The Polyphemus cats have moved into their next instar!
Caterpillars pass through five stages of growth, called instars. They enter each new stage by shedding their old skins.
Caterpillars often stop eating a day or so before shedding. They use silk to attach their rear ends to leaves or twigs. They puff themselves up to loosen their old skins. Then they crawl away, leaving the skin behind.
As well as shedding their skins they shed the faceplates that cover their faces. These usually show up at the bottom of the cage, amid balls of poop and scraps of leaves.
Polyphemus caterpillars look pretty much the same from instar to instar – they just get bigger. But some caterpillars change dramatically.
The first instars of Spicebush Swallowtails resemble dollops of bird poop.
Later instars look like cartoon characters.
Other insects shed skins and pass through instars as well. Ladybugs go through several instars that don’t look anything like their final form.
The Polyphemus cats have several weeks to grow and several skins to shed before they’re ready to spin cocoons. Happy munching!