Introduction

Dermaptera, the earwigs, are among the most instantly recognisable insects thanks to the pair of unsegmented sclerotised forceps at the tip of their abdomen — a feature found in no other insect order. These elongate, nocturnal insects inhabit leaf litter, bark crevices, and soil across every continent and most oceanic islands, with approximately 2,000 described species in around 12 families. Despite their modest diversity, earwigs are ecologically versatile omnivores and display one of the best-documented examples of maternal care among non-social insects: females actively guard their eggs and early-instar nymphs in underground chambers.

Beyond their iconic forceps, earwigs possess a second engineering marvel — their hindwings. These fan-shaped membranous wings fold into a package roughly one-tenth of their unfolded area, tucked beneath extremely short tegmina. The folding geometry is so elegant that it has inspired origami-based designs for deployable structures in engineering. For a complete diagnostic guide to all insect orders, see Insecta Guide.

Systematic Position and Classification

Dermaptera belong to the superorder Polyneoptera. Their phylogenetic position within Polyneoptera has been debated, but recent molecular analyses place them near Plecoptera and Orthoptera. The order includes approximately 12 families, among which the major groups are Forficulidae, Labiduridae, Anisolabididae, Spongiphoridae, and Pygidicranidae. Two highly modified parasitic families stand out: Arixeniidae (ectoparasites of bats in Southeast Asia) and Hemimeridae (ectoparasites of giant African pouched rats), both wingless and with flattened bodies adapted to life on their mammalian hosts.

Fossil record

The oldest definitive dermapteran fossils date to approximately 210 million years ago (Late Triassic). Mesozoic fossils from the Jurassic and Cretaceous document a variety of forms, including some with segmented cerci that represent stem-group Dermaptera. The transition from segmented cerci to the characteristic unsegmented forceps is a key evolutionary event documented in the fossil sequence. Modern families appear by the Eocene.

Morphology

Head and mouthparts

The head is prognathous (forward-facing) with well-developed compound eyes. Ocelli are absent in all living species. Antennae are filiform and relatively short, typically with around 15 segments. Mouthparts are of the generalised chewing type with robust mandibles, 3-segmented maxillary palps, and 3-segmented labial palps — suitable for their omnivorous diet.

Thorax and legs

The pronotum is large and shield-shaped with a distinct lateral rim. The body is strongly elongate and somewhat dorso-ventrally flattened, well suited for squeezing into tight spaces. All three pairs of legs are unspecialised, bearing a 3-3-3 tarsal formula — a reduced count compared to many polyneopteran relatives. Legs are short relative to body length.

Wings and tegmina

The forewings are modified into very short, truncate tegmina that leave the majority of the abdomen exposed — an appearance that can superficially recall rove beetles (Staphylinidae). Tegmina have reduced venation. The hindwings are the true flight organs: large, semicircular, membranous, and elaborately fan-folded to fit beneath the tiny tegmina. Despite this sophisticated folding mechanism, most earwig species fly rarely or not at all. Many lineages have reduced or entirely lost the hindwings.

Abdomen

The abdomen has 10 visible segments and terminates in the order’s signature feature: a pair of unsegmented, sclerotised forceps (modified cerci). Forceps morphology is sexually dimorphic in many species — males often have curved, asymmetric forceps while female forceps are straighter. The forceps serve in defence, prey capture, wing folding, and courtship. The ovipositor is reduced and internal.

Biogeography

Dermaptera are cosmopolitan, occurring on all continents and most island groups. Diversity is highest in the tropical and subtropical belts, particularly in the Oriental and Afrotropical regions. Several species have been widely dispersed through human commerce — most notably Forficula auricularia, the European earwig, which is now established across temperate zones on every continent. The parasitic families Arixeniidae and Hemimeridae have highly restricted ranges dictated by the distributions of their mammalian hosts.

Ecology and Life History

Feeding biology

Earwigs are predominantly omnivores, taking a wide range of plant material, fungi, small arthropods, and decaying organic matter. They are opportunistic feeders that can shift diet based on availability — some species are minor predators of aphids and other soft-bodied insects, making them incidental biocontrol agents. Feeding is almost exclusively nocturnal; by day, earwigs retreat into bark crevices, soil gaps, and under stones.

Activity and behaviour

Dermaptera are strongly nocturnal and thigmotactic — they actively seek tight crevices and concealed spaces. When disturbed, they raise their forceps in a threat display, and some species can deliver a noticeable (though harmless) pinch. Flight is rare; even species with fully developed hindwings seldom take to the air. The earwig escape strategy is to wedge into tight spaces rather than to fly.

Life cycle

Development is hemimetabolous, with nymphs resembling adults and bearing forceps from the earliest instars. Earwigs are notable for their maternal brood care: the female excavates a chamber in soil or under bark, deposits her clutch, and guards the eggs through development — grooming them to prevent fungal infection and protecting them from predators. She continues to attend the first-instar nymphs until they are able to forage independently. This level of parental investment is unusual among non-social insects and has made earwigs important subjects in the study of insect sociality evolution.

Applied Significance

Earwigs have minor economic significance. Forficula auricularia is an occasional pest of soft fruits (strawberries, stone fruit), flower petals, and seedlings, earning it a nuisance reputation in horticulture. However, the same species acts as a beneficial predator of aphids in orchards and vegetable gardens, creating a complex cost–benefit relationship. No earwig species transmits diseases or has veterinary importance. Dermaptera have minor forensic relevance, as some species colonise decomposing remains.

Diagnostics and Identification

Earwigs are unmistakably diagnosed by the unsegmented sclerotised forceps at the abdominal apex — no other insect order possesses this structure. Additional diagnostic features include the extremely short, truncate tegmina that leave most of the abdomen exposed, large fan-folded membranous hindwings (when present), 3-3-3 tarsal formula, prognathous head without ocelli, and filiform antennae. The body is elongate and somewhat flattened.

Distinction from related taxa

The most common source of confusion is with rove beetles (Staphylinidae, Coleoptera), which also have short elytra exposing the abdomen. However, earwigs differ fundamentally: they are hemimetabolous (no pupal stage), bear diagnostic forceps rather than flexible cerci or none, have filiform antennae (not clubbed), and possess a 3-3-3 tarsal formula. Occasional confusion with small Blattodea is resolved by the absence of forceps and the different head orientation in cockroaches.

Notable and Iconic Species

Related Taxa

References

• Grimaldi D, Engel MS (2005) Evolution of the Insects. Cambridge University Press, New York, 755 pp.
• Beutel RG, Friedrich F, Ge SQ, Yang XK (2014) Insect Morphology and Phylogeny. Walter de Gruyter, Berlin, 516 pp.
• Haas F, Kukalová-Peck J (2001) Dermaptera hindwing structure and folding: New evidence for familial, ordinal and superordinal relationships within Neoptera (Insecta). European Journal of Entomology 98: 445–509.
• Jarvis KJ, Haas F, Whiting MF (2005) Phylogeny of earwigs (Insecta: Dermaptera) based on molecular and morphological evidence: reconsidering the classification of Dermaptera. Systematic Entomology 30: 442–453.
• Zhang ZQ (2011) Animal biodiversity: An outline of higher-level classification and survey of taxonomic richness. Zootaxa 3148: 1–237.

Frequently Asked Questions