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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.

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.  

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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

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