Unsilvered fritillary Speyeria adiaste
ESA status: petitioned for listing
Violets enliven many a shadowy patch of forest with their vividly colored flowers. But for some, the violet’s importance goes beyond the visual. The unsilvered fritillary, a delicate yet vibrantly colored butterfly found along the Central Coast of California, is a true violet connoisseur. This species can be seen fluttering about in openings in conifer and redwood forests, as well as oak woodlands, chaparral, and grassy slopes, during June and July. It lays single eggs on fallen leaves and twigs near violets. When the caterpillars emerge, they feed on violet leaves. And the adult fritillaries feed on flower nectar, primarily from – you guessed it – violets.
There are three subspecies of unsilvered fritillary (Speyeria adiaste), one of which is considered extinct (the atossa subspecies); it used to live in Kern, Los Angeles, and Santa Barbara counties, but has not been seen since 1959 despite subsequent surveys. The two others face multiple threats within their limited ranges. They persist in just two isolated areas: the first includes high areas in the Santa Cruz Mountains in San Mateo, Santa Cruz, and Santa Clara counties (the adiaste subspecies), and the second includes the Santa Lucia Mountains in Monterey and San Luis Obispo counties (the clemencei subspecies).
Fritillaries in the genus Speyeria are strongly affected by changes in their environment. Scientists have long acknowledged that these butterflies, along with their violet food plants, are among the most sensitive to human disturbance and some of the first species to disappear in altered habitats. They are therefore an important indicator for healthy, functional native ecosystems. But the news they are relaying from the California Coast is not good.
Development, fire suppression, widespread fires, overgrazing, and exotic vegetation are causing the loss or degradation of this butterfly’s habitat. Scientists suspect that the atossa subspecies may have gone extinct due to a combination of overgrazing and drought. Changing fire regimes may allow brush and trees to encroach on the open areas the fritillary prefers, crowding out the violets they depend on. A growing human population in the Central Coast area of California has fragmented habitat for many wildlife species, including the fritillary. Cities have spread like amoebas since the 1980s. Outside of the cities, crop and livestock agriculture consumes 11 percent of the Central Coast area, and both of these activities degrade and eliminate habitat or spread invasive weeds.
The fritillary population has undergone a substantial decline, anywhere in the range of 50 to 90 percent. WildEarth Guardians is urgently working to protect the unsilvered fritillary under the Endangered Species Act: federal protection is this rare, delicate butterfly’s best chance for survival, since insects are not allowed protection under the California Endangered Species Act. California’s coastline is a beautiful, diverse ecosystem, and WildEarth Guardians intends to preserve it intact for future generations of both humans and unsilvered fritillaries.
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photo credit: © Jeff Pippen