Adults of this species are considered medium to large-sized moths, with a wingspan of 5 to 9 cm. (Borror and White, 1970; Hossler, et al., 2008; Manley, 1978; Manley, 1993; Peterson, 1962; Russi, et al., 1973; Tuskes, et al., 1996)exhibits sexual dimorphism in its coloration. Male forewings are typically bright yellow, while females have dark yellow or brown forewings. Females may also have larger, more pointed forewings. Both males and females have large eyespots on their hindwings; the eyespots are black or blue, with a gray or bluish iris surrounding a white center. The eyespot is often larger and rounder in females than in males. Adults are likely polymorphic, with a large variety of coloration across their range. Southern variations tend to have reddish-brown forewings, while other variations can be orange-brown or purple-brown. Likewise, populations in the southern region show a variation between diapausing and non-diapausing broods. Males that developed from diapausing pupae are tawny brown, while non-diapausing males are yellowish with some red. Early instars of larvae are brown, yellow, or dull orange, and are 3 to 4 mm in length when newly hatched. Later instars are bright green, with 2 distinctive lateral stripes, a red one on top and a white stripe just below. 4th and 5th instars grow to 3 to 5 cm in length. All instars have bifurcated urticating spines. Eggs are oblong with a flattened top. They are white when first laid, with a few yellow spots on the top and sides. After a few days, the top spot changes to black, and the side spots become tinted with orange as the larvae develops.
- Sexual Dimorphism
- sexes colored or patterned differently
- male more colorful
- Range wingspan
- 5 to 9 cm
- 1.97 to 3.54 in
Adults emerge from their cocoon during late morning or early afternoon in the warm, summer months. They remain in place until evening, while their wings fill and expand. After finding mates, females lay eggs on host plants. After about 10 days, the eggs hatch. All eggs hatch within 1 to 3 days of each other; the larvae do not leave until all have emerged. Larvae (commonly known as caterpillars) go through five instars, which takes about 4 weeks. The larvae eat continuously, before becoming pupae and spinning cocoons. The cocoon takes about 7 to 10 days to fully harden and form, and even then, they are very thin and easy to damage. Depending on the temperature and amount of daylight, pupae either emerge as adult moths within a few weeks, or they enter diapause for the winter, emerging in the spring when temperatures warm up. Populations in northern regions are univoltine, with one generation per season, while populations farther south can have several generations per year, and some broods that do not diapause over winter. Diapausing pupae will not develop unless they experience the cold period, while non-diapausing pupae are very susceptible to cold temperatures. (Hossler, et al., 2008; Manley, 1993; Tuskes, et al., 1996)
After eclosion from their cocoons, adults have 1 or 2 weeks to find a mate and deposit eggs. After eclosion, males exhibit pre-flight posturing, by flexing and fluttering their wings, before taking flight. Females remain inactive the first night, and on the second night, they also show pre-flight posturing, though they do not take flight. Moths of family Saturniidae have specific "calling" times, during which females release pheromones to attract mates. To release pheromones, females extend and retract their last abdominal segment every few seconds over a short period of time. Females rarely mate on the night of their emergence, but they will call for mates as soon as the second night after eclosion. For , calling occurs during the evening, from 9:45 to 10:30 pm. Males detect female pheromones with their antennae, once a male locates a female, copulation lasts for about 90 minutes. If temperatures drop below 8 degrees Celsius, pairs may remain together until dusk the next day before separating. If temperatures remain warm, males fly away shortly after copulation. Females reportedly do not take flight until after they have mated. (Hossler, et al., 2008; Manley, 1978; Manley, 1993; Tuskes, et al., 1996)
Three to five days after mating, females lay their eggs in clusters of 20 to 35 on leaves or stems of suitable host plants, often on the undersides of foliage. Oviposition occurs during the evening. Females can lay several hundred eggs in their short, 1 to 2 week lifespan. In the north, (Hossler, et al., 2008; Russi, et al., 1973; Tuskes, et al., 1996)has only one generation per year, with adults emerging and mating from late May to mid-July. Father south in Florida and Texas, it has two to four generations every year, producing several broods of non-diapausing adults before producing pupae that diapause over winter. Populations in the Florida Keys breed year round due to the warm temperatures.
- Key Reproductive Features
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- Breeding interval
- Io moths only breed once.
- Breeding season
- Io moths breed from late May to July, though southern populations have multiple generations that breed earlier and later in the season.
- Average eggs per season
Since adults only live 1 to 2 weeks, they provide no care for their offspring, although they do deposit the eggs on a suitable host plant and provide provisioning in the eggs. (Hossler, et al., 2008)
- Parental Investment
Adults live only 1 to 2 weeks after emerging from pupation. (Hossler, et al., 2008)
- Typical lifespan
- 7 to 14 days
- Typical lifespan
There is currently no information available regarding the home range size of Io moths.
Communication and Perception
- Other Communication Modes
Larvae of Salix species, redbuds (Cercis), hackberries (Celtis), and species of Hibiscus, Pyrus, Ribes, Rubus, Sassafras, Prunus, and Wisteria. These caterpillars also eat their empty egg shells after hatching, as well as their molted skin (exuviae). Adults have vestigial mouth parts, but do not feed during their short lifespan. (Hossler, et al., 2008; Manley, 1993; Russi, et al., 1973; Tuskes, et al., 1996)eat large amounts of leaves, with the potential to defoliate plants and strip branches clean. They feed on a large variety of plants. Some studies have recorded at least 60 plants in their diet, including most major groups of angiosperms. Some preferences include willow trees and other
- Plant Foods
Adults of Saturniidae species have venom or histamines in their spines, though the contents of larval spines have not been studied. The bright larval colors likely serve as aposematic coloration, warning predators to avoid them. Other insects prey on the larvae, including wheel bugs (Arilus cristatus) and hornets (Vespa). (Manley, 1978; Manley, 1990; Russi, et al., 1973; Simberloff and Wilson, 1969; Tuskes, et al., 1996)use the large eyespots on its hindwings as a defense mechanism. At rest, its forewings cover its eyespots. When disturbed, it "flexes" its wings and displays the eyespots, creating a 'startle effect'. This is often accompanied by behaviors that confuse or startle predators. Larvae tend to drop off the leaves or branches they are feeding on when disturbed. They also gather in large groups, which may make them appear more intimidating to predators. Additionally, all larval instar stages have urticating spines that are irritating to those that come into contact with them. Other related
- Anti-predator Adaptations
Larvae of Cercis), hackberries (Celtis), and species of Hibiscus, Prunus, Pyrus, Ribes, Rubus, Salix, Sassafras, and Wisteria. These caterpillars are also prey to several other species of insects, and can host several parasites. These parasites, which typically lay eggs in their larvae, include wasps of genus Cotesia, the wasp species Apanteles hemileucae, and several species of tachinid flies, Compsilura concinnata, Chetogena claripennis, and Carcelia formosa. (Onuf, et al., 1977; Schaffner and Griswold, 1934; Simberloff and Wilson, 1969; Tuskes, et al., 1996)are important herbivores, and can completely strip branches of trees and plants. Some of the preferred host plants include redbuds (
Economic Importance for Humans: Positive
There are no known positive effects ofon humans.
Economic Importance for Humans: Negative
Caterpillars of Saturniidae moths may contain venom or histamines in their spines that can cause severe reactions, though the contents of spines have not been analyzed. Additionally, in the early 1900s, these caterpillars were considered a pest of cotton in the southern United States, and can potentially cause crop damage. (Manley, 1993; Tuskes, et al., 1996)have urticating spines that can cause irritation and pain. After the pain subsides, swelling, erythema, and urticaria can occur. This is a relatively common occurrence for humans, who may accidentally touch the caterpillars, and can especially be a problem for children. The spines could also potentially injure the mouths of grazing livestock, as these caterpillars can be found in pastures. Larvae of other
- Negative Impacts
- bites or stings
- crop pest
Angela Miner (author), Animal Diversity Web Staff, Leila Siciliano Martina (editor), Animal Diversity Web Staff.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the southern part of the New World. In other words, Central and South America.
living in landscapes dominated by human agriculture.
having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.
- bilateral symmetry
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
uses smells or other chemicals to communicate
a period of time when growth or development is suspended in insects and other invertebrates, it can usually only be ended the appropriate environmental stimulus.
- active during the day, 2. lasting for one day.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
union of egg and spermatozoan
an animal that mainly eats leaves.
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
An animal that eats mainly plants or parts of plants.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
- internal fertilization
fertilization takes place within the female's body
A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.
having the capacity to move from one place to another.
- native range
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
chemicals released into air or water that are detected by and responded to by other animals of the same species
"many forms." A species is polymorphic if its individuals can be divided into two or more easily recognized groups, based on structure, color, or other similar characteristics. The term only applies when the distinct groups can be found in the same area; graded or clinal variation throughout the range of a species (e.g. a north-to-south decrease in size) is not polymorphism. Polymorphic characteristics may be inherited because the differences have a genetic basis, or they may be the result of environmental influences. We do not consider sexual differences (i.e. sexual dimorphism), seasonal changes (e.g. change in fur color), or age-related changes to be polymorphic. Polymorphism in a local population can be an adaptation to prevent density-dependent predation, where predators preferentially prey on the most common morph.
- seasonal breeding
breeding is confined to a particular season
offspring are all produced in a single group (litter, clutch, etc.), after which the parent usually dies. Semelparous organisms often only live through a single season/year (or other periodic change in conditions) but may live for many seasons. In both cases reproduction occurs as a single investment of energy in offspring, with no future chance for investment in reproduction.
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
living in residential areas on the outskirts of large cities or towns.
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
- tropical savanna and grassland
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
- temperate grassland
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
uses sight to communicate
Borror, D., R. White. 1970. A Field Guide to the Insects. New York: Houghton Mifflin Company.
Hossler, E., D. Elston, D. Wagner. 2008. What's eating you? Io moth (Cutis, 82/1: 21-24.).
Manley, T. 1978. Genetics of conspicuous markings of Io moth. Journal of Heredity, 69/1: 11-18.
Manley, T. 1993. Diapause, voltinism, and foodplants of Saturniidae in the southeastern United States. Journal of the Lepidopterists' Society, 47/4: 303-321.(
Onuf, C., J. Teal, I. Valiela. 1977. Interactions of Nutrients, Plant Growth and Herbivory in a Mangrove Ecosystem. Ecology, 58/3: 514-526.
Peterson, A. 1962. Some Eggs of Insects That Change Color during Incubation. The Florida Entomologist, 45/2: 81-87.
Schaffner, J., C. Griswold. 1934. Macrolepidoptera and Their Parasites Reared from Field Collections in the Northeastern Part of the United States. Washington D.C.: U.S. Department of Agriculture.
Simberloff, D., E. Wilson. 1969. Experimental Zoogeography of Islands: The Colonization of Empty Islands. Ecology, 50/2: 278-296.
Tuskes, P., M. Collins, J. Tuttle. 1996. The Wild Silk Moths of North America: A Natural History of the Saturniidae of the United States and Canada. Ithaca, New York: Cornell University Press.
Wagner, D. 2012. Moth decline in the Northeastern United States. News of the Lepidopterists' Society, 54/2: 52-56.
Worth, B. 1979. Captures of large moths by an UV light trap. Journal of the Lepidopterists' Society, 33/4: 261-264.