Treble lines
Treble lines caterpillars feed hidden at ground level, chewing through the stems of plantain and knapweed rather than eating leaves out in the open.
| Where | Woodland edges and rough grassland |
|---|---|
| Size | 33 to 40 mm wingspan |
| When | May to June |
Treble lines is a pale ochreous brown moth named for the three fine dark brown lines that cross each forewing from the leading edge toward the inner margin. The hindwings are darker grey brown with a pale fringe, and the wingspan measures about 33 to 40 mm.
Caterpillars feed at night on plantain and knapweed, living just beneath the soil surface and pupating underground once fully grown. The single yearly generation of adults flies at night over woodland edges, hedgerows and rough grassland, coming to light and to sugar bait.
Traits
Habitat
Grassland
Colour
Brown, Grey
Active
Night
To people
Comes to light and sugar bait after dark; harmless to handle.
Activity through the year
Often confused with
Similar in size at 34 to 37 mm, the dusky sallow has a single broad whitish central band across the forewing rather than three separate fine lines, and it flies later, in high summer.
Questions
Is the Treble lines dangerous to people?
Comes to light and sugar bait after dark; harmless to handle.
When can you see the Treble lines?
The Treble lines can be seen from May to June, at night.
Plate retouched from a photo by Ben Sale from Stevenage, UK, CC BY 2.0, Wikimedia Commons Licence
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Butterflies and moths›Owlet moths›Charanyca
Last updated 2026-09-26. Every entry is checked against published sources.