Some insects go through a metamorphosis process, where they change from an immature form into a mature adult form. After the immature insect feeds, it creates a cocoon in which it stays to go through the physical transformation to become a mature insect. Some of these insects attach their cocoons to trees.
Forest Tent Caterpillar
The forest tent caterpillar creates a loose silk cocoon with white or yellowish crystalline substance scattered throughout the cocoon. This crystalline substance could cause skin irritation if touched. The forest tent caterpillar locates the cocoon in the rolled leaves of a tree to hide it from predators. The mature insect emerges from the cocoon in three weeks.
A Cecropia moth cocoon measures more than 3 inches in length. Tough silken threads make up the cocoon, which is attached horizontally along twigs or branches. A cocoon located at a higher level tends to be long and compact, while a cocoon lower on the tree tends to be bulky and loose.
The Columbia moth spins a cocoon with brown silken threads. The cocoon usually measures 1 1/4 inch to 2 inches in length, has an oval shape and sometimes silver streaks on its sides. It attaches lengthwise to the twig or trunk of a tree, usually 2 to 6 feet away from the ground, near the tips of the branches.
A Promethea moth cocoon looks like a curled leaf that doesn't fall from the tree in autumn. As the insect spins the silken threads, it pulls a leaf around its body so that the cocoon sticks securely to the twig. The cocoon measures 1 to 2 inches in length and hangs vertically from a twig. Promethea moth cocoons tend to be located near one another.
The Polyphemus moth camouflages its cocoon with leaves. The insect fills the fibers of leaves with a fluid that turns white and chalky. Measuring about 2 inches long and having a more rounded shape than the promethea moth cocoon, the polyphemus cocoon is usually found on shrubs and small trees.