Common Name: European Earwig
(Information for this species page was gathered in part my Ms. Lacie Knapp for her Biology 220W class at Penn State New Kensington in Spring 2011)
The European earwig (Forficula auricularia) is a native, insect species of Europe, Northern Africa and Western Asia that has been accidently introduced to North America, New Zealand, Australia and a number of other temperate and tropical countries around the world. Its first recorded appearance in the United States was in Seattle, Washington in 1907. It was likely brought to this country in a shipment of flowers, fruit, or vegetables, but given the earwig’s ability to find survival spaces in almost any type of biological or human-made materials, it might have arrived in almost any type of transported product. In the hundred years since it arrived in the United States, the European earwig has found its way to almost every region and every state in the country.
Image credit: N. Heidenreich, Flickr
There are twenty-two species of earwigs in the United States. Twelve of these species (like the European earwig) are alien exotics, and ten are endemic. Only four of these twenty-two species, though, are classified as pest (or potential pest) species. Most of the earwig species in the United States actually are quite beneficial acting as shredders and comminuters in the soil decomposer community and as biological control agents (predators) for a variety of insect pests. The European earwig is classified as a pest species, but it is also acknowledged that it can also be an active predator of crop damaging aphids, caterpillars, beetles, and midges. Its role as a pest controlling agent is especially important in organic orchards and farms. In Pennsylvania, the European earwig is the most commonly found “pest” earwig species.
Derivation of 'earwig' Name
Appearance and Habits
European earwigs are nocturnal and spend the day in dark, moist places (like spaces under rocks, logs, surface vegetation, flower pots, leaf litter etc.). One frequently mentioned method of bio-control of earwigs is to make sure that your property is free of these potential daylight refuges. Earwigs are omnivorous and will consume plant materials (both living and dead), aphids, spiders, insects, and insect eggs. They will consume garden plants and a wide variety of fruit and vegetable crops but, very interestingly, seem to do so when potential prey (like aphids) are not present in sufficient numbers. European earwigs also accumulate inside human habitations and can work their way into almost any open space or crevice. They can consume stored food products (flour, bread, cereal, crackers, etc.) and befoul clothes, books, laundry and more with their odiferous secretions.
The female then digs out a brood nest and lays her clutch of thirty to fifty eggs. This nest will also serve as the hibernation nest for the female and also for the male. The female will tend to the eggs stacking them up and then spreading them out making sure that fungi do not grow on them and protecting them from possible predators. The eggs will hatch in the spring and the first nymphs that emerge (the first “instar”) will remain in the nest and continue to be cared for by the female. The female guards and feeds the nymphs (via regurgitated plant materials) throughout the first instar stage (which is about the first month of life). This level of maternal involvement with offspring is very unusual in insects!
There are four nymphal stages in earwigs. In the second instar stage the female opens up the nest and the nymphs begin to go out at night to search for food. These second instars, though, tend to (or at least try to) return to the nest during the day. By the third instar stage, though, the nymphs have completely left the nest and move freely about the soil and litter habitat searching for food by night and seek out their own daylight refuges by day. These nymphs develop into adults in the late summer or early fall and then mating occurs and the cycle begins all over again.
Some female earwigs lay a second clutch of eggs after the second instar nymphs have left the nest. This second batch of eggs hatches and marches through the four nymphal stages very rapidly in the warm temperatures of summer and matures into adult earwigs at the same time as the overwintering clutch of eggs.
Earwigs are preyed upon by many species of birds (including chickadees and nuthatches) and are also eaten by a number of amphibians (especially toads). They are also parasitized by the parasitoid fly Bigonicheta spinopennis and susceptible to numerous bacterial and fungal infections.
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This page was last updated on
August 31, 2014