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Common Name: European Earwig
Scientific Name: Forficula auricularia

(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)

Male European earwig - image credit N. Heidenreich, FlickrThe 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
The name “earwig” has a long and extremely non-scientific history. It is derived from the Old English word “earwicga” which translates as “ear wiggler.” There is an ancient myth that these very harmless (to humans, anyway) insects have the ability to crawl up the ear canal of a human and then eat their way into that unfortunate person’s brain. None of this is true, and it is very unclear why anyone would have thought that it was or why this myth would persist over many hundreds or thousands of years! There have been, though, some interesting fictional adaptations of “earwicga” myth in literature and science fiction television shows and movies.

Appearance and Habits
The European earwig is a little over one half an inch long (females are larger than males). They have a dark, red-brown body, a reddish head, yellowish legs, two long antennae, two membranous flight wings (which it seldom uses) tucked under the short, hard, protective forewings, and two very distinctive cerci (“pinchers”) on the end of its abdomen. The shape of the cerci differs in males and females with females having straight cerci and males having curved cerci. These cerci are used to grab and secure prey and also, in males, as weapons in mating competitions.

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.

Mating and Reproduction
European earwigs are solitary organisms and have no social behaviors or communication systems. Males and females meet up once a year, though, in order to mate. Males find females via pheromones that the females excrete in their feces. Males attracted to the pheromone then compete with each other for the attention of the female. It is thought that body size and especially cerci size are the critical variable in a male’s reproductive success. Mating takes place in early autumn.

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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