Larval describes the stage in an insect's or animal's life when it looks completely different from its adult form. A caterpillar is the larval stage of a butterfly or moth. A tadpole is the larval stage of a frog. During this phase, the creature is called a larva (plural: larvae).

Larval animals often have a completely different lifestyle from their adult versions. Caterpillars crawl on leaves and spend all day eating, while adult butterflies fly from flower to flower drinking nectar. Tadpoles swim with tails and breathe underwater with gills, while adult frogs hop on land and breathe air with lungs.

The larval stage is usually focused on one main job: eating and growing. A caterpillar might eat for weeks, growing larger and larger, before transforming into a butterfly. This process of dramatic change from larva to adult is called metamorphosis.

Scientists sometimes use larval more broadly to describe something that's in an early, undeveloped stage, like calling a rough first draft of an invention a larval design that will eventually develop into something much more sophisticated.