The sense organs of insects briefly. Nervous system and sense organs of insects. Reception and receptors

The temperature-regulating systems in insects are better studied than in other invertebrates, on the one hand, apparently as a result of the fact that insects have diverse thermoregulatory capabilities. On the other hand, this is determined by the undoubted simplicity in keeping insects, which simplifies the experimental conditions in experiments. Most insects are endothermic. However, some insect species, such as hawks, bees, and bumblebees, can exhibit behavior reminiscent of endothermic creatures during the period of preparation for flight.

All types of insects have developed complexly functioning thermoreceptors located on the trunk, antennae and limbs. In addition, temperature-sensitive cells have been found in the thoracic ganglia. Thus, for example, under conditions of cooling of the second and third thoracic segments in the moth (Hyalophora), there is a cessation of the rhythmic movements of the muscles that ensure the flight of the insect. Instead of coordinated movements, chaotic twitches are noted, accompanied by a rattle (like a whistle) and reminiscent in nature of muscle tremors in placental creatures and birds. If the thoracic ganglia are again warmed to the optimum temperature, then, despite the low ambient temperature, the moth stops trembling and attempts to take off are made.

Thermoreceptors in endothermic insects, such as flies and cicadas, are involved in the coordination of thermoregulatory behavior. Insects only then show its motor activity and the body temperature rises to I7-20T. At night, they fall into a stupor, from which they emerge when the air temperature begins to rise after the sun rises. Various species of grasshoppers position their body across the direction of the sun's rays, which allows them to absorb the energy of the sun to a greater extent and raise their body temperature above the ambient temperature for a short time. During the day, they change the position of their body and thus regulate heat absorption and heat loss. The change in body temperature during the day allows grasshoppers to develop maximum motor activity.

Endothermic insects increase their heat production before flight due to rhythmic contractions of the flying muscles, and therefore the temperature in the entire region of the chest wall and especially the flying muscles rises "- Usually, both groups of flying muscles (flexors and extensors) contract simultaneously. Wings during In this case, they almost do not move, or these movements are minimal.In such cases, the temperature of the chest reaches 40-41 ° C, which occurs due to heat production during muscle contractions.During the flight, the body temperature of insects can lie in a wide range of ambient temperatures - in bumblebees it is is maintained at a level of 10 to 25 ° C. This is possible as a result of the fact that insects are able to change both their heat production and heat loss. Lepidoptera, butterflies, for example, switch due to a corresponding change in the position of the wings from active flight to gliding and production during this less heat.

The thorax of endothermic insects is well isolated due to the thick, numerous hairline. As soon as the temperature of their chest exceeds 40 ° C, the vessels of the circulatory system of the back begin to contract rhythmically and move cold blood from the abdominal to the chest cavity; the temperature of the chest due to this decreases. Before the blood returns to the vessels of the back, it passes through open areas of the body on its way, where it is cooled by the ambient temperature, which also leads to a decrease in the temperature of the chest. Some species of insects increase heat transfer by increasing the evaporation of water from the internal or external surfaces of the body. This type of heat transfer can lead to a violation of the water content in the body. Only blood-sucking insects, such as the tsetse fly, can quickly and effectively evaporate water. Through an enlarged tracheal opening, they increase the return of water in the form of steam and reduce body temperature by 1.6 ° K below ambient temperature due to evaporation.

When the ambient temperature rises, insects are forced to repeatedly interrupt their flight, because, despite the presence of numerous protective mechanisms, they cannot avoid overheating of the body. During rest, their body temperature decreases due to insignificant heat production and due to a large temperature gradient between the body and the environment, which allows them to soon continue their flight again.

At a low ambient temperature, the increased heat transfer to the air (convection) during the flight increases so much that the body temperature, despite the maximum heat production, decreases. In this case, the insects also interrupt their flight. Due to repeated buzzing, they raise their body temperature to the level at which flight again becomes possible.

The flight success of bees and bumblebees during foraging depends on the ambient temperature. Bumblebees begin their search already at an air temperature of 5 to 10 ° C. During stops on a flower, they can cool down so much that without additional flapping of their wings they cannot start again. At higher ambient temperatures (up to 20°C), they leave the flower before their body temperature drops below a critical level. A small distance in the territory between flowers contributes to a successful flight. With an increase in the flight distance between two flowers, the body temperature of a bumblebee can rise so much that even at a low ambient temperature during a stop on a flower, it does not always reach the optimal level.

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Sense organs in insects

Zhdanova T. D.

Coming into contact with the varied and energetic activities of the insect world can be an amazing experience. It would seem that these creatures carelessly fly and swim, run and crawl, buzz and chirp, gnaw and carry. However, all this is not done aimlessly, but mainly with a certain intention, according to the innate program embedded in their body and the acquired life experience. For the perception of the surrounding world, orientation in it, the implementation of all expedient actions and life processes, animals are endowed with very complex systems, primarily nervous and sensory.

What do the nervous systems of vertebrates and invertebrates have in common?

The nervous system is a complex complex of structures and organs, consisting of nervous tissue, where the central section is the brain. The main structural and functional unit of the nervous system is a nerve cell with processes (in Greek, a nerve cell is a neuron).

The nervous system and the brain of insects provide: perception with the help of the senses of external and internal irritation (irritability, sensitivity); instant processing by the system of analyzers of incoming signals, preparation and implementation of an adequate response; storage in memory in an encoded form of hereditary and acquired information, as well as its instantaneous retrieval as needed; management of all organs and systems of the body for its functioning as a whole, balancing it with the environment; implementation of mental processes and higher nervous activity, expedient behavior.

The organization of the nervous system and brain of vertebrates and invertebrates is so different that at first glance it seems impossible to compare them. And at the same time, for the most diverse types of the nervous system, belonging, it would seem, to both completely “simple” and “complex” organisms, the same functions are characteristic.

The very tiny brain of a fly, bee, butterfly or other insect allows it to see and hear, touch and taste, move with great accuracy, moreover, fly using an internal “map” over considerable distances, communicate with each other and even own its own "language", to learn and apply logical thinking in non-standard situations. So, the brain of an ant is much smaller than a pinhead, but this insect has long been considered a "sage". When compared not only with his microscopic brain, but also with the incomprehensible capabilities of a single nerve cell, a person should be ashamed of his most modern computers. And what can science say about this, for example, neurobiology, which studies the processes of birth, life and death of the brain? Was she able to unravel the mystery of the vital activity of the brain - this most complex and mysterious of the phenomena known to people?

The first neurobiological experience belongs to the ancient Roman physician Galen. Having cut the nerve fibers in a pig, with the help of which the brain controlled the muscles of the larynx, he deprived the animal of its voice - it immediately became numb. It was a millennium ago. But how far has science gone since then in its knowledge of the principle of the brain? It turns out that despite the enormous work of scientists, the principle of operation of even one nerve cell, the so-called "brick" from which the brain is built, is still not known to man. Neuroscientists understand a lot about how a neuron "eats" and "drinks"; how it receives the energy necessary for its life activity, digesting the necessary substances extracted from the environment in “biological boilers”; how then this neuron sends to its neighbors a wide variety of information in the form of signals, encrypted either in a certain series of electrical impulses, or in various combinations of chemicals. And then what? Here a nerve cell received a specific signal, and in its depths a unique activity began in collaboration with other cells that form the animal's brain. There is a memorization of the incoming information, the extraction of the necessary information from the memory, decision-making, giving orders to the muscles and various organs, etc. How is everything going? Scientists don't know for sure yet. Well, since it is not clear how individual nerve cells and their complexes operate, the principle of operation of the whole brain, even as small as that of an insect, is not clear either.

The work of the sense organs and living "devices"

The vital activity of insects is accompanied by the processing of sound, olfactory, visual and other sensory information - spatial, geometric, quantitative. One of the many mysterious and interesting features of insects is their ability to accurately assess the situation using their own "instruments". Our knowledge of these devices is limited, although they are widely used in nature. These are determinants of various physical fields, which allow predicting earthquakes, volcanic eruptions, floods, weather changes. This is a sense of time, counted by the internal biological clock, and a sense of speed, and the ability to navigate and navigate, and much more.

The property of any organism (microorganisms, plants, fungi and animals) to perceive stimuli emanating from the external environment and from their own organs and tissues is called sensitivity. In insects, as in other animals with a specialized nervous system, there are nerve cells with a high selective capacity for various stimuli - receptors. They can be tactile (responsive to touch), temperature, light, chemical, vibrational, muscular-articular, etc. Thanks to their receptors, insects capture the whole variety of environmental factors - various vibrations (a wide range of sounds, radiation energy in the form of light and heat), mechanical pressure (for example, gravity) and other factors. Receptor cells are located in tissues either singly or assembled into systems with the formation of specialized sensory organs - sense organs.

All insects perfectly "understand" the indications of their sense organs. Some of them, like the organs of vision, hearing, smell, are remote and are able to perceive irritation at a distance. Others, like the organs of taste and touch, are contact and respond to exposure through direct contact.

Insects in the mass are endowed with excellent vision. Their complex compound eyes, to which simple eyes are sometimes added, serve to recognize various objects. Some insects are provided with color vision, suitable night vision devices. Interestingly, the eyes of insects are the only organ that other animals have the likeness of. At the same time, the organs of hearing, smell, taste and touch do not have such a similarity, but, nevertheless, insects perfectly perceive smells and sounds, navigate in space, capture and emit ultrasonic waves. Delicate sense of smell and taste allow them to find food. A variety of glands of insects secrete substances to attract brothers, sexual partners, scare away rivals and enemies, and a highly sensitive sense of smell is able to pick up the smell of these substances even for several kilometers.

Many in their ideas associate the sense organs of insects with the head. But it turns out that the structures responsible for collecting information about the environment are found in insects in various parts of the body. They can determine the temperature of objects and taste food with their feet, detect the presence of light with their backs, hear with their knees, whiskers, tail appendages, body hairs, etc.

The sense organs of insects are part of sensory systems - analyzers that penetrate the network of almost the entire organism. They receive many different external and internal signals from the receptors of their sense organs, analyze them, form and transmit "instructions" to various organs for the implementation of appropriate actions. The sense organs mainly make up the receptor section, which is located on the periphery (ends) of the analyzers. And the conductive department is formed by central neurons and pathways from receptors. The brain has certain areas for processing information coming from the senses. They constitute the central, “brain”, part of the analyzer. Thanks to such a complex and expedient system, for example, a visual analyzer, an accurate calculation and control of the organs of movement of an insect is carried out.

Extensive knowledge has been accumulated about the amazing capabilities of the sensory systems of insects, but the volume of the book allows me to list only a few of them.

organs of vision

The eyes and the entire complex visual system are an amazing gift, thanks to which animals are able to receive basic information about the world around them, quickly recognize various objects and evaluate the situation that has arisen. Vision is necessary for insects when searching for food to avoid predators, to explore objects of interest or environment, to interact with other individuals in reproductive and social behavior, etc.

Insects are equipped with a variety of eyes. They can be complex, simple or additional eyes, as well as larval. The most complex are compound eyes, which consist of a large number of ommatidia that form hexagonal facets on the surface of the eye. Ommatidium is essentially a tiny visual apparatus equipped with a miniature lens, a light guide system and photosensitive elements. Each facet perceives only a small part of the object, and together they provide a mosaic image of the entire object. Compound eyes, characteristic of most adult insects, are located on the sides of the head. In some insects, such as the hunting dragonfly, which quickly reacts to the movement of prey, the eyes occupy half of the head. Each of her eyes is built from 28,000 facets. For comparison, butterflies have 17,000 of them, and houseflies have 4,000. Eyes on the head of insects can be two or three on the forehead or crown, and less often on its sides. Larval ocelli in beetles, butterflies, hymenoptera in adulthood are replaced by complex ones.

It is curious that insects cannot close their eyes during rest and therefore sleep with their eyes open.

It is the eyes that contribute to the quick reaction of an insect hunter, such as a praying mantis. By the way, this is the only insect that can turn around and look behind itself. Large eyes provide the praying mantis with binocular vision and allow you to accurately calculate the distance to the object of their attention. This ability, combined with the quick forward movement of the front legs towards the prey, make the mantid an excellent hunter.

And in yellow-footed beetles, running on the water, the eyes allow you to simultaneously see the prey both on the surface of the water and under it. To do this, the visual analyzers of the beetle have the ability to correct for the refractive index of water.

The perception and analysis of visual stimuli is carried out by a complex system - the visual analyzer. For many insects, this is one of the main analyzers. Here, the primary sensitive cell is the photoreceptor. And the pathways (optic nerve) and other nerve cells located at different levels of the nervous system are connected with it. When perceiving light information, the sequence of events is as follows. The received signals (light quanta) are instantly encoded in the form of impulses and transmitted along the conducting paths to the central nervous system - to the "brain" center of the analyzer. There, these signals are immediately decoded (decoded) into the corresponding visual perception. For its recognition, standards of visual images and other necessary information are retrieved from memory. And then a command is sent to various organs for an adequate response of the individual to a change in the situation.

Where are the "ears" of insects located?

Most animals and humans hear with their ears, where sounds cause the eardrum to vibrate - strong or weak, slow or fast. Any change in vibration informs the body about the nature of the sound being heard. How do insects hear? In many cases, they are also peculiar “ears”, but in insects they are in places unusual for us: on the mustache - for example, in male mosquitoes, ants, butterflies; on the tail appendages - in the American cockroach. Crickets and grasshoppers hear with the shins of their front legs, and locusts hear with their stomachs. Some insects do not have "ears", that is, they do not have special organs of hearing. But they are able to perceive various fluctuations in the air environment, including sound vibrations and ultrasonic waves that are inaccessible to our ear. The sensitive organs of such insects are thin hairs or the smallest sensitive sticks. They are located in large numbers on different parts of the body and are associated with nerve cells. So, in hairy caterpillars, the “ears” are hairs, and in naked caterpillars, the entire skin of the body.

A sound wave is formed by alternating rarefaction and condensation of air, propagating in all directions from the sound source - any oscillating body. Sound waves are perceived and processed by the auditory analyzer - the most complex system of mechanical, receptor and nervous structures. These vibrations are converted by auditory receptors into nerve impulses that are transmitted along the auditory nerve to the central part of the analyzer. The result is the perception of sound and the analysis of its strength, height and character.

The auditory system of insects ensures their selective response to relatively high-frequency vibrations - they perceive the slightest tremors of the surface, air or water. For example, buzzing insects produce sound waves through rapid wing beats. Such a vibration of the air environment, for example, the squeak of mosquitoes, males perceive with their sensitive organs located on the antennae. Thus, they catch the air waves that accompany the flight of other mosquitoes and adequately respond to the received sound information. The auditory systems of insects are “tuned” to perceive relatively weak sounds, so loud sounds have a negative effect on them. For example, bumblebees, bees, flies of some species cannot rise into the air when they sound.

The varied but well-defined signal calls made by male crickets of each species play an important role in their reproductive behavior in courting and attracting females. The cricket is provided with a wonderful tool for communicating with a friend. When creating a gentle trill, he rubs the sharp side of one elytra against the surface of another. And for the perception of sound, the male and female have a particularly sensitive thin cuticular membrane, which plays the role of the eardrum. An interesting experiment was made when a chirring male was placed in front of a microphone, and a female was placed in another room near the telephone. When the microphone was turned on, the female, having heard the species-typical chirping of the male, rushed to the source of the sound - the telephone.

Organs for capturing and emitting ultrasonic waves

Moths are equipped with a device for detecting bats, which use ultrasonic waves for orientation and hunting. Predators perceive signals with a frequency of up to 100,000 hertz, and night butterflies and lacewings, which they hunt, up to 240,000 hertz. In the chest, for example, of the moth butterflies, there are special organs for acoustic analysis of ultrasonic signals. They make it possible to capture the ultrasonic pulses of hunting kozhans at a distance of up to 30 m. When a butterfly perceives a signal from a predator locator, protective behavioral actions are activated. Hearing the ultrasonic calls of a night mouse at a relatively large distance, the butterfly abruptly changes the direction of flight, using a deceptive maneuver - "diving". At the same time, she begins to perform aerobatics - spirals and "dead loops" to get away from the chase. And if the predator is at a distance of less than 6 m, the butterfly folds its wings and falls to the ground. And the bat does not detect a motionless insect.

But the relationship between moths and bats has recently been found to be even more complex. So, butterflies of some species, having detected the signals of a bat, themselves begin to emit ultrasonic impulses in the form of clicks. Moreover, these impulses act on the predator in such a way that, as if frightened, it flies away. There is only speculation as to what causes bats to stop chasing the butterfly and "run away from the battlefield". Probably, ultrasonic clicks are adaptive signals of insects, similar to those sent by the bat itself, only much stronger. Expecting to hear a faint reflected sound from his own signal, the pursuer hears a deafening roar - as if a supersonic aircraft breaks the sound barrier.

This begs the question why a bat is stunned not by its own ultrasonic signals, but by butterflies. It turns out that the bat is well protected from its own scream-impulse sent by the locator. Otherwise, such a powerful impulse, which is 2,000 times stronger than the received reflected sounds, can deafen the mouse. To prevent this from happening, her body manufactures and purposefully uses a special stirrup. Before sending an ultrasonic pulse, a special muscle pulls the stirrup away from the window of the cochlea of the inner ear - the vibrations are mechanically interrupted. Essentially, the stirrup also makes a click, but not a sound, but an anti-sound one. After a signal-cry, it immediately returns to its place so that the ear is ready to receive the reflected signal. It is difficult to imagine with what speed the muscle can act, turning off the hearing of the mouse at the moment of the sent impulse-scream. During the pursuit of prey - this is 200-250 impulses per second!

And the butterfly clicks, which are dangerous for a bat, are heard exactly at the moment when the hunter turns on his ear to perceive his echo. So, in order to make a stunned predator frightened away, the night butterfly sends signals that are extremely matched to its locator. To do this, the insect's body is programmed to receive the pulse frequency of the approaching hunter and sends a response signal exactly in unison with it.

This relationship between moths and bats raises many questions. How did insects get the ability to perceive the ultrasonic signals of bats and instantly understand the danger they carry? How could butterflies gradually develop an ultrasonic device with perfectly matched protective characteristics through the process of selection and improvement? The perception of ultrasonic signals of bats is also not easy to figure out. The fact is that they recognize their echo among millions of voices and other sounds. And no cries-signals of fellow tribesmen, no ultrasonic signals emitted with the help of equipment, prevent bats from hunting. Only the signals of the butterfly, even artificially reproduced, make the mouse fly away.

Living beings present new and new riddles, causing admiration for the perfection and expediency of the structure of their body.

The praying mantis, like the butterfly, along with excellent eyesight, is also given special hearing organs to avoid meeting with bats. These hearing organs that perceive ultrasound are located on the chest between the legs. And for some species of praying mantis, in addition to the ultrasonic organ of hearing, the presence of a second ear is characteristic, which perceives much lower frequencies. Its function is not yet known.

chemical feeling

Animals are endowed with a general chemical sensitivity, which is provided by various sensory organs. In the chemical sense of insects, the sense of smell plays the most significant role. And termites and ants, according to scientists, are given a three-dimensional sense of smell. What it is - it is difficult for us to imagine. The olfactory organs of an insect react to the presence of even very small concentrations of a substance, sometimes very remote from the source. Thanks to the sense of smell, the insect finds prey and food, navigates the terrain, learns about the approach of the enemy, and carries out biocommunication, where the specific “language” is the exchange of chemical information using pheromones.

Pheromones are the most complex compounds secreted for communication purposes by some individuals in order to transfer information to other individuals. Such information is encoded in specific chemicals, depending on the type of living being and even on its belonging to a particular family. Perception with the help of the olfactory system and decoding of the "message" causes a certain form of behavior or physiological process in the recipients. To date, a significant group of insect pheromones is known. Some of them are designed to attract individuals of the opposite sex, others, trace ones, indicate the path to a house or a food source, others serve as an alarm signal, fourth ones regulate certain physiological processes, etc.

Truly unique must be the "chemical production" in the body of insects in order to release in the right amount and at a certain moment the whole range of pheromones they need. Today, more than a hundred of these substances of the most complex chemical composition are known, but no more than a dozen of them have been artificially reproduced. Indeed, to obtain them, advanced technologies and equipment are required, so for now one can only be surprised at such an arrangement of the body of these miniature invertebrate creatures.

Beetles are provided mainly with olfactory type antennae. They allow you to capture not only the smell of a substance and the direction of its distribution, but even "feel" the shape of an odorous object. An example of a great sense of smell is gravedigger beetles, engaged in cleaning the earth from carrion. They are able to smell hundreds of meters from her and gather in a large group. And the ladybug, with the help of smell, finds colonies of aphids in order to leave masonry there. After all, not only she herself feeds on aphids, but also her larvae.

Not only adult insects, but also their larvae are often endowed with an excellent sense of smell. Thus, the larvae of the cockchafer are able to move to the roots of plants (pine, wheat), guided by a slightly elevated concentration of carbon dioxide. In experiments, the larvae immediately go to the soil area, where they introduced a small amount of a substance that forms carbon dioxide.

The sensitivity of the olfactory organ, for example, of the Saturnian butterfly, the male of which is able to capture the smell of a female of its own species at a distance of 12 km, seems incomprehensible. When comparing this distance with the amount of pheromone secreted by the female, a result that surprised scientists was obtained. Thanks to his antennae, the male unmistakably searches among many odorous substances for one single molecule of the hereditarily known substance per 1 m3 of air!

Some Hymenoptera are given such a keen sense of smell that it is not inferior to the well-known instinct of a dog. So, female riders, when running along a tree trunk or stump, vigorously move their antennae. With them, they “sniff out” the larvae of the horntail or lumberjack beetle, located in the wood at a distance of 2-2.5 cm from the surface.

Thanks to the unique sensitivity of the antennae, the tiny helis rider, by touching the cocoons of spiders with just one touch, determines what is in them - whether the testicles are underdeveloped, inactive spiders have already left them, or the testicles of other riders of their species. How Helis makes such an accurate analysis is not yet known. Most likely, he feels the subtlest specific smell, but it may be that when tapping his antennae, the rider picks up some kind of reflected sound.

The perception and analysis of chemical stimuli acting on the olfactory organs of insects is carried out by a multifunctional system - an olfactory analyzer. It, like all other analyzers, consists of a perceiving, conducting and central departments. Olfactory receptors (chemoreceptors) perceive molecules of odorous substances, and impulses signaling a certain smell are sent along the nerve fibers to the brain for analysis. There is an instant development of the response of the body.

Speaking about the sense of smell of insects, one cannot but say about the smell. Science does not yet have a clear understanding of what smell is, and there are many theories regarding this natural phenomenon. According to one of them, the analyzed molecules of a substance represent a “key”. And the “lock” is the receptors of the olfactory organs included in the odor analyzers. If the configuration of the molecule approaches the "lock" of a certain receptor, then the analyzer will receive a signal from it, decipher it and transmit information about the smell to the animal's brain. According to another theory, the smell is determined by the chemical properties of the molecules and the distribution of electrical charges. The newest theory, which has won many supporters, sees the main cause of smell in the vibrational properties of molecules and their constituents. Any fragrance is associated with certain frequencies (wave numbers) of the infrared range. For example, onion soup thioalcohol and decaborane are chemically completely different. But they have the same frequency and the same smell. At the same time, there are chemically similar substances that are characterized by different frequencies and smell differently. If this theory is correct, then both aromatic substances and thousands of types of cells that perceive smell can be assessed by infrared frequencies.

"Radar installation" of insects

Insects are endowed with excellent organs of smell and touch - antennae (antennae or ties). They are very mobile and easily controlled: an insect can breed them, bring them together, rotate each one individually on its own axis or together on a common one. In this case, they both outwardly resemble and in essence are a “radar installation”. The nerve-sensitive element of the antennae are the sensilla. From them, an impulse at a speed of 5 m per second is transmitted to the "brain" center of the analyzer to recognize the object of irritation. And then the signal of response to the received information instantly goes to the muscle or other organ.

In most insects, on the second segment of the antennae, there is a Johnston organ - a universal device, the purpose of which has not yet been fully elucidated. It is believed that it perceives movements and tremors of air and water, contacts with solid objects. Locusts and grasshoppers are endowed with surprisingly high sensitivity to mechanical vibrations, which are able to register any vibrations with an amplitude equal to half the diameter of a hydrogen atom!

Beetles also have a Johnston organ on the second segment of the antennae. And if a beetle running on the surface of the water is damaged or removed, then it will stumble upon any obstacles. With the help of this organ, the beetle is able to capture reflected waves coming from the coast or obstacles. He feels water waves with a height of 0.000000004 mm, that is, the Johnston organ performs the task of an echo sounder or radar.

Ants are distinguished not only by a well-organized brain, but also by an equally perfect bodily organization. The antennae are of paramount importance for these insects; some serve as an excellent organ of smell, touch, knowledge of the environment, and mutual explanations. Ants deprived of antennae lose the ability to find a way, nearby food, and distinguish enemies from friends. With the help of antennas, insects are able to "talk" among themselves. Ants transmit important information by touching each other's antennae with their antennae. In one of the behavioral episodes, two ants found prey in the form of larvae of different sizes. After "negotiations" with their brothers with the help of antennas, they went to the place of discovery together with mobilized assistants. At the same time, the more successful ant, which managed to transmit information about the larger prey it found with the help of antennae, mobilized a much larger group of worker ants behind it.

Interestingly, ants are one of the cleanest creatures. After each meal and sleep, their entire body and especially the antennae are thoroughly cleaned.

Taste sensations

A person clearly defines the smell and taste of a substance, while in insects, taste and olfactory sensations are often not separated. They act as a single chemical feeling (perception).

Insects with taste sensations prefer one or another substance depending on the nutrition characteristic of a given species. At the same time, they are able to distinguish between sweet, salty, bitter and sour. For contact with the food consumed, the taste organs can be located on various parts of the body of insects - on the antennae, proboscis and legs. With their help, insects receive basic chemical information about the environment. For example, a fly, only by touching its paws to an object of interest to it, almost immediately finds out what is under its feet - drink, food or something inedible. That is, it is capable of performing instant contact analysis of a chemical with its feet.

Taste is the sensation that occurs when a solution of chemicals is exposed to the receptors (chemoreceptors) of the insect's taste organ. Receptor taste cells are the peripheral part of the complex system of the taste analyzer. They perceive chemical stimuli, and here the primary coding of taste signals occurs. Analyzers immediately transmit volleys of chemoelectric impulses along thin nerve fibers to their "brain" center. Each such pulse lasts less than a thousandth of a second. And then the central structures of the analyzer instantly determine the taste sensations.

Attempts are continuing to understand not only the question of what a smell is, but also to create a unified theory of "sweetness". So far, this has not been successful - maybe you, the biologists of the 21st century, will succeed. The problem is that completely different chemicals - both organic and inorganic - can create relatively the same taste sensations of sweetness.

sense organs

The study of the sense of touch of insects is perhaps the greatest difficulty. How do these creatures chained in a chitinous shell touch the world? So, thanks to skin receptors, we are able to perceive various tactile sensations - some receptors register pressure, others temperature, etc. Touching an object, we can conclude that it is cold or warm, hard or soft, smooth or rough. Insects also have analyzers that determine temperature, pressure, etc., but much in the mechanisms of their action remains unknown.

The sense of touch is one of the most important senses for the flight safety of many flying insects, to sense air currents. For example, in dipterans, the entire body is covered with sensilla, which perform tactile functions. There are especially many of them on the halteres in order to perceive air pressure and stabilize the flight.

Thanks to the sense of touch, the fly is not so easy to swat. Her vision allows her to notice a threatening object only at a distance of 40 - 70 cm. But the fly is able to respond to a dangerous movement of the hand, which caused even a small movement of air, and instantly take off. This common housefly once again confirms that there is nothing simple in the living world - all creatures, young and old, are provided with excellent sensory systems for active life and their own protection.

Insect receptors that register pressure can be in the form of pimples and bristles. They are used by insects for various purposes, including orientation in space - in the direction of gravity. For example, a fly larva always moves clearly upwards before pupation, that is, against gravity. After all, she needs to crawl out of the liquid food mass, and there are no landmarks there, except for the attraction of the Earth. Even after getting out of the chrysalis, the fly tends to crawl up for some time until it dries out in order to fly.

Many insects have a well-developed sense of gravity. For example, ants are able to estimate a surface slope of 20. And a rove beetle that digs vertical burrows can estimate a deviation from the vertical of 10.

Living "forecasters"

Many insects are endowed with an excellent ability to anticipate weather changes and make long-term forecasts. However, this is typical for all living things - be it a plant, a microorganism, an invertebrate or a vertebrate. Such abilities ensure normal life activity in their intended habitat. There are also rarely observed natural phenomena - droughts, floods, cold snaps. And then, in order to survive, living beings need to mobilize additional protective equipment in advance. In both cases, they use their internal "weather stations".

Constantly and carefully observing the behavior of various living beings, one can learn not only about weather changes, but even about upcoming natural disasters. After all, more than 600 species of animals and 400 species of plants, so far known to scientists, can play a kind of role as barometers, indicators of humidity and temperature, predictors of both thunderstorms, storms, tornadoes, floods, and beautiful cloudless weather. Moreover, there are live "weather forecasters" everywhere, wherever you are - by the reservoir, in the meadow, in the forest. For example, before the rain, even with a clear sky, the green grasshoppers stop chirping, the ants begin to tightly close the entrances to the anthill, and the bees stop flying for nectar, sit in the hive and buzz. In an effort to hide from the impending bad weather, flies and wasps fly into the windows of houses.

Observations of poisonous ants living in the foothills of Tibet have revealed their excellent ability to make more distant forecasts. Before the onset of a period of heavy rains, the ants move to another place with dry hard ground, and before the onset of a drought, the ants fill the dark, moist depressions. Winged ants are able to feel the approach of a storm in 2-3 days. Large individuals begin to rush along the ground, while small ones swarm at a low altitude. And the more active these processes are, the stronger bad weather is expected. It was found that during the year the ants correctly identified 22 weather changes, and were mistaken only in two cases. This amounted to 9%, which looks quite good compared to the average error of weather stations of 20%.

The purposeful actions of insects often depend on long-term forecasts, and this can be of great service to people. An experienced beekeeper is provided with a fairly reliable forecast by bees. For the winter, they close up the notch in the hive with wax. By the opening for ventilation of the hive, one can judge the upcoming winter. If the bees leave a large hole, the winter will be warm, and if a small one, expect severe frosts. It is also known that if the bees start to fly out of the hives early, an early warm spring can be expected. The same ants, if the winter is not expected to be severe, remain to live near the surface of the soil, and before a cold winter, they settle down deeper in the ground and build a higher anthill.

In addition to the macroclimate for insects, the microclimate of their habitat is also important. For example, bees do not allow overheating in the hives and, having received a signal from their living "devices" about the temperature exceeding, they begin to ventilate the room. Part of the worker bees is organized at different heights throughout the hive and sets the air in motion with quick wing beats. A strong air current is formed, and the hive is cooled. Ventilation is a long process, and when one batch of bees gets tired, it is the turn of another, and in strict order.

The behavior of not only adult insects, but also their larvae, depends on the readings of living "instruments". For example, cicada larvae that develop in the ground come to the surface only when the weather is good. But how do you know what the weather is like at the top? To determine this, they create special earthen cones with large holes above their underground shelters - a kind of meteorological structures. In them, cicadas assess temperature and humidity through a thin layer of soil. And if the weather conditions are unfavorable, the larvae return to the mink.

The phenomenon of forecasting rainstorms and floods

Observing the behavior of termites and ants in critical situations can help people predict heavy rainfall and flooding. One of the naturalists described the case when, before the flood, an Indian tribe living in the jungles of Brazil hurriedly left their settlement. And the ants "told" the Indians about the approaching disaster. Before the flood, these social insects become very agitated and urgently leave the habitable place along with the pupae and food supplies. They go to places where water does not reach. The local population hardly understood the origins of such an amazing sensitivity of ants, but, obeying their knowledge, people left the trouble after the little weather forecasters.

They are excellent at predicting floods and termites. Before it starts, they leave their homes with the whole colony and rush to the nearest trees. Anticipating the magnitude of the disaster, they rise to exactly the height that will be higher than the expected flood. There they wait until the muddy streams of water subside, which rush at such a speed that trees sometimes fall under their pressure.

A huge number of weather stations monitor the weather. They are located on land, including in the mountains, on specially equipped scientific vessels, satellites and space stations. Meteorologists are equipped with modern instruments, devices and computers. In fact, they do not make a weather forecast, but a calculation, a calculation of weather changes. And the insects in the above examples of the real predict the weather using innate abilities and special living “devices” built into their bodies. Moreover, weather forecasting ants determine not only the time of the approach of the flood, but also estimate its scope. After all, for a new refuge, they occupied only safe places. Scientists have not yet been able to explain this phenomenon. Termites presented an even greater mystery. The fact is that they were never located on those trees that, during a flood, turned out to be demolished by stormy streams. In a similar way, according to the observation of ethologists, the starlings behaved, which in the spring did not occupy the birdhouses dangerous for the settlement. Subsequently, they were really torn off by a hurricane wind. But here we are talking about a relatively large animal. The bird, perhaps by swinging the birdhouse or by other signs, assesses the unreliability of its fastening. But how and with the help of what devices can such forecasts be made by very small, but very "wise" animals? Man is not only not yet able to create anything like this, but he cannot answer. These tasks are for future biologists!

Nervous system. In the structure of the central nervous system in insects, the same modifications are found as in crustaceans. Along with cases of its strong division (supraglottic, subpharyngeal, three thoracic and eight abdominal nodes) and a clearly paired structure, which occurs in primitive insects, there are cases of extreme concentration of the nervous system; the entire ventral chain can be reduced to a continuous ganglionic mass, which is especially common in larvae and larval adults in the absence of limbs and weak dissection of the body.

In the supraoesophageal ganglion, attention is drawn to the development of the internal structure of the protocerebral part of the brain, in particular the mushroom bodies. It has been noted that the structure of the mushroom bodies, which occupy a place in the upper part of the brain, forming here one or two pairs of tubercles on the sides of the midline, is closely related to the development of the insect instinct.

1 - optic lobes, 2 - frontal lobe with mushroom body, 3 - protocerebral lobe, 4 - deutocerebral lobe with antennal nerve, 5 - nerve of the paired simple eye, 6 - frontal node with an unpaired sympathetic nerve (nervus recurrens) extending back from it, 7 - peripharyngeal connective

sense organs. The sense organs of insects are differentiated and well developed. The organs of touch and smell predominate in their significance. The organs of touch are externally represented by bristles. The olfactory organs also have the shape of a typical seta, which, changing, can turn into detached thin-walled protrusions and non-segmented finger-like protrusions and thin-walled flat areas of the integument. The most important location of the endings of the olfactory nerves are the antennae.

Such, for example, is the role of antennae as organs of smell in flies and lepidoptera, which distinguish even faint odors at great distances. The sense of smell of bees is better studied; it turned out that their ability to perceive smells is close to ours: those smells that we perceive are also perceived by bees, those smells that we mix are mixed by bees; the organs of smell are also concentrated mainly on the antennae. Tastessweet, bitter, sour and salty insects also differ; taste organs are located on the tentacles of the mouth parts, on the legs; the sharpness of the taste sensation in different organs of the same insect may be different; it is much higher than in humans. The compound eyes of an insect perceive the movement of objects, and in some cases they can also perceive the shape of objects; higher hymenoptera (bees) can also perceive colors, including those that are not perceived by humans (“ultraviolet”); however, color vision is not as diverse as that of a person: for example, a bee in the left part of the spectrum feels yellow, while other colors feel like shades of yellow; the right blue-violet part of the spectrum is also perceived by bees as a single color. The visual acuity of bees is much lower than that of humans.

. On the right, the exterior building; left - frontal section, internal structure: 1 - mushroom (stalked) body, 2 - central body, 3 - optic lobe, 4 - olfactory deutocerebral lobe with two antennal nerves, 5 - subpharyngeal ganglion with nerves of three jaws

In some orders, such as in the order of Orthoptera (Orthoptera), which include grasshoppers, crickets and locusts, the so-called tympanal organs are common. to assume auditory organs in the tympanal organs. Tympanal organs in grasshoppers and crickets are located on the lower leg under the knee joint, while in locusts and cicadas on the sides of the first abdominal segment, they are externally represented by a depression, sometimes surrounded by a fold of cover and with a thin stretched membrane at the bottom; on the inner surface of the membrane or in its immediate vicinity there is a nerve ending of a peculiar structure.

Olfactory organs

They are special olfactory sensilla, usually of a conical or placoid (immersed) type. Most of them are located on the antennae. (a photo) Sometimes trichoid sensilla are also found among them. Very abundant olfactory hairs cover bees - an insect that is very sensitive to odors. There are about 6000 sensilla on each antenna of a worker bee. And some insects have even more: for example, male butterflies Antheraea polirhemus have up to 60,000 of them.

The olfactory sensilla can be collected in pits, as, for example, in flies on the third segment of the antennae. At the base of these hairs are groups of nerve cells (neurons) of up to 40-60 pieces. The surface of the sensilla has many pores (10-20), through which the terminal parts of the processes of neurons come into contact with volatile substances, perceiving odors.

How do insects smell?

Food olfactory signals are recognized by insects very well. Contrary to popular belief, for them there are not only the concepts of "edible - not edible", but also more subtle sensations. Those species that feed on flower nectar distinguish the aromas of different flowers. Other herbivores use scent to identify specific types of non-flowering plants that are suitable for them as food. Thus, insects do not just accidentally find food, but purposefully go to it, sensing its smell in the air.

As a rule, it is not the smell "as a whole" that is attractive to them, but its individual components. So, scavenger beetles react to the content in the air of skatole, indole, ammonia and other volatile substances released during the decay of proteins. The dead-eater beetle senses “seductive” smells for itself at a distance of up to 90 cm. And mosquitoes, fleas and other blood-sucking insects feel an increased concentration of carbon dioxide and volatile components of human and animal sweat. No wonder they say that a clean person attracts mosquitoes less than someone who has not taken care of their hygiene. For the same reason, decoy traps that produce heat and carbon dioxide work well against midges.

Male insects usually have more olfactory receptors than females. But this is observed not at all in connection with their more active extraction of food, but because of gender characteristics. The fact is that with the help of sensilla, males smell the pheromones emitted by females, and thanks to this they look for a mate for copulation. Therefore, in order to participate in the "celebration of life" and leave their genetic mark in a number of generations, they must have a developed sense of smell.

Butterfly males feel sexual attractants of females for 3-6 km; interestingly, if the female is already fertilized, she ceases to secrete these substances and becomes "invisible" to males. feels the presence of a sexual attractant in the air with its content there of only 100 molecules per 1 m 3, and the male pear saturnia has the ability to smell the female as much as 10 km away. This is a record among insects for sensitivity to odors. (a photo)

In a colony of ants or termites, insects distinguish the smell of their relatives from different castes, identifying the so-called foragers (these are those family members who are responsible for feeding everyone else) and coming to them for food. Some insects also give off smells of anxiety, according to which the rest understand that they need to beware of something. In addition, all insects feel the "smell of death" emitted by dead relatives. And in bee hives, the queen bee emits an odor that inhibits the development of eggs in worker bees.

The sense of smell of insects not only helps them get food and communicate with each other; with its help, they recognize representatives of other species, determine the best places for masonry, etc.

organs of taste

As already mentioned, chemoreceptors, which give insects the ability to taste, are mainly located on their mouth organs. But their accumulations are also found on other parts of the body. For example, they are found on the front, and sometimes on the antennae or even on! The latter allows females to determine the suitability of a particular substrate for laying, "feeling" it with the back of their own.

The organs of taste are thick-walled taste sensilla, at the base of which lie from 3 to 5 (in rare cases up to 50) nerve cells that transmit the corresponding signals to the central nervous system. Their short processes (dendrites) go up to the top of the sensilla, where the nerve endings of the dendrites come into contact with food substrates through a special opening (pore). (a photo)

In some insects, the structure of the sensilla is somewhat more complicated than it seems at first. For example, in the fly Phormiaregina, there are only three neurons at the base of the taste hairs, but they all perform different functions. One is a mechanoreceptor, that is, it reacts to touch, the second determines the sweet taste, and the third - salty. When the "sugar" neuron is irritated, the proboscis reflex occurs in the insect, since the sweet substrate is attractive to it. If there is a salty taste, this causes the fly to lose interest in the intended food.

How do insects taste?

From taste sensilla, nervous excitation is transmitted to special centers of the brain, where the insect "realizes" the taste and reacts to it.

Taste reactions among representatives of the class are very diverse. They, like humans, distinguish four basic tastes - sour, sweet, bitter and salty. Moreover, the sensitivity of insects to these tastes is in fact the same as ours, and sometimes even higher. So, a person feels a sweet taste if the concentration of sugar in the solution is 0.02 mol / l. Bees feel it at a content of 0.06 mol/l, and the admiral butterfly Pyrameis atalanta at 0.01 mol/l.

Insects “accustomed” to sweet food should, at first glance, distinguish it better than anyone else, but this is often not the case. For example, lactose (milk sugar) is perceived by bees as tasteless compared to the sweet nectar they consume, and some caterpillars perceive it as a sweet substance after their usual "fresh" green vegetation.

Another feature of the taste of insects is that they are not lovers of salt. They respond positively to the food substrate only when the salt concentration in it is sufficiently low. By the way, not sodium ions, like a person, but potassium ions seem to be the saltiest insects.

A remarkable feature is that the representatives of Insecta, it turns out, taste distilled water, which for us has no taste. And some also show addiction to toxic compounds. Thus, the leaf beetle Chrysolina, feeding on St. John's wort plants (a photo) , has a special group of taste buds that are excited by the poisonous alkaloid hyperisin contained in its leaves.

The sense organs are mediators between the external environment and the body. By analogy with a person, the organs of touch, hearing, smell, taste and vision are distinguished. However, it is more correct to divide them into mechanical sense, hydrothermal sense and vision.
The basis of the sense organs is their nerve-sensitive formations - sensilla. Depending on the characteristics of exposure and perception of irritation, sensilla are arranged differently: some protrude above the skin surface in the form of a hair, bristle, cone or other formation, others are located in the skin itself.
The organs of mechanical sense include tactile receptors that perceive the concussion of the position of the body, its balance. They are scattered throughout the body in the form of simple sensilla with a sensitive hair. The change in the position of the hair is transmitted to the sensitive cell, where there is an excitation that enters the nerve center.
Hearing is developed in all insects. In orthoptera, song cicadas, and some bugs, auditory receptors are represented by tympanic organs. Locusts have such organs on the sides of the 1st abdominal segment, grasshoppers and crickets - on the lower legs of the front legs in the form of a pair of ovals tightened with a tympanic membrane or a pair of slits with hidden membranes. Insects perceive sounds from 8 (infrasound) to more than 40 thousand vibrations per second (ultrasound).
The organ of chemical sense serves to perceive smell and taste and is represented by chemoreceptors located on the antennae. The number of olfactory sensilla depends on the way of life of the species, methods and nature of obtaining food. The worker bee has about 6,000 lamellar sensilla on each antennae. Males usually have more sensilla, which is associated with an active search for females.
The sense of smell serves as an insect for searching for individuals of the opposite sex, recognizing individuals of their own species, for finding food, places for laying eggs. Many insects secrete attractive substances - sexual attractants, or epagons. Unfertilized females can attract males from a distance of 3-9 km, but a fertilized female is no longer interesting for males. Males are able to catch the sexual attractant at a great distance and at its negligible concentration, calculated by a few molecules per cubic meter of air.
Taste serves only to recognize food. Insects have four basic tastes: sweet, bitter, sour, and salty. Most sugars are recognized by insects even in small concentrations. Some butterflies distinguish a sugar solution with a concentration of 0.0027% from pure water. Ants well distinguish sugar from saccharin, bees - salt and its admixture to sugar in a concentration of 0.36%. A person does not feel this concentration.
Taste buds are located on the mouth parts, but can also be located on the paws of the legs (diurnal butterflies), when the plantar side of the paw touches the sugar solution, the hungry butterfly reacts by deploying the proboscis. The high development of the chemical sense in insects is used in the fight against them by methods of bait or repellent substances.
The hydrothermal sense is of great importance in the life of insects and, depending on the humidity and temperature of the environment, regulates their behavior.
Vision, together with the chemical sense, plays a leading role in the life of insects. The organs of vision are represented by simple and compound eyes. Compound or compound eyes are located on the sides of the head and can sometimes be very large (flies, dragonflies). Each compound eye is made up of many sensilla called ommatidia, their number reaches many hundreds and even thousands. With the help of compound eyes, insects distinguish between shape, movement, color and distance to an object, as well as polarized light. Many species are short-sighted and at a distance distinguish only movement. Most insects do not see red light, but they do see ultraviolet light. The range of visible light waves lies within 2,500-8,000 nm. The honey bee distinguishes polarized light emitted from the blue sky, which allows it to orient itself in the direction of flight.
The flight of insects to light is explained by light-compass movement. Light rays diverge radially, and when moving obliquely with respect to them, the angle of incidence will change. To maintain a fixed angle, the insect is forced to constantly change its path towards the light source. The movement follows a logarithmic spiral and eventually leads the insect to a light source.
Simple eyes, or ocelli, are located between the compound eyes on the forehead or crown. Their number ranges from 1 to 3, they are arranged in a triangle. In many insects, the ocelli have a regulatory effect on the compound eyes, ensuring stability of vision under conditions of fluctuating light intensity (in insects with incomplete metamorphosis).

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