The cocoon is a strong symbol of change. Despite the mythology surrounding this metamorphosis, it is simply one stage of many in an insect's life. A caterpillar weaves a cocoon to rest in while it becomes a butterfly. Different types of butterflies weave different types of cocoons, but they all have certain things in common.
Pupae Life Cycle
A caterpillar is the larval stage of the butterfly. It spends most of its time eating and moulting. After its final moult, the caterpillar will pupate. It stops eating and forms the pupa, or chrysalis. The pupa is immobile and extremely vulnerable during this period. Gestation periods for most butterflies is a few weeks, but some caterpillars pupate in the fall and don't emerge until spring.
Caterpillar cocoons are made of silk and other fibrous materials produced by butterfly larvae. This sticky silk is produced in two glands on the inside of the insect. The caterpillar moves in a figure eight twist to envelope itself in the silk, which is soft and gooey at first but grows hard and dry when air touches it. The silk turns clear when the caterpillar is ready to emerge.
Cocoons and Plants
Caterpillars favour certain kinds of plants over others for food, laying eggs and pupating. Look for Monarch Butterfly cocoons and larvae on milkweed plants. Milkweed is the only food that Monarch butterfly larvae eat. Herbs, such as parsley and dill are favourites of a variety of Swallowtail butterflies. If you're not looking for any particular butterfly, then look for where caterpillars have eaten away at the leaves of a plant, and you will likely find butterfly larvae and cocoons.
Where to Find Cocoons
Cocoons can be found in a variety of places, but they are always up high enough to keep the butterfly's wings from touching the ground when it emerges. This ensures that the wings are able to dry properly. Cocoons can be found dangling from blades of grass or tucked into the notches of small branches. Some butterflies and many moth species also pupate in silk cocoons hidden in small hallows in the ground.