But a diagram of the organ system of insects. How many body parts do insects have: external structure

12.01.2022 -

The first scientific descriptions of the external structure of insects, presented in entomological works, date back to the 16th century. The characterization of the histological structure by entomologists was given only three centuries later. Almost every representative of the Insect class has its own characteristic structural features that make it possible to classify different species according to the type of limbs, antennae, wings and mouthparts.

The general structure of the body of insects (with a diagram and pictures)

The body of insects consists of segments - segments, diverse in shape and bearing various external appendages and organs. The structure of the body of insects includes three sections: the head, chest and abdomen. The head includes the main sense organs and the oral apparatus. Insects have a pair of elongated segmented antennae (antennae) on their heads - the organs of touch and smell - and a pair of compound compound eyes - the main visual organs. In addition, many insects have from 1 to 3 small simple eyes - auxiliary photosensitive organs. The oral apparatus of insects is formed on the basis of 3 pairs of jaws - modified limbs of the head segments, the third pair of jaws is fused. The chest consists of 3 large segments: prothorax, mesothorax, metathorax - m carries locomotor organs. Each segment has one pair of segmented legs: anterior, middle, posterior. In most insects, 2 pairs of wings are developed: the anterior, located on the mesothorax, and the hind, located on the metathorax. In a number of insects, one or both pairs of wings may be underdeveloped up to their complete loss. The abdomen, consisting of numerous uniform segments, contains most of the internal organs.

Pay attention to the picture - there are 11 segments in the structure of the abdomen of insects, however, most insects retain from 5 to 10 segments:

In the 8th-9th segments, according to their complete composition, the reproductive apparatus is located. V females of some insects (Orthoptera, Hymenoptera) on the underside of these segments, a special organ for laying eggs, the ovipositor, is developed. Some insects (mayflies, cockroaches, orthoptera, earwigs) have a pair of churches on the last segment of the abdomen - appendages of various shapes and purposes.

Look at the detailed diagram of the structure of insects, where all the main departments are indicated:

Insect head structure

The head is the most compact section of the body of insects. The segments included in the structure of the head of insects merge without distinguishable boundaries. Their integuments form a dense monolithic head capsule. Various parts stand out on the head, often separated by sutures. The lower anterior part of the head is called the clypeus, followed by the front part - the forehead, then the upper part of the head - the crown, divided by a longitudinal suture into two halves. The area behind the crown - the back of the head - is located above the occipital foramen. The sides of the head below and behind the compound eyes are called cheeks and temples, respectively.

The main types of pairs of antennae in insects

Basic tactile and olfactory; insect organs - paired jointed antennae (or antennae) are usually movably attached to the forehead, between the eyes, in special articular pits covered with a membrane. The length and shape of antennae in insects is extremely diverse and often serves as a clear sign for identifying families, genera, and species of insects. The number of segments in the antennae varies in different insects from three to a hundred or more. In the general structure of the antennae of insects, three sections are distinguished: the handle - the first segment, the leg - the second segment, and the flagellum - the totality of the remaining segments. Only the handle and leg are equipped with their own muscles and are actively mobile. Inside the leg there is an accumulation of special sensitive cells - the Johnston organ, which perceives the vibrations of the environment, some insects also have sound vibrations.

Insects have numerous types of antennae. Bristle antennae - thin, tapering towards the top (cockroaches, grasshoppers), and filamentous antennae - thin, uniform along the entire length (ground beetles, locusts), are also called simple because of their typical shape. The bead-like type of insect antennae is distinguished by convex, laterally rounded segments (dark beetle beetles). The segments of the sawtooth antennas have sharp angles, giving a jagged shape (click beetles and barbels). The elongated processes have segments of comb-shaped antennae (some species of click beetles and moths). The type of antennae of insects with a apex thickened due to the expanded last segments is called club-shaped (diurnal butterflies). Antennas with a large, pronounced club - capitate (gravedigger beetles and bark beetles). The antennae of insects with a club consisting of wide lamellar segments are lamellar clubs (beetles and dung beetles). Fusiform antennae widen towards the middle, narrowed and pointed at the apex (hawk moths). The cranked antennae are bent at the articulation of the handle with the rest (wasps, ants). The articulated pairs of antennae of insects ending in a club or comb are called, respectively, geniculate-club (weevil beetles) and geniculate-comb (deer beetles). The segments of the cirrus antennae are equipped with densely arranged thin sensitive hairs (moths, some mosquitoes). Seta-bearing antennae always short, 3-segmented; a sensitive seta (flies) extends from the last segment. Antennae with asymmetrical segments of various shapes are called irregular (blister beetles).

Types of mouthparts of insects

Due to the variety of types of food and methods of obtaining food, insects have developed a variety of mouthparts. Types of mouthparts of insects serve as major systematic features at the order level. Their study should begin with the primary and most common - gnawing apparatus.

Insects such as dragonflies, orthopterans, beetles, lacewings, most hymenoptera, and many smaller orders have gnawing mouthparts. It is designed to feed mainly on dense food: plant, animal or organic residues. The apparatus consists of the upper lip, upper jaws, lower jaws and lower lip. The upper lip is a specialized skin fold of a rectangular or oval shape. Covering other oral appendages in front, the upper lip serves as a tactile and gustatory organ. The upper jaws are monolithic, non-segmented, strongly chitinized. Teeth are developed on the inner edge. With their help, insects capture, gnaw off and begin to chew food. The lower jaws retain articulation and consist of a basal segment attached to the head capsule and a stem extending from it; at the top of the stem are the outer and inner chewing blades, the latter is equipped with teeth. A 4-5-segmented mandibular sensory palp extends somewhat to the side of the stem. The third pair of jaws in insects grows together to form the lower lip. The structure of the lips of the oral apparatus of insects is similar to the lower jaws.

The main part is divided by a transverse seam into a posterior chin and a prechin bifurcated at the top. Each half of the prechin bears a pair of small chewing lobes: internal - tongues and external - adnexal tongues, as well as 3-4-segmented lower labial sensory palps.

The piercing-sucking oral apparatus is designed to feed on a variety of liquid food hidden under the integumentary tissues of animals or plants. This apparatus is developed in bugs, homoptera (aphids, etc.), fringed-winged (thrips), and part of the order Diptera (blood-sucking mosquitoes). The outer part of the mouthparts of the bug is represented by an elongated jointed movable proboscis attached to the front edge of the head and bending under the head at rest. The proboscis is a modified lower lip. Inside the hollow proboscis lie modified upper and lower jaws - two pairs of thin, hard and pointed piercing needles or bristles. The upper jaws are simple needles that pierce the integument. A pair of lower jaws is tightly connected to each other and has two longitudinal grooves on the inner surface, forming two channels. Upper - food - serves for absorption of food. Through the lower - salivary - channel, saliva containing enzymes necessary for the primary processing of food is carried into the nutrient substrate. A small upper lip lies at the base of the proboscis. When feeding, the insect presses its proboscis on the substrate. The proboscis is slightly bent, and a bundle of piercing needles pierces the integument and penetrates the tissues. Next comes the injection of saliva and the absorption of food. Gnawing and piercing-sucking mouthparts insects can damage plants.

The sucking mouth apparatus is developed in Lepidoptera (butterflies), adapted for extracting nectar from the corollas of flowers. The upper and lower lips in the external structure of the sucking apparatus in representatives of the class Insects are small, in the form of simple plates, on the lower lip there are well-developed palps. The upper jaws are missing. The main part - a long, flexible, spirally twisted proboscis at rest - is formed by modified lower jaws. Connecting with each other, the lower jaws form a tube with an extensive internal cavity that serves to suck up nectar. The walls of the proboscis contain many chitinous rings that provide its elasticity and keep the alimentary canal open.

Gnawing-licking mouthparts are found in some Hymenoptera (bees, bumblebees). It is also designed to feed on nectar, but has a completely different structure. The upper lip and upper jaws retain their typical form for the gnawing apparatus. The main working part consists of strongly elongated, modified and interconnected lower jaws and lower lip. In the lower jaws, the outer lobes are especially developed, and in the lower lip - the inner lobes, fused into a long, flexible, tubular tongue. When folded, these parts form a proboscis, which is a system of three channels of decreasing diameter inserted into each other. Through the largest external canal, formed by the lower jaws and elongated palps of the lower lip, plentiful and close food or water is sucked in. The second channel - the cavity of the tongue - serves to suck nectar from deep corollas. The third, capillary canal, passing in the upper wall of the tongue, is salivary.

Licking mouthparts have a significant proportion of Diptera—most flies. This is the most complex in structure of the oral apparatus of representatives of the class Insects. It serves to feed various liquid foods and fine food suspensions (sugar juices, decomposition products of organic residues, etc.). It is a fleshy mobile proboscis, developed mainly due to the lower lip. The proboscis ends in a pair of semicircular lobes, forming a mouth disk, in the center of which is a mouth opening surrounded by a row of chitinous denticles. On the surface of the blades, a system of tubules is developed, opening with tiny pores. This is the filtering part of the apparatus, absorbing only small dense particles along with the liquid. The teeth of the oral disc can scrape food particles from the substrate.

Types of insect legs: structure and main types of limbs (with photo)

The leg of an insect consists of 5 sections. The first from the base is called the coxa - a short and wide segment, movably attached to the lower part of the segment. The second section, a small segment-trochanter, which increases the mobility of the leg. The third section - the thigh, elongated and thickened, contains the most powerful motor muscles. The fourth section is the lower leg, connected to the thigh by the knee joint. It is also elongated, but narrower than the hips. The last section in the structure of the legs of insects is the jointed lanka. It usually consists of 3 to 5, rarely 1-2 segments. The foot ends in a pair of chitinous claws.

As a result of adaptation to different ways of movement and performance of other functions, insects develop various types of limbs. The two most common types of insect legs - walking and running - have a common structure. The running leg is distinguished by a longer thigh and lower leg, an elongated, narrow tarsus. Parts of the walking leg are somewhat shorter and wider, at the end of the foot there is an extension - the sole. Running legs are characteristic of fast, agile insects (ground beetles, ants). Most insects have walking legs. Other specialized and modified types of legs are represented in insects, as a rule, in one pair, more often the anterior or posterior. Jumping legs are usually hind legs. A distinctive feature of the structure of these limbs of insects is a powerful, noticeably thickened thigh, containing the main muscles that act when jumping. This type is common in the orders Orthoptera (grasshoppers, crickets, locusts), Homoptera (leafhoppers and leafhoppers), fleas and some beetles (ground fleas). Swimming legs, also hind legs, are found in many aquatic insects - swimming beetles and whirlwinds, rowing bugs and smoothies. This type of insect legs is characterized by a flattened, paddle-like shape; along the edge of the tarsus, elastic bristles are developed that increase the rowing surface. Digging legs - the forelimbs of some underground or burrowing insects (bears, dung beetles). These are powerful, thick, somewhat shortened legs, the lower leg is spatulately expanded and flattened, with large teeth. Grasping forelegs are found in some predatory insects, most developed in praying mantises. These legs are elongated and mobile. The thigh and lower leg are covered with sharp spikes. At rest, the grasping legs are folded; when prey appears, they are thrown forward sharply, pinching the prey between the thigh and lower leg. Collective called the hind legs of bees and bumblebees, which serve to collect pollen. The collecting device is located on the lower leg and a large flattened first segment of the tarsus. It consists of a basket - a recess on the lower leg bordered with hairs - and a brush - a system of numerous small bristles on the foot. When cleaning the body, the insect sequentially transfers pollen to the brushes and then to the baskets of the hind legs, where pollen clumps are formed - pollen.

These photos show different types of insect legs:

The main types of insect wings: photo and structure

The insect wing is formed by a modified fold of the skin - the thinnest two-layer wing membrane, in which chitinized veins and modified tracheal vessels pass.

As you can see in the photo, three sides are distinguished in the insect wing - the front edge, the outer (outer) edge and the rear (inner) edge:

Also, the structure of the insect wing includes three angles: the base, the apex and the back angle. According to the direction in the wing, the veins are divided into longitudinal and transverse. The venation is based on large, often branched longitudinal veins reaching the wing margins. Small, unbranched transverse veins are located between adjacent longitudinal ones. The veins subdivide the wing membrane into a series of cells, which are closed, completely limited by veins, and open, reaching the edge of the wing.

The structure of the wings is considered in two main aspects: venation (number and arrangement of veins) and consistency (thickness and density of the wing plate). There are two main types of venation in insect wings. Reticulate is a dense, fine-meshed venation, in which, in addition to longitudinal veins, there are many small transverse ones, forming numerous (more than 20) closed cells. Such venation is developed in dragonflies, orthoptera, lacewings, and some other orders. The membranous venation is sparse, with few or no transverse veins; cells large, few. This venation is developed in most orders of insects (Lepidoptera, Hymenoptera, Diptera, Coleoptera, etc.). The venation of the fore and hind wings of insects is always the same.

Four types of insect wings are distinguished by density. The most common are membranous wings, formed by the thinnest, transparent wing membrane. Only in butterflies, membranous wings are opaque, because they are covered with a layer of tiny scales. The hind wings of all insects are membranous, and in many (dragonflies, lepidoptera, lacewing, hymenoptera, etc.), both pairs are membranous. In a number of insects, the front wings are compacted and serve as a protective cover. Leathery called the front wings of orthoptera, cockroaches, praying mantises, earwigs. These wings are somewhat thickened but not hard, opaque or translucent, always colored, usually retaining venation. The front wings of bedbugs are called semi-rigid, subdivided transversely into a compacted base and a membranous apex with developed veins. Such wings are active in flight and serve as a protective cover. Rigid wings, or elytra, are the front wings of beetles. They are strongly thickened and chitinized, often hard, colored, venation is completely lost. These wings, while providing reliable body protection, do not actively work in flight. Some forms of wings are distinguished by the nature of the pubescence, for example, fringed in thrips and scaly in butterflies.

The class Insects is the most numerous and most diverse class of living beings on Earth. It is believed that at least 10 20 insects live on our planet at the same time. The number of insect species already exceeds 1 million species, and every year entomologists describe about 10,000 more new species.

External building. In all insects, the body is divided into three sections: head, breast and abdomen. On the chest is three couples running legs, the abdomen is devoid of limbs. Most have wings and capable of active flight.

On the head of insects one pair antennae(ties, antennas). These are the organs of smell. There are also insects on the head pair difficult(faceted) eye, and in some species, besides them, there is also simple eyes.

The insect's mouth is surrounded three in pairs oral limbs(mouth organs), which form the oral apparatus, or, in other words, jaws. The upper jaw is formed by one pair of limbs, in insects it is called mandibles, or mandibles. The second pair of mouthparts forms the mandibles, or first maxillas, and the third pair grows together and forms lower lip, or second maxillas. On the lower jaw and lower lip there may be

couple palps. In addition, the composition of the oral limbs also includes upper lip- This is a mobile outgrowth of the first segment of the head. Thus, the mouthparts of an insect consist of an upper lip, a pair of upper jaws, a pair of lower jaws, and a lower lip. This is the so-called oral apparatus gnawing type.

Depending on the method of feeding, mouthparts can be of the following different types:

oral apparatus gnawing type - characteristic of insects that feed on hard plant foods (beetles, orthoptera, cockroaches, butterfly caterpillars). This is the most ancient, original type of oral apparatus;

oral apparatus sucking type - butterfly mouthparts;

oral apparatus licking - flies.

oral apparatus piercing-sucking type - mouthparts of bedbugs, mosquitoes, worms, aphids;

oral apparatus varnishing type - such mouthparts in bees and bumblebees.

The chest of an insect consists of three segments: anterior, medium- and metasternum. Each thoracic segment contains a pair running legs. On the middle and metathorax in flying species there are most often two pairs wings.
Walking legs are made up of five segments, which are called basin, swivel, hip, shin and paw with claws. Leg segments articulate with joints and form a system of levers. Due to different lifestyles, walking legs are running(cockroaches, ground beetles, bugs), jumping(hind leg of a grasshopper or flea), swimming(hind leg of the swimming beetle and water beetle), digging(front leg of the bear), grasping(mantis front leg), collective(hind leg of the bee) and others.

The abdomen in the most evolutionarily advanced is characterized by a decrease in the number of segments (from 11 to 4-5 in Hymenoptera and Diptera). On the abdomen, insects have no limbs, or they are modified in sting(bees, wasps) ovipositor(grasshoppers, locusts) or churches(cockroaches).

Body covers. The body is covered with chitinous cuticle. The cuticle is not continuous, but has hard plates called sclerites, and soft articular membranes. The sclerites are connected to each other by means of soft articular membranes, so the cuticle of insects is mobile. Dorsal sclerites

Type Arthropods class Insects

sides of the body are called tergites, sclerites of the ventral side - sternites, and the sclerites of the lateral side of the body are pleurites. The cuticle protects the body from external influences. tissue under the cuticle hypodermis, which produces the cuticle. The most superficial layer of the cuticle is called epicuticle and it is formed by fat-like substances, therefore the covers of insects are not permeable to either water or gases. This allowed insects, as well as arachnids, to inhabit the most arid regions of the globe. The cuticle simultaneously performs the function outdoor skeleton: Serves as a site for muscle attachment. Periodically insects molt, i.e. shed the cuticle.

musculature insects consists of striated fibers that form powerful muscle bundles, i.e. the muscles in insects are represented by separate bundles, and not by a bag like in worms. Insect muscles are capable of very high contraction rates (up to 1000 times per second!), which is why insects can run and fly so fast.

body cavity. The body cavity of insects is mixed - mixocell.

Digestive system typical, consists of front, middle and rear intestines. The foregut is represented mouth, throat, short esophagus and stomach. The mouth is surrounded by three pairs jaws. ducts open into the oral cavity salivary glands. The salivary glands can change and produce a silky thread, turning into spinning glands (in the caterpillars of many species of butterflies). In blood-sucking species, the salivary glands produce a substance that prevents blood clotting. Some species of insects have an expansion of the esophagus - goiter, serving for a more complete digestion of food. In species that eat solid food, there are peculiar chitinous folds in the stomach - teeth facilitating food digestion. AT middle gut food is absorbed. The midgut may have blind outgrowths increasing the suction surface. rear intestine ends anal hole. On the border between the middle and posterior intestines, numerous blindly closed malpighian vessels. These are excretory organs.

In many insects, symbiotic protozoa and bacteria that can break down fiber settle in the intestines. The food spectrum of insects is extremely diverse. Insects include omnivores, herbivores, and carnivores. There are species that feed on carrion, manure, plant debris, blood, tissues of living organisms. Some species have adapted to assimilate such low-nutrient substances as wax, hair, feathers, and horns of ungulates.

Respiratory system – tracheal system. It starts with holes - spiracles, or stigmas, which are located on the sides of the middle and metathorax and on each segment of the abdomen. Often stigmas have special closing valves, and air selectively enters the well-developed tracheal system. Trachea these are air tubes, which are deep invaginations of the cuticle. The tracheae penetrate the entire body of the insect, branching into ever thinner tubes - tracheoles. Tracheas have chitinous rings and spirals that prevent the walls from collapsing. The tracheal system transports gases. smallest

Type Arthropods class Insects

tracheoles fit to every cell of the insect body, so insects do not suffer from shortness of breath, i.e. do not suffocate even during the fastest flight. But the role of hemolymph (the so-called blood in arthropods) in the transport of gases is small.

Insects can perform respiratory movements with the help of active expansion and contraction of the abdomen.

Many larvae living in water (dragonfly and mayfly larvae) develop so-called tracheal gills - external protrusions of the tracheal system.

Circulatory system relatively poorly developed in insects. A heart is in pericardial sinus, on the dorsal side of the abdomen. The heart is a tube blindly closed at the posterior end, divided into chambers and having paired openings with valves on the sides - ostia. Muscles are attached to each chamber of the heart, providing contraction of the chambers. Hemolymph from the heart moves along the aorta to the front of the body and pours into the body cavity. In the body cavity, the hemolymph washes all the internal organs. Then, through numerous holes, the hemolymph enters the pericardial sinus, then through the ostium, with the expansion of the cardiac chamber, it is sucked into the heart. The hemolymph does not have respiratory pigments and is a yellowish liquid containing phagocytes. Its main function is the transport of nutrients to all organs and metabolic products to the excretory organs. The speed of the hemolymph flow is not great. For example, in a Cockroach, hemolymph circulates in the circulatory system in 25 minutes. The respiratory function of the hemolymph is insignificant, but in some aquatic insect larvae (in bloodworms, mosquito larvae), the hemolymph has hemoglobin, is colored bright red and is responsible for the transport of gases.

excretory organs. These insects include malpighian vessels and fatty body. Malpighievs vessels- these are blind protrusions on the border between the middle and posterior intestines. Malpighian vessels (there are up to 200 or more of them) absorb metabolic products from the hemolymph. Protein metabolism products turn into crystals uric acids, and the liquid is actively reabsorbed (absorbed) by the vascular epithelium and returned to the body. Uric acid crystals enter the hindgut and are excreted along with the excrement to the outside.

fat body Insects, in addition to the main function - the accumulation of reserve nutrients, also serves as an "accumulation kidney", it has special excretory cells that are gradually saturated with hardly soluble uric acid. The fat body surrounds all internal organs. The yellowish or whitish mass that protrudes from the crushed insect is nothing but a fatty body.

Nervous system. Insects have a nervous system ladder type. The supraesophageal ganglions (and their pair) merged and formed the so-called " head brain". Each thoracic and abdominal segment contains a pair of ganglia. abdominal nervous chains.

The sense organs of insects are diverse, complex and very well developed. insects have compound compound eyes and simple eyes. Compound eyes are made up of individual functional units ommatidian(facets), the number of which varies in different insect species. In active dragonflies, which

Type Arthropods class Insects

considered the most voracious predators among insects, each eye consists of 28 thousand ommatidia; and in ants, especially in individuals living underground, the number of ommatidia decreases to 8-9 thousand. Some insects have color vision, and color perception is shifted towards short-wave rays: they see the ultraviolet part of the spectrum and do not see red colors. Vision mosaic. There can be three or five simple eyes. The role of simple eyes is not fully understood, but it has been proven that they perceive polarized light, with which insects navigate in cloudy weather.

Many insects are able to make sounds and hear them. hearing organs can be located on the shins of the forelegs, at the base of the wings, on the anterior segments of the abdomen. The organs that make sounds in insects are also diverse.

Olfactory organs located mainly on the antennae, which are most developed in males. organs of taste located not only in the oral cavity, but also on other organs, for example, on the legs - in butterflies, bees, flies, and even on the antennae - in bees, ants.

Scattered over the entire surface of the body of the insect sensory cells that are associated with sensitive hair. With a change in humidity, pressure, a breath of wind, with mechanical action, the position of the hair changes, the receptor cell is excited and transmits a signal to the “brain”.

Many insects perceive magnetic fields and their changes, but entomologists still do not know where the organs that perceive these fields are located.

Insects have balance organs.

reproductive organs. Insects separate sexes. Reproduction is only sexual. Many insects show sexual dimorphism- males can be smaller (in many butterflies) or have a completely different color (gypsy moth butterflies), sometimes males have larger feathery antennae, in some species some separate organs develop strongly (for example, the upper jaws of a male stag beetle look like horns). In males, the abdomen contains a pair of testes from which depart seed tubes merging into an unpaired ejaculatory channel ending cumulative body at the posterior end of the body. The females have two ovary, they open in steam rooms oviducts, which are combined into an unpaired vagina opening at the posterior end of the abdomen sexual hole.

Fertilization internal. During mating, the male's copulatory organ is inserted into the female's genital opening and the sperm enters seminal receptacle, from where - into the vagina, where the fertilization of eggs occurs. In some species, the spermatozoa in the seed receptacle remain alive for several years. In a queen bee, for example, a mating flight occurs once in a lifetime, but she lives and lays eggs all her life (4-5 years).

Insects are known to have parthenogenetic, those. without fertilization, reproduction (this is a variant of sexual reproduction). Female aphids throughout the summer from unfertilized eggs hatch larvae, from which only females develop, only in autumn both males and females appear from larvae, mating occurs, and fertilized eggs hibernate. From parthenogenetic

Type Arthropods class Insects

eggs in social hymenoptera (bees, wasps, ants) form haploid (i.e. with a single set of chromosomes) males.

Development insects is divided into two periods - embryonic, which includes the development of the embryo in the egg, and postembryonic, which begins from the moment the young animal leaves the egg. Postembryonic development in lower primitive insects proceeds without metamorphosis. Most develop with metamorphosis(i.e. with transformation). According to the nature of metamorphosis, insects are divided into insects with incomplete metamorphosis and insects with complete metamorphosis.

to insects with complete transformation include insects in which the larva differs sharply from imago(adult sexually mature insects are called adults), there is a stage pupae, during which the restructuring of the body of the larva occurs and the organs of an adult insect are formed. A fully formed adult insect emerges from the pupa. Insects with complete transformation in adulthood do not molt. Insects with complete metamorphosis include the following orders: Coleoptera, Hymenoptera, Diptera, Lepidoptera, Fleas and others.

In insects with incomplete transformation no pupal stage, hatches from egg larva(nymph), similar to an adult insect, but its wings and gonads are underdeveloped. The larvae eat a lot, grow intensively, molt several times, and after the last molt, winged adult insects with developed gonads (sex glands) already appear. Insects with incomplete transformation include, for example, the orders: Cockroaches, Praying Mantises, Orthoptera, Lice, Homoptera and others.

The role of insects in nature huge. They are an element of biological diversity. In the structure of ecosystems, they act as consumers of the first order (these are herbivorous insects) and consumers of the second order (predatory insects), decomposers (scavengers, dung beetles). They are the object of food for other insectivorous animals - birds, toads, snakes, predatory insects, lizards, spiders, etc. (In other words, insects are carriers of matter and energy along food chains). Insects are useful for man: they pollinate his agricultural plants, they extract honey for him, they give him aesthetic pleasure, they act as his pets, they are the object of scientific research. But insects attack man and his farm animals for blood-sucking, they spoil his supplies and products, they harm cultivated plants, they carry dangerous diseases, and, finally, they are simply annoying and annoying.

External building. In all insects, the body is divided into three sections: head, breast and abdomen. On the chest is three pairs of walking legs, the abdomen is devoid of limbs. Most have wings and capable of active flight.

On the head of insects one pair of antennae(ties, antennas). These are the organs of smell. There are also insects on the head a couple of difficult(faceted) eye, and in some species, besides them, there is also simple eyes.

The insect's mouth is surrounded three pairs of mouthparts(mouth organs), which form the oral apparatus, or, in other words, jaws. The upper jaw is formed by one pair of limbs, in insects it is called mandibles, or mandibles. The second pair of mouthparts forms the mandibles, or first maxillas, and the third pair grows together and forms lower lip, or second maxillas. On the lower jaw and lower lip there may be

a pair of palps. In addition, the composition of the oral limbs also includes upper lip- This is a mobile outgrowth of the first segment of the head. Thus, the mouthparts of an insect consist of an upper lip, a pair of upper jaws, a pair of lower jaws, and a lower lip. This is the so-called oral apparatus gnawing type.

Depending on the method of feeding, mouthparts can be of the following different types:

・Mouth apparatus gnawing type - characteristic of insects that feed on hard plant foods (beetles, orthoptera, cockroaches, butterfly caterpillars). This is the most ancient, original type of oral apparatus;

・Mouth apparatus sucking type - butterfly mouthparts;

・Mouth apparatus licking - flies.

・Mouth apparatus piercing-sucking type - mouthparts of bedbugs, mosquitoes, worms, aphids;

・Mouth apparatus varnishing type - such mouthparts in bees and bumblebees.

The chest of an insect consists of three segments: anterior, medium- and metasternum. Each thoracic segment contains a pair walking legs. On the middle and metathorax in flying species there are most often two pairs wings.

Walking legs are made up of five segments, which are called basin, swivel, hip, shin and paw with claws. Leg segments articulate with joints and form a system of levers. Due to different lifestyles, walking legs are running(cockroaches, ground beetles, bugs), jumping(hind leg of a grasshopper or flea), swimming(hind leg of the swimming beetle and water beetle), digging(front leg of the bear), grasping(mantis front leg), collective(hind leg of the bee) and others.

Body covers. The body is covered with chitinous cuticle. The cuticle is not continuous, but has hard plates called sclerites, and soft articular membranes. The sclerites are connected to each other by means of soft articular membranes, so the cuticle of insects is mobile. Dorsal sclerites

Type Arthropods class Insects

sides of the body are called tergites, sclerites of the ventral side - sternites, and the sclerites of the lateral side of the body are pleurites. The cuticle protects the body from external influences. tissue under the cuticle hypodermis, which produces the cuticle. The most superficial layer of the cuticle is called epicuticle and it is formed by fat-like substances, therefore the covers of insects are not permeable to either water or gases. This allowed insects, as well as arachnids, to inhabit the most arid regions of the globe. The cuticle simultaneously performs the function exoskeleton: Serves as a site for muscle attachment. Periodically insects molt, i.e. shed the cuticle.

body cavity. The body cavity of insects is mixed - mixocell.

Digestive system typical, consists of front, middle and rear intestines. The foregut is represented mouth, throat, short esophagus and stomach. The mouth is surrounded by three pairs jaws. ducts open into the oral cavity salivary glands. The salivary glands can change and produce a silky thread, turning into spinning glands (in the caterpillars of many species of butterflies). In blood-sucking species, the salivary glands produce a substance that prevents blood clotting. Some species of insects have an expansion of the esophagus - goiter, serving for a more complete digestion of food. In species that eat solid food, there are peculiar chitinous folds in the stomach - teeth facilitating food digestion. AT midgut food is absorbed. The midgut may have blind outgrowths increasing the suction surface. hindgut ends anus. On the border between the middle and posterior intestines, numerous blindly closed malpighian vessels. These are excretory organs.

Respiratory system – tracheal system. It starts with holes - spiracles, or stigmas, which are located on the sides of the middle and metathorax and on each segment of the abdomen. Often stigmas have special closing valves, and air selectively enters the well-developed tracheal system. Trachea these are air tubes, which are deep invaginations of the cuticle. The tracheae penetrate the entire body of the insect, branching into ever thinner tubes - tracheoles. Tracheas have chitinous rings and spirals that prevent the walls from collapsing. The tracheal system transports gases. smallest

Type Arthropods class Insects

Insects can perform respiratory movements with the help of active expansion and contraction of the abdomen.

Many larvae living in water (dragonfly and mayfly larvae) develop so-called tracheal gills - external protrusions of the tracheal system.

Circulatory system relatively poorly developed in insects. A heart is in paracardiac sinus, on the dorsal side of the abdomen. The heart is a tube blindly closed at the posterior end, divided into chambers and having paired openings with valves on the sides - ostia. Muscles are attached to each chamber of the heart, providing contraction of the chambers. Hemolymph from the heart moves along the aorta to the front of the body and pours into the body cavity. In the body cavity, the hemolymph washes all the internal organs. Then, through numerous holes, the hemolymph enters the pericardial sinus, then through the ostium, with the expansion of the cardiac chamber, it is sucked into the heart. The hemolymph does not have respiratory pigments and is a yellowish liquid containing phagocytes. Its main function is the transport of nutrients to all organs and metabolic products to the excretory organs. The speed of the hemolymph flow is not great. For example, in a Cockroach, hemolymph circulates in the circulatory system in 25 minutes. The respiratory function of the hemolymph is insignificant, but in some aquatic insect larvae (in bloodworms, mosquito larvae), the hemolymph has hemoglobin, is colored bright red and is responsible for the transport of gases.

excretory organs. These insects include malpighian vessels and fat body. Malpighian vessels- these are blind protrusions on the border between the middle and posterior intestines. Malpighian vessels (there are up to 200 or more of them) absorb metabolic products from the hemolymph. Protein metabolism products turn into crystals uric acid, and the liquid is actively reabsorbed (absorbed) by the vascular epithelium and returned to the body. Uric acid crystals enter the hindgut and are excreted along with the excrement to the outside.

Nervous system. Insects have a nervous system ladder type. The supraesophageal ganglions (and their pair) merged and formed the so-called " brain". Each thoracic and abdominal segment contains a pair of ganglia. ventral nerve cord.

The sense organs of insects are diverse, complex and very well developed. insects have compound compound eyes and simple eyes. Compound eyes are made up of individual functional units ommatidian(facets), the number of which varies in different insect species. In active dragonflies, which

Type Arthropods class Insects

Many insects perceive magnetic fields and their changes, but entomologists still do not know where the organs that perceive these fields are located.

Insects have balance organs.

Reproductive organs. Insects separate sexes. Reproduction is only sexual. Many insects show sexual dimorphism- males can be smaller (in many butterflies) or have a completely different color (gypsy moth butterflies), sometimes males have larger feathery antennae, in some species some separate organs develop strongly (for example, the upper jaws of a male stag beetle look like horns). In males, the abdomen contains a pair of testes from which depart seed tubes merging into an unpaired ejaculatory canal ending aggregative body at the posterior end of the body. The females have two ovaries, they open in steam rooms oviducts, which are combined into an unpaired vagina opening at the posterior end of the abdomen genital opening.

Type Arthropods class Insects

eggs in social hymenoptera (bees, wasps, ants) form haploid (i.e. with a single set of chromosomes) males.

The skin of insects has a complex, multilayered structure. First of all, they are divided into outer layer - cuticle and the inner layer skin cells - hypodermis. The substance that determines the basic properties of the cuticle is the nitrogenous polysaccharide chitin, which has high mechanical and chemical resistance.

Digestive system of insects

The digestive system is divided into three general sections: the anterior, middle, and hindgut.

The foregut includes the oral cavity, into which the salivary glands open, a pharynx with highly developed muscles, an elongated esophagus, a goiter - a reservoir for the accumulation of food, well developed in sucking insects, and a compact muscular stomach that grinds food, better developed in gnawing insects.

The main digestion occurs in the midgut under the action of secreted enzymes. The walls of the midgut absorb nutrients. In many insects, the midgut forms blindly closed processes that increase the digestive surface. In the thicker hindgut, excess water is absorbed with dissolved low molecular weight substances, excrement is formed, which is removed through the rectum and anus.

excretory system of insects

The main excretory organs of insects- Malpighian vessels, tubular tubules (from two to a hundred), the closed ends of which are freely located in the abdominal cavity, with the other ends they open into the intestine at the border of the middle and posterior intestines. Liquid metabolic products - excess salts, nitrogenous compounds - are selectively absorbed by the thin walls of blood vessels, concentrated and excreted through the hindgut.

Respiratory system of insects

It is represented by a complex of tracheas - air tubes with elastic walls containing chitin. Air enters the trachea through spiracles - small paired openings located on the sides of the segments, in many insects, from the mesothorax to the end of the abdomen. In the spiracles there are locking devices that regulate air exchange. Further, the tracheae branch many times up to the thinnest tracheoles, penetrating the entire body and delivering air directly to organs and tissues.

Insect circulatory system

The circulatory system of insects is not closed; part of its path, the blood passes not through special vessels, but in the body cavity. The central organ is the heart, or dorsal vessel, lying in the upper part of the abdominal cavity and subdivided into a number (6-7) of homogeneous pulsating chambers. The heart passes into the aorta, which, heading forward, opens into the cavity of the head. Further, the blood spreads into the body cavity due to the work of the heart and the contraction of the diaphragms, entering the vessels of the limbs, antennae and wings. Blood is sucked into the chambers of the heart through openings in the side walls. The blood of insects is called hemolymph.. It is usually unstained and does not contain hemoglobin or similar oxygen scavengers delivered directly by the tracheal system. The hemolymph performs the transport of nutrients and excretions, as well as the function of immunity.

Nervous system of insects

The central nervous system is represented by the supraesophageal nerve ganglion, or the brain, consisting of three pairs of merged nerve nodes. A near-pharyngeal nerve ring departs from it, connected below with a pair of subpharyngeal ganglia. From them in the lower part of the body cavity stretches the abdominal nerve chain. Initially paired nodes in each segment in some insects merge in the thoracic region. The peripheral nervous system is connected with the central nervous system - a set of nerves extending from the nodes to the muscles, and the sympathetic system that goes from the subpharyngeal nodes to the internal organs.

Sense organs of insects

Despite their small size, insects have complex, highly sensitive sense organs. The organs of vision are represented by complex compound eyes and simple eyes. The compound eye consists of thousands of elementary visual units - ommatidia. Insects have developed color vision, the spectrum of which is somewhat shifted to the ultraviolet region. Simple eyes, apparently, serve as additional photosensitive organs and are able to perceive polarized light. Insects show a highly developed visual orientation, some of them are guided by the sun, taking into account its declination.

The main organs of smell are antennas that carry many special sensitive receptors. The sharpness and specificity of the sense of smell of insects is unusually great. The males of some moths find the female, guided by the smell of the sex pheromone, from a distance of 10-12 km.

Only some insects have specially developed hearing organs. Taste receptors are concentrated mainly on the oral appendages - sensitive palps, and in some insects (butterflies and bees) are found even on the paws. Insects have a highly specific taste, which makes it possible to accurately identify food objects.

In the skin of insects, in addition to numerous tactile receptors, some receptors register pressure, temperature, microvibrations of the environment, and other parameters.

reproductive system of insects

The reproductive system of insects is represented by the genital and adnexal glands, excretory ducts and external genital organs. The female reproductive system consists of paired glands - ovaries, consisting of egg tubes. They produce numerous eggs. The excretory ducts are paired oviducts coming from the ovaries, uniting into an unpaired oviduct, which opens with a genital opening. A chamber for storing sperm is connected to the oviduct - a seminal receptacle. In the male reproductive system, paired glands are developed - the testes, consisting of small lobules that produce spermatozoa. Paired spermatic ducts depart from them, uniting in the ejaculatory canal, passing through the copulatory organ of the male. Fertilization in insects is internal.

1. External building.

2. Internal structure.

About 1 million species are known. The habitats are varied.

1. External building

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

(thorax) and abdomen (abdomen).

Head

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

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

1. External structure

worms (toothed moths) of the mandible, the lower lip in the form of a small platform with palps, the proboscis is formed by elongated outer chewing lobes of maxilla. The piercing-sucking mouthparts (mosquitoes, bedbugs) include the entire set of mouthparts, but they have lost their original shape, most of them have turned into stylets that serve to pierce the integument of animals and plants. The lower lip in this device performs the function of a case. The licking (filtering) mouth apparatus is characteristic of flies; the labellums of the lower lip are well developed in it; mandibles and maxillae are absent.

Thoracic

It is formed by 3 segments, locomotor organs are associated with it: legs and wings. The limb of an insect consists of a coxa, trochanter, tibia, tarsus, and pretarsus. There are several types of limbs. Wings are placed on the second (mesothorax) and third (mesothorax) segments. Wings more often 2 pairs, less often (dipterous, fanopterous) 1 pair. The second in this case is small in size, turned into a haltere. Wings - lateral folds of integument, originated from paranotums. They are two-layer, nerves, trachea, hemolymph pass through them. The following types of wings are distinguished: mesh, membranous, rigid (elytra), semi-rigid (hemielytra). The wings have a system of longitudinal and transverse veins. The longitudinal veins of the wing are: costal (C), subcostal (Sc), radial (R), medial (M), cubital (Cu) and anal (A) veins. In flight, insects use either one or both pairs of wings. Depending on which pair of wings is used in flight, insects are divided into bimotor, front-motor and rear-motor. Many insects, being diptera, fly on one pair of wings. This phenomenon is called flight dipterization.

Abdominal

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

covers

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

LECTURE 19. EXTERNAL AND INTERNAL STRUCTURE OF INSECTS

1. External structure

layers: exocuticles and endocuticles. The hard cover of the body limits the growth of the insect. Insects are characterized by molting. Covers are appendages. They are divided into structural and sculptural. The color of the insect is associated with the integument. Coloring is divided into chemical (pigment) and structural (physical). The value of color for an insect is direct (influence on internal processes) and indirect (impact on other animals). Types of coloration: cryptic - coloring of the resting posture, warning, frightening, mimicry. Derivatives of the hypodermis are wax glands, odorous, poisonous, varnish and others.

2. Internal construction

Muscular system

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

fat body

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

LECTURE 19. EXTERNAL AND INTERNAL STRUCTURE OF INSECTS

2. Internal structure

body cavity

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

Digestive system

Three sections: anterior, middle and hindgut. Between the anterior and middle intestines is the cardiac valve, the middle and hindgut is the pyloric valve. The anterior intestine is represented by the pharynx, esophagus, goiter, mechanical stomach. Depending on the food consumed, variations in the structure are possible: there is no goiter, stomach. Goiter - a place of temporary residence of food, partly digestion takes place here; The function of the stomach is to crush (grind) food. The pharynx of insects that feed on liquid food is muscular and acts as a pump. The salivary glands open into the oral cavity, usually near the base of the lower lip. Enzymes contained in saliva provide the initial stages of digestion. In blood-sucking insects, saliva contains substances that prevent blood clotting - anticoagulants. In some cases, the salivary glands change their function (in caterpillars they turn into spinning glands). The middle (small) intestine is where food is digested and absorbed. In the initial section of the intestine in some insects (cockroach, etc.), several blind protrusions of the intestine flow - pyloric appendages - they increase the suction surface. The walls of the middle intestine form folds - crypts. The type of digestive enzymes depends on the diet of insects. The secretion of enzymes in insects is holocrine and merocrine. The epithelium of the midgut in many insects secretes a peritrophic membrane around the contents of the intestine, the role of which is important in the processes of digestion and absorption of nutrients. In addition, it protects the midgut epithelium from mechanical damage. The posterior (rectum) intestine is often distinguished by its considerable length and is subdivided into several sections. This is where most insects have their rectal glands. Functions of the department: the formation and removal of excrement, the absorption of water from the food mass, the digestion of food with the help of symbionts (typical for the larvae of some insect species). The intestines are separated by valves that prevent the reverse flow of food. The anterior and middle sections are separated by the cardiac valve, the middle and posterior by the pyloric valve.

But a diagram of the organ system of insects. How many body parts do insects have: external structure

The general structure of the body of insects (with a diagram and pictures)

Insect head structure

The main types of pairs of antennae in insects

Types of mouthparts of insects

Types of insect legs: structure and main types of limbs (with photo)

The main types of insect wings: photo and structure

Digestive system of insects

excretory system of insects

Respiratory system of insects

Insect circulatory system

Nervous system of insects

Sense organs of insects

reproductive system of insects

Head

Thoracic

Abdominal

covers

Muscular system

fat body

body cavity

Digestive system

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