Cockroaches are also called roaches belonging to the order Blattodea, which also include termites. About 30 cockroaches reside with humans among 4600 species of cockroaches. Cockroaches are one of the oldest living organisms, they originated in the Carboniferous period. Cockroaches are characterized by a flattened oval body, long threadlike antenna, and finally a shining black or brown leather integument.
Cockroaches have chewing mouthparts and are likely among the most primitive living neopterin insects.
The scientific name of cockroaches is Blattodea.
Scientific Classification of Cockroach
Classification of cockroach is given below -
Kingdom - Animalia
Phylum - Arthropoda
Subphylum - Hexapoda
Class - Insecta
Superorder - Dictyoptera
Order - Blattodea
Different families of cockroach species in the order Blattodea are Anaplectidae, Blaberidae, Blattidae, Corydiidae, Cryptocercidae, Ectobiidae, Lampron Blattidae, Nocticolidae, Tryonicidae and others.
Structure of Cockroaches
The body of an adult cockroach is 2–5 cm long and about one centimetre wide. The fragmented cockroach body parts are clearly divided into three distinct divisions - the head, thorax, and abdomen. The head and thorax are joined together by a soft area called the neck or cervix.
The study of the external morphology of the insect's body is helpful in finding all the characteristics of a common winged insect. In addition to cockroaches, the knowledge of symptoms described in the definition of a common insect is evident in the body of grasshoppers.
The head of an insect is made up of 6 different sections, but these sections are connected in such a way that they are not clearly visible. The antennae are present in the second section of the head, mandibles in the fourth section, the maxillae in the fifth section and the labium appendages in the sixth section. Apart from these, a pair of compound eyes and three ocelli are also situated.
The insect's thorax is divided into three distinct segments, the first section is called the prothorax, the second section is called the mesothorax and the last section is called the metathorax. Each pair of the thorax has one pair of legs and one pair of wings are present in the mesothorax and posterior thorax. Hence, the mesothorax and metathorax are collectively called the terothorax. Wings are found in them to support the wings. One respiratory pore or spiracles are also found on both the mesothorax and metathorax.
The abdomen of the insect is usually divided into 11 segments. The tympanum of the ear is found in the first section of the abdomen. and in each section, you can find a respiratory cavity or spiracles. In the last segment of the abdomen, a pair of sarsai and a female ovipositor is also situated.
The insect's segmented or divided body into different twenty sections helps them to perform many tasks simultaneously and provides the necessary elasticity in their body. The thoracic section of the insect is helpful in walking and flying while the genital organs of the insect's abdomen are helpful in reproduction.
Cockroaches Life Cycle
All the cockroaches go through three phases of the life cycle egg, nymph and adult. The life span of these cockroaches ranges between 6 to 15 months, the cockroach lifespan varies depending on species, moisture and temperature.
Egg - The first stage of the Cockroach life cycle is an egg. They lay a case of 10 to 15 eggs in warm, humid and secluded spots of home and other places, It is in the form of small leathery capsules. Some of the particular areas where eggs can be found are under stoves, sinks, and appliances. Cockroaches take about one to two months to hatch from the egg, this egg stage can last from 14 - 100 days depending on the species and the climate. In general, the higher the temperature, the faster the cockroaches will develop. One German cockroach can produce up to 300 eggs in a year, they create multiple egg cases during their lifetime.
Nymph - This is the second stage of the cockroach life cycle. Nymph hatches and undergoes several moults. They grow a little every time they shed their skins. Once they emerge from their old shell, Immature pests have a soft white body, that gets hardened and changes their colour to brown. They reach their full adult size and colour with their last moult.
Adult - Once they reach their adult phase and reproduce, they repeat the cycle again. Since the lifespan of cockroaches is relatively long, they can infest the building by the thousands and finally it would be difficult to control.
Types of Cockroaches
There are nearly 4,500 types of cockroaches in the world, here, we will only discuss some of the common types of cockroaches.
German cockroach - The scientific name of cockroach is Blattella germanica and they are one of the most common species. The length of german cockroaches ranges from 13 -14 mm, they are pale yellow in colour, with two dark-brown stripes behind the head. This type of cockroaches lifespan is nearly 12 months and they produce more eggs compared to the other species.
American cockroaches - Its scientific name is Periplaneta americana and it is one of the largest cockroaches commonly found in the home, they can grow up to a length of 53mm. They are reddish-brown in colour with light yellow bands around the shield behind the head. Both males and females of the American cockroaches have wings and they are capable of flying short distances. They can commonly be found in households where food is stored.
Brown-banded cockroaches - The scientific name of brown-banded cockroaches is Supella longipalpa and they can grow up to a length of 13mm. Females of these species have reddish-brown to dark brown wings and the wings of the male of these species are dark brown towards the base and lighten as the wings get extended to the tip. In brown-banded cockroaches, only males are capable of flying and both males and females have two light yellow bands on their bodies. These cockroaches' lifespan ranges from three to 11 months.
Oriental cockroach - The scientific name of oriental cockroach is Blatta orientalis, and they have glossy dark brown or black body. Females of these species can grow to a length of 32 mm and males can grow to a length of 25 mm. In oriental cockroaches both males and females are not capable of flying. The life span of these types of cockroaches is nearly about 6 months. These cockroaches primarily feed on decaying organic matter.
Some of the other popular types of cockroaches are albino cockroach, Australian cockroaches, Asian cockroach, lobster cockroach, Cuban cockroaches, death head cockroach, field cockroaches, Florida woods cockroach, flying cockroach, green cockroach, sand cockroach, Surinam cockroaches, Turkestan cockroach, wood cockroach and furthermore.
Reproductive System of Cockroaches
Cockroaches are unisexual animals also known as dioecious.
The male reproductive system of cockroaches consists of a pair of testes, vasa deferentia, and ejaculatory duct, utricular gland, phallic gland and the external genitalia. Testes lie on each lateral side of the abdominal found between the fourth and the sixth segment. A thin vas deferens arises from each testis and opens into the ejaculatory duct through the seminal vesicle and the ejaculatory duct opens into the male gonopore, which is situated ventral to the anus. A mushroom-shaped gland is present in the abdominal segment, which is an accessory reproductive male gland. Male gonapophysis made up of chitin represents the external genitalia. Sperms are stored in the seminal vesicles, and those sperms are glued together to form a bundle known as spermatophores and it is discharged during copulation.
The female reproductive system of cockroaches consists of mainly two large ovaries. It is found in between the second and sixth abdominal segments, each ovary forms a group of eight ovarian tubules or ovarioles containing a chain of developing ova. All the oviducts of the ovaries unite to form a single median oviduct, which is also called a vagina and it opens into the genital chamber. In the sixth segment of the cockroach, spermatheca is present, which opens into the genital chamber.
Alimentary Canal of Cockroaches
The digestion of food in cockroaches takes place with the help of specialized cavities. The alimentary canal has been mainly divided into three parts: foregut, midgut and hindgut. The foregut is the starting part of the alimentary canal comprising the mouth and surrounded by the parts of the mouth. The midgut creates the real gut namely the mesenteron and it comprises the whole stomach or ventriculus. The hindgut is a coil-like structure having anterior ileum, middle colon, and posterior rectum. It is the final stage of an alimentary canal connected to the posterior rectum having openings to the exterior through the anus.
Digestion in cockroaches begins from the mouth, where the parts like mandibles and maxillae help to chew the food. Salivary carbohydrases digest the food partially in the mouth itself and the salivary juice provides the required lubrication to swallow the food. The further food moves to the oesophagus and then on to crop. This is the place where food is stored temporarily in the masticated form. After that, the next point where the food moves are the gizzard, where the grinding of the food takes place. The regurgitation of food would be prevented by the smooth valve name stomodeal right, which ensures the smooth passage of food in the stomach. Once the food enters the stomach, it is treated with digestive enzymes created by gastric caeca. Those enzymes are invertase, amylase, tryptase, maltase and lipase. All the residual fats, proteins and carbohydrates are absorbed in this stage.
Use of Cockroaches
In Research and Education - Cockroaches are very easy to rear and their resilience, they have been used as insect models in the laboratory. Particularly in the field of neurobiology, reproductive physiology, and social behaviour. They are convenient for the studies as they are large and simple to rise in the laboratory environment. These conditions make it suitable for research, schools and undergraduate biology studies. It can also be used for experimenting with topics like sexual pheromones, spatial orientation, aggression, activity rhythms and behavioural ecology. According to research conducted in 2014, humans fear cockroaches the most, even more than mosquitoes due to evolutionary aversion.
As Food - Cockroaches are considered disgusting in western culture, but they are eaten in many places in the world. The household cockroaches may carry bacteria and viruses. But cockroaches grown under laboratory conditions can be used to prepare nutritional food. In some places like Mexico and Thailand, the heads and legs of the cockroaches are removed. The remainder of the cockroach would be boiled, sauteed, grilled, dried or diced to consume. Cockroaches have become a popular medicine and the farming of cockroaches is increasing with time.
Some of the interesting facts about cockroaches are -
Cockroaches can live for a week without their head
Cockroaches can hold their breath for a duration of 40 minutes.
Cockroaches can run at a speed of three miles per hour.
The newborn baby of German cockroaches become adults in a short duration of just 36 days.
It is believed that cockroaches are really old, they originated 280 million years ago known as the carboniferous era.
Cockroaches can live for a month without food.