical Habitat: Critical habitat was designated at the time of listing, and includes the salt-spray meadow between Big Creek and Rock Creek, Lane County, Oregon. This includes those portions of Section 15 and of the south half of Section 10 which are west of a line parallel to, and 1,500 feet west of, the eastern section boundaries of Sections 10 and 15, T16S, R12W, Willamette meridian.
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Recovery Plan: Oregon Silverspot Butterfly (Speyeria zerene hippolyta) (pdf, 1.0 MB), published August 2001. Oregon Silverspot Butterfly Photo Credit:USFWS File Photograph Identifying Characteristics: This is a medium-sized butterfly with a wingspan of approximately 5.5 cm (2.2 inches).
The upper surfaces are golden brown with numerous black spots and lines. Wing undersides are brown, orange-brown, and tan with black lines and distinctive silver and black spots. Basal areas of the wings and body are covered with fine hairs. The Oregon silverspot is a member of the family of true fritillary, or silverspot butterflies, of which 13 species occur in North America. The species Speyeria zerene, sometimes known as the Zerene Fritillary, includes a number of subspecies, of which 8 occur in the Pacific Northwest and on the California coast.
The Oregon silverspot butterfly is similar in appearance to two other coastal subspecies of Speyeria zerene, the Behren’s silverspot butterfly ( S. Behrensii) and Myrtle’s silverspot butterfly ( S. Myrtleae), both of which are also federally listed. The Oregon silverspot differs from the Behren’s silverspot primarily by less dark basal suffusion on the upper sides of the wings and its relative smaller size. The Myrtle’s silverspot is larger in size than the Oregon silverspot. Both the Myrtle’s and Behren’s silverspot butterflies occur well to the south of the Oregon silverspot. Flicker free download.
Current Geographic Range: The historic range of Oregon silverspot butterfly extended along the Oregon and Washington coasts from Westport, Washington south to around Heceta Head in Oregon, and in a separate coastal area north of Crescent City in Del Norte County, California. At least 17 historic sites are known. The current known range is limited to five sites, including four in coastal Oregon in Lane and Tillamook counties, and one in Del Norte County, near Lake Earl. The butterfly’s presence at a six site, in Clatsop County, is uncertain due to a population decline. Life History: Females lay eggs in the debris and dried stems of the main larval food plant, the early blue violet ( Viola adunca). This is a small, native, perennial herb with pale to deep violet flowers, which typically blooms in late spring to early summer, and dies back to the perennial rhizome during winter. Early blue violets occur widely in western North America, but within the Oregon silverspot range, are associated with coastal grasslands and, at one site, montane meadows.
Little is known about the biology of the caterpillars or pupae. Caterpillars (larvae) are dark-colored with many branching, sharp spines on their backs. Upon hatching, the larvae spin a silk pad upon which they pass the fall and winter in diapause (dormancy). Upon ending diapause in the spring, the larvae seek out the violet food plant. During the spring and early summer they pass through six instars (stages of development) before forming a pupa within a chamber of leaves that they draw together with silk.