Earwigs are long-bodied insects with chewing mouthparts and many-jointed antennae in the order Dermaptera. Earwigs have small, vestigial forewings modified into a wing case, but their membranous hind-wings are large, folded, and functional, although they are not often used for flying. Earwigs hatch into nymphs which closely resemble the adults, only they are much smaller. Metamorphosis in earwigs is simple, with no radical changes in shape during development from the nymphal stages to the adult form.
The most readily distinguishing characteristic of earwigs is the pair of unjointed, forceps-like structures that terminate their abdomen. These unusual organs are modified from common insect structures known as cerci, and they differ between the sexes, those of females having less curvature. The pincers are brandished when earwigs are disturbed, and can give a significant pinch to the finger, so they are clearly useful in defense. The pincers may also have other uses, possibly in folding the rather complicated wings after a flight.
Earwigs are nocturnal animals, and they hide during the day in dark, damp places. Most species of the more than 1,200 species of earwigs are scavengers of a wide range of organic debris, including carrion. Some species are herbivorous, some are opportunistic predators of other insects, and a few, specialized species are parasites of mammals.
The most common native earwig in Europe is Forficula auricularia, a species that is now also widespread in North America, New Zealand, and elsewhere due to accidental introductions by humans. The European earwig is omnivorous, eating a wide range of dead organic matter, and also preying on other insects. The female of this species broods her eggs and young hatchlings. During summers when the European earwig is particularly abundant, it may be considered a pest because of its ubiquitous presence in flower gardens, under all manner of moist things, in basements and kitchens, and in laundry hanging on clotheslines. These earwigs may damage vegetables and flowers during their feeding, but they are not really an important pest. In fact, the European earwig may be beneficial in some respects, by cleaning up organic debris, and perhaps by preying on other, more important insect pests.
A total of 18 species of earwigs occur in North America. The seaside earwig (Anisolabis maritima) is a native species that occurs on both the Atlantic and Pacific coasts of North America. The red-legged earwig (Euborellia annulipes), striped earwig (Labidura bidens), and handsome earwig (Prolabia pulchella) occur in the southern United States. The toothed earwig (Spongovostox apicedentatus) occurs in dry habitats in the southwestern states. The little earwig (Labia minor) is another species that was introduced from Europe.
Some species of earwigs have relatively unusual, specialized lifestyles. Arixenia is a small earwig that is a viviparous breeder, giving birth to live young. This species is an ectoparasite of the Indian bat (Cheiromeles torquatus). Hemimerus is also a small, viviparous earwig, and a blind ectoparasite of the giant rat (Cricetomys gambianus) of west Africa.
Earwigs received their common name from the folk belief that these insects would sometimes crawl into the ears of people as they slept, seeking refuge in those dark, moist cavities. This may, indeed, sometimes occur, and it would certainly be disconcerting to have an earwig, or any other insect in one's ear. However, there is no evidence that earwigs in the ear are a common problem, except as very rare accidents.