Unknown species. Flew like a moth, but I don't believe it was. Probably a skipper.
San Bruno Butterfly Count
Pollinating the bitterweed.
Pyrgus is a genus in the skippers butterfly family, Hesperiidae, known as the grizzled skippers. The name 'Grizzled Skipper' best describes this genus, but in some countries the name 'Checkered Skipper' or 'Chequered Skipper' is applied to some species. Strictly speaking, 'chequered skippers' applies to butterflies of the genus Carterocephalus.