This is a very distinctive species with very dark brown, almost black, forewings marked with a large white stigma from which the species gets its common name. The hindwings are grey with a dark band at the termen. The wingspan is 38-50 mm. It flies at night in July and August and is attracted to light, sugar and flowers.
The larva is rather variable in colour, being green, brown or even purplish. It is marked with lighter diagonal markings and has a distinctive hump at the rear end. It is polyphagous, feeding on a wide variety of plants (see list below). The species overwinters as a pupa.