More About Roaches
Additional Information
Cockroaches are one of the most common insects on Earth and have been present for nearly 350 million years according to fossil evidence. Insects are considered by some biologists to be one of the most successful groups of animals to ever inhabit this planet, and cockroaches are among the most adaptable and successful insect groups. They have survived many changing environments over millions of years. There are approximately 3,500 species of cockroaches worldwide, with about 70 species found in the United States.
Their presence in nearly every part of the world and in a wide range of habitats demonstrates their outstanding success in nature. However, their biological characteristics that make them so successful can also make them difficult pests to control.
The German cockroach (Blattella germanica L.) is one of the most commonly encountered household insect pests in much of the United States and many other areas worldwide. Fortunately, effective control technology and pest management understanding are now available to allow consistently high levels of cockroach control for most species and in most situations.
Only a few cockroach species found in the United States routinely enter and infest our dwellings. The most common of these are the German, American, oriental, brownbanded, smokybrown, Australian, brown, woods, field and Asian species. Of these species, the first five probably represent 95 percent or more of all cockroach management concerns in and around buildings.
Cockroaches are often found in groups in their daytime hiding or resting areas, called harborages. They can also be found feeding in groups at night. However, unlike ants or termites, they are not social insects. Cockroaches generally forage individually for food and behave in a largely individualistic or non-social manner. Although they are not social insects, they do often form aggregates.
Cockroaches have an oval and flat-bodied shape that enables them to squeeze into all types of cracks and crevices. German cockroaches are most commonly found in kitchens, other areas of food storage or consumption, and bathrooms. They have a shield-like covering called a pronotum that projects forward over the head and their mouthparts are of the chewing type and are oriented downward and slightly toward the rear of the body. With their long, spiny legs, they can run rapidly over most surfaces and specialized pads on their tarsi allow them to easily scale glass windows or walk across a ceiling.
Besides their ability to move around inside and outside, some species are good fliers and cockroaches are well known for moving to new areas via “hitchhiking.” Because they prefer to hide in cracks and crevices during the daytime, they are frequently moved about by people or in products shipped around cities or across the country. Careful inspection of furniture, clothing or other goods coming into a home or other structure may reveal cockroaches hiding in these items.
Cockroaches develop by a gradual metamorphosis that consists of three stages: egg, nymph and adult. The female produces an egg capsule called an ootheca which has two rows of eggs in it. Nymphs hatch out of the egg capsule by working together to break a seam along the top of the egg case. When the seam splits open, the tiny nymphs emerge to begin their life. Cockroach nymphs generally resemble adults in appearance and behavior but are smaller and do not have wings.
Cockroach nymphs undergo a series of molts and with the last molt, the wings (if they exist in that species) are fully formed and the sexes are easily distinguished. The wings of adults may be long and functional or short to almost non-existent. In some species, males are winged but females have only small wing pads. Adults may or may not fly depending on the species and environmental factors.
The length of time required for cockroach eggs to hatch, for nymphs to develop and for the lifespan of adults will vary within each species due to temperature, humidity, diet and other environmental conditions.