Describe the external body structure of a cockroach.

(N/A) $\rightarrow$ The adults of the common species of cockroach are $Periplaneta$ $americana$.
$\rightarrow$ The body of the cockroach is long,dorso-ventrally flattened,and brownish-red in colour.
$\rightarrow$ Adult cockroaches have a length of $25 \ mm$ to $45 \ mm$ and a breadth of $8 \ mm$ to $12 \ mm$.
$\rightarrow$ The body is covered by a hard,chitinous exoskeleton.
$\rightarrow$ In each segment,the exoskeleton has hardened plates called tergites (dorsally) and sternites (ventrally),which are joined to each other by a thin and flexible articular membrane called the arthrodial membrane.
$\rightarrow$ The body is segmented and divisible into three distinct regions: head,thorax,and abdomen.
$\rightarrow$ Head: The head is triangular in shape and lies anteriorly at right angles to the longitudinal body axis. It is formed by the fusion of six segments and bears a pair of compound eyes and a pair of thread-like antennae.
$\rightarrow$ Mouth parts: The mouth parts consist of a labrum (upper lip),a pair of mandibles,a pair of maxillae,and a labium (lower lip). $A$ median flexible lobe acting as a tongue (hypopharynx) lies within the cavity enclosed by the mouth parts.
$\rightarrow$ Thorax: The thorax consists of three parts: prothorax,mesothorax,and metathorax. Each thoracic segment bears a pair of walking legs. The first pair of wings arises from the mesothorax (tegmina) and the second pair from the metathorax.
$\rightarrow$ Abdomen: The abdomen in both males and females consists of $10$ segments. In females,the $7^{th}$ sternum is boat-shaped and forms a brood or genital pouch. In males,the genital pouch lies at the hind end of the abdomen,bounded dorsally by the $9^{th}$ and $10^{th}$ terga and ventrally by the $9^{th}$ sternum. Anal cerci are present in both sexes,while anal styles are present only in males.