A medium-size (3.6-4.2 cm wingspan) grey-black moth with a silvery sheen in fresh specimens. Forewings are mottled pale grey in the basal and subterminal areas, with dark blackish-brown in the lower median area and along the subterminal line. The antemedian and postmedian lines and the area below the stigma are dark red-brown. Stigma is silvery white, forming an outward curving arc with a rounded tip and with a widely separated fork at the upper end. About one-third of the way down the subterminal line is a black dash which connects the subterminal and postmedian lines. This black dash is diagnostic and will separate californica from the very similar A. pseudogamma. Hindwings are dark sooty brown-black, paler in the basal half and shading into a wide dark terminal band. The antennae are simple and both the sexes are alike.