Q.Location of tergum.

The cockroach body is elongated, bilaterally symmetrical and dorso-ventrally flattened, and is triploblastic, eucoelomate and truly segmented. Because its circulatory system is open, its body cavity is filled with blood and is called the haemocoel rather than a plain coelom. The body is glistening brown to reddish-brown and is covered by a hard, non-living, chitin-built exoskeleton that gives strength, elasticity and a surface for muscle attachment; each segment carries four chitinous sclerites — a dorsal tergum, a ventral sternum and two lateral pleura.

The body has three regions — head, thorax and abdomen — joined by a flexible neck (cervix) between head and thorax. The head, formed by the fusion of six segments, bears a pair of antennae (long, jointed, tactile and olfactory feelers seated in antennal sockets), a pair of fenestrae (ocellar spots) at the antennal base, a pair of compound eyes (built of many ommatidia, each forming a partial image that together give a mosaic view), and biting-and-chewing mouthparts around a pre-oral cavity: the labrum (upper lip), a pair of mandibles (true jaws with serrated edges, moved by adductor/abductor muscles), a pair of maxillae (accessory jaws with sensory maxillary palps, also used to groom the antennae/legs), the labium (lower lip with sensory labial palps) and the hypopharynx (tongue, where the salivary duct opens). …