Earwigs

Earwigs make up the insect order Dermaptera, found throughout the Americas, Eurasia, Australia and New Zealand. With 1,800 species in 12 families, they are one of the smaller insect orders. Earwigs have characteristic cerci, a pair of forceps pincers on their abdomen, and membranous wings folded underneath short forewings, hence the scientific order name, “skin wings.” Some groups are tiny parasites on mammals and lack the typical pincers.

Earwigs rarely use their flying ability. Earwigs are nocturnal; they often hide in small, moist crevices during the day, and are active at night, feeding on a wide variety of insects and plants. Damage to foliage, flowers, and various crops is commonly blamed on earwigs, especially the common earwig Forficula auricularia. Earwigs have five molts in the year before they become adults.
Many earwig species display maternal care, which is uncommon among insects. Female earwigs may care for their eggs, and even after they have hatched as nymphs will continue to watch over offspring until their second molt. As the nymphs molt, sexual dimorphism such as differences in pincer shapes begins to show.

Earwigs are abundant and can be found throughout the Americas and Eurasia. The common earwig was introduced into North America in 1907 from Europe, but tend to be more common in the southern and southwestern states. The only native species of earwig found in the north is the spine-tailed earwig (Doru aculeatum), found as far north as Canada, where it hides in the leaf axils of emerging plants in southern Ontario wetlands. However, other families can be found in North America, including Forficulidae (Doru and Forficula being found there), Labiidae, Anisolabididae, and Labiduridae. Few earwigs survive winter outdoors in cold climates. They can be found in tight crevices in woodland, fields and gardens. Out of about 1,800 species, about 25 occur in North America, 45 in Europe (including 7 in Britain), and 60 in Australia.

Earwig are hemimetabolous, meaning they undergo incomplete metamorphosis, developing through a series of 4 to 6 molts. The developmental stages between molts are called instars. Earwigs live for about a year from hatching. They start mating in the autumn, and can be found together in the autumn and winter. The male and female will live in a chamber in debris, crevices, or soil 2.5 mm deep. After mating, the sperm may remain in the female for months before the eggs are fertilized. From midwinter to early spring, the male will leave, or be driven out by the female. Afterward the female will begin to lay 20 to 80 pearly white eggs in 2 days. Some earwigs, those parasitic in the suborders Arixeniina and Hemimerina, are viviparous (give birth to live young); they would be fed by a sort of placenta. When first laid, the eggs are white or cream-colored and oval-shaped, but right before hatching they become kidney-shaped and brown. Each egg is approximately 1 mm (0.04 in) tall and 0.8 mm (0.03 in) wide. Earwigs are among the few non-social insect species that show maternal care. The mother will pay close attention to the needs of her eggs, such as warmth and protection, though studies have shown that the mother does not pay attention to the eggs as she collects them. The mother has been shown to pick up wax balls by accident, but they would eventually be rejected as they do not have the proper scent. The mother will also vigorously defend the eggs from predators, not eating unless an egg goes bad. Another distinct maternal care unique to earwigs is that the mother continuously cleans the eggs to protect them from fungi. Studies have found that the urge to clean the eggs persists for days after they are removed; when the eggs were replaced after hatching, the mother continued to clean them for up to 3 months.