What sense organs do insects have? The structure of the body of an insect - the sense organs and the nervous system of insects

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The sense organs are described separately from the structure, since not only nerve cells, but also derivatives of other tissues participate in their formation. However, they can be called part of it. They are elements of the peripheral nervous system, as they contain sensitive nerve endings.

Reception and receptors

Any sense organ consists of receptors - sensitive elements of a special structure that perceive a certain type of irritation. For example, the hairs on the body of an insect, which perform the function of touch, feel mechanical irritation, but do not perceive light, and so on.

In total, there are 4 types of receptors in the insect body.

Mechanoreceptors

: perceive mechanical vibrations. Such nerve endings underlie the organs of touch and hearing (sound is also a mechanical vibration of a certain frequency). Among the mechanoreceptors that form the sense of touch, there are several varieties. Some feel pressure, others feel vibration, others feel touch, and so on. In general, mechanoreceptors are quite diverse and "multifunctional".

thermoreceptors

structures that perceive temperature. They are located in the integument of insects and transmit information about its fluctuations. Moreover, when heated and cooled, they are excited different types thermoreceptors: cold and heat. Without temperature sensitivity, life and some insects would be impossible. For example, worker bees in a hive constantly monitor the temperature of the nest area where they develop and (Photo). They either warm them up or cool them down. The temperature is constantly maintained at 34.5-35.5 degrees, as they die if they deviate from this “norm”.

Chemoreceptors

- sensitive formations that are irritated by chemicals. An example is the organs of taste and. Despite the fact that insects are more primitive than many animals, they have found special chemoreceptors that no one else has. We are talking about internal chemoreceptors, which determine the constancy of the internal environment of the body: pH and so on. So far, these receptors are poorly understood.

Photoreceptors

- the basis of the organ of vision, nerve endings that perceive light waves.

In general, all receptors perform only one function - reception, that is, the perception of certain signals. These signals in the form of nervous excitation are fed to the nerve centers of the brain and where information is processed. As a result, the insect "decides" what to do in response to external stimuli.

organs of taste

. Sensitive chemoreceptors are found in most groups on the oral organs. However, in flies (Photo) , butterflies and bees, they are also located on the front legs (more precisely, on them). Folded-winged wasps are distinguished by the presence of taste organs on the segments of the antennae.

Insects are best at distinguishing sweet, they are also able to recognize sour, bitter and salty. Sensitivity to different tastes in different insects is not the same. For example, lactose is sweet to butterfly caterpillars, but tasteless to bees. But bees are very sensitive to salt.

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 is hard 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 home or 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 into the right amount and at some point the whole gamut of pheromones they need. Today, more than a hundred of these substances of the most complex nature are known. chemical composition, but no more than a dozen of them were artificially reproduced. Indeed, to obtain them, advanced technologies and equipment are required, so for now it remains only to 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. A ladybug using the sense of smell, it 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. Yes, maggots Maybug 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 determines by just touching the cocoons of spiders what is in them - whether they are underdeveloped testicles, inactive spiders that have already left them, or 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 - the 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, smell is determined chemical properties molecules and the distribution of electric 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 they smell different. 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 shackles). 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. Antennae are of paramount importance for these insects, some serve as an excellent organ of smell, touch, and knowledge. environment, 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 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 sensation 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 ordinary housefly once again confirms that there is nothing simple in the world of life - 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 for 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 rarely seen natural phenomena- droughts, floods, cold snaps. And then, in order to survive, living beings need to mobilize additional resources in advance. protective equipment. 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, ants move to another place with dry hard ground, and before the onset of a drought, ants fill 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 big hole- the winter will be warm, and if it is small, 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 soil surface, and before cold winter located 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 modern appliances, devices and computer technology. 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 magnitude. 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 (supraoesophageal, suboesophageal, 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 is 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 middle line, stands in close connection with 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. Flavorssweet, 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 in humans: for example, a bee in the left side of the spectrum feels yellow, other colors are 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 right - external structure; 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.

Type of nervous system in insects

The nervous system of insects processes signals from the environment into electrical impulses. Thanks to this, muscle movements and the functioning of organs are carried out. A particularly large number of nerve cells are located in the head. They form the brain, as well as the second nerve center located under the esophagus, the subesophageal ganglion. The three thoracic segments contain nerve nodes that control the movements of the legs and wings. Located in the back of the body, eight nerve nodes innervate their part of the body. Nerve nodes are connected to each other and to other nerve centers by nerve trunks. In this way, nervous system insects is built on the principle rope ladder. In many insects, the ganglions of the thoracic segments and the back of the body merge into larger ganglions.

How do insects breathe

Through a complex system of tubes, air spreads through the body of an insect. On the sides of the thoracic and abdominal segments, there is one respiratory opening each. Tracheas, airways, which branch intensively, depart from it. The thinnest tubes, thousands of times thinner than a human hair, entangle the surfaces of all insect organs. Large insects such as beetles and butterflies often breathe by tensing and relaxing the back of their body. In order to prevent moisture from leaving the respiratory tract, the insect closes the respiratory openings with the help of hairs; This also eliminates the possibility of foreign bodies getting into them. The tracheae are internally covered with a cuticle, which is renewed with each change of the membrane.

Do insects have ears?

"Drum" skin is present in the body of many insects. This "ear" is often susceptible not only to the sounds that people hear, but also to ultrasound. However, it is located not on the head of the insect, but on the most different parts its bodies: in cicadas and some night butterflies, on the back of the body, in other butterflies, in the last thoracic segment. In grasshoppers, the "ears" are located under the knees on the front legs. Many insects use their ears to communicate: female grasshoppers and crickets find singing males. But insects have other senses that perceive noise. Male mosquitoes use an organ located in their antennae to detect the sounds that females of their species make when flying, and thus find a partner. Cockroaches have long sensitive hairs on the back of their bodies that can perceive sound.

Why do insects have antennae?

The sense organs on the antennae of insects tell them not only the state of the environment, they help to communicate with relatives, find appropriate place habitat for themselves and offspring, as well as food. Females of many insects attract males with the help of smells. Males of the lesser nocturnal peacock eye can smell a female at a distance of several kilometers. Ants recognize by the smell of females from their anthill. Some species of ants mark their way from the nest to the source of food thanks to odorous substances that are secreted from special glands. With the help of antennae, ants and termites smell the smell left by their relatives. If both antennae capture the smell to the same extent, then the insect is on the right way. Attractant substances that are released by female butterflies ready for mating are usually carried by the wind.

Insects like other multicellular organisms, have many different receptors, or sensilla, that are sensitive to certain stimuli. Insect receptors are very diverse. Insects have mechanoreceptors (hearing receptors, proprioceptors), photoreceptors, thermoreceptors, chemoreceptors. With their help, insects capture the energy of radiation in the form of heat and light, mechanical vibrations, including a wide range of sounds, mechanical pressure, gravity, the concentration of water vapor and volatile substances in the air, as well as many other factors. Insects have developed sense smell and taste. Mechanoreceptors are trichoid sensilla that perceive tactile stimuli. Some sensilla can detect the slightest fluctuations in the air around the insect, while others signal the position of body parts relative to each other. Air receptors perceive the speed and direction of air currents in the vicinity of the insect and regulate the speed of flight.

Vision

Vision plays a big role in the life of most insects. They have three types of organs of vision - compound eyes, lateral (stemmas) and dorsal (ocelli) eyes. Diurnal and flying forms usually have 2 compound eyes and 3 ocelli. Stemma are found in insect larvae with complete metamorphosis. They are located on the sides of the head in the amount of 1-30 on each side. Dorsal ocelli (ocelli) are found together with compound eyes and function as additional organs of vision. Ocellia are noted in adults of most insects (absent in many butterflies and Diptera, in worker ants and blind forms) and in some larvae (stoneflies, mayflies, dragonflies). As a rule, they are present only in well-flying insects. Usually there are 3 dorsal ocelli located in the form of a triangle in the fronto-parietal region of the head. Their main function is probably to evaluate the illumination and its changes. It is assumed that they also take part in the visual orientation of insects and phototaxis reactions.

Features of vision of insects are due to the faceted structure of the eyes, which consist of a large number of ommatidia. The largest number ommatidia were found in butterflies (12-17 thousand) and dragonflies (10-28 thousand). The light-sensitive unit of the ommatidium is the retinal (visual) cell. The photoreception of insects is based on the transformation of the visual pigment rhodopsin under the influence of a light quantum into the metarhodopsin isomer. Its reverse restoration makes it possible to repeatedly repeat elementary visual acts. Usually, 2-3 visual pigments are found in photoreceptors, differing in their spectral sensitivity. The data set of visual pigments also determines the color vision features of insects. Visual images in compound eyes are formed from many point images created by individual ommatidia. Compound eyes lack the ability to accommodate and cannot adapt to vision at different distances. Therefore, insects can be called "extremely short-sighted." Insects are characterized by an inversely proportional relationship between the distance to the object under consideration and the number of details distinguishable by their eye: the closer the object is, the more details they see. Insects are able to evaluate the shape of objects, but at short distances from them, this requires that the outlines of objects fit into the field of view of the compound eye.

The color vision of insects can be dichromatic (ants, bronze beetles) or trichromatic (bees and some butterflies). At least one species of butterfly has tetrachromatic vision. There are insects that are able to distinguish colors with only one (upper or lower) half of the compound eye (four-spotted dragonfly). For some insects, the visible part of the spectrum is shifted to the short-wavelength side. For example, bees and ants do not see red (650-700 nm), but they distinguish part of the ultraviolet spectrum (300-400 nm). Bees and other pollinating insects can see ultraviolet patterns on flowers that are hidden from human vision. Similarly, butterflies are able to distinguish elements of the color of the wings, visible only in ultraviolet radiation.

The perception of sounds transmitted through a solid substrate is carried out in insects by vibroreceptors located in the shins of the legs near their articulation with the thigh. Many insects are highly sensitive to shaking of the substrate they are on. The perception of sounds through air or water is carried out by phonoreceptors. Diptera perceive sounds with the help of Johnston organs. The most complex auditory organs of insects are the tympanic organs. The number of sensilla in one tympanic organ varies from 3 (some butterflies) to 70 (locusts) and even up to 1500 (singing cicadas). In grasshoppers, crickets, and mole crickets, the tympanal organs are located in the shins of the forelegs, in acridoids, on the sides of the first abdominal segment. The auditory organs of song cicadas are located at the base of the abdomen in the vicinity of the sound-producing apparatus. The auditory organs of moths are located in the last thoracic segment or in one of the two anterior abdominal segments and can perceive ultrasounds emitted by bats. Honey bees make sounds by causing part of the thorax to vibrate through frequent muscle contractions. The sound is amplified by the wing plates. Unlike many insects, bees can make sounds. different heights and timbres, allowing them to convey information through different characteristics sound.

Vision

Insects have a highly developed olfactory apparatus. The perception of smells is carried out thanks to chemoreceptors - olfactory sensilla located on the antennae, and sometimes on the perioral appendages. At the level of chemoreceptors, the primary separation of olfactory stimuli occurs due to the presence of two types of receptor neurons. Generalist neurons recognize a very broad set of chemical compounds, but at the same time have a low sensitivity to odors. Specialist neurons respond only to one or a few related chemical compounds. They provide the perception of odorous substances that trigger certain behavioral reactions (sex pheromones, food attractants and repellents, carbon dioxide). In male silkworms, the olfactory sensilla reach a theoretically possible limit of sensitivity: only one molecule of the female pheromone is sufficient to excite a specialist neuron. In his experiments, J. A. Fabre determined that males of the pear-eye can detect females by pheromones at a distance of up to 10 km.

Contact chemoreceptors form the peripheral part of the taste analyzer of insects and allow them to assess the suitability of the substrate for food or oviposition. These receptors are located on the mouthparts, tips of the legs, antennae, and ovipositor. Most insects are able to recognize solutions of salts, glucose, sucrose and other carbohydrates, as well as water. Insect chemoreceptors rarely respond to artificial substances that mimic sweet or bitter tastes, unlike vertebrate chemoreceptors. For example, saccharin is not perceived by insects as a sweet substance.