I used to think I knew how some caterpillars become butterflies. I assumed they weave cocoons, then sit inside growing six long legs, four wings, and so on. I figured if I were to cut open a cocoon, I’d find a butterfly-ish caterpillar, or a caterpillar-ish butterfly, depending on how far things had progressed. I was wrong. In fact, the first thing caterpillars do in their cocoons is shed their skin, leaving a soft, rubbery chrysalis. If you were to look inside the cocoon early on, you’d find nothing but a puddle of glop. But in that glop are [...]