It’s earwig time again in the Midwest

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Earwigs have the unsavory reputation of crawling into one’s ear during the night and eventually boring into the brain. This superstition originated in Europe and made its way to this country hundreds of years ago. It is completely without foundation, and I guess it was started eons ago when someone awoke during the night and discovered an earwig that had lost its way and was gallivanting about his head. These insects may become a nuisance at times, but they are completely harmless.

Earwigs may cause alarms to homeowners at this time of the year because they will attempt to invade the dwelling to escape the cold of winter. They are odd-looking insects and vary in color from light red-brown to black, being about an inch in length when mature. However, the most distinguishing feature about them is the long pair of forcep-like pincers protruding from their rear end. Bug experts have debated for years the function of these appendages, but have come to no definite conclusions. The pincers, which occur in both the male and female earwigs, are probably associated in some way with the mating process, defense, prey capture, and to probe narrow crevices. Muscles attacked to the pincers are quite strong, and if you should pick one up, it is capable of giving you a slight nip. The forceps of the female are straight, whereas those of the males are larger and bowed, caliper-like. It is difficult for one to understand how the forces of evolution combined to create the formidable pincers of earwigs.

The most objectionable thing about them when they invade our homes is that they frequently emit a yellowish liquid that smells to high heaven. They spray this fluid an inch or so to discourge a potential predator. This odor can be quite obnoxious when a basement is inhabited by a large number of these insects.

Earwigs have chewing-type mouthparts and are mainly vegetarians, but a few are predaceous and feed on small insects such as aphids. When present in large numbers, they may cause considerable damage to ornamental and garden plants. They especially like to set up housekeeping in greenhouses during the winter as the humidity, temperature, and ready food supply is to their liking. They are mainly active at night and are seldom seen during the day. If they cannot find a way into your home, they may seek shelter from the cold underground. Light attracts them, and, if for some reason, a person wants to collect them, he should inspect the area around an outside incandescent light.

Some earwigs have rudimentary, short, stubby wings, and some are wingless. The winged forms seldom fly but rely on their speedy legs to move about, though they cannot crawl long distances but often hitch a ride indoors in laundry baskets, cut flowers, newspapers, and baskets of fruit.

During the spring or autumn, the female lays from 20 to 50 pearly white eggs in a chamber she has prepared 2 or 3 inches under the surface of the soil. Few insects show maternal instincts, but the mother earwig is a devoted parent. While the eggs are incubating in the nest, the female earwig sits on them in a manner similar to a mother hen. When the young earwigs hatch, the mother keeps them close to her until after their first molt. Earwigs overwinter in either the adult or egg stage, and some mature ones may burrow into the ground for up to 6 feet to escape the cold.

The best way to keep earwigs out of your home is prevention. All openings to the dwelling should be sealed, and moist mulch should be kept from direct contact with the foundation. Various chemicals may be used for control inside or outside, but many general insecticides on the market give erratic control. It is best to ask your extension or county agent what is the most efficacious insecticidal formulation presently on the market. Earwigs may be trapped easily if you don’t want to use chemicals. A closed, cardboard box with pencil-sized holes punched in near the bottom and baited with oatmeal will trap a surprising number of these pests.

The insect order Dermaptera (skin wings) is a small but diverse order in the vast insect kingdom, and they occupy an ecological niche in the complex web of life on earth.

Dr. Robert Hedeen is a former resident of Maryland’s eastern shore and resided in the Chicago area from 1960 to 1971. He is a retired professor emeritus of biological sciences in the University of Maryland system. He has published more than 30 scientific papers, has written numerous magazine articles, and is the author of two books on the natural history of the Chesapeake Bay.

From the Jan. 3-9, 2007, issue

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