A thing I didn’t know until I started doing more and more research about silk: butterfly caterpillars make silk too.
Many of them don’t make much silk – it’s often just a little tuft, a few yards total – but it’s critically important to their life cycle. Most of the time, silk is used to make a small pad which attaches to a surface – anything from a twig to a leaf to a patio chair – where the caterpillar is going to pupate. Many, like some swallowtails, also make a “lasso” which helps keep the pupa in position against its substrate.
This is the hatched-out chrysalis of a Gulf fritillary, Agraulis vanillae, from my backyard passionflower patch. The silk pad attached it to the garden chair.