External structure of cockroaches
The order “cockroaches” is quite numerous and numbers up to 7 and a half thousand species. In our territories, the most numerous is the red cockroach or Prusak, as it is also called. Black cockroaches are less numerous, with the American cockroach being a fairly rare species. The structure of cockroaches, despite their species, is almost identical, although they differ in size and color.
Interesting to know! The structure of modern cockroaches is practically no different from the structure of their ancient representatives of the order “cockroaches”, in the form of Ignaroblatta, which was found in fossils. Their size was 4 times larger than the Prussians, but at the same time they were smaller in size compared to modern giant cockroaches. Moreover, they were the most numerous representatives of this genus who lived within the ancient continent of Gondwana.
The structure of their body is considered quite perfect, so it is not surprising that these insects have retained all their basic qualities for many millions of years.
The cockroach has a flattened body, which allows it to penetrate through the narrowest cracks, while the body consists of 3 parts: head, chest and abdomen.
American (Periplaneta americana)
In fact, the homeland of American cockroaches is hot Africa, and they came to America with the help of cargo ships. After some time, they began to be found on almost all continents.
Food remains in huge quantities that accumulated in trash cans near houses, as well as a high level of unsanitary conditions in public places, led to the appearance of this type of cockroach in our country. The American cockroach can be easily distinguished from other types of similar insects by its large size, as well as by the shape of its body, which is oval in shape. In addition, this insect has a brown shell that looks like folded wings.
There is another factor that helps distinguish this insect from other types of cockroaches - this is the fact that the American cockroach is afraid of the cold. Already when the temperature drops to 0 degrees, these insects die. In addition, the American cockroach is characterized by an increased level of aggression, so it can attack both humans and domestic animals, which cannot be said about other types of similar insects.
Head structure
The cockroach's head is triangular in shape, and it is covered on top by a shield connected to the first segment of the chest. Therefore, you can see that only the back of the head peeks out from under the shield, and the rest of the head looks down. On both sides of the head there are compound eyes consisting of 1800 fragments. As a result, the insect perceives all objects in the form of a mosaic made up of many colored pieces. The eyes of cockroaches are not designed for detailed study of objects, but at the same time, the color resolution of these insects is 5 times higher than that of humans.
Interesting fact! Thanks to the presence of compound eyes, the cockroach is able to detect individual movements that follow with a frequency of at least 300 Hz. Therefore, he is able to see the movement of an object in slow motion, which helps him timely dodge flying objects, such as a slipper, for example.
In addition to these, one might say, compound eyes, on the front of his head there are 2 simple eyes, the functions of which have not been studied to this day. Experts say that thanks to these simple eyes, the insect can navigate perfectly in the dark.
The cockroach's long whiskers serve as organs of touch, smell and temperature determination. The whiskers are distinguished by the fact that they have nerve shoots that constantly send signals to the pest’s central nervous system. With the help of their whiskers, insects contact each other, and they can transmit and perceive the necessary information. After each molt, the whiskers of individuals grow by 1 segment, so you can determine how old the cockroach is. An adult may have about 80 of them, but this does not mean that the cockroach is 80 years old. Only specialists can do the calculations.
The insect's oral apparatus has a rather interesting structure, since each part of it is designed to perform separate functions. For example:
- The upper lip (lambrum) has a movable connection with the head and on its inner surface there are receptors that signal the composition of food.
- With the help of the lower jaw (mandible), the insect firmly holds food. The lower jaws look like curved plates with sharp teeth.
- With the help of the upper jaws (maxillae), the insect chews, grinds and grinds food. They are located above the lower jaws and are armed with chemoreceptors.
- The lower lip (labium) covers the oral opening from below and consists of several parts. Thanks to the presence of this lip, food particles do not fall down. In addition, the lower lip has taste and tactile receptors that help find food and analyze its origin.
- In the cavity of the oral pharynx there is a salivary gland and something similar to a tongue, thanks to which cockroaches drink water.
It is believed that the oral apparatus of these insects has not undergone significant changes over such a long period of their existence.
10 facts about COCKROACHS that you are better off not knowing
Circulatory system
The circulatory system of the cockroach (Fig. 83), like that of all arthropods, is not closed. Blood directly washes the internal organs and tissues while in the body cavity, transferring nutrients to them and carrying harmful waste products to the excretory organs. Blood does not participate in the transfer of oxygen and carbon dioxide, that is, in respiration. Its movement is ensured by the work of the heart - a longitudinal muscular tube located in the dorsal part above the intestines.
The cockroach's heart, pulsating rhythmically, drives blood to the head end of the body. The backflow of blood is prevented by the heart valves. When the heart expands, blood enters it from the back of the body through its side openings, which are equipped with valves that prevent blood from flowing back. In the body cavity, unlike the heart, blood flows from the front end to the back, and then, entering the heart as a result of its pulsation, it is again directed to the head.
The thoracic region and the purpose of the paws
On the thoracic part of the cockroach's body there are wings with elytra, as well as insect legs. Cockroaches, like any representative of the “insect” class, have 6 legs, that is, 3 pairs. Each tarsus is located on one of the thoracic segments and represents:
- Prothoracic legs, which have the shortest length and serve as “brakes” if the insect moves too quickly.
- Medium-thoracic paws that can move in any direction, providing the insect with high maneuverability.
- The metathoracic legs are designed to move the insect only forward. They are the longest in size.
The cockroach's paw is a rather complex mechanism, which includes 5 segments. The thighs, flattened in shape, are armed with spines below. The first 4 segments are armed with pads, and the fifth with claws with a suction cup located in the center. This allows the insect to crawl on both horizontal and vertical surfaces.
Interesting fact! Having relatively long legs helps the cockroach not only run fast, but also jump high. In addition, with the help of all 3 pairs of limbs, the cockroach takes care of itself from the head to the abdomen.
In other words, the insect uses 3 pairs of its legs for its intended purpose. Cockroaches are able to move along the surface at a speed of about 4 kilometers per hour. If a cockroach grew to the size of a cheetah, it could easily outrun it. With the help of sensitive hairs located on the legs, the cockroach assesses the situation around itself. In 1 minute he is able to change his trajectory up to 30 times.
Here, on the thoracic region, the wings with more rigid elytra are attached. Using the length of the wings, you can determine the gender of individuals: females have much shorter wings. These insects use their wings during the mating season, as well as when moving or falling. By spreading their wings, individuals demonstrate their readiness to mate. Despite the presence of wings, cockroaches cannot fly, although there is one species that lives in South and Central America that can fly.
Lifestyle
The black cockroach , like the red one, is a common acquaintance of ours. He has long been a person’s companion and is his lodger. Each cockroach has its own slit. There are any number of cracks and cracks in living spaces for cockroaches. The original homeland of the black cockroach has not been precisely established. His closest relatives live in Africa and Australia. Afraid of the light - that’s what people called the cockroach. Photophobia is one of the characteristic behavioral traits of cockroaches, inherited from distant ancestors. Cockroaches, both black and red, are nocturnal animals. They are busy with their business at night and early in the morning. With the onset of darkness, cockroaches go looking for food: small pieces of vegetables, bread crumbs, particles of granulated sugar. As polyphagous insects, they do not disdain all kinds of garbage; they are not averse to feasting on laundry soap, nourishing skin creams, and even... shoe polish. You can wash down such food with ink - it will not harm the body at all. In a year, 1000 black cockroaches eat 9.5 kg of food, but they dirty much more food.
Abdomen: structural features
A maximum of 9 abdominal segments can be distinguished, although it actually consists of 11 segments. The anus is located on the tenth segment, and the last segment is formed by paired outgrowths that have no purpose, but represent a separate sign of a certain type of cockroach. These growths have been preserved for millions of years, indicating their relict origin.
The female has a special capsule (ootheca) at the end of her abdomen, which contains 12-16 eggs and subsequently develops into the hatched larvae. Under favorable conditions (availability of water and food), this capsule appears in the female every couple of days.
Interesting to know! During the process of growth and development, not only the size of individuals changes, but also their weight, which at the beginning of development is about 2 mg, and at the end of the process about 8 mg. The larvae, in comparison with the imago, do not have wings, cerci and spines on their legs, but have short antennae. After the fifth molt, the insects develop genitals and complete external resemblance to adult cockroaches.
According to University of Massachusetts professor J. Kunkel, cockroaches are endowed with basic driving instincts, such as hunger, thirst, survival and reproduction. In order to understand whether cockroaches have a brain, you should study its internal structure.
Internal organs of a cockroach
According to some claims, a headless cockroach can live for several days. Such possibilities are associated with the structure of the nervous system and other organs, which allows the cockroach to live without a head.
Structure of the nervous system
The central nervous system of the cockroach is formed by 11 independent nerve ganglia. In the head of an insect there are only 2, but large, nerve nodes. They are located under and above the pharynx, and are responsible for the actions of the eyes, whiskers and probes located on the lips of the cockroach.
3 thoracic nodes, together with the subpharyngeal node, control the operation of the oral apparatus, wings, paws and head muscles, as well as the muscles of the thoracic region.
In the belly of the insect there are six small nerve ganglia, the largest of which is the terminal one, which is responsible for the functions of the genital organs and sensitive cerci.
Important point! The internal structure of the cockroach is such that it can easily do without a head, especially since its breathing is not connected to the nerve nodes located in the head. There is no pressure in his circulatory system, so he does not bleed. At the same time, he does not waste energy while being immobile, so he can easily do without food. Under certain conditions, it can live without a head for up to 1 month.
The nerve fibers of a cockroach are connected to all organs of the insect, including the sense organs. The cockroach not only has unique vision, it also has excellent hearing. The insect's auditory receptors are located near the anus.
Circulatory system
The circulatory system is of an open type, while the cockroach’s blood is white and washes all internal organs, being in free circulation. The cockroach's heart is a tubular organ located in the dorsal pericardium. The middle sinus contains the intestines, and the thoracic sinus contains the nerve cord.
Due to the work of the tubular organ, hemolymph (blood) is pumped through the circulatory system. The work of the heart is carried out due to pressure differences resulting from the work of the muscles. Blood is pumped slowly, so cockroaches are quite sensitive to changes in ambient temperature.
Respiratory system
On both sides of the abdomen there are tiny holes called spiracles, through which the insect breathes. There are 10 pairs of them, which means that on each side of the abdomen there are 10 such spiracles. From these holes extends a whole system of tubes - tracheoles, which ultimately connect with 3 pairs of several large tracheal trunks. Oxygen reaches all organs by diffusion.
Important fact! Cockroaches are able to hold their breath for up to 40 minutes, blocking their spiracles, which allows the insect to survive in difficult living conditions.
As a rule, a cockroach, being stationary, expends practically no energy. It is believed that they are in a state of movement for only 25% of their lives, so cockroaches are also considered the laziest insects.
Digestive system
When food enters the cockroach’s mouth, it is moistened with saliva (previously crushed) and enters the goiter through the esophagus, after which it is sent to the gizzard. Therefore, the process of digestion of food begins in the crop and ends in the stomach. After this, the food enters the intestine, which consists of the foregut and hindgut.
Interesting moment! The foregut consists of several parts. Immediately behind the mouth opening there is a buccal chamber with 6 teeth. With their help, the insect additionally crushes the food that has entered the mouth.
In the intestines of a cockroach there is a full range of bacteria and fungi that help the insect digest food objects, including even inedible food of inorganic origin.
Feces and urine are released through one anus. Urine is collected using special channels. They collect toxins dissolved in water throughout the body and send them to the anus.
Reproductive system
Males have a rather complex reproductive system. For example:
- The testes are located in segments 4-6 of the abdomen.
- The reproductive system includes the fungal (utricular) gland.
- The seminal vesicles empty into this gland.
- There are also organs of copulation.
- The female reproductive system is no less complex and consists of:
- From the ovaries, 8 avarioles each.
- From a pair of oviducts that are connected to the vagina.
- From the genital chamber where eggs accumulate. And collateral glands are associated with this chamber, which secrete a special secretion for the formation of a capsule (ootheca).
- From the ovipositor.
After fertilization, a capsule is formed into which the fertilized eggs enter.
Important point! The human cell nucleus includes 46 chromosomes, which are responsible for the transmission of hereditary information. Cockroaches have as many as 48 of them, although this is in no way evidence of the unique complexity of their body. Similar (relict) species of insects are distinguished by a large number of chromosomes.
According to scientists, cockroaches are more primitive, but the presence of 2 extra chromosomes indicates that the insects are quite resistant to external manifestations. It was this factor that turned out to be fundamental, ensuring the survival of the species for millions of years.
Interesting Facts
- In a second, an insect can run 75 cm.
- Cockroaches are very maneuverable - they can change the trajectory of their movement up to 25 times per second.
- The insect can live without a head for 10 days, a month without food and a week without water.
- Cockroaches breathe with their whole body and are able to hold their breath for 40 minutes.
- A person can survive exposure to 500 rads, while a cockroach can withstand 6400 rads.
- During life, the insect releases gases every 15 minutes, and after death it continues to release them for another 18 hours.
- If a cockroach is turned on its back, it will never turn back and will lie there until it dies from thirst or hunger.
- Cockroaches easily move from one country to another and immediately take root in a new place.
The black cockroach is distributed throughout Europe and is found in close proximity to human habitation.
