Pupa Stage: When the caterpillar has grown enough, it finds a protected spot, molts for the last time, and forms an encasement in which they metamorphose. During this stage, most moth caterpillars spin a silken cocoon while most butterfly caterpillars form a chrysalis. The pupa undergoes tremendous change. The caterpillar releases digestive juices that break down most of its body into a “tissue cell soup” from which it develops four wings, new legs, new eyes, new mouthparts, and genitalia. When the insect emerges, its metamorphosis is complete.