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Adults of adumbrata are medium-size (3.4-4.0 cm wingspan) rather narrow-winged noctuid moths. The sexes are dimorphic; females are dark blackish-brown and males red-brown. Females are essentially unmarked except for pale scales outlining the reniform and orbicular spots. Males are almost identical to red specimens of Euxoa ochrogaster, and to a lesser degree to Euxoa mimallonis. The male genital characters mentioned above will separate adumbrata from the others. Males of mimallonis also have shining white hindwings, not dirty white or sooty as in adumbrata. The male genital characters can be observed in most specimens without dissection. The Sordid Dart belongs to the Euxoa subgenus Chorizagrotis, characterized by long, apically spatulate saccular extension and short harpes in the male. The only other member of the subgenus in Alberta is E. auxiliaris, which can be separated by its shorter harpes (3 times as long as wide in auxiliaries versus 5 times as long as wide in adumbrata). Females of Chorizagrotis may be separated from females of other Euxoa subgenera by their dorsoventrally flattened abdomen. Keys to the adults of the genus, subgenera and species are provided in Lafontaine, 1987. The nomenclature of adumbrata has gone through a number of changes in recent years; it has been treated as both drewseni (Staud.) and lidia (Stoll) (Hardwick, 1970; Lafontaine, 1987).

Holarctic. In North America adumbrata occurs across northern Canada from Quebec to western Alaska, south to the northern tier of states, and in the mountains to Colorado. In Alberta it has been collected throughout the southern half of the province.