We explain what insects are, what their anatomy is like and what they feed on. Also, what are its characteristics, habitat and more.
What are insects?
The insects are a class of invertebrate animals belonging to the phylum arthropodsalong with arachnids, crustaceans and myriapods.
They are the most abundant and diverse animals in the entire world, as well as the most evolutionarily successful. They represent 90% of known life formswith more than one million known species and an estimated 6 to 10 million species yet to be discovered.
Like the rest of the arthropods, insects have a segmented body with jointed legs and external skeletons (exoskeletons) of chitin, which allow them tremendous resistance and adaptability, which is why they are the largest class within the largest animal phylum that exists.
Nowadays It is possible to find them in almost any habitatand it is estimated that there are about 200 million insects for every human being in existence. If we are to say, the planet is actually theirs.
See also: Scorpio
How did insects originate?
The insects appear in the fossil record in the Lower Devonianmore than 400 million years ago.
They survived the mass extinction at the end of that period to populate the Triassic.
The first modern families appeared in the Jurassic and then they diversified enormously in the Cretaceous.
The concentration of atmospheric oxygen in those times was much higher: it occupied 21% of the atmosphere, instead of the current 16%. This allowed much larger insects emerged than those that exist today.
Anatomy of insects
Insects are distinguishable from other arthropods by their anatomy, which consists of:
- Head. In the form of a capsule, it contains the eyes and antennae, the latter always in a single pair. The eyes, on the other hand, are usually compound and large in size, made up of hundreds of circular or hexagonal vision cells. In addition, they usually have three simple eyes or ocelli on the top of the head. Their oral apparatus is adapted to their mode of nutrition, allowing them to chew, suck, chew-lick, cut-suck or bite-suck depending on the species.
- Chest. The middle region of the body containing the internal organs and limbs is divided into three parts: prothorax, mesothorax and metathorax. Each has a pair of legs (always 6 in total) and the last two have a pair of wings (always 4 in total) when present. In some cases there may be only one pair of wings on the mesothorax or metathorax. Not all insects fly.
- Abdomen. The posterior and most vulnerable region of the body, generally covered only above by the exoskeleton, contains the excretory and reproductive organs, as well as the viscera. At the end, appendages with different functions may emerge, as in the case of bees or other poisonous stinging insects.
What do insects eat?
The diet of insects is enormously varied. Most of them feed on plants and vegetables.: its leaves (especially in the caterpillar phase), its fruits, its sap or the nectar of its flowers.
In fact, insects were some of the first successful herbivores in the history of life, thus contributing enormously to competition between plant species.
Other insects are detritus-eating, feeding on waste and decomposing organic matteror using it (like ants) to fertilize fungi that later serve as their sustenance.
And many other species are, instead, predators, hunting and devouring other species of insectsto small mollusks or annelids, and even to small mammals and fish, as is the case of the praying mantis.
Finally, There are also parasitic insects, which feed directly on the blood of animals. Therefore, they can be a danger to their health.
It may be useful for you: Food chains
Insect habitat
They have adapted to practically any habitatwith the exception of water, with very few species living in lakes, rivers or the sea (on the other hand, crustaceans are essentially marine).
Many species are particularly social and build nests or hivesIn them, they can live underground, inside trees or wood, or in mud structures that they build themselves.
How do insects reproduce?
Insects generally They present their sexes separately and different from each other morphologically.
Their reproduction is sexual and they are oviparous.This means that the male carries out fertilisation inside the female’s body (internal fertilisation). The female then lays eggs from which the larvae will emerge.
However, not all insects always mate. Those that live in hives, for example, usually respond to very rigid hierarchies in which only one queen (generally one or a few per nest) is fertilized by a single male.
The queen’s function is to lay eggs incessantly.while the rest of the hive’s inhabitants take care of maintenance and feeding tasks, without ever reproducing.
Another interesting case is that of the parthenogenesis that certain insects developThis consists of the deposition of eggs by females without the intervention of a fertilizing male. From these eggs arise females that are genetically identical to their parents.
This type of reproduction usually occurs when males are scarceHowever, the intervention of a male in one of the generations is necessary to provide genetic variety to the offspring.
Also there are few cases of viviparismIn these, the female expels the live offspring (from the newly hatched egg inside her) or the pupal stage directly from her body.
Metamorphosis
Most insects They are not born identical to their parentsbut must go through a phase of postembryonic changes known as metamorphosis.
In these cases, a larva emerges from the eggs which after a period of feeding and growth, begins the transformation into an adult or imago.
Depending on the metamorphosis process, we can distinguish three types of insects:
- Ametabolos. Those that do not have metamorphosis, but rather their offspring are identical to the adult except in sexual maturity and size.
- Hemimetabolos. Those that present an incomplete metamorphosis, that is, whose offspring (or nymphs) go through different stages of gradual change, becoming more and more like the imago, without going through a pupal stage but with a final stage of more pronounced changes.
- Holometabolos. Those that undergo complete metamorphosis, since a larva emerges from the egg that is completely different from the adult, which must feed and grow until it reaches the nutrients necessary to form a cocoon or pupa, inside which it will change shape again and emerge as a mature adult.
Classification of insects
Due to the gigantic variety of insects, there are numerous orders, depending on their morphological characteristics. The main ones of them are:
- Odonata. Incapable of folding their wings in the abdomen, of incomplete metamorphosis and much more primitive, like the dragonfly or damselfly.
- Blattodea. With a flattened body measuring between 3 and 7 centimeters, they are omnivores and in some cases flyers. Its best example is the cockroach.
- Orthoptera. Their third pair of legs is more robust and allows them to jump enormously, being able in some cases to glide or fly short distances. This is the case of crickets or grasshoppers.
- Phthiraptera. Without wings and parasitic life of different animals, they feed on remains of skin, blood, hair or feathers, like lice.
- Coleoptera. The most abundant order of all, with the greatest diversity and adaptability: that of the beetles.
- Lepidoptera. The order of winged insects, many of which are nocturnal and undergo complete metamorphosis, such as butterflies and moths.
- Hymenoptera. Social insects, of complete metamorphosis and generally live in a nest or hive, where they are part of a hierarchy. Like ants.
Presence of insects in culture
Insects and their mysterious life cycle have always intrigued humans, who have seen in them the symbol of rebirthof the spirit and of eternal life.
Many dynastic orders of antiquity They venerated the beetle, the butterfly or the dragonflywhile other species have always been fought against and considered harmful or dirty, such as flies, mosquitoes and cockroaches, generally considered “pests.”
Other insects have been part of traditional human storiesin which human traits such as selfless work (the ant and the bee), music and laziness (the cricket), vanity (the butterfly), etc. are attributed to them.
In some cultures, in addition, insects are part of the dietHowever, in general human consumption is not well regarded, and its use as livestock feed, or as a tool for the production of fibers (such as silk) or food (such as honey) is much more widespread.
Ecological importance of insects
Insects are extremely numerous and They have many relationships with the rest of the species of animals and plants, on the verge of being ecologically essential today.
As prey, predators or simply as pollination vehiclesinsects contribute to the enormous cycle of ecosystems.
Examples of insects
Some common examples of insects are:
- Bees, bumblebees, wasps and hornets.
- Beetles, cockroaches, crickets, grasshoppers.
- Dragonflies, butterflies, moths and cicadas.
- Bedbugs, mosquitoes, lice, fleas, horseflies.
- Termites, ants, ladybugs and flies.
- Taras, mantises and chipos.