Cockroaches have three stages of development — egg, nymph (immature form which closely resembles the adult form only smaller) and adult.

The egg stage in cockroaches is unusual in the insect world. Cockroaches put their eggs into small cases holding anywhere from about six to 40 or more young. Some cockroaches put their egg cases in a protected place soon after it is formed, while others hold it internally or on the end of their body until it is ready to hatch.

When the young break out of the egg case, they are very small nymphs. To grow, all insects must shed their outer skin by a process called molting. When a cockroach molts, it is soft and white until its body hardens and darkens. With each molt, the cockroach grows in size and becomes more adult-like. It may take a cockroach as little as six weeks to become an adult or as long as a few years. This will depend on what kind of cockroach it is and how favorable the conditions are for its growth.

As with most insects, cockroaches will not molt after reaching the adult stage. Adults look similar in shape to nymphs but will often have wings.

It is important to know which kind of cockroach you are trying to control because each kind likes to be in a slightly different location. The cockroach pests that are most difficult to control are usually the smaller kinds, but if the larger ones establish inside, they too can be difficult to eliminate.

Small Cockroaches: The most persistent cockroach pests are the smaller kinds that live and breed indoors with people. This includes the very common German cockroach (Blatella germanica) and the less common brownbanded cockroach (Supella longipalpa).

German Cockroach: German cockroach adults are ½ to ⁵/8 inch long and pale brown or tan with two parallel black streaks behind the head. Unlike most cockroaches, German cockroach females protect their egg cases by carrying them around. The egg case protrudes from the body until the eggs are nearly ready to hatch. Each egg case contains thirty to forty eggs that take about two weeks to hatch. A female German cockroach may produce one to seven cases during her life. German cockroach nymphs are about ¹/8 inch long when they hatch and uniformly dark, except for a lighter brownish area in the middle of the body.

German cockroaches are mainly found in kitchens and bathrooms around sinks and drains, behind refrigerators and stoves, and in cabinets. However, if sanitation is poor, German cockroaches may be found in other places. Even though adult German cockroaches have wings, they do not fly.

Brownbanded Cockroach: Brownbanded cockroach adults are about ⁵/8 inch long. All stages have two light, yellow-brown bands that run across their backs. The bands on adult males may be hard to see since their light brown wings completely cover their narrow bodies. The males can fly in a warm environment.

Brownbanded cockroaches may be found anywhere in a structure, especially above floor level around cabinets and in corners near the ceiling. Egg cases are often glued underneath drawers and in furniture and appliances, including TV’s, microwaves, computers, and radios.

Large Cockroaches: The most common large cockroaches include the American (Periplaneta americana), the smokybrown (P. fuliginosa) and the oriental (Blatta orientalis). These cockroaches are normally found outdoors, but they can live inside.

American cockroach: American cockroach adults range in size from 1½ to 2 inches. Generally, they are red-brown in color, with pale yellow "halolike" markings behind the head. The nymphs are about ¼ inch long when they hatch from the egg case and are initially gray-brown. As they develop, they become more red-brown and the "halo" becomes more prominent.

American cockroaches are often found in dark, moist, warm areas, especially around sewers, storage rooms, and garbage areas. Along the coast they may be found in trees. When inside, they generally stay on the basement and first floor levels. Adults may fly on warm evenings.

Smokybrown cockroach: Smokybrown cockroach adults are 1 to 1½ inches in length and, as the name implies, smoky-brown in color. The young nymphs are about ³/8 inch long, with black bodies and white markings on the middle of their bodies and the tips of their antennae. As they grow, they turn a mahogany color before becoming smoky-brown adults.

Smokybrown cockroaches prefer dark, warm, humid environments. They can be very mobile and will use a variety of habitats such as mulch, log piles, thick vegetation, and gutters around roofs. Along the coast they may be found in trees, especially palmettos. In a structure, they can be found from the attic to the crawl space. Adults may fly on warm evenings.

Oriental cockroach: Oriental cockroach adults are 1 to 1¼ inches in length and dark brown to jet black in color. The wings of the males are ²/3 the length of the body, while the females have only small wing pads. Neither sex is capable of flight. The nymphs are about ¼ inch long when they hatch and go from red-brown to black as they develop.

Oriental cockroaches prefer dark, damp, and relatively cool locations. They can be found in water meter boxes, sewer lines, leaf litter, crawl spaces and basements. In a structure, they rarely go above the basement level.

Many cockroaches do not live in close association with humans. Others are found in only a few locations around the state. These are considered minor pests.

The Surinam cockroach (Pycnoscelus surinamensis) is about 1 inch in length, with a stout body. It is brown to black with a pale band on the front edge of its body. The wings extend beyond the length of the body. Only females are known to occur, and all the young are clones of the mother. Surinam cockroaches are mostly found along the coast, where they can become very numerous in lawns. Sometimes they are transported in plantings used in shopping malls.

Wood cockroaches are a group of minor cockroach pests. They are native to North America. Males are usually plain brown and 1 inch or less in length. Females are shorter and broader than males. Generally, females range in color from light to dark brown, with wings only half the length of the body or shorter. Males are good fliers and are often found around lights at night. Sometimes males fly into buildings. Outdoors, wood cockroaches are found in areas such as wood piles, mulch and leaf litter. Indoors, wood cockroaches cannot survive very well and are seldom a problem.

There are many control strategies available to help solve cockroach problems. Cockroach control requires more than just insecticides. You will be most successful if you use a combination of methods. Preventing access to shelter, food and water around your home is one of the best control measures both outside and inside.

Outdoor habitat changes that may help include:

• Removing as much mulch or debris around the building as possible.
• Pruning tree limbs and shrubbery so they do not touch the house.
• Stacking wood away from the house and raising the piles off the ground.
• If you have pets, not leaving food bowls out overnight and keeping kennel areas clean.
• Disposing of garbage in sealed bags and in garbage cans with lids.
• If you recycle, rinsing out cans and bottles and keeping your recycling areas in a dry location away from the house. Do not let your recycling area become too cluttered.
• Keeping screens and weather stripping in good repair.
• Checking attic vents and windows.
• Caulking large openings around outside drainage lines and sewer vents. Steel wool can be used as a temporary filler until you can caulk openings properly.
• Remembering to check grocery bags, boxes, firewood and other items that may serve as a means of entry for cockroaches.

If cockroaches do get inside, the following tips will help you control them:

• Keep food and garbage in tight containers.
• Clean up all crumbs and spills on floors, counters and shelves as soon as possible.
• Keep faucets and drains under sinks and appliances in good repair. Do not let water stand in the sink for long periods of time.
• Keep clutter from accumulating, especially in kitchens and bathrooms. Cockroaches often hide in messy cabinets and in stacks of newspapers, bags and rags.
• Vacuum often. Vacuuming is very important because it can remove small food crumbs and cockroach egg-cases that may not be killed by insecticides.

Good sanitation is important, both inside and outside the house. It is often the best control measure for cockroaches.

Many products for cockroach control can be found in supermarkets, garden supply stores, feed and seed stores, and farm supply stores. It is impossible to list all the insecticides and products. You can usually find the right chemical in the store by looking at the lists of ingredients on the containers. Look at the label on products at the store to help you select the one that can be safely and legally used on a specific site. Read the entire label and only use insecticides according to label instructions. Most homeowner products come in a dust, bait or spray form.

Dusts are slow-acting, but they give long-lasting control. Boric acid is probably the most commonly used dust labeled for cockroach control. Boric acid should be applied as a thin film in out-of-the-way places such as under refrigerators, stoves and sinks, as well as in wall voids, cracks and crevices. It should not be applied in open areas such as on shelves and counters where food and utensils are kept. Never place in reach of children and pets.

--The Clemson University Cooperative Extension Service