Harmless. It has no sting, and as an adult it has no working mouthparts at all — it cannot bite because it cannot eat. It is safe to let sit on your hand.
SizeWingspan 100–150 mm
MarkingsVery large and tan to reddish brown, with a wingspan wider than your palm · A huge round eyespot in the middle of each hindwing, ringed in yellow and blue
WhereDeciduous woodland, orchards and some wetlands. Adults of both sexes come readily to lights, which is where nearly everybody meets one.
SeasonApril–May and July–August in the south, in two broods; a single May–July flight in the north
How to tell it apart
Very large and tan to reddish brown, with a wingspan wider than your palm
A huge round eyespot in the middle of each hindwing, ringed in yellow and blue
A much smaller clear eyespot near the middle of each forewing
Broad feathery antennae mean a male; slimmer antennae and a fatter body mean a female
Usually found sitting still by a porch light or a lit doorway in the morning
Where you’ll find it
The most widespread giant silkmoth in North America — southern Canada southward, in every Canadian province except Newfoundland and in virtually every state in the continental US. If you have found a large eyespotted moth almost anywhere in the country, this is the likeliest one.
Deciduous woodland, orchards and some wetlands. Adults of both sexes come readily to lights, which is where nearly everybody meets one.
April–May and July–August in the south, in two broods; a single May–July flight in the north.
How it behaves
The adult does one thing: find a mate. It has about a week to do it, cannot feed, and dies afterwards. Males track females by scent using those feathered antennae, sometimes across a considerable distance. The eyespots are a defence — a bird that gets a sudden flash of what look like large eyes tends to hesitate, and a hesitation is all the moth needs.
You’ve found one indoors
Leave it be. It is not damaged and it does not need feeding — a jar with sugar water will not help an animal with no mouth. If it is somewhere it will get stepped on, slide a piece of paper under it and move it to a tree trunk or a shaded fence in the shade, where it will sit out the day and fly at dusk.
Common questions
What do I feed it?
Nothing. Adult polyphemus moths have no functioning mouthparts. They live for roughly a week on what they stored as a caterpillar and then die, which is normal and not something you can prevent.
Do polyphemus moths bite or sting?
No. No sting, and no mouth to bite with.
Is it rare? It looks like it should be.
Not rare, just rarely seen. It is the most widespread giant silkmoth on the continent. The adults fly at night and live about a week, so the odds of being outside at the right moment are small.
How do I tell it from a cecropia moth?
Colour and markings. Polyphemus is tan to reddish brown with big round eyespots on the hindwings. Cecropia is charcoal and grey with red shading and crescent-shaped white-centred spots, not round eyespots.
I found a huge green caterpillar — is it this?
Possibly. The larva is very large, bright green, with oblique yellow lines along the abdomen that cross at the breathing pores. A luna moth caterpillar is similar but its yellow lines sit near the back edge of each segment instead.
Christine Stone · CC0