Question

Describe the external morphology of cockroach.

Answer 1

• The body of cockroach is elongated and dorsoventrally flattened. It is red-brown in colour. Males are larger than females. The body is covered by a brown chitinous exoskeleton. The 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. The head is formed by the fusion of six segments. The head is flexible and is covered by the head capsule. The head bears two sessile compound eyes, one on each of its sides. Two thread-like long antennae arise from membranous sockets. They are very sensitive. The anterior end of the head bears mouth which is provided with mouthparts. These consist of the labrum, a pair of mandibles, a pair of maxilla and labium. There is a medium lobe, hypopharynx which acts like the tongue.
• (b) Thorax : It consists of 3 segments : (i) prothorax, (ii) mesothorax, (iii) metathorax. The 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 arise from mesothorax and metathorax respectively. The fore wings are called tegmina. Wings are used for flight.