I've been documenting the development of Spicebush Swallowtail caterpillars on my recently planted spicebush. It only took the butterflies a few short days to find it and begin laying eggs on it.
Back inside, I pulled my John and Gloria Tveten field guide, Butterflies of Houston and Southeast Texas, from the shelf to read about the Spicebush Swallowtail. The Tvetens had written, "The larvae feed primarily at night, hiding during the day within a rolled leaf stitched with silk." So my caterpillars were performing exactly as Spicebush Swallowtails are known to perform. I had just never seen it because I've never had Spicebush caterpillars before.
Caterpillars are easy prey for hungry wasps and other predators and so they have to develop defensive measures to protect themselves. The rolled leaf is one of the most effective and it is used by several types of caterpillars, most notoriously the "leaf-rollers" that make a mess of our canna leaves during summer. Pretending to be a bird dropping is another defense. The clever little Spicebush caterpillars use both of these strategies and no doubt increase their survival rate accordingly.