Earwigs: Dermaptera

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EARWIGS: Dermaptera

EUROPEAN EARWIG (Forficula auricularia): SPECIES ACCOUNTS
ST. HELENA EARWIG (Labidura herculeana): SPECIES ACCOUNTS

PHYSICAL CHARACTERISTICS

Earwigs are related to crickets, grasshoppers, and stick insects. They are long, slender, flattened insects that come in various shades of brown or black, sometimes with patterns of light brown or yellow. A few species are metallic green. Most earwigs measure between 0.16 to 3.2 inches (4 to 78 millimeters) in length, without the pinchers (PIN-churs), or grasping claws. The head is distinctive and has chewing mouthparts that are directed toward the front. The antennae (an-TEH-nee), or sense organs, are long, thin, and threadlike. The compound eyes, eyes with many lenses, are usually well developed. However, simple eyes, those that have only single lenses, are absent. Most adult earwigs have four wings. When present, the forewings, or front wings, are short, thick, and leathery and cover a pair of tightly folded, fanlike flight wings that are shaped like the human ear. Their long, flexible abdomen ends in a pair of strong pinchers. The pinchers of the adult male are larger and thicker than those of the females and young earwigs or larvae (LAR-vee).

The young earwig, or larva, resembles the adult except that the larva may not have wings. Larvae of wingless species are distinguished from the adults by their smaller size. Their pinchers are nearly straight and are similar to those of the female.

GEOGRAPHIC RANGE

There are approximately 1,800 species of earwigs found throughout the world, except in the Arctic and Antarctic. They are especially common in the tropics and subtropics. Twenty-two species live in the United States and Canada.

HABITAT

Most earwigs live in moist crevices (KREH-vuh-ses) of all kinds, including under bark, between leaves, and under stones. Some species live on the furry bodies of giant rats or bats as parasites, or animals that live on another organism or host and obtain food from it.

DIET

Most earwigs are scavengers (SKAE-vihn-jers) and predators (PREH-duh-ters), feeding both on living and dead insects and plants. Some species eat mainly plants, while others eat mostly insects, such as chinch bugs, mole crickets, mites, scales, aphids, and caterpillars. Parasitic species scavenge bits of dead skin or fungi growing on the bodies of giant rats or feed on skin secretions of bats.

BEHAVIOR AND REPRODUCTION

Earwigs are active at night. They hide during the day in moist, dark, tight-fitting places under stones, logs, and bark. They also seek shelter inside cracks in the soil or deep inside flowers. Other species live in caves or actively burrow through the soil. Earwigs often live in groups of dozens or hundreds of individuals. Both males and females use their pinchers for grooming, capturing prey, and courtship. The pinchers are also used to help fold and unfold the wings.

Earwigs will defend themselves by using their powerful pinchers as a weapon. Other species have glands in their abdomens that spray a foul-smelling fluid at attackers up to 2.9 to 3.9 inches (75 to 100 millimeters) away.

A LIFE OF RATS AND BATS

Parasitic earwigs spend their entire lives on the bodies of their host animals. These small (0.4 inches or 10 millimeters) insects are blind and have short, bristlelike pinchers. They cling to the fur of their hosts with special claws. They feed only on bits of skin and fungus growing on the bodies of African giant rats or on the skin secretions of just one species of Asian bat. Unlike all other earwigs, parasitic earwigs do not lay eggs but bear live young.

After mating, females dig a chamber in the soil or leaf litter to lay their eggs. Some earwigs guard the eggs and will frequently turn and lick them to keep them moist and free of mold. After hatching, the young larvae may remain with their mother. She will swallow food and then spit it up to offer it to the larvae. Earwig larvae closely resemble the adults but lack wings. They will molt, or shed their exoskeletons or hard outer coverings, four to six times before reaching adulthood. Earwigs produce one or two generations every year.

EARWIGS AND PEOPLE

The name "earwig" is thought to come from the mistaken belief that this insect likes to crawl into and hide in the ears of sleeping people. Earwigs are harmless and do not bite people, although some larger species can pinch. Most earwigs are not considered important pests. Earwigs— like cockroaches—have been transported throughout the world by ships and in cargo. They will cause damage in gardens by feeding on flowers and leaves. Sometimes earwigs are helpful because they eat other insects and mites that are harmful to plants. Occasionally, large numbers of earwigs may invade homes, but they cause little harm. Still, many people waste time and money trying to control earwigs.

CONSERVATION STATUS

One species, the St. Helena earwig (Labidura herculeana), is listed as Endangered by the World Conservation Union (IUCN). It may even be extinct and no longer exist.

EUROPEAN EARWIG (Forficula auricularia): SPECIES ACCOUNTS

Physical characteristics: The European earwig is reddish brown to nearly black with yellowish brown wing covers, legs, and antennae. The pinchers are reddish brown. Adults are fully winged and measure 0.47 to 0.59 inches (12 to 15 millimeters) in length, without the pinchers. The male's pinchers are broad with tiny notches at the bases and are sometimes as long as the abdomen and curved. They vary in size from 0.16 to 0.31 inches (4 to 8 millimeters) long. The pinchers of the female are thinner and crossed, measuring 0.12 inches (3 millimeters). The larvae look just like the adults but are smaller and lack wings.

Geographic range: The European earwig was originally known from Europe, western Asia, and North Africa. It now lives in East Africa, North America, the East Indies, Australia, New Zealand, Chile, and Argentina.

Habitat: The European earwig hides among petals or leaves of garden plants or inside damaged fruit, shrubs, along fences, in woodpiles, around bases of trees, and behind loose boards on buildings.

Diet: They feed on plants, ripe fruit, lichens, fungi, and other insects.

Behavior and reproduction: Adults are fully winged but seldom fly. They remain hidden during the day and forage at night for food and water.

In North America females lay batches of fifty to ninety eggs in chambers dug in moist soil from November to January. Another clutch with fewer eggs is laid in March or April. Depending on temperature the eggs will hatch in forty to fifty days. Females guard the eggs until they hatch. The larvae take about forty to fifty days to reach adulthood. They molt four times during this period. There is only one generation produced each year. Both larvae and adults are found throughout most the year, but adults are usually found in fall.

European earwigs and people: This species is not considered to be much of a pest in Europe, but in the United States they will attack flower crops, butterfly bushes, hollyhocks, lettuce, strawberries, celery, potatoes, sweet corn, roses, seedling beans and beets, and grasses. They are considered helpful when they eat aphids and other plant pests.

Conservation status: This species is not endangered or threatened. ∎

ST. HELENA EARWIG (Labidura herculeana): SPECIES ACCOUNTS

Physical characteristics: This species is the largest earwig in the world. They are black with reddish legs and wing covers, with no hind wings. Their bodies measure between 1.44 to 2.13 inches (36 to 54 millimeters). Their pinchers add an additional 0.6 to 0.96 inches (15 to 24 millimeters). The largest known specimen is a male measuring 3.1 inches (78 mm).

Geographic range: The species is found on Horse Point Plain in the extreme northeastern portion of the island of St. Helena. St. Helena is located in the Atlantic Ocean, almost midway between the continents of Africa and South America.

Habitat: The St. Helena earwig lives in a dry and barren habitat, with stony soil, bushes, and tufts of grass.

Diet: Nothing is known.

Behavior and reproduction: Living specimens have been found under stones or near burrows in the soil. St. Helena earwigs are nocturnal and active during summer rains. During the dry season they remain underground.

St. Helena earwigs and people: This species is of scientific interest because it is the largest earwig in the world.

Conservation status: The St. Helena earwig is listed as Endangered by the World Conservation Union (IUCN). Endangered means it faces a very high risk of extinction in the wild. It is in danger because it is found only on one part of a very small and remote island. This species was last seen in 1967 and may not still be alive today. More study is needed to determine whether or not this species still exists and, if so, how to protect it from becoming extinct. ∎

FOR MORE INFORMATION

Books:

Helfer, J. R. How to Know the Grasshoppers, Crickets, Cockroaches, and Their Allies. New York: Dover Publications, 1987.

Holm, E., and C. H. Scholtz. Insects of Southern Africa. Durban, South Africa: Butterworths, 1985.

Rights, M. Beastly Neighbors: All about Wild Things in the City, or Why Earwigs Make Good Mothers. Boston: Little, Brown, 1981.

Tavoloacci, J., ed. Insects and Spiders of the World. New York: Marshall Cavendish, 2003.

Periodicals:

Hoffman, K. M. "Earwigs (Dermaptera) of South Carolina, with a Key to the Eastern North American Species and a Checklist of the North American Fauna." Proceedings of the Entomological Society of Washington (1987) 89: 1–14.