Earwigs are mostly nocturnal and often hide in small, moist crevices during the day, and are active at night, feeding on a wide variety of insects and plants.

Some earwig specimen fossils are placed with extinct suborders Archidermaptera or Eodermaptera, the former dating to the Late Triassic and the latter to the Middle Jurassic.

[2] Entomologists suggest that the origin of the name is a reference to the appearance of the hindwings, which are unique and distinctive among insects, and resemble a human ear when unfolded.

[3][4] The name is more popularly thought to be related to the old wives' tale that earwigs burrowed into the brains of humans through the ear and laid their eggs there.

[11] Most earwigs are flattened (which allows them to fit inside tight crevices, such as under bark) with an elongated body generally 7–50 millimetres (1⁄4–2 in) long.

Strong neuron connections connect the neurohemal corpora cardiaca to the brain and frontal ganglion, where the closely related median corpus allatum produces juvenile hormone III in close proximity to the neurohemal dorsal arota.

Long, slender (excretory) malpighian tubules can be found between the junction of the mid- and hind gut.

[23] The reproductive system of females consist of paired ovaries, lateral oviducts, spermatheca, and a genital chamber.

Some earwigs, those parasitic in the suborders Arixeniina and Hemimerina, are viviparous (give birth to live young); they would be fed by a sort of placenta.

After laying them, she gathers them together, and studies have found mothers to pick up small egg-shaped wax balls or stones by accident.

[23] For protection from predators, the species Doru taeniatum of earwigs can squirt foul-smelling yellow liquid in the form of jets from scent glands on the dorsal side of the third and fourth abdominal segment.

In August 1755 they appeared in vast numbers near Stroud, Gloucestershire, UK, especially in the cracks and crevices of "old wooden buildings...so that they dropped out oftentimes in such multitudes as to literally cover the floor".

[28] A similar "plague" occurred in 2006, in and around a woodland cabin near the Blue Ridge Mountains of the eastern United States; it persisted through winter and lasted at least two years.

To a large extent, this species is also a scavenger, feeding on decaying plant and animal matter if given the chance.

[10] Plants that they feed on typically include clover, dahlias, zinnias, butterfly bush, hollyhock, lettuce, cauliflower, strawberry, blackberry, sunflowers, celery, peaches, plums, grapes, potatoes, roses, seedling beans and beets, and tender grass shoots and roots; they have also been known to eat corn silk, damaging the crop.

On the other hand, species in the genus Xeniaria (still of the suborder Arixeniina) are believed to feed on the guano and possibly the guanophilous arthropods in the bat's roost, where it has been found.

Interaction with earwigs at this time results in a defensive free-fall to the ground followed by a scramble to a nearby cleft or crevice.

Picnic tables, compost and waste bins, patios, lawn furniture, window frames, or anything with minute spaces (even artichoke blossoms) can potentially harbour them.

One species of tachinid fly, Triarthria setipennis, has been demonstrated to be successful as a biological control of earwigs for almost a century.

[35][36] Another tachinid fly and parasite of earwigs, Ocytata pallipes, has shown promise as a biological control agent as well.

[37] The common predatory wasp, the yellow jacket (Vespula maculifrons), preys upon earwigs when abundant.

[44] Phasmatodea Embioptera Orthoptera Notoptera †Dermapteridae †Protodiplatyidae †Bellodermatidae †Semenoviolidae †Turanodermatidae Hemimerina Arixeniina Forficulina The fossil record of the Dermaptera starts in the Late Triassic to Early Jurassic period about 208 million years ago in England and Australia, and comprises about 70 specimens in the extinct suborder Archidermaptera.

Some of the traits believed by neontologists to belong to modern earwigs are not found in the earliest fossils, but adults had five-segmented tarsi (the final segment of the leg), well developed ovipositors, veined tegmina (forewings) and long segmented cerci; in fact the pincers would not have been curled or used as they are now.

[14] The theorized stem group of the Dermaptera are the Protelytroptera, which are similar to modern Blattodea (cockroaches) with shell-like forewings and the large, unequal anal fan, are known from the Permian of North America, Europe and Australia.

[47] Amongst the most frequently suggested order of insects to be the closest relatives of Dermaptera is Notoptera, theorized by Giles in 1963.

[48] A 2018 phylogenetic analysis found that their closest living relatives were angel insects of the order Zoraptera, with very high support.

[14] Some evidence of early evolutionary history is the structure of the antennal heart, a separate circulatory organ consisting of two ampullae, or vesicles,[51] that are attached to the frontal cuticle near the bases of the antennae.

The first epizoic species of earwig was discovered by a London taxidermist on the body of a Malaysian hairless bulldog bat in 1909, then described by Karl Jordan.

Some examples are the flowers, hops, red raspberries,[61] and corn crops in Germany, and in the south of France, earwigs have been observed feeding on peaches and apricots.

The earwigs attacked mature plants and made cup-shaped bite marks 3–11 mm (1⁄8–7⁄16 in) in diameter.