Overview of the Recognizable Io Moth

An Io moth lives in Eastern Canada and the United States, and is unique for its painful sting and prominent hindwing eyespots that serve to scare predators away.

Io Moth Species Summary

Scientific Name	Automeris io
Family Name	Saturniidae
Kingdom	Animalia
Genus	Automeris
Habitat	Deciduous forests, thorn scrub, and suburban areas
Range	The US and Canada
Host Plants	Hackberry, willow, mesquite, redbud, and blackberry
Butterfly Description	Bright yellow with a large blue and black eyespot on hindwings
Caterpillar Description	All instars change color, becoming brighter as they mature

What is the Io moth’s body like?

This stunning moth is one of the most recognizable moths out there.

The male Io moth is bright yellow, and you may often see it resting with its wings flat to the side of its back. However, once it feels threatened, this moth will open the forewings to reveal the large blue and black eyespot on its hindwings and tiny red-brown sections close to its body.

Adult Io moth females are more brown/rusty red on the upper side of their forewings. Female Io moths are also larger than males, but males have more feathery antennae.

Their wingspan is 2.5 to 3.5 inches (6.3 to 8.8 cm). Some hybridizations have caused variations among the hindwing eyespots.

Why is it called an Io Moth?

The Io moth got its name from Greek mythology, based on the woman Io, the first priestess of Hera. Io was actually Zeus’ mortal lover.

Io moth Larva Description

The Io moth has 5 larval instars. During the first instar, larvae are reddish-brown, with six longitudinal rows of spines. The second, third, and fourth instars are leaning towards yellowish color and as they grow, they’ll become lighter and lose the urticating bristles.

They may reach up to 2.7 inches (7 cm) in length. Once they’re ready to move onto the next life stage, they’ll form a flimsy dark cocoon made of silk among the leaf litter, protected crevices, or living leaves.

The pupa is dark brown, almost black. The pupae also show sexual dimorphism, where females are significantly larger than males.

What is the lifespan of an Io moth?

Egg Stage	1 to 3 days
Caterpillar Stage	28 days
Chrysalis Stage	7 to 10 days
Butterfly Stage	7 to 14 days

Where are Io moths found?

Io moth prefers deciduous forests and thorn scrub. It can also be found in suburban areas.

Like many other saturniid moths, the Io moth is less common today. It was abundant in England and its populations in the Gulf States have declined since the 1970s. Today, the Automeris Io moth lives in Canada and some parts of the US.

Usual Host Plants

Female Io Moths lay small white eggs on the following host plants:

What does the Io moth eat?

Like other moths of North America, the adult Io Moth doesn’t have a mouth, so it doesn’t feed. Still, the caterpillar eats various plants — grasses, shrubs, deciduous trees, and conifers. They’re most commonly found on sassafras. Their favorite food plants include, but aren’t limited to:

Behavior

Adult moths emerge from their cocoons in the late morning or early afternoon and stay still until evening. The emergence usually occurs from June to July. Once they’re out, they’ll hang on plants for about 20 minutes, waiting for their wings to start working.

These moths are nocturnal, flying during the peak hours of the night. The females will wait for the night and then extend a scent gland from their posterior region to attract males via pheromones. The males will detect them via their antennae. These moths don’t live long — after mating and laying eggs, the females die.

In some areas, such as Canada, these moths are single-brooded. On the west, they’re double-brooded, depending on the weather. In Florida and southern Texas, these moths make up to four broods.

Both males and females are attracted to light and fly around when the temperatures are above 45 F (7 C). Females usually won’t fly until after mating.

Io Moth predators

Unfortunately, Io Moths have many predators, such as birds, small mammals, insects, and spiders. Hornets will often attack their larvae and flies and wasps are common parasitoids. This is likely why caterpillars of all instars have evolved to sting. Their white stripe and spines may repel some insect predators as well.

Furthermore, the Io Moth is also a great example of “startle” coloration. The adults are often camouflaged, but will quickly react when disturbed. They’ll open their wings and show their eyespots to scare predators away.

Does the Io moth caterpillar sting?

The caterpillar’s stinging spines have painful venom that’s released as soon as something touches them. They even cause skin irritation in humans if touched.

Are Io Moths Endangered?

This moth isn’t listed on the IUCN Red List or the US Federal List. It is one of the most widespread Saturniidae species in North America and has high adaptability.