While their prominent tail-end pincers might look ferocious, earwigs aren’t harmful to people. Earwigs can seriously damage seedling vegetables and chew holes in annual flowers, soft fruit, and corn silks, but earwigs also play a beneficial role by feeding on aphids and other insects. Nocturnal in habit, earwigs feed at night and hide during the day in dark, cool, moist places in the yard or within flowers or vegetables. To manage earwigs, reduce hiding places and moisture, and employ a vigilant trapping program.
Earwigs are among the most readily recognized insect pests in home gardens. Although they can devastate seedling vegetables or annual flowers and often seriously damage maturing soft fruit or corn silks, they also have a beneficial role in the landscape and have been shown to be important predators of aphids. Although several species occur, the most common in California gardens is the European earwig, Forficula auricularia, which was accidentally introduced into North America from Europe in the early 1900s. The striped earwig, Labidura riparia, occurs in southern California and can annoy residents when it is attracted to lights. It has a very disagreeable odor when crushed. However, the striped earwig does not damage plants.
The adult earwig is readily identified by a pair of prominent appendages that resemble forceps at the tail end of its body. Used for defense, the forceps are somewhat curved in the male but straighter in the female. The adult body is about 3/4- inch long and reddish brown. Most species have wings under short, hard wing covers, but they seldom fly. Immature earwigs look like adults except they are smaller and lack wings. Contrary to popular myth and despite their ferocious appearance, earwigs do not attack humans.
Earwigs feed most actively at night and seek out dark, cool, moist places to hide during the day. Common hiding places are under loose clods of soil, boards, dense growth of vines or weeds, or even within fruit damaged by other pests such as snails, birds, or cutworms.
Female earwigs dig cells in the ground where they lay masses of 30 or more eggs. Eggs hatch into small, white nymphs and remain in the cell protected and fed by their mother until their first molt. Later instar nymphs are darker and forage on their own. Generally there is one generation a year, but females produce two broods. Part of the earwig population hibernates during the winter as pairs buried in cells in the soil. In milder California climates, some remain active all year.
European earwigs feed on a variety of dead and living organisms, including insects, mites, and growing shoots of plants. They are voracious feeders on soft-bodied insects such as aphids and insect eggs and can exert significant biological control under some circumstances. In yards that are planted to turf and contain mature ornamental plants, damage by earwigs is unlikely to be of concern.
European earwigs can cause substantial damage to seedling plants and soft fruit as well as to sweet corn. Damaged seedlings may be missing all or parts of their leaves and stem. Leaves on older plants, including fruit trees, have numerous irregular holes or are chewed around the edges. This damage may resemble damage caused by caterpillars. Look for webbing, frass (excrement), or pupae that would indicate the presence of caterpillars. Soft fruit such as apricots or strawberries may be attacked. Hard fruit such as apples will not be harmed. On stone fruit, look for shallow gouges or holes that extend deeply into the fruit. On strawberries, distinguish earwig damage from that of snails and slugs by checking for the slime trails left by snails and slugs. On corn, earwigs feed on silks and prevent pollination, causing poor kernel development. Earwigs may also damage flowers including zinnias, marigolds, and dahlias.
Earwigs may seek refuge indoors when conditions outside are too dry or hot or cold. Large accumulations of earwigs can be annoying but present no health hazards. Sweep or vacuum them up and seal entry points. Earwigs eventually die indoors because there is little for them to eat.