A medium-size (3.3-3.7 cm wingspan) moth with brick-red forewings and black hindwings. The forewings vary in color in the same population from dull brown with rather prominent dark orbicular and reniform to deep brick red with black basal and subterminal bands (illustrated). The banded form of brunneipennis is unmistakable. Most brunneipennis have a deeper more saturated almost greasy-looking appearance. The markings on most specimens are faint or obsolete, with the dark shade at the top of the subterminal shade most prominent. They are very closely related and most likely to be confused with A. cupida, most specimens of which are lighter orange-red and have lighter black hindwings. Brunneipennis is associated with sandy habitats in the cooler boreal forest and foothills regions, while cupida frequents dry often clay habitats south of the boreal forests. Although bar-code sequence fails to differentiate between cupida and brunneipennis, there are significant differences in both the male and female genitalia. Lafontaine (1998) illustrates the various forms of adults and genitalia of both sexes.