Story Behind the Science
Io moths are noted for their woodsy coloring and methods of defending themselves against predators. Adult male io moths have mostly yellow coloring of their wings, while females usually have brown forewings. There are variations in color by species, including yellow to tan, reddish brown or purplish red hues.
In addition to the variation in coloration, io moths have bold, large “eyespots” on their hindwings. These moths have a wingspan of between 2 and 3 ½ inches. They are most common in eastern North America and occupy a variety of habitats, though they are most common in forests and park-like areas.
Io moths have relatively short life spans once they have become adults and left their cocoons. They are active at midday, mate in the evening and die soon after.
Io moths and its Saturniidae family, also known as the family of “Giant Silkworm Moths,” are not a very threatened group, which may be due to their many predator prevention tactics. Io moths, like other Saturniidae, use a natural strategy called startle coloration to defend themselves against predators. Io moths usually camouflage well with their surroundings, but when they’re startled, they spread their wings and display the large, round spots on their hindwings that resemble eyes. These “eyespots,” as they’re often called, warn off potential predators because they are mistaken for the eyes of a larger animal rather than the wings of a moth.
These moths are great at defending themselves, even as caterpillars. Mature io moth caterpillars use their “stinging” spines, a process that is scientifically known as urticating, as a defense mechanism to fight off predators. When touched by these spines, also known as setae, the caterpillar’s poison glands are stimulated, resulting in the release of poison into the area where the predator’s skin is punctured. Adult io moths do not have this capability though.
Did You Know?
- Silkworm moths are not in the same family as the mulberry silkworms that are used to create silk for clothing.Learn More »
- The Io moth’s name is derived from multiple sources. One of Jupiter’s largest moons is called Io and was named after a character related to moons in Greek mythology.Learn More »
- As young caterpillars, io moth larvae tend to feed in groups by forming long “trains,” but as they mature, the older caterpillars usually feed alone.Learn More »
- Female silkmoths release perfume-like pheromones that male silkmoths detect with their feathery antennae. These pheromones are released at a specific time of night, called a “calling time,” that signals specific moth species in order to prevent attracting the wrong mate.Learn More »
- Luna moths, a kind of silkmoth, are popular because of their beauty. The Luna moth first appeared on a first class U.S. postage stamp in 1987, was featured on the cover of "A Field Guide to Moths of Eastern North America" and is currently used in TV commercials for the sleep-aid drug Lunesta.Learn More »
|Compare & Contrast||Io Moths||Saturniidae (Giant Silkworm Moths)|
|How many species?||Over 200||Around 1,500|
|Where do they occur?||Most common in eastern North America, including Canada, and as far south as Costa Rica||Worldwide with the largest number found in tropical and subtropical regions|
|What do they eat?||Io moth caterpillars eat a wide variety of plants, including clover and grasses, as well as the leaves of crops and trees. Some popular host trees include apple, cherry, hickory, maple, and oak.||As caterpillars, they feed on the foliage of a variety of trees and shrubs. As adults, they do not feed because they do not have mouths.|
|Do they have predators?||Io moth cocoons are often preyed upon by birds, mice and other animals. As caterpillars, these insects may have predators that are often deterred by their poisonous spines.||Insects and other general predators are common, and cocoons are most susceptible to attack by woodpeckers, squirrels and wasps. Owls and bats are common predators of these creatures as well.|