Earwig

Earwig is the common name given to the insect order Dermaptera, characterized by membranous wings folded underneath short forewings, hence the literal translation of the order being "skin wings". The abdomen extends beyond the wings, and frequently ends in a pair of forceps-like structures called cerci. The order is relatively small among Insecta, with about 1,800 recorded species in 12 families. Earwigs are found in the Americas and Eurasia. There is no evidence that they transmit disease to humans or other animals.

Etymology

The scientific name for the order, Dermaptera, is Greek in origin, stemming from the words dermatos, meaning skin, and pteron, or wing. It was coined by Charles De Geer in 1773. The far more common term, earwig, is derived from the Old English ēare, which means "ear", and wicga, which means "insect." The name comes from the old wives' tale that earwigs burrowed into the brains of humans through the ear and therein laid their eggs.

Wicga is in turn related to wiggle, and ultimately to other words implying movement, including way and vehicle, all from PIE *wegh-. Other languages have words based on the same premises: German Ohrenkneifer, Ohrwurm, or Ohrenhöhler; Dutch oorwormen or oorwurmen; French perce-oreille; Danish ørentviste; Slovak ucholak (ucho = ear, lak = scare); Romanian urechelniță; and Hungarian fülbemászó ("crawler-into-the-ear"). 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 of earworm. Hungarian also uses the phrase fülbemászó dallam, meaning "a catchy melody". Some dialects of Swedish have related names for the earwig, but standard Swedish, by contrast, uses the word tvestjärt, which translates as "two-tail", not unlike the Geordie forkytail.

Characteristics

Most earwigs are elongated, flattened, and are dark brown. Lengths are mostly in the quarter- to half-inch range (10–14 mm), with the Saint Helena earwig reaching three inches long (80 mm). Cerci range from nonexistent to long arcs up to one-third as long as the rest of the body. Their mouthparts are designed for chewing, as in other orthopteroid insects. Flight capability in Dermaptera is varied, as there are species with and without wings. In those earwigs that have wings (are not apterous), the hindwings are folded in a complex fashion, so that they fit under the forewings. Most species of winged earwigs are capable of flight, yet they rarely do.

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

Behavior

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 arthropods, plants, ripe fruit, and garbage. Plants that they feed on typically include clover, dahlias,zinnias, butterfly bush, hollyhock, lettuce, cauliflower, 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 typically spend the daytime hours hiding in small, dark, and often moist areas. They can usually 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 that they can remain concealed during daylight hours. Picnic tables, compost and waste bins, patios, lawn furniture, window frames, or anything with minute spaces (even artichoke blossoms) can potentially harbor them. 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.

The only insect predator that preys on the earwig is the tachinidae, or tachinid fly, whose larvae live like parasites in the earwig's body. The eggs and nymphs can also be cannibalized by other earwigs.

Life cycle

Females generally lay eggs in early spring or autumn, in batches of 20 to 30 each, depending on the species. The mother will guard her eggs while they develop, clean them, protect them from predators, and eat fungi that begins to grow on them. The eggs usually incubate for about two weeks before hatching, but this period may last for a longer time if the eggs are laid over winter. When first laid, the eggs are white or cream-colored and oval-shaped, but right before hatching, they become kidney-shaped and brown. Each egg is approximately1 mm (0.04 in) tall and 0.8 mm (0.03 in) wide.

About ten days after the nymphs emerge, the mother will cease to care for them. Nymphs are similar in shape to adults, but are noticeably smaller. They are also wingless, and both genders have straight forceps, even though the males will develop curved forceps later on. Their abdomen consists of ten segments throughout this stage in life, but their antenna will grow as the nymphs pass through various instars.

After five to six instars, the nymphs will molt into adults. The adults range from 19 mm (0.75 in) to25 mm (0.98 in) tall, although this can differ depending on the species. The male's forceps will become curved, while the females remain straight. They will also develop their natural color, which can be anything from a light brown (as in the Tawny earwig) to a dark black (as in the Ringlegged earwig). Wings may also develop, though these are rarely used unless the earwig is disturbed. If the wings are present, the forewings are short and thick, covering the hindwings.

Classification

The order Dermaptera contains around 1,800 species, despite a record of fossilization that began 208 million years ago and numerous extant species. Although this fossil record is very sparse, four suborders within Dermaptera have been established. The actual phylogeny of the suborders remains a topic of debate, however, as all three extant suborders have distinct morphologies yet molecular evidence suggests Forficulina is paraphyletic through the exclusion of Hemimerina.

Archidermaptera: An extinct group whose fossil record is known only from the Jurassic, and is believed to be sister to the remaining earwig species. This suborder has tarsi with five segments (unlike the three found in the other suborders) as well as unsegmented cerci.
Arixeniina: Represented by two genera, Arixenia and Xeniaria, with a total of five species in them. As with Hemimerina, they are blind and wingless, with filiform segmented cerci. They are ectoparasites of various Southeast Asian bats, preferring guano from the genus Cheiromeles (i.e., "naked bulldog bats").
Forficulina: Contains the overwhelming majority of earwig species, grouped into nine families of 180 genera, including Forficula auricularia, the common European Earwig. Species within Forficulina have functional wings and are not parasites. The cerci are unsegmented and modified into large, forcep-like structures.
Hemimerina: Represented by two genera, Hemimerus and Araeomerus, with a total of 11 species. They are wingless and blind, with filiform segmented cerci. Hemimerina are viviparous ectoparasites, preferring the fur of African rodents in either Cricetomys or Beamys genera.

In 1985, biologist E.J. Popham developed a chart, shown on the right, explaining the approximate phylogenetic relationships between different families and suborders of earwigs. His system was based primarily on the characteristics of the earwig's genitalia.

Distribution

Approximately 99% of extant earwig species belong to the suborder Forficulina, and those that do not are small and parasitic. Thus, nearly all human encounters with earwigs are with Forficulina. For example, the European earwig, Forficula auricularia, was introduced to North America from Europe in 1907, and has since spread to every continent except Antarctica. Although they tend to prefer warmer, more tropical regions, they have still become a cosmopolitan species. Other examples of cosmopolitan species in Dermaptera include the Tawny earwig and the Ringlegged earwig.

Translation

The word "Earwig" occurs as such in the following languages: English, Simple English.

Translation(s) in other languages: Catalan: Dermàpter, Czech: Škvoři, Danish: Ørentvist, German: Ohrwürmer, Spanish: Dermaptera, Persian: گوش‌خیزک, French: Dermaptera, West Frisian: Earkrûper, Korean: 집게벌레목, Ido: Forfikulo, Icelandic: Klaufhalar, Italian: Dermaptera, Hebrew: צבתנאים, Latin: Dermaptera, Lithuanian: Auslindos, Hungarian: Fülbemászók, Dutch: Oorwormen, Dutch Low Saxon: Gaffeltaand, Japanese: ハサミムシ, Norwegian (Bokmål): Saksedyr, Norwegian (Nynorsk): Saksedyr, Polish: Skorki (owady), Portuguese: Dermaptera, Russian: Кожистокрылые, Slovenian: Strigalice, Serbian: Ухолаже, Sundanese: Cocopét, Finnish: Pihtihäntäiset, Swedish: Tvestjärtar, Tongan: Mokohula, Chinese: 蠼螋.