Earwigs

Dermaptera. Spanish: Tijeretas.

Portuguese: Tesouras.

Earwigs are most easily recognized by the pincers or forcepslike cerci borne on the end of the abdomen. Their tips are strongly incurved, and they often have internal teeth. The cerci, normally larger in males than females, are short to almost as long as the body. They are used to capture and manipulate prey as well as for defense.

Dermaptera are otherwise monoton ously similar, somber-colored insects, most small to medium-sized (BL 1—2.5 cm), with chewing mouthparts, short threadlike or beadlike antennae, and unspecialized, similar legs. The fore wings are thickened and leathery and very short, meeting in a straight line down the back, almost like the elytra of some beetles. The hind, or flight wings are membranous and roughly circular and fold fanlike along many radially arranged creases. Appreciable anatomical variation in their body structure occurs primarily in the length and shape of the cerci, for example, in Metresura ruficeps, they are considerably longer than the body (fig. 5.12c). Some species have reddish (Carcinophora americana; fig. 5.12a) or yellow (Doru lineare; fig. 5.12b) areas on the fore wings.

Scientifically, this is one of the most neglected orders of insects, even though they are commonplace. Earwigs are, on the whole, not popular owing to their appearance and their unwelcome presence in gardens and homes. While they do cause some economic damage to stored food, roots, and shoots of tender young vegetables, some are predaceous and help to control populations of other more serious pests.

Urban earwigs are all adventives, thought to have made their way from Europe to Latin America with the earliest colonists,

Figure 5.12 EARWIGS, (a) Giant earwig (Carcinophora americana, Anisolabiidae). (b) Lined earwig (Doru lineare, Forficulidae). (c) Earwig (Metresura ruficeps, Anisolabiidae). (d) Shore earwig (Labidura riparia, Labiduridae). (e) Flat earwig (Sparatta pelvimetra, Sparattidae).

possibly in the ballast of ships or on nursery stock. One of the most widespread is the ring-legged earwig (Euborellia annulipes), so called because of the faint dark band around the femora and tarsi of each leg. Also characteristic are the dark antennae with the third to fifth subapical segments contrastingly pale. It is medium-sized (BL 1.5 cm) and wingless. The forceps of both sexes are very short and stout.

The shore (or striped) earwig (Labidura riparia; fig. 5.12d) is another nearly ubiquitous species. It is much larger than the other adventive species (BL 2.5 cm) and much lighter colored, generally tan and with dark, longitudinal stripes on the wings and dorsum of the abdomen, these markings contrasting sharply with the lighter adjacent areas. The forceps of males are almost as long as the abdomen, slender, and smoothly incurved. The species prefers damp habitats near water, including the sea. It is a general predator and scavenger and thus is to be considered a beneficial insect. It is also a good flier and often attracted to lights (Gross and Spink 1971).

The maritime earwig (Anisolabis mari-tima) also is a cosmopolitan species but is not so widespread as the foregoing as it occurs only near the seashore. It is fairly large (BL 2 cm), wingless, and with a shiny black to dark brown body and pale yellowish legs. The forceps are short, stout, and strongly incurved in the male.

It is strange that the European earwig (Forficula auricularia), so common almost everwhere else, has not succeeded in invading Latin America. It is known there from only a few, far nothern localities.

In the Neotropics, a much more varied and less-known native fauna lives in all climes and situations (Brindle 1968). The 300 or so remaining species, in fifty-eight genera, mostly belong to the family Labi-Mae (Reichardt 1968-1971; Steinmann 1973, 1975). The biggest genus is Marava.

The Pygidicranidae is a family of primitive earwigs, containing several South American species, whose closest relatives are in southern Africa (Brindle 1984).

The native earwigs dwell in all sorts of damp, secluded habitats, under stones, in rotten wood, in abandoned termite nests, in cracks in rocks, and the like. Sparatta (fig. 5.12e) is particularly flattened as an adaptation for living under bark. Earwigs are generally more conspicuous in damp forests, but there are desert and mountain dwellers as well. In contrast to their dull-colored semidomestic counterparts, many are marked with bright patterns, often spotted red or yellow.

Typically, earwigs are active at night, when they forage for food. Although most are omnivorous, a number appear to be at least partly carnivorous, feeding primarily on other insects. They use their forceps to seize and hold the victim and curve the abdomen forward to access the mandibles.

References

Brindle, A. 1968. The Dermaptera of Surinam and other Guyanas. Stud. Fauna Suriname Guyanas 36: 1—60.

Brindle, A. 1984. The Esphalmeninae (Dermaptera: Pygidicranidae): A groupof Andean and southern African earwigs. Syst. Entomol. 9: 281-292.

Gross, H. R., Jr., and W. T. Spink. 1971. Flight habits of the striped earwig Labidura riparia. Entomol. Soc. Amer. Ann. 64: 746-748.

Reichardt, H. 1968-1971. Catalogue of New World Dermaptera (Insecta). Dept. Zool. Sec. Agric. (Säo Paulo), Pap. Avul. Zool. 21: 183-193 (Pi. I. Introduction and Pygidicranoidea); 22: 35-46 (Pt. II. Labioidea, Carcinophori-dae); 23: 83-109 (Pt. III. Labioidea, Labi-idae); 24: 161-184 (Pt. IV: Forficuloidea); 24: 221-257 (Pt. V: Additions, corrections, bibliography and index).

Steinmann, H. 1973. A zoogeographical checklist of world Dermaptera. Pol. Entomol. Hungarica 26: 145-154.

Steinmann, H. 1975. Suprageneric classification of Dermaptera. Acad. Sei. Hungaricae Acta Zool. 21: 195-220.

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