About Tetheella fluctuosa (Hübner, 1803)
Tetheella is a monotypic moth genus in the family Drepanidae, first described by Werny in 1966. This genus contains only one species: Tetheella fluctuosa, commonly known as the satin lutestring, which was originally described by Jacob Hübner in 1803. This species is found across the Palearctic region, ranging from western Europe east to Kamchatka, Sakhalin Island, Korea, and Japan. The wingspan of adult Tetheella fluctuosa measures 35–38 mm. The forewings are light fuscous in color, sprinkled with white. A whitish first line marks the edge of a broad darker central band, which contains dark fuscous median and second lines. This band is followed by a waved whitish line with a dark edge. The subterminal line is whitish and waved, and is preceded on the costa by an oblique dark fuscous dash. The hindwings are grey, and have a pale postmedian line. Fully grown larvae are yellowish whitish, with fuscous dorsal, fine subdorsal, and lateral lines. The larval head is reddish-ochreous with brown markings. Adult moths fly from June to August, with flight timing varying by location. The larvae of this species feed on birch and alder plants.
