General characteristics of insects. Class Insects. General characteristics of the head-thorax-abdomen connection in insects

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This part of the body has many variants of morphology, so it is quite difficult to talk about any absolute uniformity in its external structure.

Number of abdominal segments

In typical cases, it includes ten or eleven segments - “rings”, which are attached to each other and form the visceral section. The 11th segment is found only in bessiazhkovyh, bivostok and other primary wingless insects - the most primitive forms of insects. In highly developed species, the posterior segments are reduced or rolled into the body.

The number of abdominal segments also depends on the stage of development: they, as a rule, are present in the maximum possible number, while others have fewer.

In adults, they also often merge with each other and have uneven thickness, so those with a short abdomen and small body size are distinguished by the fact that on their visceral section the number of clearly distinguishable rings can be reduced to three. However, in most representatives of the insect class the average number of segments ranges from 5 to 8.

The first segment of the abdomen in Stalk-bellied (Hymenoptera) is called and merges with the posterior part of the thoracic region, and the second (in ants - both the second and the third) is transformed into a thin stalk. Thanks to this structure, the abdomen acquires greater mobility in relation to the insect, and it becomes more convenient for the insect to manipulate (bees) or inject injections (riders).

Segment structure

The cuticular rings of the visceral region have a structure reminiscent of the morphology. Each segment is divided into two parts in the shape of half rings - upper and lower. On the lateral sides of the body they are connected to each other using a thin elastic pleural membrane. (photo) The same movable structure is also found at the junctions of neighboring segments. This adaptation allows the abdomen to change quite significantly in size, stretching 2-5 times after eating or during maturation (in females).

Song insects - mayflies, cicadas - have air cavities in their abdomen. By stretching and contracting the pleural membranes, they pump and release air from the abdominal region, gaining the ability to reproduce characteristic sounds. And some, for example, worker ants of the genus Myrmecocystus, have special reserve organs within the abdomen, in which they large quantities accumulate food substrates for feeding the inhabitants of the nest and for their own nutrition. Being “filled”, the abdomens of these ants look like transparent golden drops several times larger in size and; as needed, insects regurgitate food for their fellow tribesmen, and then replenish their supplies again.

Atypical abdominal shape

Abdomen shape

The shape of the abdomen can be very different, and its features mainly depend on the lifestyle: the better the insect flies, the more streamlined and correct form at its visceral department. In order not to provide resistance when moving in the air, all appendages on the abdomen (primarily hairs) grow in the direction from front to back.

In addition to being cylindrical, the abdomen can be spherical, flattened in the superior-inferior direction, club-shaped, triangular in cross-section, etc. In most beetles it is thickened in the middle and narrowed towards the end, while its lower surface is almost flat, and its upper surface is convex.

In front, the abdominal section can directly pass into (butterflies), or be separated from it by a “stalk” (bumblebees) or a constriction, as in some ground beetles. In the posterior part, it most often tapers in a spindle-shaped manner, forming a rounded apex. However, for example, bark beetles are distinguished by a shortened, as if “chopped off” abdomen, shaped like a truncated cone. (photo)

Abdominal appendages in the form of modified limbs

and external formations of the abdomen

Based on their origin and purpose, all additional structures of the visceral region can be divided into three groups:

Due to the fact that various insects have different quantities abdominal segments, many appendages and organs do not have a “permanent” place and can be located in different parts of it. Most of them are located at the posterior end of the body.

() - holes closed by a thin membrane through which gas exchange occurs. They are located on each segment of the visceral section, on the sides, in the area of ​​​​the connection of the upper and lower semirings.

False legs

- reduced and modified limbs. They do not contain locomotor muscles and do not serve for movement in adults, but have a simplified structure and are actively used in true and false caterpillars. In addition, the body of insects at any stage of development may have reduced legs that do not perform functions or are generally presented in the form of outgrowths. For example, the caterpillar of the king walnut butterfly has a very unusual look (photo)

: in addition to the main false ones, on each segment of its abdominal section there are several reduced branched pseudopods. - articulated appendages located on the last segment of the abdomen in the form of a “tail”. There are two, rarely three, they come from a reduced 11th segment and can have different lengths: from almost invisible in a fly to very pronounced in a house cricket. Higher forms

insects are deprived of these additions.

Genital appendages and organs - Components reproductive system

, which are usually located on 8 or 9 segments. Conventionally, they are considered to be the main part of the abdomen. Moreover, sometimes the visceral segment on which they are located is separated into a separate genital segment. Accordingly, the rings lying in front of it are called pregenital, and behind them - postgenital. Depending on the characteristics of morphology, in many insects the abdomen can acquire additional significance. In caterpillars moving on false legs

, it is involved in the implementation of locomotor function. Special muscle bundles, responsible for increasing and decreasing body length, connect adjacent segments. Thus, by relaxing and tensing them “in rhythm” with walking, he accelerates his progress. The movable connection of the abdomen with the chest and the presence of a modified one in the Stalked-bellied animals make it easier for them to protect themselves. The luminescent organs of fireflies and the resonating cavities of cicadas help them in communication and security, and through accumulation nutrients ants - “honey barrels” are able to survive even in unfavorable conditions

deserts and semi-deserts.

Task 1. Do laboratory work. Subject

: "The external structure of an insect insect." Goal of the work : explore external structure

insects such as a cockroach or a large beetle.

1. Make sure that the workplace has everything necessary to perform laboratory work.

2. Using the instructions given in paragraph 26 of the textbook, complete the laboratory work.

3. Fill out the table.

Task 2. Fill out the table. Task 3. Color insect (red - circulatory organs; yellow - nervous system organs; green - digestive system organs) and label them.

Complete 4. Complete the table.

Digestive system, digestion, type of nutrition: mouth, pharynx, esophagus, stomach, intestines. Extracellular digestionmouth, oral cavity, pharynx, esophagus, crop, gastric stomach, midgut, hindgut, anusSense organsSense organs

Comparative characteristics of arachnids and insects
Comparable characteristic	Class
	Arachnids	Insects
Distribution and lifestyle	land and terrestrial arthropods	all habitats except seas and oceans
Body parts	cephalothorax and abdomen, no antennae, 2 pairs of mouth organs	head, chest, abdomen; 1 pair of compound eyes, 1 pair of antennae
Limbs: number, location, structure	4 pairs of walking legs	three pairs of legs or wings
Digestive system, digestion, type of nutrition	mouth, pharynx, esophagus, stomach, intestines. Extracellular digestion	mouth, oral cavity, pharynx, esophagus, crop, stomach, midgut, hindgut, anus
Respiratory system	lungs and trachea	trachea
Nervous system	cephalothoracic ganglion	large supraglottic node
Sense organs	well developed, there are several pairs of eyes	well developed
Reproduction and development	internal fertilization	dioecious insects

Task 5. Write down the numbers of the correct statements.

1. The class Insects includes all tracheal-breathing arthropods with three pairs of legs.

2. In all insects, the body consists of a head, chest and abdomen.

3. Insects have legs on their chest and abdomen.

4. Insects live not only on land, but also in water and soil.

5. Insects eat everything that contains organic matter. Some of them have even adapted to feed on wool, wood and beeswax.

6. Along with compound eyes, many good flying insects also have simple eyes.

7. Insect antennae are organs of smell.

8. Aquatic insects have developed gill respiration.

9. Excretory organs of insects - Malpighian vessels.

10. In insects, blood flows only through blood vessels.

Correct statements: 1, 2, 4, 5, 6, 7, 9.

Hymenoptera

Stag beetle

Diptera

Scorpio girls

The structure of insects. The body of adult insects, like all arthropods, is covered with a chitinous covering, which acts as an exoskeleton, and is divided into a head, thorax and abdomen, which distinguishes them from other arthropods. The segments of the head are fused into a common mass, the segments of the thorax and abdomen are more or less clearly distinguishable. The head and chest bear limbs, the abdomen sometimes retains only underdeveloped limbs, i.e. rudiments.In the larvae of many insects, the division of the body into sections is weakly expressed.

Locust head

lip Lower lip

Upper jaw.

Lower jaw

The mouth is located on the lower surface of the head or at its anterior end. On the sides of the head there are two large compound eyes, between which there may be several small ocelli. The head bears four pairs of appendages that form the oral apparatus. A pair of antennae, or antennae, consisting of one row of segments extends from its upper side.

Forebrain

Medium breast

The thorax of insects always consists of three segments calledanteriorly-, medium-Andrear-chest. The chest segments bear three pairs of walking limbs. The wide distribution of insects and their exploration of various habitats has led to the emergence of significant diversity in the structure of jointed limbs. The limbs of insects are a system of movably connected to each other.

Grasshopper

hom levers with a large number degrees of freedom, i.e. capable of varied and precise movements. Running legs most closely correspond to the described type. (bugs, cockroaches), most common among insects. In animals that can jump, such as grasshoppers, the femur and tibia of the back pair of legs are greatly extended. In burrowing insects - mole cricket- all legs, and especially the front ones, shorten, become massive and acquire powerful weapons of chitinous teeth. Swimming limbs are flattened in the form of an oar and equipped with a dense row of elastic paddle hairs ( swimming beetles).

Wasp medium

Autumn zhigalka

A characteristic feature of many insects is the ability to fly.Wings, one or two pairs, located on the second (mesothorax) and third (methothorax) thoracic segments and represent folds of the body wall. The wing has the appearance of a thin plate; it is two-layered.

Elytra

Dragonfly

swimmer

bordered

In different orders of insects, the fore and hind wings can be developed differently. Only in the least specialized insects (for example, dragonflies) are both pairs of wings equally developed, although they differ in shape. Beetles are characterized by the transformation of their front wings into thick and hard ones. elytra, which almost do not participate in flight and mainly protect the dorsal side of the body. Only the hind wings are real, which at rest are hidden under the elytra.

Movement

wings

Muscles

The movement of wings in insects is the result of the work of a complex apparatus 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.

The abdomen is the last section of the insect body. The number of segments included in its composition varies among different representatives of the class.

Blood

The muscular system of insects is characterized by great complexity and a high degree of differentiation and specialization of its individual elements. The number of individual muscle bundles often reaches 1.5-2 thousand.

Respiratory

Ladybug taking off

The nervous system of insects, like that of other arthropods, is built according to the type of ventral nerve chain, but can reach a very high level of development and specialization. Central nervous system includes the suprapharyngeal ganglion - the brain, the subpharyngeal ganglion and the abdominal nerve chain of paired nerve ganglia - ganglia. The brain consists of three sections: anterior, middle and posterior.

The sensory organs of insects can perceive a wide variety of irritations: mechanical, chemical, visual, sound, etc. Insects are capable of not only perceiving, but also making sounds. This feature is typical for representatives of many groups: straightcracker

lykh, Zhukov, Hymenoptera, butterflies etc. Chirping Orthoptera, for example, is due to the development of special devices, which are most often associated with wings. Yes, y grasshoppers these organs are located on the front wings, where the veins of the left wing acquire tooth-like projections and turn into the so-called bow, which the animal moves along the right wing.

Insect compound eye

Simple peephole

Feelings

body

cells

Pigment cells

The eyes consist of individual ocelli (facets), the number of which is determined mainly by the biological characteristics of the insects. Active predators and good flyers - dragonflieshave eyes with up to 28 thousand facets. At the same timeants, especially in working individuals of species that live underground, the eyes sometimes consist of only 8-9 ocelli.

In addition to complex (compound) eyes, many insects also have simple eyes that perceive only the intensity of light, and not images.

Crystal

Lens

Dragonfly eyes

The circulatory system of insects is not closed. In the abdomen above the intestines lies a long tube-shaped “heart”. Insect hemolymph is a colorless or yellowish liquid, the main function of which is to supply tissues and organs with nutrients.

Tsetse fly eyes

The respiratory organs of insects are a complex system trachea. On the sides of the mesothorax and metathorax and, in addition, on the abdominal segments there are up to 10 pairs of openings - spiracle. Air tubes permeate the entire body and deliver oxygen directly to tissues and cells, as if replacing blood vessels.

Horsefly eyes

Digestive system Reproductive system

Bumblebee collecting nectar

The digestive system of insects begins with the pharynx. Food is digested and absorbed in the intestine. In many herbivorous forms, symbiotic organisms (protozoa, bacteria, etc.) settle in the intestines, providing, for example, termites, breakdown of fiber.

Dead beetle

SHSHYAYSHSH

The food of insects is varied, it includes almost all substances of plant and animal origin. Among insects there are all

poisonous, such as cockroaches, which feed on various plant and animal products. Many insects are vegetarians, feeding on all parts of plants, from root to fruit inclusive.

Ground beetle - predator

No less numerous are insect predators that eat other insects, worms, mollusks, etc. Finally, there are insects that feed on carrion, various kinds of waste and rotting products: manure, rotting plant debris, etc. Some insects specialized in extremely low-nutritive food ( feathers, horn, wax, etc.).

The excretory organs are presentedMalpighian vessels- thin tubes that open into the intestines.

Reproduction of insects. Insects are dioecious. Their gonads are paired. In males, the abdomen contains testes, from which vas deferens extend into the ejaculatory canal. The ovaries of females open into oviducts, which are connected below into a single vagina. Fertilization is internal. Sperm in the female genital tract remain viable for a very long time. On the-

Dragonfly larva

Egg Larva

Adult

Caterpillar Pupa

For example, a queen bee, after mating, lays thousands of eggs throughout her life (4-5 years) without repeated fertilization.

Postembryonic development of insects proceeds either without transformations or with incomplete or complete metamorphosis. With direct development, characteristic of lower insects ( foot- ponytail, Campodea), from the eggs hatch individuals that differ from adults mainly in their small size and underdeveloped sexual characteristics

organs.In insects with incomplete transformation, for example,grasshoppersorlocusts, emerge from eggslarvaewith the features of an adult organism - imago. butterflies The larvae undergo several molts and eventually turn into adult insects without going through the pupal stage. With complete transformation, characteristic of , worm-like larvae emerge from the eggs, completely different from the imago. Having reached a certain age, they stop moving and feeding and soon turn into dolls

ku.

Inside it, a profound restructuring of the body occurs with the formation of tissues and organs of an adult insect.At the end of this process, the integument of the pupa bursts and the Dragonfly dit imago.

Stages of development in insects are strictly

are confined to a certain season of the year: this phenomenon is called

seasonal cycle.

Incomplete Variety of insects. Insect classtransformation is divided into two large groups - primarybut wingless and winged.Complete transformation TO

primary wingless include the most simply organized insects, such as

campodea, springtail, sugar silverfish

and others, living in the soil, under stones, in moss, in basements and cellars. Their sizes are small, some do not exceed 1 mm. Together with other soil-dwelling animals, primary wingless animals participate in soil formation.

Springtail smintur

Primarily unscratchedspringtail, SilverfishSilkwormIn social insects (antstermites etc.) well expressed polymorphism(external differences) depending on the functions performed in the family. For example, at

bees

distinguish between queen bees, worker bees and drones. After fertilization, females lose the ability to fly and produce

As special calculations have shown, at least 108 billion insects simultaneously live on our planet, i.e., for every person on Earth there are about 250 million different representatives of this class. Moreover, these are organisms that actively participate in a wide variety of biological processes.

The meaning of insects. The positive activity of insects in nature is primarily expressed in their pollination of plant flowers (about 30% of European flowering plants are pollinated by insects).

Insects are of great importance, especiallytermitesAndants, in soil-forming processes. These insects, as well as the larvae of many insects living in the ground, loosen the soil with their moves, contribute to its better ventilation, moistening, and enrichment with humus. The latter is associated with destruction

plant and animal residues that accumulate in abundance on the soil surface.

The role of insects is enormous as one of the most important links in the cycle of substances in nature. Many insects are part of various food chains. Knowledge of insect food chains allows them to be used to control other insect pests Agriculture.

The negative consequences of insect activity are no less significant. Yes, many

Bee dance

: * Working

Honey bee

Termite castes

Uterus

Colorado potato beetle

Caterpillars of cabbage white butterflies Blood-sucking mosquito

Examples of the use of insects in human economic activities are well known. Since time immemorial, the East has bred silkworm, from whose cocoons silk was made. People breed bees to produce honey, a number of medicines (propolis) and wax. Some insects, for example riders, have found application in the fight against agricultural pests (for example,blood aphids)as their natural enemies.

Making silk threads from silkworm cocoons

What are the features of the external structure of insects?

How many sections does the insect body consist of?

How are the limbs of insects constructed?

What kind of wings do insects have?

How does the nervous system of insects work?

Describe the structure of insect eyes.

How do insects eat?

What is hemolymph? What are its functions?

How do insects breathe?

What are Malpighian vessels?

Complete task No. 117 on p. 89 (Workbook).

Choose the correct answer. Test on p. 132-136, option 1 (Test tasks).

Think

Why do insects have a poorly developed circulatory system?

Why is the circulatory system not involved in the transport of gases throughout the body?

Laboratory work

Complete work No. 13 on p. 18-20 (Laboratory work).

Work with computer

Refer to the disk. Study the lesson material and complete the assigned tasks.

http://www.floranimal.ru/classes/2703.html(Insects. general characteristics.

Classification).

http://www.krugosvet.ru/enc/nauka_i_tehnika/biologiya/NASE-KOMIE.html (Insects. General characteristics. Role in human life).

The body of insects consists of three sections (head, thorax, abdomen). On the head there is one pair of compound eyes, sometimes simple eyes, a mouthparts formed by modified limbs, and antennae. The chest bears three pairs of walking legs, most have wings. Breathing is carried out using tracheas that penetrate the entire body. The circulatory system is not closed. Development in many forms is accompanied by a complex transformation from the larval stage to the adult organism. The lifestyle includes flying, running, burrowing and swimming insects.

Type Echinoderm* Echinoderms are inhabitants of the seas, mainly bottom-dwelling animals capable of slow movement. These include, starfish, sea ​​urchins holothurians.

The type includes about six thousand modern species. The sizes of echinoderms range from a few millimeters to 1 m (rarely more).

The ancestors of echinoderms and chordates are considered to be animals that separated from the group of ancient polychaetes.

The structure of echinoderms. The body of echinoderms is star-shaped, spherical or worm-shaped. The skeleton may be more or less underdeveloped. The genital and anal openings are located on opposite poles of the body.

Sea stars

Holothuria The integument of echinoderms consists of two layers: the outer - single-layer epithelium and the inner, formed by fibrous connective tissue, where various elements of the calcareous skeleton develop. U starfish the skeleton is formed by calcareous plates arranged in longitudinal rows and usually bearing spines protruding outwards. Body sea ​​urchins enclosed in a calcareous shell of rows of tightly connected plates with long needles sitting on them. The skeleton of holothurians is formed from small calcareous bodies different shapes

, scattered throughout the skin. The most characteristic featureechinoderms - (water-vascular It is represented by a ring canal surrounding the esophagus and five radial canals extending from it into rays.

The latter produce paired branches to the legs - thin, highly extensible tubes equipped with a suction cup on one side and a bubble on the other. The water-vascular system is connected to the external environment through a channel (with calcified walls) and a porous plate. The water entering the system is filtered through the pores of the plate.

Mobile echinoderms, using this system, can move by sticking to the ground; in immobile animals, gas exchange and excretion occur through the channels of the water-vascular system.

The muscles are developed to varying degrees - depending on the mobility and nature of the skin skeleton.

The nervous system of echinoderms has a radial structure: radial nerve cords extend from the peripharyngeal nerve ring according to the number of body rays.

Sense organs are poorly developed. Primitive ocelli are located at the ends of the rays of sea stars, and on the upper part of the body in sea urchins.The integument of echinoderms consists of two layers: the outer - single-layer epithelium and the inner, formed by fibrous connective tissue, where various elements of the calcareous skeleton develop. UThere are also organs of touch.

The circulatory system usually consists of two annular vessels, one of which surrounds

mouth, and the other is the anus, and radial vessels, the number of which is

coincides with the number of rays of the body. Diagram of the structure of a starfish

The respiratory organs of sea stars and urchins are cutaneous gills - thin-walled outgrowths on the upper side of the body. In a number of echinoderms, respiration occurs through the integument of the body or with the participation of the channels of the water-vascular system.

Structure diagram

sea ​​urchin

Intestines

The digestive system begins with the mouth, located in the middle of the lower surface of the body, it leads into a short esophagus, followed by the intestine. The anus is absent in some species.

Echinoderms do not have special excretory organs. The release of metabolic products occurs through the walls of the channels of the water-vascular system.

LegsThe genital organs have different structures. Most echinoderms are dioecious, but there are also hermaphroditic forms.Development occurs through a series of complex transformations. Bilaterally symmetrical echinoderm larvae swim in the water column; During the process of transformation (metamorphosis), animals acquire radial symmetry and switch to a crawling lifestyle.Many echinoderms have the ability toregeneration

(restoration) of body parts. For example, from one beam

starfish the whole animal can recover. Starfish regeneration Holothurians, or Sea cucumbers.

Nervous system of a starfish

Starfish class

Starfish

The body of starfish, as the name suggests, is shaped like a flat star with five or more arms. Along the underside of the rays there are longitudinal grooves in which numerous legs are located. Starfish move with the help of rays. The mouth is located in the center of the lower surface of the body. Having found large prey (for example, a mollusk), the starfish covers it with its body, turns out its stomach and presses it against the prey. Juices secreted by the stomach wall digest food. The short intestine leads to the anus, which lies on the upper surface.

Starfish live at the bottom of the seas, descending to great depths. They feed on bottom animals and organic remains.

Evasteria

mesh

Crossaster

Astroclex

Insects are a class belonging to the phylum Arthropods. The vast majority of arthropod species belong to insects. There are about 1.5 million species of insects. Compared to crustaceans and arachnids, they are more complex due to the fact that they are better adapted to living on land and have mastered almost all living environments here. They crawl on the ground, live in the soil, fly and jump. Some have even returned to life in water, but still breathe air.

Insects include beetles, butterflies, grasshoppers, mosquitoes, dragonflies, flies, bees, ants, cockroaches and many others.

The following general characteristics of insects can be given:

• The body is covered with a cuticle containing chitin(as with all arthropods).
• The body of insects consists of a head, thorax and abdomen. The chest consists of three segments. The number of abdominal segments varies depending on the species (from 6 to 10 segments).
• Three pairs of legs(6 in total), which grow from the chest segments. Each leg consists of several segments (coxa, trochanter, femur, tibia, tarsus). In some insects, the legs may be modified due to the fact that they perform some other function rather than walking (for jumping, digging, swimming, grasping). For example, grasshoppers' hind legs are more powerful and long and provide them with a good jump. And in mantises, the front legs are modified into grasping limbs, with which it catches other insects.
• Most insects have two pairs of wings. They grow from the last two segments of the chest. In a number of groups, the first pair of wings is modified into hard elytra (for example, in beetles).
• On the head there is one pair of antennae, on which the organs of smell and touch are located.
• Insect eyes are complex (faceted), consist of many simple eyes (facets). Such eyes form a mosaic image ( big picture made up of small parts).
• Insects have a more complex nervous system and behavior than other groups of arthropods, but their overall plan the structure is approximately the same. The brain (suprapharyngeal ganglion mass), peripharyngeal ring, and ventral nerve cord are distinguished.
• Insects can eat in different ways. In the process of evolution, they formed different oral apparatus(gnawing, sucking, filtering and other types). In any case, the formation of the oral apparatus involves the upper and lower lips, a pair of upper and a pair of lower jaws, as well as a chitinous tongue.
• The digestive system consists of the oral cavity, esophagus, crop (not always), stomach, midgut, hindgut, anus. IN oral cavity and the midgut there are various glands that secrete digestive enzymes. In the stomach of an insect, food is mainly crushed using hard chitinous formations. Digestion occurs in the midgut, which, at the border with the stomach, has blind processes in a circle that increase its surface.
• The excretory system is represented only Malpighian vessels. These are tubes, one end of which flows into the hindgut, and the other is in the body cavity and is blindly closed. Through the walls of the Malpighian vessel, waste products that need to be removed from the body are filtered from the body cavity in which blood flows. They exit the hindgut along with undigested food debris. Most harmful substances The body isolates insects in the so-called fat body (but its main function is the supply of nutrients).
• The respiratory system consists only of trachea- branched tubes penetrating the body. They open outward on each segment with a pair of holes.
• The circulatory system is not closed, i.e., blood flows from the vessels into the body cavity, and then collects again in the vessels. The blood is pushed by the heart, located on the dorsal side of the abdomen. From the heart, blood flows towards the head. From the head, blood flows in the abdominal direction through the spaces between the organs. Then it is collected again into vessels going to the heart. Blood is involved only in the transport of nutrients from the intestine and excretion harmful products vital activity from cells. Oxygen enters the tissues of the insect's body directly from the trachea. They also release from tissues carbon dioxide. Despite the fact that the tracheal respiratory system for arthropods is considered more advanced, and the trachea permeates the entire body of the insect, this type breathing prevents insects from increasing in size. A large body cannot be fully supplied with oxygen using tracheas.
• There are two types of insect development: with complete transformation and with incomplete transformation. In insects with complete transformation into life cycle Metamorphosis is observed when the larva, unlike adults, changes greatly through pupation and becomes an adult, sexually mature insect. This development allows larvae and adults to feed and live in different places, which reduces competition between them. Insects with incomplete metamorphosis do not undergo metamorphosis in their life cycle. They emerge from eggs looking similar to adults. As the young grow, they molt several times and develop reproductive organs.
• For historical development life on Earth (evolution), many insects entered into a kind of symbiosis with flowering plants, becoming their pollinators and feeding on their pollen and nectar. This is what determined their external structure (especially the structure of the oral apparatus) and all the diversity and beauty of plant flowers. Many types of insects pollinate only certain types of plants, the flower of which is adapted for pollination only by that type of insect.