Muir's Hairstreak (Callophrys muiri) nectaring on Western Wallflower (Erysimum capitatum)
Photographed in The Cedars (near Cazadero) on 8 April 2016
Note the greenish sheen, especially on the hind wing. This is a feature I looked for last year (see post from 29 April 2015), but missed. It was nice to see it!