European Earwigs

Description

The European earwig is an insect migrant from Europe that was established in the eastern United States around 1907. This insect rapidly spread across the United States and has occurred in Colorado since the 1950s. 

The European earwig is about 5/8 inch long and brown with a reddish head. Young earwigs are similar in appearance to adults but smaller and lacking fully developed wings. A distinctive feature is the pair of prominent forceps at the rear of the body (cerci). The name earwig originates from the superstition that these insects use their cerci to burrow into people’s ears. The male’s cerci are more strongly curved than those of the female. These cerci are used by males to fight with rival males or other insects. In lab experiments, males with more asymmetric cerci have been shown to have an advantage over less asymmetric males. 

The European earwig is the only earwig found throughout most of Colorado. In the extreme southern areas of the state, a second species may be seen: the ring-legged earwig, readily identified by a band on the forelegs. 

Habits

Earwigs are a common nuisance both indoors and out. During the day they hide in almost any dark, confined space, particularly if it also is rather moist. Typical indoor hiding places are under rugs or potted plants, in stacks of newspapers, and similar locations. 

Outdoors, they are commonly found under rocks or stacked wood, inside the unfurled leaves of plants, in eartips of sweet corn, and under various kinds of debris. Problems with earwigs in Colorado tend to occur from mid-July through mid-September. 

Earwigs are active at night and feed on a wide variety of materials. They occasionally cause injury to leafy plants, such as lettuce and some flower blossoms. They are often associated with injuries caused by other insects. For example, leaves curled by aphids and holes in fruit are favorite hiding places for earwigs. 

Earwigs mainly are a nuisance pest. Their reputation is made worse by the widespread fear that many people have regarding these insects. Several tales exist concerning alleged damage of earwigs: how they like to crawl into ears or how the forceps cause a painful pinch. These stories have little basis in fact, although earwigs have been known to cause a mildly painful bite when sat upon or handled. 

Overall, earwigs may actually be considered beneficial — they feed on many plant pests, such as aphids, mites, and insect eggs. Earwigs have been used for biological control of some plant pests. However, there are situations where control of earwigs is desired. 

Earwig Control 

Managing earwigs is best achieved by combining several measures. 

If earwigs are a problem in the home, focus on preventing their entry. These entry points are usually small gaps along doors, windows, and vents. Small gaps can be sealed with caulk.  

Many earwigs can be trapped which may help reduce numbers. Traps can be of various designs but should produce dark hiding areas that the earwigs will seek out for daytime shelters. Rolled corrugated cardboard can be very effective, as can rolled or crumpled newspapers. Furthermore, the addition of some food bait within the shelter can greatly improve the use of a trap by earwigs. Wheat bran and wheat germ are among the baits that have been effective in CSU trials. Such traps should be collected every 2-3 days, bagged and the captured earwigs discarded. 

Certain oil-based baits are also effective traps. Vegetable oil or fish oil placed in a small cup sunk into the ground will be visited by earwigs. Keep the level of the oil at least an inch below the surface, forcing the earwigs to crawl deeply into the cup. Many earwigs may be attracted into oil-baited cups and drown. 

Modifications of the area around the home also may reduce nuisance migrations into the home. Clear the area next to the home of sheltering debris (including mulches) used by earwigs, particularly near likely points of entry (doorways, window wells). This may be particularly effective if the area is also relatively dry, denying moist shelters sought by earwigs. All cracks around doors and windows should also be sealed to prevent entry. Insecticides applied as barrier treatments to exterior near points-of-entry may supplement the effectiveness of these measures.

Table 1. Insecticides recommended to control earwigs outdoors. 

Insecticide	Trade Names
bifenthrin	Ortho Home Defense Max, Ortho Ortho-Klor, K-Gro Home Pest Control, Ortho Max Lawn & Garden Insect Killer, others
carbaryl	Sevin, many baits
deltamethrin	Hi-Yield Turf Ranger, Bonide Termite & Carpenter Ant Dust, Green Light Many Purpose Dust, others
lambda-cyhalothrin	Spectracide Triazide Soil & Turf Insect Killer, Ortho Bug Stop Home Insect Killer, others
permethrin	Ace Soil and Turf Insecticide, Bonide Eight, ferti-lome Indoor/Outdoor Multipurpose, Hi-Yield Indoor/Outdoor Broad Use Insecticide, Ortho Bug-B-Gon Max Garden Insect Dust, many others

Insecticides can be applied in a variety of ways, depending on the situation. Several insecticides (Table 1) may be used as sprays, applied around flower gardens, building foundations, or harborage areas where earwigs hide during the day. Some of these (e.g., Sevin, permethrin) have label use instructions that also allow some uses around fruit and vegetables. Applications made later in the day may be most effective since earwigs are active at night. 

Bait formulations containing carbaryl (Sevin) as the active ingredient are also effective. These are broadcast around the base of plants and are eaten by the insects. Relative to sprays, bait formulations are generally considered to have fewer effects on non-target organisms. 

Spot treatments may be more appropriate for certain situations. For example, earwigs may be controlled on fruit trees by treating the area around the base of the tree, killing earwigs that crawl across this barrier. 

Reference: CSU Fact Sheet 5.533