The earwigs are an order (Dermaptera) of insects characterized by large membraneous wings folded underneath short leathery forewings (thus the literal name of the order – “skin wings”). The abdomen extends well beyond the wings, and frequently ends in a pair of forceps-like cerci. With about 1,800 recorded species in 10 families, the order is relatively small among the Insecta, but the earwigs themselves are quite common throughout the world, often finding their way into houses, where they are usually first noticed scurrying across the floor.
The name “earwig” is said to originate from an old belief that earwigs crawl into people’s ears and lay eggs in the brain. Earwigs do tend to prefer being in hidden places, and on very rare occasions have been known to find their way into a human ear canal, but only as far as the eardrum and certainly never into the brain. Actually, the name comes from the ancient use of pulverized earwigs as medicine to treat diseases of the ear, resulting in the Late Latin name auricula. When much later the origin of the name was forgotten, a false explanation was found. Another explanation is that it is an alteration of “ear-wing”, after the shape of the hind wings when unfolded; but it’s important to note that the Oxford English Dictionary states unequivocally that the name is derived from Old English words for ear and wiggle “from the notion that it penetrates into the head through the ear.”
Most earwigs are elongated and low to the ground, and are dark brown in color. Lengths are mostly in the 10-14 mm range, with a species of St Helena reaching 80 mm. The cerci range from nonexistent, to long arcs up to 1/3 as long as the rest of the body. Mouthparts are adapted for chewing. The hind wings are folded in a complicated fashion so that they fit under the forewings; but despite all the trouble, earwigs rarely fly.
The earwig’s abdomen is flexible and muscular, and capable of both maneuvering and opening/closing the forceps. The forceps seem to be used for a variety of purposes. Their role in self-defense is familiar to every child whose first grab at a passing earwig resulted in a pinch – more surprising than painful, the forceps not being particularly strong. In some species, the forceps have also been observed in use for holding prey, to unfold the wings, and in copulation. There is also conclusive proof that earwig males grow a spare set of genitals in the event of his first set being snapped off or otherwise damaged.
Fossil earwigs are known from the Jurassic period (between 200 and 150 million years ago)–about 70 specimens having been found as of 2003.