Common Name: Gray Marble, Boisduval's Marble
Fairly common on the Sierran West slope in rocky canyons and moist forest. Local in the North Coast Range and on the East slope of the Sierra, usually in rocky canyon sites. Resembles (and easily confused with) the Gray-Veined White in flight; probably underreported. The female is larger than the male, with broader wings and a more complete dark patrtern at the apex; otherwise similar.
The genus Anthocharis is Holarctic ; there are related species in the eastern United States, Mexico, Europe and East Asia.
One brood, late April-July; mostly 2000-6000' but occasionally higher and lower. Host plants native Brassicaceae, generally tall species, especially Tower Mustard (Arabis glabra) and tall species of Jewel Flower (Streptanthus). The larva eats both leaves and buds/flowers/fruit. Adults visit a variety of flowers, including Brassicaceae, especially Western Wallflower (Erysimum capitatum), which is NOT a host; Blue Dicks; Yerba Santa, mints, etc.
The name "Gray Marble" is somewhat unfortunate, as the underside mottling is in fact a rich burgundy red, at least when fresh.