COMMON EARWIG: CHARACTERISTICS, HABITAT, REPRODUCTION, NUTRITION - BIOLOGY - 2025

The common earwig (Forficula auricularia) is an insect of the order Dermaptera. It is characterized by presenting a pair of appendages on the back of the abdomen in the form of pincers or scissors, an elongated, flattened body and with three pairs of legs. Its coloration is dark reddish brown and can reach up to 25 mm in length.

It is a species that is located in humid environments and has twilight and nocturnal habits. It can be found under leaf litter and rocks, in wall crevices and under vases, among other places. It is native to Europe, West Asia and North Africa and has been accidentally introduced to the American continent.

Female common earwig Forficula auricularia, in defense position. Taken and edited from: Pudding4brains.

The common earwig is omnivorous, it feeds on anything, for example living or dead plant material, flowers, fruits, leaves, shoots, grains. It can also feed on other insects, living or dead, and it can even feed on insects of the same species (cannibalism).

It is a species considered a pest in some regions, where it can cause significant damage to orchards and gardens. It can also live indoors, causing tissue damage and contaminating food by walking on top of it and depositing its feces.

Its appearance is threatening due to the presence of the scissors or pliers (fences), however, these structures are intimidating organs because they do not have poison or great strength to serve as an offensive weapon.

characteristics

Adults

The common earwig is an insect with an elongated body and dorsoventrally depressed, with an average length of 12 to 15 mm, but which can reach up to 25 mm. The head is provided with a pair of antennae with 14-15 arms, shorter than the length of the body, and underdeveloped chewing mouthparts.

The pronotum is shell-shaped. The thorax has three pairs of legs in addition to two pairs of wings. The wings are well developed, but do not cover the abdomen. The body is reddish brown and the legs are lighter than the body.

The abdomen is visible dorsally, ending in a pair of appendages in the form of forceps or scissors that are called fences. The length of the abdomen, with enclosures included, exceeds the length of the thorax and head together. The fences are sexually dimorphic, longer, more robust, curved and crenulate in males; short, straight and smooth in females.

Polymorphism is also observed in males, with some specimens more robust and with more developed fences than others.

Nymph stages

According to some authors, the species has 4 nymphal stages while others maintain that they are actually 5. The nymphs are similar to adults, but lighter in color and their wings and fences are reduced or absent. The wings develop from the 4th nymphal stage. Body color darkens with each molt.

The antennae of the first and second nymph have 8 segments, then this number will be increased to 12 segments in the last nymph stage.

Eggs

Each egg has an elliptical to oval shape and is white or slightly yellow in color. At the time of the laying it measures 1.13 mm long by 0.85 mm high and its size increases as the moment of hatching approaches.

The female can lay more than 60 eggs in shallow galleries built into the ground.

Habitat and distribution

Habitat

Forficula auricularia is a terrestrial species that prefers humid and temperate climates, not supporting well the lack of humidity. Its optimum growth temperature is 24 ° C. Its habitat includes forests, agricultural and sub-agricultural areas. It is found in areas where there is no direct incidence of the sun's rays, such as litter, under rocks or logs.

Under normal conditions they are far from the houses unless there are excessively large populations or the environmental conditions are not very favorable. In the southernmost areas of the American continent they are frequent in nurseries, greenhouses and other agricultural structures.

During the reproductive season, the female prefers rich, well-draining soils, as she burrows in them to deposit her eggs. In houses they can be hidden under vases, cracks in walls and garbage cans.

Distribution

The species is cosmopolitan and its original distribution includes Europe (except the northernmost part of Scandinavia), East Asia and North Africa, although it is currently easily traceable globally.

Altitude can be distributed from sea level to more than 2824 m in height. It has nocturnal and twilight habits and remains hidden during daylight hours in dark areas, under weeds, rocks, leaves, in screams, etc.

It usually aggregates in large groups, except in the reproductive season, when the female isolates herself to care for and protect her offspring.

Taxonomy

The common earwig is an insect of the order Dermaptera included in the family Forficulidae. This family is divided into four subfamilies and a large group of species whose taxonomic location is uncertain (Incertae sedis). The genus Forficula, which was proposed by Linnaeus in 1758, is included in the subfamily Forficulinae.

According to some authors, the representatives of the Forficula auricularia species could actually be a complex formed by two sibylline species, one of which would be distributed in northern Europe and the mountainous regions of southern Europe, while the other would be inhabiting the most casualties to southern Europe.

Reproduction

The common earwig is a species of sexual reproduction, with separate sexes (dioecious) and sexual dimorphism. The males are larger and have larger and more arched fences, while in the females they are rectilinear and smaller. During the reproductive season, the female produces and secretes pheromones that attract the male.

Before copulation, Forficula auricularia males must perform a courtship ritual in which fences play an important role. The males wave the fences in the air and touch the female with them. If the female accepts the male's courtship, the male arches her abdomen below that of the female and positions her for copulation.

During copulation, the female can move and feed with the male attached to her abdomen. Fertilization is internal. During copulation, a male can confront the one who is copulating with the female and move her to take her place. Both males and females can carry out the sexual act with different partners.

The fertilized female lays about 50 eggs (although sometimes they can be more than 60) in a shallow gallery built in the ground, and performs parental care of them, cleaning their surface with her mouth to protect them from parasitic fungi. After approximately 70 days after laying, the nymphs hatch.

The female continues to care for the young by regurgitating the food to feed them. After the first molt, the nymphs emerge from the gallery and are able to get their own food. Females can sometimes lay a second set of eggs during the same reproductive period.

The species goes through 6 nymph stages in a period of 56 days and matures sexually, being able to reproduce in the next reproductive season.

Life cycle of the common earwig Forficula auricularia. Taken and edited from: Earwig_life_cycle_upwards.svg: Bugboy52.40derivative work: The Earwig (Talk - Contribs).

Nutrition

Forficula auricularia is an omnivorous species, with chewing-type mouthparts. It feeds on other organisms, both animals and plants, living or decomposing. In adverse conditions you can also practice cannibalism. The species is especially voracious in the last nymph stages.

The plant diet of this species includes lichens, algae, flowers, fruits, leaves, shoots and even seeds. Drill small, deep holes in the fruit. In homes it can cause damage to plants and their flowers and in nurseries it can cause considerable damage to various fruit and vegetable productions.

Regarding their carnivorous habits, their main prey are aphids, worms, spiders and protozoa. It is a voracious predator of these organisms in their natural environment, exerting control over their populations.

Bite

When the common earwig feels threatened, it raises the bottom portion of its abdomen as a deterrent to a potential predator. However, despite their dangerous appearance, these fences are not poisonous and their bite is not harmful, resembling rather a pinch.

There are no serious side effects or consequences from the insect bite. More damaging is its allergenic effect on some people. Allergic reactions can arise from direct contact with the animal by consuming food contaminated with its feces or by inhaling remains of the exoskeleton or the feces of the insect.

Forficula auricularia

In its natural environment, the common earwig feeds on a wide variety of insects and other arthropods, including aphids, which are phytophagous organisms that cause serious losses in the crops of some fruit trees, mainly apple and pear trees.

Due to this, many European farmers try to guarantee the presence of earwigs in their crops, increasing the number of places where they can hide and minimizing the use of pesticides that can affect them.

Additionally, there are management plans for the species to increase its populations in the event of the presence of an aphid plague. Common earwigs cause significant declines in insect pest populations, reducing or avoiding the use of pesticides.

After the aphid population has decreased, Forficula auricularia persists without causing significant damage to the plants.

In monitoring programs for the control of the aphid Eriosoma larigerum that affects apple orchards in Australia, the researchers found that the use of the common earwig, alone or in combination with other biocontrollers, was even more effective than the use of chemical agents, since aphids developed resistance against them.

Forficula auricularia

Despite being beneficial in their natural environments when controlling pest organisms, Forficula auricularia can become a pest in environments where it has been introduced due to the absence of its natural enemies. Earwig infestations, however, are rare.

Very abundant populations of this species can cause significant damage in greenhouses as well as in gardens, attacking young shoots of plants, fruits and even flowers.

In agricultural production centers where they become pests they can cause holes in the fruits that can then be colonized by other pathogens, devaluing the product. They can attack lettuce, strawberries, roses, among other plants, causing significant economic losses.

In the Falkland Islands they have become a significant plague that not only causes damage to gardens and greenhouses, but has even invaded hospital care centers, being able to seek shelter in inhalers and oxygen masks, causing additional security expenses to ensure that these equipment is suitable for use.

There are different ways to try to solve the problems caused by common earwig pests, such as habitat management, use of pesticides, and use of biocontroller organisms.

Male of Forficula auricularia. Taken and edited from: Luis Miguel Bugallo Sánchez (Lmbuga) Copyright: GFDL (GNU Free Documentation License) Published by / Publish by: Luis Miguel Bugallo Sánchez.

Habitat management

Among the cultural practices for the prevention of the common earwig infestation, agricultural producers use the cleaning of weeds, debris and other objects or structures that can serve as a refuge for the insect in the growing area and in the vicinity of it.

Repellants, such as kerosene, or beer and yeast baits, are also used to ward off insects or lure them into traps where they will drown.

Chemical control

There are no specific pesticides to act against Forficula auricularia, which is why the use of non-specific chemicals is necessary, which are generally very toxic and polluting.

Among the most commonly used pesticides are pyrethroids such as permethrin and cypermethrin, methamidophos and dimethoate. All of them act by contact or by ingestion and range from moderately toxic to very toxic for humans.

Biologic control

In its natural environment, the common earwig has numerous enemies that maintain control over its populations. Among the species that prey on Forficula auricularia are several species of flies of the Tachinidae family, such as Triarthria setipennis and Ocytata pallipes.

Some beetles Pterostichus vulgaris, Carabus nemoralis and Calosoma tepidum, the fungi Erynia forficulae and Metarhizium anisopliae as well as spiders, birds, toads and snakes can feed on the common earwig.

Among these species, tachyinid flies have been introduced as biological controllers in areas where the common earwig was not found before and in which it is now considered a pest.

For example, Triarthria setipennis was actively introduced in the Mediterranean area, several states of the United States of America and in Canada, managing to establish itself in some of these localities. Recently, a project to plant T. setipennis and Ocytata pallipes has been started in the Falklands to combat the common earwig.

References

1. Forficula auricularia (European earwig). Invasive species compendium. Recovered from: cabi.org.
2. Forficula auricularia. On Wikipedia. Recovered from en.wikipedia.org
3. Earwig (beetle). Recovered from: ecured.org.
4. Forficula auricularia (European earwig). Animal diversity web. Recovered from: animaldiversity.org.
5. P. Pavon-Gozalo, B. Mila, P. Aleixandre, J. Calderon, A. Zaldivar-Riveron, J. Hernandez-Montoya & M. Garcia-Paris (2011). Invasion of two widely separated areas of Mexico by Forficula auricularia (Dermaptera: Forficulidae). Florida Entomologist.
6. M. Kolliker (2007). Benefits and costs of earwig (Forficula auricularia) family life. Behavioral Ecology and Sociobiology.