Unsilvered Fritillary
Speyeria adiaste
One of the rarest butterfly species in the U.S., with a few small colonies in four central California counties; attempts to list it as an endangered species have been rejected because there are no confirmed data from published surveys across its entire range.
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Locally, the colony on Chews Ridge was studied in 2011-2012 by a team of locals and students and staff at UOP Stockton; this study has been published.
Surveys
Survey Results
small numbers seen most years on the Hastings June Butterfly count, but not this year; this is likely a result of the late phenology due to record-heavy winter-spring rains.
no surveys in July 2023
Recommended sites
Chews Ridge Fire Lookout - park at the gate to the lookout and MIRA observatory; search the lookout for hilltoppers and the surrounding woods for nectar-feeders on Monardella and thistle