There are many kinds of cockroaches, the American and German cockroaches are one of the most common pest problems. These cockroaches are often about the size of your thumbnail, have broad, flattened bodies and relatively small heads. Cockroaches are one of the most common household pests, and can transmit disease and trigger allergic reactions in humans.
Cockroaches are nocturnal insects. They prefer to live and feed in the dark, so a cockroach seen during the day is a sign of infestation. Cockroaches tend to prefer dark, moist places to hide and breed and can be found behind refrigerators, sinks and stoves, as well as under floor drains and inside of motors and major appliances. Because they can flatten their bodies to fit into narrow areas, cockroaches may also be found hiding beneath rubber mats, behind wallpaper and within wall cracks. This makes it particularly difficult to get rid of cockroaches.
Cockroach feces will be visible during an infestation. Small roaches produce feces, which resemble coffee grounds or black pepper, while larger roaches expel cylindrical droppings. The quantity of visible feces is oftentimes a good indicator of the level of infestation.
Some species emit unpleasant smells called pheromones. In the event of serious infestation, a strong, oily or musty odor may be present. The bodies of dead cockroaches can also be found throughout the house. Oval-shaped egg cases are sometimes visible behind furniture and in other hidden locations, such as the spaces between books.