They may be seen during the daytime, particularly if a heavy population is present or if there is some other stress, such as a lack of food or water or an application of pesticides. The German cockroach is the most economically important urban pest. It is also the most common cockroach species in houses, apartments, restaurants, hotels, and other institutions. This is true not only in Pennsylvania but also throughout the United States and in most parts of the civilized world. While they have fully developed wings, they do not fly.
Nymphs are similar in appearance to adults except that they are smaller and lack wings.
The German cockroach is best identified by its small size and by two dark parallel lines running from the back of the head to the wings. The German cockroach is the most successful of the species infesting buildings in Pennsylvania. There are several reasons for this cockroach's persistence and the difficulty of controlling it. German cockroaches produce a larger number of eggs per capsule and they undergo the shortest time from hatching until sexual maturity, resulting in a rapid population growth. A greater number of nymphs hatch successfully because the female carries the egg capsule during the entire time the embryos are developing within the eggs.