''Forficula auricularia'', the common earwig or European earwig, is an

omnivorous An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nut ...

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pa ...

in the family Forficulidae. The European

earwig Earwigs make up the insect order Dermaptera. With about 2,000 species in 12 families, they are one of the smaller insect orders. Earwigs have characteristic cerci, a pair of forcep-like pincers on their abdomen, and membranous wings folde ...

survives in a variety of environments and is a common household insect in North America. The name ''earwig'' comes from the appearance of the hindwings, which are unique and distinctive among insects, and resemble a human ear when unfolded; the species name of the common earwig, ''auricularia'', is a specific reference to this feature. They are considered a household pest because of their tendency to invade crevices in homes and consume pantry foods, and may act either as a pest or as a beneficial species depending on the circumstances (see below). ''Forficula auricularia'' is reddish-brown in color, with a flattened and elongate body, and slender, beaded antennae. An obvious feature of earwigs is the pair of 'pincers' or forceps at the tip of the flexible abdomen. Both sexes have these pincers; in males they are large and very curved, whereas in females they are straight. Nymphs are similar to adults in appearance, but their wings are either absent or small

Morphology

''Forficula auricularia'' has an elongated flattened brownish-colored body, with a shield-shaped pronotum, two pairs of wings and a pair of forcep-like cerci. They are about 12–15 mm long. The second tarsal segment is lobed, extending

distal Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...

ly below the third tarsal segment. The antenna consists of 11–14 segments, and the mouth parts are of the chewing type. Adult males are polymorphic in body weight and head width, as well as cercus length and width. The male forceps are very robust and broadened basally with crenulate teeth. The female forceps are about 3 mm long, and are less robust and straighter. The cerci are used during mating, feeding, and self-defense. Females also have tegmina of about 2 mm in length. Third

instar An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ...

or older

nymphs A nymph ( grc, νύμφη, nýmphē, el, script=Latn, nímfi, label=Modern Greek; , ) in ancient Greek folklore is a minor female nature deity. Different from Greek goddesses, nymphs are generally regarded as personifications of nature, are ...

that have lost one branch of cerci are capable of regenerating it in form of a straight structure. Males with asymmetrical forceps are called gynandromorphs or

hermaphrodite In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many taxonomic groups of animals (mostly invertebrates) do not have ...

s because they resemble females.

Distribution

Native to Europe, western Asia and probably North Africa, ''Forficula auricularia'' was introduced to

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...

in the early twentieth century and is currently spread throughout much of the continent. In North America, European earwigs comprise two

sibling species In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...

, which are reproductively isolated.Wirth T., et al. (1998)
Molecular and reproductive characterization of sibling species in the European earwig (''Forficula auricularia'').
''Evolution'' 52(1) 260–65. Populations in cold continental climates mostly have one

clutch A clutch is a mechanical device that engages and disengages power transmission, especially from a drive shaft to a driven shaft. In the simplest application, clutches connect and disconnect two rotating shafts (drive shafts or line shafts). ...

per year, forming species A, whereas those in warmer climates have two clutches per year, forming species B. European earwigs are most commonly found in

temperate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout ...

climates, since they were originally discovered in the

Palearctic The Palearctic or Palaearctic is the largest of the eight biogeographic realms of the Earth. It stretches across all of Eurasia north of the foothills of the Himalayas, and North Africa. The realm consists of several bioregions: the Euro-Sib ...

region, and are most active when the daily temperature has minimal fluctuation.Capinera, J. 2001. ''Handbook of Vegetable Pests''. Academic Press, San Diego, CA.

Behavior

European earwigs spend the daytime in cool, dark, inaccessible places such as flowers, fruits, and wood crevices. Active primarily at night, they seek out food ranging from plant matter to small insects. Though they are

, they are considered as scavengers rather than predators. Often they consume plant matter, though they have also been known to feed on

aphid Aphids are small sap-sucking insects and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...

spider Spiders (order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species ...

s, insect eggs, and dead plants and insects, among other things. Their favorite plants include the common crucifer ''

Sisymbrium officinale ''Sisymbrium officinale'', the hedge mustard, (formerly ''Erysimum officinale'') is a plant in the family Brassicaceae. Description It is distinct from the mustard plants which belong to the genus '' Brassica''. ''S. officinale'' is similar to ...

'', the white clover ''

Trifolium repens ''Trifolium repens'', the white clover, is a herbaceous perennial plant in the bean family Fabaceae (otherwise known as Leguminosae). It is native to Europe, including the British Isles,Clapham, A.R., Tutin, T.G. and Warburg., E.F. 1968. ''Excursio ...

'', and the dahlia ''

Dahlia variabilis ''Dahlia pinnata'' (''D.'' × ''pinnata'') is a species in the genus ''Dahlia'', family Asteraceae, with the common name garden dahlia. It is the type species of the genus and is widely cultivated. Description ''Dahlia pinnata'' is a perennial ...

''. They also like to feed on molasses, as well as on

nonvascular plants Non-vascular plants are plants without a vascular system consisting of xylem and phloem. Instead, they may possess simpler tissues that have specialized functions for the internal transport of water. Non-vascular plants include two distantly re ...

lichen A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular micr ...

. They prefer meat or sugar to natural plant material even though plants are a major natural food source. European earwigs prefer aphids to plant material such as leaves and fruit slices of apple, cherry and pear. Adults eat more insects than do nymphs. Although ''F. auricularia'' have well-developed wings, they are fairly weak and are rarely, if ever, used. Instead, as their main form of transportation, earwigs are carried from one place to another on clothing or commercial products like lumber, ornamental shrubs and even newspaper bundles.

Reproduction

A male finds prospective mates by

olfaction The sense of smell, or olfaction, is the special sense through which smells (or odors) are perceived. The sense of smell has many functions, including detecting desirable foods, hazards, and pheromones, and plays a role in taste. In humans, ...

. He then slips his cerci under the tip of the female's abdomen so that his and her ventral abdominal surfaces are in contact with each other, while both face in opposite directions. If not disturbed, pairs can stay in this mating position for many hours. Matings occurred frequently among clustered individuals particularly in locations that allow both partners to cling to a surface. Under laboratory conditions, the mating season peaked during August and September, and a single mating event enabled females to lay fertilized eggs. European earwig

look very similar to their adult counterparts except that they are a lighter color. The young go through four nymphal stages and do not leave the nest until after the first

moult In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer ...

. European earwigs

overwinter Overwintering is the process by which some organisms pass through or wait out the winter season, or pass through that period of the year when "winter" conditions (cold or sub-zero temperatures, ice, snow, limited food supplies) make normal activi ...

about 5 mm below the surface of the ground. The female earwig lays a clutch of about 50 eggs in an underground nest in the autumn. She enters a dormant state and stays in the nest with the eggs. The female cares for her young by shifting the eggs about and cleaning them to avoid fungal growth. In the spring, she spreads them out into a single layer and the young emerge from the eggs. She guards them until they reach maturity after about one month. It is possible for the female to lay a second brood in one season and by the end of August all of the young reach maturity.

Habitat

European earwigs survive well in cool, moist habitats and have an optimum mean growth temperature of . Their daily abundance in a given year has been linked to factors such as temperature, wind velocity and the prevalence of easterly winds. The development of European earwigs also depends on temperature. Thus, the occurrence of European earwigs can be predicted based on weather parameters. Hibernating adults can tolerate cool temperatures, but their survival is reduced in poorly drained soils such as clay. To avoid excessive moisture, they seek the southern side of well-drained slopes. Sometimes they also occupy the hollow stems of flowers where the soil is poorly drained. Their eggs are capable of resisting damage from cold and heat.

Agricultural impact

''Forficula auricularia'' has been known to cause significant damage to crops, flowers, and fruit orchards when at high population levels. Some of the commercially valuable vegetables it feeds upon include cabbage, cauliflower, chard, celery, lettuce, potato, beet, and cucumber among others. Earwigs readily consume corn (maize) silk and can damage the crop. Among fruits, they have been found to damage apple and pear orchards. They damage young plum and peach trees in early spring, when other food is scarce, by devouring blossoms and leaves at night. It is not uncommon to find them wedged among petals of fresh cut carnations, roses, dahlia and zinnia. In addition to all of the agricultural problems caused, humans are not very fond of ''F. auricularia'' because of its foul odor and annoying propensity to aggregate together in or near human dwellings. Control of ''F. auricularia'' has been attempted using some of its natural enemies, including the

parasitoid In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable str ...

fly '' Bigonicheta spinipenni'', the fungi '' Erynia forficulae'' and '' Metarhizium anisopliae'', as well as many species of birds. The tachinid flies '' Triarthria setipennis'' (Fallen) and '' Ocytata pallipes'' have been introduced in North America to control ''F. auricularia'' in the 1920s.Bugguide.net. Species Forficula auricularia - European Earwig
/ref> Insecticides have also been successfully implemented, although commercial products are rarely targeted specifically towards earwigs. Multipurpose

insecticide Insecticides are substances used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. Insecticides are used in agriculture, medicine, industry and by consumers. Insecticides are claimed t ...

s for control of earwigs, grasshoppers, sowbugs and other insects are more common. Diazinon, an

organophosphate In organic chemistry, organophosphates (also known as phosphate esters, or OPEs) are a class of organophosphorus compounds with the general structure , a central phosphate molecule with alkyl or aromatic substituents. They can be considered ...

insecticide, has been known to continue killing ''F. auricularia'' up to 17 days after initial spraying. Humans have, however, found beneficial uses of ''F. auricularia'' in the pest management of other insects. The European earwig is a natural predator of a number of other agricultural pests, including the pear psyllid and several aphid species, and in this regard has been used to control outbreaks of such organisms. Damage to crops by ''F. auricularia'' is limited as long as there are high population levels of their insect prey.Vickery, V. and D. Kevan. 1986. ''The Insects and Arachnids of Canada, Part 14''. Canada Dept. of Agriculture, Ottawa, ON.

References

External links

ARKive: Images of Life on Earth
- ''Forficula auricularia'' fact page as well as photos and video
Encyclopedia of Life
- ''Forficula auricularia'' images and facts
Royal Horticultural Society- Gardening advice: Earwigs
- Gardening advice in relation to ''Forficula auricularia'' {{DEFAULTSORT:Forficula Auricularia Forficulidae Household pest insects Insects described in 1758 Insects of Europe Taxa named by Carl Linnaeus da:Ørentvist