Appearance
The adult's wingspan is 18–21 mm; in their core range they can be seen between April and November, but in outlying regions they may only be regularly encountered in late summer and early autumn, when vagrant individuals abound. This species is strongly sexually dimorphic: males are light brown with a wavy pattern of whitish lines and a broad darker band running across the wings, forming concentric semicircles when the moth is at rest. There is a small whitish-rimmed black spot within the darker band between the center and the leading edge of each forewing. The females are slightly larger and much darker, almost uniformly blackish-brown with an indistinct lighter pattern and a forewing spot like the males have.
Naming
Under its junior synonyms ''Nycterosea brunneipennis'' and ''Geometra fluviata'', the Willow Beauty is the type species of genera ''Nycterosea'' and ''Percnoptilota'', respectively. The latter is treated as junior synonym of the former, but ''Nycterosea'', though usually included in ''Orthonama'' these days, may warrant recognition as an independent genus after all.
Habitat
The adult's wingspan is 18–21 mm; in their core range they can be seen between April and November, but in outlying regions they may only be regularly encountered in late summer and early autumn, when vagrant individuals abound. This species is strongly sexually dimorphic: males are light brown with a wavy pattern of whitish lines and a broad darker band running across the wings, forming concentric semicircles when the moth is at rest. There is a small whitish-rimmed black spot within the darker band between the center and the leading edge of each forewing. The females are slightly larger and much darker, almost uniformly blackish-brown with an indistinct lighter pattern and a forewing spot like the males have.The caterpillar larvae feed on a wide range of low-growing core eudicots, but prefer asterids. Host plants recorded from the Central European part of its range include:
Euasterids I
⤷ Gentianales: Rubiaceae
⤷ * ''Galium''
⤷ Solanales: Convolvulaceae
⤷ * ''Convolvulus''
Euasterids II
⤷ Asterales: Asteraceae
⤷ * ''Anthemis''
⤷ * ''Chrysanthemum''
⤷ * ''Eupatorium''
⤷ * ''Senecio'' – e.g Common Groundsel in the British Isles
Eurosids II
⤷ Brassicales: Brassicaceae
⤷ * ''Alyssum''
⤷ * ''Nasturtium''
Basal core eudicots
⤷ Caryophyllales: Polygonaceae
⤷ * ''Polygonum''
⤷ * ''Rumex''
References:
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