1902 Encyclopedia > Earwig

Earwig




EARWIG, a name, sanctioned by common error, applied under various modifications in different languages (e.g., Auricularia, Perce-oreille, Ohr-wurni, Oorblazer, Ormask, Oerentvist, Gusauo del oido, &c.) to the somewhat osculant insects comprised in the old Linnean genus Forflcula,—an error arising in the first instance probably from their invariable habit of secreting themselves in any cavity, of which they always endeavour to reach the innermost re-cess (instances being known of the common species hiding itself in the ear of a person sleeping in the open air), and strengthened by the popular exaggerated idea of the strength and attributes of the anal forceps peculiar to these insects.

Earwigs have been for some time of uncertain position in classifi-cation, having been even considered as worthy of the rank of a spe-cial separate order (Labidoures, Dumeril; Dcrmaptera, corrected to Dermatoptera, Leach ; and Fuplcxoptera, corrected to Euplectoptera, Westwood), but they are now generally recognized as forming a family, Forficulidoi or Forficularim, of the Orthoptera (the Locusts, Grasshoppers, Crickets, Cockroaches, Mantis, &c.) They have much the facies of the Brachelytra or Staphylinidoz in the Coleoptera (Beetles), from which order they differ in their pupa being active, resembling the perfect insect except in possessing only rudimentary wings, &c. ; also in the method of folding and neuration of the hinder wings, the possession of an anal forceps, and, as in the other Orthoptera, in the additional external lobe to their maxilla?. From all the other Orthoptera, apart from the anal forceps, they differ in having horizontal elytra covering the wings in repose as in beetles, and in the female not possessing a corneous ovipositor, and from most of them in the hind legs being not formed for jumping.

Of distinct species 250 are recognized, comprised in 34 genera (of which some are apparently needless); but it is highly probable that this represents a mere outline of the group, as scarcely any naturalists make them an object of study, and their geographical distribution is very extended. There are about 200 species in the collection of the British Museum alone, mostly unnamed, and not specially collected. They are found in the whole of Europe, in Syria and Asia Minor, Central Asia, Hindustan, Ceylon, Indo-China, China and Formosa, the Malay Archipelago, the Philip-pines, North, West, and South Africa to the Cape itself, Egypt, Zanzibar, Mauritius, Kamtchatka, Newfoundland, the North American States from New York to California (but comparatively rare, according to Packard), Mexico, Florida, Central America and the West Indies, South America from Columbia to Chili, New Guinea, North Australia, Tasmania, and New Zealand ; and species occur in such isolated localities as Madeira, the Canaries, St. Helena, Woodlark Island, the Solomon and Sandwich Isles, and Kergue-len's Island. As regards pre-historic times, a few fossil species have been found in the territories of Solenhofen, QSningen, and Italy in the Old World, and of the Rocky Mountains (Colorado) in the New. Seven species have been recorded from Great Britain, of which two are universally common, viz., Forfieula auricularia, the typical earwig, and the smaller Labia, minor. The former of these is found all over Europe, in Armenia, the Caucasus, and other parts of Asia, and in the eastern United States, being also recorded from Japan ; and the latter occurs in Europe, Western Asia, and North America. Another species, Labidura riparia, extends over the entire Old World.





All are of comparatively small size, and nearly all of ob-scure colours, mostly various shades of brown or dull yellows and reds : one South American species is white; another, from the Amazon, has blue metallic elytra, which are metallic also in another from Penang; a fourth exotic species is yellow, with black stripe ; and several have opaline or iridescent wings. Eccentricity of development is shown chiefly in the forceps, which in a Nicaraguan species are as long as the rest of the body ; in another South American form the abdomen is laterally toothed; a third has very long legs, being almost tipuliform; Apachys has the body as thin as cardboard.

Sexual differences are shown in the male by the greater development and armature of the forceps, or the tubercu-lated abdomen, which is composed of nine distinct segments, whereas only seven are evident in the female. The forceps have been observed to be used in arranging the wings, and are also supposed to be used as weapons of offence and defence, though it is difficult to understand how they could be of any practical assistance for either purpose. The lower wings have long attracted attention from their unexpectedly large size and fan-like structure; in the accompanying figure, a is the magnified open wing of the common earwig, b the same of the natural size, and c the wing closed, also of natural size. Although possessed of such ample organs of flight, Forfieula auricularia has seldom, if ever, been observed to make use of them, though there is evidence that it does fly; but the other common British species, Labia minor, is frequently seen on the wing, being often mis-taken for a brachelytrous beetle. It may be observed, that the possession of wings is apparently sexual in some cases, and that some species are entirely apterous.

Some few instances have been recorded of earwigs being carnivorous, devouring the larvae and pupae of wild bees and even their own species; but the majority are in a normal state certainly eaters of vegetable matter, congre-gating under bark, and destroying flowers, fruit, &c, often to a considerable extent. An instance M their adaptability to circumstances is afforded by Mr H. W. Bates's discovery of a large white species (above referred to) very common on white sandy beaches of the Brazilian river Pari, at Caripi, with a white Tetracha and a white mole cricket; this white-ness was permanent, and must not be confused with the light colour of recently disclosed individuals.

The female of the common earwig has long been noted for an exhibition of remarkable maternal instinct in defend-ing her progeny, not only brooding over her eggs, but caring for her newly hatched young.

The chief writers on Forficulidoe are Dohrn, in the Stettiner entomologisehe Zeitung for 1862 and following years, and quite recently, S. H. Scudder, in the Proceedings of the Boston Natural History Society, vol. xviii., the latter being the first to discuss these insects in a collective form. (E. C. R.)







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