Insects with complete metamorphosis

Order Hymenoptera

Bee

Bumblebee

Hornet

Wasp

Ant

Phase variability[edit | edit code]

Phase variability of the desert locust
A special form of metamorphosis, which goes through together with the main one, is the so-called phase variability

, discovered initially in locusts, but then found in other orthoptera, as well as in stick insects, butterflies and other insects.
Its essence lies in the fact that when crowding of individuals occurs, the morphological and biological-physiological properties of the species change - the pigmentation of the integument increases (mainly due to the partial deposition of metabolic products in them), the proportions and shape of body parts change, development accelerates, and behavior changes. A gregarious phase
(lat. phasis gregaria)
arises When individuals disperse, these properties are lost and the species returns through a transition phase
(Latin phasis transiens) to its original state -
a single phase
(Latin phasis solitaria). The differences between the phases are so great that ignorance of their nature gave rise to the division of one type into 2-3.

Order Diptera

Fly

Mosquito

Horsefly

hoverfly

Age-related color change

Hatching from the pupa and thereby undergoing the last molt in the larval stage, the insect leaves its shell. Often the initial color is light in tone (not white, but paler). Over a certain period (from several hours to 2-3 weeks), pigment substances accumulate and oxidize when in contact with atmospheric air, as a result of which the cuticle darkens.

Certain species, for example, the imago of butterflies (order Lepidoptera) appear with “their own” formed color.

The change in color may be associated with certain changes in the body. Thus, the desert locust is initially yellow-green in color. During the breeding season, reproductive enzymes accumulate in the body and as a result, the integument acquires a pink tint (pictured above).

Stages of complete transformation of insects

Various metamorphoses are characteristic of all types of insects. Complete metamorphosis involves a complete change in the appearance of the insect. During the period of changing phases of complete transformation, all insects experience several stages of molting. Such changes are characteristic of beetles, lepidoptera, and flies. The usual complete transformation looks like this: moulting, insects shed their old cuticle and begin to increase in size. Such periods have different time intervals. For example, butterfly larvae go through 5-6 molts, which indicate their age.

Main stages of transformation:

Egg
. This phase is characterized by the presence of the embryo inside the hard shell of the egg. At this stage, it replenishes its nutrients and prepares to move on to the next stage. The end of this period is the emergence of the larva from its egg.
Larva.
Unlike the embryo, the larva begins to move and gains the ability to feed on its own. As a rule, the appearance of the larva is very different from the other stages. This is due to the underdevelopment of many of its organs. The main task of this stage comes down to nutrition in order to increase its size. Some insects are characterized by cannibalism among young individuals. After the egg stage, the larvae can feed on each other in the absence of other organisms;
Doll.
At this stage, the insects do not move and are in a pupal shell. The insect body undergoes major changes in the anatomy of the body structure, and upon completion, the insects become adults. If you try to open the larva at the first stage of the pupa, it will be difficult to notice any development in it. The pupa will consist of a thick white liquid, and only the vascular and nervous systems will be visible. This liquid serves to build a complete organism.
Imago.
A fully formed insect organism. It has all the necessary organs inherent to a particular species.

Reproduction

Full Development: Stag Beetle

Reproduction in most insects is accompanied by mating and fertilization and is associated with the participation of two sexes. However, insects also have other methods of reproduction:

viviparity - the eggs mature in the female’s body, and the larvae immediately emerge (for example, in Madagascar and a number of other cockroaches). To the observer, it looks as if the insect is “giving birth,” but this process is completely different from gestation in humans and higher mammals.
parthenogenesis - reproduction without the participation of a male, when the female lays unfertilized eggs, and larvae emerge from them. It is very common among stick insects, but is also found in many other groups - in cockroaches, mantises, and all social insects (in bees, wasps, ants, and bumblebees, working individuals appear precisely from unfertilized eggs).
pedogenesis is a special case of parthenogenesis, the ability to reproduce at the larval stage. Found in fanwings, micromalthus beetles, gall midges and bagworms.
polyembryony - the development of several embryos from one zygote. Interestingly, in addition to insects, it is also observed in armadillos and bryozoans.

The difference between complete and incomplete transformation

During the period of incomplete metamorphosis, insects go through three stages, which are similar to the metamorphoses of complete metamorphosis, with the exception of the “pupa” stage. With incomplete transformation, the differences between the stages are not so pronounced. The larva looks like a small adult. However, despite the small number of stages of transformation, insects with incomplete metamorphosis are as complete as insects with complete metamorphosis. The presence of certain phases is explained by the living conditions of insects. Orders of insects with incomplete transformation include: Homoptera, bedbugs, dragonflies, lice, Orthoptera, and cockroaches.

IMAGO

What does the word IMAGO

in dictionaries:

Anagram for the word “amigo”
Question: In biology: the final stage of insect development - answer: IMAGO
Adult stage of insect
Insect maturity
Mature insect
Grown insect
Mature insect
What word can be made from the word “amigo” by rearranging the letters?
What word will you get if you mix the letters in the word “amigo”
A jumble of letters from the word “amigo”
Insect. with a matriculation certificate
An insect “in its prime”
Insect “of marriageable age”
Insect in adulthood
Insect in the last stage of development
Insect with maturity certificate
The final stage of individual development of insects
Winged stage of insect development
Change the letters in the word “amigo”
The last, fourth stage of butterfly development
Novel by the Swiss writer K. Spitteler
Adult insect
A fully grown insect
Ripe insect
Stage of love and weddings in insects
Insect development stage
Insect development phase
The final stage of insect development
What comes out of the word “amigo” if the letters in it are reversed?
adult insect

In biology, maintaining the proportions of organs and body parts during the period of growth of the organism

In biology - invagination

Features of the development of insects with complete transformation

The cardinal difference between the larvae and the last stage is noteworthy. The larvae are completely different in territory and nutrition from the adults. For example, the larvae of flies and beetles live in the soil. In addition, the larvae of full transformation have a gnawing mouthparts, lack eyes and wing rudiments, and the antennae and legs are very short. The degree of development of the limbs depends on the type of insect and is divided into 4 groups:

Legless larvae. Characteristic of dipterans and beetles;
Larvae with small limb rudiments. These include bees and wasps;
Larvae with well-developed limbs. This type is demonstrated by individuals of winged insects, such as beetles and lacewings;
Caterpillar. This stage has well-developed three pairs of walking legs and several pairs of prolegs. These include representatives of butterflies and sawflies.

The characteristics of the stages of development of a particular phase may differ depending on the species in question.

Structure and shape of eggs

Insect eggs are rich in yolk and covered with two membranes. They are varied in size, shape and color. Egg sizes usually range from tenths of a millimeter to several millimeters. The shape of the eggs is oval (many beetles, butterflies, flies), elongated (grasshoppers and locusts), spherical (turtle bugs), hemispherical (cutworm butterflies), barrel-shaped (scuttle bugs), bottle-shaped (day butterflies), stalk-shaped ( lacewings) ( Fig. 2

Rice.
2. Forms of insect eggs Females of various insects lay eggs in places suitable for further development of larvae. The fertility of insects (the number of eggs laid by a female during her life) is varied. In some species it is small - on the order of several dozen eggs, in most about several hundred, in a number of species - several thousand. The fertility of sexually mature female social insects reaches several million eggs. In some insects, females lay eggs singly or scattered, but most lay them in compact groups - ovipositions.

What is a pupa

This is the phase of the insect life cycle that leads to the development of a sexually mature individual - the adult. The pupal stage is characterized by the fact that the organism does not feed and cannot move. In addition to silk, animals often use particles of sand or shells to build a cocoon and strengthen it. In free pupae, the antennae, legs and wings of the future imago individual are free and pressed to the body. Covered pupae are characteristic of many species of butterflies, ladybugs, and some dipterans.

Class insects

Body coverings, musculoskeletal system

The body is differentiated into a head (5 fused segments), thorax (3 segments) and abdomen (8 segments). On the head there is one pair of antennae - antennas, which are the organs of smell and touch. The body cavity of insects is mixed (mixocoel), which allows during molting to significantly increase body volume by increasing blood pressure.

Many insects are capable of amazing movement in the air - flight. The first pair of wings is called elytra: they do not participate in flight, they are dense chitinized formations covering part of the chest and abdomen. The second pair of wings is directly involved in flight and has the appearance of flattened membranous formations.

Three pairs of walking legs are attached to the chest. The jointed limb of the insect ends in two claws, between which suckers are sometimes located. The limbs of insects differ in the function they perform, receiving their names according to it: digging, running, jumping, swimming, collecting.

The body of insects, like all arthropods, is covered with a chitinous cuticle - an external skeleton. This dense shell of the insect inhibits growth. Remember that insects actively grow only in the larval stage and during the molting period, when the chitinous cover is not fully formed or has been shed.

Digestive system

Consists of anterior, middle and posterior sections. The anterior section includes the mouth, pharynx, esophagus, which often has an extension - goiter, stomach. After the stomach, the middle section begins - the intestine, from which numerous blind-ending outgrowths extend, increasing the absorption surface. In the hind intestine, excrement is formed and water is absorbed; the hind intestine ends at the anus.

It is especially necessary to note the developed muscles of the stomach, which is called muscular. Additional grinding of food occurs in it. After this, food particles are broken down into monomers, which are absorbed by the intestine and enter the hemolymph. With its current, nutrients reach internal organs and tissues.

Most insects have salivary glands. Insects have a wide variety of complex mouthparts. The structure of the oral apparatus reflects the method of feeding. Below you see a table showing the variety of mouthparts in insects.

Respiratory system

The respiratory system is represented by a highly branched system of tracheas, which perform the function of external breathing. On the head, chest and abdomen of insects there are spiracles (stigmas) - breathing holes through which the trachea opens to the external environment.

The circulatory system does not carry oxygen, so the function of its delivery belongs entirely to the tracheae, which branch into thin tubes (tracheoles) and approach small groups of cells. In some fast-flying insects (flies, bees), the trachea forms expanded areas - air sacs, which improve ventilation of the tracheal system and reduce the specific weight of the body

Circulatory system

Insects are characterized by an open (lacunar) type of circulatory system. Blood moves freely through the lacunae (sinuses), directly washing the internal organs and tissues. The function of the heart is performed by the spinal vessel: thanks to its contractions, blood is pumped from the back of the body to the front.

The functioning of the heart vessel is similar to that of crustaceans. At the moment of relaxation of the heart vessel, blood fills it through the openings (ostia), and at the moment of contraction (systole), blood is pushed into the arteries, then enters the body cavity, washing the organs and tissues.

The internal environment of insects is hemolymph, which is a colorless or yellowish liquid. Nutrients are absorbed into the hemolymph from the intestine and then delivered to the cells of the body. It also removes metabolic by-products.

Excretory system

The excretory organs are represented by Malpighian vessels (in honor of the Italian biologist and physician Marcello Malpighi). These are long tubular projections of insects and arachnids that are located at the border of the midgut and hindgut.

As you remember, insects are faced with a difficult task: to preserve water in the body as much as possible. The Malpighian vessels contribute to this: they receive metabolic products from the hemolymph in the form of a suspension. As it moves through the Malpighian vessels, all the water from the suspension is absorbed back into the hemolymph, and metabolic products (uric acid crystals) enter the intestine in dry form and are excreted from the body with excrement.

The excretory organs also include the fat body. The fat body is a formation of mesodermal origin containing reserves of nutrients that are constantly consumed by the body. Metabolic products can also accumulate in the fat body: breakdown products, which neutralizes their toxic effect.

Nervous system

The type of nervous system of insects is nodal. It consists of the brain (suprapharyngeal ganglion), subpharyngeal ganglion and ventral nerve cord.

The brain has a complex structure, formed as a result of the fusion of 3 ganglia and consists of 3 sections: anterior, middle and posterior. Nerve cords, called connectives, extend from the brain and go to the subpharyngeal ganglion, collectively forming the peripharyngeal nerve ring.

The most developed ganglia in the ventral nerve cord are in the chest, as they innervate the complex functioning of the limbs and wings. The nodes are distributed unevenly: 3 ganglia are located in the chest, 8 in the abdomen.

The sense organs are well developed. The eyes are simple or complex (faceted), one pair of antennae (antennae), on which the organs of smell and touch are located. There are taste organs located on the palps of the lower lip and lower jaw.

This progressive development of the nervous system laid the foundation for the emergence of the most complex and amazing reflexes in insects. Among all invertebrates, only insects are distinguished by a social way of life: they build a nest together, care for offspring, and share responsibilities among family members. Social insects are bees, wasps, ants, and bumblebees.

Note that in the anterior part of the brain there are mushroom bodies, associative centers of the brain. Mushroom bodies are especially well developed in insects that lead a social lifestyle, which is associated with their complex behavior.

Reproductive system

Insects are dioecious; hermaphrodites are very rare among them. Well-defined sexual dimorphism—external differences between males and females—is often encountered.

The gonads are paired: in males there are testes, in females there are ovaries. From the testes and ovaries, respectively, the vas deferens and oviducts depart, flowing into the ejaculatory canal and vagina. Fertilization in insects is internal: with the help of copulatory organs, the seed is introduced by the male into the reproductive tract of the female.

Development can be direct or indirect. Remember that all insects have indirect development.

Indirect development can occur with metamorphosis (from the Greek metamorphosis - transformation) - complete transformation, or without it - incomplete transformation.

Metamorphosis is a profound transformation of the structure of an organism, a transition from one form to another, accompanied by the appearance of new structural elements and functions.

As can be seen from the diagram above, incomplete and complete transformation are distinguished by the presence of a pupal stage, this is precisely the stage at which metamorphosis occurs. You will learn about which insects are characterized by development with metamorphosis and which are not in the next article.

A classic example of metamorphosis is the transformation of a caterpillar into a butterfly. In the cocoon (pupa stage) in the caterpillar's body, almost all tissues dissolve, with the exception of the nervous and circulatory systems. As a result of this metamorphosis, a new organism is formed - a butterfly, very different from a caterpillar.

It is logical to assume that in insects with incomplete metamorphosis, the larva resembles the adult individual, but is smaller in size. In insects with complete transformation, which is accompanied by metamorphosis (the caterpillar becomes a butterfly), the larva is completely different from the adult individual and is strikingly different from it in structure and functions.

Of particular note is parthenogenesis. Parthenogenesis (from the Greek parthenos - maiden, virgin and genesis - birth) is one of the forms of sexual reproduction in which a new organism develops from an egg without its fertilization. Since the male gamete is not involved in this process, the genotype of the offspring contains exclusively the genes of the mother.

Parthenogenesis occurs in the following insects: aphids, ants, bees, wasps, bumblebees, silkworms. Parthenogenesis refers specifically to the sexual (and not asexual) type of reproduction, since a new organism develops from an unfertilized egg (female gamete). This process plays an important role: it significantly increases the rate of population growth, regulates the ratio of female and male individuals, and ensures the continued existence of the species.

Artificial parthenogenesis in the silkworm was first obtained by A.A. Tikhomirov in 1886, and the practice was developed by B.L. Astaurov, who came up with an artificial method for producing male silkworms, which give an increased yield of valuable material - high-quality silk fiber.

Colorado potato beetle: photo

To make sure that you have the Colorado potato beetle, look at the photo of the pest and compare it with the individuals found in your garden. You may need a detailed description of the key external characteristics of the pest if you suddenly have doubts after a visual comparison.

The body of the beetle is round and voluminous; it can reach 1–1.2 centimeters in length and about 3–4 millimeters in width.
The main color varies from yellow to light brown and reddish.
There are 10 black stripes stretching across the back, as if carelessly drawn with a marker.
The large head may be brighter than the body, covered with black spots of arbitrary shape.
The beetles have 6 black legs.
There are long mustaches on the head.
The surface of the body is glossy, as if covered with varnish.
The insect has wings and can fly.

The Colorado potato beetle can be confused with the False potato beetle, which does not pose a danger to the vegetable garden. Adults are almost identical in appearance, but the potato beetle has red legs instead of black and slightly different stripes on the back - alternating white, black and brown. The Colorado potato beetle does not have white stripes.