American idia moth
As caterpillars, American idia moths eat lichens growing on tree bark rather than leaves, an unusual diet for a moth of its family.
| Where | Moist forests and tree trunks |
|---|---|
| Size | 20 to 30 mm wingspan |
| When | May to October |
The American idia has dull grey to reddish brown forewings that darken toward the outer edge, crossed by irregular dark lines that form bars along the leading edge. A light grey spot filled with ochre yellow and reddish brown sits near the center of each forewing, and the hindwings are a paler grey with similar wavy lines.
Caterpillars feed on lichens growing on tree trunks and stone surfaces rather than on leaves, an uncommon habit among moths. Adults fly at night from spring through autumn and are drawn to light.
Traits
Habitat
Woodland
Colour
Grey, Brown, Orange
Active
Night
To people
Comes to lights at night but does not bite or sting; harmless to people.
Activity through the year
Often confused with
Very similar in size, but a more uniform dull grey overall, without the reddish brown tones and darker outer margin of the American idia moth.
Questions
Is the American idia moth dangerous to people?
Comes to lights at night but does not bite or sting; harmless to people.
When can you see the American idia moth?
The American idia moth can be seen from May to October, at night.
Plate retouched from a photo by Susan Blayney, CC BY 4.0, iNaturalist Licence
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Butterflies and moths›Erebid moths›Idia
Last updated 2026-09-27. Every entry is checked against published sources.