Earwigs

Despite their intimidating appearance, earwigs are harmless to people and, contrary to their eye-catching name, they do not seek to hide inside your ears. However, these insects can cause serious damage to seedlings and chew large holes into specialty crops, flowers, and grain. Earwigs belong to the Order (taxonomic ranking) Dermaptera which derives from Greek origins meaning leather and wings. One could find earwigs during the night or during the day in dark, moist, and cool places such as inside vegetables, weeds, home corners, or mulch. When found in the home, earwigs may emit a foul-smelling yellowish-brown liquid (dimethyl disulfide and dimethyl trisulfide) from their scent glands when disturbed or crushed, this is defense mechanism similar to stink bugs (Halyomorpha halys). Because of their tough bodies, earwigs are frequently confused with several species of beetles (Coleoptera), but what distinguishes them?

Identification: Spot Key Characteristics

Similar to beetles, earwigs have wing coverings made of elytra, which are short, hardened shields that cover the wings. Earwigs rarely fly and thus fold their wings in a complex, origami-like style (up to 20 folds). European earwigs have wings, while ringlegged earwigs remain wingless. The European earwig ranges from ¹/₂ to ³/₄ inch long, with banded legs and a reddish head. The ringlegged earwig ranges from ¹/₂ to ³/₅ inch long and is black-yellowish underneath with legs having white crossbands at the joints. Young earwigs (nymphs) are similar to adults except that the nymphs lack wings and their cerci are short. 

Life Cycle and Habits

So why the pinchers (cerci)? Many insect appear to have "pinchers" at the front of their bodies. These are extended jaws (mandibles) or "horns." So why do earwigs have pinchers extending from the tips of their abdomens? For starters, the pinchers are actually modified cerci (paired tail-like insect appendages). They use these modified cerci to defend themselves and fight each other. When two males cross paths, they will use their cerci to wrestle. The larger their cerci, the better the chance an earwig has of winning a fight with another earwig. However, the shape of the cerci also comes into play—earwigs with asymmetrical cerci often defeat earwigs with symmetrical cerci in these intense insect wrestling matches.

Earwigs have a hemimetabolous (incomplete) life cycle, which means they develop from egg to adult through several nymphal instars (developmental stage of arthropods between molts). The majority of earwigs typically deposit their eggs in underground soil cavities, beneath logs, or beneath stones between late winter and early spring. Typically, 20 to 50 oval, pearly-white or cream-colored eggs are produced. Up to the first molt, the female protects the eggs and young while moving, cleaning, and providing maternal care which is uncommon among arthropods.

A mother creates an opening in the soil's surface for the young nymphs to exit the nest and search for food when springtime conditions are favorable. During the day, the little nymphs frequently go back to their burrow, but eventually they leave the nest. Because they are active at night, earwigs are frequently seen near lights where they prey on other little insects that approach light. Earwigs spend the day hiding behind stones, boards, pavements, and litter in damp, shaded areas. They can run quickly and consume both dead and living mosses, lichens, algae, fungi, insects, spiders, and mites.

Earwigs generally hide during the day in a number of locations including behind loose boards, at the base of trees, in shrubs, in flower pots, in damp mops, and in woodpiles. At night, earwigs become active and wander around, eating a range of foods (from trash to different types of household plants). They can harm lettuce, strawberries, celeries, potatoes, dahlias, zinnias, butterfly bushes, and young beans and beets in the garden. They can also be found feeding on silks in maize ears. During periods of heat and drought, earwigs will enter homes to find shelter. Groups hiding around door and window frames can be unwelcome guests.

Integrated Pest Management

Earwig populations should be reduced outdoors if they are regularly invading a house or building. Reducing mulch layers and landscape structures can aid in eliminating earwig shelters and reduce earwig breeding in soil chambers and spaces beneath landscape stones and timbers. Use plants that are less vulnerable to aphid and scale infestations, or treat these insects when they are discovered, since European earwigs thrive by consuming soft-bodied insects.

Earwigs occasionally move indoors in search of a cool, damp habitat during hot, dry weather. Residual insecticide applications in nooks and crannies, under cabinets, along baseboards, along door and window sills, and in other hiding spots can repel or kill invaders.

• Cultural Practices: Since earwigs are mostly outdoor insects, removing their hiding and breeding locations, such as leaves and debris near homes, helps deter their populations. Ensure that windows and doors on the ground level and basement fit snugly to reduce invasion. Using dehumidifiers in a damp basement may discourage earwigs from entering.
• Trapping: Earwigs can be encouraged to cluster in trapping sites. Place cover (pieces of canvas, boards, heavy paper or other cover material) on top of mulch, or around shrubbery where earwigs are present. Earwigs will hide under these sheltered areas, allowing them to be collected early in the morning. Shake the earwigs into hot, boiling water or into soapy water. Indoors, remove earwigs with a broom and dustpan or by vacuum sweeper, but be sure to dispose of the vacuum sweeper bag to avoid having the earwigs crawl back out.
• Chemical Control: Insecticide may be needed to eliminate large populations. Outdoors, apply pesticides to areas around the foundation of the house where earwigs are seen. Treat the entire infested area except where indicated in the precautions stated on the pesticide label. Apply in spring when young earwigs are leaving their nests and again in midsummer if earwigs are troublesome. Many insecticides are labeled for earwig control. Indoor treatments should supplement outdoor treatments since earwigs do not become established indoors.

Reminder! Before using any pesticide, always read the label. By law, all pesticides must be used following the instructions on the label.

Originally written by David J. Shetlar and Jennifer E. Andon, Entomology, Ohio State University Extension, March 9, 2010.