During the last five years, a dark-brown formidable-looking insect with prominent “pincers” at its tail end has caused much consternation in homes and gardens of greater Boston and other areas along the northern Atlantic Coast.
This is the European earwig which has the scientific name Forficula auricularia L. As the name implies, it is a native of Europe, western Asia, and northern Africa. Although it has increased tremendously in many localities, it is not new, having been known since 1907.
In addition to its native home, this insect has been spread to East Africa, East Indies, Tasmania, New Zealand, Australia, and North America. In this country, it is found principally along the coast of New England and the Pacific Coast, where it is very abundant and troublesome.
The climate and typical weather govern the ability of the earwig to thrive and multiply. These insects cannot flourish where the annual rainfall is less than 30” inches (except in irrigated areas), and the mean temperature is less than 75° F. in July and August.
However, they survive a surprising amount of winter cold. The climate of eastern New England is highly favorable to earwigs.
Noted Hitch Hikers
The earwig is a very weak flyer and seldom takes to the air. It crawls and runs rapidly, but only for a short distance. However, it is an accomplished “hitchhiker.” Introductions from abroad have been traced to ship and plane cargo, even to letter mail.
Earwigs are omnivorous, eating both living and dead animal or vegetable matter. They frequent garbage and other filth, but their principal food is mosses, lichens, algae, and fungus spores which thrive in cool, damp places.
Their animal food includes soil-inhabiting insects, mites, spiders, protozoa, and aphids and the inactive stage of several insects that may be found on trees.
Nearly all plants growing in an infested area may be damaged, though often not seriously. Among the flowers, dahlia, carnation and zinnia are most frequently injured. Beets, beans, cabbage, and potato, are damaged, and the foul excreta may contaminate the leafy vegetables from the hiding insects. Unsprayed ripe fruits and berries may also be eaten.
Earwig More Repulsive, Disgusting Than Destructive Pest
The earwig is more of a repulsive, disgusting annoyance than a destructive pest. The habit of hiding during the day in any available shelter or crevice about the home, such as laundry on the line, window awnings, window blinds, garden hose, and door frames, is highly irritating.
However, the often-repeated legend that the earwig enters the ear to tunnel into the head is mythical and unsubstantiated by fact.
The shiny elliptical or oval eggs are pearly white and about 1 millimeter in diameter, swelling to about twice that size before hatching. They are laid in masses of 30 to 90 in cells 2” to 6” inches beneath the surface of rich, mellow soil.
There are four instars, or growth periods, of the earwig nymph developing from about 4 mm. to 11 mm. in length (exclusive of the forceps) in seven to nine weeks. The nymphs resemble the adult except for the wings that first appear just before they become adults.
The average adult is 14 mm. long, brown with two 14 segmented antennae and a pair of short membranous wings folded under horny wing covers. The males are distinguished by their curved forceps at the rear, while the females have a couple of nearly straight forceps. These forceps are used occasionally but not skillfully to fight, capture, and hold prey.
One Generation Of Earwigs a Year
Most male and many female earwigs die during the winter in the east, but on the Pacific Coast, many hibernate successfully. The average life of non-hibernating females and males is about six months; the hibernating females live ten months.
The European earwig develops one generation annually. The young are present from early May to mid00-July when most have become adults. They begin to forage more widely, climb trees and buildings and become more noticeable.
Earwings Natural Enemies
Earwigs have many natural enemies among insects, roundworms, birds, and reptiles. One of the most effective is a parasitic fly with Bigonicheta setipennis. This is a native of Europe, resembling a housefly, which has been introduced in most of the known infested areas in this country.
These flies are attracted to earwigs by odor and soon lay eggs on or near them. Their eggs hatch in about a minute and the tiny larvae enter the body of the earwig, where they feed until they have injured the vital organs and the pest is killed.
A parasitic “threadworm” living in the body cavity of young and adult earwigs has been observed to kill at least ten percent of the pests in certain colonies. Several entomophagous fungi also infect earwigs and are particularly destructive to them in wet weather.
Predatory ground beetles eat earwigs readily but have not been observed in large numbers to provide any reasonable control. Snakes and toads consider earwigs a delicacy, as do poultry, especially bantam chickens. However, the earwigs are so clever at hiding in the daytime that poultry seldom keeps the insects in check.
Are Earwings Easy To Trap
Eat-wigs are easily trapped. A favorite trap is made from two boards ¾” x 4” x 12” inches. Grooved lengthwise, these act as hiding blocks when joined with the grooves inside. However, many escapes and hundreds of earwigs are trapped in such hiding blocks. Also, good traps are short sections of garden hose, inverted flower pots, and similar utensils.
In city or suburban areas around buildings, small flower or vegetable gardens, and shrubbery, poisoned baits have been generally recommended for control with excellent results.
The most satisfactory baits are —
Stale bread crumb – 16 pounds
Paris Green – 1 pound
Water to moisten Or Whet bran – 12 pounds.
Sodium fluosilicate — 1 pound
Fish oil – 1 pint
The bread crumbs or bran and the Paris Green or sodium fluosilicate are thoroughly mixed dry by stirring with a paddle or the hands. The water or fish oil is then added and thoroughly mixed so that the bait is moist and crumbly, not sticky or doughy.
The appeal is most effective in June while the nymphs are active, but before the insects become adults. It is usually spread at about two pounds on every 1,000 square feet or placed in small cans, pop bottles, or boxes where the earwigs congregate. It may be necessary to renew the bait at seven to l0 days intervals.
The poisons in these baits are toxic to humans and warm-blooded animals, so they must be handled and used accordingly. However, careful observations have shown that wild birds, particularly robins, arc detailed avoid the bait, and dead birds are not found in a baited area. Domestic poultry is less alert and maybe poisoned.
Modern insecticides such as DDT and Chlordane kill the earwigs readily and can be used safely and effectively for their control.
In buildings or wherever there is no danger to plant life, the regular household sprays containing 5% DDT or 2% Chlordane are satisfactory.
The spray or dust is best applied in June before the earwigs are fully grown, but they will be partially effective at any time later in the summer. Applications should be made around the foundation of buildings, under shrubbery, on the trunks of trees, in compost piles, or wherever the earwigs congregate.
Two or three treatments may be advisable, especially when the insects migrate. Whether by bait, spray, or dust, the most successful control is on a community basis where all neighbors cooperate.
These insecticides will also control ants and many other destructive insects. The insects are killed when they come in contact with the residues of the insecticides. It is not necessary to hit them directly or poison their food.
44659 by W. D. Whitcomb