Polyphemus moth vs Io moth
These two are easy to mix up. Here's how to tell a Polyphemus moth from an Io moth, and whether either one bites or stings.
Polyphemus moth
Antheraea polyphemus
Io moth
Automeris io
≠The key differences
Larger (wingspan often 110-150 mm) with a translucent 'window' spot on each hindwing rather than the circular eyespot of Io moth.
⚖︎Side by side
| Polyphemus moth | Io moth | |
|---|---|---|
| To humans | Non-toxic | Stinging caterpillar |
| Size | 11-15 cm wingspan | 50-80 mm wingspan |
| Colours | Reddish brown, Tan, Olive-brown, Sky blue (eyespot center) | Yellow, Reddish brown, Green (caterpillar), Blue (eyespots), Black (eyespot center) |
| Family | Saturniidae | Saturniidae |
| Habitat | Deciduous woodlands, suburban yards, parks and areas with host trees | Woodlands, forest edges, fields, gardens and riparian areas where host plants grow |
| Range | Widespread across much of the United States and southern Canada, extending into Mexico | Eastern and central North America — from southern Canada through the United States and into parts of Mexico |
| Active | Spring and early summer (one or two broods depending on latitude); adults are nocturnal | Spring to late summer depending on latitude; adults are nocturnal |
| Pest? | No | Yes |
🔍How to spot a Polyphemus moth
- Very large wingspan (11-15 cm) with broad, rounded wings
- Distinctive large circular eyespot on each hindwing with a clear center ringed with yellow, blue and black
- Overall reddish-brown to tan coloration with wavy crosslines across wings
- Males with notably feathered antennae; females with thinner antennae
🔍How to spot an Io moth
- Hindwings with a single large eyespot on each side: black-and-blue center with a white mark, on a yellow background
- Sexual dimorphism: males bright yellow, females reddish-brown on forewings
- Caterpillars bright green with branched stinging spines and a red-and-white stripe along each side
?Frequently asked questions
What is the difference between a Polyphemus moth and an Io moth?
Larger (wingspan often 110-150 mm) with a translucent 'window' spot on each hindwing rather than the circular eyespot of Io moth.
Is a Polyphemus moth or an Io moth more dangerous?
Polyphemus moth: Non-toxic. Io moth: Stinging caterpillar. Polyphemus moths do not bite or sting. Io moth caterpillars have urticating spines that inject irritant when they break the skin.
Identification from photos is never certain: don't handle insects you can't identify, and get medical advice for bites, stings or allergic reactions.