Wing movement in insects- the result of the work of a complex mechanism and is determined, on the one hand, by the peculiarity of the articulation of the wing with the body, and on the other, by the action of special wing muscles. IN general outline The basic mechanism of wing movement is presented as follows. The wing itself is a double-armed lever with arms of unequal length. The wing is connected to the tergite and lateral plate by thin and flexible membranes. Slightly moving away from the place of this connection, the wing rests on a small column-shaped outgrowth of the side plate, which is the fulcrum of the wing lever.
The powerful longitudinal and dorsoventral muscles located in the thoracic segments can lower or raise the tergite. When lowering, the latter puts pressure on the short shoulder of the wing and drags it down with it. As a result, the long arm, i.e. the entire load-bearing plane of the wing, moves upward. The rise of the tergite leads to the lowering of the wing plate. Small muscles attached directly to the wing are able to rotate it along the longitudinal axis, thereby changing the angle of attack. During flight, the free end of the wing moves along a rather complex trajectory. When lowered, the wing plate is horizontal and moves down and forward: a lifting force arises that holds the insect in the air. When moving up and back, the wing is positioned vertically, which creates a propelling effect.
The number of wing beats in 1 s varies greatly among different insects: from 5-10 (in large diurnal butterflies) to 500-600 (many mosquitoes); in very small midge mosquitoes this figure reaches 1000 vibrations per 1 s. In various representatives of insects, the fore and hind wings can be developed in to varying degrees. Only in more primitive insects (dragonflies) are both pairs of wings developed more or less equally, although they differ in shape. In beetles (order Coleoptera - Coleoptera) the front wings change into thick and hard elytra - elytra, which almost do not participate in flight and mainly serve to protect the dorsal side of the body. The real wings are only the hind wings, which in the resting state are hidden under the elytra. In representatives of the order of bugs, only the main half of the front pair of wings hardens, as a result of which this group of insects is often called the order Hemiptera. In some insects, namely in the whole order of dipterans, only the front pair of wings is developed, while only rudiments of the back ones remain in the form of so-called halteres.
The question of the origin of the wings not yet fully resolved. Currently, one of the most substantiated is the “paranotal” hypothesis, according to which the wings arose from simple motionless lateral outgrowths of the skin - paranotums. Such outgrowths are found in many arthropods (trilobites, crustaceans), in many fossil insects, and in some modern forms(termite larvae, some mantises, cockroaches, etc.). The transition from crawling to flying was perhaps served by a climbing lifestyle on trees, in which insects probably often jumped from branch to branch, which contributed to the further development of the lateral outgrowths of the chest, which initially served as load-bearing planes during parachuting or gliding flight. Further differentiation and separation of the outgrowths from the body itself led to the development of real wings, providing active propelling flight.
Abdomen- the last section of the body of insects. The number of segments included in its composition varies depending on different representatives class. Here, as in other groups of arthropods, a clear pattern emerges: the lower in evolutionary terms certain representatives stand, the more complete set of segments they have. And indeed, we find the maximum number of abdominal segments in the lowest cryptomaxillary (neg. Protura), the abdomen of which consists of 11 segments and ends with a clearly distinguishable telson. In all other insects, part of the segments is reduced (usually one or several last ones, and sometimes the very first one), so total number segments can be reduced to 10, and higher forms(some Hymenoptera and Diptera) up to 4-5.
The abdomen is usually devoid of limbs. However, due to the origin of insects from forms that had legs throughout the entire homonomically dissected body, rudiments of limbs or limbs that have changed their original function are often preserved on the abdomen. Yes, the squad Protura, the lowest representatives of wingless insects, have small limbs on the three anterior segments of the abdomen. The rudiments of the abdominal limbs are also preserved in open-jawed animals. Tyzanura have special appendages on all segments of the abdomen - styli, on which, like on runners, the abdomen slides along the substrate when the insect moves. One pair of styli at the posterior end of the body is also preserved in cockroaches. Very widespread, especially in more primitive forms (cockroaches, locusts, etc.), cerci - paired appendages of the last segment of the abdomen, which are also modified limbs. Apparently, the ovipositors, found in many insects and consisting of three pairs of elongated valves, also have a similar origin.
Covers of insects, like all other arthropods, consist of three main elements - the cuticle, hypodermis and basement membrane. The cuticle is secreted by cells of the hypodermis, which in cryptognathous insects often turns into syncytium. The cuticle of insects is three-layered. Unlike that of crustaceans, it bears an outer layer containing lipoproteinose complexes and preventing the evaporation of water from the body. Insects are land animals. It is interesting to note that in aquatic and soil forms that live in an atmosphere saturated with water vapor, the outer layer is either not expressed at all or is very poorly developed.
The mechanical strength of the cuticle is given by proteins hardened with phenols. They inlay the middle, main layer.
On the surface of the cuticle there are various outgrowths movably articulated with the surface of the body - thin hairs, scales, and bristles. Each such formation is usually the product of the secretion of one large hypodermal cell. The variety of forms and functions of hairs is extraordinary; they can be sensitive, integumentary, or poisonous.
Insect coloring in most cases depends on the presence of special coloring substances - pigments - in the hypodermis or cuticle. The metallic sheen of many insects is one of the so-called structural colors and has a different nature. The structural features of the cuticle determine the appearance of a number of optical effects, which are based on the complex refraction and reflection of light rays. The integument of insects has glands of various significance; they are unicellular and multicellular. These are stink glands (on the chest of bedbugs), protective glands (in many caterpillars), etc. The most common are molting glands. Their secretion, secreted during molting, dissolves the inner layer of the old cuticle without affecting the newly formed cuticular layers. Special wax glands in bees, mealybugs and some other insects secrete wax.
Muscular system insects are highly complex and high degree differentiation and specialization of its individual elements. The number of individual muscle bundles often reaches 1.5 - 2 thousand. Skeletal muscles, which ensure the mobility of the body and its individual parts in relation to each other, are usually attached to the inner surfaces of the cuticular sclerites (tergites, sternites, walls of the limbs). According to histological structure, almost all insect muscles are striated.
Insect muscles (primarily this refers to the wing muscles of higher groups of insects: Hymenoptera, Diptera, etc.) are capable of an extraordinary frequency of contractions - up to 1000 times per second. This is due to the phenomenon of multiplication of the response to stimulation, when a muscle responds to one nerve impulse with several contractions.
Richly branched tracheal network respiratory system supplies each muscle bundle with oxygen, which, along with a noticeable increase in the body temperature of insects during flight (due to the thermal energy released by working muscles), ensures a high intensity of metabolic processes occurring in muscle cells.
Digestive system It begins with a small oral cavity, the walls of which are formed by the upper lip and a set of oral limbs. In forms that feed liquid food, it is essentially replaced by channels formed in the proboscis and used to absorb food and conduct saliva - the secretion of special salivary glands. The walls of the upper part of the oral cavity and the tubular pharynx following it are connected to the walls of the head capsule with the help of powerful muscle bundles. The combination of these bundles forms a kind of muscle pump that ensures the movement of food into the digestive system.
The ducts of one or more (up to 3) pairs of salivary glands open into the back of the oral cavity, as a rule, near the base of the lower lip (maxilla II). The enzymes contained in saliva provide the initial stages of digestion. In blood-sucking insects (tsetse fly, some types of mosquitoes, etc.), saliva often contains substances that prevent blood clotting - anticoagulants. In some cases salivary glands dramatically change their function. In butterfly caterpillars, for example, they turn into spinners, which, instead of saliva, secrete a silky thread that is used to make a cocoon or for other purposes.
The digestive canal of insects, starting with the pharynx, consists of three sections: the foregut, middle and hindgut.
The foregut can be differentiated into several parts that differ in function and structure. The pharynx passes into the esophagus, which looks like a narrow and long tube. The posterior end of the esophagus often expands into a crop, especially developed in insects that feed on liquid food. In some predatory beetles, orthoptera, cockroaches, etc., another small extension of the foregut is located behind the crop - the chewing stomach. The cuticle lining the entire foregut in the chewing stomach forms numerous hard outgrowths in the form of tubercles, teeth, etc., facilitating additional grinding of food.
Next comes the midgut, where food is digested and absorbed; it looks like a cylindrical tube. At the beginning of the midgut, several blind intestinal protrusions, or pyloric appendages, often flow into it, which mainly serves to increase the absorption surface of the intestine. The walls of the midgut often form folds, or crypts. Typically, the epithelium of the midgut secretes a continuous thin membrane around the intestinal contents, the so-called peritrophic membrane.
The final digestion and absorption of nutrients occurs in the midgut.
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, for some - public image 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 of natural biogeocenoses and the use of pesticides, the total number of insect species is decreasing, therefore 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 red-blind, but see and are attracted to ultraviolet light. 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.).
The oral apparatus consists of three pairs of limbs: the upper jaws, the lower jaws, the lower lip (fused second pair of lower jaws) and the 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. The following types of oral apparatus are distinguished:
- 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 the state of the environment, they help them 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 of the 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. In aquatic insects, for example 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 are represented by Malpighian vessels (from 2 to 200), which look like thin tubes that flow into the digestive system at the border between the midgut and hindgut, and the fat body, which performs the function of “storage buds”. Fat body- 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, 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 permeate the entire body of insects, intertwine tissues and organs, and enter individual cells in the form of tiny branches - tracheoles, through which gas exchange occurs. Carbon dioxide and water vapor is 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, consisting 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 posterior end to the anterior, 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 plays a structure such as mushroom bodies - the highest associative and coordinating center nervous systems s. 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 in orientation in external environment along with the olfactory organs. 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.).
From eggs laid after certain period embryonic development the larvae emerge. Further development larvae in insects of various orders can occur with incomplete or complete transformation (Table 16).
Life cycle. Insects are dioecious animals with internal fertilization. Type postembryonic development Insects are distinguished with incomplete (in highly organized) and with 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 an adult form - an 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 Similar to an adult insect in 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, the eggs hatch into larvae. 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. For several days she performs various work 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 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 is a valuable food product; it is also used for medicinal purposes for diseases gastrointestinal tract, heart, liver, kidneys. Used as medicinal drugs royal jelly and bee glue (propolis). Bee (wasp) venom is also used in medicine. Beeswax widely used in various industries - electrical engineering, metallurgy, chemical production. The annual global honey harvest is about 500 thousand tons.
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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 grena). 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 molts 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 benefits of insects for the national economy, then perhaps the benefits would significantly exceed the losses. Insects provide cross-pollination for 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 South-East Asia They produce a valuable technical product - shellac, and other types of scale insects - the 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.
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- 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.
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Adult beetles eat young tree leaves in the 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 geographic latitude of the area and climatic conditions, the development of May beetle lasts from three to five years.
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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, there are no natural enemies of the Colorado potato beetle that would restrain its reproduction.
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 damages (gnaws) mainly seedlings of winter cereals in the fall (hence the name of the pest), in to a lesser extent vegetable crops and root crops; 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 moth is common in the European part of the former USSR; this pest is not found in Siberia, since the 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 the 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 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.
Dangerous pests of cultivated plants in 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. Compliance with the rules of personal hygiene (washing hands before eating, thoroughly washing fruits, vegetables, etc.) is also of great importance.
Agrotechnical and forestry measures, 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 methods of plant protection with the maximum use of agrotechnical and biological methods. 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. In order to protect nature, the widespread use of biological plant protection products is envisaged.
- 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.
Methods of movement of insects: swimming, walking, flying. Examples of insects that use walking to move: spider, ladybug. The structure of insect wings, the mechanism of flight. Adaptation to water, movement on its surface (water strider).
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The class Insects is one of the most numerous. If you carefully examine the insect's body, you can observe a clear division: head, chest, abdomen. A pair of antennae, which are sensory organs, a pair of eyes and a mouthparts are located on the head. Each of the three segments of the thoracic region is endowed with a pair of legs. The dorsal side of the two segments is equipped with one, and sometimes two pairs of wings. The abdomen of any individual representing the class Insects is also divided into segments, which can be from six to twelve.
The hypodermis, which is located immediately under the chitin that covers the body from the outside, is composed of homogeneous cells, some of them are glandular. Chitin, which has the property of not stretching, replaces the old layer with a new one, that is, the process of molting occurs. This process is very important during the growth of the insect.
The Insect class is distinguished by a complex oral apparatus, consisting of upper and lower jaws, upper and lower lips, and a tongue, which is a chitinous protrusion of the floor of the mouth.
The oral apparatus of insects is of several types: in beetles it is gnawing, in flies it is licking, in butterflies it is sucking, and in mosquitoes and fleas it is piercing-sucking.
The respiratory organs are the trachea; they supply the tissues with oxygen. Up to ten pairs of respiratory openings are located on the lateral parts of the insect’s body.
The poor development of the circulatory system is associated with the special structure of the respiratory organs. The nervous system, on the contrary, has a high level of development. There are three sections of the “brain” - anterior, middle and posterior.
Creatures representing the class Insects have well-developed sensitive hairs, present throughout the body, that perform the function of antennae and mandibular palps being organs of smell. As for the hearing organs, certain types of insects, the grasshopper, for example, pick up sounds with a third pair of legs. It is here, on the shins, that this class is located and can be simple or complex. When the teeth of the upper wings rub against the thighs of the hind limbs, a sound characteristic of a particular insect appears.
As a rule, insects bring many problems to humans. They are carriers and causative agents of various diseases. That’s why scientists have been studying this class for a long time. The science that studies entomology. Today it is separated into a separate branch of biology, and this branch is developing at an unusually fast pace.
Entomology can be divided into several independent areas: general entomology, medical, forestry, veterinary, agricultural. A separate story with beekeeping and sericulture - they are very close to entomology.
In general, each direction of this science has its own specifics. For example, general entomology deals with the study of the basic structural features of insects, both internal and external, the study of their lifestyle, development and reproduction, as well as the identification of their relationships with the environment.
Insect pests and insect pollinators are areas of concern in agricultural entomology. Scientists in this area are also developing ways to control pests in order to minimize damage to agriculture.
The class Insects is huge and diverse. Its representatives live everywhere: soil and plants, air and water, as well as mountains and lowlands, deserts and snow - all this is their usual habitat.
A typical representative of the class Insects are Khrushchev May (Melolontha melolontha). The body length reaches from 5 to 60 mm, the wingspan does not exceed four centimeters.
Features of the external structure
Body parts - head, chest and abdomen, each of which performs its own functions. Chairman formed from 6 segments that completely merge. The head has antennae, eyes and mouthparts. The antennae, which are called antennae or siblings, are one pair. In beetles they are lamellar and perform the function of an olfactory organ. The mouth has three pairs of organs: upper jaws (mandibles), lower jaws (maxilla) and upper and lower lips. These organs form gnawing mouthparts. There are projections on the lower jaws and lower lip - palps, which serve as organs of touch and taste. Along with the antennae there are complex (faceted) eyes. In insects they can be simple or complex.
Depending on the type of food, the mouthparts of insects are modified, which leads to the formation of different types of mouthparts:
gnawing mouthparts - oral organs, which include top And lower lips, upper And mandibles(e.g. grannies, beetles, cockroaches, orthoptera, termites, ants)
gnawing-licking oral apparatus- oral organs in which the lower lip and lower jaws form proboscis, A upper jaws lost chewing function and participate in the construction of honeycombs (bees, bumblebees)
sucking mouthparts - mouth organs have been transformed into proboscis, which is adapted to feeding on nectar from flowers (butterflies)
piercing-sucking mouthparts- oral organs in which the lower lip forms proboscis for sucking liquids, and the upper and lower jaws are turned into long, spiny ones stilettos for piercing body coverings (bugs, aphids, lice, some dipterans).
Some adult insects (silkworms, gadflies) do not feed, so their mouthparts do not function and are very reduced.
Thoracic region consists of three segments (prothorax, mesothorax and metathorax), which have organs of movement - legs and in winged insects - wings. On each segment of the chest there is one pair of limbs, and therefore in insects 3 pairs of walking legs, which is why they are also called hexapods (six-legged). In other insects, these limbs can perform other functions and therefore the following types are distinguished: jumping, swimming, grasping, digging, running, and the like. Two pairs of wings are attached to the second and third segments of insects. Wings are folds of integument, the walls of which are built from the upper and lower layers of epithelial cells covered with a cuticle. Between these layers there is a gap with hemolymph. The supporting frame of the wing is formed by a system of longitudinal and transverse thickenings called veins. In beetles, the first pair is modified into hard elytra. Elytra- modified fore wings that protect the membranous wings from damage when the insect is not flying.
Abdomen formed by a different number of segments (no more than twelve) and contains the bulk of internal organs. This section is devoid of limbs, has openings of the tracheal system - spiracles, and ends with the ovipositor.
Veils are represented by the hypodermis and chitinous cuticle with a waxy film that prevents the evaporation of water. On the body of an insect there are numerous hairs that perform the function of organs of touch, create an air layer that protects the body from water during rain, from overheating, determine coloring, and the like. Ducts of odorous glands open onto the surface of the body, which help individuals find each other during reproduction. In other insects there may be poisonous (in hairy caterpillars), wax (in bees), silk (in butterfly larvae) and other glands.
Peculiarities internal structure and life processes
Digestive system consists of the anterior (oral cavity with salivary glands, pharynx, esophagus, stomach), middle (midgut with pyloric appendages, without liver) and posterior (hindgut with anus) sections. Khrushchev eats plant foods, so the outgrowths of its intestines contain symbiotic microorganisms that secrete enzymes for digesting fiber. In larvae, the intestine is relatively long and food is retained in the body for a long time. Absorption of water in order to prevent its loss occurs in the hindgut with the help of the rectal glands.
Respiratory system - tracheal type. A system of tracheal tubes branches throughout the body, which open on the abdomen with dichals - stigmas (on one segment - a pair). Air moves in this system due to diffusion and abdominal movements.
Circulatory system open The heart is tubular, located in the dorsal part of the abdomen.
System fluid - hemolymph- colorless and does not participate in the transportation of gases, which is associated with the development of the trachea. It performs functions such as transport of nutrients
Internal structure of the May beetle: A - antennae; B - subpharyngeal nerve ring: B - December ganglia; G - trachea; D - heart; E - ovary; F - Malpighian vessels; WITH - spiracle; AND - goiter; AND - stomach
substances, transfer of metabolic products, distribution of hormones, protection with the help of phagocyte cells from microorganisms, etc. Hemolymph circulation is carried out by contractions of the heart. When the walls of the heart are stretched with the help of muscles, hemolymph enters the heart through the lateral openings (ostia), and when contracted, the valves close the ostia and fluid enters the arteries.
Excretory system represented by Malpighian vessels and the fat body. Malpighian vessels are excretory tubes at the border of the midgut and hindgut. The number of these outgrowths varies from 2 to 150. The fat body is loose connective tissue, which, among other functions, absorbs metabolic products.
Nervous system - nodal chain type, which is characterized by a well-developed “brain” - a suprapharyngeal accumulation of neurons. It is divided into C sections - anterior, middle and posterior. The anterior section is more complex and provides complex forms of behavior. The ventral chain consists of the pidpharyngeal ganglion and, as a rule, 10 thoracic and abdominal enlarged ganglia.
Behavior very complex and is determined by the interaction of unconditioned and conditioned reflexes. Big role For insects, they have such innate forms of behavior as instincts.
Endocrine system carries out humoral regulation with the help of hormones that are secreted by the suprapharyngeal and subpharyngeal nodes, brain appendages, etc. Special meaning for insects have such biologically active substances as ecdysone, that affect shedding, " juvenile hormone"- inhibits maturation pheromones influence members of their own species sex attractants- attract individuals of the opposite sex during reproduction, etc.
Sense organs - the most diverse, which is associated with the general high level of organization and complex behavior of insects. Basically, these are hair or other creations with a receptor inside: organs of vision - eyes, complex faceted and simple, organs of smell - antennae, organs of taste - on the mouth and other parts of the body, organs of touch - sensitive hairs on the integument of the body, hearing organs ( tympanic organs, chordotonal organs) are located on the abdomen (in grasshoppers - on the legs). In May beetles, as in other flying insects, there are special antennae at the base. Johnston bodies to control the speed and direction of flight.
Reproduction. May beetles, like almost all insects, are dioecious. Fertilization is internal. The sexual dimorphism of the May beetle is expressed in the fact that the antennae of males have seven segments, while females have only six; females have an ovipositor for laying eggs, extended shin legs for burying them in the soil, etc.
Development at chafer- indirect, in which a pupa is observed in the life cycle. doll - a stage of insect development with complete metamorphosis, in which internal restructuring occurs, as a result of which the insect turns from a larva into an adult. The transformation from egg to adult insect stage is regulated by hormones and continues in the beetle for several years.
Development in most insects is usually indirect, but there is direct:
1) straight (in primary insects without wings, or bristletail)
2) indirect (or development with transformation - metamorphosis):
■ with complete transformation: egg - larva - doll - imago (in Coleoptera, Hymenoptera, Lepidoptera, Diptera, fleas)
■ with incomplete transformation: egg - larva - imago (in Orthoptera, cockroaches, bedbugs).
The biological significance of the transformation is that: a) larvae and adults live in different conditions and therefore do not compete for habitat and food; b) insects have a greater opportunity to survive under unfavorable living conditions ( low temperature, lack of food) at one or another less vulnerable stage of development, in general promotes an increase in the number of individuals of the species.
