What are the sense organs of insects? Insect sense organs
Experiencing the varied and energetic activity 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 acquired life experience. For perception of the surrounding world, orientation in it, implementation of all appropriate 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?
Nervous system is a complex complex of structures and organs consisting of nervous tissue, where the central part is the brain. The main structural and functional unit of the nervous system is the nerve cell with its processes (in Greek, nerve cell - neuron).
The nervous system and brain of insects provide: perception through the senses of external and internal irritation (irritability, sensitivity); instant processing of incoming signals by the system of analyzers, preparation and implementation of an adequate response; storing hereditary and acquired information in encoded form in memory, as well as instantly retrieving it as needed; management of all organs and systems of the body for its functioning as a whole, balancing it with the environment; implementation mental processes and higher nervous activity, expedient behavior.
The organization of the nervous system and brain of vertebrate and invertebrate animals is so different that their comparison at first glance seems impossible. And at the same time, the most diverse types of nervous systems, belonging to seemingly completely “simple” and “complex” organisms, are characterized by the same functions.
The very tiny brain of a fly, bee, butterfly or other insect allows it to see and hear, touch and taste, move with great precision, moreover, fly using an internal “map” over considerable distances, communicate with each other and even own its “language”, learn and apply in non-standard situations logical thinking. Thus, the ant’s brain is much smaller than the head of a pin, but this insect has long been considered a “sage.” When compared not only to his microscopic brain, but also to the incomprehensible capabilities of a single nerve cell, man should be ashamed of his most modern computers. 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 life of the brain - this most complex and mysterious of phenomena known to people?
The first neurobiological experiment belongs to the ancient Roman physician Galen. Having cut the pig's nerve fibers, with the help of which the brain controlled the muscles of the larynx, he deprived the animal of its voice - it immediately became numb. This was a thousand years ago. But how far has science come since then in its knowledge of how the brain works? It turns out that despite great work scientists, the principle of operation of even one nerve cell, the so-called “brick” from which the brain is built, is still unknown to humans. Neuroscientists understand a lot about how a neuron “eats” and “drinks”; how it receives the energy necessary for its life activity by digesting in “biological boilers” the necessary substances extracted from the environment; how this neuron then sends a wide variety of information to its neighbors in the form of signals, encoded either in a specific series of electrical impulses or in various combinations of chemicals. What then? Now the 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. The incoming information is memorized, the necessary information is retrieved from memory, decisions are made, orders are given to muscles and various organs, etc. How is everything going? Scientists still don’t know this for sure. Well, since it is not clear how individual nerve cells and their complexes operate, the principle of operation of the entire brain, even one as small as that of an insect, is also not clear.
The work of 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 negligible, although they are widely used in nature. These are also determinants of various physical fields that make it possible to predict earthquakes, volcanic eruptions, floods, and weather changes. This is a sense of time, counted by the internal biological clock, and a sense of speed, and the ability to orient and navigate, and much more.
The property of every organism (microorganisms, plants, fungi and animals) to perceive irritations emanating from external environment and from their own organs and tissues, is called sensitivity. Insects, like other animals with a specialized nervous system, have nerve cells with a high selective ability to various stimuli - receptors. They can be tactile (responsive to touch), temperature, light, chemical, vibration, muscle-articular, etc. Thanks to their receptors, insects capture a wide 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 collected in systems to form specialized sensory organs - sense organs.
All insects perfectly “understand” the readings of their sense organs. Some of them, like the organs of vision, hearing, and smell, are remote and are capable of perceiving irritation at a distance. Others, like the organs of taste and touch, are contact and react to influence through direct contact.
Insects are generally endowed with excellent vision. Their complex compound eyes, to which simple ocelli are sometimes added, are used to recognize various objects. Some insects are provided with color vision and suitable night vision devices. Interestingly, the eyes of insects are the only organ that is similar to other animals. 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, orient themselves in space, and capture and emit ultrasonic waves. Their delicate sense of smell and taste allows them to find food. Various glands of insects secrete substances to attract brothers, sexual partners, scare away rivals and enemies, and a highly sensitive sense of smell can detect the smell of these substances even from several kilometers away.
Many in their ideas associate the sensory organs of insects with the head. But it turns out that the structures responsible for collecting information about the environment are located 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, mustaches, tail appendages, body hairs, etc.
The sense organs of insects are part of sensory systems - analyzers, which permeate almost the entire organism with a network. They receive many different external and internal signals from the receptors of their sense organs, analyze them, form and transmit “instructions” to various organs to carry out appropriate actions. The sense organs mainly make up the receptor department, which is located at the periphery (ends) of the analyzers. And the conductive section is formed by central neurons and pathways from receptors. The brain has specific areas for processing information from the senses. They form the central, “brain” part of the analyzer. Thanks to such a complex and practical system, for example a visual analyzer, precise calculation and control of the insect’s organs of movement are carried out.
Extensive knowledge has been accumulated about the amazing capabilities of the sensory systems of insects, but the volume of the book allows us to cite 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 assess the situation that has arisen. Vision is necessary for insects when searching for food, to avoid predators, to explore objects of interest or the environment, to interact with other individuals during reproductive and public behavior etc.
Insects are equipped with a variety of eyes. They can be complex, simple or accessory ocelli, and also larval. The most complex are compound eyes, which consist of large number ommatidia, forming hexagonal facets on the surface of the eye. Ommatidium is essentially a tiny visual apparatus equipped with a miniature lens, a light-conducting system and light-sensitive elements. Each facet perceives only a small part of the object, but together they provide a mosaic image of the entire object. Compounded eyes, characteristic of most adult insects, are located on the sides of the head. In some insects, for example, in the hunting dragonfly, which quickly reacts to the movement of prey, the eyes occupy half of the head. Each of her eyes is made of 28,000 facets. For comparison, butterflies have 17,000 of them, and houseflies have 4,000. Insects can have two or three eyes on their heads on the forehead or crown, and less often on its sides. The larval eyes of beetles, butterflies, and hymenoptera are replaced by complex ones in adulthood.
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 a hunting insect, 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 mantis with binocular vision and allow it to accurately calculate distances to the object of their attention. This ability, combined with the rapid extension of its front legs towards prey, makes mantises excellent hunters.
And the yellow-footed beetles, running through the water, have eyes that allow them to simultaneously see prey both on the surface of the water and under it. To achieve this, beetle visual analyzers have the ability to correct for the refractive index of water.
The perception and analysis of visual stimuli is carried out by a very complex system - the visual analyzer. For many insects, this is one of the main analyzers. Here the primary sensitive cell is the photoreceptor. And connected to it are pathways (optic nerve) and other nerve cells located at different levels of the nervous system. 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 pathways to the central nervous system - to the “brain” center of the analyzer. There, these signals are immediately decoded (deciphered) into the corresponding visual perception. To recognize it, standards of visual images and other necessary information are extracted from memory. And then a command is sent to various organs for an adequate response of the individual to the changing situation.
Where are the “ears” of insects?
Most animals and humans hear through their ears, where sounds cause the eardrum to vibrate - strong or weak, slow or fast. Any changes in vibrations provide the body with information about the nature of the sound being heard. How do insects hear? In many cases, they also have peculiar “ears,” but in insects they are located in places unusual for us: on the whiskers - for example, in male mosquitoes, ants, butterflies; on the tail appendages - in the American cockroach. The shins of the front legs hear crickets and grasshoppers, and the belly hears locusts. Some insects do not have “ears,” that is, they do not have special hearing organs. But they are capable of perceiving various vibrations in the air, including sound vibrations and ultrasonic waves that are inaccessible to our ears. The sensitive organs of such insects are thin hairs or tiny sensitive rods. They are located in large numbers on different parts of the body and are associated with nerve cells. Thus, in hairy caterpillars, the “ears” are hairs, and in naked caterpillars, the entire skin of the body is the “ears”.
A sound wave is formed by alternating rarefaction and condensation of air, spreading in all directions from the source of sound - any vibrating body. Sound waves are perceived and processed by the auditory analyzer - a complex system of mechanical, receptor and neural structures. These vibrations are converted by auditory receptors into nerve impulses, which are transmitted along the auditory nerve to central part analyzer. The result is the perception of sound and analysis of its strength, height and character.
Insect auditory system ensures their selective response to relatively high-frequency vibrations - they perceive the slightest vibrations of the surface, air or water. For example, buzzing insects produce sound waves by rapidly flapping their wings. Males perceive such vibrations in the air, for example the squeak of mosquitoes, with their sensitive organs located on the antennae. In this way, they detect air waves that accompany the flight of other mosquitoes and respond adequately to the received sound information. The auditory systems of insects are “tuned” to perceive relatively weak sounds, so loud sounds have an impact on them. bad influence. For example, bumblebees, bees, and some types of flies cannot rise into the air when they sound.
The varied but strictly defined signal sounds produced by the male crickets of each species play important role in their reproductive behavior - when courting and attracting females. Cricket provides 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 the other. And for the perception of sound, the male and female have a particularly sensitive thin cuticular membrane, which plays the role of an eardrum. An interesting experiment was done when a chirping 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, hearing 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 provided 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 the moths and lacewings they hunt – up to 240,000 hertz. In the chest, for example, moth moths have special organs for acoustic analysis of ultrasonic signals. They make it possible to detect ultrasonic pulses from hunting leatherbacks at a distance of up to 30 m. When the butterfly perceives a signal from the predator's locator, protective behavioral actions are activated. Having heard the ultrasonic cries of a night mouse at a relatively large distance, the butterfly abruptly changes its flight direction, using a deceptive maneuver - “diving”. At the same time, she begins to perform aerobatic maneuvers - spirals and “loops” to escape pursuit. And if the predator is less than 6 m away, the butterfly folds its wings and falls to the ground. And the bat does not detect the motionless insect.
But, the relationship between moths and bats, as recently discovered, have proven to be even more complex. Thus, 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 have such an effect on the predator that it, as if frightened, flies away. There is only speculation as to what makes bats stop chasing the butterfly and “flee 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 plane is breaking the sound barrier.
This begs the question of why the bat is deafened 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 produces and purposefully uses a special stirrup. Before sending an ultrasonic pulse, a special muscle pulls the stapes 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 the scream-signal, it immediately returns to its place so that the ear is ready to receive the reflected signal. It is difficult to imagine how fast a muscle can act that turns off a mouse’s hearing at the moment of sending a cry-impulse. While chasing prey, this is 200-250 pulses per second!
And butterfly click signals, dangerous for the bat, are heard exactly at the moment when the hunter turns on his ear to perceive his echo. This means that in order to force a stunned predator to fly away in fear, the moth sends signals that are perfectly matched to its locator. To do this, the insect's body is programmed to receive the pulse frequency of an approaching hunter and sends a response signal exactly in unison with it.
This relationship between moths and bats raises many questions. How did insects develop the ability to perceive ultrasonic signals from bats and instantly understand the danger they pose? How could butterflies gradually develop, through the process of selection and improvement, an ultrasonic device with ideally selected protective characteristics? The perception of ultrasonic signals from bats is also not easy to understand. The fact is that they recognize their echo among millions of voices and other sounds. And no screaming signals from fellow tribesmen, no ultrasonic signals emitted using equipment interfere with the bats’ hunting. Only butterfly signals, even artificially reproduced ones, cause the mouse to fly away.
Living beings present new and new mysteries, causing admiration for the perfection and expediency of the structure of their organism.
The praying mantis, just like the butterfly, along with excellent eyesight, is also given special hearing organs to avoid encounters with bats. These hearing organs, which perceive ultrasound, are located on the chest between the legs. And some species of mantises, in addition to the ultrasonic hearing organ, are characterized by the presence of a second ear, which perceives much lower frequencies. Its function is not yet known.
Chemical feeling
Animals are endowed with 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. It is difficult for us to imagine what this is. The insect's olfactory organs react to the presence of even very small concentrations of a substance, sometimes very distant from the source. Thanks to the sense of smell, the insect finds prey and food, navigates the area, learns about the approach of an enemy, and carries out biocommunication, where a specific “language” is the exchange of chemical information using pheromones.
Pheromones are complex compounds secreted for communication purposes by some individuals in order to transmit information to other individuals. Such information is encoded in specific chemicals, depending on the type of living creature and even on its membership in a particular family. Perception through the olfactory system and decoding of the “message” causes a certain form of behavior or physiological process in the recipients. A significant group of insect pheromones is known to date. Some of them are designed to attract individuals of the opposite sex, others, traces, indicate the way to a home or food source, others serve as an alarm signal, and others regulate certain physiological processes etc.
The “chemical production” in the body of insects must be truly unique in order to release in the right quantity and at a certain moment the entire range of pheromones they need. Today, more than a hundred of these highly complex substances are known. chemical composition, but no more than a dozen of them were artificially reproduced. After all, to obtain them, advanced technologies and equipment are required, so for now one can only be amazed at the arrangement of the body of these miniature invertebrate creatures.
Beetles are provided mainly with antennae of the olfactory type. They allow you to capture not only the smell of the substance itself and the direction of its spread, but even “feel” the shape of the odorous object. An example of an excellent sense of smell is burying beetles, which clean the earth from carrion. They are able to smell it hundreds of meters away and gather large group. And the ladybug, using her sense of smell, finds colonies of aphids in order to leave clutches there. After all, aphids feed not only on themselves, but also on their 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 increased concentration carbon dioxide. In experiments, the larvae immediately go to the area of the soil where they have not been introduced. a large number of substances that form carbon dioxide.
The sensitivity of the olfactory organ, for example, of the Saturnia butterfly, the male of which is able to detect the smell of a female of his 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 finds, among many odorous substances, one single molecule of a hereditarily known substance in 1 m3 of air!
Some Hymenoptera have such a keen sense of smell that it is not inferior to the well-known sense of a dog. Thus, 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 woodcutter 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 rider Helis, by just touching them on the cocoons of spiders, determines what is in them - whether they are underdeveloped testicles, inactive spiders that have already emerged from them, or the testicles of other riders of their species. How Helis makes such an accurate analysis is not yet known. Most likely, he senses a very subtle specific odor, but perhaps when tapping his antennae, the rider catches some kind of reflected sound.
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 perceptive, conductive and central department. Olfactory receptors (chemoreceptors) perceive odorant molecules, and impulses signaling a specific odor are sent along nerve fibers to the brain for analysis. There the body’s immediate response occurs.
Talking about insects' sense of smell, we can’t help but mention 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 olfactory receptors included in odor analyzers. If the configuration of the molecule matches the “lock” of a certain receptor, 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 chemical properties 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 components. Any aroma 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 fragrant substances and thousands of types of odor-sensing cells can be assessed using infrared frequencies.
"Radar installation" of insects
Insects are endowed with excellent organs of smell and touch - antennae (antennae or antennae). They are very mobile and easy to control: an insect can spread them apart, bring them closer together, rotate each individually on its own axis or together on a common one. In this case, they both externally resemble and are essentially a “radar installation”. The nerve-sensitive element of the antennae is the sensilla. From them, an impulse is transmitted at a speed of 5 m per second to the “brain” center of the analyzer to recognize the object of stimulation. And then the response signal to the received information instantly reaches the muscle or other organ.
In most insects, the Johnston's organ is located on the second antennal segment - universal device, the purpose of which has not yet been fully clarified. It is believed that it perceives movements and vibrations of air and water, contacts with solid objects. Locusts and grasshoppers are endowed with surprisingly high sensitivity to mechanical vibrations, which are capable of registering any shaking with an amplitude equal to half the diameter of a hydrogen atom!
Beetles also have a Johnston's organ on the second antennal segment. And if the beetle running on the surface of the water is damaged or removed, it will begin to bump into any obstacles. With the help of this organ, the beetle is able to catch reflected waves coming from the shore or an obstacle. It senses water waves with a height of 0.000,000,004 mm, that is, the Johnston's 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 utmost 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 the road, nearby food, and distinguish enemies from friends. With the help of antennas, insects are able to “talk” to each other. Ants transmit important information by touching their antennae to certain segments of each other's antennae. In one of the behavioral episodes, two ants found prey in the form of larvae of different sizes. After “negotiating” with their brothers using antennas, they headed to the place of discovery together with mobilized assistants. At the same time, the more successful ant, who managed to convey information about the larger prey he found with the help of his antennae, mobilized much more large group worker ants.
Interestingly, ants are one of the cleanest creatures. After every meal and sleep, their entire body and especially their antennae are thoroughly cleaned.
Taste sensations
A person clearly identifies the smell and taste of a substance, but in insects the taste and olfactory sensations are often not separated. They act as a single chemical feeling (perception).
Insects that have a sense of taste have a preference for certain substances depending on the nutrition characteristic of a given species. At the same time, they are able to distinguish between sweet, salty, bitter and sour. To come into 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, just touching an object that interests it with its paws, almost immediately recognizes what is under its feet - drink, food or something inedible. That is, she is able to carry out instant contact analysis of a chemical substance with her feet.
Taste is a sensation occurring when a solution of chemicals acts on the receptors (chemoreceptors) of the insect’s taste organ. Taste receptor cells are a peripheral part of the complex taste analyzer system. They perceive chemical stimuli, and this is where 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 continue to understand not only the question of what smell is, but also to create a unified theory of “sweetness”. So far this has not been possible - maybe you, biologists of the 21st century, will succeed. The problem is that completely different chemical substances, both organic and inorganic, can create relatively identical taste sensations of sweetness.
Organs of touch
Studying the sense of touch in insects is perhaps the most difficult. How do these chitinous shell-clad creatures perceive the world? Thus, thanks to skin receptors, we are able to perceive various tactile sensations– some receptors record pressure, others temperature, etc. By 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 about the mechanisms of their action remains unknown.
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 that perform tactile functions. There are especially many of them on the halteres to sense air pressure and stabilize flight.
Thanks to the sense of touch, the fly is not so easy to swat. Its vision allows it to notice a threatening object only at a distance of 40 - 70 cm. But the fly is able to react 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 living world - all creatures, young and old, are provided with excellent sensory systems for active life and their own protection.
Insect receptors that record 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, before pupation, a fly larva always clearly moves upward, that is, against gravity. After all, she needs to crawl out of the liquid food mass, and there are no guidelines there other than the gravity of the Earth. Even after emerging from the pupa, the fly still strives to crawl upward 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 the slope of a surface to be 20. And the rove beetle, which digs vertical burrows, can determine the deviation from the vertical to be 10.
Live weather 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 functioning 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 both cases, they use their internal “weather stations”.
By constantly and carefully observing the behavior of various living beings, you can learn not only about weather changes, but even about upcoming natural disasters. After all, over 600 species of animals and 400 species of plants, so far known to scientists, can serve as barometers, indicators of humidity and temperature, predictors of thunderstorms, storms, tornadoes, floods, and beautiful cloudless weather. Moreover, there are live “forecasters” everywhere, wherever you are - near a pond, in a meadow, in a forest. For example, before the rain, while the sky is still clear, green grasshoppers stop chirping, ants begin to tightly close the entrances to the anthill, and bees stop flying for nectar, sit in the hive and hum. In an effort to hide from the approaching bad weather, flies and wasps fly into the windows of houses.
Observations on poisonous ants, living in the foothills of Tibet, revealed their excellent ability to make longer-range forecasts. Before the start of a period of heavy rains, the ants move to another place with dry hard ground, and before the onset of drought, ants fill dark, damp depressions. Winged ants are able to sense the approach of a storm within 2–3 days. Large individuals begin to scurry along the ground, and small ones swarm at low altitudes. And the more active these processes are, the stronger the bad weather is expected. It was revealed that over the course of a 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 average error weather stations in 20%.
The appropriate actions of insects often depend on long-term forecasts, and this can be of great service to people. For an experienced beekeeper, bees provide a fairly reliable forecast. For the winter, they seal the hive entrance with wax. You can judge the upcoming winter by the hole for ventilation of the hive. If the bees leave big hole– the winter will be warm, and if it’s small, expect severe frosts. It is also known that if bees begin to fly out of their hives early, we can expect an early, warm spring. The same ants, if the winter is not expected to be severe, remain to live near the surface of the soil, and in front cold winter are located deeper in the ground and build a higher anthill.
In addition to the macroclimate, the microclimate of their habitat is also important for insects. For example, bees do not allow overheating in the hives and, having received a signal from their living “instruments” about the temperature being exceeded, they begin to ventilate the room. Some of the worker bees are located in an organized manner on different heights throughout the hive and moves the air with rapid flapping of its wings. A strong air flow is created and the hive cools. Ventilation is a long process, and when one group 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
In insects, there are mechanical senses (touch, vibrations), hearing, chemical senses (smell, taste), hygrothermal senses (dryness, warmth), and vision.
The sense organs are based on formations with slightly different structures - sensilla (sensitive elements) (Figure 27).
The organs of touch, or tactile sensilla, are nerve endings in the skin and its appendages in the form of special sensitive hairs, bristles, and spines located throughout the insect’s body, especially on the antennae, labial and maxillary palps and legs. They detect various mechanical irritations (touch), thermal irritations, changes in air pressure (figure).
The chemical sense organs (smell, taste) in insects are concentrated on the antennae in the form of pits, hairs, etc., to which the endings of the nerve branches from the suprapharyngeal ganglion approach. The sense of smell of insects is extremely subtle and serves to find food, as well as to find one sex for the other. In males, since they search for females using their sense of smell, the size and overall surface of the antennae are much larger than those of females. For example, many males of different species have feathery antennae with a large surface. The taste organs have the same structure, but are located inside the oral cavity and on the oral organs. Insects' sense of taste is also highly developed; for example, ants accurately select grains of sugar from a mixture of quinine powder and sugar.
Not all insects have hearing organs. The most developed and complex organs of hearing, the so-called tympanic, are found in the order of Orthoptera - grasshoppers, crickets, locusts, which also have the ability to make loud sounds. The organs are like a hole in the skin, covered with a thin membrane. From the inside, branches of the auditory nerve approach this membrane. In grasshoppers and crickets, the tympanic organs are located on the tibia of the front legs; in locusts they are located on the sides of the first abdominal segment (Figure 28).
Organs of vision In insects there are complex or facet eyes and simple eyes, or ocelli (Figure 29).
Compounded eyes, found in most insects, are located on the head and sometimes occupy most of it (for example, in flies, dragonflies, etc.). They each consist of numerous individual ocelli, as a result of which the surface of the compound eye appears in the form of numerous individual facets, round or hexagonal (Figure 30).
In a longitudinal section, each eye consists of the following layers:
transparent cornea(biconvex or flat-convex; light-refracting conical part - crystal cone; light-receiving part - retina or retina. Branches of nerves from the suprapharyngeal ganglion approach the retina.
Every peephole lets you through light rays only through the central part, giving on the retina an image of only individual parts of the object in question. In general, the compound eye gives a mosaic display of the entire object. The more facets there are in the structure of the eye (up to several tens of thousands), the clearer the image is (especially in predatory insects).
Simple eyes, numbering from one to three, are located on the forehead or crown (Figure 31). They are constructed in much the same way as the individual ocelli in compound eyes, but do not have a light-refracting cone. Being a very imperfect organ of vision, they capture only the intensity and direction of light. Not all insects have eyes; many dipterans, beetles and butterflies do not have them.
In insects, the eyes perceive polarized rays, and a light-compass movement in relation to the light source is developed, which is used when monitoring nocturnal forest pests in light traps (Figure 32).
1. Open the insect by making incisions along the pleural part of the body. Attach to the bottom of the bath.
2. Discover and examine the internal organ systems: circulatory, digestive, excretory, reproductive, nervous.
3. Consider the sensory organs of insects: eyes, ocelli, auditory organs, sensitive hairs.
4. Make notes and sketch the structure of individual organ systems.
Materials and equipment: freshly killed insects - black cockroaches, grasshoppers, chafers, their larvae. Insects in the collections include dragonflies, bees, longhorned beetle larvae, grasshoppers, and locusts. Dissection baths filled with paraffin or wax, tweezers, scalpels, dissection needles, pipettes, saline solution, binocular microscopes, 10 x magnifiers, towels, cotton wool.
1. Bey-Bienko, G. Ya. General entomology./ G. Ya. Bey-Bienko. - M., Higher School, 1980. – 416 p.
2. Mozolevskaya, E.G. et al. Workshop on forest entomology./ E.G. Mozolevskaya, N.K. Belova, G.S. Lebedeva and others - M.: Academy, 2004. - 288 p.
3. Kharitonova N.Z. Forest entomology. – Mn.: Higher School, 1994. – 412 p.
4. Ross G., Ross D., Ross Ch. Entomology, M.: Mir, 1985 – 429 p.
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Sense organs are described separately from their 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 sensory nerve endings.
Reception and receptors
Any sensory 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 mechanical vibrations 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, etc. In general, mechanoreceptors are very 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 not be possible. For example, worker bees in a hive constantly monitor the temperature of the nest area where they develop and (photo). They either insulate them or cool them. The temperature is always maintained at 34.5-35.5 degrees, since 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 been found to have 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 have been poorly studied.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 sent 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 on the oral organs of most groups. However, in flies (photo) , butterflies and bees, they are also located on the front legs (more precisely, on their). Foldoptera wasps are distinguished by the presence of taste organs on the antennal segments.Insects are best at distinguishing sweets; they are also able to recognize sour, bitter and salty. Sensitivity to different tastes varies among different insects. For example, butterfly caterpillars find lactose sweet, but bees find it tasteless. But bees are very sensitive to salty foods.
The general structure of the nervous system of insects is the same as that of other arthropods. Along with cases of strong division (suprapharyngeal, subpharyngeal, 3 thoracic and 8 abdominal ganglia) and the paired structure of the nervous system in primitive insects, there are cases of extreme concentration of the nervous system: the entire abdominal chain can be reduced to a continuous ganglion mass, which is especially common in larvae and larval adults with no limbs and weak body dismemberment.
In the suprapharyngeal ganglion, the development of the internal structure of the protocerebral part of the brain is noticeable, in particular the mushroom bodies, forming 1-2 pairs of tubercles on the sides of the midline. The brain is well developed, and especially its anterior section, in which there are special paired formations responsible for complex forms of behavior.
Among the organs, represented by numerous hairs, bristles, depressions - to which nerve endings are suitable - there are various receptors that perceive different types irritants - mechanical, chemical, temperature and so on, the sense organs of touch and smell predominate in their importance. The mechanical sense organs include both the organs of touch and the organs of hearing, which perceive air vibrations as sounds. The organs of touch are represented on the surface of the body of insects by bristles. Chemical sense organs - serve to perceive the chemistry of the environment (taste and smell). Olfactory receptors, also in the form of bristles - sometimes modified into thin-walled detached outgrowths, non-segmented finger-like projections, thin-walled flat areas of the integument, most often located on the antennae, taste - on the organs oral apparatus, but sometimes on other parts of the body - in flies, for example, on the terminal segments of the legs. The sense of smell has vital importance in intra- and inter-population relationships of insect individuals.
With the help of complex compound eyes consisting of sensilla, the hexagonal parts of which are called facets form a cornea from a transparent cuticle - insects are able to distinguish the sizes, shapes and colors of objects. The honey bee, for example, distinguishes all the same colors as humans, except red, but also ultraviolet colors that are not distinguished by the human eye. Simple eyes of insects - reacting to the degree of illumination, ensure the stability of image perception with compound eyes, but are not able to distinguish color and shape.
Insects of some orders, the species of which have males with sound organs - for example, Orthoptera - have tympanic organs, the structure of which suggests that these are organs of hearing. In grasshoppers and crickets they are on the lower leg under the knee joint, in locusts and cicadas they are on the sides of the first abdominal segment and are externally represented by a depression (sometimes surrounded by a fold of the integument) with a thinly stretched membrane at the bottom, on the inner surface of which or near it there is a nerve ending peculiar structure; on the wings of some other insects, etc.
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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 organ functioning 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 subpharyngeal ganglion. The three thoracic segments contain nerve ganglia that control the movements of the legs and wings. Eight nerve ganglia located in the posterior part of the body innervate their area of the body. The nerve ganglia are connected to each other and to other nerve centers by nerve trunks. Thus, the nervous system of insects is built on the principle of a rope ladder. In many insects, the nerve ganglia of the thoracic segments and the posterior part of the body merge into larger ganglia.
How do insects breathe?
Air is distributed through a complex system of tubes throughout the insect's body. On each side of the thoracic and abdominal segments there is one respiratory opening. Tracheas and respiratory tracts extend from it, which branch intensively. 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. To prevent moisture from leaving the respiratory tract, the insect closes the respiratory openings with hairs; This also eliminates the possibility of foreign bodies getting into them. The trachea is covered from the inside with a cuticle, which is renewed with each change of the shell.
Do insects have ears?
"Drum" skin is present in the body of many insects. This “ear” is often receptive 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 various parts of its body: in cicadas and some moths, on the back of the body, in other butterflies, in the last thoracic segment. Grasshoppers have “ears” located under the knees on their front legs. Many insects use their ears to communicate: female grasshoppers and crickets find singing males. But insects also have other sense organs 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 sense 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 them communicate with relatives, find appropriate place habitat for themselves and their offspring, as well as food. The females of many insects attract males using scents. Male lesser night peacocks can smell a female from several kilometers away. Ants recognize females from their anthill by smell. Some types of ants mark the path from the nest to the food source thanks to odorous substances that are released from special glands. With the help of their antennae, ants and termites smell the scent left by their relatives. If both antennae pick up the scent to the same extent, then the insect is on the right track. Attractant substances released by female butterflies ready to mate are usually carried by the wind.