Order Dermaptera - Earwigs

• Common Earwig
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Elongate insects with biting mouthparts and long, slender antenae. Forewings modified into short, leathery 'wing-cases' (elytra) which meet in the mid-line and reach only a short way down the body. The large, membranous hindwings are semi-circular with radial veins and when not in use they are folded in a complex manner under the small front wings, although many species are entirely wingless. The cerci are modified into stout forceps or pincers at the end of the abdomen, more strongly curved in the male than in the female (see below). Metamorphosis is slight, normally with four nymphal stages. This is a small Order of about 1,000 species - only four of these are native to the British Isles.

Description. Mainly brown in colour, up to 17 mm long. The hind wings are well developed, although this species appears reluctant to fly.

Biology. Found in many different habitats and mainly nocturnal. They hide by day in narrow crevices under stones, loose bark and similar places. Frequently enter houses by crawling through the small gaps around doors and opening windows. Feed on animal and plant material, but probably do more good than harm, since soft bodied insect pests like aphids are eaten just as readily as plant tissue. However, they do have the annoying habit of chewing flower petals. The female shows maternal care for the eggs and young nymphs. Batches of 20-50 eggs are laid in the soil and the female earwig looks after her clutch until the eggs hatch. She then continues to feed and tend the young nymphs up to about their second moult. After this stage the nymphs are well able to fend for themselves. The full life cycle takes a year. The function of the pincers at the end of the abdomen is uncertain. Earwigs have been reputed to use these structures for opening and closing the wings and to capture prey, but their principal role is probably for defence and as grasping organs during mating. When the insects are disturbed or molested, the abdomen is often raised upwards and the pincers held wide open over the body in a threatening manner.

Distribution. Common and widespread throughout Europe, including the British Isles. It has been introduced to North America and New Zealand, and is now well established in both these regions.

Photo: Jim Kalisch, Department of Entomology, University of Nebraska-Lincoln ©

Male (left)
&
Female (right)
 
(note how the pincers differ
in shape between the sexes)