All about earwigs

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An old European superstition warns that earwigs crawl into people’s ears and burrow into their brains to lay eggs. When you take a look at an earwig, you could almost believe it — just look at those large, forceps-like pincers at the end of their abdomen. There’s no truth to the story, of course, but it gave rise to their name, and those pincers can certainly give a pinch. The name earwig is from Old English and literally means “ear insect.”

Their order is Dermaptera (der-MAP-ter-uh), from the Greek dermatos for skin and pteron for wing, referring to earwigs’ leathery forewings. This is a small order with about 1,800 species around the world, except polar regions. They’re most common in the tropics. About 23 species inhabit the U.S. Fossil records indicate the earwig first showed up about 208 million years ago.

Physical description
What you’ll notice first about earwigs are the large pincers, also called forceps, located at the end of their abdomen. Technically these are “cerci” (SIR-see), and earwigs use them to fold their hind wings. They also use them as a defense against predators who attack from the rear and to capture prey. There are other insect orders with cerci, but only earwigs have heavy, pincer-looking ones. Females have relatively straight pincers; males have scarier-looking ones, shaped like calipers. If we handle earwigs carelessly, they might pinch us out of fear (and some even emit an offensive odor), but these insects are otherwise harmless.

Earwigs typically range in length from about 1/4- to 5/8-inch, but some are as large as 1-3/8 inches. Their body is elongate and somewhat flattened. The head is large, with relatively small eyes, chewing mouthparts and long, thin antennae. Their forewings are modified into wing covers, called elytra (EL-uh-truh), and have a leathery look. Their hind wings are large, semi-circular and folded first lengthwise, like a fan, and then crosswise. They’re hidden under the elytra except during rare instances of flying. They aren’t good fliers and compensate by being fast on their feet. Many are even wingless. Earwigs’ wing coloration ranges from light reddish-brown to brown to black and they sometimes have a yellow pattern.

Food sources
Earwigs are omnivorous. Most species feed on plant material — fungi, algae, mosses, pollen, flowers — or are scavengers on dead and dying vegetation. Some occasionally prey on small insects like aphids and mites. Earwigs cause minimal damage to plants and may even be beneficial as recyclers of decaying material and as predators.

Where to find them
Unless you go looking for them, you may never notice an earwig. They’re nocturnal and hide out during the day. They like dark, moist places, so look for them under stones, boards, mulch, dead leaves, logs and flowerpots. You might also find them in rotting wood where some feed on the decomposing plant material. At night you may find them around lights or lighted windows.

If you do see an earwig, it’s likely because he found a way inside your house. This usually happens by accident, riding in as hitchhikers on cut flowers or other items brought indoors. Sometimes they migrate indoors in large numbers, becoming pests during prolonged heat and drought as they seek moisture and a cooler environment. They aren’t destructive, but because they do need to eat, your houseplants and food items will be on their menu. To eliminate them, just carefully sweep or pick them up and put them outside. Be careful not to crush them as it releases an obnoxious odor.

Life cycle
Earwigs undergo incomplete metamorphosis, which involves three life stages: egg, nymph and adult. (You can read more about the life cycle of insects here.) Females, sometimes assisted by males, dig burrows underground and lay 20 to 50 eggs. The young, called nymphs, hatch in about seven days and make the egg case their first meal.

Now, here’s a really interesting thing about earwigs: Mother takes care of her babies, an unusual thing in the insect world. If her eggs get dispersed, the mother rushes to save them and puts them back in the burrow.

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Female earwig (© Igor Semenov / iStock)

She keeps the eggs free of parasites and fungi by licking them clean. After they hatch, she delivers food to her offspring until they can take care of themselves. The amount of time the nymphs stay in the nest varies with the species, but Mom kicks them out or they begin foraging on their own at least by the end of their second molt.

In a tragic twist to this story, after taking such tender care of her young, she’s apt to eat those who won’t leave the nest when she tells them to scram. Females, depending on the species, lay one or two broods each season.

The nymphs look somewhat like adults, only smaller and wingless. Nymphs shed their outer skin four or five times as they eat and grow larger, a process called molting. With each molt, the wings get bigger and the antennae longer. The nymphs mature to winged, sexually mature adults in around 50 days. By this time, they also have their adult coloration. Earwigs overwinter as eggs or adults in the soil, sometimes as a male and female couple. They live for about a year.

*Top photo: Male earwig, Forficula auricularia. (Gilles Gonthier / Flickr; cc by 2.0)

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