Behren's Silverspot Butterfly

Speyeria zerene behrensii

Description

Behren's silverspot butterfly, Speyeria zerene behrensii, is also a member of the brush-footed butterfly family (Nymphalidae). It was first described by William H. Edwards in 1869 from an adult male collected by an unknown lepidopterist in Mendocino, California. It is a medium-sized butterfly with a wingspan of approximately 2.2 in (5.5 cm). 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 densely pubescent. Behren's silverspot butterfly is similar in appearance to two other subspecies of S. zerene. The Oregon silverspot butterfly (S. zerene hippolyta ), federally listed as threatened, has lighter basal suffusion on the upper sides of the wings than Behren's silverspot butterfly. The endangered Myrtle's silverspot butterfly (S. zerene myrtleae ), another related taxon, is larger in size and also lighter in color than S. zerene behrensii.

Behavior

The life history of Behren's silverspot butterfly is similar to the callippe silverspot butterfly. The females lay their eggs in the debris and dried stems of the larval foodplant, violet (Viola adunca ). Upon hatching, the caterpillars wander a short distance and spin a silk pad upon which they pass the fall and winter. The larvae are dark-colored with many branching, sharp spines on their backs. The caterpillars immediately seek out the foodplant upon termination of their diapause in the spring. They pass through five instars before forming a pupa within a chamber of leaves that they draw together with silk. The adults emerge in about two weeks and live for approximately three weeks. Depending upon environmental conditions, the flight period of this single-brooded butterfly ranges from July to August. Adult males patrol open areas in search of newly emerged females.

Habitat

Behren's silverspot butterfly inhabits coastal terrace prairie habitat.

Distribution

The historic range of Behren's silverspot butterfly extends from the mouth of the Russian River in Sonoma County northward along the immediate coast to southern Mendocino County in the vicinity of Point Arena. Six historic populations are known from coastal terrace prairie and associated habitats. The single extant population is located on private land near Point Arena in Mendocino County. No specimens have been observed at the sites of the other historically known colonies since 1987.

Threats

Behren's silverspot butterfly has been extirpated from five of its six historical locations, one of which was eliminated by a housing development. This species is currently known from a single locality near Point Arena in Mendocino County which is subject to grazing by livestock. Although no development plans have been proposed for this site, urban development is occurring in the vicinity.

Conservation and Recovery

The greatest need for conservation of the Behren's silverspot is to protect its last remnant of critical habitat in Mendocino County. This site is privately owned, and should be protected by acquiring the land and designating an ecological reserve, or by negotiating a conservation easement. The critical habitat must be protected against degrading activities, such as trampling by off-road vehicles, equestrians, and pedestrians. The butterfly itself must be protected against collecting for sale in the commercial trade in lepidopteran specimens, or by amateur collectors. The population of the Behren's silverspot should be monitored, and research undertaken into its biology and habitat needs, including management practices needed to maintain its habitat in good condition (such as prescribed burning). Planning should be undertaken towards the establishment of additional populations of this rare butterfly.

Contacts

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
http://pacific.fws.gov/

Sacramento Fish and Wildlife Office
2800 Cottage Way, Room W-2605
Sacramento, California, 95825-1846
Telephone: 916-414-6600
Fax: 916-460-4619

Reference

U. S. Fish and Wildlife Service. 5 December 1997. "Endangered and Threatened Wildlife and Plants: Determination of Endangered Status for the Callippe Silverspot Butterfly and the Behren's Silverspot Butterfly and Threatened Status for the Alameda Whipsnake." Federal Register 62 (234): 64306-64320.