The name Apterygota is sometimes applied to a subclass of small, agile insects, distinguished from other insects by their lack of wings in the present and in their evolutionary history; notable examples are the silverfish, the firebrat, and the jumping bristletails. Their first known occurrence in the fossil record is during the Devonian period, 417–354 million years ago. The nymphs (younger stages) go through little or even no metamorphosis, hence they resemble the adult specimens. Their skin is thin, making them appear translucent.