Insects, examples and characteristics of which we will present today, are the largest group of all creatures that inhabit our planet. It includes about 80% of the total number of animal species. More than 1,000,000 species include such a group as insects. Examples known to science are far from all species that exist in nature. There may be more to discover. Many fossil and living primitive forms have been described, clarifying the evolution of modern 29 orders into which insects are divided. Examples of modern species will be discussed in this article. Most of the fossil forms belong to the Lower Carboniferous (345 million years ago). At this time, the vast wetland forests were already inhabited by winged insects.
Ubiquitous animals
Even in the sea there are insects. Examples of such species, however, are few. Some of them stay on the surface, others live in the littoral, and one species even lives on the seabed. But wherever any other animals penetrate, insects are sure to appear there either as free-living forms or asparasites of other organisms. Insects are undoubtedly the dominant form of life from the Arctic to the equator. Some of them live under snow and ice, others - in deserts, others - in s alt lakes and hot springs. The world of insects is very diverse. There is even a fly (Psilopa petrolei) in southern California that spends part of its life in pools of oil. One of the main reasons insects thrive is their ability to fly.
Ability to fly
With the exception of a number of primitive forms, most insects move freely in the air, which allows them to explore new habitats, elude predators, find partners and find food with greater ease than their wingless invertebrate relatives can. Some of them even catch prey in the air. Although insects owe their prosperity to flight, the ratio of their body weight to wing area is such that theoretically they should not be able to fly. In fact, the muscles of their wings generate and realize energy at a tremendous speed. The high stroke rate compensates for the lack of lift.
Insect sizes and their role in evolutionary prosperity
The size of insects also played an important role in their evolutionary prosperity. When they first appeared, about 350 million years ago, the conditions of existence already resembled the current ones. Insects have mastered free until then ecological niches. This explains their relatively small size (although fossil dragonflies with a wingspan of up to 76 cm are known): they cansurvive and reproduce in conditions unfavorable for larger animals.
Primitive insects
Insects are believed to have evolved from centipede-like ancestors, from which they differ mainly in having only three pairs of limbs. Each pair is attached to one segment of the chest (middle part of the body). The most primitive of modern species are those wingless insects, examples of which belong to the four orders grouped under the name Apterygota. All others have wings and are designated Pterygota. Springtails and bessyazhkovye probably descended from creatures similar to twotails, but both groups developed in different directions. Springtails are characterized by a special fork on the abdomen, which acts like a spring and allows these animals to jump well. The bessyazhki do not have antennae, and part of their functions are carried by the forelimbs.
Main groups and orders of winged insects
An important step in the evolutionary development of insects was the development of wings and the ability to fly. Two orders - mayflies and dragonflies, whose representatives cannot fold their wings on their backs during rest, are united in the Palaeoptera (ancient-winged) group. Insects with this ability form the group Neoptera (new-winged). Seven orders are considered the most primitive of the Neoptera. They are characterized by a fairly simple mouth apparatus. In addition, they are mainly herbivorous insects. Examples: earwigs (pictured above), termites, cockroaches, praying mantises, etc. A detachment of stoneflies -side branch with many archaic features. Squads of bug-like insects show a gradual improvement in the oral apparatus. It is primitive and unspecialized in hay eaters (pictured below) or developed piercing-sucking in bedbugs.
The rest of the insect orders (Neuropteroidea) have received significant advantages over their more primitive relatives by improving the development cycle.
Insects with incomplete and complete metamorphosis
Usually, all species from Palaeoptera and Neoptera are divided into two groups, depending on the development cycle. Insects with incomplete metamorphosis (examples of them are Hemimetabola and Apterygota) are characterized by the fact that the juveniles (nymphs) hatched from eggs resemble adults. Later, after going through a series of molts, the nymphs become fully formed adults. In insects with complete transformation (Holometabola), the larva hatched from the egg does not look like an adult at all.
This stage (caterpillar or worm-like larva) usually eats completely different food. The larva turns into a pupa, which can remain dormant for many months, and then, by metamorphosis (tissue rearrangement), turns into an adult insect. Differences in lifestyle between her and the adult allow them to use completely different habitats. Holometabola includes 84% of the total number of insect species, and many of them are of great economic importance.
Hymenoptera
Hymenoptera - an extensive detachment representing the world of insects. They are characterized by the fact that the basic plan of the structure of them practically does not change. However, these animals are significantly different from other insects with complete metamorphosis. This is a rather isolated group, but in terms of the nature of larval development and metamorphosis, it approaches scorpions.
Adaptation to the environment
Coleoptera, the largest order in the animal kingdom, are characterized by the development of rigid elytra covering the posterior pair of membranous wings used for flight. The strength of the external skeleton and the adaptive capabilities of the main body plan turned out to be the leading factors in the development of various habitats by adults. The rest of the fully metamorphosed insects are grouped around the once vast squad of scorpions.
Butterflies are recognizable by their scaled wings and specialized nectar-feeding mouthparts. The evolution of this order and some representatives of the Diptera order was in close connection with the evolution of flowering plants.
Caddisflies branched off from butterflies, acquiring hairy wings and chewing mouthparts. The larvae lead an aquatic lifestyle. Diptera fly with the help of the front pair of wings, and the second is turned into h alteres, which play the role of balance organs in flight. Diptera larvae show a greater adaptive specialization than other insects. Many adults feed on blood, which is whatdue to their role in the transfer of pathogens of infectious diseases. Close to Diptera are fleas, they have no wings and the body is flattened from the sides. Together with the order of lice, this group belongs to the number of ectoparasites of warm-blooded animals.
Insect pest problem
Many evolutionarily advanced forms of insects from Holometabola often cause significant damage to humans. They can destroy crops or spread dangerous diseases. Among the Hemimetabola, such insects are few. Examples (pests) are lice and locusts. But they cause great harm to man. One species alone, the Desert Locust (Schistocerca gregaria), can cause starvation for more than 10% of the world's population. This insect (pictured below) reproduces rapidly after heavy rains and suddenly spreads widely, eating any greenery in its path.
However, it must be said that mostly insects are practically harmless. Moreover, they play their irreplaceable role in nature.
So, we have considered such an interesting and numerous group of animals as insects. Examples, names, classification and characteristic features of them were presented in the article. We hope you enjoyed reading and found useful.
