Dragonfly larvae, known as nymphs, live in water and grow up by preying on small animals.

Dragonfly larvae, commonly known as nymphs, are the juvenile stage of dragonflies before they emerge as adults, and they spend most of their lives in water. They mostly inhabit freshwater environments such as ponds, paddy fields, ditches and streams, breathing underwater through rectal gills inside their bodies; when threatened, they can also squirt water rapidly out of their bodies and dart forward using the recoil.

The nymph is an ambush predator in the water, usually lying in wait among aquatic plants or in the mud and sand at the bottom, and when prey comes near it suddenly extends its telescopic lower lip, covering the victim like a mask. Its food consists mainly of small animals such as mosquito larvae, aquatic insects, small fish and tadpoles, which helps to some extent in suppressing mosquito breeding. As their bodies grow, they go through several molts; the length of the larval stage varies greatly depending on species and water temperature, ranging from as short as a few months to as long as several years.

Emergence is the most critical moment in a nymph's life. The mature larva climbs out of the water at night or in the early morning, clambers up a grass stem or stone at the water's edge, and the adult emerges after its back splits open; the wings gradually unfold and harden, and only then does it become the dragonfly we know. Newly emerged adults are paler in color and weak in activity, and usually need some time before they can fly normally.

When observing in the wild, nymphs are often confused with damselfly larvae. In fact, damselfly larvae have slender bodies and three leaf-shaped tail gills at the rear, while dragonfly larvae are more robust and have no tail gills. Because nymphs generally appear only in relatively clean water, they are often used as a reference indicator for monitoring the aquatic environment. For people engaged in paddy farming or nature observation, seeing nymphs active in the fields often means the ecology of that water body is being maintained well.