Earwig, (order Dermaptera), any of approximately 1,800 species of insects that are characterized by large membranous hindwings that lie hidden under short, leathery forewings. The name earwig is derived from the Anglo-Saxon word meaning “ear creature,” probably because of a widespread ancient superstition that earwigs crawl into the ears of sleeping people. The earwig varies from 5 to 50 mm (0.2 to 2 inches) in length and is flat, slender, and dark-coloured. It has a shiny outer covering and simple biting mouthparts, and it undergoes incomplete metamorphosis (i.e., egg, nymph, and adult stages). This nocturnal insect is usually herbivorous. Several species can fire a foul-smelling liquid, formed in abdominal glands and probably protective in function, for distances up to 10 cm (4 inches).

The earwig has a pair of horny forceps-like tail filaments, or pincers (cerci), at the posterior end of the abdomen, with those of the male being larger and of a different shape than those of the female. It has been suggested that the pincers may function in defense, in catching insects and holding them while eating, in helping to fold the hindwings under the forewings, or during courtship fights for possession of a female. When alarmed or aggressive the earwig carries the cerci over its body in a scorpion-like manner. In some species, earwig females exhibit maternal care, defending and feeding the newly hatched immatures.