The wingspan is 36–44 mm.[2][3] Forewing drab grey, suffused brown, except along costa and inner margin, and in an oblique pale fascia-form submarginal area;the pale submarginal fascia externally throw's off pale teeth; a long black streak from base below cell: median vein white, with only a small white spot at end of cell and a minute black point above it: veins whitish with black terminal streaks in the intervals:hindwing dark greyish, fuscous. - ab. suffusa Tutt is a melanic brown form common in Britain, occurring, but rarely, in the Alps; — ochracea Tutt is a brownish ochreous form, also rare, apparently, on the continent.[4]
Figs 1 larva about halfgrown 1a larva after last moult
Biology
The moth flies from May to July, with a second brood in August–September in southern parts of its range.
Larva reddish brown, with scattered black clots: dorsal and subdorsal lines black and fine; venter paler;thoracic plate black with 3 white lines; head brown. The larvae feed on various plants growing in sandy places, including dandelion and plantain.[3][5][6]
The English vernacular name refers to the only distinctive marking on the moth, a pair of white dots outward of the center of the forewing resembling a colon or joined into a > shape.
^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
