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, and 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 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. Insects, like other animals with a specialized nervous system, have nerve cells with a high selectivity 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 off rivals and enemies, and a highly sensitive sense of smell is able to detect 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
Eyes and the entire most 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 light-sensitive 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, for example, a hunter 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 a housefly has 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 the most 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're in in large numbers located on different parts of the body and associated with nerve cells. So, in hairy caterpillars, the “ears” are hairs, and in naked caterpillars, the whole skin covering 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 important role in their reproductive behavior - when 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. Has been done interesting experience 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, 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 ultrasonic impulses 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 the 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 night butterflies and bats have 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". It is likely that 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 inner ear– 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 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 should 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 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. 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 maybe when tapping his antennae, the rider picks up 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 - 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.
Talking about the smell of insects can't say enough about the smell. In science, there is still no clear understanding of what a 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 distribution electric charges. The newest theory, which has won many supporters, main reason smell sees 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 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 convey information about the larger prey it found with the help of antennae, mobilized much more large group worker ants.
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 the main 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 sensation arising from the action of a solution of chemicals on the receptors (chemoreceptors) of the insect's taste organ. Taste receptor cells are the peripheral part complex system 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 nothing is 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 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 also rarely observed natural phenomena - droughts, floods, sharp 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, over 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 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
Organs of touch. Presented as sensitive hairs from large to microscopic in size, they are located almost on the entire surface of the body, especially on those parts that often come into contact with surfaces and environmental objects. The most concentrated on the antennae, legs, appendages of the abdomen, mouth organs. In its simplest form, the organ of touch is the trichoid sensilla. When touched or exposed to air flow, the hair moves. This irritates the underlying nerve cells, which transmit nerve impulses to the brain.
The organ of hearing on the abdomen
Hearing organs. As a rule, they are well developed in those insects that themselves make sounds. Since these sounds are primarily intended for communication between representatives of the species, it is naturally important to be able not only to make them, but also to hear them. The auditory organs of insects are also called tympanic organs. They look like sections of the cuticle, over which a membrane is stretched, vibrating from sound waves. In other words, this is a primitive version of the "ears". True, they are not located on the head, like the ears of animals and humans, but on other parts of the body. For example, in cicadas and locusts, they are located on the first segment of the abdomen, and in crickets and grasshoppers, they are on the shins of the first pair of limbs.
Paws - location
fly's taste organ
organs of taste. Sensitive chemoreceptors are found in most groups on the oral organs. However, in flies, butterflies and bees, they are also located on the front legs (more precisely, on their legs). Folded-winged wasps are distinguished by the presence of taste organs on the apical 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.
Organs of smell. Insects “sniff” with their antennae, since sensitive olfactory chemoreceptors are located mainly on them. Sometimes this process can be observed with one's own eyes, especially on the example of bees, which, sitting on a flower, first "feel" it with their antennae, and then immerse their mouth organs in its calyx. The olfactory organs can also be located in other parts of the cuticle. They are presented in the form of cones or plates located in the recesses of the cuticle.
Male insects often have a stronger sense of smell than females. Insects are generally more sensitive to certain odors than humans. For example, the scent of geraniol (an organic substance used as a fragrance in perfumery) is 40 to 100 times stronger in bees than in humans. With the help of smells, insects also “communicate” with each other. So, male butterflies distinguish the smell of female pheromones in the air, even if they are at a distance of 3-9 km from them.
organs of vision. They can be represented by complex compound eyes and simple (dorsal) ocelli, and larvae sometimes have larval (lateral) ocelli. The function of vision is best performed by compound eyes; in larval ocelli, vision is rather weak, and dorsal ocelli do not see at all.
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 surface of the skin 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 capture 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 are distinguished from clean water sugar solution with a concentration of 0.0027%. 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 nearsighted and can only distinguish movement at a distance. 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 by blue sky, which allows it to navigate 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).
The general plan of the structure of the nervous system of insects is the same as that of other arthropods. Along with cases of strong dissection (supraoesophageal, suboesophageal, 3 thoracic and 8 abdominal ganglia) and pair 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 ganglionic mass, which is especially common in larvae and larval adults in the absence of limbs and a weak dismemberment of the body.
In the supraesophageal ganglion, the development of the internal structure of the protocerebral part of the brain, in particular, the mushroom bodies, forming 1-2 pairs of tubercles on the sides of the midline, is noticeable. 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 the nerve endings fit - various receptors that perceive different types stimuli - mechanical, chemical, temperature, and so on, the sense organs of touch and smell prevail in their significance. The organs of mechanical sense 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. Organs of chemical sense - serve to perceive the chemistry of the environment (taste and smell). Olfactory receptors, also in the form of a bristle - sometimes changing into thin-walled detached outgrowths, non-segmented finger-like protrusions, 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 is of great importance in intra- and interpopulation relations 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, can see all the same colors as humans, except for red, but also ultraviolet colors that are invisible to 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 tympanal 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 cover) with a thinly stretched membrane at the bottom, on inner surface which or close to it is the nerve ending of a peculiar structure; some other insects have wings, etc.
Insects have more or less developed sense of touch, smell, taste, hearing and sight. In addition, individual species can distinguish between fluctuations in air temperature and humidity, changes in air and water pressure, the Earth's magnetic field, and the effects of an electrostatic field.
1. Organs touch presented in the form of sensitive hairs located on various parts of the body, especially on the antennae and mouth limbs. The irritation of the hair is transmitted to the tactile nerve cell, where excitation occurs, transmitted through its processes to the nerve center.
2. Organs smell concentrated mainly on the antennae in the form of plates or cones, immersed in the recesses of the cuticle and connected to nerve cells. In males, olfactory elements - sensilla - are usually more than in females. Especially a lot of them in worker bees - up to 6000 plates on each antenna, due to the importance of the sense of smell for their search for nectar. The sensitivity of insects to certain odors is much higher than that of humans. For example, bees detect the smell of geraniol and other essential oils at a concentration 40 ... 100 times less than a person, and labeled males of some butterflies distinguish the smell of a female sexual attractant 11 km away.
3. Organs taste in structure, they are sometimes almost indistinguishable from the organs of smell. They are located on the mouth parts. In butterflies, bees, and flies, gustatory sensilla are also found on the tarsi of the forelegs. A hungry butterfly expands its proboscis when the underside of its paws touches a sugar solution. At the same time, butterflies feel the concentration of sugar in water is 2000 times lower than humans. Insects to some extent can distinguish between sweet, salty, bitter and sour.
4. Organs hearing well developed only in those insects that can make a sound (locusts, grasshoppers, crickets, song cicadas, some bugs). They are presented in the form of tympanal organs, i.e., cuticle sections thinned like a tympanic membrane with an accumulation of sensitive elements. Paired tympanal organs in grasshoppers and cicadas are located on the I segment of the abdomen, in grasshoppers and crickets - on the shins of the front legs. However, many other insects that do not have tympanic organs can also distinguish sounds.
Organs vision usually well developed. Only in insects living underground or in caves, eyes are absent or underdeveloped. Vision is represented by complex and simple eyes. Complex, or faceted, eyes (1 pair) are located on the sides of the head. They consist of many visual elements - ommatidia, or facets, the number of which in a house fly reaches 4,000, and in dragonflies - even up to 28,000 in each eye. Ommatidium consists of a transparent lens, or cornea, in the form of a biconvex lens and a transparent crystal cone lying under it. Together they form a single optical system. Under the cone is the retina, which perceives light rays. Retinal cells are connected by nerve hairs to the visual lobes of the brain. Each ommatidium is surrounded by pigment cells.
Insects can distinguish colors. Aphids, for example, distinguish red, yellow, and green from blue and violet; the swedish fly is attracted to blue shades on a green background; in bees, color vision is shifted towards the short-wave part of the spectrum, and they poorly distinguish its orange-red part, but this is compensated by distinguishing the ultraviolet part inaccessible to the human eye.
Simple eyes, or eyes, are located on the head of an insect in a triangle: 1 median - on the forehead, 2 others - symmetrically on the sides and above on the crown. They are not developed in all insects. The median ocellus often disappears, rarely paired ocelli are absent, while the middle ocellus is preserved. Many Lepidoptera and Diptera are completely devoid of ocelli.
Thanks to a highly developed nervous system and sensory organs, insects perceive a variety of signals coming from the external environment and respond to them with a set of expedient movements, including hereditarily fixed actions. This cumulative reaction of the body is called behavior. Behavior is determined not only by external stimuli, but also by the physiological state of the organism (hunger, puberty, etc.). Behavior is based on a reflex, i.e., a response to irritation. There are unconditioned reflexes, on which simpler acts of behavior are based, and conditioned reflexes, which are elements of higher nervous activity.
Unconditioned reflexes are innate, inherited from their parents. An example of the simplest form of behavior is the state of thanatosis, when, with a sudden shock, shaking of the substrate, reflex inhibition of movements is observed, and the insect falls from the branch to the ground, remaining motionless for some time.
Taxis and instincts are more complex forms of behavior. Taxis are a variety of reflex movements under the influence of a stimulus: thermotaxis - heat, phototaxis - light, hygrotaxis - moisture, chemotaxis - a chemical stimulus, etc. The sign of taxis can be positive or negative, depending on where the insect's movement is directed - to the stimulus or in the opposite direction.
Instincts are complex innate reflexes. They are very important in the life of insects, in the survival of individuals and the population of the species as a whole. Instincts at first glance give the impression of intelligent, conscious action. For example, the female beetle makes lateral oval chambers in the lower part of the vertical passage in the soil, which are filled with lumps of plant mass made from leaves cut in the fields. various plants. She lays one egg on a lump, and the exit from the chamber is covered with soil. On such a kind of silage mass, the larvae of the golden-winged marrow develop, pupating here.
Thus, instincts, even the most complex ones, are a chain of unconditioned reflexes. In this chain, each previous reflex determines the next one. Instincts do not depend on the training of an individual, but are developed in the process of evolution of the species, being hereditarily transmitted from generation to generation.
As first noted by Acad. IP Pavlov, conditioned reflexes are elements of the animal's higher nervous activity. Unlike unconditioned reflexes, they are formed during the life of an individual and are temporary. A conditioned reflex is developed under the influence of combinations of at least two stimuli - unconditioned (for example, food) and conditioned (smell, color, sound, etc.). As a result of the joint action of two - stimuli, a temporary connection arises between the various centers of the nervous system, and the body will react for a certain time only to one conditioned stimulus. However, if the reinforcement with the unconditioned stimulus is not too long, the temporal connection in the central nervous system is broken, and the conditioned reflex fades away.
Reproductive organs. Almost all insects are dioecious, and populations consist of males and females. Only a few insects have hermaphroditism (termitoxenia flies living in termite nests, some coccids). External differences between male and female are often slight or absent, in which case individuals differ only in genital appendages. Along with this, quite pronounced sexual dimorphism is often found in insects.
In the presence of sexual dimorphism, males are distinguished by a stronger development of antennae (May beetle, cockchafers, butterflies from the family of wolves and silkworms), eyes (bee and folded wasps), mouthparts (stag beetle), cerci (earwigs), skin appendages (beetle -rhinoceros), as well as a brighter body color and greater mobility. The most pronounced sexual dimorphism is expressed in representatives of the fan-winged order (winged male, wingless female worm-shaped), most species of coccids, some butterflies (winter moth, gypsy moth, etc.).
The reproductive organs of the female consist of paired ovaries, paired oviducts, an unpaired oviduct, paired accessory glands, and sometimes a seminal receptacle. The ovaries are made up of oviducts in which eggs are formed. The number of egg tubes various kinds insects varies greatly: from 4...8 pairs in some beetles and butterflies to 220 pairs in honey bees, the maximum number was noted in female termites - 12,000 pairs or more. The egg tubes are usually combined into several ducts that empty into one of the paired oviducts.
The paired oviducts pass into the unpaired oviduct, which opens outward through the genital opening. A relatively narrow duct of the seminal receptacle often flows into the unpaired vas deferens (some flies have 2...3 seminal receptacles). The seminal receptacle, or spermatheca, serves to store the male's spermatozoa, which fall into it during mating. Storage of spermatozoa sometimes lasts up to 4-5 years, for example, in honeybees. Fertilization of the egg occurs when it passes through the unpaired oviduct during oviposition. At this time, the spermatozoa leave the seminal receptacle and fertilize the egg. Often in females, the unpaired oviduct at the posterior end expands, forming a sac-shaped organ - the vagina. The duct of the accessory glands also opens into the unpaired oviduct.
The reproductive organs of the male consist of paired testes, paired vas deferens, an unpaired ejaculatory canal, accessory sex glands, and a copulatory organ. The testicles have a variety of shapes (bunch-shaped, lobulated, disc-shaped, convoluted, etc.) and consist of seminal tubes, or follicles, in which spermatozoa are formed. The seminal tubes flow into paired vas deferens, the ends of which often expand, forming seminal vesicles. They accumulate sperm before going outside, when mating, it enters the ejaculatory canal, which pushes the sperm out through the copulatory organ.
The accessory sex glands of males, usually from 1 to 3 pairs (in a cockroach, however, they are presented in the form of a large mushroom-shaped bundle of dozens of tubes), flow into the ejaculatory canal. The secret of the accessory glands protects the sperm from external influences during mating, for example, in bees. In some insects, the secretion of the accessory glands envelops a portion of sperm, forming a kind of capsule called a spermatophore. When mating, the male either inserts a spermatophore into the female's genital opening or attaches the spermatophore to it; the spermatozoa then pass from the spermatophore into the female genital tract. Spermatophoric fertilization has been noted in orthopterans, praying mantises, and some beetles.
