Body of cockroach is elongated and dorsoventrally flattened. It is red brown in colour. Males are larger than females. Body is covered by brown chitinous exoskeleton. Cockroach is nocturnal and the body is segmented. It is divided into three distinct parts :
(a) Head : The head is triangular. It lies anteriorly at right angles to the longitudinal body axis. Head is formed by the fusion of six segments. The head is flexible and is covered by head capsule. The head bears two sessile compound eyes, one on each of its side. Two thread-like long antennae arise from membranous sockets. They are very sensitive. The anterior end of head bears mouth which is provided with mouth parts. These consist of labrum, a pair of mandibles, a pair of maxilla and labium. There is a medium lobe, hypopharynx which acts like tongue.
(b) Thorax : It consists of 3 segments : (i) prothorax, (ii) mesothorax, (iii) metathorax. Head is connected with the thorax by a short extension of the prothorax called the neck. Large sclerites covers the prothorax and shields the mesothorax. Each thoracic segment bears two walking legs. Each leg has 5 segments : (i) coxa, (ii) trochanter, (iii) femur, (iv) tibia, (v) tarsus. The first and second pairs of wings arises from mesothorax and metathorax respectively. The fore wings are called tegmina. Wings are used for flight.
(c) Abdomen : In both male and female it consist of 10 segments. The seventh sternum is boat- shaped in females and together with eighth and nineth sterna makes a broad genital pouch. The tenth segment bears two jointed filamentous structures which are known as anal cerci. The 9th segment bears a pair of short, thread-like style which lie ventral to anal cirri. The anal styles are not found in female cockroach