Class Insects. General characteristics, internal and external structure, the structure of a simple eye and a complex compound eye, reproduction, diversity and significance of Insects
Class Insects (Insecta). Structural features, digestion, respiratory and excretory systems, sensory organs and representatives
The cuticle of insects is covered with a thin layer of a fat-like substance that prevents the body from losing moisture. On the surface of the cuticle are mobile hairs, scales, bristles.
The body consists of a head, chest and abdomen. On the head are a pair of jointed antennae, oral organs (a pair of upper jaws, a pair of lower jaws, a lower lip), a pair of compound compound eyes, there may be 1–3 simple eyes. The area between the compound eyes is called forehead . On the sides under the eyes are cheeks . The back of the head is called back of the head . The head is movably connected to the thoracic region.
The chest consists of three segments. They have 3 pairs of limbs that extend from each thoracic segment and are movably attached. The types of limbs depend on the lifestyle: walking, running type (for beetles), hocking (for grasshoppers), digging (for bears), swimming (for swimming beetles). On the last leg segment there are claws, and in some species there are also suckers.
Many insects (adults only) have wings (a fold of skin filled with hemolymph) that are attached to the second or second and third thoracic segments. On the wings, transverse and longitudinal veins are developed, which form the supporting frame. In the middle of the veins are the trachea and nerves. The shape and structure of the wings are varied. In many species, the first pair of wings is modified into rigid elytra that protect the hind, membranous, often transparent wings from injury. In the order Diptera, only the first pair of wings is developed. The second is modified into club-shaped appendages that provide a certain frequency of wing beats, stabilize the balance of the insect in flight and are called halteres . There are two types of flight in insects: flapping and soaring. Flight is ensured by the coordinated work of the pectoral and wing muscles. By rapidly working with their wings, some insects are able to hover in the air (flies, dragonflies, etc.).
The abdomen consists of several segments (4-10) and the anal plate. It contains most of internal organs. Each segment has a pair of spiracles. The limbs are missing. In some species, they are modified into an ovipositor, a stinger, etc. Paired appendages of the last segment of the abdomen are called churches.
Digestive system of insects
Class Insects (Insecta). Types of mouthparts: gnawing type (grasshopper), sucking type (butterfly) and licking type (fly)
Gnawing mouthparts is considered the most ancient (characteristic of primitive insects) and is common among insects that feed on solid plant or animal food (beetles, cockroaches, orthopterans, etc.). From above, the mouth opening of such an apparatus is covered with an unpaired plate (upper lip), on the sides there are paired upper and lower jaws, from below - an unpaired lower lip. The upper lip is formed by a cuticle fold. The upper jaws are represented by plates with teeth on the inside. The lower jaws consist of two segments. On the upper segment there is a pair of ruminant lobes and a mandibular dissected palp (an organ of touch and taste). The lower lip was formed by the fusion of the lower jaws, consists of two segments and has a pair of lower labial palps, two pairs of ruminant lobes.
piercing-sucking the apparatus is characteristic of insects (bugs, mosquitoes, etc.) that feed on liquid food: the juice of plants, tissues, and the blood of animals.
Sucking mouthparts in the form of a long tube of two halves found in butterflies that feed on fruit juice, flower nectar. Flies have a peculiar mouth apparatus with a fleshy lower lip - licking (modified sucking).
Gnawing-licking mouthparts found in Hymenoptera (bees, wasps, etc.). These are mouth organs that have extended into a proboscis for sucking nectar. Wherein upper jaws remained almost unchanged (reduced ruminant cloves) and serve for the structure of the cells. Sometimes adult insects do not feed (silkworm), their mouth organs do not function, they can be reduced.
Digestive system consists of the oral cavity, pharynx, esophagus, large goiter, muscular stomach (in insects that feed on solid food, the walls are thick with chitinous teeth or plates for grinding food), midgut, hindgut, which ends with an anus.
The ducts of the salivary glands open into the oral cavity. Their secret wets and partially dissolves solid food. In bees, the secretion of the salivary glands, when mixed with nectar, turns into honey. In caterpillars of butterflies, hymenoptera larvae and some other insects, the salivary glands are modified into silk-secreting or spinning glands. Silk thread is allocated for building a cocoon, protective formations, etc.
Worker bees feed the larvae of the future queen with the secret of the pharyngeal glands.
The middle intestine is lined from the inside with a glandular epithelium that secretes digestive juice. Insects do not have a liver. Some insects are capable, like spiders, of extraintestinal digestion (ladybug larvae, swimming beetle, etc.).
excretory system of insects
Excretory organs - Malpighian vessels (blindly closed tubes that protrude into the digestive system between the middle and hind intestines), fatty body (has a whitish, yellowish or greenish color and, in addition to the excretory - accumulation kidneys, performs a storage function).
The circulatory system of insects
The circulatory system is not closed. The heart is tubular, multi-chambered, located on the dorsal side of the abdomen. A pair of openings with valves opens into each chamber. Several chambers are capable of pulsing. Anterior to the heart is a single blood vessel, the aorta. Blood from the heart enters the aorta, from it - into the cavity of the head, and then - into the spaces between the organs. Blood (hemolymph) is colorless, greenish-yellow, sometimes red, does not take part in the transport of gases.
Respiratory system of insects
Breathe with trachea. They branch and braid all organs, they even enter individual cells in the form of tracheoles. 10 pairs of spiracles open outward or stigma - openings on the sides of the abdomen and chest. In the anterior part of the abdomen, the breasts of the trachea expand and form air sacs. Through the trachea, gas exchange takes place (oxygen is absorbed, carbon dioxide is excreted), water vapor is removed. Breathing is carried out due to the rhythmic contraction and stretching of the lateral and longitudinal muscles of the abdomen. The larvae of some insects breathe with tracheal gills (dragonflies, ephemera). These are formations on the surface of the body or in the hindgut, which look like petals with branched tracheae in the middle. The tracheal system is closed (no spiracles). Oxygen enters the trachea from the gills.
Nervous system of insects
It consists of the subpharyngeal (formed by the fusion of three ganglia) and supraesophageal ganglia, connected by circumpharyngeal connectives, and the ventral nerve circuit. The subpharyngeal node innervates the oral organs and the anterior intestine. The abdominal chain is formed by three thoracic ganglia and eight abdominal. In some highly organized insects, neighboring nodes of the ventral nerve chain merge by combining the thoracic ganglia into one large node. Abdominal nodes can merge into 2 - 3 or 1 large node (in flies, lamellar beetles). The thoracic ganglia regulate the work of the legs and wings.
A special development forms the supraesophageal ganglion. It forms the brain, which includes three sections: anterior, middle and posterior. Innervates antennae, eyes (has a pair of large visual lobes on the sides). In the anterior section, a pair is very well developed. stalked or mushroom-shaped , tel. It is believed that they are responsible for the behavior of insects.
The complex structure of the nervous system causes complex behavior.
Sense organs of insects
On the head - 1 pair of antennae (organs of smell and touch). Diverse structure of the antennae: comb-shaped, club-shaped, filiform, lamellar, bristle-shaped, serrated, etc. The organ of vision is compound (faceted) eyes, sometimes there are simple ones (1 - 3). Each compound eye consists of a large number of facets (several thousand). Most insects do not perceive red, but perceive well ultraviolet radiation. Simple eyes (not capable of perceiving an image) react to the degree of illumination, can perceive polarized light. Insect larvae with complete metamorphosis have lateral ocelli (from one to several pairs). Each such eye can perceive images of objects. The body, limbs are covered with hairs, scales, which are receptors for taste, touch, etc. Some insects have an organ of hearing (in grasshoppers - on the front pair of legs, etc.).
Insect breeding
Types of development of insects. Complete transformation (development with metamorphosis) and incomplete transformation (development without metamorphosis)
They reproduce only sexually (with or without fertilization). The reproductive organs are developed only in adult insects (imagoes). Insects are dioecious. In many species, sexual dimorphism is well expressed (beetle - deer, butterflies, etc.). The reproductive organs are located in the abdomen. In females, they are represented by tubular ovaries, oviducts, additional sex glands, and a seminal receptacle. At the end of the abdomen, females have an ovipositor for laying eggs. In some insects of the order Hymenoptera, it is turned into a sting with a duct of a poisonous gland inside.
In males, the reproductive system is represented by a pair of testes, vas deferens, vas deferens, and additional genital organs. A copulatory apparatus may be developed at the end of the abdomen. Fertilization is predominantly internal.
The genital opening is one, since the ducts of the sex glands merge. Some insects are characterized by mating behavior (competition for a female, etc.).
Most insects lay eggs, sometimes they are viviparous (they give birth to live larvae - aphids, gadflies, etc.). Eggs are covered with a thick shell, inside they contain a supply of nutrients (yolk). They are laid by females singly or in groups on different surfaces, in soil, water or in animals, etc. Insects are very prolific (bees lay up to 1.5 million eggs daily for 10-12 years; termite uterus - over 30 thousand eggs) . They can have several generations per year (depending on the species, conditions of existence).
Development with transformation (complete and incomplete). stages incomplete transformation : egg - larva - adult insect (imago) . They are characteristic of cockroaches, bedbugs, lice, orthopterans, etc. Insect larvae with incomplete metamorphosis are outwardly similar to an adult insect, but are smaller (after each molt they look more and more like an adult), mainly live where adults do, feed on the same food. Sometimes the larvae live in a different environment (dragonflies, etc.), then they have certain adaptations and differ somewhat from adult insects.
stages complete transformation : egg - larva - pupa - adult insect (imago). They are characteristic of Lepidoptera, Hardoptera, Hymenoptera, Diptera, and others. appearance, neither in a way of life is similar to an adult insect. The larvae of such insects never have complex eyes, the limbs are mostly absent or underdeveloped, the mouth apparatus differs from that of adults, and they feed on different foods (which reduces competition with adults). The larvae of some species may have special larval organs (caterpillar silk glands, etc.). The pupa is immobile and does not feed. In it, the complete destruction of the tissues of the larva and the formation of new ones, characteristic of an adult insect, occur. Not only destroyed nervous system, rudiments of the sex glands and special structures - imaginal discs , due to which the organs of an adult insect are formed.
The development of some insects can be very short, and in certain types last several years (May beetle, etc.).
The insect class is divided into approximately 30 orders.
Squads of Insects
Types of development of insects. Development of insects with incomplete transformation: egg - larva - adult insect (adult). Development of insects with complete transformation: egg - larva - pupa - adult insect (adult)
- Order Orthoptera (Orthoptera). Representatives: green, gray grasshoppers, locust, bear and others.
- Detachment Cockroaches (Blattoptera). Representatives: black beetle, red cockroach or Prussian, Madagascar hissing cockroach, american cockroach and others.
- Squad Termites (Isoptera). Representatives: mediterranean termite or harmful and etc.
- Squad Lice (Anoplura). Representatives: head louse, cootie and etc.
- Order Hemiptera or Bedbugs (Hemiptera). Representatives: bugs-turtles, pine bark bug and etc.
- Order Homoptera (Homoptera). Representatives: mountain cicada and etc.
- Dragonfly Squad (Odonata). Representatives: dragonflies, beauty dragonflies and etc.
- Order Beetles or Hardwings (Coleoptera). Representatives: ladybug, ground beetle, Chafer, Colorado beetle , stag beetle, swimming beetle and etc.
- Order Lepidoptera or Butterflies (Lepidoptera). Representatives: swallowtail, cabbage butterfly, silkworm and etc.
- Order Hymenoptera (Hymenoptera). Representatives: bee, wasp, bumblebee, ant and etc.
- Order Diptera (Diptera). To long-whiskered Diptera relate mosquitoes, midges, mosquitoes etc. K short-whiskered Diptera – flies, gadflies and etc.
- Order Fleas (Aphaniptera). Representatives: human flea, rat flea and etc.
Meaning of Insects
The diversity and importance of insects
They are an important link in natural biocenoses. Biomass is superior to all other animals.
Class Insects. Cereal pests: Bread beetle (Kuzka beetle), Cereal fly, Corn beetle, Thrips and Grass aphid
Honey, royal jelly, bee venom, glue are obtained from the honey bee. Wax is widely used in industry (metallurgy, chemical production, electrical engineering). Silk is obtained from the silkworm.
Many species of insects are pests of agricultural and forest crops. About 300 species belong to dangerous pests of cultivated plants (May beetle, mole cricket, beet weevil, ringed silkworm, gypsy moth, winter scoop, cabbage scoop, pea weevil, Colorado potato beetle, etc.). About 200 species of insects damage human food supplies (peas and beans - grain beetles, flour - caterpillar of the mill moth, grain - grain moth, some weevils, etc.). Wooden products, buildings, plants are damaged by termites. Fur products, woolen - domestic moth, leather - leather beetles.
Insects are our constant companions in life. No matter how they sterilize the operating rooms, at least some fly will fly in, and even in houses they are always in in large numbers… For robotics engineers, insects are an inspiration, because only they can move on any surface, but it is very difficult to repeat this in an artificial model.
Like others, insects have an external (exo-) skeleton consisting of chitin. Outgrowths are often observed on the integument of the body - hairs, horn formations, scales, etc.
Body: head, thorax and abdomen separately. 3 pairs of walking legs. Most insects have wings(usually 2 pairs).
Features of the internal structure of insects
There are terrestrial insects, there are also aquatic representatives, so there are differences in respiratory system:
- in aquatic insects, breathing is carried out by the entire surface of the body;
- in terrestrial - respiratory organs - trachea.
Circulatory system: open circulatory system , insect blood is called hemolymph. The main vessel containing the hemolymph runs along the length of the insect in the dorsal part. The back of this vessel contains a "heart" - several pulsating chambers connected in series with each other.
Digestive system:
1. A very interesting oral apparatus - in various kinds it is different:
- gnawing- in those insects that eat solid food, or this food must be obtained (gnawed out);
- sucking (piercing-sucking) - for taking liquid food (butterflies and mosquitoes);
- muscoid (both gnawing and sucking like flies)
2. A system consisting of the stomach, intestines, rectum and anus.
excretory system:malpighian vessels(similar to arachnids).
Features of the structure of the nervous system of insects and sensory organs:
Insects have a very intense movement, and not chaotic, but quite purposeful, so such movement must be well coordinated. Insects already have a real nervous system - ganglion, consisting of three departments - the nerve node, the ventral nerve cord and a network of neurons throughout the body.
- antennae (antennas) - organs of touch;
- eyes - can be faceted (complex) and simple, but then there should be several of them.
- insects perceive and distinguish smells well (they have the basis of communication - the isolation and recognition of various chemicals).
reproductive system:
Insects are dioecious. Fertilization is mostly internal.
Development takes place as
Insects are very closely related to many other organisms on Earth.
For them - irreplaceable pollinators, for animals - food.
The class Insects unites more than 1 million species of arthropods, which are characterized by the division of the body into three sections: head, chest and abdomen. There are three pairs of legs on the chest, the abdomen is devoid of limbs. Most have wings and are capable of active flight.
© External structure. On the head of insects there are complex (faceted) eyes, in some species, in addition to them, there are also simple eyes. There are four pairs of appendages on the head: the first pair is the antennae (antennae), the organs of smell, the remaining three pairs form the oral apparatus. The upper lip covers the upper jaws. The second pair of oral appendages form the upper jaws, the third pair - the lower jaws, the fourth pair grows together and forms the lower lip. There may be a pair of palps on the lower jaw and lower lip. The oral apparatus includes the tongue - a chitinous protrusion of the bottom of the oral cavity. Due to the type of nutrition, mouthparts may be various types(Fig. 128):
¨ gnawing type - characteristic of insects that feed on hard plant foods (beetles, orthoptera, cockroaches, etc.) - the most ancient, original type of oral apparatus;
¨ gnawing - sucking mouthparts in bees;
¨ piercing - sucking mouthparts in bedbugs, mosquitoes;
¨ sucking butterfly mouthparts;
¨ licking mouthparts in flies.
The thorax consists of three segments: prothorax, middle and metathorax. Each segment has a pair of legs; on the mesothorax and metathorax in flying species there are most often two pairs of wings. The limbs are jointed, forming a system of levers with the help of the joints. In connection with the way of life, the legs are running, jumping, swimming, digging, grasping 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, lower insects have paired limbs; in higher insects, they are modified into an ovipositor or other organs.
The integuments consist of cuticle and hypodermis, which protect insects from mechanical damage, water loss, and are the outer skeleton.
Muscles of insects histological structure belong to the striated, they are distinguished by high differentiation and the ability to have a very high frequency of contractions (up to 1000 times per second.)
© Digestive system begins with the oral limbs and the oral cavity, into which the ducts of the salivary glands open. The salivary glands can change and produce a silky thread, turning into spinning glands (in the caterpillars of many species of butterflies). The anterior intestine includes the pharynx, esophagus, some insect species have an extension - goiter. In species that eat solid food, there is a chewing stomach behind the goiter, in which there are chitinous folds - teeth that help grind food. The midgut may have blind outgrowths that increase the absorption surface. The hindgut ends with an anus. On the border between the middle and posterior intestines, the intestinal lumen opens numerous blindly closed Malpighian vessels (Fig. 129).
In many insects, protozoa and bacteria that can digest fiber settle in the intestines. Among insects, there are omnivorous species (cockroaches), herbivorous, predatory. There are species that feed on carrion, decay products - manure, plant debris. Some species have adapted to digest such little nutrients like wax, hair.
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Rice. 130. The structure of the trachea of insects.Actively moving insects can perform respiratory movements by expanding and contracting the abdomen. Many larvae living in water (dragonflies, mayflies) have so-called tracheal gills, no stigmas, the tracheal system is closed. Some larvae living in water have gills that do not have tracheae, gas exchange occurs only through the integument, in these cases oxygen is transported by the hemolymph.
Circulatory system relatively poorly developed in insects. The heart is located in the pericardial sinus, on the dorsal side of the abdomen, and 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 to ensure its contraction. The hemolymph moves to the front of the body, into the only vessel - in head aorta- and poured into the body cavity. 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 (Fig. 131).
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 respiratory function of hemolymph is insignificant, but in some aquatic insect larvae (in bloodworms, mosquito larvae), hemolymph has hemoglobin, is colored bright red and is responsible for the transport of gases.
© excretory organs. In insects, these include the Malpighian vessels and the fat body. Malpighian vessels (up to 200 or more) absorb metabolic products from the hemolymph. The products of protein metabolism are converted into uric acid crystals, the liquid is actively reabsorbed by the vascular epithelium and returned to the body, and the uric acid crystals enter the hindgut. The fat body of 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 sparingly soluble uric acid.
© Nervous system. The CNS of insects consists of the brain, suboesophageal ganglion, and segmental ganglia of the ventral nerve cord (Fig. 132). The peripheral nervous system is represented by nerves extending from the central nervous system and sensory organs. The trend towards fusion of the ganglia continues; in some insects, the thoracic and abdominal segmental ganglia merge into the thoracic and abdominal ganglia. The most complex brain develops in social insects: ants, bees, termites.
The sense organs of insects are diverse and complex. They have compound eyes and simple eyes. Compound eyes are made up of ommatidian, the number of which varies among different insect species. In dragonflies, each eye consists of 28,000 ommatidia, in ants, especially in individuals living underground, the number of ommatidia is reduced to 8 - 9. Some insects have color vision, color perception is shifted towards short-wave rays: they see the ultraviolet part of the spectrum and do not see red colors. Mosaic vision. The role of simple eyes is not fully understood, but it has been proven that they perceive polarized light.
Many insects are able to make sounds and hear them. The organs of hearing 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.
The organs of smell are located mainly on the antennae, which are most developed in males. The organs of taste are 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.
On the entire surface of the body of the insect there are sensory cells that are associated with a 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 change, but where the organs that perceive these fields are located is still unknown.
© Reproductive organs. Insects have separate sexes. Many insects exhibit sexual dimorphism - males can be smaller (in many butterflies) or have a completely different color (gypsy moth butterflies), sometimes males have larger antennae, in some species separate organs develop strongly - the upper jaws of the male stag beetle. In males, there are testes in the abdomen, from which the vas deferens extend, ending in an unpaired ejaculatory canal. Females have two ovaries, they open into paired oviducts, which are connected below into an unpaired vagina.
During mating, the male's semen is introduced into the copulatory pouch and the seminal receptacle, from where it enters the vagina, where the eggs are fertilized. In some species, the spermatozoa in the seed receptacle remain alive for several years. In a queen bee, for example, a mating flight happens once in a lifetime, and she lives and lays eggs for 4-5 years.
Insects are known to have parthenogenetic reproduction (without fertilization). Female aphids throughout the summer from unfertilized eggs give birth to larvae from which females develop, only in autumn both males and females are formed from larvae, mating occurs, and fertilized testicles overwinter. From parthenogenetic testicles of social hymenoptera are formed by males. The sex glands of drones in bees remain haploid, and the body cells restore diploidy.
© Development insects is divided into two periods - embryonic, including the development of the embryo in the egg, and postembryonic, which begins from the moment the young animal leaves the egg. Postembryonic development occurs with metamorphosis; according to its nature, they are divided into insects with incomplete transformation and insects with complete transformation.
to insects with complete transformation include insects in which the larva differs sharply from the adult stage of the adult, 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. An adult insect emerges from the pupa. Insects with complete transformation in adulthood do not molt. Insects with complete metamorphosis include, for example, the following orders: Coleoptera, Hymenoptera, Diptera, Lepidoptera and others.
In insects with incomplete transformation the pupal stage is absent, a larva (nymph) emerges from the egg, similar to an adult insect, but the wings and gonads are underdeveloped. The larvae molt several times, and after the last molt, winged adult insects with developed gonads appear. Insects with incomplete transformation include, for example, the orders: Cockroaches, Praying Mantises, Orthoptera, Lice, Homoptera and others.
In insects of the order Coleoptera(Coleoptera) the first pair of wings is transformed into rigid elytra, mouthparts of a gnawing type. At Maybug larva development continues underground for several years. The larva has a well-pronounced head with a gnawing type of mouth apparatus, three pairs of jointed limbs, completely unlike a beetle. The first year the larva feeds on humus, the second - on the roots of grasses, the third - on the roots of shrubs and trees, which cause great harm to young tree plantations. In the fourth year, at the end of spring, the larva turns into a chrysalis and in the autumn a young beetle emerges from the pupa. The beetle emerges on the surface of the soil in the spring of next year. Larvae of bark beetles, barbels, bring great harm to the forest and garden, damaging the wood of trees, the Colorado potato beetle is a dangerous pest of potatoes, the leaves of which feed on both larvae and adult beetles. The larvae of click beetles are called wireworms, they harm cereal crops by gnawing the roots. Bread beetles they feed on soft grains of cereals, and their larvae gnaw on the roots.
Predatory beetles are of great benefit ground beetles, ladybugs and their larvae that feed on aphids. Many beetles are orderlies, clearing nature of corpses and manure ( scarabs, dung beetles, dead eaters, gravediggers).
Butterflies have a sucking-type oral apparatus, two pairs of large wings are covered with chitinous scales that form bizarre and complex patterns. Coloring may be cautionary warning about inedibility, patronizing expressed in resemblance to a protected animal or inedible object. At the same time, the color is identification character.
Butterfly larvae - caterpillars - have a worm-like shape, on the head there is a gnawing mouth apparatus. On the thoracic segments, they have three pairs of segmented legs, the rest are unsegmented false legs. Among Lepidoptera there are many species whose caterpillars are pests of forests and gardens. Feeding on the leaves they bring huge harm deciduous trees. Visiting flowers, Lepidoptera play an essential role in pollination. Silkworm used by humans to produce natural silk. Currently, the silkworm is not found in the wild.
Many Lepidoptera have become rare and are listed in the Red Books.
The wings are membranous, two pairs, the second pair is smaller than the first, during flight they are linked into a single flying surface with the help of hooks. The head has a pair of compound compound eyes and three simple ocelli. Among them there are pests ( sawflies, horntails, nutcrackers), and species useful to humans. domestic bees are suppliers of honey, wax, propolis; bumblebees- excellent pollinators, ants destroy a huge number of harmful insects.
Riders ( trichogram, telenomus, white-tailed rider) lay their testicles in the eggs of other insects ( egg-eaters), into their larvae ( larvae) and even in adult insects ( imagoes). The larvae that emerge from them eat their prey, reducing the number of insects harmful to humans. The containment of harmful activities through the use of natural enemies is called biological control method.
This order includes the most highly organized insects with one pair of wings, the second pair is turned into an organ of balance - halteres. The mouthparts are stabbing or licking. The larvae are legless, in flies they are also headless. The negative value of Diptera is great: they are mechanical carriers of pathogens intestinal infections and helminth eggs; some Diptera are bloodsuckers and can carry pathogens of serious diseases. For example, tsetse fly- a carrier of the causative agent of sleeping sickness, mosquitoes- leishmaniasis, horseflies- tularemia and anthrax, malarial mosquito(genus Anopheles) - malaria.
Unlike other mosquitoes, the female malarial mosquito lays eggs singly, without sticking them to each other. The eggs have air chambers and float on the surface. The eggs hatch into larvae that are parallel to the surface of the water, and not at an angle, like the larvae of peeping mosquitoes (Culex genus). When landing, the belly of the malarial mosquito is at an angle to the surface (Fig. 133), while that of the pisk mosquito is parallel to the surface. But also mosquitoes of the genus Culex on Far East spread a serious viral disease - Japanese encephalitis.
Great harm to livestock gadflies. These large flies do not feed, their mouth apparatus is not developed. Some lay their eggs or larvae on the surface of the body of sheep, horses, cattle. Others - in the nasal cavities of animals. The larvae settle under the skin, in the stomach, nasopharynx, frontal and maxillary sinuses, bring great suffering to their owners. Eventually, the larva enters the soil, where it pupates.More than 20,000 species of insects with incomplete metamorphosis. The hind legs are of a jumping type, gnawing mouthparts are characteristic.
Of this order, the most famous are insects from the Grasshopper family, the Cricket family, the Medvedka family, and the Locust family. Grasshoppers have long antennae, feed on plant and animal food, and are usually green in color. Some species of locust bring great harm to agriculture, destroying crops on hundreds of hectares. Their antennae are short, the ovipositor is short, hook-shaped. Bears bring tangible harm, often damaging the underground organs of plants.
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2. Features of the vital activity of insects
The body of insects is divided into 3 sections - the head, chest and abdomen. The head is equipped for the most part with a pair of compound eyes, a pair of tentacles or antennae, and oral appendages surrounding the mouth opening. These appendages, in the form of upper and lower lips and 2 pairs of jaws, can change their shape in different orders and are either gnawing, then sucking, stabbing or lapping ..
Insects use almost any organic matter, both plant and animal origin, as food. They can feed on both solids and liquid substrates. Therefore, the original gnawing type of their oral apparatus has undergone significant changes aimed at the formation of various types of proboscis. For example, the oral apparatus of Hymenoptera retained the basic properties of the gnawing type. These insects have well-developed mandibles, which are so necessary for them to carry out construction work. Consider the exquisitely crafted honeycombs of domestic bees or the paper nests of social wasps. Solitary hymenoptera use various substrates in the manufacture of nests - they gnaw holes in wood, hard and even stony ground. [10.75-77].
Mandibles are also used when capturing and transporting victims by predatory wasps, and if necessary, this is a good protection organ.
However, these insects are able to feed on nectar or simply lick liquid from the surface. Actually their proboscis consists of two posterior pairs of jaws. They are elongated and, when folded together, form an almost closed channel, and even with a kind of piston inside. With the help of a proboscis, they are able to penetrate deep into the corolla of the flower to the nectary. The proboscis of butterflies is also intended for eating. But it is simpler in structure, differs, as a rule, in greater length and should be considered the most specialized. The possibilities of its use are limited - only for the use of liquid available food. They work on the principle of a pump. .
Another thing is the piercing-sucking proboscis. They independently occurred in different groups of insects, have features of originality in each of them. However, common to all is the presence of two channels in such a proboscis: one for the injection of saliva, the other for suction of food. Insects of several orders have piercing-sucking proboscis: blood-sucking dipterans, bedbugs, fleas, lice, homoptera proboscis. The principle of operation of such oral apparatuses is different, it can be called the principle of a syringe and a pump. The proboscis pierces the integumentary tissues of animals or plants, injects digestive enzymes or other biologically active substances through the salivary canal, and sucks food through the food canal. .
The chest of insects, fused from 2 segments, carries 3 pairs of legs and 2 pairs of wings.
The abdomen consists mostly of 8 segments.
The nervous system consists of the head ganglion, peripharyngeal commissures and the ventral nerve chain.
Excretory organs - in the form of tubules (Malpighian vessels), flowing into the intestine at the border of the middle and hind intestines.
The circulatory system is represented by one dorsal vessel - the heart, passing in front of the head artery; further, the blood from the vessel enters the sinuses between the tissues and individual organs.
Respiratory organs in the form of respiratory tubes or tracheas, consisting of: 2 lateral longitudinal trunks that communicate with the external environment through holes - spiracles that fit in pairs in the segments of the body, and a series of smaller branches of the airways scattered between all tissues and organs. .
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Insects are members of the arthropod phylum. Them characteristic feature is the presence of limbs, consisting of separate segments. The class Insects is the most numerous and contains about 1 million species. Cockroaches, grasshoppers, beetles, butterflies, wasps, bees - it is simply impossible to list them all! What features allowed them to become so widespread? The topic "Insects and their features" is very interesting. Let's study it in more detail.
Structure
The body parts that insects have (see photo in the article) are the head, chest and abdomen. There is a pair of antennae on the head, the length of which varies and serves as an important systematic feature.
miraculous transformation
It happens in a special way. In organisms with a larva, an imago is formed - an adult. Moreover, these two stages do not differ in morphological features except for size. This is how the development of such orders as cockroaches, orthoptera, termites, lice, bedbugs and praying mantises takes place.
Coleoptera and fleas have a different type of transformation - complete. Its essence lies in the fact that the larva at an early stage of development leaves the egg, turning into a chrysalis. At this stage, the destruction of the original organs and the formation of new ones. This is how an adult is formed. An important fact is that the larva and imago are not similar in appearance. For example, the Colorado potato beetle at the initial stage of development looks like a small worm.
Habitat
Characteristic signs of insects
Insects (photos show a variety of representatives) have signs by which taxonomists distinguish them into a separate class of the Arthropod type. These are three pairs of limbs and body parts (head, chest, abdomen), the presence of a pair of antennae on the head, the respiratory organs are the trachea, and the discharge is the Malpighian vessels.
Diversity and importance of insects
Which insect from the order Hymenoptera is social? Of course it's a bee. Its main significance lies in obtaining honey and bee bread from pollen.
Representatives of the order cockroaches fly very poorly, but they orient themselves well in space with the help of long antennae.
Locusts, mole crickets and crickets are orthopterous. This order includes both grasshoppers and crickets, which have special adaptations. This is the so-called mirror - a thin membrane - and a bow - a vein with teeth.
Insects belonging to the order Bedbugs have a flattened body on which wings are not formed. Their absence is compensated by the ability to easily jump a decent distance.
Insects are all representatives of the order of beetles, which have hard elytra that tightly cover the abdomen.
Who among us has not admired the fluttering flight of beautiful butterflies? They are also insects. They are not only beautiful. Many of them are useful. So, "leads" the whole production. It is artificially bred in many countries of the world. And the product of its vital activity is natural silk.
Thus, insects represent a class most of which are adapted for flight. Thanks Enough high level organizations, they have mastered all habitats, occupying their niche in the system of the organic world.
