Lepidoptera - Metamorphosis, Wings, Antennae: Lepidopterans show great diversity in size, structure, and other characteristics. Adults have three distinct body segments: head, thorax, and abdomen. The life cycle includes the egg, larva (caterpillar), and pupa (chrysalis) stages. The Lepidoptera belong to an insect group called the panorpoid complex. The earliest fossils date from the beginning of the Paleogene Period.