The Oriental cockroach known as the "water bug," is more closely associated with damp areas than the other common roaches. These insects feed on garbage and decaying organic matter and are often considered the filthiest of the house-infesting roaches. They are found in damp basements, cellars, crawl spaces, near drains, leaky water pipes and beneath refrigerators, sinks and washing machines, under floors, and inside walls. They forage mostly on the ground floors of buildings.

Outdoors, they are found beneath decomposing leaves or stones in mulching materials, in trash and at municipal sewer plants. During the autumn, there can be a mass movement into buildings, but because of their preference for cooler temperatures, can be found outdoors and in unheated buildings during the winter.

Adult Oriental cockroaches are shiny, dark brown or black, about 1 to 1-1/4-inch long and have nonfunctional wings incapable of flight. Females are about 1-1/4-inch long, broad and have only little pads for wings. Males are about one inch long, more slender and have wings not reaching the tip of the abdomen. Immature roaches (nymphs) are darker in color than adults, similarly shaped and wingless. Egg cases are dark reddish-brown, one inch long (largest of the common roaches), and appear slightly inflated.