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A medium-size (3.3-3.8 cm wingspan) moth with powdery grey forewings and white hindwings. The dark grey forewings are crossed by the black antemedian and postmedian lines, while the subterminal line is marked by lighter grey on a black background. The orbicular and reniform are usually well marked, finely outlined with black scales and with dark centers. Hindwing is shining white with a faint discal dot and postmedian band and a fine black terminal band. There is a small patch of dark scales at the anal angle. Males are smaller than females and have bipectinate antennae (simple in females). The closely related R. coloradensis has paler grey and light tan forewings with contrasting black patches near the base and along the lower half. See also Acronicta species, most of which are lighter grey in color.

No Alberta data; elsewhere in Canada poplars, in particular Trembling aspen (Populus tremuloides) and Balsam poplar (Populus balsamifera). Other hosts recorded much less frequently include willow (Salix sp.), White birch (Betula papyrifera) and speckled alder (Alnus rugosa).

Nova Scotia west, across the forested regions of Canada to British Columbia, south to Mississippi in the east. The southern limits in the west are uncertain due to confusion with several closely related species or forms. In Alberta, they are found throughout the Aspen parklands, the Boreal forest north to Lake Athabasca and the foothills and lower elevations in the mountains. They are replaced in the wooded valleys or the grasslands region by the closely related R. coloradensis.