The American cockroach is the largest species of common cockroach, and often considered a pest. American cockroach adults grow to an average length of around 4 centimetres . They are reddish brown and have a yellowish margin on the body region behind the head. Immature cockroaches resemble adults except that they are wingless. The insect can travel quickly, often darting out of sight when someone enters a room, and can fit into small cracks and under doors despite its fairly large size. It is considered on e of the fastest running insects. This cockroach thrives in warm, damp environments, such as sewers, roof voids, wall cavities. It will be found living and breeding outdoors.