Antheraea polyphemus
A large tan-coloured giant silk moth with striking purple eyespots on each hindwing, named after the cyclops Polyphemus. Widespread across North America from subarctic Canada to the southern United States. Caterpillars are polyphagous, feeding on a wide range of deciduous trees including oak, maple, birch, and sassafras.
Seasonal Activity
Diet
Foliage of oak, maple, birch, willow, elm, sassafras, and other deciduous trees (larva); adults do not feed
Lifecycle
Two broods per year throughout most of its range. Females lay eggs singly or in small groups on the underside of host leaves. Caterpillars pass through five instars, growing to 7.5-10 cm in length. Final-instar larvae are bright green with silver spots on the sides. The caterpillar spins a brown silk cocoon wrapped in a host plant leaf, which falls to the ground in autumn. Pupae overwinter in the leaf litter. Adults emerge in spring and late summer. Females emit pheromones at night; males fly up to several kilometres to locate mates. Adults are nocturnal, have vestigial mouthparts, and live less than one week.
Ecology
Host Plants
Native Habitats
Details
Description
The Polyphemus Moth (Antheraea polyphemus) is a large tan-coloured Saturniidae moth with a wingspan of 10-15 cm. Its most distinctive feature is the large, purplish eyespot on each hindwing, bordered in yellow and black — the moth's namesake, after the cyclops Polyphemus of Greek mythology. The wings are various shades of brown, from reddish-cinnamon to dark chocolate, with a black-and-white stripe along the wing margins. Males have large, feathery (plumose) antennae for detecting female pheromones; females have slender antennae and slightly larger abdomens.
The species is ranked Secure (G5) by NatureServe and Least Concern by the IUCN. It ranges across all of continental North America except Arizona and Nevada, with populations extending into subarctic Canada. It is one of the most widespread giant silk moths on the continent.
Lifecycle
Two broods typically hatch each year: adults emerge in early spring and again in late summer. Males emerge several days before females from the same brood. After mating — which occurs on the same day adults eclose — females lay eggs singly or in groups of 2-5 on the underside of host leaves.
Caterpillars pass through five instars. Early instars are yellow; by the fifth and final instar, larvae are bright green with silver spots along the sides and can reach 7.5-10 cm in length. The caterpillar then spins a brown silk cocoon, typically wrapped inside a host plant leaf for camouflage, which drops to the ground in autumn. Pupae overwinter in the leaf litter.
Adult emergence is triggered by warming temperatures. Moths eclose in the afternoon and must pump hemolymph into their wings to expand them. Females release pheromones in the late evening; males, detecting these with specialized sensilla on their antennae, can fly several kilometres to locate a mate. Adults have vestigial mouthparts, do not feed, and live less than one week.
Ecology
Caterpillars are highly polyphagous, feeding on a wide range of deciduous trees. Preferred hosts include American elm (Ulmus americana), birch (Betula), willow (Salix), oak (Quercus), maple (Acer), hickory (Carya), beech (Fagus), walnut (Juglans), and sassafras (Sassafras albidum), among many others.
The large hindwing eyespots serve as a startle display — when flashed, they resemble the eyes of a Great Horned Owl, deterring avian predators. Caterpillars produce clicking sounds with their mandibles when prodded and will regurgitate a deterrent fluid. Parasitoid wasps and the introduced tachinid fly Compsilura concinnata are significant threats. Squirrels prey on overwintering pupae. Light pollution disrupts adult mating behaviour.
Host Plants
Larvae are polyphagous on a wide range of deciduous trees. Key hosts in Ontario include:
- Oak (Quercus species)
- Maple (Acer species)
- Birch (Betula species)
- Willow (Salix species)
- Sassafras (Sassafras albidum)
- Wild Cherry (Prunus species)
Habitat
Polyphemus moths inhabit deciduous hardwood forests, forest edges, orchards, urban areas, and wetlands. In Ontario, they occur throughout the Carolinian Forest and Great Lakes-St. Lawrence forest regions. The species is highly adaptable and commonly encountered in suburban and even urban settings where mature host trees are present.