Structure Life Cycle and Other Life Processes of Cockroach

Objectives       

This  blog post provides readers with the following objectives. The reader will be able to:

o   Identify cockroach.

o   Describe the external features of the nymph and adult cockroach.  

o   Discuss the life cycle and other life processes of the cockroach.

 

Cockroach

Phylum: Arthropoda

Class: Insecta

Order: Dictyoptera

Habitats of Cockroach

Cockroaches are found in cupboards, cracks, and crevices in walls, drawers, toilet pits, dust bins etc.

Examples of Cockroach

Cockroaches are mainly nocturnal and will run away when exposed to light. The common ones are Blatta orientalis and Periplaneta American.

Structure of Cockroach

Cockroach has broad, dorso-ventrally flattened body and a relatively small head.

The whole body is covered by a dark reddish-brown exoskeleton of chitin called cuticle. The body is divided into three parts, the head, the thorax and the abdomen.

The exoskeleton covering the thorax and abdomen is divided into dorsal plate, the tergum and ventral plate, the sternum.

This image is credited to D G Mackean www.biology-resources.com

Head

The head is oval in shape and inconspicuous in dorsal view. 

It bears a pair of large compound eyes and a pair of long, flexible antennae (singular: antenna). The antennae are sensitive to touch, smell and vibration.

The underside of the head bears biting and chewing mouthparts.

Mouthparts

The mouthparts consist of the upper lip or labrum and three pairs of jaws.

The first pair of jaws, called mandible, is strong with serrated inner edges for biting. They work against each other like the blades of pair of scissors.

The second pair of jaws, first maxillae consisting of jointed maxillary palp, located behind the mandibles for cutting and chewing.

The third pair of jaws, second maxillae, forms the innermost jaws. They have labial palps and their bases are fused to form lower lip or labium.

Thorax

It consists of three segments; prothorax, mesothorax and metathorax. The mesothorax and metathorax bear a pair of wings, the forewings and hind-wings.

The forewings called elytra (singular: elytron) or tegmina (singular: tegmen) are thick, chitinous plates, which cover two-thirds of the abdomen. Their function is to protect the hind-wings when at rest.  

The hind-wings are delicate membranous sheets of chitin used for short distance flight.

Each thoracic segment bears a pair of jointed walking legs. Each walking leg consists of five segments: coxa, trochanter, femur, tibia and tarsus.

The tarsus ends in claws with a soft hair pad called arolium (plural: arolia) which prevent slipping.

Abdomen

It consists of ten segments, but only the first seven are visible because the tergum of the 7^th segment covers the rest of the segments.

The last segments carry a pair of segmented sensory structure called cerci (singular: circus). Males bear a pair of shot, unjointed structure called anal style on the sternum of the 9^th segment.

The female is distinguished by the possession of a genital pouch, below the 7^th segment. The genital pouch receives sperms during copulation and also carries egg-case.

Eight pairs of spiracles are present in the abdomen. 

Difference between Male and Female Cockroach

Male cockroach	Female cockroach
1.      Presence of anal style on the ninth segment	1.      Absence of anal style
2.      Possesses narrow abdomen	2.      Possesses broad abdomen
3.      No genital pouch	3. It has genital pouch
4.      Spermatheca absent	4. Spermatheca present
5.      Larger in size	5. Smaller in size

Life Processes of Cockroach

Nutrition in Cockroach

Cockroach is omnivorous which feeds on all kinds of organic material such as dead insects, its own ootheca, books and clothing. 

The food is cut chewed using the mouthparts. During chewing, saliva is released on to the food containing enzymes called amylase which converts starch to maltose. The saliva moistens and lubricates the food to facilitate swallowing. The food passes down the esophagus into the crop. The food leaves the crop and enters the gizzards where it undergoes further break down. Digestive caecum produces weak acidic fluid which emulsifies fats. The food particles of appropriate size are filtered into midgut, where the majority of digestion takes place. The midgut produces enzymes that convert maltose to glucose, proteins to amino acids and fats to fatty acids and glycerol. The end products are absorbed in the midgut and the digestive caecum. The undigested food moves down into the hindgut and rectum. Water is absorbed and later the feces pass out of the anus 

Respiration in Cockroach

The respiratory system of cockroach, like all insects, is made up of tiny openings called the spiracles and series of small tubes called trachea.

The trachea branch to form a network of moist tubules called tracheoles in the tissues.

Oxygen enters the tracheal system through the spiracles. Oxygen diffuses into the tracheoles where eventually reaches the cells, while carbon dioxide diffuses out through the tracheae, and leaves the body by the spiracles.  

Excretion in Cockroach

The main excretory products of insects are CO₂ and nitrogenous waste. Metabolic wastes are collected by a series of tubules called Malpighian tubules. The Malpighian tubules absorb nitrogenous waste from the blood and convert them into uric acid. It is passed into the hindgut and eliminated together with the feces through the anus.

­­Irritability in Cockroach

The head bears a pair of compound eyes, for vision and a pair of antennae, sensitive to touch, smell and vibration. The 10^th segment bears a pair of jointed anal cerci. They bear minute sensory hair sensitive to sound and other vibrations.

Life Cycle of Cockroach

The life cycle of cockroach shows an incomplete metamorphosis (egg, nymph and adult).

During copulation, the male produced sperms and discharged them into the female through the genital pore.

The sperms are stored in the sperm pouch or spermatheca of the female. The sperms fertilize the eggs inside the female (internal fertilization).

The fertilized eggs are enclosed in an egg case called ootheca. The female carries the ootheca in her genital pouch for some time and later deposited in a dark, warm place or in cracks.

After six weeks, the eggs hatch into young, sexually immature, colorless, and wingless cockroaches called Nymphs. The nymphs feed and develop into the adult.

Growth in Cockroach

Growth occurs by the process called Ecdysis or molting. Ecdysis is the periodic shedding of the exoskeleton of an arthropod to enable growth to take place. Each immature stage is referred to as instar.

­Economic Importance of Cockroach

1. They destroy food and stain valuable items like books, papers, shoes, clothes drawers etc.

2. They transmit disease causing organisms that cause disease such as cholera, leprosy, typhoid, dysentery, tuberculosis. 

3. They contaminate food and water with their feces.

4. They feed on food and can leave an offensive odor.

5. Cockroaches have been shown to be linked with allergic reactions in humans with asthma.

 

Control of Cockroach 

1.  By making surroundings clean and tidy by preventing clutter things.

2.    All food left over should be well placed.

3.    Their hideouts should be kept dry and less humid to reduce their reproduction. 

4. Insectides could be used.

5. By trapping them on sticky traps and vacuuming them up.

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