About Hadena caesia (Denis & Schiffermüller), 1775
Technical description and variation: The wingspan of Hadena caesia measures 32–37 millimetres (1.3–1.5 inches). The forewings are blue-grey with a furry appearance, which is caused by a dusting of dusky grey scales. Both forewing folds are tinged with fulvous yellow-brown. Lines and markings on the forewings are often indistinct. The upper stigmata are pale, with yellow scales along their circular outlines. There is a dark antemedian band that widens toward the inner margin, plus a less prominent dark submarginal cloud. A small dark blotch appears at the middle of the forewing costa. The hindwings are dark fuscous, and paler toward the base. The form manani Gregs, found on the Isle of Man and the Irish coast, is uniformly darker slate-coloured. The aberration nigrescens Stgr, found in the Pyrenees, Alps, and mountains of Scandinavia, is much darker, with the forewing suffused with black. In contrast, the taxon now recognized as the full species Hadena clara Stgr, from Armenia and Asia Minor, has greyer forewings with a pinkish tinge, and a paler median area.
