Weekly “What is it?”: Polyphemus Moth
Periodically, one of these articles spurs a question from a reader, often requiring additional research on my part. A few weeks ago, one of our Master Naturalists saw my article on the luna moth and asked for confirmation on a different species of moth he’d found. After some digging to confirm the identity of the insect in question—a polyphemus moth, as it turned out—I ended up solving a little mystery of my own.
I frequently walk about 3 miles through my neighborhood, listening to podcasts and chatting with neighbors. I have several routes that I frequent, and with my hands free and my phone’s camera handy, I often stop and take photos of interesting plants or animals along the way. For months, my attention has been drawn to a large, solid cocoon hanging from a river birch a few blocks from my house. I had no idea which insect created it, but I’d never noticed one quite so large before. When researching the polyphemus moth, I found that this is exactly what created my mystery cocoon!
Thick but paperlike, with a nearly perfect circular exit hole, the cocoon is large (at least 3” long) and well-constructed. Looking closely, you can observe the caterpillar used silk to wrap up a leaf tightly, so the finished product has a woven appearance. Even with their thick layers, the large cocoons are vulnerable to woodpeckers, squirrels, and parasitic insects.
The larvae of the polyphemus moth feeds on the leaves of hardwood trees, with a preference for birch, maple, and oaks. While caterpillars feed on the trees, they rarely cause enough damage to permanently injure their host tree. Polyphemus moths are widespread throughout the United States, having been identified in every state but Nevada and Arizona.
As an adult, the polyphemus moth (named for a cyclops in Greek mythology), has the same eyespots on its hind wings as other Saturniid moths. These are a defense mechanism, tricking would-be predators into thinking they are seeing the eyes of a much larger animal. Most moths are rather unremarkable, but the polyphemus, like its cousin the luna, is larger and more butterfly-like, with colorful (multiple shades of brown, red, and pink) wings and patterns.