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Binomial name: Automeris io (Fabricius, 1775)
Common name: Io moth
Geographical range: Canada; United States (Georgia, Florida, Montana, North Dakota, South Dakota, Nebraska, Colorado, New Mexico, Texas, Utah); arguably Central America (Mexico, Costa Rica) although it is subject of discussion if the variations encountered there are subspecies of io or their own species. (neomexicana, draudtiana, potosiana, siri, et cetera).
Host plants: Extremely polyphagous, with over hundreds recorded food plants. Favorites include cherry (Prunus), redbud (Cercis), willow (Salix), Wisteria, Sassafras, currant (Ribes), Hibiscus but they have also been recorded on hickory (Carya), poplar (Populus), pear (Pyrus), limetree (Tilia), elm (Ulmus), fishpoison tree (Piscidia piscipula), oaks (Quercus), blackberry (Rubus), maple (Acer), birch (Betula), tuliptree (Liriodendron), Gleditsia, privet (Ligustrum), ash (Fraxinus), hazel (Corylus), beech (Fagus), corn (Zea mays), bamboo (many Poaceae), coral bean (Erythrina), hop (Humulus lupulus), walnut (Juglans), sweetgum (Liquidambar); and many more species of deciduous trees and shrubs, more than could be possibly compiled into one list. The food preference of the larvae may vary regionally througout their expansive range.
Habitat: Suburban areas, deciduous forest, shrubbery in grasslands, parks, agricultural area
Wingspan: 45mm-85mm – males smaller than females
Flight time: Varies geographically. The northernmost populations have one generation a year while the most southern populations have three to four generations a year and seem to be continuously brooded. It is likely that the diapause is induced by the local climate and that Automeris io will produce continous generations if provided sufficient warmth and sunlight; as the local climate gradually becomes much colder towards the northern parts of their natural range, their life cycle is gruadually inhibited to the point of producing only one or two generations. Moths are active in the late evening/night.
Ecology: Found in a variety of habitats such as suburban areas, decidous forests, shrubbery in grasslands; very polyphagous so can survive in a wide array of habitats. The females passively wait for males to arrive that are willing to copulate with her. This species is considered nocturnal, although their activity actually starts in the late evening. After pairing the female becomes slightly more active, and she will look for a suitable place to deposit 50 to 250 pale white, oval eggs. Fertile eggs develop a clear black dot (micropyle). Moths do not feed and are short lived (7 to 14 days). The eggs hatch in 2 to 3 weeks time and the social larvae will stay together after hatching, feeding from various trees, grasses and shrubbery. The caterpillars are green to yellow and have venomous spines that can deliver a painful sting upon skin contact. While social at first, as the caterpillars grow older they will become more solitary. When fully grown, caterpillars spin papery brown cocoons between plant leaves, in crevices or forest floor litter. Depending on the season and geographical location, the cocoons will decide to hatch in a few months or overwinter. In the most southern warm localities this species does not overwinter at all and has 3 to 4 generations in one year, while the environment in the most northern populations in cold localities only permits them to have one generation a year, always overwintering as cocoons until the next spring.
Description adult: Males bright yellow; the entire body, legs, abdomen, antennae and thorax are yellow. In some cases the males can be orange. The forewing is decorated with brown/blackish dots and stripes. Females have brown wings. The hindwings of both sexes are yellow and have bright eyespots that are revealed if the moth is disturbed; when resting the forewings are held over the hindwings. These eyespots have a blueish center surrounded by a black ring, looking very much like a pupil and are surrounded by a black and a red/orange margin.
Description larvae: The final instars are bright green or in more rare cases yellow and are covered with sharp branching spines that can inject venom. Along their side a red stripe runs from the front to their rear end and inside this stripe a secondary pale white stripe can be seen. Young caterpillars are orange to yellow. As the caterpillars mature they become more colourful. Automeris io caterpillars are social and often live in groups and can be seen covering the food plants together, although they become more solitary with each instar.
Diapausal state: This species overwinters in the cocoon stage. Although if kept warm, the cocoons will always hatch; their emergence is inhibited by temperatures. This is evident in warm (sub)tropical climates where they can be continuously brooded.
Similar species: In North America it is the only species with bright yellow males (although they can be dark and orange in some regions, such as Automeris io lilith from Florida). Automeris beutelspacheri, Automeris draudtiana, Automeris potosiana, Automeris dandemon,
Dimorphism: Males are small and yellow (or in some cases orange); females are larger
Health information: Larvae are urticating with venomous spines; although not considered dangerous skin contact with them may hurt. Allergic people are at risk.
Fun fact: The population in Florida is unique and may have bright orange males; a colour form known as Automeris io lilith.
Other media: Video available (click here)
Photography: All specimens photographed here were part of a captive breeding experiment in the Netherlands (Europe) and are live specimens. Although captive livestock does not look very different from wild animals, they are not wholly representative of wild animals since captive livestock is prone to exhibiting unnatural variations and sizes. I am a moth breeder from the Netherlands that has bred hundreds of species. This website only features the imagoes of Lepidoptera I photographed and not the early life stages.
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