What do moth caterpillars spin around themselves?

Moth caterpillars spin a silk cocoon around themselves. Butterfly caterpillars generally do not - they shed their skin to reveal a hard chrysalis underneath, with no silk wrapping at all, which is the usual distinction between the two words.

What happens inside is not growth but demolition. Most of the caterpillar's tissues are broken down into a nutrient soup, and the adult is reassembled from small pockets of cells called imaginal discs that were present and dormant from the beginning - one for each wing, each leg, each antenna. The animal that emerges shares almost no cells with the one that went in.

Something crosses the gap, which is the part that unsettles people. Caterpillars trained to associate a particular smell with a mild electric shock produced moths that still avoided that smell. A memory survived the dismantling and rebuilding of the brain that formed it.