Class Insects: examples, types, features

The insects, examples and characteristics of which we present today, are the largest group of all the creatures that inhabit our planet. It includes about 80% of the total number of animal species. More than 1 000 000 species includes such a group as insects. Examples that are known to science are far from all species existing in nature. Perhaps as much remains to be discovered. Many fossil and living primitive forms are described, which clarify the evolution of the modern 29 orders into which insects divide. Examples of modern species will be discussed in this article. Most fossil forms belong to the Lower Carboniferous (345 million years ago). At that time, extensive swamp forests already inhabited winged insects.

Ubiquitous animals

Even in the sea live insects. Examples of such species, however, are few. Some of them stay on the surface, others live on the littoral, and one species lives even on the seabed. But wherever any other animals have penetrated, insects inevitably appear either as free-living forms or as parasites of other organisms. Insects, undoubtedly, are the dominant form of life from the Arctic to the equator. Some of them live under snow and ice, others - in deserts, others - in salty lakes and hot springs. The world of insects is very diverse. In southern California, there is even a fly (Psilopa petrolei), which spends part of life in puddles of oil. One of the main reasons for the prosperity of insects 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 develop new habitats, escape predators, find partners and find food more easily than their wingless invertebrates do. Some of them even catch prey in the air. Although insects are obliged to fly by their prosperity, the ratio of the weight of their body to the area of the wings is such that theoretically they should not have flown. In fact, the muscles of their wings produce and realize energy at a tremendous speed. A high frequency of strokes compensates for the lack of lift.

Size of insects and their role in evolutionary prosperity

The size of the insects also played an important role in their evolutionary prosperity. When they just appeared, about 350 million years ago, the conditions of existence already resembled the current ones. Insects have developed free until then ecological niches. This explains their relatively small size (although fossil dragonflies are known with a wingspan of up to 76 cm): they can survive and multiply in conditions unfavorable for larger animals.

Primitive insects

It is believed that insects originated from ancestors similar to millipedes, from which they differ mainly by the presence of only three pairs of limbs. Each pair is attached to one segment of the chest (middle part of the body). The most primitive of the modern species are those wingless insects, examples of which are related to the four orders united under the name Apterygota. All others have wings and are designated as Pterygota. Naughty tails and bald-headed ones probably originated from creatures similar to the twins, but both groups developed in different directions. A characteristic fork-tail is a special fork on the abdomen, which acts like a spring and allows these animals to jump well. At bessyazhkovyh there are no tendrils, and some of their functions carry front limbs.

The main groups and detachments of winged insects

An important stage in the evolutionary development of insects was the development of wings and the ability to fly. Two detachments - the podenki and dragonflies, whose representatives can not fold their wings on their back during the rest, are united in the group Palaeoptera (ancient winged). Insects that possess this ability form a group of Neoptera (new-winged). Seven units are considered the most primitive of Neoptera. They are characterized by a fairly simple oral apparatus. In addition, it is mainly herbivorous insects. Examples: earwigs (pictured above), termites, cockroaches, praying mantises, etc. The squadron is a side branch with many archaic features. The groups of clone-like insects demonstrate the gradual improvement of the oral apparatus. It is primitive and unspecialized in the Cenotes (pictured below) or developed piercing-sucking in bedbugs.

The rest of the insects (Neuropteroidea) received significant advantages over their more primitive relatives by improving the development cycle.

Insects with incomplete and complete transformation

Usually all species from Palaeoptera and Neoptera are divided into two groups, depending on the development cycle. Insects with incomplete transformation (examples of them refer to Hemimetabola and Apterygota) are characterized by the fact that the hatchlings (nymphs) hatched from eggs resemble adults. Later, after passing through a series of rulers, the nymphs become fully formed adults. In insects with complete transformation (Holometabola), the larva hatched from the egg is not at all like an adult.

This stage (caterpillar or vermiform larva) usually feeds entirely different food. The larva turns into a pupa, which can remain at rest for many months, and then transforms into an adult insect by metamorphosis (tissue reorganization). Differences in the way of life between it and the adult individual allow them to use completely different habitats. To Holometabola is 84% of the total number of insect species, and many of them are of great economic importance.

Hymenoptera

Hymenoptera is an extensive group representing the world of insects. They are characterized by the fact that the basic plan of their structure practically does not change. However, these animals are significantly different from other insects with complete transformation. This is a fairly isolated group, but by the nature of larval development and metamorphosis, it is drawing closer to scorpions.

Adaptation to the environment

For coleoptera - the largest detachment in the animal kingdom - it is characteristic the development of rigid elytra covering the posterior pair of membranous wings serving for flight. The strength of the external skeleton and the adaptive capabilities of the basic plan of the structure turned out to be the leading factors in the development by adults of individuals of various habitats. The remaining insects with a complete transformation are grouped around the once vast squad of scorpions.

Butterflies are recognized on scaly-covered wings and specialized mouth parts, adapted to nectar. The evolution of this detachment and some representatives of the Diptera detachment was in close connection with the evolution of flowering plants.

The caddisfly branches off from the butterflies, having acquired hair-covered wings and a chewing mouthpiece. Larvae lead an aquatic life. Diptera fly with the front pair of wings, and the second is turned into buzzing, playing the role of the balance in flight. Larvae of Diptera show a greater adaptive specialization than other insects. Many adults eat blood, which determines their role in the transfer of infectious agents. Close to Diptera are fleas, they have no wings and the body is flattened from the sides. Together with a detachment of lice, this group belongs to the number of ectoparasites of warm-blooded animals.

The problem of insect pests

Many evolutionarily advanced forms of insects from Holometabola often cause significant damage to a person. They can destroy crops or spread dangerous diseases. Among Hemimetabola there are few such insects. Examples (pests) are lice and locusts. But they cause great harm to man. Only one species - a desert locust (Schistocerca gregaria) - can cause hunger for more than 10% of the world's population. This insect (in the photo below) multiplies rapidly after heavy rains and, suddenly spreading widely, eats all the greens on its way.

However, it must be said that in general insects are almost 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 characteristics of them were presented in the article. We hope that the reading turned out to be pleasant and useful for you.