How many orders of insects? §29

Habitats, structure, lifestyle

Insects are the largest class of animals. It includes more than 1 million species. Insects live everywhere: in forests, gardens, meadows, fields, vegetable gardens, on livestock farms, in human homes. They can be found in ponds and lakes, on the body of animals.

The body of insects consists of a head, thorax and abdomen. There are a pair of compound eyes on the head, a pair of antennae, three pairs of legs on the chest, and most have one or two pairs of wings, and spiracles on the sides of the abdomen.

Insects differ in the shape of their body parts, the size of their eyes, the length and shape of their antennae and other characteristics. Their antennae, mouthparts, and legs are especially diverse. Some insects have lamellar antennae (many beetles), others have filamentous antennae (grasshoppers), others have feathery or club-shaped antennae (butterflies), etc. The mouthparts can be gnawing, like those of cockchafers, piercing-sucking, like mosquitoes, sucking, like butterflies, etc. The hind legs of grasshoppers are jumping, while those of swimming beetles are swimming; The front legs of the mole cricket are digging. All these and other structural features have developed in insects in connection with adaptation to certain living conditions.

Rice. Bombardier (beetle). Family - ground beetles

The internal structure of insects is mainly related to the respiratory, excretory and nervous systems. The respiratory organs of insects - the trachea - are highly branched. U small insects Gas exchange occurs by diffusion. Large insects ventilate the trachea (when the abdominal walls relax, air is sucked into the trachea, and when contracted, it is released into the external environment). The excretory organs of insects are numerous tubes, the free ends of which are closed. The excretory products entering them flow into the posterior intestine. Insects have fat cells that store nutrients and water. Some substances unnecessary for the body are deposited in them.

Differences in the nervous system of insects are associated with the enlargement of the suprapharyngeal nerve ganglion (it is often called the brain), a decrease in the number and enlargement of the nodes of the ventral nerve chain. The more complex structure of the nervous system is manifested in the complexity of insect behavior. A bee, for example, having found flowering nectar-bearing plants, upon returning to the hive, crawls on the honeycomb, “dances,” describing certain figures, by which other bees establish the direction to the place of honey collection. The ants close the entrances to the anthill at night, bring wet needles to the surface, and after drying, drag them into the depths of the anthill.

Types of insect development

Insects are dioecious animals. In some insects (locusts, bedbugs), fertilized eggs laid by females develop into larvae that are similar in appearance to adults. Feeding heavily, they grow, molt several times and become adult insects. In other insects (butterflies, beetles, flies), the larvae are not similar in appearance and nutrition to adults. The larvae of the cabbage butterfly, for example, are worm-like and do not feed on nectar, like butterflies, but on cabbage leaves. Their mouthparts are not sucking, but gnawing. After several molts, the caterpillars turn into pupae that do not feed or move, but complex changes occur under their chitinous cover. After some time, the pupa’s body cover bursts and an adult insect emerges.

Development that occurs in three phases, and the insect larvae are similar to adults, is called incomplete transformation. The development of insects, which occurs in four phases (including the pupal phase), and the larvae do not resemble adults, is called complete metamorphosis.

Development with transformation makes it possible for insects to survive under unfavorable living conditions ( low temperature, lack of food) at one or another less vulnerable stage of development. Insects with complete metamorphosis have the greatest advantages. Their larvae do not compete with adults: they usually use different food and develop in different habitats.

The main orders of insects

In the class of insects there are from 30 to 40 orders. The largest of them are the orders of Orthoptera, Homoptera, Hemiptera, Coleoptera, Lepidoptera, Hymenoptera, and Diptera.

Orders of insects with incomplete metamorphosis. The order Orthoptera includes locusts, grasshoppers, crickets, and mole crickets. They are characterized by a chewing mouthpart, two pairs of longitudinally veined wings, and a (usually) hopping hind pair of legs. Many Orthoptera produce and perceive sounds (in grasshoppers, the sound apparatus is located on the front wings, and the auditory apparatus is on the shins of the front legs). Their antennae are thread-like. Females of many species have an ovipositor. The order Homoptera includes aphids, cicadas, etc., feeding on plant sap, having a piercing-sucking proboscis and 2 pairs of transparent wings.

The order Hemiptera, or bugs, includes terrestrial and aquatic insects with piercing-sucking mouthparts, two pairs of wings (semi-rigid upper and membranous lower), and highly developed scent glands. Of the representatives of this order, the most common are green forest bugs and long-legged water strider bugs. The same order includes the bedbug, which feeds on the blood of people and animals living in human housing.

Orders of insects with complete transformation. The order Coleoptera, or beetles, includes insects with rigid front wings and membranous hind wings. In most beetles, when at rest, hard wings completely cover the membranous wings and protect them from damage. Beetles have gnawing mouthparts. The order Coleoptera includes May beetles, ground beetles, ladybugs, weevils.

Butterfly Papilio demoleus. Photo: Jeevan Jose

The vast majority of insects of the order Lepidoptera, or butterflies, are characterized by two features: scaly cover on two pairs of wings and a sucking mouthpart, usually coiled. The antennae of daytime butterflies are usually club-shaped, while those of nighttime butterflies are feathery. Worm-like butterfly larvae (caterpillars), in addition to three pairs of jointed legs, have false legs - outgrowths of the body. Caterpillars have gnawing mouthparts.

Diptera - flies, mosquitoes, horseflies, etc. - have one pair of membranous wings. The hind wings are transformed into flask-shaped organs - halteres. The mouthparts of dipterans are piercing-sucking or licking. Larvae have no legs. They develop in water, soil, rotting remains of plants, living animals and corpses.

Task 1. Fill out the table.

Features of the external structure of insects depending on their type of development.

Representatives of insect groups: mole cricket - orthoptera, apple aphid - homoptera, bed bug - bedbugs, stag beetle - coleoptera, urticaria butterfly - lepidoptera, forest wasp, squeak mosquito - Hymenoptera.

Task 2. Write down the numbers of insect names in accordance with their type of development.

Insect names:

1. Swimming beetle

2. Honey bee

3. Squeaky mosquito

4. Dragonfly rocker

5. Butterfly hives

6. Green grasshopper

7. Locust

Development with incomplete transformation: 4, 6, 7

Development with complete transformation: 1, 2, 3, 5

Task 3. Write down the numbers of the correct statements.

Statements:

1. Cabbage butterfly caterpillars and adult butterflies have different types of mouthparts.

2. Cabbage butterfly larvae pupate underground.

3. Insect pupae actively feed and develop into adults.

4. Development with complete transformation takes place in the following sequence: egg - larva - adult insect.

5. During development with incomplete transformation, there is no larval stage.

6. Grasshoppers and locusts are characterized by development with incomplete transformation.

7. Flies, butterflies, mosquitoes and dragonflies develop with complete transformation.

8. Locust larvae look similar to adult locusts.

Correct statements: 2, 3, 4, 8

Task 4. Insects reproduce fantastically quickly: in five months, the offspring of one housefly could reach 7.6 billion individuals. But this doesn't happen. Explain why.

Many flies die before reaching sexual maturity (they are eaten or killed), which means they cannot leave offspring, but they also feed on fly larvae, so the flies do not reach such a large number of individuals.

Task 5. Fill out the diagram.

Type arthropod:

Class Insects:

1. Group Orthoptera. Signs: 2 pairs of wings; legs - jumping, mouth apparatus - gnawing.

2. Group Homoptera. Signs: mouthparts - piercing-sucking type, wings folded into a house.

3. Group Bugs, or Hemiptera. Signs: the wings are hard in front and soft in the back, the oral apparatus is piercing-sucking.

4. Group Butterflies, or Lepidoptera. Signs: soft chitinous scales on the wings, sucking mouthparts.

5. Group Beetles, or Coleoptera. Signs: hard elytra, gnawing mouthparts.

6. Group Diptera insects. Signs: one pair of wings, mouthparts cutting-sucking and licking.

7. Hymenoptera group. Signs: two pairs of membranous wings.

Insects are the youngest of the invertebrates and the most numerous class of animals, numbering more than 1 million species. They have completely mastered all habitats - water, land, air. They are characterized by complex instincts, omnivorousness, high fertility, and for some, a social way of life.

During development with transformation, the habitat and food sources are divided between larvae and adults. The evolutionary path of many insects is closely related to flowering plants.

More highly developed insects are winged. Gravedigger beetles, dung beetles, and consumers of plant residues play an important role in the cycle of substances in nature, and at the same time, insects - pests of agricultural plants, gardens, food supplies, leather, wood, wool, and books - cause great damage.

Many insects are carriers of pathogens that cause diseases in animals and humans.

Due to the reduction natural biogeocenoses and the use of pesticides total number insect species are declining, so 219 species are listed in the Red Book of the USSR.

General characteristics of the class

The body of adult insects is divided into three sections: head, thorax and abdomen.

• Head, consisting of six fused segments, is clearly separated from the chest and is movably connected to it. On the head there is a pair of segmented antennae or antennae, mouthparts and two compound eyes; many also have one to three simple ocelli.

  Two compound, or facet, eyes are located on the sides of the head; in some species they are very well developed and can occupy most surface of the head (for example, in some dragonflies, horse flies). Each compound eye contains from several hundred to several thousand facets. Most insects are blind to the color red, but they can see ultraviolet radiation and are attracted to it. This feature of insect vision is the basis for the use of light traps, emitting most of the energy in the violet and ultraviolet regions, to collect and study the ecological characteristics of nocturnal insects (some families of butterflies, beetles, etc.).

  Oral apparatus consists of three pairs of limbs: upper jaws, lower jaws, lower lip (fused second pair of lower jaws) and upper lip, which is not a limb, but is an outgrowth of chitin. The oral apparatus also includes a chitinous protrusion of the floor of the oral cavity - the tongue or hypopharynx.

  

  

  

  Depending on the method of feeding, the oral organs of insects have a different structure. Distinguish following types oral apparatus:

  • gnawing-chewing - the elements of the oral apparatus have the form of short hard plates. Observed in insects that feed on solid plant and animal food (beetles, cockroaches, orthoptera)
  • piercing-sucking - the elements of the oral apparatus have the appearance of elongated hair-like bristles. Observed in insects that feed on plant cell sap or animal blood (bugs, aphids, cicadas, mosquitoes, mosquitoes)
  • licking-sucking - the elements of the oral apparatus have the form of tubular formations (in the form of a proboscis). It is observed in butterflies that feed on flower nectar and fruit juice. In many flies, the proboscis is highly transformed; at least five of its modifications are known, from a piercing-cutting organ in horse flies to a soft “licking” proboscis in flower flies that feed on nectar (or in carrion flies that feed on liquid parts of manure and carrion).

  Some species do not feed as adults.

  The structure of the antennae, or cubs, of insects is very diverse - filamentous, bristle-shaped, serrated, comb-shaped, club-shaped, lamellar, etc. There is one pair of antennae; they bear the organs of touch and smell, and are homologous to the antennules of crustaceans.

  The sense organs on the antennae of insects tell them not only their condition environment, they help to communicate with relatives, find a suitable habitat for themselves and their offspring, as well as food. The females of many insects attract males using scents. Male lesser night peacocks can smell a female from several kilometers away. Ants recognize females from their anthill by smell. Some types of ants mark the path from the nest to the food source thanks to odorous substances that are released from special glands. With the help of their antennae, ants and termites smell the scent left by their relatives. If both antennae pick up the scent to the same extent, then the insect is on the right track. Attractant substances released by female butterflies ready to mate are usually carried by the wind.

• Breast insects consists of three segments (prothorax, mesothorax and metathorax), to each of which a pair of legs is attached to the ventral side, hence the name of the class - hexapods. In addition, in higher insects the chest bears two, less often one, pair of wings.

  The number and structure of limbs are characteristic features class. All insects have 6 legs, one pair on each of the 3 thorax segments. The leg consists of 5 sections: coxa (plow), trochanter (trochanter), femur (femur), tibia (tibia) and articulated tarsus (tarsus). Depending on the lifestyle, the limbs of insects can vary greatly. Most insects have walking and running legs. In grasshoppers, locusts, fleas and some other species, the third pair of legs is of the jumping type; In mole crickets that make passages in the soil, the first pair of legs are digging legs. U aquatic insects, for example, in the swimming beetle, the hind legs are transformed into rowing or swimming legs.

  Digestive system presented

  • The foregut, starting from the oral cavity and dividing into the pharynx and esophagus, the posterior section of which expands, forming a goiter and a chewing stomach (not for everyone). In consumers of solid foods, the stomach has thick muscular walls and carries chitinous teeth or plates from the inside, with the help of which food is crushed and pushed into the midgut.

    The foregut also includes salivary glands (up to three pairs). The secretion of the salivary glands performs a digestive function, contains enzymes, and moistens food. In bloodsuckers, it contains a substance that prevents blood clotting. In bees, the secretion of one pair of glands is mixed in the crop with flower nectar and forms honey. In worker bees, the salivary glands, the duct of which opens into the pharynx (pharyngeal), secrete special protein substances (“milk”), which feed the larvae that turn into queens. In butterfly caterpillars, caddisfly larvae and hymenoptera, the salivary glands are transformed into silk-secreting or spinning glands, producing silky thread for the production of cocoons, protective formations and other purposes.

  • The midgut at the border with the foregut is covered from the inside with glandular epithelium (pyloric outgrowths of the intestine), which secretes digestive enzymes (insects lack liver and other glands). Absorption of nutrients occurs in the midgut.
  • The hindgut receives undigested food debris. Here water is sucked out of them (this is especially important for desert and semi-desert species). The hindgut ends with the anus, which leads excrement out.

  

  Excretory organs represented by Malpighian vessels (from 2 to 200), which look like thin tubes flowing into digestive system on the border between the midgut and hindgut, and the fat body, which functions as “storage kidneys”. The fat body is loose tissue located between the internal organs of insects. It has a whitish, yellowish or greenish color. Cells of the fat body absorb metabolic products (uric acid salts, etc.). Next, the excretory products enter the intestines and are excreted together with excrement. In addition, the cells of the fat body accumulate reserve nutrients - fats, proteins and the carbohydrate glycogen. These reserves are spent on the development of eggs during wintering.

  Respiratory system- trachea. This is a complex branching system of air tubes that directly deliver oxygen to all organs and tissues. On the sides of the abdomen and chest there are most often 10 pairs of spiracles (stigmas) - holes through which air enters the trachea. Large main trunks (tracheas) begin from the stigmas, which branch into smaller tubes. In the chest and anterior part of the abdomen, the trachea is expanded and forms air sacs. Tracheas penetrate the entire body of insects, entwine tissues and organs, and enter individual cells in the form of tiny branches - tracheoles, through which gas exchange occurs. Carbon dioxide and water vapor are removed to the outside through the tracheal system. Thus, the tracheal system replaces the functions of the circulatory system in supplying tissues with oxygen. The role of the circulatory system is reduced to the delivery of digested food to the tissues and the transfer of decay products from the tissues to the excretory organs.

  Circulatory system in accordance with the characteristics of the respiratory organs, it is relatively poorly developed, not closed, consists of the heart and a short, unbranched aorta extending from the heart to the head. The colorless liquid containing white blood cells circulating in the circulatory system is called hemolymph, in contrast to blood. It fills the body cavity and the spaces between organs. The heart is tube-shaped, located on the dorsal side of the abdomen. The heart has several chambers capable of pulsating, into each of which a pair of holes equipped with valves opens. Through these openings, blood (hemolymph) enters the heart. The pulsation of the heart chambers is caused by the contraction of special pterygoid muscles. Blood moves in the heart from the rear end to the front, then enters the aorta and from it into the head cavity, then washes the tissues and flows through the cracks between them into the body cavity, into the spaces between the organs, from where through special openings (ostia) it enters the heart. The blood of insects is colorless or greenish-yellow (rarely red).

  Nervous system reaches an exceptionally high level of development. It consists of the suprapharyngeal ganglion, peripharyngeal connectives, the subpharyngeal ganglion (it was formed as a result of the fusion of three ganglia) and the abdominal nerve cord, which in primitive insects consists of three thoracic ganglia and eight abdominal ones. In higher groups of insects, adjacent nodes of the ventral nerve chain merge by combining three thoracic nodes into one large node or abdominal nodes into two or three or one large node (for example, in true flies or lamellar beetles).

  The suprapharyngeal ganglion, often called the brain, is especially complex. It consists of three sections - anterior, middle, posterior and has a very complex histological structure. The brain innervates the eyes and antennae. In its anterior section the most important role played by such a structure as the mushroom bodies - the highest associative and coordinating center of the nervous system. The behavior of insects can be very complex and has a clearly defined reflex nature, which is also associated with significant development of the brain. The subpharyngeal node innervates the oral organs and the anterior intestine. The thoracic ganglia innervate the organs of movement - legs and wings.

  Insects are characterized by very complex forms of behavior, which are based on instincts. Particularly complex instincts are characteristic of the so-called social insects - bees, ants, termites.

  Sense organs reach an exceptionally high level of development, which corresponds to a high level of general organization of insects. Representatives of this class have organs of touch, smell, vision, taste and hearing.

  All sense organs are based on the same element - the sensilla, consisting of one cell or a group of sensitive receptor cells with two processes. The central process goes to the central nervous system, and the peripheral one goes to the outer part, represented by various cuticular formations. The structure of the cuticular sheath depends on the type of sensory organs.

  The organs of touch are represented by sensitive hairs scattered throughout the body. The olfactory organs are located on the antennae and mandibular palps.

  The organs of vision play a leading role for orientation in the external environment, along with the organs of smell. Insects have simple and compound (compound) eyes. Compound eyes consist of a huge number of individual prisms, or ommatidia, separated by a light-proof layer. This eye structure gives “mosaic” vision. Higher insects have color vision (bees, butterflies, ants), but it differs from human vision. Insects perceive mainly the short-wave part of the spectrum: green-yellow, blue and ultraviolet rays.

  Reproductive organs are located in the abdomen. Insects are dioecious organisms; they have well-defined sexual dimorphism. Females have a developed pair of tubular ovaries, oviducts, accessory gonads, spermatic receptacle and often an ovipositor. Males have a pair of testes, vas deferens, ejaculatory duct, accessory sex glands and copulatory apparatus. Insects reproduce sexually, most of them lay eggs, there are also viviparous species, in which the females give birth to live larvae (some aphids, gadflies, etc.).

  After a certain period of embryonic development, larvae emerge from the laid eggs. Further development of larvae in insects of various orders can occur with incomplete or complete transformation (Table 16).

  Life cycle. Insects are dioecious animals with internal fertilization. According to the type of postembryonic development, insects are distinguished with incomplete (in highly organized) and complete (in higher) metamorphosis (transformation). Complete metamorphosis includes the stages of egg, larva, pupa and adult.

  In insects with incomplete metamorphosis, a young individual emerges from the egg, similar in structure to the adult insect, but differing from it in the absence of wings and underdevelopment of the genital organs - a nymph. They are often called larvae, which is not entirely accurate. Its living conditions are similar to adult forms. After several molts, the insect reaches its maximum size and turns into adult form- imago.

  In insects with complete metamorphosis, the eggs hatch into larvae that differ sharply in structure (they have a worm-like body) and habitat from the adult forms; Thus, mosquito larvae live in water, and imaginal forms live in the air. The larvae grow and go through a series of stages, separated from each other by molts. During the last molt, a stationary stage, the pupa, is formed. The pupae do not feed. At this time, metamorphosis occurs, the larval organs undergo decay, and imago organs develop in their place. Upon completion of metamorphosis, a sexually mature, winged individual emerges from the pupa.

  Table 16. Development of insects	Type of development
  	Superorder I. Insects with incomplete metamorphosis	Superorder 2. Insects with complete metamorphosis
  Number of stages	3 (egg, larva, adult insect)	4 (egg, larva, pupa, adult insect)
  Larva	Looks like an adult insect external structure, lifestyle and nutrition; differs in smaller size, wings are absent or incompletely developed	Differs from an adult insect in external structure, lifestyle and nutrition
  Doll	Absent	Yes (in the immobile pupa, histolysis of larval tissues and histogenesis of adult tissues and organs occurs)
  Squad	Order Orthoptera (Orthoptera)	Order Coleoptera, or beetles (Coleoptera) Order Lepidoptera, or butterflies (Lepidoptera) Order Hymenoptera (Hymenoptera)

  Class Overview

  The insect class is divided into more than 30 orders. The characteristics of the main groups are given in Table. 17.

  Beneficial insects

  Honey bee or house bee [show] A family usually lives in a hive, which consists of 40-70 thousand bees, of which one is the queen, several hundred male drones, and the rest are worker bees. The queen is larger in size than other bees; she has well-developed reproductive organs and an ovipositor. Every day the queen lays from 300 to 1000 eggs (on average this is 1.0-1.5 million over a lifetime). Drones are slightly larger and thicker than worker bees, and they do not have wax glands. Drones develop from unfertilized eggs. Worker bees are underdeveloped females that are unable to reproduce; their ovipositor turned into an organ of defense and attack - a sting. The sting consists of three sharp needles, between them there is a channel for removing the poison produced in a special gland. In connection with feeding on nectar, the gnawing mouthparts have changed significantly; when eating, they form a kind of tube - the proboscis, through which nectar is absorbed using the muscles of the pharynx. The upper jaws also serve to build honeycombs and other construction work. The nectar is collected in the enlarged crop and turns into honey, which the bee regurgitates into the cells of the honeycomb. There are numerous hairs on the bee's head and chest; when the insect flies from flower to flower, pollen sticks to the hairs. The bee cleans pollen from the body, and it accumulates in the form of a lump, or pollen, in special recesses - baskets on the hind legs. Bees drop pollen into the cells of the honeycomb and fill it with honey. Beebread is formed, which the bees feed the larvae with. On the last four segments of the bee's abdomen there are wax glands, which outwardly look like light spots - speculums. The wax comes out through the pores and hardens in the form of thin triangular plates. The bee chews these plates with its jaws and builds honeycomb cells from them. The wax glands of a worker bee begin to secrete wax on the 3-5th day of its life, reach its greatest development on the 12-28th day, then decrease and degenerate. In the spring, worker bees begin collecting pollen and nectar, and the queen lays one fertilized egg in each cell of the comb. After three days, larvae hatch from the eggs. Worker bees feed them “milk” for 5 days, a substance rich in proteins and lipids, which is secreted by the maxillary glands, and then bee bread. After a week, the larva weaves a cocoon inside the cell and pupates. After 11-12 days, a young worker bee emerges from the pupa. Some days she does various jobs inside the hive - cleans the cells, feeds the larvae, builds honeycombs, and then begins to fly out for a bribe (nectar and pollen). In slightly larger cells, the queen lays unfertilized eggs, from which drones develop. Their development lasts several days longer than the development of worker bees. The queen lays fertilized eggs in large queen cells. From them larvae hatch, which the bees constantly feed with “milk”. From these larvae young queens develop. Before the young queen emerges, the old one tries to destroy the queen cell, but the worker bees prevent her from doing this. Then the old queen with some of the worker bees flies out of the hive - swarming occurs. A swarm of bees is usually transferred to a free hive. The young queen flies out of the hive along with the drones, and returns after fertilization. Bees have a well-developed suprapharyngeal node, or brain, which is distinguished by the strong development of mushroom-shaped, or stalked, bodies, with which the complex behavior of bees is associated. Having found flowers rich in nectar, the bee returns to the hive and begins to describe figures on the honeycomb that resemble the number 8; At the same time, her abdomen oscillates. This peculiar dance signals to other bees in which direction and at what distance the bribe is located. Complex reflexes and the instincts that determine the behavior of bees are the result of a long historical development; they are inherited. People have been raising bees in apiaries since ancient times. The collapsible frame hive was an outstanding achievement in the development of beekeeping; it was invented by the Ukrainian beekeeper P.I. Prokopovich in 1814. The beneficial activity of bees lies primarily in the cross-pollination of many plants. With bee pollination, the yield of buckwheat increases by 35-40%, sunflower - by 40-45%, and cucumbers in greenhouses - by more than 50%. Bee Honey- a valuable food product, it is also used for medicinal purposes in diseases of the gastrointestinal tract, heart, liver, and kidneys. Royal jelly and bee glue (propolis) are used as medicinal preparations. Bee (wasp) venom is also used in medicine. Beeswax is widely used in various industries industry - electrical engineering, metallurgy, chemical production. The annual global honey harvest is about 500 thousand tons. [show] The silkworm has been known to people for over 4 thousand years. It can no longer exist in nature; it is bred in artificial conditions. Butterflies don't feed. Sedentary, whitish female silkworms lay 400-700 eggs (the so-called greena). From them, in special rooms on racks, caterpillars are hatched and fed with mulberry leaves. The caterpillar develops within 26-40 days; During this time she sheds four times. An adult caterpillar weaves a cocoon from silk thread, which is produced in its silk gland. One caterpillar secretes a thread up to 1000 m long. The caterpillar wraps this thread around itself in the form of a cocoon, inside which it pupates. A small part of the cocoons are left alive - later butterflies hatch from them and lay eggs. Most cocoons are killed by hot steam or exposure electromagnetic field ultra-high frequency (in this case, the pupae inside the cocoons heat up to 80-90 ° C in a few seconds). Then the cocoons are unwound on special machines. More than 90 g of raw silk is obtained from 1 kg of cocoons.

  If it were possible to accurately calculate the harm and benefit of insects for National economy, then perhaps the benefits would significantly outweigh the losses. Insects provide cross-pollination of about 150 species of cultivated plants - garden, buckwheat, cruciferous, sunflower, clover, etc. Without insects, they would not produce seeds and would die themselves. The aroma and color of higher flowering plants were developed in the process of evolution as special signals to attract bees and other pollinating insects. Insects such as burying beetles, dung beetles, and some others are of great sanitary importance. Dung beetles were specially brought to Australia from Africa, because without them, a large number of manure, which interfered with grass growth.

  Insects play a significant role in soil formation processes. Soil animals (insects, centipedes, etc.) destroy fallen leaves and other plant debris, assimilating only 5-10% of their mass. However, soil microorganisms decompose the excrement of these animals faster than mechanically crushed leaves. Soil insects, along with earthworms and other soil inhabitants, play a very important role in mixing it. Lacquer bugs from India and Southeast Asia produce a valuable technical product - shellac; other species of bugs produce valuable natural paint carmine.

  Harmful insects

  Many types of insects damage agricultural and forest crops; up to 3,000 species of pests have been registered in Ukraine alone.

  [show] Adult beetles eat young tree leaves in spring (they eat leaves of oak, beech, maple, elm, hazel, poplar, willow, walnut, fruit trees). Females lay eggs in the soil. The larvae feed on thin roots and humus until autumn, overwinter deep in the soil, and the following spring continue to eat roots (mostly herbaceous plants). After the second winter in the soil, the larvae begin to feed on the roots of trees and shrubs; young plantings with an underdeveloped root system may die due to damage. After the third (or fourth) wintering, the larvae pupate. Depending on the geographical latitude locality and climatic conditions, the development of May Khrushchev lasts from three to five years. [show] The Colorado potato beetle began damaging potatoes in 1865 in North America in the state of Colorado (hence the name of the pest). After the First World War it was introduced to Europe and quickly spread east to the Volga and the North Caucasus. Females lay eggs on potato leaves, 12-80 eggs per clutch. Larvae and beetles feed on leaves. In a month, a beetle can eat 4 g, a larva - 1 g of leaves. If we consider that on average a female lays 700 eggs, then the second generation of one female can destroy 1 ton of potato leaves. The larvae pupate in the soil, and adult beetles overwinter there. In Europe, unlike North America, no natural enemies Colorado potato beetle, which would restrain its reproduction. Common beet weevil [show] Adult beetles eat sugar beet seedlings in the spring, sometimes completely destroying the crops. The female lays eggs in the soil, the larvae feed on the roots and root crops of sugar beets. At the end of summer, the larvae pupate in the soil, and the young beetles overwinter. Bug harmful turtle [show] The bug bug harms wheat, rye and other grains. Adult bedbugs overwinter under fallen leaves in forest belts and bushes. From here in April-May they fly to winter crops. At first, bedbugs feed by piercing stems with their proboscis. Then the females lay 70-100 eggs on the leaves of the cereals. The larvae feed on the cell sap of stems and leaves, and later move to ovaries and ripening grains. Having pierced the grain, the bug secretes saliva into it, which dissolves the proteins. Damage causes the grain to dry out, reduce its germination capacity and deteriorate its baking qualities. [show] The forewings are light brown, sometimes almost black. They show a typical “scoop pattern”, represented by a kidney-shaped, round or wedge-shaped spot edged with a black line. The hind wings are light gray. The antennae of males are weakly combed, those of females are thread-like. Wingspan 35-45 mm. The caterpillars are earthy gray in color, with a dark head. The Fall Armyworm caterpillar in the fall damages (gnaws) mainly seedlings of winter cereals (hence the name of the pest), to a lesser extent vegetable crops and root vegetables; in the southern regions it harms sugar beets. Adult caterpillars overwinter burrowed into the soil in fields sown with winter crops. In spring they pupate quickly. Butterflies emerging from pupae in May fly at night and at dusk. Females lay eggs on millet and row crops - sugar beets, cabbage, onions, etc. and in places with sparse vegetation, so they are often attracted to plowed fields. Caterpillars destroy sown grains, gnaw plant seedlings in the root collar area, and eat leaves. Very gluttonous. If 10 caterpillars live on 1 m 2 of crops, then they destroy all the plants and “bald patches” appear in the fields. At the end of July they pupate; in August, second-generation butterflies emerge from the pupae and lay eggs on weeds on the stubble or seedlings of winter crops. One female winter armyworm can lay up to 2,000 eggs. In Ukraine, two generations of winter armyworm develop during the growing season. [show] One of our most common butterflies. The upper side of the wings is white, the outer corners are black. Males have no black spots on the forewings; females have 2 black round spots and 1 club-shaped spot on each wing. The hind wings of both males and females are the same - white, with the exception of a black wedge-shaped spot at the anterior edge. The underside of the hind wings is a characteristic yellowish-green color. Wingspan up to 60 mm. The body of the cabbage plant is covered with thick, very short hairs, giving it a velvety appearance. The variegated coloring of the caterpillars is a warning that they are inedible. The caterpillars are bluish-green, with yellow stripes and small black dots, and the abdomen is yellow. In cabbage butterfly caterpillars, the poisonous gland is located on the lower surface of the body, between the head and the first segment. To defend themselves, they regurgitate a green paste from their mouths, which is mixed with secretions from the poisonous gland. These secretions are a caustic bright green liquid with which the caterpillars try to coat the attacking enemy. For small birds a dose of several individuals of these animals can be fatal. Swallowed cabbage caterpillars cause the death of domestic ducks. People who collected these insects with their bare hands sometimes ended up in the hospital. The skin on my hands became red, inflamed, my hands were swollen and itchy. Cabbage butterflies fly during the day in May-June and with a short break throughout the second half of summer and autumn. They feed on the nectar of flowers. Eggs are laid in clusters of 15-200 eggs on the underside of a cabbage leaf. In total, the butterfly lays up to 250 eggs. Young caterpillars live in groups, scrape off the pulp of cabbage leaves, while older ones eat up all the pulp of the leaf. If 5-6 caterpillars feed on a cabbage leaf, they eat it entirely, leaving only large veins. To pupate, the caterpillars crawl onto surrounding objects - a tree trunk, a fence, etc. During the growing season, two or three generations of cabbage whites develop. Cabbage grass is common in the European part former USSR, in Siberia this pest is not present, since butterflies cannot withstand severe winter frosts. The damage caused by cabbage is very great. Often many hectares of cabbage are completely destroyed by this pest. The flights of butterflies are interesting. When the butterflies reproduce strongly, they gather in large numbers and fly over considerable distances. [show] Willow woodborer - Cossus cossus (L.) The willow borer damages the bast and wood of poplars, willows, oaks, and other deciduous trees and fruit trees. Butterflies appear in nature starting from the end of June, mainly in July, and depending on the geographical location, in some places even before mid-August. They fly slowly in the late evening. A year lasts a maximum of 14 days. During the day they sit in a characteristic position with their chest reclining on the lower part of the trunk. Females lay eggs in groups of 15-50 pieces in bark cracks, damaged areas, cancerous wounds of trunks at heights of up to 2 m. Caterpillars hatch after 14 days. First, the bast tissues are eaten together. On older trees with thick bark in the lower part of the trunk, the caterpillars eat out individual long, irregularly running oval tunnels in the cross section only after the first wintering. The walls of the passages are destroyed by a special liquid and are brown or black. On thinner trunks with smooth bark, the caterpillars penetrate the wood earlier, usually within a month after hatching. The caterpillars push wood chips and excrement out through the lower hole. At the end of the growing season, when the leaves fall, the feeding of the caterpillars stops, which overwinter in the tunnels until the leaves bloom, i.e., until April - May, when the caterpillars continue to feed in separate tunnels again until autumn, overwinter one more time and finish feeding. They pupate either at the end of a circular passage, where a flight hole closed with wood chips is prepared in advance, or in the ground, near a damaged trunk, in a cocoon of wood chips. The pupal stage lasts 3-6 weeks. Before departure, the pupa, with the help of spines, protrudes halfway out of the flight hole or out of the cocoon, so that the butterfly can more easily leave the exuvium. The generation is maximally biennial. The willow woodborer is distributed throughout Europe, mainly in the middle and southern parts. It is found throughout the forest zone of the European part of Russia, in the Caucasus, Siberia, and also in Far East. Known in western and northern China and Central Asia. The butterfly's forewings are gray-brown to dark gray with a marbled pattern and vague gray-white spots, as well as dark transverse wavy lines. The hind wings are dark brown with matte dark wavy lines. The chest is dark on top, whitish towards the belly. The dark abdomen has light rings. The male has a wingspan of 65-70 mm, the female - from 80 to 95 mm. The female's abdomen is completed with a retractable, clearly visible ovipositor. The caterpillar is cherry-red immediately after hatching, and later turns flesh-red. The head and occipital plate are shiny black. An adult caterpillar is 8-11 cm (most often 8-9 cm), then it is a yellowish meat color, brown on top with a purple tint. The yellow-brown occipital scute has two dark spots. The breathing hole is brown. The egg is oval-longitudinal, light brown with black stripes, dense, 1.2 mm in size. Many insects, especially those with piercing-sucking mouthparts, carry pathogens of various diseases. Malarial plasmodium [show] Plasmodium falciparum, the causative agent of malaria, enters the human bloodstream through the bite of a malaria mosquito. Back in the 30s of the XX century. In India, over 100 million people fell ill with malaria every year; in the USSR, in 1935, 9 million malaria cases were registered. In the last century, malaria was eradicated in the Soviet Union, and the incidence rate has sharply decreased in India. The center of malaria incidence has moved to Africa. Theoretical and practical recommendations for the successful fight against malaria in the USSR and neighboring countries were developed by V. N. Beklemishev and his students. The nature of damage to plant tissue depends on the structure of the pest’s oral apparatus. Insects with gnawing mouthparts gnaw off or eat away sections of the leaf blade, stem, root, fruit or make tunnels in them. Insects with piercing-sucking mouthparts pierce the integumentary tissues of animals or plants and feed on blood or cell sap. They cause direct harm to a plant or animal, and also often carry pathogens of viral, bacterial and other diseases. Annual losses in agriculture from pests amount to about 25 billion rubles, in particular, damage from harmful insects in our country annually averages 4.5 billion rubles, in the USA - about 4 billion dollars. TO dangerous pests cultivated plants in the conditions of Ukraine include about 300 species, in particular beetles, click beetle larvae, mole crickets, corn beetles, Colorado potato beetles, common beet weevils, turtle bugs, meadow and stem moths, winter and cabbage cutworms, hawthorn, gypsy moth, ringed silkworm, codling moth, American white butterfly, beet root aphid, etc. Control of harmful insects To combat harmful insects, a comprehensive system of preventive measures has been developed, including agro- and forestry, mechanical, physical, chemical and biological. Preventive measures consist of observing certain sanitary and hygienic standards that prevent the mass reproduction of harmful insects. In particular, timely cleaning or destruction of waste and garbage helps reduce the number of flies. Draining swamps leads to a decrease in mosquito numbers. Great importance also has to observe the rules of personal hygiene (washing hands before eating, thoroughly washing fruits, vegetables, etc.). Agrotechnical and forestry activities, in particular weed control, correct crop rotations, proper preparation soil, the use of healthy and sedimentary material, pre-sowing seed cleaning, well-organized care of cultivated plants create unfavorable conditions for the mass reproduction of pests. Mechanical measures consist of the direct destruction of harmful insects manually or with the help of special devices: flytraps, adhesive tapes and belts, trapping grooves, etc. In winter, wintering nests of hawthorn and goldentail caterpillars are removed from trees in gardens and burned. Physical measures - use to kill some insects physical factors. Many moths, beetles, and dipterans fly towards the light. With the help of special devices - light traps - you can promptly learn about the appearance of certain pests and begin to fight them. To disinfect citrus fruits infected with the Mediterranean fruit fly, they are cooled. Barn pests are destroyed using high frequency currents. Therefore, integrated pest management, which involves a combination of chemical, biological, agrotechnical and other plant protection methods with the maximum use of agrotechnical and biological methods, is of particular importance. Integrated control methods provide for chemical treatments only in areas that threaten a sharp increase in pest numbers, and not for continuous treatment of all areas. With the aim of nature conservation, widespread use is envisaged biological agents plant protection.

Systematic position of the class, division into orders and families.

Insects are higher invertebrates.

The class has more than 1 million species.

Habitat: soil, air-ground, organisms of other living beings

The body is divided into sections: head, chest, abdomen.

The thoracic region consists of three segments; each carries one pair of legs. Consequently, insects are characterized by the presence of 3 pairs of limbs. The second and third segments, in addition, can carry a pair of wings. In some insects, both pairs of wings are well developed, but wingless insects are also known. The abdomen consists of 6 - 12 segments. The type of complex oral apparatus of insects is determined by the method of feeding and can be gnawing (beetles), sucking (butterflies), piercing-sucking (lice), licking (flies).

Body coverings and muscular system: have a chitinized cover, under which lies a single-layer hypodermal epithelium. The skin is rich in various glands: odorous, waxy, molting, etc. The muscles are striated.

Digestive system: mouth, pharynx, esophagus, crop, stomach, midgut, hindgut ends with anus. There are salivary glands and a gland that performs the functions of the liver and pancreas. Digestion and absorption of food occurs in the midgut.

Respiratory organs: trachea.

Excretory organs: Malpighian vessels and fat body.

Circulatory organs: the circulatory system is not closed, the tubular 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. Hemolymph circulates through the vessels.

Nervous system: abdominal nerve cord with a strong tendency to concentrate ganglia in the head section, so the suprapharyngeal ganglion is transformed into a “brain”, which has three sections (anterior, middle, posterior). There are sense organs: eyes (faceted, but can also be simple), balance, taste, touch and smell, and in some - hearing.

Reproductive system: insects are dioecious, sexual dimorphism is often pronounced. Gonads are paired (females have ovaries, males have testes). Sexual reproduction: with fertilization or parthenogenetic. Development is not direct: with complete metamorphosis (stages: egg - larva - pupa - adult) or incomplete metamorphosis (stages: egg - larva - adult).

The practical importance of insects is very great: pollinators of flowering plants, participate in soil formation processes, etc.

Among insects of medical importance, the following groups are distinguished:

The class Insects is divided into big number squads.

Spreading: ubiquitous

Morphology: Its body is flattened in the dorsal direction and covered with a highly extensible chitinous cover. The wings are completely reduced. Bedbugs attack humans at night, and spend the day in shelters - in furniture, behind wallpaper. The saliva of a bedbug contains a poisonous secretion, so its bites are painful; the transmission of pathogens by a bedbug to any infectious diseases has not been proven.

Medical and epidemiological significance:

Locally for a bite: hyperemia, swelling, itching, blisters. Absorb up to 7 ml of blood at a time. Bedbugs that live on birds and mammals can also attack humans - possibly by transmitting viruses that cause psittacosis. In tropical countries, bedbugs can transmit trypanosomes and a number of other pathogens.

Prevention: sanitary treatment of homes.

Insects are the most numerous class of animals; there are more than 1 million species. There are about 40 orders of insects, which are divided into two groups - insects with incomplete transformation and insects with complete transformation. Examples of insect orders with incomplete transformation are Orthoptera, Homoptera, and Hemiptera. Examples of orders with complete transformation are Coleoptera, Diptera, Lepidoptera, Hymenoptera.

Features of the order Orthoptera

Representatives: grasshoppers, locusts, crickets.

• Gnawing mouthparts.
• The wings of the first pair are narrow with longitudinal venation, the wings of the second pair are fan-shaped.
• The hind legs are of the jumping type (not for everyone).
• Many can make sounds and perceive them (grasshoppers make sounds with their front wings, and their hearing organ is on their legs).

Features of the order Homoptera

Representatives: aphids, copperheads, shield insects. Aphids live on the shoots of trees, shrubs and grasses, forming clusters. There are usually a lot of copperheads on the leaves of fruit trees.

• They feed on plant sap.
• Piercing-sucking mouthparts with proboscis.
• Two pairs of soft transparent wings (not for everyone).

Features of the order Hemiptera (bugs)

Representatives: green forest bugs, water strider bugs, bed bugs.

• They lead a terrestrial or aquatic lifestyle.
• Piercing-sucking mouthparts.
• A pair of semi-rigid upper wings and a pair of membranous lower wings.
• Scent glands are developed.

Features of the order Coleoptera (beetles)

Representatives: ladybugs, weevils, dung beetles, ground beetles, chafers.

• Rigid front wings protect the hind wings from damage.
• The mouthparts are gnawing type.

Features of the order Diptera

Representatives: flies, mosquitoes.

• One pair of membranous wings. The hind ones are modified into halteres.
• The oral apparatus is piercing-sucking or licking.
• Legless larvae that develop in soil, water, plant and animal remains.

Features of the order Lepidoptera (butterflies)

• Scaly cover of wings.
• The sucking mouthparts are coiled.
• Feathery (in nocturnal) or club-shaped (in diurnal butterflies) antennae.
• Butterfly larvae are caterpillars. They have body outgrowths - false legs. The mouthparts are gnawing type.

Features of the order Hymenoptera

Representatives: bees, wasps, ants, riders.

• Two pairs of membranous transparent wings.
• The mouthparts are gnawing or licking.
• Females have an ovipositor at the end of the abdomen, which in some species is transformed into a sting and is associated with poisonous glands.
• Worm-like, most often legless, larvae.