Comprehensive Guide to Cockroaches: Structure, Life Cycle, and Essential Life Processes

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.

 

Structure and  Life Processes of 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.


External 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.

Structure of Cockroach with labels

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.

Structure of Cockroach head with labels

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.

Structure of Mouthparts of a Cockroach

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.

Structure of cockroach leg

Abdomen

It consists of ten segments, but only the first seven are visible because the tergum of the 7th 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 9th segment.

The female is distinguished by the possession of a genital pouch, below the 7th 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 cockroaches

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


Internal Structure of Cockroach

  1. Digestive System

    • Foregut: Includes the mouth, pharynx, esophagus, crop, and gizzard.
    • Midgut: Site of digestion and absorption.
    • Hindgut: Involves the intestine, rectum, and anus.

  2. Circulatory System

    • Open circulatory system with a dorsal heart pumping hemolymph.

  3. Respiratory System

    • Tracheal system with spiracles leading to a network of tracheae and tracheoles.

  4. Nervous System

    • Central nervous system with a brain and ventral nerve cord, along with peripheral nerves.

  5. Reproductive System

    • Male: Testes, vas deferens, seminal vesicles, and accessory glands.
    • Female: Ovaries, oviducts, spermatheca, and accessory glands.


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 


Labelled Drawing of Digestive system of cockroach

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.  


respiratory system of Insect


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 10th 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.

Reproduction, Incomplete metamorphosis in cockroach

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

Cockroaches, while often considered pests, have several economic implications, both negative and positive. Understanding their economic importance helps us grasp their impact on human activities and ecosystems.

Negative Economic Importance

  1. Pest Control Costs

    • Cockroaches are major household pests, necessitating significant expenditure on pest control measures, including insecticides, traps, and professional extermination services.

  2. Food Contamination

    • Cockroaches can contaminate food with their droppings, saliva, and body parts, leading to foodborne illnesses. This contamination results in economic losses in food production, storage, and handling industries.

  3. Health-Related Costs

    • Cockroaches are vectors for various pathogens, including bacteria like Salmonella and E. coli, which can cause food poisoning. The allergens they produce can also trigger asthma and other allergic reactions, leading to increased healthcare costs.

  4. Property Damage

    • Cockroaches can cause damage to property by chewing on materials like paper, fabric, and electrical wiring, leading to repair and replacement costs.

  5. Reduced Property Values

    • Infestations can decrease property values and make properties less attractive to potential buyers or renters.

Positive Economic Importance

  1. Scientific Research

    • Cockroaches are widely used in scientific research due to their resilience and adaptability. They are valuable in studies related to neurobiology, behavior, and pest control methods.

  2. Decomposition and Nutrient Cycling

    • In natural ecosystems, cockroaches play a role in decomposition by breaking down organic matter, which recycles nutrients back into the soil. This process is crucial for maintaining soil health and fertility.

  3. Biological Control Agents

    • Some cockroach species can be used as biological control agents to manage pest populations in agricultural settings. For example, certain cockroaches can prey on other harmful insects.

  4. Animal Feed

    • Cockroaches are being explored as a sustainable source of protein for animal feed, particularly in the context of growing interest in insect farming as an alternative protein source.

  5. Traditional Medicine

    • In some cultures, cockroaches have been used in traditional medicine for their purported healing properties. Extracts from cockroaches are believed to have medicinal benefits and are used in various remedies.
For further reading on the economic impact of cockroaches, you can refer to reputable sources such as PestWorld and  scientific journals on entomology and pest management. 

Control of Cockroach 

Controlling cockroach infestations involves a combination of preventative measures, sanitation practices, chemical treatments, and sometimes professional pest control services. Here is a detailed guide on how to control cockroaches effectively:

Preventative Measures

  1. Seal Entry Points

    • Inspect and seal cracks, crevices, and gaps around doors, windows, pipes, and utility lines to prevent cockroaches from entering.

  2. Proper Food Storage

    • Store food in airtight containers and keep pet food sealed. Clean up food spills and crumbs immediately.

  3. Eliminate Water Sources

    • Fix leaky faucets, pipes, and drains. Avoid leaving standing water in sinks or other containers.

Sanitation Practices

  1. Regular Cleaning

    • Clean kitchen counters, floors, and appliances regularly to remove food particles and grease. Pay special attention to areas under and behind appliances.

  2. Trash Management

    • Dispose of garbage regularly and use trash cans with tight-fitting lids. Clean trash cans periodically to remove residues.

  3. Clutter Reduction

    • Reduce clutter in storage areas, basements, and garages where cockroaches can hide and breed.

Chemical Treatments

  1. Bait Stations

    • Use cockroach bait stations, which contain a slow-acting poison that cockroaches carry back to their nests, spreading the toxin to other cockroaches.

  2. Gel Baits

    • Apply gel baits in cracks, crevices, and other areas where cockroaches are likely to travel. Gel baits are effective because they can be placed in hard-to-reach areas.

  3. Insecticidal Sprays

    • Use residual insecticidal sprays in areas where cockroaches are seen. Follow the manufacturer’s instructions carefully and use sprays in combination with other methods.

  4. Dust Insecticides

    • Apply dust insecticides like boric acid or diatomaceous earth in wall voids, behind baseboards, and under appliances. These powders can be effective in killing cockroaches that come into contact with them.

Biological Control

  1. Natural Predators

    • Introduce natural predators such as certain species of ants and spiders, which can help control cockroach populations.

  2. Parasitoids and Pathogens

    • Research is ongoing into the use of parasitoid wasps and microbial pathogens that specifically target cockroaches.

Professional Pest Control

  1. Inspection and Assessment

    • Professional pest control services can conduct a thorough inspection to assess the extent of the infestation and identify the species of cockroach present.

  2. Integrated Pest Management (IPM)

    • Professionals often use an IPM approach, combining multiple control methods, including chemical, biological, and mechanical strategies, to manage cockroach populations effectively.

  3. Follow-Up Treatments

    • Regular follow-up treatments may be necessary to ensure the infestation is fully eradicated and to prevent future infestations.

Home Remedies (Supplementary Measures)

  1. Baking Soda and Sugar

    • Mix equal parts of baking soda and sugar and place it in areas where cockroaches are seen. The sugar attracts cockroaches, and the baking soda disrupts their digestive system.

  2. Essential Oils

    • Certain essential oils like peppermint, eucalyptus, and tea tree oil can repel cockroaches. Mix a few drops with water and spray in affected areas.

For more information and guidance on cockroach control, you can refer to resources such as PestWorld and the Centers for Disease Control and Prevention (CDC).


Conclusion

The structure of a cockroach is highly specialized, allowing it to thrive in various environments. From its sensory-rich head to its flexible abdomen, each part of the cockroach's anatomy plays a vital role in its survival and adaptability. For further reading, you can explore reputable sources like Encyclopaedia Britannica and National Geographic.

By understanding the structure of cockroaches, we gain insights into their remarkable resilience and evolutionary success.


Free Notes on Structure Life Cycle of Cockroach 

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