Insects are a class of the animal kingdom. A class is a relatively high in the order- the list, from bigger to smaller, goes kingdom, phylum, class, order, family, genus, and species. In other words, the term insect encompasses a massive segment of life on this earth. In fact, it is estimated that they make up about 90% of multi-cellular life on this planet, by weight, which is pretty incredible when you think about it. With the insect class, they think there are about six to ten million separate species of insects in total, which is an absolutely staggering amount.

So, what makes an insect an insect then? There are a number of different physical characteristics that a required. First, they need to have a chitinous exoskeleton. They also need to have a three part body made up of a head, a thorax and an abdomen. They also need to have three pairs of jointed legs, compound eyes and tow antennae. If they fulfill all of those criteria, then they are an insect.

They range from the beautiful monarch butterfly right through to the dastardly mosquito, from the humble but vital earthworm to the massive and majestic dragonfly.

There are over six million species of insects in the world and despite their small individual size they make up about 90% of the total animal biomass on the planet. By species number and biomass total alone, insects seem to be one of evolution’s success stories, so how did insects evolve to be such a powerful force on the planet.

There are a number of precursor species that had some of the characteristics of the modern insect, but, critically, not all of them.

These can be dated back to about 500 million years ago.

The first real insects can be traced back to the Devonian Period, which was between 409-362 million years ago. Fossils from this period show insects that have the three part body, the exoskeleton, compound eye and the mandibles that are the telltale characteristics of an insect.

These developments were important as they mark insects out as different from similar arthropods like spiders. While some other animals share similarities, it was around 400 million years ago that the insect combined all of them into a cohesive and identifiable class of animal.

Amazingly, although there is a 400 million year divide between the first true insects and their modern ancestors, differentiating between them is not that easy. The initial innovations were so successful that little improvement on them has been needed.

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