Myrtle’s Fritillary, also known Myrtle’s Silverspot, a subspecies of the Zerene Fritillary (Speyeria zereneSwainson) (see photo), was described in 1945, it was restricted to Pescadero Point in San Mateo County in California, USA.
The larvae are known to have fed on the Hookedspur Violet (Viola adunca Sm.).
Myrtle’s Fritillary was apparently last recorded around 1919 and is now considered extinct.
The taxonomic situation of this form, however, is not finally solved and thus it might be identical with another form, the Point Reyes Fritillary (Speyeria zerene ssp. puntareyes Emmel & Emmel), which is restricted to the southernmost Sonoma County of california, and which itself is highly threatened.