How to identify an io moth
The io moth has a wingspan of roughly 2 to 3.5 inches, smaller than luna or polyphemus. Males have vivid yellow forewings; females are larger and rusty reddish-brown. The real signature is on the hindwings: a single big eyespot on each, blue-and-black with a pale outline, normally tucked out of sight beneath the forewings. When a bird or other threat gets close, the io snaps its forewings forward to flash those staring eyes, a startle display meant to buy a moment's escape. The feathery antennae are most developed in males.
Where the io moth lives
The io moth ranges widely across the eastern and central United States, from the Northeast south to Florida and west into Texas and the Plains. In open records it is reported most often in Texas, Florida, New York, West Virginia, and Virginia. It turns up in deciduous woods, fields, suburbs, and brushy edges where its many host plants grow.
When io moths fly
In open observation records io moth sightings peak in June. In the warmer South the season stretches longer and can include more than one brood, while in the North the flight is concentrated in early summer. A warm, calm June night is a reliable time to watch for one at a light.
Caterpillars, host plants, and life cycle
The caterpillar is the part to respect. Io caterpillars are pale green with a reddish-and-white stripe along each side, and they are covered in clusters of branching spines. Those spines are urticating: brushing against them can deliver a painful, nettle-like sting, so do not handle them. The caterpillars feed in groups when young on a very broad range of plants, including willow, hibiscus, redbud, blackberry, corn, and many other trees and shrubs. They pupate in a thin papery cocoon in leaf litter. The adult that emerges has no working mouthparts, never eats, and lives only about a week to mate.
How to see an io moth at night
Io moths come to artificial light like other silk moths, and ultraviolet outperforms white LED. The leading explanation is that bright lights disrupt a moth's flight orientation: moths try to hold a natural light such as the moon at a fixed angle, and an artificial bulb scrambles that. To look for one, set up a white sheet with a UV or mercury-vapor lamp on a warm, windless June night and check it through the first hours of dark. New to this? See mothing for beginners, and compare with another eyespotted silk moth, the polyphemus moth.