Caterpillars are eating machines, and all that food has to go somewhere! As they consume leaf after leaf, they grow rapidly, but their rigid exoskeleton can’t expand. So, how do they get bigger? They shed their skin! This process, called molting or ecdysis, is how caterpillars grow.
The Molting Process: Shedding Skin to Grow Bigger
The exoskeleton, that tough outer layer that provides support and protection, becomes too small as the caterpillar grows. Molting is a complex process controlled primarily by hormones. Before shedding, the caterpillar prepares by growing a brand new, larger cuticle (the basis of the new exoskeleton) underneath the old one. Think of it like building a new house inside your current one before moving out!
To loosen the old exoskeleton, the caterpillar secretes enzymes between the layers. These enzymes dissolve the connections between the old cuticle and the muscles, allowing the new, larger cuticle to form without being exposed and vulnerable. Once the old exoskeleton is sufficiently loosened, the caterpillar wriggles and sheds the old skin, revealing its fresh, new, bigger “suit.”
Instars: Stages of Growth
Each stage between molts is called an instar. It’s like a level in a video game – the caterpillar has to “level up” by molting to reach the next stage. Most butterfly caterpillars go through five instars before they pupate (transform into a chrysalis). During each instar, the caterpillar eats voraciously, growing larger and preparing for the next molt. The pupation stage itself is another type of molt, where the caterpillar sheds its skin one final time to reveal the chrysalis.
More information about Molting From Fourth to Fifth Instar by Monarch Watch
Why Molting Matters
Molting is essential for caterpillar growth. Without this process, they would be trapped in their old, too-small exoskeletons. Each molt allows the caterpillar to increase in size, store energy, and ultimately prepare for the incredible transformation into a butterfly.
