Lesson-game “General characteristics of the Insects class. Internal and external structure of insects Reproduction and development

Insects are the most numerous and widespread group of invertebrate animals. The number of species reaches one and a half million. The abundance and wide distribution of insects testifies to their perfect organization.

Their body consists of a head, chest and abdomen. The head was formed as a result of the fusion of six segments. On the head there are compound eyes and antennae that serve as sensory organs, as well as oral limbs. The chest consists of three segments. Three pairs of legs and two pairs of wings are attached to the chest. In some insects, the wings were reduced. The abdomen consists of 6–12 segments. The number of segments in the abdomen varies among different species. There are no legs on the abdomen, but the remains of the hind legs have turned into appendages located near the anus and genital openings.

The oral apparatus, depending on the feeding nature of the insect species, is varied (gnawing, piercing, sucking, licking).

The organs of locomotion are three pairs of legs attached to the chest. Most insects have two pairs of wings, but wingless insects (lice, fleas) are also known to have lost their wings due to their specific lifestyle.

The cuticular cover has compacted plates that are connected to each other by thin membranous sections, which provides the insect with body flexibility.

The brain of insects is well protected by the cuticular covering of the head.

In the outer integument there are various glands, the secretions of which ensure communication between individuals attached to another individual of the same species, or serve to scare away enemies due to a specific unpleasant odor.

The covers of almost all insects are colored. The coloring and pattern are specific to each species. The significance of color for insects is very great and varied. It makes insects less visible against the background of their habitats, can play a warning and deterrent role; in some cases, specific coloring can reduce heat transfer when the air temperature decreases and, conversely, increase heat transfer when the air temperature rises.

Insects have a highly developed nervous system. The ganglia of the ventral nerve chain, located in the abdomen, regulate the functioning of the respiratory and cardiac organs. Three ganglia of the ventral chain, located in the chest, innervate the legs and wings. The anterior part of the ventral nerve cord is highly developed and controls the functioning of the oral limbs and coordinates the activity of all organs of movement.

The cephalic ganglia merge and form the brain, which consists of three sections - anterior, middle and posterior. Each section performs its own function - the posterior section innervates the front part of the head, the middle section innervates the olfactory organs, and the anterior section innervates the eyes.

Neurosecretory cells are found in all parts of the central nervous system. The complexity of the nervous activity of insects depends on the development of the brain. In different insects, the brain differs not only in size, but also in the complexity of its structure. The complexity of the nervous activity of insects is manifested in the variety of instincts: obtaining and preserving food, relationships between males and females, building nests, the ability to quickly acquire conditioned reflexes, methods of protection from enemies, etc.

The muscular system of insects is well developed. It consists of a large number of striated fibers capable of very frequent contractions. This feature of the muscular system provides complex and varied movements of insects.

The legs of insects, depending on the functions they perform, have different structures - there are adjective legs, burrowing legs, running legs, etc. But all legs consist of the same parts, ending with claws.

The wings are thin but strong cuticular plates of various sizes, in which there are compacted veins consisting of chitinous cords, trachea, and nerves. The wings are driven by numerous muscles extending from the pectoral segments.

The nature of the flight of different types of insects is different - soaring or vibrating. The flight speed is also different.

The color of blood in insects is often yellowish. Blood transfer is carried out due to the energetic work of the heart, located on the dorsal side of the body and which is a tube consisting of a number of interconnected chambers. Hormones enter the bloodstream that affect the vital processes and development of insects.

The energetic vital activity of insects is ensured by intensive metabolic processes. In this case, a large amount of oxygen is consumed, the transfer of which is carried out by a special respiratory system, consisting of a large number of tracheas branching throughout all parts of the body. Oxygen enters the trachea along with air through complexly arranged spiracles located in insects on the sides of the chest and abdomen. The flow of air into and out of the respiratory system is carried out and regulated by the active work of the abdominal muscles and obturator structures of the trachea.

In many flying insects, the main longitudinal trunks of the trachea are greatly expanded and play the role of air sacs.

Intense respiration of insects is accompanied by the release of large amounts of heat.

The main excretory organs in insects are the Malpighian vessels - thin tubes with single-layer walls consisting of epithelial cells. In different insect species, the number of Malpighian vessels is different and ranges from several dozen. With the help of the Malpighian vessels, uric acid and its salts are released from the body through the hindgut. Alkaline dissimilation products are not removed from the body, but are absorbed by special cells - nephrocytes, in which they are stored until the end of the insect’s life. Many products of metabolic processes accumulate in the fat body, which fills the spaces between organs and performs various functions. The fat body also accumulates reserve substances (proteins, fats, carbohydrates) consumed by insects during periods of intense activity.

The oral apparatus of different insects is different. It can be gnawing (cockroaches, beetles, dragonflies), gnawing-sucking or lapping (bees, bumblebees), piercing-sucking (bugs, mosquitoes, aphids), sucking (butterflies).

The digestive system of insects is quite advanced and ensures the extraction, processing and assimilation of various nutritious foods. In obtaining food, an important role is played by the oral limbs, which originate from modified forelegs. The digestive system of insects consists of three sections. The anterior section includes the oral apparatus, the digestive tube beginning with the oral cavity. The ducts of the salivary glands open into the oral cavity, the secretions of which moisten food and act as enzymes. The oral cavity passes into a short pharynx and connects with the esophagus, the posterior part of which in many animals expands into a crop, used as a place for storing and partially processing food. The esophagus of many insects passes into the muscular stomach, where mechanical processing of food is carried out. The anterior section of the digestive system of insects ends with the muscular stomach.

The middle section of the digestive system of insects is represented by a not very long intestine, in which very complex and important processes occur - digestion and absorption of breakdown products. Insects do not have a liver, but the walls of the midgut secrete active enzymes that cause the rapid breakdown of proteins, carbohydrates, and lipids. The midgut has many lateral processes and a folded structure of the walls, which ensures an increase in its surface.

The long and voluminous hindgut represents the third section of the insect digestive system. The hindgut absorbs water and soluble substances and produces feces. The anus opens at the posterior end of the body.

Reproduction in insects is only sexual. All insects are dioecious. Fertilization in most species of insects is internal, in a few species it is external-internal.

According to the nature of postembryonic development, all insects can be divided into two large groups. In some insects (locusts, aphids, bedbugs), larvae develop from eggs, similar to adult individuals, but differing in color, lack of wings, and underdevelopment of the genitals. They molt several times, grow and gradually become like adults.

In other insects (beetles, fleas, bees, butterflies, flies), larvae develop from eggs, leading a different lifestyle than adults, and not at all similar to them. Larvae become similar to adults only after a complete change in their organization. It occurs during the resting stage - the pupa, into which the larva turns as a result of the last molt. Larvae become similar to adults only after a complete change in their organization.

All insects are combined into two subclasses - primarily wingless and winged. The vast majority of insects, united in orders, belong to the winged subclass:

Mayflies are small insects; their larvae are eaten by fish.

Hemipterans or bugs - among them there are many pests of agricultural plants. Some of them, living in fresh water bodies, attack fish fry. Among them there are those that feed on the blood of humans, mammals, birds, and fish. There are carriers of pathogens of infectious diseases.

Orthoptera - these include grasshoppers, locusts, crickets, cockroaches. Among them there are many pests of agricultural crops.

Homoptera - these include aphids, phylloxera, leafhoppers, psyllids, and scale insects. Pests of garden, fruit, and field plants.

Coleoptera or beetles - many of them, using carrion, manure, and bird droppings for food, are good environmental health workers. Among them there are pests of cultivated plants, trees, food products, and predators that attack fish.

Hymenoptera - bees, bumblebees, ants, ichneumonriders, horntails, etc. They provide valuable products, protect the forest by eating pests, and pollinate plants. Among them there are also pests of conifers, cereals and cruciferous plants.

Lepidoptera or butterflies - among them there are those that provide valuable raw materials, pollinators of plants and pests of trees, crops, fruits, vegetables, etc.

The importance of insects in the life of our planet cannot be overestimated. Billions of invertebrate animals inhabiting all corners of the globe cannot but influence the living animal and plant world, as well as inanimate nature.

The importance of invertebrates for humans is great and varied.

Along with invertebrates that are beneficial to humans and the environment, there are also harmful ones. You have to fight them.

The number of insects that harm agriculture, horticulture, animal husbandry, gardening, and humans is small from the total number of all types of insects, but the damage they cause to the national economy is very significant. This is due to their extreme fertility and wide distribution on the planet.

Insects include pests of agricultural and garden crops, gardens and forests, food supplies, wooden and hydraulic structures. The leather industry is suffering from insects and their larvae, and the fish productivity of water bodies is decreasing.

There is not a single plant in nature that is not used by insects either for food or for habitat.

Many types of insects destroy grain crops (wheat, oats, barley), corn, strawberries, mint, mustard, and attack trees in gardens, forests, and parks. Among the pests are butterfly larvae, bark beetles, longhorned beetles, beetles, weevils, fleas (bread, mustard, beet, etc.). All of them feed on leaves, stems, roots, root crops, flowers, juices, and tissues of various plants.

Acacia false scale damages gooseberries, currants and fruit crops. The larvae suck the juice from the leaves of young shoots, the plants weaken and die if they are severely damaged.

The larvae of the raspberry bud moth, the raspberry beetle, and the weevil - the raspberry-strawberry flower beetle - infect the buds, buds, berries and shoots of raspberries. Damaged buds dry out, do not open and fall off.

Raspberry stem fly, shoot gallicea and raspberry stem gallicea infect young raspberry shoots. Their larvae penetrate into shoots, making ring-shaped passages. The tops of the shoots turn black and the shoots dry out.

Leaf aphids and leaf aphids feed on raspberry leaves and are carriers of viruses that cause raspberry disease - vein mosaic and leaf spot.

Caterpillars of the currant bud moth damage the buds and berries of all types of currants. The larvae of the narrow-bodied currant beetle feed on the pith of currant and gooseberry branches. Damaged branches in the spring lag behind in development, produce low yields and dry out.

Caterpillars of currant glass also feed on the pith of currant and gooseberry branches, as a result of which damaged branches wither and dry out. The pulp of currant and gooseberry leaves feeds on the caterpillars of the rose and currant moth, the gooseberry moth, and the yellow gooseberry sawfly. They also destroy both berries and young shoots. In damaged plants, the leaves wrinkle and curl into a tube, shoot growth is weakened, and the plants' winter hardiness is reduced.

Red, white, black currants and gooseberries are damaged by the pale-footed sawfly, stem and leaf currant gallicea, currant gall aphid, and willow scale insect.

Peas, beans and beans become unfit for consumption after they are damaged by pea, bean and legume caryopsis. Among barn pests, the omnivorous nylon beetle causes significant damage. It turns grain, alfalfa, figs, dates, peaches, pears, plums, cherries, raisins, grapes, corn, tomatoes, and fishmeal into dust.

Among the many enemies of apple trees there is a very dangerous aphid. This small insect is called the blood aphid. The larvae of this aphid overwinter on the tree. In the spring they crawl out onto the crown of the tree and begin to feed on its sap. Adults and their larvae often completely cover all branches, young shoots and the trunk of the tree. Pests pierce the bark and continuously suck all the nutrients from the tree. The damaged tree weakens and is colonized by bark beetles, phytopathogenic bacteria, fungi and lichens. The wood is destroyed and the tree dies.

The Colorado potato beetle feeds on gooseberry leaves, tomatoes, cabbage, oats, and potato leaves. The beetle overwinters in the soil. Females lay eggs on the underside of leaves. The larvae, feeding on potato leaves, completely destroy them, as a result of which the process of photosynthesis is disrupted, and this in turn leads to a sharp decrease in potato yield.

Many types of flies are pests of agriculture.

The larvae of Hessian and Swedish flies are pests of cereal plants. The green eye spoils barley, spring wheat, rye, and oats.

Cabbage, onion, carrot, and beet flies cause damage to vegetables. The melon fly spoils cucumbers, watermelons, and melons. The Mediterranean fruit fly is a pest of gardens and vegetable gardens. The adult fly lays eggs under the skin of the fruit. The larvae feed on the pulp of the fruit. The fruits rot and fall off.

Some types of flies cause spoilage of meat and fish, meat and fish products.

Wasps can feed on nectar, honey from dead bees, various waste and meat, among them there are also species that feed on garden crops. They gnaw and spoil fruits and infect them with phytopathogenic microorganisms.

Ants are ubiquitous. They can be found in the garden, in the forest, in the field, in the meadow and swamp, in a person’s home.

They are found in desert and temperate climate zones. There are about twenty thousand species around the world. Ants live in colonies. Most of them are predators, feeding on eggs, larvae and adult insects. But many ants feed on seeds and plant sap. Fruiting bodies and mycelium of mushrooms. There are carpenter ants that spoil wood and cause harm to the forest.

These include fleas, lice, flies, mosquitoes, horseflies, mosquitoes, bedbugs, etc. Insects that are carriers of pathogenic microorganisms (bacteria, fungi, rickettsia, viruses, protozoa) can be divided into two groups, one of which combines mechanical carriers (ants, wood lice, cockroaches, cockroaches, flies) pathogens, and the other, feeding on the blood of a person, animal, bird, transmits the pathogen in place with its saliva. This method of transmitting the pathogen is called transmissible.

1. External building.

2. Internal structure.

About 1 million species are known. Habitats are varied.

1. External construction

The body of insects is divided into three tagmas: head (cephalon), thorax

(thorax) and abdomen (abdomen).

Head

Consists of an acron and 4 (according to some sources 5 or even 6) segments. It is covered with a chitinous capsule and is movably connected to the thoracic region. There are three types of positioning of the head relative to the body: prognathic, hypognathic and opisthognathic. The head capsule has several sections. The anterior facial part is occupied by the fronto-clypeal section. It consists of the frontal (frons) - frontal sclerite and clypeus (clypeus). The upper lip (labrum) is attached to the clypeus. The second section is the parietal. It consists of two parietal (vertex) sclerites and an occipital (occiput). The occiput is surrounded by the foramen magnum. The lateral sections are located under the compound eyes and are called cheeks (genae).

On the head there are eyes (complex, sometimes simple) and antennae of various structures, as well as mouthparts. The mouthparts of insects vary. Variation in structure is associated with the variety of food consumed by these animals. The initial type of oral apparatus is gnawing (orthopteroid). It is found in insects of many orders (cockroaches, Orthoptera, dragonflies, beetles, etc.). It consists of the following elements: upper lip, mandibles, maxillae, lower lip and hypopharynx. The lapping (bees, bumblebees) is formed by the upper lip, mandibles, in the maxilla the outer chewing blade (galea) is developed and elongated, which forms the upper and part of the lateral surface of the proboscis, the lower lip is represented by an elongated palp (palpi), which forms the lower and part of the lateral surface of the proboscis . Inside the proboscis there is a tongue formed by the internal (glossae) lobes of the lower lip. The sucking mouthparts (Lepidoptera) include the upper lip; in a few

1. External structure

vitels (toothed moths) mandibles, lower lip in the form of a small platform with palps, proboscis formed by elongated external chewing lobes of the maxillae. The piercing-sucking mouthparts (mosquitoes, bedbugs) include the entire set of oral limbs, but they have lost their original shape, most of them have turned into stilettos, used for piercing the integument of animals and plants. The lower lip in this device serves as a case. The licking (filtering) oral apparatus is characteristic of flies; the labellum of the lower lip are well developed in it; mandibles and maxillae are absent.

Thoracic region

Formed by 3 segments, locomotor organs are associated with it: legs and wings. The limb of an insect consists of a coxa, trochanter, tibia, tarsus, and pretarsus. There are several types of limbs. The wings are located on the second (mesothorax) and third (methothorax) segments. There are usually 2 pairs of wings, less often (dipterans, fan wings) 1 pair. The second, in this case, is small in size and transformed into halteres. The wings are lateral folds of the integument, originating from the paranotum. They are two-layered, nerves, tracheas, and hemolymph pass through them. The following types of wings are distinguished: mesh, membranous, rigid (elite), semi-rigid (hemieliter). The wings have a system of longitudinal and transverse veins. The longitudinal veins of the wing are: costal (C), subcostal (Sc), radial (R), medial (M), cubital (Cu) and anal (A). In flight, insects use either one or both pairs of wings. Depending on which pair of wings is used in flight, insects are divided into bimotor, anterior- and rear-motor. Many insects, being dipterous, fly on one pair of wings. This phenomenon is called flight dipterization.

Abdominal

Segmented, most of the insect’s internal organs are connected to it. The maximum number of segments in a department is 11, usually there are fewer. The abdominal segment is formed by tergite, sternite and pleural membranes. The abdomen is devoid of real limbs; some insects have modified ones: cerci, styli, ovipositors, sting, jumping fork.

Veils

Represented by the cuticle, hypodermis and basement membrane. The cuticle includes the epicuticle and procuticle. The procuticle consists of two

LECTURE 19. EXTERNAL AND INTERNAL STRUCTURE OF INSECTS

1. External structure

layers: exocuticle and endocuticle. The hard body cover limits the growth of the insect. Molting is typical for insects. The integument bears appendages. They are divided into structural and sculptural. The color of the insect is associated with the integument. Coloring is divided into chemical (pigment) and structural (physical). The significance of color for an insect is direct (impact on internal processes) and indirect (impact on other animals). Types of coloring: cryptic - coloring of a resting pose, warning, scaring, mimicry. Derivatives of the hypodermis are wax glands, odorous glands, poisonous glands, varnish glands and others.

2. Internal structure

Muscular system

It is characterized by complexity and a high degree of differentiation and specialization of its individual elements. The number of muscle bundles often reaches 1.5–2 thousand. According to histological structure, almost all insect muscles are striated. Muscles are divided into skeletal (somatic), which ensure the mobility of the body and its individual parts in relation to each other, and visceral (internal). Skeletal muscles are usually attached to the inner surfaces of the cuticular sclerites. There are four groups of somatic muscles: head, pectoral, wing and abdominal. The wing group is the most complex; the muscles of this group in Hymenoptera, dipteran insects and some others are capable of an extraordinary frequency of contractions (up to 1000 times per second); these are the so-called asynchronous muscles. This frequency of contractions is associated with the phenomenon of multiplication of the response to stimulation, when a muscle responds to one nerve impulse with several contractions. Visceral muscles are connected to internal organs.

Fat body

It is a loose tissue penetrated by tracheae. Color is variable. Functions: accumulation of nutrients, absorption of metabolic products, oxidation of the fat body produces metabolic water, which is especially important in conditions of moisture deficiency. There are four categories of cells in the fat body: trophocytes (the most numerous, they accumulate nutrients), urate cells (uric acid accumulates), mycetocytes (they contain symbiotic microorganisms) and chromocytes (the cells contain pigment).

LECTURE 19. EXTERNAL AND INTERNAL STRUCTURE OF INSECTS

2. Internal structure

Body cavity

The body cavity of insects, like other arthropods, is mixed. It is divided by diaphragms into 3 sinuses: the upper (pericardial), which houses the heart, the lower (perineural), which houses the abdominal nerve chain, and the visceral sinus occupies the largest volume. The digestive, excretory, and reproductive systems are connected to this sinus. The respiratory system is located in all sinuses of the body cavity.

Digestive system

Three sections: foregut, midgut and hindgut. Between the foregut and midgut there is a cardiac valve, and between the midgut and hindgut there is a pyloric valve. The foregut is represented by the pharynx, esophagus, goiter, and mechanical stomach. Depending on the food consumed, variations in the structure are possible: there is no goiter or stomach. The crop is a temporary place for food; digestion partly occurs here; The function of the stomach is to grind (grind) food. The pharynx of insects that feed on liquid food is muscular and functions as a pump. The salivary glands open into the oral cavity, usually near the base of the lower lip. The enzymes contained in saliva provide the initial stages of digestion. In blood-sucking insects, saliva contains substances that prevent blood clotting - anticoagulants. In some cases, the salivary glands change their function (in caterpillars they turn into spinning glands). Digestion and absorption of food occurs in the middle (small) intestine. In some insects (cockroaches, etc.), several blind protrusions of the intestine flow into the initial part of the intestine - pyloric appendages - they increase the absorption surface. The walls of the midgut form folds - crypts. The type of digestive enzymes depends on the feeding regime of the insects. The secretion of enzymes in insects is holocrine and merocrine. The epithelium of the midgut in many insects secretes a peritrophic membrane around the intestinal contents, the role of which is important in the processes of digestion and absorption of nutrients. In addition, it protects the epithelium of the midgut from mechanical damage. The hind (rectum) intestine is often quite long and is divided into several sections. This is where most insects have rectal glands. Functions of the department: formation and removal of excrement, absorption of water from the food mass, digestion of food with the help of symbionts (typical of the larvae of some types of insects). The intestinal sections are separated by valves that prevent the backflow of food. The anterior and middle sections are separated by the cardiac valve, the middle and posterior sections by the pyloric valve.

Insects are true terrestrial invertebrates. The class has about 1 million species. The body of insects is clearly divided into head, chest, and abdomen. The head is formed by four segments. The thoracic region consists of three segments, each with one pair of limbs. The second and third segments on the dorsal side usually bear a pair of wings. The abdomen consists of 8-12 segments.

general characteristics

A typical representative of this class is the cockchafer. Its length is 2-2.5 cm. The body shape is cylindrical. Color - light brown. There are characteristic triangular white spots on the sides of the abdomen.

The cockchafer is a typical representative of the class Insects

The cockchafer's head contains sensory organs and mouth parts. The sensory organs of insects are two compound eyes. In front of the eyes there is a pair of antennae with expanded plates at the end, which act as olfactory organs.

The organs of touch and taste are the palps. They are found in pairs on the lower lip and lower jaws. The oral organs include the upper and lower lips, upper and lower jaws. The upper lip and upper jaws are single-membered. The lower lip and lower jaws are polynomial.

Based on the nature of the structure of the oral organs in insects, they distinguish between gnawing, piercing-sucking, lapping, cutting-sucking and other oral apparatus, which is associated with the variety of food consumed by different insects.

The May beetle belongs to the order of beetles or Coleoptera. In insects belonging to this order, the first pair of wings has turned into hard elytra, which serve as a cover for the second pair of membranous wings used in flight.

Before taking off, the cockchafer lifts its elytra, moves them to the side and spreads the membranous wings folded under them. During flight, the wings perform the same role as the load-bearing planes of an airplane, and the elytra perform the same role as an airplane propeller.

The cockchafer's legs are equipped with sharp claws, which help it cling tightly to leaves and twigs.

The beetle's abdomen consists of 8 segments; they are visible only from the underside, since almost its entire upper part (with the exception of the pointed tip of the abdomen) is hidden by the elytra.

Insect feeding. The cockchafer feeds on young tree leaves. Swallowed food passes through the esophagus into a voluminous crop, and from it into the stomach, where it is ground by chitinous denticles. In the intestine, crushed food is finally digested and absorbed, and undigested remains enter the hind intestine and are thrown out through the anus.

Respiratory system in insects represented by tracheas. These are numerous branching tubes into which air enters through special openings - spiracles, or stigmas. The trachea distributes air throughout the body, reaching all organs. The work of the respiratory organs of insects is connected with the work of the muscular system of the abdomen: when it contracts, air is pushed out of the trachea, and when the abdomen expands, fresh air enters them.

Insect circulatory system represented by the heart and blood vessels. The heart and aorta are located on the dorsal side. Due to the fact that there is an extensive network of tracheas, the circulatory system is poorly developed and lacks the function of an oxygen carrier. The fluid circulating through the circulatory system is called hemolymph. It contains white blood cells.

Excretory organs of insects- numerous tubes (Malpighian vessels) flowing into the border of the middle and hind intestines. Their lumen is filled with grains of uric acid - the main product of dissimilation in insects. In addition, the fat body has an excretory function. Uric acid also accumulates in it, although it is not removed from the body, so its concentration in the fat body increases with age. The fat body is the “kidney” of storage. However, the main function of the fat body is the accumulation of reserve nutrients: fat, glycogen, protein.

Nervous system of insects built according to the type of abdominal nerve chain, but can reach a very high level of development and specialization. The central nervous system includes the brain, the subpharyngeal ganglion, and the segmental ganglia of the ventral nerve cord located in the trunk. The brain has a very complex histological structure. In most insects, the ganglia of the ventral nerve cord are concentrated in the longitudinal direction.

May beetles reproduce sexually. The fertilized female burrows into the soil and lays eggs. Larvae develop in them and leave the egg shells at the end of summer. The larvae feed on humus.

In the fall, they penetrate deep into the soil, overwinter, and in the spring they rise to the soil surface and feed on the roots of herbaceous plants and pine seedlings throughout the summer. They overwinter again deep in the soil and only in the third summer the grown larvae are able to feed on the roots of shrubs and trees, as a result of which young trees often dry out.

The larva turns into a pupa only after it has overwintered for the third time and has greatly increased in size. This happens at the end of spring, and by autumn an ​​adult cockchafer emerges from it. At first, its soft covers are colorless, then they harden and become colored. After overwintering in the ground again, the beetles crawl to its surface in the spring. Massive summers of them occur in the spring months at dusk.

The main damage to forestry is caused not by adult beetles, but by their larvae. This is due to the fact that starting from the second year, they feed on tree roots and destroy young plants and seedlings.

The natural enemies of cockchafers are birds (starlings, rooks) and mammals (moles, bats). These birds and animals must be protected in every possible way.

General characteristics of the class. This is the most numerous class, including more than 1 million species. By origin, this is a group of true terrestrial animals. Insects have inhabited a wide variety of terrestrial habitats, soil, fresh water bodies, and coastal seas. The wide variety of habitats in the terrestrial environment contributed to the speciation and wide dispersal of this large group of arthropods.

The abdominal region of different groups of insects consists of an unequal number of segments (mostly 9-10) and is devoid of real limbs.

Skin Insects are structured similarly to those of arachnids. The skin contains various pigments that determine the color of insects. Coloring can be protective or warning. The numerous hairs present on the surface of the chitinous cuticle perform the function of touch. The integument is abundantly supplied with various glands - waxy, odorous, spinning, poisonous, etc., the secretions of which play an important role in the life of insects.

The striated muscles reach special development in the thoracic region, providing rapid movements of the wings (from five to a thousand beats per second) and limbs.

Like other arthropods, digestive system insects consists of three divisions. The structure of the foregut is modified depending on the food specialization of insects. Insects that feed on solid food have a muscular stomach (Fig. 11.14). In those who feed on liquid food, the oral cavity is transformed into a system of canals, and the stomach is of a sucking type. Salivary glands can be converted into spinning glands (butterfly caterpillars) or contain blood anticoagulants (in blood-sucking forms). In the hind intestine of most insects there are special glands designed to absorb water from undigested food debris.

In addition to the Malpighian vessels (from 2 to 200), the fat body also serves as an excretory organ, the main function of which is to store nutrients necessary for the development of eggs during wintering. The end product of nitrogen metabolism in insects is uric acid, which is secreted in the form of crystals, which is due to the need to retain water in their gel.

Breath insects are carried out exclusively with the help of a highly branched tracheal system. The openings of the spiracles are located on the lateral surfaces of the chest and abdomen. The spiracles are equipped with special valves that regulate the flow of air into them, the movement of which occurs through contractions of the abdomen. Insects living in water - water flies and bedbugs - are forced to periodically rise to the surface of the water to store air.

Rice. 11.14. Scheme of the structure of cockroach organs: 1 — esophagus; 2 — goiter; 3 — muscular stomach; 4 - midgut; 5 —excretory tubes; b — lateral trachea; 7 — ventral nerve cord.

Circulatory system In insects, due to the structural features of the respiratory organs, it is poorly developed and does not differ fundamentally from that of other arthropods (Fig. 11.15). The blood is colorless or yellowish, rarely red, which depends on the hemoglobin dissolved in it (for example, in mosquito larvae).

Nervous system, like other arthropods, it is built according to the type of peripharyngeal nerve ring and ventral nerve cord. The suprapharyngeal ganglion reaches a high level of development, especially in social insects (bees, ants, termites), transforming into a “brain” with three sections: anterior, middle and posterior. It innervates the eyes and antennae. The behavior of social insects is complex.

The sense organs of insects are well developed. The visual organs of an adult are represented by compound eyes, to which simple ocelli are sometimes added, located on the forehead and crown.

Some insects have color vision (butterflies, bees). The organs of balance and hearing are arranged in a unique way. Insects have a keen sense of smell, allowing them to find food and sexual partners. The organs of touch are most often located on the antennae, and the organs of taste are located on the oral limbs. A highly developed nervous system and sophisticated sensory organs determine the complex behavior of insects, especially social ones. It is determined by instincts, which are innate complexes of reactions.

Fig 11 .15 . Insect circulatory system: 1 — aorta; 2 — pterygoid muscles; 3 — dorsal vessel — "heart".

Types of insect development. Insects are dioecious, most of them with well-defined sexual dimorphism. The gonads are paired; males often have a copulatory organ. The eggs are rich in yolk and are laid in the external environment. After leaving the egg, the development of the insect organism occurs with incomplete or complete transformation (metamorphosis).

In insects with incomplete metamorphosis, the eggs hatch into larvae that are similar in appearance to the adult insect, but differ from it in their smaller size and underdeveloped wings and reproductive system. With each moult, they become more like their adult form. On the contrary, in insects with complete transformation, development proceeds with a consistent change of forms, completely different from one another. A worm-like larva hatches from the egg (in a butterfly it is called a caterpillar), which crawls, eats a lot, molts several times and becomes larger with each molt. As a result of the last larval molt, a pupa is formed that does not move or feed. Pupae of different orders of insects with complete metamorphosis have different structures, but what they have in common is the destruction of the anatomical structures of the larva and the use of this material to build the organs of an adult insect. Regulation of all stages of metamorphosis occurs with the participation of special hormones.

In insects with complete metamorphosis, the larva (caterpillar) and the adult differ not only in appearance, but also in the method and objects of nutrition. Thus, the caterpillar of the cabbage butterfly feeds on leaves, while the adult butterfly sucks flower nectar. In addition, larvae and adult insects inhabit different habitats. For example, a mosquito larva lives in fresh water bodies and feeds on algae and protozoa, while an adult mosquito (female) lives on land and sucks the blood of humans and other mammals. These differences in food sources and habitats reduce intraspecific competition, allowing insects to thrive.

Orders of insects. The class Insects includes a large number of orders. The basis for their identification is the structure of the wings, mouthparts and type of development. The characteristics of the main orders are presented in Table. 11.1.

Table 11.1. Main orders of insects.

The squad and its representatives	Characteristic signs	Meaning
1	2	3
Insects with incomplete metamorphosis
Dragonflies (large rocker, beauties, arrows, etc.)	Two pairs of wings (identical in the suborder Homoptera and somewhat different in representatives of the suborder Heteroptera) with a fine network of veins. Large, compound eyes converging at the crown. Gnawing mouthparts.	Being voracious predators, they destroy a large number of insect pests.
Orthoptera (grasshoppers, crickets, locusts, mole crickets)	The forewings are rigid with almost parallel longitudinal veins. The hind wings are wider with radially diverging longitudinal veins. Gnawing mouthparts.	Most representatives of the order are plant pests. Locusts, eating leaves and stems, damage crops. Grasshoppers cause damage to orchards and vineyards. Mole crickets, burrowing in the soil, damage the roots of plants.
Hemiptera, or Bugs (tortoise bugs, bed bugs, water striders, etc.)	Half of each elytra from its base is rigid and consists of a thick layer of chitin, and the other half is thinner, membranous. Some bugs (bed bugs, etc.) have reduced wings. The mouthparts are piercing-sucking type. Many species have a scent gland, which is why they have an unpleasant odor.
Insects with complete metamorphosis
Coleoptera, or Beetles (chafer beetles, click beetles, weevil beetles, bread beetles [kuzka], leaf beetles [Colorado beetle], bark beetles, swimming beetles, ground beetles, ladybugs, dung beetles, etc.)	The first pair of wings - hard elytra - covers the second pair of membranous wings. The mouthparts are gnawing.	Many of the beetles harm plants; chafers eat leaves, and their larvae eat tree roots. Click beetle larvae are called wireworms. They feed on the underground parts of potatoes and cereals. The Colorado potato beetle and its larvae eat potato leaves. The larvae of the weevil, the apple blossom beetle, destroy the ovaries of the flower, and the larvae of the beet weevil destroy the roots of the beet. Among the beetles there are also useful ones. These are predatory beetles (ground beetles and beetles) that hunt silkworm caterpillars. Ladybugs and their larvae feed on aphids. Dung beetles and their larvae, eating manure, are a kind of orderlies.
Lepidoptera, or Butterflies (cabbage white, hawthorn, codling moth, codling moth, house moth, silkworms)	Two pairs of very large wings compared to the insect’s body, painted in different colors. The color of the wings depends on the color and arrangement of the scales. The veins on the wings are located longitudinally. With the exception of some moths, butterflies have sucking mouthparts.	Butterfly larvae, eating above-ground parts of plants, cause harm. Cabbage white larvae eat the leaves of cabbage and other cruciferous vegetables. The larvae of hawthorn moth, codling moth and codling moth cause damage to fruit trees. House moth larvae feed on the wool of fabrics or furs and damage clothing, carpets, and upholstery. Pine silkworm larvae, eating pine needles, harm pine forests; Ringed silkworm larvae damage orchards. While causing harm at the larval stage, adult butterflies produce benefits by pollinating plants. The benefit of butterflies is that they are food for birds. Among butterflies there are also domesticated forms. These are oak and mulberry moths. Their caterpillars have highly developed silk glands that secrete silk thread. The caterpillar wraps itself with this thread before pupation. The silky cocoon serves as protection for the pupa from unfavorable conditions, and for humans as raw material for producing silk.
Hymenoptera (riders, sawflies, bees, wasps, bumblebees, ants, etc.)	The hind wings are always smaller than the front wings. Both pairs are transparent with relatively sparse longitudinal and transverse veins. The oral apparatus in most species is gnawing, while in stinging animals (bees) it is of the gnawing-sucking type. Bees, wasps, and some ants have a sting, which is a modified ovipositor. The lifestyle is different. Some (riders, sawflies, some wasps) live alone, others (bees, ants, some wasps) live in large families and are social insects. Between individuals Within a family there is a division of labor.	Hymenoptera are of great importance as plant pollinators. The honey bee produces wax, bee venom, and jelly, which are used in medicine and perfumery. Bee honey is also useful. Riders are of great benefit. By laying eggs in the body of larvae and eggs of many harmful insects, they help humans in the fight against them. Wasps are also useful in this regard: by storing food for their larvae, before laying eggs, they paralyze and drag V burrows of caterpillars of many harmful insects. Among the Hymenoptera there are also pests. Female sawflies have a saw-like ovipositor, which they use to saw through the eggs of the plant to lay eggs. The larvae that emerge from the eggs eat the leaves of the plants.
Diptera (flies, gadflies, horseflies, mosquitoes, midges, mosquitoes, etc.)	The hind pair of wings is reduced. Their remains turned into halteres. The front pair of wings is strongly narrowed at the base. The mouthparts are of the licking (fly) and piercing-sucking (mosquito) type.

The role of insects in nature, their practical significance. Insects, with their diversity and huge numbers, play an important role in nature and human life. They are plant pollinators, destroy harmful representatives of this class and act as orderlies. Some beneficial insects - bees, silkworms - have been domesticated by humans. At the same time, the damage caused by insects is also great. Depending on the object of attack, harmful insects are divided into several groups: pests of the field, garden, vegetable garden, barn pests, disease carriers.

In order to protect plants from insects, various methods of controlling them are used. Widely applied collection insects using trapping ditches, rings, traps, insect traps (mechanical method), etc. In addition, the fight is also carried out using a chemical method, in which insects are exposed to poisons. But the use of chemicals leads to the poisoning of soil, water, and the destruction of both harmful and beneficial insects. Therefore, recently a biological method of control has gained recognition, in which humans use natural enemies of insects: insectivorous birds, insect predators (ground beetles, ladybugs, etc.). Trichogramma ichneumon is artificially bred to combat the codling moth.

Material from the site. Encyclopedia of Beekeeping

Insects- a class of invertebrate arthropods that arose about 410 million years ago. According to the traditional classification, together with centipedes they belong to the subphylum trachea-breathers. The name of the class comes from the verb “to cut” (to cut) and is a tracing paper from the French “ insecte"(Latin insectum, Wed Greek ἔντομον with the same meaning), meaning “animal with notches.” The body of insects is covered with a chitinized cuticle, forming an exoskeleton, and consists of three sections: head, thorax and abdomen. In many groups of insects, the second and third segments of the thorax each bear a pair of wings. There are three pairs of legs, and they are attached to the thoracic region. The body sizes of insects range from 0.2 millimeters to 30 centimeters or more.

The science that studies insects is called entomology.

Taxonomy

Latin name Insecta has the formal authorship of Carl Linnaeus by virtue of the rules of the International Code of Zoological Nomenclature, according to which the date of publication of the 10th edition of Linnaeus' System of Nature () is the original priority date for all names of zoological taxa. In relation to typified names of species, genera, families and intermediate ones, the rules of the International Code of Zoological Nomenclature apply, but for such untypified names as Insecta, they are not distributed. As a result, the name "Insecta" has been used in the scientific literature for a wide variety of taxa. Initially, since the time of Aristotle, this name applied to terrestrial arthropods (sexapods, arachnids and others), but not to crustaceans. Linnaeus put crustaceans in class Insecta, So Insecta according to Linnaeus approximately corresponds to the current taxon Arthropoda(arthropods). J. B. Lamarck belonged to the class Insecta some winged insects. Other authors have used the title "Insecta" in one meaning or another, intermediate between Linnaean and Lamarckian. The most traditional is to use the name "Insecta"(William Alford Leach, 1815) - meaning six-legged; but also in modern scientific literature the name "Insecta" used in at least three or four different meanings. Term Hexapoda used as another designation Insecta, especially in cases where primitive wingless insects ( Apterygota) are not considered true insects. In old world and Russian literature, “insects” most often refer to a broad group that includes primarily wingless insects and all Pterygota(sometimes the name is also used Hexapoda). In the modern sense, class Insecta accepted in a narrower scope. Two-tailed, springtails and bessyazhkovyh scientists or contrasted with insects, forming a separate class Entognatha, or are considered independent classes.

Number of species

As of August 2013, scientists have described 1,070,781 biological species of insects, including 17,203 fossil species. Estimates of the true total number of insect species range from about 2 million to about 8 million. Every year, at least 7000-7500 species of insects new to science are described. Among the four dozen modern and extinct orders, the 5 largest stand out: Coleoptera (392,415 species), Diptera (160,591), Lepidoptera (158,570), Hymenoptera (155,517) and Hemiptera (104,165).

External structure

The body of insects is divided into three segmented sections: head, chest And abdomen. Each segment is divided into four parts - the upper half ring is called tergite, the lower semiring is called sternite, side walls - pleurites. When denoting the relative position of body parts and organs with the term “dorsal” ( dorsalis) denote the upper side of the body, and "ventral" ( ventralis) - bottom side. There are also mesosome (in ants from three thoracic segments and the first abdominal segment of the propodeum) and metasoma (petulus and abdomen).

A distinctive feature of insects is the presence of a chitinous exoskeleton, which is the outer covering of the body and limbs. The cuticle covering the body forms a dense outer exoskeleton, but in some cases it is soft and thin. A hard exoskeleton creates a number of advantages: it protects the body from mechanical stress, drying out, etc., and increases resistance to deformation. It also has a number of disadvantages (for example, high energy costs associated with molting). The exoskeleton is divided into separate scutes - sclerites (sclerites), connected by thinner sections of the cuticle. The surface of the integument usually bears various kinds of outgrowths, folds, spines, scales, bristles, small hairs - chaetoids. The cuticle also includes movable skin hairs - Kheti.

The coloring of the body and its parts in insects is very diverse. There are structural and pigment colors. Structural is associated with some specific features of the surface structure of the cuticle (microscopic ribs, plates, scales, etc.), which create the effects of interference, diffraction and light dispersion - metallic shiny shades. Pigmented coloration is caused by pigments, which are often contained in the cuticle, less often in the cells of the hypodermis or fat body. Many insects exhibit a combination of these two types of coloration. Most types of insects have very bright patterns on various parts of their body. Insects with daytime activity, confined to plant substrates, are predominantly brightly colored. Many species that move along the soil surface or are active at night are characterized by a uniform and predominantly dark body color. The color can be one color or consisting of a combination of several colors, mainly two or three, less often more colors. The general background may have spots, stripes or any other pattern.

Respiratory system

Sense organs

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

Vision

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

Hearing

The perception of sounds transmitted through a solid substrate is carried out in insects by vibration receptors located in the shins of the legs near their articulation with the thigh. Many insects are highly sensitive to vibrations of the substrate on which they are located. The perception of sounds through air or water is carried out by phonoreceptors. Diptera perceive sounds using Johnston organs. The most complex auditory organs of insects are tympanic organs. The number of sensilla included in one tympanic organ varies from 3 (some butterflies) to 70 (locusts) and even up to 1500 (in song cicadas).

Many insects are ectotherms (animals for which the environment is the source of heat), while others can be endotherms (they independently produce heat inside their body through biochemical processes). Endothermic insects are more accurately described as heterotherms because they are not entirely endothermic. When heat is produced, different parts of an insect's body may have different temperatures; for example, moths produce heat in their chest for flight, but their abdomen remains relatively cool.

Features of behavior

Intraspecific communication

Contact signals

Scout bees can tell members of their family, using a special dance, the path to the found source of food. Bees dance in the dark, inside the hive. The language of bee dances was deciphered by Karl von Frisch, who received the Nobel Prize in 1973 for his work in this area. Contact signals (touching by antennae) play an important role during trophallaxis.

Pheromones

Pheromones are used by insects for a wide variety of purposes. They cause a response in individuals of the same species. There are two functional groups of pheromones: releasers and primers. Releaser pheromones cause an immediate behavioral response. They are widespread in insects, mediating sexual behavior, the formation of aggregations, and the distribution of individuals in space at a high population density of one species. The most important are sex pheromones, which facilitate the meeting of males and females. Primer pheromones cause slow reactions and, by promoting physiological changes, either inhibit or excite behavioral responses.

Orientation in space

The most important means of orientation for many insects are visual, sound stimuli and smells. Honey bees use solar orientation to guide other bees in their hive in the direction of a nectar source (the circling and wagging dance of bees). Having the ability to navigate along the plane of polarization of light, insects can determine the position of the Sun even in cloudy weather. Bees and wasps orient themselves by remembering the location of their nest relative to the surrounding objects (trees, bushes, stones, etc.). Before flying away, many solitary wasps circle around the nest, remembering the main milestones on the way to it. In the case of bees, if you move the hive to the side at a distance of less than one meter, then the bees returning with a bribe look for it in the same place and do not immediately find it in the new one.

Ecology

Relationships with other organisms

In the course of long evolution, insects have developed diverse