All caterpillars produce silk from silk glands. The silk is used for a variety of purposes including communication, defense and as a structural material. Caterpillars may enclose themselves in leaves, often for protection against parasitoids, predators or inclement weather. Some caterpillars will feed inside leave rolls or ties. Other caterpillars will tie leaves to make a protected site for pupation.
The caterpillar below has parked on the surface of a plastic container in preparation for pupation. The caterpillar has used silk to wrap itself with a leaf (which is slightly pulled away for better viewing). How does the caterpillar manage to “pull” the leaf around itself? The silk is a sticky protein that the caterpillar forces out its silk gland. The caterpillar will attach the strand to one surface to be tied, then stretches the silk strand before attaching it to the second surface. After the silk is attached, it will contract to pull the surfaces together. Caterpillar silk can generate a force 30 times the force of gravity to hold surfaces together.