The chrysalis is a stage in the life cycle of a butterfly. It is the third stage in complete metamorphosis, following the egg and the larva (caterpillar), and preceding the final adult stage. This stationary form offers security while the insect undergoes internal restructuring, preparing to emerge as a winged adult. The shell is formed from the final larval skin, which hardens into a rigid, often camouflaged structure.
The Process of Pupation
The formation of the chrysalis begins after the caterpillar reaches full size and finds a suitable location. The larva spins a small silk pad, securing its rear end to a surface like a twig or a leaf, and hangs inverted before its final molt.
The outer caterpillar skin splits behind the head and is pushed upward toward the attachment point. The soft, new pupal shell is revealed underneath as the old skin bunches up. The pupa must then shed the last remnants of the larval skin.
During this shedding, the pupa secures itself to the silk pad using the cremaster, a specialized structure at its posterior end. The cremaster is a stem-like projection equipped with hundreds of microscopic hooks that anchor the chrysalis securely. Once anchored, the pupa sheds the old skin, allowing the new chrysalis to harden.
Distinguishing Chrysalis from Cocoon
Chrysalis and cocoon refer to two distinct structures used by different insects within the order Lepidoptera. A chrysalis is the pupal stage of a butterfly, characterized by its “naked” appearance. It is the hardened exoskeleton of the insect itself, formed directly from the caterpillar’s final molt.
A cocoon is a protective silk casing that a moth caterpillar spins around its pupa. The moth pupa is contained inside this external structure, which is made from spun silk and sometimes incorporates leaves or hair for camouflage. The chrysalis is the pupa’s hard outer shell, while the cocoon is the covering spun by the larva.
Chrysalises are typically smooth, hard, and sometimes angular, often featuring colors that blend with the environment. Cocoons, conversely, are composed of silken threads and tend to be soft, fuzzy, or fibrous in texture. Many moth cocoons are buried or hidden in leaf litter, while chrysalises are often found hanging freely.
The Biological Transformation Within
Once the chrysalis hardens, metamorphosis begins inside the protective shell. This is not a period of sleep, but a period of internal restructuring. The first phase of this change is histolysis, the breakdown of larval tissues.
Specialized enzymes dissolve the caterpillar’s muscles, gut, and other larval organs into a liquid mixture. This decomposition is necessary because the adult butterfly requires a different body plan. The nutrients released from this self-digestion are then recycled to build the adult body.
Adult structures are constructed from small, dormant clusters of cells called imaginal discs. Each imaginal disc contains the plan for a specific adult part, such as a wing, leg, or antenna. This process of building new tissue is called histogenesis, where these discs rapidly divide and differentiate. They use the energy provided by the dissolved larval tissues to construct the complex features of the butterfly.
The Final Stage of Eclosion
The emergence of the adult butterfly is called eclosion. The chrysalis shell becomes translucent toward the end of the pupal stage and splits open. The adult insect must then push its way out of the casing.
The newly emerged butterfly appears wet, with a swollen abdomen and small, crumpled wings. It immediately begins inflating its wings while hanging vertically, allowing gravity to assist the process. The insect pumps hemolymph from its body into the network of veins within the wings.
This fluid pressure expands the wings to their full size and shape, a process that can take anywhere from a few minutes to several hours. Once the wings are fully expanded, the hemolymph is withdrawn, and the wings must dry and harden before the butterfly can attempt its first flight. Any disturbance or failure during this period can result in permanently deformed wings, preventing flight.