Io moth
This moth's caterpillar carries hollow, branching spines that snap off under the skin, and every larval stage delivers the same stinging defense.
| Where | Forests, woodlands and parklike areas |
|---|---|
| Size | 51 to 88 mm wingspan |
| When | April to October |
Male Io moths have yellow forewings while females are brown to purplish red, and both reveal a large blue and black eyespot on each hindwing when the forewings snap open. At rest the plain outer wings make the moth blend into leaf litter until it is disturbed.
Caterpillars are pale green with a red and white stripe and carry clusters of branching spines that break off in skin on contact. They feed on a wide range of trees and shrubs, including sassafras, willow and maple, before pupating in a papery cocoon spun among leaves.
Traits
Habitat
Woodland
Colour
Yellow, Brown, Blue
Active
Night
To people
Take care
Caterpillars sting on contact and cause burning pain and swelling that fades within hours; adult moths do not bite or sting.
Activity through the year
Often confused with
Much larger, about 89 to 150 mm across, with a yellow hindwing eyespot ringed in blue and black with a transparent center, unlike the Io moth's solid blue and black spot.
Questions
Is the Io moth dangerous to people?
Take care. Caterpillars sting on contact and cause burning pain and swelling that fades within hours; adult moths do not bite or sting.
When can you see the Io moth?
The Io moth can be seen from April to October, at night.
Plate retouched from a photo by Trevor Edmonson, CC BY 4.0, iNaturalist Licence
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Butterflies and moths›Emperor moths›Automeris
Last updated 2026-09-26. Every entry is checked against published sources.