Speyeria zerene hippolyta
The Oregon silverspot butterfly (Speyeria zerene hippolyta) is listed as a threatened species under the United States Endangered Species Act. Patches of Oregon silverspot habitat occur in Oregon, Washington and California. Development, grazing and off-road vehicles are all to blame for this butterfly’s decline. Changes in fire regime, introduced plant species and pesticides also threaten this butterfly.
Historically, the coastal meadow habitats used by the Oregon silverspot were maintained in an early successional state by periodic fires. Fires prevent trees and shrubs from overshadowing low-growing plants such as violets (genus Viola). Recently, fires have been prevented because development has made them undesirable. Thus, meadow habitat has gradually been replaced by forest. Recognition of the role of fire and other periodic disturbance in the maintenance of Oregon Silverspot habitat has allowed appropriate management strategies to be enacted and the butterfly’s future is relatively bright.
This butterfly is a member of the family Nymphalidae. It belongs to one of fifteen subspecies of Speyeria zerene Boisduval. The silverspot has wings as wide as 27 mm (1 in) for males and 29 mm (1.1 in) for females. The silverspot has orange and brown markings with black veins and spots on the dorsal side of the wings, and bright metallic silver spots on the ventral sides.
The silverspot requires one of three types of grasslands: coastal salt spray meadows, stabilized dunes, and montane meadows. The Oregon silverspot butterfly’s primary source of food is the western blue violet (Viola adunca). Adults appear throughout the late summer and early fall to mate. The eggs are laid during the fall and hatch shortly thereafter. The larvae feed for a short time in the fall and then enter a dormant state in which they spend the winter. In the spring the larvae resume feeding until the late spring or summer when they pupate. Their pupation time is short and adults soon emerge to continue the cycle.
The Oregon silverspot once inhabited suitable coastal habitat in Washington, Oregon and Northern California. It is now found at only four sites in Oregon.