They are among the most common insects. Based on fossil evidence, roaches are known to have been present on Earth for over 300 million years. Their sizes vary considerably; some species are up to several inches long. Some biologists consider insects to be one of the most successful groups of animals to ever inhabit this planet, and cockroaches are one of the most adaptable and successful insect groups. They have been able to survive many changing environments over millions of years. There are approximately 3500 species of cockroaches.
They are mostly active at night, during which time they forage for food, water and mates. They may be seen in the daytime, particularly when a heavy population is present or when some other form of stress is placed on the population (such as lack of food or water). Cockroaches ordinarily prefer a moist environment, and many species also prefer a relatively high degree of warmth. Cockroaches usually choose to live in protected cracks and crevices which provide a warm and humid environment. Some species, such as the American and oriental cockroaches, gather in large groups on open walls in protected places or in open areas outside. While they are often found in groups in their daytime hiding or resting areas (called "harborage"), and can be found feeding in groups at night, cockroaches are not social insects as are the ants and wasps.

German cockroach

• First, the German cockroach has a larger number of eggs per capsule than the other species that infest structures.
• Second, it also has the shortest period to develop from hatching until sexual maturity; thus, populations of German cockroaches will build up faster than other species. These factors combine to produce what entomologists call a "high reproductive potential." 
• Third, German cockroach nymphs have a better chance of surviving than do other species because the female carries the egg capsule during the entire time that the embryos are developing within the eggs. This results in the nymphs avoiding many hazards of the environment which may affect eggs that remain detached and isolated. Thus, more nymphs are likely to hatch, and a higher reproductive potential is likely.
• Fourth, German cockroach nymphs are smaller than most other cockroaches; thus, they are able to conceal themselves.

American cockroach

It is the largest of the common species, growing to 1.5 inches or more in length. It is reddish-brown, with a pale brown or yellow border on the upper surface of the pronotum. Both the male and female are fully winged. The wings of the male extend slightly beyond the tip of the abdomen, while those of the female are about the same length as the abdomen. When indoors, the nymphs and adults are usually found in dark, moist areas of basements and crawl spaces as well as in and around bathtubs, clothes hampers, floor drains, pipe chases and sewers. In basements they are usually found in corner areas high on the walls. It can also be restricted primarily to large institutional buildings. The American cockroach is also common around the manholes of sewers, and on the underside of metal covers of large sump pumps in boiler rooms.

American cockroaches feed on a variety of foods, but decaying organic matter seems to be preferred. They also feed upon book bindings, manuscripts, clothing and glossy paper with starch sizing. Syrup and other sweets are also attractive. The adults can survive two or three months without food, but only about a month without water.

Oriental cockroach

Total length of this cockroach is about 1.25inches for the female and 1 inch for the male. The female has small, functionless rudimentary wings called wing pads. The male's wings cover about 3/4 of the abdomen. Neither the male nor the female can fly. Adults are very dark brown or nearly black, and usually have a somewhat greasy sheen to their body. Females are broader and heavier looking than males.

An egg capsule is earned by the female for about 30 hours, after which it is either dropped or attached to a protected surface near a food supply. The nymphs and adults have similar habits and are found associated with decaying organic matter indoors and out. They can be found in yards, beneath leaves, in dumps, in crawl spaces and in the mulch of flower beds. They are also common in high moisture situations such as sewers, drains and dark, damp basements. Both the nymphs and adults are sluggish and are usually located at or below ground level indoors. They are seldom found on walls, in high cupboards or in the upper floors of buildings.

Oriental cockroaches feed on all kinds of filth, rubbish and other decaying organic matter. They seem especially fond of garbage and the contents of discarded tin cans. If water is available, they can live for a month without food, but die within two weeks without water.

Brown Banded cockroach

One of the smaller cockroaches, rarely being more than 1/2 inch long. It is light brown and can be readily distinguished from the German cockroach by the presence of two lighter, transverse bands running from one side to the other across the base of the wings and abdomen in adults, and in the same position on the nymphs. These bands may be somewhat irregular or broken and are more apparent on the young and the females than on the males.

Nymphs and adults are generally found on ceilings, high on walls, behind picture frames and light fixtures, or near motors of refrigerators and other appliances. They are also found in light switches, closets and furniture. They do not require as close an association with moisture sources as the German cockroach. This helps explain why they are so commonly found in rooms other than the kitchen or bathroom. These cockroaches dislike light and are not normally seen during the day.

The brown-banded cockroach prefers feeding on starchy materials. However, they can be found feeding on almost anything, and have been known to chew on such non-food materials as nylon stockings (presumably for the residues of body oils and skin flakes).
When making an inspection for brown-banded cockroaches, look beneath tables and chairs, dressers and chests. Look also behind pictures, along picture moldings, on rough plaster walls and ceilings, and most especially on the ceilings and upper walls of cabinets, pantries and closets.
Generally all cockroaches are loathsome pests, spreading filth and running over food, fabric and book bindings. They also mechanically transmit pathogenic bacteria including those of diarrhea. We hold a range of control methods which combine several chemicals. We are also capable of reducing their populations by sterilizing them so that they cannot reproduce.