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A medium size moth (approx. 3 cm wingspan; females larger than males). Forrwings grey with few markings, consisting of a darker antemedian and erratic postmedian line, usually poorly marked. The reniform is usually indicated by a dark dot or bar bordered by pale scales. Hindwings pale orange-buff with a wide black border, and with the buff largely suffused with grey in many specimens. Body densly wooly-hairy, dark grey. Male antennae plumose; female simple. The illustrated specimen (from the Caribou Mnts of Alberta) is freshly emerged and unusually well marked.

Reported larval hosts included species of Saxifrage and willow; possibly also Potentilla (Handfield, 1999). Willow buds are favored at some arctic sites. The Alberta larva was collected on Rubus acaulis and was reared in the lab on R. idaeus. The larvae may take multiple years to complete development, and females can produce fertile eggs without mating. The larvae are covered in dense soft grey hairs, and the cocoon is a grey oval with the larval hair incorporated into it. Adults are active during the day.

G. rossii has an Holarctic arctic-alpine distribution. In North America it occurs south in the east to ME and NH, west across the arctic and subarctic to Alaska and south in the Rocky Mountains to CO. Although it has never been collected in the Rocky Mountains in Alberta, a single larvae (which later produced a female moth) was found in the subarctic-boreal forest at Horseshoe Lake in the Caribou Mountains by Doug Macaulay.