Singly and in pairs, these moths preceeded us as we walked along Road F, in the grassland just past Trail 15. This tropical species is intolerant of cold weather, and was extirpated from most of the Bay Area during the extreme cold wave of Christmas week 1990; it is only known for certain to have survived on San Bruno Mountain, from where it recolonized the Bay Area. (Shapiro & Manolis, Field Guide to Butterflies of the SF Bay and Sacramento Valley Regions, Univ of Cal Press, 2007)