In the whole wide world of insects, there’s probably not one bug with a more unfortunate name or history than the earwig. Earwigs derived their name from a popular and very old notion that the wiggly insect liked crawling into people’s ears and establishing a base camp inside the ear where they would raise their young. And as you can imagine, they were much feared and maligned as a result (after all, few people care for the idea of a bug settling down in their ears).
Under normal circumstances, a folktale like that would have died off a long time ago once scientists proved it false. But not so for the poor earwig. Its much-undeserved reputation gained new notoriety in the 1970s, thanks to a popular episode of the TV horror series Night Gallery. In that episode (charmingly but deceptively called “The Caterpillar”), an earwig winds up chewing through the brain of a notorious womanizer and would-be murderer. The good news – the earwig finally emerges from the “other side” of the brain; the bad news – it laid eggs during its journey, and now all those babies have to eat their way out. While the legend was certainly good fodder for TV audiences, fortunately it’s just that – a legend – and earwigs thankfully want nothing to do with either our ears or our brains.
Earwigs comprise the Dermaptera order of insects that includes about 2,000 species divided into 12 families. That may sound like a lot of bugs, but in fact, Dermaptera are one of the smaller orders of insects, many of which include tens of thousands of species. Despite their relatively small family size, earwigs are found in most parts of the world, including North, South and Central America, Asia, Africa, Europe and Australia. They’re also one of the most widely recognized insects, partly because they like to hang out in our backyards and gardens and partly because of their distinctive appearance – most notably, the pair of long pincers that extend from the tail-end of an earwig. These pincers (called cerci) are primarily used to grasp prey, to mate and sometimes to do battle with other earwigs. They probably also contain sensory organs that enable the earwigs to detect movement and sound, and while they may use them to defend themselves from humans, the pincers are too weak to inflict any damage to tough human skin. A couple of species found in Africa and Asia don’t have pincers and live as parasites on bats and rodents. In addition to cerci, earwigs also have a pair of antennae to help it feel and sense its surroundings as well as track down prey. Total body length typically is a little over a half an inch.
In the U.S., there are 22 species of earwigs, nearly all of which have been introduced from other countries. Only a small handful of these 22 species are found commonly in the U.S., mostly in the South and Southwest, and of these, Forficula auricularia (sometimes called the European earwig or the common earwig) is the most common and widespread.
Most earwigs prefer damp, dark locations, usually nestling down under rocks, dense ground-level vegetation or old stumps. Some earwigs bed down inside fallen fruit damaged by birds or small mammals. Far less often, they can be found indoors, usually in the fall when the weather turns cold or after a particularly long dry spell. They cant live long indoors where there’s no ready source of food, so do them a favor and carry them outside to a nearby rock or stump and set them free.
As for their eating habits, for the most part, earwigs are scavengers, looking for relatively easy-to-find sources of food like rotting leaves and plants and other debris during the cool, dark hours from dusk until dawn, at which time, they retreat to cooler environs. They’re also fond of eating some other insects, and yes, they will eat living plants too, including young vegetable plant shoots.
While earwigs’ legendary (i.e., false) brain-eating reputation might be more prevalent (or rampant), their reputation as excellent parents has earned them a unique spot in the insect world. The life of an earwig begins in a clutch of eggs laid by the female, usually in a shallow burrow or cell located beneath a rotting log or other protective shelter. Most broods contain between 30 and 50 eggs, and females usually produce two broods each year, one in the early spring and one later in the year. Mating takes place in the early fall, just before the earwigs dig their winter burrows. The brooding period is longer for the insects born in the early spring when temperatures are cooler, usually taking about 70 days. Once the eggs are laid, they’re closely guarded by the mother who will attack predators and even move the eggs if her shelter is disturbed. Mother earwigs also clean the eggs regularly to protect them from opportunistic fungal infections. (To get a close-up view of earwig “babies” and earwig parents protecting their eggs, check out this YouTube video.)
After hatching, the tiny “newborn” nymphs remain in the burrow under their mother’s care and protection until their first molt, when they shed their outer shells to accommodate their growth. At this point, some earwigs may head out to forage on their own during the night, returning to the nest to hang out during the day. More commonly, earwigs wait until their third or fourth molt to leave the nest and forage completely on their own. By this time, their outer shells (exoskeletons) are much darker, making it easier for them to stay camouflaged. Most earwigs have five molts before reaching full maturity.
Interestingly, more recent research found orphaned earwigs raised in a lab setting could actually do quite well without a mother around, growing larger and stronger than the average “parented” insects. However, they also found the earwigs that lacked a mother’s loving care were far less able to raise broods of their own, which meant subsequent generations were less likely to survive. The “passing down” of parenting strategies from one generation to another is common among mammals, but the earwig study marked the first time a similar effect was observed in the insect world.
Even without the whole eating-through-your brain stigma, plenty of people still dislike earwigs, primarily because they tend to enjoy many of the same foods we do – namely, fresh veggies from the garden. While most of their feeding focuses on debris and other insects, earwigs can and do feed on tiny, succulent plant shoots and seedlings as well as flowers and soft fruits like tomatoes, apricots and berries. They’re also very fond of sweet corn and its silk, sometimes consuming enough silk to interfere with pollination. Less commonly, they may eat leaves of mature plants, leaving holes and irregular edges similar to damage caused by caterpillars.
But before you go on an anti-earwig rampage, know this: Most crop damage is due to other pests like caterpillars, aphids, slugs and cutworms. Earwigs can actually help control damage by consuming most of these other common “pest” insects, especially those with soft bodies. Plus, there are few things an earwig enjoys more than a tasty meal of insect eggs, which makes them a pretty beneficial bug to have around.
OK, so earwigs may not crave the taste of brains like the zombies that populate apocalyptic fiction, but they’re still pretty cool, and beyond their innate knack for parenting, they exhibit some other characteristics worthy of mention:
As with many insects, there’s a lot more to know about earwigs than initially meets the eye. While their rear pincers (not to mention their brain-feasting reputation) may make them seem fearsome, they’re actually mild, retiring insects that do all they can to keep a low profile, usually while ridding your garden and yard of more damaging insects like aphids and slugs. With their unusual maternal behaviors (especially rare among insects that don’t form social colonies like ants), it’s easy to see why they remain such an interesting subject of research for scientists worldwide.