The only experience most people have with cockroaches is that of German cockroaches in kitchens or American cockroaches crawling out of sewers at night. However, there are about 4,000 cockroach species around the world, and only a few of these are considered to be pests. German and American cockroaches are basically tropical insects. Thus, they select indoor sites for harboring such as in kitchens and bathrooms that provide the temperature and humidity of their natural habitats.
Adults and the immature stages are brown to blackish brown, oval, and flattened. The head is usually concealed from above by the large pronotum. The antennae are very long, and they have chewing mouthparts. Most adult males have wings and can fly; females often have short wings or none at all and do not ﬂy. Nymphs are similar to adults except for their size and the absence of wings. Eggs are enclosed within an egg case. There are five to 12 nymph stages, depending on species.
Cockroaches locate food by using chemical receptors on their antennae and mouthparts. In general, they prefer carbohydrate foods but also will feed on material high in fat and protein. The availability of food controls their reproduction. The female German cockroach actively forages and eats when she is preparing her egg case, but she remains relatively inactive once the egg case is formed and during the 28 days she carries it. Cockroaches defecate while feeding and moving about, spreading pathogens to surfaces they contact.
Their legs have strong spines and setae, and the pads on the undersides of their feet enable them to climb. A large pad between the claws at the end of each leg helps cockroaches move quickly on smooth and vertical surfaces. This can be seen in the movement of German cockroaches in kitchens and the American cockroaches indoors and out.
Oriental cockroaches do not have the large pad between their claws. These cockroaches can easily climb rough horizontal surfaces, but they can not climb smooth vertical surface.
They often become trapped in sinks and bathtubs that have smooth sides, and give the false impression they have come up the drain pipe.