How does a caterpillar grow?

A caterpillar grows by molting, or shedding its skin, because its exoskeleton doesn't stretch.

Understanding Caterpillar Growth

Caterpillars, like the Monarch caterpillar, go through a fascinating process of growth. Unlike humans whose skin expands as they grow, a caterpillar's external skeleton (exoskeleton) is rigid. Therefore, it cannot expand continuously. Here's how they manage to grow larger:

The Molting Process

• What is Molting? Molting is the process where a caterpillar sheds its old, smaller exoskeleton and reveals a new, larger one underneath. Think of it like a snake shedding its skin.
• How Often? Monarch caterpillars, for example, reach their full size after approximately two weeks of constant feeding and will molt several times during this period.
• The Role of Ecdysone A specific hormone called ecdysone triggers the molting process. This hormone cues the caterpillar's body to form a new exoskeleton under the old one and then shed the old one.

Steps of Molting

1. Preparation: The caterpillar starts by forming a new, soft exoskeleton beneath the old one.
2. Separation: The old exoskeleton separates from the new exoskeleton.
3. Shedding: The caterpillar then wiggles and pushes its way out of the old exoskeleton.
4. Hardening: Once the old skin is shed, the new exoskeleton expands and hardens, and the caterpillar is now larger.

Summary

The process of molting allows caterpillars to grow significantly during their larval stage, preparing them for their transformation into a pupa and eventually, a butterfly or moth. This process is essential for their survival and development.