General Characteristics

In 1773 DeGeer coined the term Dermaptera (but used the name for all orthopteroids). Kirby in 1815 introduced the name in its current sense, as a small insect order of about 2000 described species. The oldest known examples of dermapterans are Jurassic fossils dating from about 208 mya. These elongate, slender, hemimetabolous (incompletely metamorphic) insects have chewing mouthparts, three-segmented tarsi (in extant groups), (usually) compound eyes, and no ocelli. The presence of abdominal cerci makes them easy to distinguish from beetles. The cerci are typically forcepslike (though they are filiform in at least some parasitic forms) and are sexually dimorphic (Fig. 1). The forceps are used for a variety of purposes, including prey capture,

FIGURE 2 Female ringlegged earwig (Euborellia annulipes), brooding over her clutch of eggs.

defense, fighting, and as aids in copulation and in folding of hind wings. Earwigs are diploid (i.e., they have a double set of chromosomes); males are heterogametic (i.e., they produce gametes with different sex chromosomes, e.g., X and Y).

Some earwig species are wingless as adults, but most have short front wings (tegmina) that do not cover the abdomen. The derivation of the name "dermaptera" (derma, skin, ptera, wing) refers to the thickened or "skinlike" front wings. The hind wings are unlike those of any other group of insects: they are semicircular and membranous, with radially arranged veins. They fold fanlike beneath the front pair when the insects are at rest (Fig. 1). The derivation of the common name (earwig) may be a corruption of "earwing," in reference to the hind wing resemblance to a human ear. Alternatively, it could be a reference to the ancient Anglo-Saxon legend that these insects crawl in ears of sleeping humans. Additionally, the forceps of some species look like instruments once used for piercing women's ears for earrings.

Earwigs typically display parental care of offspring (although there are almost no observations of maternal care in the viviparous, ectoparasitic forms). Eggs are typically deposited in soil (or protected whorls of monocotyledonous plants); the females "roost" on the eggs until the young hatch and then they care for them (Fig. 2). The period of maternal care appears to be a time of nonfeeding of the brooding female; physiologically, her levels of both juvenile hormone and ecdysteroids (see later) are likely low during the period of egg care.

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