Mythimna ferrago, the clay, is a moth of the family Noctuidae. It is distributed throughout Europe and is also found in Morocco, Algeria, Turkey, Asia Minor, Armenia, Syria, Turkestan, Israel, Lebanon, Iraq, Iran, Central Asia and the western parts of temperate North Asia. Also Tibet.
The forewings of this species vary from buffish to orangey brown, usually with a darker central line running longways down the wing, interrupted by a pale stigma. There are usually a few small dark spots in the basal area. The hindwings are dark grey with paler margins. The male is easily recognizable by a triangular area of black hair on the underside of the abdomen. The wingspan is 36–44 mm. This moth flies at night in July and August  and is attracted to light and sugar.
Technical description and variation
The wingspan is 36–44 mm. Forewing pale greyish rufous, speckled with dark;lines indistinct, dark grey; the outer regularly lunulate-dentate, the teeth marked by black dashes on veins;reniform stigma obscure, ending in a cloudy pale spot at lower end of cell; hindwing greyish ochreous; ventral tufts black. The species varies in coloration: ferrago F. is the reddest form: - grisea Haw, is grey without any rufous admixture, with the markings generally clearer; fulvescens Tutt is rare, with fulvous in the place of red; — ab. marginata Tutt has silvery grey hindwings with broad dark border.
The larva, brownish yellow; dorsal line white; lateral lines broad, whiter, containing the black spiracles, feeds on various grasses including Deschampsia. The species overwinters as a small larva.
- Chinery, Michael. (1986; 1991). Collins Guide to the Insects of Britain and Western Europe
- Skinner, Bernard. (1984). Colour Identification Guide to Moths of the British Isles
- Seitz, A. Ed., 1914 Die Großschmetterlinge der Erde, Verlag Alfred Kernen, Stuttgart Band 3: Abt. 1, Die Großschmetterlinge des palaearktischen Faunengebietes, Die palaearktischen eulenartigen Nachtfalter, 1914
- "Robinson, G. S., P. R. Ackery, I. J. Kitching, G. W. Beccaloni & L. M. Hernández, 2010. HOSTS – A Database of the World's Lepidopteran Hostplants. Natural History Museum, London".
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