Long-term survival of the Unsilvered Fritillary is in question: one race is now extinct, and, based on anecdotal accounts, the other two are in decline.  NatureServe ranks the species Critically Imperiled at both national and statewide levels.  Does it merit federal endangered species status?

Butterflies of the genus Speyeria, and their host plants (violets; genus Viola), are considered to be among the better ecological indicators of quality of native habitats.  This suggests they are sensitive to disturbance, especially loss of habitat and food resource depletion.  Human disturbance - agriculture, logging, introduced non-native plants, suburban development, and livestock overgrazing - has factored in population declines of several fritillary species: two examples are the Diana Fritillary of the S. Appalachians and the Regal Fritillary of midwestern prairies.

In California, the Atossa Fritillary (Speyeria adiaste atossa), was once a common butterfly that ranged widely across high elevation grasslands in S. California, where its probable host plant was the Pine Violet (Viola purpurea).  The last known atossa specimen was collected in 1959.  Overgrazing of grasslands by livestock, in combination with drought, are likely factors in the extinction of this fritillary.

Sadly, Clemence’s Unsilvered Fritillary (Speyeria adiaste clemencei), seems determined, in the words of UC Davis lepidopterist Dr. Art Shapiro, to follow atossa to that “great flowery meadow in the sky.”  Clemencei is limited today to a few small isolated colonies in Monterey and San Luis Obispo counties.  In Monterey County, summer surveys in 2011 counted fewer than 1,000 flying adults. 

Clemencei is subject to multiple threats, including introduced, non-native grasses in host plant grasslands, livestock grazing, and poaching/commercial collecting.  Introduction of non-native grasses into meadows can crowd out native plants like violets.  The effects of grazing are complex: some level may be beneficial, by reducing the accumulation of dead leaves and non-native grasses, but overgrazing can damage the larval Viola food plant. 

The impact of collecting at this time is equivocal.  Private collectors covet specimens at the Chew’s Ridge colony site, which is widely published in the literature and on the internet.  It is not likely that prudent taking of a few individuals for private collections poses a serious threat to this colony; however, over-collecting by either private or commercial enterprise is another matter.  During mid-summer, meadows containing dense patches of the Viola host plant concentrate slow-flying, patrolling clemencei males and ovipositing females, both of which can then be easily captured by net and removed from the population.  In the 1920’s, John Comstock once took 500 adult atossa from one location in S. California.  A similar thoughtless act today would decimate the Chew’s Ridge colony.  Females are especially vulnerable: summer 2011 surveys of this colony found an approximate 5:1 (male:female) sex ratio, suggesting fewer than 100 females throughout the adult flight season.

Proposals in 1998 and 2010 to list the Unsilvered Fritillary as federally endangered were rejected by the US Fish and Wildlife Service due to lack of data on the range, distribution, and population size of the two remaining subspecies*. 

*DEPARTMENT OF THE INTERIOR Fish and Wildlife Service

50 CFR Part 17 / FWS–R8–ES–2010–0078; MO 92210–0–0008 B2

Endangered and Threatened Wildlife and Plants; 90-Day Finding on a Petition To List the Unsilvered Fritillary Butterfly as Threatened or Endangered

ACTION: Notice of 90-day petition finding.

SUMMARY: We, the U.S. Fish and Wildlife Service, announce a 90-day finding on a petition to list the unsilvered fritillary butterfly (Speyeria adiaste) as threatened or endangered under the Endangered Species Act of 1973 (Act), as amended, and designate critical habitat. Based on our review, we find that the petition does not present substantial scientific or commercial information indicating that listing the unsilvered fritillary may be warranted. Therefore, we are not initiating a status review in response to this petition. We ask the public to submit to us any new information that becomes available concerning the status of, or threats to, the unsilvered fritillary or its habitat at any time.

DATES: The finding announced in this document was made on February 24,2011.

EXCERPT: The petition states that the unsilvered fritillary has vanished from much of its range and asserts that this is due to human activities, including habitat loss and degradation due to burgeoning human populations, with resultant urban and suburban sprawl; increasing agriculture; extensive livestock grazing; off-road vehicle use; and other adverse land uses. The petition also asserts that climate change has taken and will take its toll through altered fire regimes, more severe and frequent droughts, and shifts in native plant distribution... The mere identification of factors that could impact a species negatively may not be sufficient to compel a finding that listing may be warranted. The information must contain evidence sufficient to suggest that these factors may be operative threats that act on the species to the point that the species may meet the definition of threatened or endangered under the Act. We found no information to suggest that threats are acting on the unsilvered fritillary such that the species may become extinct now or in the foreseeable future.