Cocoons With Butterflies

During the time a caterpillar is in its cocoon, it radically transforms into a butterfly.

Beginning life as an egg and then hatching into a caterpillar, the caterpillar one day finds a spot to hang and spins a cocoon around itself that hardens into a pupa, or chrysalis. The pupa eventually breaks open and a beautiful butterfly emerges. Scientists call the transformation from a caterpillar to a butterfly metamorphosis. It is inside the cocoon where metamorphosis takes place. The purpose of a cocoon is to provide a protective covering for the caterpillar to protect it from prey.

Building a Cocoon

When a caterpillar is ready to enter its pupal stage in which metamorphosis takes place, it looks for a quiet, isolated spot such as secluded tree branches, the roof of a house, or an untouched patch of ground. A cocoon is prime prey for predators, so caterpillars want to find a safe spot. Caterpillars construct their cocoons using silk that they emit through two glands. Most caterpillars build their cocoons just large enough to encase their body.

Characteristics of a Cocoon

Cocoons can be a wide range of different colors, such as green and white, and they can be translucent or opaque. Some are soft and some are hard. The texture can be a loosely structured mesh or solid and tightly woven. It can consist of a single layer or more than one layer. The characteristics depend on the species of caterpillar (or butterfly). The butterfly that emerges from the cocoon will either cut its way out or release a liquid that softens the cocoon, enabling the insect to break through its walls.

Time Frames

A caterpillar can be inside its cocoon for as little as two weeks before it emerges as a butterfly. Other types of caterpillars need to stay inside their cocoon much longer. For example, the Queen Alexandra's birdwing, the largest butterfly in the world, stays in its cocoon for around 40 days. Caterpillars that live in colder climates where there is snow stay inside their cocoons all winter.

Emerging from the Cocoon

Butterflies tend to emerge from their cocoons in the morning. When they first break out, their wings look tiny and are wrinkled. Before flying, they hang upside down where their cocoon had been hanging and dry out in the sun. Soon their wings begin to fill out and become unwrinkled. The butterfly is able to fly as soon as it takes off from where it was hanging.

References

• Cocoon.org: Butterfly and Moth Information
• Novel Guide: Butterflies and Lepidoptera
• Dublin Butterfly House
• Earth's Endangered: Queen Alexandra's Birdwing Butterfly