Morphology of Cockroach

• Morphology refers to study of form or externally visible features and in the case of plants or microbes, the term morphology precisely refers to this only. In case of animals this refers to the external appearance of the organs or parts of the body.

• The word anatomy conventionally is used for the study of morphology of internal organs in the animals. 

Cockroach:

·        Cockroaches are brown or black bodied animals that are included in class Insecta of Phylum Arthropoda.

·        Bright yellow, red and green coloured cockroaches have also been in tropical regions.

·        Their size ranges from ¼ inches to 3 inches (0.6-7.6 cm) and have long antenna, legs and flat extension of the upper body wall that conceals head.

·        They are nocturnal omnivores that live in damp places, all where. They are available in all homes and are serious pests and vectors of several diseases.

Morphology:

• The adults of the common species of cockroach, Periplaneta americana are about 34-53 mm in length with extended wings beyond the tip of the abdomen in males.

The body of the cockroach is segmented and divisible into three distinct regions –

·        Head

·        Thorax

·        Abdomen

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• The entire body is enclosed by a hard chitinous exoskeleton (brown in colour). In each segment, exoskeleton has hardened plates called sclerites (tergites dorsally and sternites ventrally) that are joined to each other by a thin and flexible articular membrane (arthrodial membrane).

Head:

• Head lies anteriorly at right angles to the longitudinal body axis, is triangular in shape and is formed by the fusion of six segments and shows great mobility in all directions due to flexible neck.

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Head region of cockroach : parts of head region

• The head capsule bears a pair of compound eyes. A pair of hair like antennae arise from membranous sockets lying in front of eyes. Antennae have sensory receptors that help in monitoring the environment.

• Anterior end of the head bears appendages forming biting and chewing type of mouth parts. The mouthparts 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 (hypopharynx), lies within the cavity enclosed by the mouthparts.

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Head region of cockroach : mouth parts

Thorax:

Thorax consists of three parts –

·        Prothorax

·        Mesothorax

·        Metathorax

• The head is connected with thorax by a small 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 (mesothoracic) 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 flying. 

Abdomen:

• The abdomen in both males and females consists of 10 segments. 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 gonapophysis. Males bear a pair of short, threadlike anal styles which are absent in females. In both sexes, the 10th segment bears a pair of jointed filamentous structures called anal cerci.