Straw underwing
The Straw underwing hides plain dark forewings by day, but its pale straw-yellow hindwings, rimmed in black, flash into view only when the moth takes flight.
| Where | Grassland, moorland and open woodland |
|---|---|
| Size | 38 to 46 mm wingspan |
| When | July to September |
The Straw underwing has dark brown forewings mottled with paler and reddish patches and crossed by a whitish line near the outer edge. Its hindwings are pale straw yellow with a broad blackish border, a contrast that stays hidden while the moth rests with its wings closed.
Adults fly mainly in July and August, visiting light and sugar patches after dark across grassland, moorland, dunes and open woodland rides. Caterpillars feed low down on grasses, including annual meadow-grass and mat-grass, before pupating in the soil.
Traits
Habitat
Grassland
Colour
Brown, Yellow
Active
Night
To people
Comes to light and sugar at night; poses no known risk to people.
Activity through the year
Often confused with
Noticeably larger at 47 to 54 mm wingspan, with rich coppery orange hindwings rather than the pale straw yellow of the Straw underwing.
Questions
Is the Straw underwing dangerous to people?
Comes to light and sugar at night; poses no known risk to people.
When can you see the Straw underwing?
The Straw underwing can be seen from July to September, at night.
Plate retouched from a photo by gailhampshire from Cradley, Malvern, U.K, CC BY 2.0, Wikimedia Commons Licence
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Butterflies and moths›Owlet moths›Thalpophila
Last updated 2026-09-26. Every entry is checked against published sources.