Earwigs are the insects belonging to the order Dermaptera and are found throughout in America, Australia and Eurasia. Dermaptera is one of the smallest insect orders with only 1,800 species comprised in 12 families. Earwigs are characterized by presence of cerci, a pair of forceps like pincers on their abdomen and membranous wings folded under the short forewings hence the name of the order is Dermaptera which means skin wings. Some are parasites of mammals and although they have wings but they fly very rarely. They are nocturnal creatures hiding in the crevices during the day time and coming out in night in order to feed. They feed on small insects and plant material. They are also known to damage our foliage, flowers and valuable crops. They are known to undergo moulting 5 times in a year before they attain adulthood. Some species are also known to exhibit maternal care which is rare among insects. Mothers are known to take care of the eggs as well as the nymphs till they moult twice. As the nymphs grow sexual dimorphism becomes more pronounced which is basically observed in the shape of the pincers in both the sexes.
The fossils of earwigs have been obtained from different places. The name of the order has been derived from a Greek word meaning skin wings and the name was coined by Charles De Geer in 1773. The earwigs have got their name from the Old English word meaning ear insect. They are also known to hide themselves in the ear canal of humans. They are flat insects with elongated bodies measuring 7-50 mm in length although some species attain a length of 80 mm also. They have characteristic forceps like pincers at the end of their abdomens which is curved in males while straight in females. Pincers are used for defence as well as prey capture and remain protected under the wings when not in use. Antennae are thread-like and at least 10 segmented. Forewings are short and leathery while the hind wings are membranous and thin and some are without wings. Hind wings are used as a fan and remain protected under the forewings. The wings are rarely used for flight and the venation of wings is unique. Wingless species are sometimes considered as ectoparasites.
Earwigs are mostly scavengers while some are omnivores or predatory. The abdomen is flexible and muscular and is capable of opening and closing the forceps. Forceps are used for a variety of purposes like prey capture and copulation. They are known to feed upon other arthropods like lice, bluebottle flies, and ripe fruits. They are known to hide in holes, crevices and other dark places during the daytime. They are also seen patrolling the household walls and ceilings. During summers they are seen to roam around the sinks and the bathrooms. Some people believe that during night they crawl over humans and make burrows in the ears. They are harmless to humans. They are hemimetabolous insects and undergo incomplete metamorphosis and moult 4-6 times before attaining adulthood. The developmental stages between the moults are known as instars. The average lifespan of earwigs is about one year.
Mating occurs in the fall and the males and females live in crevices about 2.5 cm deep. After mating the sperms received from males remain inside the body of females for many months before they are fertilized. Before egg laying the males either leaves the crevices by their own or are driven out by the females. The female lays 20-80 pearly white eggs in 2 days. Some species are viviparous. The eggs when laid are oval and pearly white in colour but later on they turn kidney shaped and brown in colour. Eggs are 1 mm long and 0.8 mm wide. They are non-social insects but show maternal care. The mother is known to guard the eggs from the predator and she regularly cleans the eggs so that they may not get contaminated with microbial infection. Eggs are devoid of any scent. Eggs hatch after 7 days and the mother helps the nymphs while they come out by pushing the egg case. After hatching the nymphs spend some time in eating the egg case and then live with the mother. The nymphs resemble their parents but are smaller in size and are guarded by the mother till second moult. The nymphs feed on the food material regurgitated by the mother and on their own moulted skin. If the mother dies before the nymphs are ready to leave the crevice they feed on the dead body of the mother. After moulting for 5-6 times the nymphs become adults. The adults develop pincers as well as wings. Hind wings are made up of elytra which form the hard covering of the beetles.
They are frequently preyed upon by the birds, insectivorous mammals, amphibians, lizards, centipedes and spiders. Bars are also noticed to prey upon them. The primary predators of earwigs are tachinid flies whose larvae are endoparasites of them. Cannibalism is also well known among these animals. It is believed that they evolved about 208 million years ago.
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