Automeris io

Fabricius, 1775

Io moth, peacock moth

Species Guides

Automeris io neomexicana(Io moth)

Automeris io is a colorful North American saturniid with in coloration: males are bright yellow, females reddish-brown to purple. Both sexes possess distinctive eyespots on the hindwings used in anti- displays. The caterpillars are gregarious, bright green with red and white lateral stripes, and possess venomous urticating spines that cause painful stings. Adults are , lack functional mouthparts, and live 1–2 weeks. have declined in parts of their range, particularly in New England, due to loss and by introduced agents.

Io Moth (Automeris io) by Michael Hodge. Used under a CC BY 2.0 license.

Automeris.io by Luis Miguel Bugallo Sánchez (Lmbuga Commons)(Lmbuga Galipedia)

Publicada por/Publish by: Luis Miguel Bugallo Sánchez. Used under a CC BY-SA 3.0 license.

Automeris Io, last instar (2) by QueenOfFrogs. Used under a CC BY-SA 4.0 license.

Pronunciation

How to pronounce Automeris io: //ɔːˈtɒməˌrɪs ˈaɪ.oʊ//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

distinguished from similar saturniids by the combination of in color (yellow males, reddish-brown to purple females) and the single large eyespot on each hindwing. Males identified by ; females by simpler antennae and darker coloration. Caterpillars identified by bright green color with red and white lateral stripes and prominent venomous spines—distinctive among North American saturniid larvae. Pupae can be sexed by the presence of a notch (female) versus (male) on the aspect.

Images

Appearance

have a wingspan of 63–88 mm. Sexually dimorphic: males have bright yellow forewings, body, and legs; females have reddish-brown to purple forewings, body, and legs. Males possess much larger (feathery) than females. Both sexes have one large black to bluish eyespot with some white in the center on each hindwing. Caterpillars reach 7 cm in length, with bright green bodies, two lateral stripes (upper bright red, lower white), and numerous urticating spines. Pupae are dark brown to black; female pupae have a notch on the aspect, while male pupae bear a pair of in this area with no notch.

Habitat

Occurs in diverse including deciduous and mixed forests, woodlands, and suburban areas with plants. Found from sea level to moderate elevations. Larvae feed on a broad range of woody plants; specific host associations vary regionally.

Distribution

Eastern North America from the southeast corner of Manitoba and southern extremes of Ontario, Quebec, New Brunswick, and Nova Scotia in Canada. In the United States, ranges from Montana, North Dakota, South Dakota, Nebraska, Colorado, New Mexico, Texas, and Utah eastward across the eastern states to southern Florida.

Seasonality

emerge from cocoons in late morning or early afternoon, typically from June to July. Adults are strictly , flying during peak night hours. Females extend at nightfall to release . Single brooded in northern portions of range; may have partial second in southern areas.

Diet

Caterpillars are herbivorous and gregarious, feeding on leaves of numerous woody plants. Documented plants include: Morus alba (white mulberry), Prunus pensylvanica (pin cherry), Salix spp. (willow), Abies balsamea (balsam fir), Acer rubrum (red maple), Amorpha fruticosa (bastard indigo), Baptisia tinctoria (wild indigo), Carpinus caroliniana (American hornbeam), Celtis laevigata (sugarberry), Cephalanthus occidentalis (buttonbush), Cercis canadensis (eastern redbud), Chamaecrista fasciculata (showy partridge pea), Comptonia peregrina (sweetfern), Cornus florida (flowering dogwood), Corylus avellana (common hazel), Erythrina herbacea (coral bean), Fagus spp. (beech), Fraxinus spp. (ash), Liquidambar styraciflua (American sweetgum), Lythrum salicaria (purple loosestrife), Quercus spp. (oak), Paeonia spp. (peony), and Phoenix roebelenii (pygmy date palm). have mouthparts and do not feed.

Host Associations

Morus alba - larval food plantwhite mulberry
Prunus pensylvanica - larval food plantpin cherry
Salix spp. - larval food plantwillow
Abies balsamea - larval food plantbalsam fir
Acer rubrum - larval food plantred maple
Amorpha fruticosa - larval food plantbastard indigo
Baptisia tinctoria - larval food plantwild indigo
Carpinus caroliniana - larval food plantAmerican hornbeam
Celtis laevigata - larval food plantsugarberry
Cephalanthus occidentalis - larval food plantbuttonbush
Cercis canadensis - larval food planteastern redbud
Chamaecrista fasciculata - larval food plantshowy partridge pea
Comptonia peregrina - larval food plantsweetfern
Cornus florida - larval food plantflowering dogwood
Corylus avellana - larval food plantcommon hazel
Erythrina herbacea - larval food plantcoral bean
Fagus spp. - larval food plantbeech
Fraxinus spp. - larval food plantash
Liquidambar styraciflua - larval food plantAmerican sweetgum
Lythrum salicaria - larval food plantpurple loosestrife, introduced
Quercus spp. - larval food plantoak
Paeonia spp. - larval food plantpeony
Phoenix roebelenii - larval food plantpygmy date palm

Life Cycle

are laid in clusters of more than twenty on plant leaves, with large rosettes that turn black as embryos develop. Eggs hatch in 8–11 days. Larvae emerge orange, consuming their egg shells, and proceed through five instars. Early instars are gregarious and travel in single-file processions. Later instars turn bright green and develop urticating spines. Caterpillars spin flimsy, valveless cocoons of dark coarse silk—some at the base of trees among leaf litter, others wrapped in living leaves that brown and fall with the cocoon. Pupae overwinter in cocoons. emerge in late morning or early afternoon, requiring approximately 20 minutes to inflate wings with . Adult lifespan is 1–2 weeks. Females die after egg-laying.

Behavior

Caterpillars are gregarious throughout all instars, forming single-file processions on plants. are strictly , with females releasing from extended abdominal at nightfall to attract males. Males use enlarged to detect female pheromones. Both sexes employ a deimatic anti- display: when disturbed in -down position or touched, they shake and expose the large hindwing eyespots to startle predators.

Ecological Role

Caterpillars function as herbivores, consuming foliage of diverse woody plants. serve as prey for bats, birds, small mammals, and spiders. Subject to by tachinid flies (Compsilura concinnata, Lespesia spp., Chetogena claripennis, Carcelia formosa, Sisyropa eudryae, Nilea dimmocki) and ichneumonid and braconid wasps (Hyposoter fugitivus, Enicospilus americanus, Cotesia electrae, Cotesia hemileucae). The introduced Compsilura concinnata has been implicated in declines.

Human Relevance

Caterpillar stings cause painful, irritating erucism (acute dermatitis) due to venomous spines; not life-threatening but can cause significant discomfort and allergic reactions in sensitive individuals. are non-threatening and do not feed. Subject of scientific interest for anti- adaptations and phylogenetic relationships. declining in eastern North America due to loss and agents.

Similar Taxa

Automeris metzliSimilar with urticating caterpillars and eyespot defenses; distinguished by geographic range (Mexico to Ecuador, Trinidad) and specific associations including Erythrina and coconut
Antheraea polyphemusAnother North American saturniid with hindwing eyespots; distinguished by larger size, tan to brown coloration without in yellow/purple tones, and eyespots with central clear windows rather than solid black/bluish with white center
Eacles imperialisImperial moth overlaps in range and has colorful larvae; distinguished by lack of eyespots on hindwings and different larval coloration (green, brown, or orange with spines but without red and white lateral stripes)