♂︎♀︎. 3+1⁄4"-3+1⁄2". Head, antennae, and thorax dark fuscous. Palpi whitish at base, second joint with two whorls of dark fuscous white-tipped scales, terminal joint black with two white rings. Abdomen blackish-fuscous, beneath silvery-whitish. Legs dark fuscous, middle and posterior tibiae with white central and apical rings, all tarsi with white rings at apex of joints. Fore-wings elongate, very slightly dilated, hind-margin indented beneath apex; basal and apical thirds dark fuscous, densely strewn with whitish scales, central third bronzy-ferruginous, more or less broadly suffused with dark fuscous on costa and inner margin; a white oblique costal streak at 1⁄3, reaching middle, ending in a leaden-metallic spot; an indistinct white spot on inner margin near base; two outwardly curved steel-blue metallic fasciae ending in white spots on both margins, first hardly before, second beyond middle; beyond these are three white spots on costa, the first two giving rise to obsolete metallic streaks, the last sub-apical, sending a steel-blue metallic streak to hind-margin below apex; a blackish spot on apex; cilia whitish, fuscous-grey at apex and anal angle, basal half separated by a strong dark fuscous line, and clothed towards base with ferruginous scales, except where a wedge-shaped dark-margined white indentation meets the sub-apical streak. Hind-wings and cilia dark fuscous-grey.[2]
G. euastera is a day-flying moth.[7] This species is on the wing between October and January.[3] It is a leaf mining moth.[10]
Host plants and habitat
The host species of the larvae of G. euastera is unknown although it is likely that it is a sedge or grass.[6] It is believed that the species is associated with Poa cita (silver tussock).[9] The preferred habitat of this species is short tussock grassland ranging in altitude from sea level to 1,280 metres (4,200 ft).[6]
^ abcPawson, Stephen M.; Emberson, Rowan M. (2000). The conservation status of invertebrates in Canterbury (Report). Department of Conservation. pp. 45–46. hdl:10182/1658. ISSN1171-9834.