The juvenile stage of exopterygote insects, especially terrestrial species, such as grasshoppers, cockroaches, and earwigs; the juveniles of aquatic species (e.g. dragonflies, mayflies, stoneflies) are sometimes called naiads or larvae. The nymph resembles the adult except that the wings and reproductive organs are undeveloped. There is no pupal stage, the nymph developing directly into the adult. Compare larva.