5 Main characteristic of insects

5 Main characteristic of insects
Insects are arthropod invertebrate animals belonging to the Arthropoda and Insecta Class. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of jointed legs, compound eyes and one pair of antennae.

They represent the group with the greatest diversity among all animals on the planet.

Examples of insects are: beetles, butterflies, bedbugs, mosquitoes, locusts, among many others.

Main features

Know the main characteristic of insects:

Body structure

Body anatomy of insects

The insects have a body divided into:

  • head;
  • chest and abdomen;
  • a pair of antennas;
  • three pairs of legs;
  • One or two pairs of wings.

Circulatory system

The circulatory system of insects is open.

The colorless blood fluid, called hemolymph, is pumped from a dorsal heart passing from the vessels to body cavities, called hemocelles.

Some insects have accessories hearts to help pump the hemolinph to the wings. The hemolinfa may or may not contain respiratory pigments such as hemoglobin or hemocyanin.

The digestive system

The digestive system of insects is complete. The digestive tube has accessory glands (salivary gland, gastric cediums) and the presence of jaws and oral parts to help manipulate and grind the food.

The digestion is extracellular, through enzymes secreted by gastric cecus. The nutrients are absorbed by the cells of the intestine and distributed by the hemolymph to the rest of the body.

Respiratory system

Insects have tracheal breathing. Air enters the body through spiracles, present on the body surface, and through the tracheas, which are branched tubes, reaching up to the body cells.

Nervous system and excretor

The nervous system of insects is composed of brain ganglia that consists of the union of several nerve ganglia, in addition to several ventral nerves.

The excretas are eliminated through the Malpighi Tubules. They are responsible for removing the excretions of hemolymph and releasing into the intestinal cavity, being eliminated together with the remains of digestion by the anus.

Reproduction and development

The reproduction of insects is sexual, the species are dioicas, that is, with the two sexes separated.

The male releases the spermatozoa inside the female’s body, which are stored in the spermatheque and then are fertilized, so the fertilization is internal. However, in some species it can also be external.

The development of animals can be direct (ametals) or indirect (meta-sbolos).

In the insects ametalollis, when hatching the egg is born an animal similar to the adult. While the methalops go through metamorphosis to reach adulthood.

According to metamorphosis, there are two types of insects:

The holomebolos come out of the egg in the form of a larva, which is quite active and voracious. After this, they go through the pupa phase, also called chrysalis or cocoon, when they stay real and finally reach the adult stage.

Hemi-abolos are born similar to adults, in the form of nymphs and gradually acquire all the characteristics.

Therefore, there are three forms of development: direct, indirect, with incomplete and indirect metamorphosis with complete metamorphosis.


The class of insects can be subdivided into several orders.

The names of the orders end with term ptera, derived from the Greek, and relate to the type of wings.

Because it is a very diverse group, insects are quite different. They vary the types of wings, but have in common the general characteristics that are: head, thorax and abdomen, a pair of antennae and 3 pairs of legs. Not all insects have wings.

Order Coleoptera: beetles and joaninhas

The collegiate order is quite diverse

The Coleoptera Order is the most numerous, with about 400,000 known species.

Its representatives have 2 pairs of wings, the externals being rigid and the internals being the fine and membranous.

Order Hymenoptera: bees, wasps, termites and ants

Bees live in society

The Order Hymenoptera has about 200,000 species, with 2 pairs of fine wings and membranes, and some that do not have wings.

Some representatives of this group live in societies, with a high level of social organization, such as bees and termites.

Order Lepidoptera: butterflies and moths

The Order Lepidoptera has more than 100,000 species, with 2 pairs of membranous wings and specialized oral appliance to suck the nectar of flowers.

Order Diptera: flies and mosquitoes

The fly has only a pair of wings

The Order Diptera contains about 95,000 species, which have a pair of fine wings.

Order Hemyptera: bedbugs

The Hemyptera Order has about 50,000 species, most with 2 pairs of wings, the previous pair being rigid at the base and membranes at the end.

Generally, they are parasitic animals of other animals and plants.

Order Homoptera: cicadas and amps

The Homoptera Order contains about 25,000 species, most with two pairs of wings and some wingless.

Order Orthoptera: locusts and crickets

The Orthoptera Order has more than 11,000 species, most of them with two pairs of wings.

Order of Odonata: dragonflies

Dragonflies have wings of the same size

The Order Odonata has about 5,000 species. They have large eyes, 2 pairs of thin and transparent wings.

Its representatives are predators of other animals.

Order Thysanura: book-rodes

The Thysanura Order has about 500 species without wings, with a pair of long antennae and three long tails.

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