The Polyphemus Moth has a wingspan of up to 6 1/2”, the largest wingspan of any moth in the PNW, although the largest one I’ve found ‘only’ measured a little over 5 1/2”. With its large size, tan ground color, and transparent eyespots it isn’t likely to be confused with any other moth in our region. It is said to be common in woodlands and damp forested areas, but in my year-and-a-half of mothing I’ve only seen 4. But each one is a golden memory etched upon my mind, a mixture of joy, awe, and gratitude. The first time I saw one my initial knowledge of it came when a huge shadow appeared on my mothing sheets. I took it to be a bat, an interesting happening in its own right. Then I saw the broad expanse of warm tan wing and breathed a soft ‘thank you’, to what I do not know.
The name Polyphemus comes from the Greek myths about the giant, cyclopean Polyphemus, son of Poseidon and Thoosa, in reference to the single eyespot on each wing, which probably serves to redirect bird strikes to these less biologically critical areas.
Though they are not reared for this purpose commercially, Polyphemus Moths are silk moths, and silk can be made from their cocoons, as shown here.
Polyphemus Moths utilize many different larval hosts, including (but not limited to) oak, willow, maple, alder, birch and shrubs and trees in the Rosaceae family. They can even be an agricultural pest, with occasional large outbreaks in filbert orchards. The caterpillars are leaf eaters and, despite the wide variety of leaves they will feed on, strongly prefer to stick with the species of leaves they start with. These caterpillars are known to be particularly voracious, eating up to 1,500 times their body mass daily! This would equate to eating roughly 2 cubic feet of oak leaves as a caterpillar. The adults, however, do not feed, having only vestigial mouthparts. My friend Mathew Campbell, who rears Lepidoptera for a living, says that the leps that don’t feed as adults typically eat far more as larvae.
Polyphemus Moths can be found region wide wherever there are larval hosts, which only excludes the most arid parts of the interior, and they have adapted to landscape plantings in urban areas. They fly from early May to late July.
Size- FW length 44-68mm
Habitat- Woodlands, mesic forests; wherever larval hosts can be found
Range- Region wide except for the most arid parts of the interior
Eats- Larvae eat leaves of, amongst others, oak, willow, maple, alder, birch, and shrubs and trees in the Rosaceae family. Adults do not feed
Flight Season- May to July