A nymph is the immature stage of an insect that gradually develops into the adult form through incomplete metamorphosis (does not include a pupal stage). The nymphs look like tiny versions of the adults that grow through a series of molts but lack wings or have undeveloped wings and cannot reproduce. Examples of insects with nymphal stages (have incomplete metamorphosis) include grasshoppers, stink bugs, leafhoppers, aphids and cockroaches.