home Plumbing Features of the external structure of insects depending on. The external structure of representatives of the class insects

Features of the external structure of insects depending on. The external structure of representatives of the class insects

Answers to school textbooks

This is the most diverse class of arthropods. The number of species exceeds 1 million, and nevertheless, some features of the external structure common to all insects can be distinguished:

The body consists of three sections: head, chest and abdomen; covered with chitinous cover;

There is one pair of antennae on the head; all head segments fused;

The chest always consists of three segments: anterior, middle, and metathorax;

Three pairs of walking legs (attached respectively to each segment of the chest);

A pair of complex (faceted) eyes is located on the sides of the head;

Most insects have wings, one or two pairs (on the second and third segments of the thoracic region);

The abdomen is segmented; the number of segments varies between species.

2. How many sections does the body of insects consist of?

The body consists of three sections: the head (formed by several merged segments); chest, consisting of three segments; abdomen, consisting of several segments (5-11), separated by notches.

3. How are the limbs of insects arranged?

On the head there is one pair of antennae (the organs of smell and touch) and the oral apparatus. The latter is formed by modified limbs (three pairs). The oral apparatus can be of several types - gnawing, piercing-sucking, licking, sucking.

On each segment of the chest there are paired legs: jumping (grasshopper), digging (dung beetle), swimming (swiss beetle), running (beetles). The second and third segments may have wings (modified integument folds). At the end of the abdomen, some representatives have modified limbs: a stinger, ovipositors.

4. What kind of wings do insects have?

5. How is the nervous system of insects arranged?

The nervous system of insects is built according to the type of the ventral nerve chain and reaches a very high level of development and specialization. The central nervous system includes the supraesophageal ganglion - the brain, the subpharyngeal ganglion and the abdominal nerve chain of paired ganglia. The brain consists of three sections: anterior, middle and posterior. There is a gray matter, consisting of the bodies of nerve cells (neurons), which is the basis of complex behaviors in insects.

6. Describe the structure of insect eyes.

Eyes can be either complex or simple.

Fixed compound eyes, consisting of facets, perceive the shape of objects. The number of facets is determined by the biological characteristics of insects. The eyes can perceive flashes with a frequency of 250-300 Hz (flickers per second!). Also, the eyes of insects can distinguish colors (butterflies, bees) and perceive the polarization of light.

Simple eyes can only distinguish light from darkness.

7. How do insects eat?

Among insects, there are omnivores, such as cockroaches, which feed on various plant and animal products. Many insects use various parts of plants as food, from the root to the fruit, inclusive. No less numerous are predatory insects that eat other insects, worms, mollusks, etc. There are species that feed on carrion, various kinds of garbage and decay products. There are also insects that specialize in extremely low-nutrient food - feathers, horns, wax, etc.

8. What is a hemolymph? What is its function?

Hemolymph is a colorless or yellowish liquid that circulates in the vessels and cavities of insects, the main function of which is to supply tissues and organs with nutrients.

9. How do insects breathe?

10. What are Malpighian vessels?

Malpighian vessels are thin tubes located in the body cavity, opening into the intestine at the border of the middle and hindgut. Metabolic products come from the hemolymph into the lumen of the Malpighian vessels in the form of a suspension (crystals suspended in water) and are excreted into the intestine. Water from this suspension is absorbed by the walls of the Malpighian vessels and the hindgut and returns to the hemolymph, and almost dry metabolic products, together with undigested food residues, are excreted through the anus.

11. What are the structural features of the reproductive system of insects?

Insects have separate sexes. Their sex glands are paired. In males, the testes are located in the abdomen, from which the vas deferens extend, flowing into the ejaculatory canal. The ovaries of females open into the oviducts, which are connected below into a single vagina. Fertilization is internal.

12. What role do insects play in nature and human life?

In nature, insects are the main pollinators of flowering plants.

Insects are one of the most important links in the cycle of substances in nature. They are part of various food chains.

By consuming plant foods, they turn it into animal proteins - food for other animals.

Many insects act as orderlies of the biosphere, destroying the corpses of dead animals and excrement (gravedigger beetles, dung beetles).

The importance of insects, especially termites and ants, in soil-forming processes is great.

Penetrating into the wound, the larva literally eats away the body.

The infamous tsetse fly is a carrier of sleeping sickness, often fatal to humans.

Insects are widely used in human economic activities. For example, bees are bred for honey, bee venom, propolis, wax; silkworm - for the sake of silk; varnish insects - to obtain insulating substances and carmine paint.

Some insects (for example, the rider) have found use in the fight against agricultural pests as their natural enemies.

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 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 wing of an insect 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.

Question 1. What are the features of the external structure and internal organization of insects?