The forewings of this species are reddish brown with distinctive patterning towards the base: a black mark resembling the Hebrew letter Nun: נ with a pale cream coloured area adjacent to this mark. The hindwings are cream coloured. The wingspan is 35-45 mm. Two broods are produced each year and the adults are on the wing between May and October. This moth flies at night and is attracted to light and sugar as well as flowers such as Buddleia, ivy and ragwort.
The larva is pale brown or green with black spots. It feeds on a huge variety of plants (see list below). The species overwinters as a larva.
A fictional story of how a moth received the letter "nun" can be found at http://www.flwildflowers.com/moth