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Earwig

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Earwig is the common name given to the insect order Dermaptera characterized by membranous wings folded underneath short leathery forewings (hence the literal name of the order—"skin wings"). The abdomen extends well beyond the wings, and frequently, though not always, ends in a pair of forceps-like structures termed cerci. With about 1,800 recorded species in 10 families, the order is relatively small among Insecta. Earwigs are, however, quite common globally. There is no evidence that they transmit disease or otherwise harm humans or other animals, despite their nickname pincher bug.

Etymology

Earwig is derived from Old English ēare "ear" and wicga, 'insect'. (Wicga is in turn related to wiggle, and ultimately to other words implying movement, including way and vehicle, all from PIE *wegh-.) The name comes from the old wives' tale that earwigs burrow into the brains of humans through the ear and therein lay their eggs. Though the notion has no basis in fact, earwigs, being curious omnivores predisposed to hiding in small holes, may well have crawled into a human ear at some time or other seeking a warm humid crevice.

Other languages have words based on the same premise: German Ohrwurm, French perce-oreille, Danish ørentviste. English has derived a verb from this, to earwig, meaning 'to fill someone's mind with prejudice by insinuations' or 'to attempt to influence by persistent confidential argument or talk'. The German word Ohrwurm has the derived meaning 'an annoying tune which I can't get out of my head' (see earworm).

Classification

Four suborders within the Dermaptera have been established:

  • Archidermaptera: Has a fossil record extending into the Jurassic, with fossils from that period. These have unsegmented cerci and tarsi with 4-5 segments.
  • Forficulina: The largest and most familiar group. The cerci are unsegmented, and modified into large, forcep-like structures.
  • Hemimerina: Represented by one genus, Hemimerus, with filiform segmented cerci and are wingless, blind and viviparous and ectoparasitic on African rodents
  • Arixenina: Represented by two genera, Arixenia and Xeniaria. As with Hemimerina, they are blind, wingless ectoparasites with filiform segmented cerci. They are ectoparasites of various Southeast Asian bats, particularly of the genus Cheiromeles (i.e., "naked bulldog bats").

Appearance and behaviour

Most earwigs are elongated, flattened, and are dark brown. Lengths are mostly in the 10–14 mm range, with the St. Helena earwig reaching 80 mm. Cerci range from nonexistent to long arcs up to one-third as long as the rest of the body. As in other orthopteroid insects, mouthparts are adapted for chewing. When earwigs have wings (are not apterous), the hindwings are folded in a complex fashion, so that they fit under the forewings. Earwigs rarely fly.

The abdomen of the earwig is flexible and muscular. It is capable of maneuvering as well as opening and closing of the forceps. The forceps are used for a variety of purposes. In some species, the forceps have also been observed in use for holding prey, and in copulation. The forceps tend to be more curved in males than in females.

Most earwigs found in Europe and North America are of the species Forficula auricularia, the European or common earwig, which is distributed throughout the cooler parts of the northern hemisphere. This species feeds on other insects, plants, ripe fruit, and garbage. Plants they feed on typically include clover, dahlias, zinnias, butterfly bush, hollyhock, lettuce, strawberry, 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 corn. Typically they are a nuisance because of their diet, but normally do not present serious hazards to crops. Some tropical species are brightly colored. Occasionally earwigs are confused with cockroaches because of their cerci and their long antennae.

Earwigs are generally nocturnal and can be seen patrolling household walls and ceilings. Interaction with earwigs at this time results in a defensive free fall to the ground below, and the subsequent scramble to a nearby cleft or crevice.

Earwigs are also drawn to damp conditions. During the summer, they can be found around sinks and in bathrooms. Earwigs tend to gather in shady cracks or openings or anywhere they can remain concealed in daylight hours. Picnic tables, compost and waste bins, patios, lawn furniture, window frames or anything with minute spaces (even artichoke blossoms) can potentially harbor these unwanted residents. Upon gaining entry to the basement and living areas of the home, earwigs can easily find cover in undisturbed magazine and newspaper piles, furniture/wickerwork, base boards, carpeted stairways, pet food dishes, and even inside DVD cases and keyboards. Earwigs are inclined to take risks and are exploratory creatures but are overly unaware of the consequences and are often found trapped in poison baited cups or buckets of soapy water.

Pest control

While earwigs can be considered in some ways a beneficial part of the garden, especially when they prey on other insects, they can become a nuisance because of their habit of hiding within leaves and feeding on soft plant tissues. Since they prefer cool, moist places, a rolled up damp newspaper placed where earwig activity is suspected can be effective in collecting them. The newspaper can then either be discarded or shaken out. Placing diatomaceous earth in key spots around the home (bathroom, baseboards, window frames) can be a long-term repellent.

Another method of removing earwigs is by utilizing their attraction to vegetable oil. Putting vegetable oil in a pie tin and burying it up to the rim of the tin is an effective way of capturing them. Another effective method of earwig control is to take steps to control the population before they hatch by removing rotting underbrush and spraying with commercially available insecticidal nematodes, which invade the earwigs in their nymphal stage and infect them with a lethal bacterium.

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Last updated on Thursday March 06, 2008 at 19:02:14 PST (GMT -0800)
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