The structure of insects is based on an unchanged structure for hundreds of millions of years: the body consists of three segments, head, thorax, and abdomen, with two pairs of wings, three pairs of legs, and two compound eyes.
But this basic structure declines in countless variations, which are as many as the needs of adapting to an environment.
Insects are the largest group of animals. There are more than a million known species, but experts estimate there are at least ten million, and some, more optimistic, say there may be as many as 70 million.
We live, according to scientists, in an “insect age”, a more fascinating age, as we still have millions of species to discover.
Insects appeared about 400 million years ago, and almost all orders of insects that existed 200 million years ago have representatives in today’s fauna. It’s an impressive example of survival, the result of perfect adaptation to the most diverse living conditions.
The answer to this question is resounding, but, yes, insects are animals. Now let’s look at why.
Archaea, Bacteria, and Eukarya are the three taxonomic domains. The first two mainly include single-celled organisms, but only Eukarya exhibits organisms with cellular nuclei. Does that mean everything in Eukarya is an animal? No, it’s not. To reach this point, we must move to the “Kingdoms”.
After all, trees are multiple cellular organisms with nuclei, but the third is not obviously an animal! Therefore, at the level of the “Kingdom”, there is a classification known as Animalia. The species grouped in the animal kingdom have several common features:
With a small number of exceptions, all animals meet these basic criteria. So, the next time you are asked whether insects are animals, you can say they are because they reproduce sexually, breathe oxygen, consume organic material, and are able to move”.
Now that we have established that insects are animals, let us see exactly what percentage of the Animal Kingdom is represented by insects.
Today there are approximately 1 million known insect species. This represents about 70% of all animal species. In total, along with invertebrates, which include arachnids, crustaceans, and other species, represent 96% of all identified animal species.
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When you compare the number of insects, under the “insect class”, you see the amazing biodiversity of insects.
Number of species (Chapman, 2009)
Most importantly, the percentage of insects compared to other animals should continue to increase in the coming decades.
We don’t know everything, but some of the reasons could be:
The adaptability of insects
Insects are a group with great plasticity, evolving rapidly and adapting to changes, new situations, and opportunities.
Phytophagous insects eat a large number of plants, while other insects feed on animals, vertebrates, or invertebrates, dead or alive. There are also a bunch of insects that eat “our” food, including heat-processed, cooked food, clothes, feathers, blood, cork stoppers, paper, dung, and almost anything else!
The ability to fly
It is a quality that allowed insects to spread and conquer new territories.
It is one of the most fascinating features of insects. They go through several stages of life. The larvae being much different from adults gives them the opportunity to exploit other food resources.
The external skeleton
A true technological wonder. Composed mostly of chitin, it is lightweight, flexible, and also very resistant to chemical and mechanical aggression. From this excellent material, nature has produced a huge variety of designs. And today, insects continue to evolve, adapt and spread. Optimistic scientists say insects will continue to live on Earth long after we, humans, will no longer be.
Their three pairs of legs can have the most varied appearance, with claws for hanging (on lice), wider parts that serve swimming (on aquatic insects), and adhesive discs for holding on different surfaces – this is how flies manage to stand on a smooth vertical wall, and many others.
Born to jump
Order of the Orthoptera
In crickets and locusts, the hind legs are designed for jumping. Very long, with strong muscles, they developed a considerable force that propels the insect’s body a few meters away. This is a remarkable performance for a creature of only a few centimeters long.
Their weapon is their foot
The order of the Mantodea
Predator insects, the praying mantis, have as their main weapon of attack the pair of anterior legs. Knife blade mechanism, plus toothed edges like saws, plus catch speed equal effective and scary attack weapons.
The praying mantis is able to capture in a fraction of a second prey of their size or even larger. Large species of exotic praying mantis can capture, besides insects and spiders, small vertebrates such as frogs, lizards, rodents, or hummingbirds. These insects are famous for the fact that females tend to devour, after mating, males of their own species.
Thousands of facets
Compound eyes. Each facet faces a different direction from its neighbors. They capture a general impression of the color and luminous intensity of a portion of the object being watched and transmit a fragment of the total image. Insects can only see well at short distances, but they can sense extremely fine movements.
Insects were the first winged creatures to appear on Earth. Although there are species without wings, most insects have wings, and these are among the most important characteristics of their classification. By the appearance of the wings, a butterfly is clearly distinguished from a dragonfly, for example, or a cockroach.
Shapes and colors – Camouflage
Sometimes, insects’ silhouettes mimic so well certain parts of plants that the result is an enviable camouflage. What appears to be a branch, a leaf, or a flower may actually be an insect. Even the thorns of plants can become the “inspiration” for some insects.
Sometimes, insects’ body structures represent functional adaptations to flight, as are the thin and elated bodies of dragonflies. Other times, they are durable, compact constructions, as in the case of almost semi-ferric bodies of ladybugs.
We live in the age of insects. They are invertebrates with segmented bodies and constitute the largest group of animals. There are about a million known species, exceeding the number of all other species of animals. What is the reason behind their success? They are the only arthropods capable of flight.
They have conquered all living environments, as they can use the most diverse sources of food. They play an important role in nature and in human life. Some insects cause man a lot of trouble because they damage crops and stored products, or transmit diseases.
But let’s not just talk only about the bad. Insects are also the most important pollinators, and predatory species regulate the number of harmful ones. Some recycle decomposing organic matter, others produce honey, wax, and silk. Let’s not forget the joy of admiring the beauty of butterflies, the elegant flight of dragonflies, the wonderful shapes and colors of cockroaches, or the song of crickets. Get to know them better.