Royal Alberta Museum: Invertebrate Zoology - Bug Facts

[Caterpillars and Other Immature Insects]

Fact Sheets: Commonly Observed and Asked About Insects and Spiders Found in Alberta

Polyphemus Moth (Antheraea polyphemus)

Polyphemus Moth
Photo CD 0023 3291 1601, Image #06 - Credit: Terry Thormin

Polyphemus Moth caterpillar
From the collection of Terry Thormin

INTRODUCTION

The Polyphemus Moth is one of the largest moths in Alberta, reaching wingspans of 10 to 15 cm. The caterpillar can achieve lengths of 7 to 8 cm. Neither the moth, which is active only at night, nor the caterpillar, which is well camouflaged, is often seen. However, when seen they cause a lot of curiosity because of their size.

IDENTIFICATION

The size of both the moth and caterpillar eliminate almost all other species. The reddish-brown or yellowish-brown wings of the moth, with clear eyespots in both the front and hind wings, and the black area surrounding the hind wing spot, make it easy to distinguish this moth from similar species like the Columbian Silk Moth. The green colour, hairy knobs and pale yellow vertical streaks on each body segment, separate the caterpillar from similar species.

DISTRIBUTION

The Polyphemus Moth is found throughout Alberta in wooded areas.

TIME OF YEAR

Adults appear in June, with some individuals lasting into July. Caterpillars first appear by about mid-July and mature by early to mid-August. The cocoons are formed from leaves and silk, and are located in protected areas. They overwinter in this stage and the adults emerge the following June.

HABITAT AND HABITS

Caterpillars feed on a variety of plants, including rose, birch, maple, ash, oak and pine. For this reason they are found in wooded or shrubby areas. They often get into backyards if the appropriate plants are found. Because of their excellent camouflage, they are not often discovered unless their numbers reach proportions that they are doing noticeable damage. Adults do not have mouthparts and do not feed. Females emerge from the cocoon with the eggs already preformed and are immediately ready to mate. They produce pheromones that attract the males,who detect the pheromones with their feathery antennae which are designed for that purpose. Adults are nocturnal (active at night) and are attracted to lights. For this reason they sometimes turn up on people's doorsteps.

SIMILAR SPECIES

The Columbia Silkmoth is the only large moth found in Alberta that is closely related. It is found throughout Alberta but is decidedly rarer than the Polyphemus. It is a much darker maroon colour.

COMMENTS

Most people who see this moth for the first time are amazed that such a large moth is native to Alberta. People are often amazed at the size of the caterpillar, but are also concerned that it might be doing serious damage to their trees and shrubs. This species is seldom found in numbers sufficient to be considered a pest species, and its beauty far outweighs its destructiveness.

For information on how to over-winter pupae of this species, see How to over-winter butterfly and moth pupae

For more information on the Polyphemus Moth you can visit the University of Alberta’s entomology collection species page.

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Last update: December 10 2004