Both the common and binomial names of this moth refer to distinctive black markings, one on each wing.

The size of the orbicular stigma is variable, and the amount and shape of the black filling in of the cell is determined by this variation; in ab.

the black markings are replaced by olive brown or rufous; it is a northern form, occurring in Scotland, Scandinavia and Finland, and in the Tarbagatai Mountains; askoldensis Stgr.

[now full species Orthosia askoldensis] from Amurland and Japan has a more violet-grey ground colour; ab.

The larva is green dotted all over with yellow; dorsal and subdorsal lines yellowish white; spiracular line broad, white, with dark upper edge; head pale green.