About Nycteola revayana (Scopoli, 1772)
This entry covers the technical description and morphological variation of Nycteola revayana (Scopoli, 1772), also referenced as S. revayana Scop. The typical form has ashy grey forewings dusted with darker scales, most densely in the costal half of the median area. Its darker double lines are indistinct. The inner line curves outward above and below the middle, and angles outward below vein 1. The outer line is irregularly waved and strongly indented on the submedian fold. A few faint dark spots mark the position of the submarginal line. The hindwing is pale greyish fuscous. The aberrant form fusculana Schmid has a dull dark brownish fuscous ground colour, with visible black lines and a ferruginous spot that represents the reniform stigma. An oblique black streak runs from the middle of the base to the lower end of the inner line. Submarginal spots are visible, paired with a row of small black marginal lunules. Aberrant form dilutana Hbn. has a dull grey or whitish grey ground colour, with a brownish grey median area that is more purely brown toward the costa. The reniform stigma is diffuse and rufous. The pale basal area holds grey spots between veins in the space between the subbasal and inner lines. Submarginal spots are darker grey, and the pale submarginal line beyond these spots is more clearly marked. Aberrant form degenerana Hbn. is bright greenish white, with a purplish grey and brown median area that is darker black toward the costa. Its reniform stigma is purple red. The lines are filled with white, and cloudy spots in the basal and marginal areas are black. There is a black spot at the apex, and the fringe is whitish. Intermediate forms occur between degenerana and dilutana. The new aberrant form obscura has an entirely olive brown forewing, with the same markings seen in degenerana. Aberrant form glaucana Lampa has obscurely glaucescent forewings, with a triangular dark fuscous blotch. Aberrant form ilicana F. (equivalent to punctana Hbn.) is pale fawn grey, sprinkled with whitish scales. Its lines are much finer. The cell spot, a spot on each side of the median vein before the inner line, and the two lowest spots of the submarginal line are black. In aberrant form ramosana Hbn. (equivalent to ramulanus Curt.), the ground colour is brownish grey with fuscous shading. A deep black streak extends from below the base of the cell to below the reniform stigma, branching shortly toward the inner margin beyond the subbasal and inner lines. Submarginal spots are darker. Aberrant form russiana Dup. has grey green forewings with a large dark median blotch. The larva is green with yellowish segmental incisions, and its tubercles bear long white structures. The wingspan of this species ranges from 20 to 25 millimetres (0.79–0.98 in).
