What's so wonderful about Polyphemus silk moths?

Another of our favorite species is the Polyphemus silk moth (Antheraea polyphemus). This beauty is not only one of the largest silk moths in North America, with wingspans that range from 4 to 6 inches, but it's also the most widespread. Unlike the Cecropia (Hyalophora cecropia) or Ceanothus (Hyalophora euryalus) species, which are geographically limited to east or west (respectively) of the Rocky Mountains, Polyphemus moths can be found throughout the contiguous United States. As a result, we're able to supply eggs and pupae to moth lovers throughout the U.S. 

In addition to being widely distributed, Polyphemus caterpillars are polyphagus, meaning they eat a wide variety of broad-leaved tree leaves. We've had the best luck with willow, chokecherry, and walnut in our desert environment; however, they're often called "oak silk moths" and will almost universally feed on oak. Your best bet is to offer several types of leaves that you have available from the extensive list of potential food plants to see which your caterpillars prefer. 

You can container raise Polyphemus caterpillars all the way through to pupation, but we usually move them outside onto sleeved trees once they get to the fourth instar. By that point, they're bright green with orange or red tubercles, making them easy to spot on a leaf. They're also consuming significant amounts of food and producing large amounts of frass (poop), which makes container raising less than ideal. Their voracious appetites are reminiscent of Eric Carle's Very Hungry Caterpillar.



When they've reached maximum chonkiness (technical term), which depends on genetic and environmental factors, the caterpillars spin a silk cocoon. Initially, you'll still be able to see the green caterpillar inside, but eventually, the caterpillar will pupate within the cocoon. After pupation, some will eclose within several weeks, while others will diapause (overwinter) depending (mostly) on the light cycle to which they were exposed. 

Our Pacific Northwest Polyphemus populations only have one brood per year, but some areas have two or even three. On the East Coast, the Ohio Valley seems to be the dividing line, with populations from Pennsylvania north only having one brood, while areas south of the valley have two. Some southern states have more than two broods per year, with Florida and Texas reporting adult moth sightings year-round. 

Male and female Polyphemus moths are fairly easy to tell apart. Males (above, left) have much larger, feathery antennae, which they use to sense female pheromones from great distances. The females (above, right) have thinner antenna, but larger abdomens for carrying hundreds of eggs.  Both sexes have only vestigial mouth parts and don't eat as adults. They live off their body fat reserves for about a week, long enough to mate and lay eggs.