Cockroach – Class 11 | Chapter – 7 | Short Notes Series PDF
A Cockroach is probably the most loathed insect that ever existed. Cockroaches belong to the phylum Arthropoda. But the main fact is that cockroaches have inhabited the earth for the past 300 million years ago and still continue to be present on earth. Here, in this article we have discussed the external morphology and internal anatomy of a cockroach. The scientific name of the common cockroach is Periplaneta americana. The classification of cockroach is discussed below:
- Phylum – Arthropoda
- Class – Insecta
- Order– Dictyoptera
- Family– Blattidae
- Genus –Periplaneta
- Species– americana
The body of the cockroach is divided into:
- Head
- Thorax
- Abdomen
Head
It bears a pair of compound eyes and two long antennae arising from their head. The mouth is present on the anterior part which bears a pair of mandibles, a pair of maxillae and labium. A median flexible lobe acts as the tongue.
Thorax
The thorax is divided into three parts- Prothorax, Mesothorax, and Metathorax. The head and thorax are connected by prothorax, which is a short extension known as the neck. The mesothorax gives rise to the first pair of wings, while the second pair of wings arise from the metathorax. The thorax region also bears a pair of legs. It also consists of forewings called tegmina.
Abdomen
The abdomen of a cockroach is divided into 10 segments. The 7th sternum, along with the 8th and 9th sterna bears a broad genital pouch. The 10th segment contains a pair of the joint filamentous structure called anal cerci.
Digestive System
It has a long and coiled alimentary canal divided into three parts- foregut, midgut, and hindgut.
- Foregut or Stomadaeum- It comprises the buccal chamber, pharynx, oesophagus, crop, and gizzard.
- Midgut or Mesenteron- It is short compared to the foregut and lined with glandular endoderm. Eight blind globular hepatic caeca are present between gizzard and midgut, which secretes digestive enzymes.
- Hindgut or Proctodaeum- It consists of ileum, colon, rectum.
Nervous System
The nervous system of a cockroach is divided into- central nervous system, peripheral nervous system, and sympathetic nervous system.
- The central nervous system consists of the brain.
- The peripheral nervous system consists of nerves.
- The sympathetic nervous system consists of a frontal ganglion.
Respiratory System
The respiration in cockroaches occurs through the trachea present on the lateral side of the body. It opens through 10 pairs of small holes called spiracles.
The trachea is sub-divided into tracheoles that carry oxygen from outside to different parts of the body.
Excretory System
The metabolic waste is excreted by ciliated and glandular Malpighian tubules. The waste is excreted in the form of uric acid.
Circulatory System
The cockroach has an open circulatory system. The blood flows through the body cavity. The circulatory system consists of a heart, anterior aorta, and a system of ill-defined blood spaces known as sinuses.
Sensory Organs
- Thigmoreceptors: They perceive sense for touch and are present on the body, legs, antennae and maxillary palps.
- Olfactory Receptors: They are present on antennae and palps and sense various smells.
- Gustatory Receptors: They are present on the maxilla and labial palps and can perceive a sense of taste.
- Thermoreceptors: These are present on the pads between the first four tarsals and can sense changes in temperature.
- Auditory Receptors: They are present on the anal cerci and responsible for hearing.
Reproductive System
- The male reproductive system consists of a pair of testes present in the 4th and 6th segments of the abdomen laterally.
- The sperms are stored in the seminal vesicles.
- The female reproductive system consists of two ovaries in the 2nd and 6th segment of the abdomen.
- Oviducts of each ovary connect to form a single median oviduct.
- Sperms transfer through spermatophores.
- The fertilized eggs are present in a case like structure called oothecae.
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