In insects, larvae hatch from eggs. Development and reproduction of animals. Butterfly development: four stages of the life cycle
The cockroach, like representatives of some other orders of insects ( Mayflies, Dragonflies, Mantises, Stoneflies, Orthoptera, Earwigs, Lice, Homoptera), development occurs dream complete transformation . This means that larvae emerge from the eggs - small insects that look very similar to their parents. They differ from adult insects in their smaller size, lack of wings and underdeveloped reproductive system. The larvae molt several times, grow with each molt and become more and more like adult insects. Over time, they become sexually mature and their wings are fully formed. After this, the insects no longer grow.
Thus, an insect with incomplete metamorphosis goes through three stages in its development: egg -> larva ->adult insect (Fig. 101).
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Orthoptera. This group includes locusts, grasshoppers(Fig. 102, 3 ), crickets And mole crickets. They have two pairs of wings (the front ones are denser than the hind ones), many have jumping hind limbs, and a gnawing mouthparts. Many of the Orthoptera jump in heights of up to 80 cm, and if they help themselves with their wings, the distance they cover in one jump reaches 10 m. Some types of locusts fly well. Locusts feed on plants, grasshoppers are both herbivores and carnivores, and crickets are omnivores.
Homoptera. This group belongs to cicadas(Fig. 102, 6 ) And aphids. Their mouthparts are of the piercing-sucking type, and their wings are usually folded into a roof. Homoptera feed on plant sap. Cicadas are fairly large (up to 7 cm long) diurnal insects and are known for being able to make very loud sounds using special bodies located at the base of the abdomen. Aphids are small insects several millimeters long. Among them there are both winged and wingless forms.
Bedbugs, or Hemiptera. Insects of this order are so called because their fore wings (elytra) are dense in front and soft in back (Fig. 102, 2 ). The second pair of wings lies under the first. It is with the help of the second pair of wings that bedbugs can fly. Some, for example bed bug, wings are missing. The mouthparts of bedbugs are piercing-sucking. Among bugs there are species that feed on plant juices, there are predators and bloodsuckers (bed bugs).
Insects with complete metamorphosis
In insects with complete metamorphosis, the larvae do not at all resemble adults. These are the larvae butterflies, beetles, flies, wasps, ants. These larvae lack compound eyes, have only simple ocelli, or have no visual organs at all; the body is most often worm-shaped (butterfly caterpillars). Often there are no antennae and no wings. Insect larvae with complete metamorphosis molt several times and grow. Having reached its maximum size, the larva turns into doll - This is another stage of development, usually motionless, intermediate between the larva and the adult insect.
Thus, insects with complete transformation go through four stages in their development: egg -> larva ->doll -> adult insect (Fig. 103).
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Beetles, or Coleoptera(Fig. 104, B). Representatives of this order have dense, hard elytra that cover the second pair of leathery wings, with the help of which they fly. The mouthparts are gnawing. Among the beetles there are many herbivores. There are also predators that hunt other insects and carrion eaters. Beetles live in the ground-air environment (on plants, the surface of the earth, in the soil) and in water. Beetle larvae are both very mobile predators, living openly, and sedentary, worm-like, living in shelters and feeding on plants, fungi, and sometimes decomposing remains of organisms.
Diptera(Fig. 104, IN). These insects have only one pair of wings. The second pair is greatly reduced and serves to stabilize the flight. This group includes mosquitoes And flies. Some dipterans have a licking ability oral apparatus, others have a piercing-sucking apparatus. Among the dipterans there are those that feed on pollen and nectar of flowers (syrphid flies), predators (ktyri) and bloodsuckers (mosquitoes, midges, midges, horseflies). Their larvae live in the decaying remains of cesspools and composts (house flies), in water (mosquitoes And midges) or lead a wandering lifestyle and hunt small insects.
Hymenoptera(Fig. 104, G). The order includes such well-known insects as bumblebees, wasps, bees, ants. Representatives of this order have two pairs of membranous wings, but some have no wings. This group also belongs to sawflies. They are called so because the females have a serrated ovipositor that resembles a saw. With this ovipositor, females cut leaves and stems of plants, and then lay eggs there. Sawfly larvae are similar to butterfly caterpillars. Hymenoptera include riders. Their females, using a long ovipositor, pierce the covers of the caterpillars and lay eggs in them. The larvae emerging from the eggs eat the caterpillars.
Incomplete transformation: egg -> larva -> adult insect (orders Dragonflies, Orthoptera, Homoptera, Bugs); complete transformation: egg -> larva ->doll -> adult insect (orders Lepidoptera, Coleoptera, Diptera, Hymenoptera).
Insects typically lay eggs in external environment, however, sometimes the larvae hatch from them while still in the abdomen of the female and are born “alive” from there. Insects are characterized by relatively large, yolk-rich eggs. Developing in the cavity of the ovariole under the pressure of its walls, the eggs are somewhat elongated in length, thus the insect eggs, which were round in the initial state, are replaced by elliptical ones. In butterflies and some bugs, the eggs become rounded for the second time. Insect eggs vary in shape and size. The largest of them reach 15 mm in length, and the smallest do not exceed 0.05 mm. Sizes vary from 1.35% to 70% of the female’s body length.
The development of an insect in the egg phase can last from several days (for many flies) to 2 - 3 weeks. In insects that lay eggs in autumn, the duration of the egg phase can reach 6 - 9 months.
The shell of insect eggs is called chorion; it consists of two layers penetrated by a system of air cavities. Occasionally, a layer of wax and an additional cuticle are deposited under the chorion. The eggs of many insects are well protected from moisture loss.
The photographs show insect eggs whose size varies from 0.7 to 2 mm in diameter. The photographs were taken using a scanning electron microscope, which uses beams of electrons to trace the surfaces of objects. Then the resulting black and white photographs were recolored to reflect the natural appearance of the eggs.
Dryas iulia butterfly egg
This Dryas iulia butterfly egg on a passionflower tendril may not be threatened by hungry ants. This species of butterfly lays eggs almost exclusively on this plant. (Martin Oeggerli)
Shield eggs
Shield bugs often lay their eggs in groups. The individual eggs are glued not only to each other, but also to the sheet on which they are left. The tiny growths act like a breathing apparatus. (Martin Oeggerli)
Caligo butterfly egg
The mosaic pattern on the Caligo butterfly egg looks like a space landing pad. In the center is a tiny hole called the micropyle, through which sperm enters the egg. (Martin Oeggerli)
Blue morpho butterfly egg
The red stripe indicates chemical reaction after fertilization. The egg contains the embryo of a butterfly - one of the largest. Its wingspan ranges from 12 to 20 centimeters. (Martin Oeggerli)
Egg of a beautiful blueberry butterfly
The beautiful blueberry is a very rare species of butterfly because it is fastidious. She lays eggs (as in the photo) only on the European perennial hippocrepis. Moreover, she looks for holes chewed by rabbits to make it easier to lay eggs. (Martin Oeggerli)
Egg of the Cetosia Byblis butterfly
This egg has a lacy pattern with micropyles through which the sperm enters. A similar design is found on the scaly wings, which give the red butterfly its name. (Martin Oeggerli)
Fathead egg
Fatheads lay eggs on the horned frog. Adults are found in Europe and parts of Asia. The butterfly is no different in beauty. (Martin Oeggerli)
Cabbage egg
A yellow cabbage egg under the lower leaves of a common cabbage (pictured) and Brussels sprouts. (Martin Oeggerli)
In the cockroach, as in representatives of some other groups of insects (mayflies, dragonflies, mantises, stoneflies, orthoptera, earwigs, lice, homoptera), development occurs with incomplete transformation. This means that larvae emerge from the eggs - small insects that look very similar to their parents. They differ from adult insects in their smaller size, lack of wings and underdeveloped reproductive system. The larvae molt several times, grow with each molt and become more and more like adult insects. Over time, they become sexually mature and their wings are fully formed. After this, the insects no longer grow.
Thus, an insect with incomplete metamorphosis goes through three stages in its development: egg >> larva >> adult insect (Fig. 100).
Rice. 100. Diagram of the development of an insect with incomplete transformation: 1 - egg capsule; 2,3,4 - different stages of larval development; 5 - adult insect
Dragonflies. These are well-known insects with a long slender body and two pairs of strong transparent wings (Fig. 101, 1). Dragonflies (especially large ones) are distinguished by very fast and maneuverable flight. They are predators, catching insects (flies, mosquitoes, small butterflies) on the fly. Dragonflies have large compound eyes that provide nearly all-round vision and long legs lined with coarse hairs. Dragonfly larvae are inactive and live in ponds, lakes, ditches with water, and slowly flowing rivers. They are also predators and grab passing crustaceans, larvae of other insects, tadpoles and fish fry with the help of a lower lip that can be thrown forward, which is called a mask.
Rice. 101. Representatives of insect orders with incomplete transformation: 1 - dragonfly; 2 - bug: 3 - grasshopper; 4 - praying mantis; 5 - stonefly; 6 - cicada
Orthoptera. This group includes locusts, grasshoppers (Fig. 101.3), crickets and mole crickets. They have two pairs of wings (the front ones are denser than the hind ones), many have jumping hind limbs, and a gnawing mouthparts. Many of the Orthoptera jump in heights of up to 80 cm, and if they help themselves with their wings, the distance they cover in one jump reaches 10 m. Some types of locusts fly well. Locusts feed on plants, among grasshoppers there are both herbivorous species and predators, and crickets are omnivores.
Homoptera. Homoptera include cicadas (Fig. 101, b) and aphids. Their mouthparts are of the piercing-sucking type, and their wings are usually folded into a roof (“house”). Homoptera feed on plant sap. Cicadas are large (up to 7 cm long) diurnal insects and are known for being able to make very loud sounds using special organs located below at the base of the abdomen. Aphids are small insects 0.5-6 mm long. Among them there are both winged and wingless forms. Many harm crop plants.
Bugs, or Hemiptera. Representatives of this group are called so because their fore wings (elytra) are dense in front and soft in back (Fig. 101, 2). The second pair of wings lies under the first. It is with the help of the second pair of wings that bedbugs can fly. Some, like bed bugs, lack wings. The mouthparts of bedbugs are piercing-sucking. Among bugs there are species that feed on plant juices, there are predators and bloodsuckers (bed bugs).
Insects with complete metamorphosis
In insects with complete metamorphosis, the larvae are completely different from the adults. These are the larvae of butterflies, beetles, flies, wasps, and ants. These larvae lack compound eyes, have only simple ocelli, or have no visual organs at all; the body is most often worm-shaped (butterfly caterpillars). Often there are no antennae and no wings. Insect larvae with complete metamorphosis molt several times and grow. Having reached its maximum size, the larva turns into a pupa - this is another stage of development, usually motionless, intermediate between the larva and the adult insect.
Thus, insects with complete metamorphosis go through four stages in their development: egg >> larva >> pupa >> adult insect (Fig. 102).
Rice. 102. Stages of development of an insect with complete transformation (chafer beetle): 1 - egg: 2 - larva; 3 - pupa; 4 - adult insect
In insects with complete metamorphosis, the larvae often live in completely different places and feed on different foods than adult animals. Thus, caterpillars (butterfly larvae) feed on green parts of plants and have gnawing mouthparts. Adult butterflies feed on the nectar of flowers, and their mouthparts are sucking. Midges suck the blood of mammals, and their larvae live in running water of rivers and catch small organic particles carried by the current. The difference in habitats and nutrition of adult insects and their larvae eliminates competition between different stages of the same species. Most species of insects are characterized by development with complete transformation.
Butterflies, or Lepidoptera. Butterflies (Fig. 103, A) are called lepidoptera because they have small chitinous scales on their wings. They are brightly colored and strongly refract the incident light, creating a bizarre play of colors.
Rice. 103. Representatives of insect orders with complete transformation: A - butterflies: 1 - burdock; 2 - hawk moth; 3 - she-bear; B - beetles: 4 - swimming beetle; 5 - barbel; 6 - Khrushchev; B - dipterans: 7 - housefly; 8 - green carrion fly; 9 - blood-sucking mosquito; 10 - long-legged; G - hymenoptera: 11 - wasp; 12 - sawfly; 13 - rider
The coloring of the wings of butterflies helps them recognize each other, camouflages them in the grass and on the bark of trees, or warns enemies that the butterfly is inedible. Butterflies are so diverse and beautiful that it is a pleasure to look at them in museums and in special color atlases.
The sucking mouthparts of butterflies are a proboscis coiled into a spiral. Butterflies feed on the nectar of flowers. When pupating, the caterpillars of some butterflies secrete silk threads. People breed mulberry and oak silkworms to produce silk fabrics.
Beetles, or Coleoptera(Fig. 103, B). Representatives of this group have dense, hard elytra covering the second pair of leathery wings, with which they fly. The mouthparts are gnawing. Among the beetles there are many herbivores, there are predators and carrion eaters. Beetles live in the ground-air environment (on plants, the surface of the earth, in the soil) and in water. Beetle larvae are both very mobile predators, living openly, and sedentary, worm-like, living in shelters and feeding on plants, fungi, and sometimes decomposing remains of organisms.
Diptera(Fig. 103, B). These insects have only one pair of wings. The second pair is greatly reduced and serves to stabilize the flight. This group includes mosquitoes and flies. They have piercing-sucking or licking mouthparts. Some dipterans feed on pollen and nectar of flowers (syrphid flies), there are predators (quackers) and bloodsuckers (mosquitoes, midges, midges, horseflies). Their larvae live in the decaying remains of cesspools, composts (house flies), in water (mosquitoes and midges) or lead a wandering lifestyle and prey on small insects.
Hymenoptera(Fig. 103, D). The group includes such well-known insects as bumblebees, wasps, bees, and ants. They have two pairs of membranous wings (some have no wings).
Sawflies also belong to this group. They are called so because the females have a serrated ovipositor that resembles a saw. With this ovipositor, females cut leaves and plant stems and lay eggs there. Sawfly larvae are similar to butterfly caterpillars.
Hymenoptera also include riders. Their females, using a long ovipositor, pierce the covers of the caterpillars and lay eggs in them. The larvae emerging from the eggs eat the caterpillars. The parasites are used in the biological control of pests of cultivated plants.
Among insects, there are groups that develop with incomplete transformation (the larva emerging from the egg looks like an adult insect) and with complete transformation (the worm-like larva turns into a pupa, from which an adult insect emerges).
Dragonflies, Orthoptera, Homoptera, bugs (hemiptera), butterflies (Lepidoptera), beetles (Coleoptera), Diptera, Hymenoptera; incomplete and complete transformation, caterpillar.
Exercises based on the material covered
- Name the insects known to you that have incomplete metamorphosis. What role do they play in nature?
- Name the insects known to you with complete metamorphosis. What role do they play in nature?
- Tell us how insects with incomplete metamorphosis develop (using the example of a cockroach or a bug); with complete transformation (using the example of the Colorado potato or May beetle).
- List the characteristics of the main groups of insects.
include: dog, fox, cow, elephant and other mammals. IN REALITY The term “kingdom” is used in biology. In addition to the animal kingdom, in the world of living nature it is customary to distinguish the kingdoms of plants, fungi and some others that are not so widely known and popular. Thus, the concept of “animals” includes mammals, birds, fish, amphibians, reptiles, as well as invertebrates - for example, mollusks, worms, insects. Tell your child that a dog, a cow, an elephant are animals, and you won’t be wrong. Of course, the word “animals” is also acceptable in this case. And do not hesitate to classify birds, butterflies, fish and other creatures as animals, because they are not considered plants! In this case, excessive pedantry will only harm the matter. Myth 2 Hedgehog eats mushrooms and apples IN REALITY The main food of a hedgehog is beetles and caterpillars, somewhat less often - mice, snakes and frogs. This cute and harmless creature at first glance is a ruthless predator. It can be started in country house if there are mice there. There will be no mercy for them! A hedgehog can eat eggs or even chicks. And the erroneous opinion about the harmless herbivory of hedgehogs arose because people noticed hedgehogs that, quite by accident, pricked various edible objects onto their spines. Usually these are mushrooms in the forest, and apples in the garden. This is where such pictures come from in children's books. Of course, such a sight is quite aesthetic and, moreover, makes you believe that the clever hedgehog is stocking up on food. Telling your child about what a hedgehog actually eats is not difficult. It is much more difficult to explain that most books contain erroneous information. We usually tell children in class that the picture in his book shows a fairy-tale hedgehog and he has every right to indulge in an apple. But in nature everything is completely different. Myth 3 Bananas grow on a palm tree REALITY Banana is a giant perennial herb. After flowering and fruiting, the entire above-ground part dies, which never happens in a tree (in particular, a palm tree). Palms are tree-like plants. The most widely known are the coconut and date palms, but the banana palm does not exist in nature. Myth 4 The dolphin, as well as the whale, is big fish IN REALITY Everyone knows that fish lay eggs, from which fry then emerge. The exception is some viviparous fish- for example, guppies. Dolphins and whales belong to the class of mammals. They give birth to young and feed them with milk. Dolphins are excellent at navigating in water using echolocation and very sensitive hearing. Their sound organ is located in a single nostril. They have a very highly developed central nervous system and the brain. Myth 5 Polar bear hunts penguins IN REALITY The fact is that the above representatives of the animal world live at opposite poles globe: polar bears are in the North, and penguins are in the South, and they can’t possibly meet, except perhaps in a zoo. Well, to be completely precise, the Magellanic penguin lives not only in Antarctica, but also in temperate waters South America on the Atlantic side and on the Falkland Islands (Malvinas). But even there he never had the opportunity to meet Umka or his brothers. Myth 6 Frogs and toads eat strawberries in the garden IN REALITY Strawberries in the garden are most often spoiled by slugs. Toads and frogs, on the contrary, save the harvest by eating pests - slugs and beetles. Sometimes shameless raids on delicious berries Strawberries and more are visited by birds. Knowledgeable people they say that this happens in the hot summer. But perhaps this is also a myth? Myth 7 Spiders are insects IN REALITY Features An insect is as follows: it has 6 legs and goes through the following stages of development - egg-larva-pupa-adult. Now take a closer look at the spider. Firstly, it has 8 legs, and secondly, it only goes through two stages of development: the spider egg. Spiders, ticks and scorpions are not insects. They belong to the class of arachnids. Certainly, small child You should not load it with complex scientific terms, but it is necessary to provide information at its level. He will be happy to examine the structure of an insect and a spider, find the differences between them and will be quite capable of saying, for example: “Insects and spiders are drawn in this picture.” Which would be absolutely right! "My Child" magazine, November 2007 Didn't find the answer to your question? Ask an expert. Online consultations.
1) the name of the theory that stated that living things can arise from non-living things2) The theory according to which the air contains “ life force", capable of causing spontaneous generation of life
3) The theory according to which in modern conditions spontaneous generation of life is impossible
4) which scientist proved the impossibility of spontaneous generation of life in a pasteurized broth enclosed in a sealed flask.
5) refuted the theory of spontaneous generation of life
6) author modern theory about the origin of life
7) a scientist who simulated in a flask the conditions that existed on Earth 4.6 billion years ago
8) Who was the first to obtain proteins abiogenically from individual amino acids?
9) The origin of life took place in... stages
10) Type of nutrition of the first true cells
11) Perhaps life on Earth began many times as it ended
12) Clots of organic substances appeared at what stage
13) Clots of organic matter floating in the primary broth
14) abiogenic synthesis of organic substances corresponds to what stage of life development?
15) The first true prokaryotic cells appeared at the stage?
16) coacervates exhibiting some properties of living things
17) Eukaryotic cells appeared
18) Photosynthesis first appeared in a group of organisms
19) Metabolism and the ability to grow and reproduce appeared at what stage?
20) due to the absence of these organisms, organic substances in the “primary broth” could exist indefinitely
21) Absence of this gas in the atmosphere ancient earth ensured the preservation of organic substances in the “primary broth” indefinitely
22) Prokaryotes are colonial, but sometimes?
23) The theory according to which eukaryotes arose due to the absorption of some prokaryotes by others and their mutually beneficial cohabitation.
Reproduction of insects. Reproduction is a complex process that ensures an increase in the number of organisms. In insects, like many other plant and animal organisms, the reproductive period begins after a long period of nutrition, growth and development. During the period of feeding, growth and development, many insects die, so there is a biological need to make up for this loss. If the intensity of reproduction does not compensate for mortality, then the species becomes extinct. Thus, in a typical case, the life cycle of an insect consists of a period of feeding, growth and development, which is followed by a period of reproduction and dispersal. Dispersal is an important stage in the life of adult insects, which strive to be evenly distributed over all areas and areas where they have food sources and other conditions necessary for survival.
It is important first of all to pay attention to the prerequisites that most species have for rapid reproduction. If we determine the potential fertility of the well-known housefly, taking into account the fact that in individual clutches there are about 100 eggs, and there can be up to 5 such clutches from each female over the summer, then as a result, during the season one female will theoretically give birth to offspring exceeding hundreds of billions of copies.
Among insects, there are few economically important pests that cause serious damage to agriculture and forestry.
Thus, the harmfulness of insects attacking agricultural crops, orchards, vegetable gardens, and forest plantings is closely related to their numbers. Insects cause damage periodically, when the number of a particular pest increases greatly and its period begins. mass reproduction. The same species does not cause economically significant harm during periods of low abundance.
IN Lately Much attention is paid to issues of nature conservation, including insects. Everyone knows that a huge number of insects feed on plants, eating their leaves. Previously, many of these insects were included in the list of pests to be destroyed. Modern approaches to problems of nature conservation give reason to reconsider this issue and include among pests only mass species insects that severely damage plants and thereby cause significant economic damage.
Egg. Insect reproduction ends with the laying of a female large number eggs, each of which, under favorable conditions, turns into a larva and then into an adult insect.
Some insects do not lay eggs, but small larvae that hatch from eggs in the genitals inside the female's body. This viviparity is an adaptation to reduce offspring mortality, since many eggs die due to unfavorable conditions or eaten by predators. In a typical case, the female insect lays eggs, which, if they do not overwinter, take several days to develop.
Larva. The feeding, growing and developing phase of the insect's life cycle is called the larva. All insects, without exception, have larvae. The larvae emerge from the eggs extremely small. They feed continuously and voraciously and usually increase in size quickly.
However, as mentioned above, the body of insects, including larvae, is covered on the outside with a durable chitinous cover. Unlike adult insects, the body covers of larvae are softer, capable of stretching, otherwise their growth would be impossible. Nevertheless, the ability of the integument to stretch is not unlimited, and after a certain period of feeding and growth of the larva, the integument becomes an obstacle to a further increase in its size.
A crucial period begins - molting. During preparation for molting, the larvae stop feeding, become inactive, and new covers appear under their covers, much more spacious. After the larva's body has prepared for molting, the old integument bursts in the area of the head and gradually slides to the rear end of the body as a result of muscle contraction. The larva is completely freed from the old integument, its new integument hardens and becomes colored. She is back to vigorous eating and growth.
There are 3-6 such molts during the period of larval growth, but there can be significantly more. Preparing for molts - difficult physiological process regulated by special hormones.
Nutrition, as already emphasized above, is the main purpose of the larva in the life cycle of an insect. The larva accumulates reserve substances in the form of a reserve of proteins, fats and carbohydrates. Adult insects often do not feed at all and have underdeveloped mouthparts. In females of such insects, the development of eggs is carried out due to the reserves accumulated by the larva. The appearance of the larvae is extremely varied and depends on adaptation to the environment in which they live.
Complete and incomplete transformation. Doll. In the simplest case, adult insects and their larvae live in the same conditions. Good quality famous examples we can mention locusts and grasshoppers living among herbaceous vegetation, or cockroaches living in plant debris, in various crevices, etc. With this lifestyle, the larvae have the same adaptations as adult insects. For this reason, a larva emerges from the egg, outwardly similar to the parents, but much smaller in size, not yet capable of reproduction and without wings.
Gradually, during the process of feeding and growth from molt to molt, the size of the larvae increases, they develop wing rudiments, and reproductive organs develop (Fig. 10). The larva becomes more and more like an adult insect. Finally, the last molt occurs and an insect hatches from the skin of the larva, capable of flying (spreading) and reproducing.
Otherwise, the transformation of the larva into an adult occurs in cases where different phases of the insect’s life cycle live in different conditions, i.e. they have various devices. Thus, the larva of the May beetle or a closely related species, the beetle beetle, develops in the soil, feeding on plant roots, while the adult beetle lives openly on plants. In these cases, the larva and adult insect are completely different from each other (Fig. 11).
The larva of the cockchafer has a thick, dirty-white body, bent in a semicircle, and a large brown head equipped with sharp mandibles adapted for gnawing roots. She does not have compound eyes or any rudiments of wings; Its legs and antennae are short and bear no resemblance to the legs and antennae of an adult beetle.
With such a sharp difference between larvae and adult insects, a whole period of restructuring of external and internal organs larvae into the corresponding organs of the adult insect. Due to the need for this restructuring, the pupal phase occurs in the life cycle of insects.
The pupa is the resting phase of the life cycle. The pupa does not feed, does not grow, does not move, and is usually only able to weakly move its abdomen. The pupa is formed from the larva before the last molt, is freed from the larval skin and is characterized by a completely different structure than the larva; in appearance pupae, the signs of an adult insect are already clearly visible - legs, antennae, wing covers, etc.
The pupa is completely defenseless, so the larvae of many insects, before turning into a pupa, build special shelters in which it is protected from enemies. Thus, the caterpillars of some butterflies weave a special cocoon, many soil beetles pupate in caves with dense walls, etc.
Over the course of several weeks, complex changes occur in the body of the pupa, some organs disintegrate, others undergo partial restructuring, including the nervous system. Finally, the skin of the pupa most often bursts along the longitudinal dorsal seam and gradually the legs, antennae, and wings are pulled out of the corresponding pupal covers. Shedding often lasts several hours.
The wings of the insect emerging from the pupa are soft, often wrinkled, and colorless. The insect itself also has soft covers, is not able to move quickly and is completely defenseless. The wings expand as a result of the rush of blood and then harden and become colored. In the first hours after molting, the integument on the entire body of the insect also hardens and becomes colored. After this, beetles, flies and other insects emerging from the pupa acquire the ability to fly, feed, and reproduce.
The above materials characterize two main types of insect development.
Development with complete transformation goes through 4 phases: egg, larva, pupa, adult insect (Fig. 11).
During development with incomplete transformation, there is no pupal phase in the life cycle, but there are only 3 phases: egg, larva and adult insect (Fig. 10). Hence the name of the transformation - “incomplete”.
However, these two types of transformation do not exhaust the entire diversity of insect life cycles. For example, the question of what transformation was the original one in insects requires clarification. The answer to this question is complex. This type of transformation is characteristic only of those insects that initially did not have wings, i.e., their most ancient groups - the bristletails. This primitive transformation is characterized by gradual changes appearance insect, and molting continues in insects that have begun to reproduce. This type of transformation is called primary transformation (protometaboly). Although complete (holometaboly) and incomplete (hemimetaboly) transformations, as already noted, are the main types of transformation in insects, in addition to them and primary transformation, there are other types of metamorphosis. A special type is considered, for example, to be the transformation of insects of ancient aquatic groups - dragonflies and mayflies. Their larva bears little resemblance to an adult insect, but there is no pupal phase.
Based on complete transformation, as a result of its further complication, the so-called excessive transformation (hypermetamorphosis) arose in some beetles and flies. Thus, in the red-headed spanka from the family of blister beetles, the larvae different ages outwardly they differ sharply (Fig. 12). The first instar larva is very mobile, it actively searches for a clutch of locust eggs (pod) in the soil, penetrates it, molts and turns into a thick, sedentary larva, which is busy only with feeding. Thus, the differences between larvae of different ages are explained by the fact that they lead a different lifestyle.
It should be borne in mind, however, that not all insects with complete metamorphosis have larvae and adult insects currently living in sharply different conditions. Butterflies and their caterpillars, leaf beetles and their larvae live on plants, i.e. in similar conditions. Such exceptions are explained by the fact that some beetles and most butterflies switched to a similar way of life later, after the development of complete transformation had occurred in their ancestors. In this regard, it is interesting to note that the most ancient groups of beetles and butterflies have larvae that develop not on plants, but secretly, in the depths of various substrates.
The biological essence of the transformation of insects is largely similar to what is observed in other groups of animals. IN initial period During development, an insect must eat and grow quickly. This task is performed by the larvae. Adult insects often do not feed at all. They have other functions - reproduction of the species and its resettlement in new favorable habitats.
Biology of the cockchafer. The cockchafer (Table 1, 4) is included in large group harmful insects from the family of lamellar beetles, the larvae of which gnaw the roots of plants.
IN western regions USSR under the name "Chafer" actually combines two different, but very similar in appearance: the Western Chafer and the Eastern Chafer. Only the latter species is found in Siberia.
The cockchafer overwinters in the soil and emerges when the buds open on the birch tree and the first spring leaves appear. During the day, beetles hide in the crowns of trees, and at dusk, after sunset, they begin to fly. They are only attracted to crowns deciduous trees(birch, maple, oak, aspen, etc.), near spruce or pine trees they appear rarely and mostly by accident. This behavior is explained by the fact that the beetles feed mainly on leaves, and very rarely on larch needles or pine inflorescences. If there are a lot of beetles, then all the young spring leaves are eaten.
The cockchafer develops in the soil. A mature female burrows into the soil to a depth of 20 - 30 cm and lays up to 70 oblong eggs there. Females choose sites for laying eggs very carefully. The beetles do not fly into the thicket of the forest, but gather on the edges and fields adjacent to the forest.
This behavior of females leads to the fact that they concentrate in certain places with favorable conditions, where their numbers can be very high. They are especially attracted to pine nurseries and young plantings that are well-warmed by the sun.
The larvae develop slowly and middle lane USSR winter 3 times, i.e. the life cycle of the cockchafer is completed in 4 years. Large beetle larvae that gnaw the roots of young pine plantings are especially harmful. The eating of pine roots can be so significant that such a tree can be easily pulled out of the ground. There are known cases of the destruction of pine plantings by the larvae of the cockchafer in areas measuring thousands of hectares. Thus, the harmfulness of the cockchafer is explained by the fact that females concentrate in certain areas of the forest and field, where they lay many eggs at once. As a result, the number of cockchafer larvae during breeding periods in these areas becomes alarming and they damage the root systems of forest crops, preventing forest regeneration.
Rare and endangered species(Table 3). As already noted, the vast majority of insects do not have economic significance, their life activity is indifferent to the human economy. However, it does not follow from this that a person can be indifferent to such insects that are neutral to him. Firstly, many of these insects decorate nature and have a large aesthetic value for people who treat nature with love and care, and there are more and more such people nowadays. In addition, these billions of insects, harmless to humans, are absolutely necessary for the normal existence of huge and rich natural natural complexes. Suffice it to say that many invertebrate and vertebrate animals feed on insects, which in the absence of this food source are doomed to starvation, and many to death. Therefore, great concern thinking people causes depletion of natural complexes, the disappearance of a number of plants and animals, including insects.
In most cases, these adverse events are associated with production activities humanity. The area of cities is growing, they are being developed large areas for agricultural production, where mineral resources are discovered, industrial complexes arise, etc.
A huge number of insects die when pesticides are used to protect agricultural and forest lands from any strongly multiplied pest: after all, pesticides kill not only this pest, but also other species, including beneficial ones.
Many insects that were relatively common just a few decades ago are now rare and need protection. These are mainly large beetles and butterflies, which have become rare due to the reduction in the area of natural habitats where these species lived and the reduction in food sources available to them.
The stag beetle (Table 3, 2), for example, becomes rare species due to the reduction of those suitable for his life forest areas in the southern regions of the country. This beetle can only exist in old forests with an abundance of large rotting trees, in the wood of which its larvae develop.
The great oak woodcutter (Table 3, 3) was previously considered a pest of oak forests. Its larvae lived in large hundred-year-old oak trees and damaged their wood. There are almost no such oaks left now. In some countries, areas with old oak trees are protected in order to also preserve the great oak woodcutter.
The largest woodcutter of the USSR fauna is the Ussuri longhorned beetle, reaching a length of 10 cm and found on Far East, is also experiencing oppression due to the cutting down of old forests. This species, like the stag beetle, develops in the rotting wood of century-old oaks, elms and other deciduous trees.
Many large insects - butterflies, dragonflies, orthoptera, etc. - have become rare and need protection. In the USSR and many other countries, the so-called “Red Books” have been published and are being prepared for publication, which describe species of animals whose extermination is punishable by law.
There are few insects protected by law, but every amateur entomologist should understand that catching insects for one's own pleasure can harm nature. It is much more useful to direct your efforts and knowledge to the protection of insects in general, especially rare and endangered species