The adults of the common species of cockroach are Periplaneta Americana. The body of cockroach is long, flat from dorsi-ventral side and of brownish red colour. Adult cockroach has 25 mm to 45 mm length and breadth of 8 to 12 mm. The size of male is little long. The body of this animal is hard and protected by exoskeleton made of chitin. In each segment, exoskeleton has hardened plates called tergites and sternites that are joined to each other by a thin and flexible articular membrane called arthrodial membrane. Cockroach possesses bilateral structure. The body of the cockroach is segmented and divisible into three distinct regions - head, thorax and abdomen. There is no internal segmentation. Head : Head is triangular in shape and lies anteriorly at right angles to the longitudinal body axis. It is connected with thin neck to thorax. Head is formed by the fusion of six segments. The head capsule bears a pair of compound eyes. It is bean shaped. A pair of thread like antennae arise from membranous sockets. It can move in all directions. Anterior end of the head bears appendages forming biting and chewing type of mouth parts. The mouth parts are sensitive.
Mouth parts : The mouth parts consisting of a labrum (upper lip), a pair of mandibles, a pair of maxillae and a labium (lower lip). A median flexible lobe acting as tongue lies within the cavity enclosed by the mouth parts.
Thorax : Thorax consists of three parts - prothorax, mesothorax and metathorax. The head is connected with thorax by a short extension of the prothorax known as the neck. Each thoracic segment bears a pair of walking legs. The first pair of wings arises from mesothorax and the second pair from metathorax. Forewings called tegmina are opaque dark and leathery and cover the hind wings when at rest. The hind wings are transparent, membranous and are used in flight. Abdomen : The abdomen in both males and females consists of 10 segments. Each segment has tergites and sternum and lateral membrane. Eight and ninth tergite are covered with seventh tergite. Tenth tergite has groove in the middle and anus is followed by it. In male and female cockroach both along with tenth tergite. A pair of segmented Anal cerci is associated which is a sound receptor organ. Anal style comes out from the ninth strength of male cockroach. It leads in females. In females the 7th sternum is boat shaped and together with the 8th and 9th sterna forms a brood or genital pouch whose anterior part contains female gonopore, spermathecal pores and collateral glands. In males, genital pouch or chamber lies at the hind end of abdomen bounded dorsally by 9th and 10th terga and ventrally by the 9th sternum. It contains dorsal anus, ventral male genital pore and gena apophysis.
