Jul 17 2020

Metamorphosis

Metamorphosis is when a creature changes form from one thing to another. In the butterfly life cycle, it’s when the caterpillar becomes a butterfly.

The large caterpillar I found in my garden is ready for its metamorphosis.

When they are large caterpillars, they eat a seemingly endless amount of food for a few days to get as much fuel for this metamorphosis as possible. During the change they go through, they have no way to get fuel. In fact, even butterflies do not “eat” ever again. They will drink nectar from plants which provides quick moisture and energy to give the butterfly strength to fly, but no nutrients to keep the butterfly alive for a long period of time.

My caterpillar has been happily munching on a piece of a milkweed plant that broke when I was collecting eggs, and then on the flower buds that formed on another plant. (Gardening tip: if you want a bigger, leafier plant, you need to cut off flower heads so that the plant will stop spending its energy on flowering and deliver that energy to forming more green parts instead.) Last night, it climbed to the roof of the aquarium I store my caterpillars in and searched out a spot on the mesh lid to begin its transition.

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Over the course of several hours, the caterpillar uses its mouth to create a silky web. In nature it might be on a stem or a leaf… but inside the aquarium the mesh lid is almost always where my caterpillars go to do this.

You can see the web in this picture. Us butterfly enthusiasts call it a “button.” Once the caterpillar is done making its button, they attach their back end to it with a sort of limb called a cremaster. Then they slowly let go of the mesh from all sets of their feet and hang, like you see in this picture. We say that the caterpillar is in “J” formation because they look like a J.

In all of the resources I’ve read, I’ve never read about why caterpillars do this… but they hang like this for about 24 hours before they shed and harden into a chrysalis for their metamorphosis. My best guess is that they are resting because that final shed of their exoskeleton is really difficult!

Look for an update later on today or tomorrow once this caterpillar has shed and made its chrysalis!

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