The hickory horned devils are solitary nighttime feeders in early stages, when they curl up in a "j" shaped pattern during the day and resemble two-toned bird droppings.
As the caterpillars age, they feed during the day. They molt 5 times. Each instar is different, but on their sixth and final instar they become a bright green color, with huge black-tipped red horns, earning them their common name "hickory horned devils". They feed heavily on their host plant and can grow up to 15cm long. Their scary appearance is purely a ruse; the spines, though prickly, do not sting, and the larva is harmless and actually one of the more easily handled of the saturniidae.
Just before pupation, the larva expels its gut and changes color from Frankenstein-green to a more fetching turquoise, the skin of the fully fed creature stretched shiny and tight. They then crawl down the host plant, where they burrow into the dirt and pupate in a well formed chamber at a depth of five to six inches. The pupae are dark brown/black in color, and have a relatively short cremaster. Some pupae overwinter for 2 seasons, perhaps as an adaption to variable and adverse conditions such as fires and flooding, or to maintain genetic diversity across generations.