Insects grow by metamorphosis. In incomplete metamorphosis, an insect egg hatches, and a small nymph comes out. The nymph usually looks just like the adult insect but is much smaller. Nymphs do not become pupae before becoming adults. They just grow larger. They moult through various stages called instars.
Some insects have nymphs that are aquatic, which means they live in water. These nymphs look very different from the adults. Dragonflies have nymphs that live in water, such as in lakes and rivers. Nymphs that live in water are sometimes called naiads.