European Earwig, Forficula auricularia
June 29, 2010
European Earwigs, as the name suggests, are an invasive species native to Europe. They were introduced to the west coast in around 1910, likely in plant material cargo or on the ships themselves. Since then they have spread across many parts of the United States. There are now 22 species of earwigs in the US, 12 of them invasive.
Earwigs’ unusual morphology has put them in an order all to themselves. European earwigs are generally around 12-15 mm long, and have two sets of “wings”. The harder, upper set of wing covers conceals the lower, flying set. When the lower set is expanded they are transparent and almost round in appearance, with veins all branching out from a single point. Earwigs can fly, but only short distances, and very rarely. The head of the European earwig is reddish-brown, while the legs and wing covers are a dull yellow. Variations in colors occur not infrequently. The most distinguishing feature of this species—and, indeed, any earwig—is its cerci, the “forceps” on the rear of its abdomen. In males, these appendages can range from half the length of the abdomen more than twice that big. In general, male cerci are larger and more rounded, or pincer-like, than females. The cerci are harmless to humans, although earwigs use them occasionally to assist in mating or catch prey.
Earwigs mate in the late summer or early fall, and both the males and females burrow underground for the winter. They remain there together until the male leaves in the early spring, after which the female lays her eggs. She lays her first clutch of around 35-50 eggs, and guards them carefully. Female earwigs exhibit a remarkable amount of parental care, tending and grooming the eggs, and will even collect them if scattered or move them to a more favorable spot. The eggs hatch in about 70 days. During their first instar (developmental stage, marked by a moult), the mother keeps them below ground. In the second instar, she lets them aboveground to forage, but they return to the nest at night (though not always the correct one). In the third and fourth instars, the young stay above ground to forage on the surface. By this time, it is late summer, so as soon as the young are mature, they begin to search for mates. The female, in the meantime, has laid a second clutch of eggs which mature much faster (in around 20 days) because of the warmer weather.
Earwigs are omnivorous and tend to eat plant material, other insects, or even garbage. Although they can occasionally consume crops, they are not a significant threat to agriculture, and indeed sometimes consume more harmful insects, like aphids. They shelter in any small spaces; including plants, cover objects, and buildings. They are regarded as a minor pest in some areas.
These specimens were collected as inside the milkweed head also here, on the dam by the pond.
Article by Hazel Galloway