The Very Hungry Caterpillar is a classic children’s book by Eric Carle. If you’ve ever wondered what the caterpillar would look like in real life, I imagine it would look like the larva of the Polyphemus moth, Antheraea polyphemus. The moth is named after the Cyclops named Polyphemus described in Homer’s The Odyssey.
Adult male polyphemus moth (Credit: University of Florida)
Polyphemus moths belong to the family Saturniidae, as they are considered silk moths, along with Luna moths, Cecropia moths, Io moths, and many others. These caterpillars are all fairly similar looking, but the polyphemus moth is distinguishable by the thin white stripes that it has running vertically down its sides.
This summer our lab found 2 polyphemus caterpillars while sampling at the Smithsonian Environmental Research Center (SERC) BiodiversiTREE experiment in Maryland, one at the beginning of summer and one at the end of summer. The polyphemus we found at the start of summer was likely in its first or second instar, and was found on a Black Oak (Quercus velutina) tree in a 12 species polyculture. The second one we found was in its last instar, and was found on a White Oak (Quercus alba) tree in a 4 species polyculture. This seems pretty typical, as these critters will eat a large range of trees: oak, maple, willow, elm, sycamore, and many more. And boy, do they eat a lot of leaves. We would have to put in 3-5 large oak leaves for these caterpillars, and those would last about a day and a half before being completely devoured. I didn’t compare these guys to The Very Hungry Caterpillar for nothing!
Early instar caterpillar that the sampling team found in June (Credit: Burghardt Lab)
Action shot of the same caterpillar a few months later. Nowhere close to his final size… (Credit: Burghardt Lab)
Final instar polyphemus caterpillar found in late August (Credit: Burghardt Lab)
Surprisingly, the final instar of the polyphemus was much harder to find than the first instar that we found. It most likely had to do with the fact that the caterpillars get so big - the one we found was probably as large as my pointer finger! Because the caterpillars are so large and have a green cryptic coloration, it’s pretty easy to see how predators may confuse the polyphemus for a leaf. Our lab almost made that same mistake!
Unfortunately, the large size of these creatures means that they’re an easy target for parasitoids and other natural enemies. Tachinid flies are common parasitoids, as well as several species of wasps. The caterpillar in the picture below was one we collected and sure enough, several weeks after it pupated, flies emerged instead of an adult moth. The polyphemus moth normally overwinters as a cocoon, so we are still waiting to see if our first larva will successfully emerge as an adult or not.
If you look closely, you can see some black parasitoid oviposition holes on the second segment behind this critter’s head! (Credit: Burghardt Lab)
A closeup of one of the parasitoid Tachinid flies that emerged from the caterpillar above (Credit: Burghardt Lab)
Written by Elizabeth Butz, undergraduate student