Earwigs: Get past the myth and meet these unique insects

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First, let’s address that familiar warning that earwigs crawl into people’s ears and burrow into their brain to lay eggs. If one has ever entered an ear, it wasn’t intentional. There’s just no truth to the story; we’re safe from earwigs. More importantly, there’s a lot more you should know about them than that grisly myth. They’re interesting insects with oddly folding wings, pincers to admire if you’re a carpenter and, get this — doting mothers!  

Earwigs belong to a small scientific order of about 2,000 species found around the world, excluding Antarctica. 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, during the time of the dinosaurs. Their order is Dermaptera (der-MAP-ter-uh), from the Greek dermatos for skin and pteron for wing, referring to earwigs’ leathery forewings. The name earwig comes from Old English and means “ear insect.”

Physical description 
Earwigs, like all other insects, have three body sections: head, thorax and abdomen.

They typically range in length from about 1/4- to 5/8-inch (6 mm to 18 mm) long. The largest one, the Australian Giant Earwig, Titanolabis colossea, grows to 2.0 inches (50 mm). Earwigs have a long and somewhat flattened body, which allows them to fit into tight spaces.

Earwig, Forficula auricularia. (video: zaphad1 / Flickr; cc by-sa 3.0) 

Head
Earwigs have a large head with two small eyes, two long, thin antennae and mouthparts designed for chewing. The eyes are compound, meaning they’re made up of hundreds of individual photoreceptors* that transmit signals through neurons to the brain, which then interprets them. Their mouthparts include a labrum and labium (upper and lower lips), maxillae (max-SIL-ee; the upper jaw), and mandibles (lower jaws). (You may have noticed that some parts of the earwig head have the same names as a human face, but they’re nothing alike!)

Earwigs also have a brain. It mostly contains clusters of neurons that interpret sensory information coming to it, such as signals from eyes, taste and smell receptors. It doesn’t play a very big role in bodily functions; ganglia throughout the rest of the body primarily handle those. Interestingly, recent research on insect brains show some evidence of a rudimentary consciousness, according to a 2016 paper on the subject.¹  

Thorax
The middle body section, the thorax, has three pairs of legs and two pairs of wings attached to it. The legs are long and adapted for running. The forewings are short, leathery and not used for flight. Instead, they’re modified into covers for the hind wings. The hind wings are large, semi-circular and folded first lengthwise, like a fan, and then crosswise. The hind wings are kept hidden under the forewings, except during rare instances of flying. Earwigs aren’t good fliers and compensate by being fast on their feet. Many are even wingless.

 

olor illustration of two earwigs, a male and a female, showing the hind wings folded and unfolded.

Earwig hind wings, unfolded and folded. (Bugboy52.40 / Wiki; cc by-sa 3.0

Abdomen
Behind the thorax is the abdomen. It contains part of the earwig’s nervous system, digestive system, circulatory system, reproductive system, and the anus. In some species, there are also glands that can shoot an offensive fluid up to 4 inches (100 mm).

Now, to the pincers. We’re describing them last, but they may be what you notice first about earwigs. The pincers (forceps) are located at the end of the abdomen. Technically called cerci (SIR-see), earwigs use them to fold their hind wings, defend themselves against predators attacking from the rear, and capture prey.

Females have relatively straight pincers and they’re large enough to be noticed. But males’ are larger, shaped like calipers and look dangerous. Take that as a warning. If one is handled carelessly, it might use them out of fear. Otherwise, earwigs are harmless to humans. (There are other insect species with cerci, but only earwigs have the heavy, pincer-looking ones.)
Learn more about insect anatomy 

Life cycle
Earwigs undergo incomplete metamorphosis (hemimetaboly), which means they go through three life stages: egg, nymph and adult.

Males and females mate in the fall. They stay together in a nest located about 1-inch (2.5 cm) deep under debris, in crevices or in soil, through the fall and early winter. During mid-winter to early spring the male leaves. The female then lays 50 to 80 eggs. Depending on the species, she has one or two broods each season. The young, called nymphs, hatch in about seven days and make their egg case their first meal.

Earwig nest with the mother and her nymphs and eggs.

Earwig mother in her nest tending to her young nymphs and eggs. (Photo by Tom Oates, 2010/ wiki; cc by-sa 3.0)

Now, here’s a really interesting thing about earwigs: Mother takes care of her babies, a very unusual thing in the world of nonsocial insects. If her eggs get dispersed, the mother rushes to save them and puts them back in the burrow. She keeps them 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 nymphs look somewhat like adults, only smaller, wingless and pale. They 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 amount of time the nymphs stay in the nest varies with the species, but they begin foraging on their own at least by the end of their second molt. They mature to winged, sexually mature adults in around 50 days. By that time, they also have their adult coloration. They live for about a year from the time they hatch.

In an ironic, tragic twist to this story, after taking such tender care of her young, their mother is apt to eat those that won’t leave the nest when she wants them to. 

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 see them around lights or lighted windows.

If you find an earwig, it might be because it found a way into your house. This usually happens by accident, 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 — and don’t get pinched!

¹A compound eye is an organ made up of hundreds, sometimes thousands, of individual photoreceptors. Each photoreceptor, called an ommatidium (oh-muh-TID-ee-um), consists of a lens and cells for distinguishing light and, sometimes, color. Compound eyes create a mosaic which an insect’s brain is able to interpret as one image. Compound eyes are particularly adept at detecting motion. This is one reason it’s hard to sneak up on them.

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²SmithsonianMag.com
*Top photo: Male earwig, Forficula auricularia. (Gilles Gonthier / Flickr; cc by 2.0)

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