A pupa is an insect in the quiet middle stage of its life, after it has been a larva (a caterpillar, a maggot) and before it comes out as an adult. Inside a special cover it changes shape. For many butterflies people also say chrysalis; chrysalis is the butterfly/moth case, while pupa is the wider scientific word for that stage in insects generally, including flies and beetles. The usual plural in school science is pupae; pupas is also heard. English took the word from New Latin, from Latin pūpa, 'little girl' or 'doll' — the resting insect looked, to the namers, like a tiny wrapped figure. Though actually, the insect is not sleeping in a simple way; a huge rebuilding is going on inside. Students sometimes call every caterpillar a pupa, but the crawling eating stage is the larva; the pupa is the still, covered stage that follows.