Bug Category: Occasional Invaders

Centipede

Summary

Centipedes and millipedes are not insects because they have more than six legs, but they are closely related invertebrates. When outdoors, these invertebrates are innocuous organisms, but they may be considered centipede pests when they share living space with us. Both of these groups of invertebrates have long, segmented bodies with either one pair (centipedes) or two pairs (millipedes) of legs on each segment. Their food preferences vary greatly.

Habitats

The house centipede is found throughout the United States. This centipede can be found outside under stones, boards, or sticks or beneath moist leaf litter and other organic matter. When disturbed, centipedes move swiftly toward darkened hiding places. When they are found in homes, they are often found in moist basements, damp closets and in bathrooms. Centipedes require moist habitats. If they are plentiful, there may be an underlying moisture problem that should be corrected.

Threats

Some species of centipede can be hazardous to humans because of their bite. Although a bite to an adult human is usually very painful and may cause severe swelling, chills, fever, and weakness, it is unlikely to be fatal. Bites can be dangerous to small children and those with allergies to bee stings. The bite of larger centipedes can induce anaphylactic shock in such people. Smaller centipedes usually do not puncture human skin.

Earwig

Summary

Earwigs make up the insect order Dermaptera, found throughout the Americas, Eurasia, Australia and New Zealand. With 1,800 species in 12 families, they are one of the smaller insect orders. Earwigs have characteristic cerci, a pair of forceps pincers on their abdomen, and membranous wings folded underneath short forewings, hence the scientific order name, “skin wings.” Some groups are tiny parasites on mammals and lack the typical pincers. Earwigs rarely use their flying ability.

Earwigs are nocturnal; they often hide in small, moist crevices during the day, and are active at night, feeding on a wide variety of insects and plants. Damage to foliage, flowers, and various crops is commonly blamed on earwigs, especially the common earwig Forficula auricularia.

Earwigs have five molts in the year before they become adults. Many earwig species display maternal care, which is uncommon among insects. Female earwigs may care for their eggs, and even after they have hatched as nymphs will continue to watch over offspring until their second molt. As the nymphs molt, sexual dimorphism such as differences in pincer shapes begins to show.

Etymology

The scientific name for the order, Dermaptera, is Greek in origin, stemming from the words dermatos, meaning skin, and pteron, wing. It was coined by Charles De Geer in 1773. The common term, earwig, is derived from the Old English ēare, which means “ear”, and wicga, which means “insect”. The name may be related to the old wives’ tale that earwigs burrowed into the brains of humans through the ear and laid their eggs there. Earwigs are predisposed to hiding in warm humid crevices and may indeed occasionally crawl into the human ear canal (much like any other small organism).

The common earwig was introduced into North America in 1907 from Europe, but tend to be more common in the Southern and Southwestern states.

Field Cricket

Summary

Field crickets hatch in spring, and the young crickets (called nymphs) eat and grow rapidly. They shed their skin (molt) eight or more times before they become adults. They eat a broad range of feeds: seeds, plants, or insects (dead or alive). They are known to feed on grasshopper eggs, pupae of Lepidoptera (moths and butterflies) and Diptera (flies). Occasionally they may rob spiders of their prey. They will also practice cannibalism if they are very hungry.

Acheta domesticus (the house cricket) and Gryllus bimaculatus are sometimes raised in captivity for use as live food for exotic pets. Ironically, one of the ways to produce the most nutritious crickets is to feed them dry pet food.

Identification

Field crickets normally range between 15mm and 25mm in size, depending on the species, and can be black, red or brown in color. While both males and females have very similar basic body plans, each has its own distinguishing feature(s).

Females can be indentified by the presence of an ovipositor, a spike-like appendage, about 3/4 of an inch long, on the hind end of the abdomen between two cerci. This ovipositor allows the female to bury her fertilized eggs into the ground for protection and development. In some female field crickets, species can be distinguished by comparing the length of the ovipositor to the length of the body (i.e.G. rubens has a longer ovipositor than G.texensis).

Males are distinguished from females by the absence of an ovipositor. At the end of the abdomen there are simply two cerci. Unlike females, however, males are able to produce sounds or chirps. Thus, males can be identified through sound while females cannot.

Behavior

In mid to late summer, males begin chirping. The acoustical properties of their calling song provide an indication of past and present health. Females evaluate each song and move towards the one they prefer. When the male senses a female is near, he will produce a softer courting song. After mating, the female will search for a place to lay her eggs, preferably in warm, damp soil.

Field crickets prefer to live outdoors, but will move inside when environmental conditions become unfavorable. Their method of entry into buildings include open doors and windows as well as cracks in poorly fitted windows, foundations, or siding.

Unlike house crickets, which can adapt themselves to indoor conditions, the field cricket will die by early winter. Consequently, field crickets in temperate regions exhibit diapause.

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