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By: Ikedi Ani-okoye

Insect history

Insects are the naost numerous and successful creatures on Earth. They belong to a Venue o~ Invertebrates known as arthropods, which are characterised by theiry.ointed limbs, segmented bodies, and tough outer skektoar. Arthrnpods i)lay an essential role in all of the Worlds major ecosystems. Although they are less conspit~~ss than other animals, if you look closely you will uncover their incradible variety and learn something about their extraordinary lives.

FIRST SIGNS of life on Earth were single-celled organisms that lived in the oceans around 3,500 million years ago. Jellyfish, simple worms, and other multicellular animals later evolved in the seas, followed by creatures with hard outsides, such as shellfish and trilobites - primitive aahropods. The early sea-dwelling arthropods were later become the very first land-Diving animals, emerging from the oceans as scavengers about 420 million years ago perhaps to escape aquatic predators.

As land plants became more complex, they provided living space and resources for the increasing number of arthropod species - the most successful of all being the insects. Today, invertebrate animals (those without a backbone) make up the majoriry of the world's known species; vertebrate animals ~those with a
backbone) account for less than three per cent. Within the invertebrates, the huge group Arthropoda eclipses all other groups, while arthropods are, in turn, dominated by the insects. It is sstimated that there are about 10 quintillion - 10,000,000,000,000,000,0J0 insects alive at any time.

Unwelcome pests?

Arthropods are seen as troublesome pests by most urban-dwelling humans. Certainly, some are destructive. It is estimated that about 20 per cent of crops grown for human consumption are eaten by herbivorous .Insects. Insects also carry diseases that affect animals and human beings - approximately one in six people alive today is currently affected by an insect-borne disease. The venom of certain arthropods can be fatal, and many people have severe phobias about groups such as spiders and moths.

Real benefits

Most arthropods, however, are harmless. Most arthropods, however, are harmless, For example, less than one per cent of For example, less than one per cent of cockroach species - a much maligned insect group - are significant pests. Many people overlook the benefits that insects bring. Useful products derived from insects range from honey and silk to waxes, oils, natural medicines, and .dyes. In many counties, insects such as crickets, grasshoppers, grubs, and caterpillars still provide nutritious food for humans. Arthropods are also widely used in scientific research, helping us to understand genetics, physiology, and animal behaviour. Many insect species are vital plant-pollinators. Without them, many plants would die out and humans would lose a large proportion of their food
SUpply.

Natural balance

The most fundamental role that the millions of arthropods play is in helping to maintain the balance of the Earth's ecosystems and food chains. These are complex networks that depend on energy from the Sun. The energy is "trapped" by green plants and converted to carbohydrate, which is then eaten by herbivores and converted Into body tissue.

The herbivores are then eaten by carnivores. Most food chains are dependent on insects as the majoring of animals eat insects to survive and many mould not exist without them. Birds, for example, are mostly insectivorous. A single swallow chick may consume around 200,000 bugs, flies, and beetles before it fledges, and even bird species that are seed-feeders as adults rear their young on a nutritious insect diet.

Animal droppings are food for certain beetles and flies, and many insects eat decomposing plant and animal matter. So insects are also helping to keep the Earth's supply of nutrients in circulation. Einally, although insects may cause Serious damage to crops, they

A world of insects

With around 1,500 families of terrestrial arthropods, it would be impossible to include them all in thiS booby. We have chosen a broad range from around the World, including families because they are particularly important common, simply fascinating in some way.

Changing the course of history

Disease-carrying insects have made a major nark on history. Three world epidemics of plague, a flea-home disease, killed millions and altered social structures as a result. Until she use of insecticides during World War II, twice as many people died of insect-9orne diseases as from fighting. Most of Napoleon's altar which set out to conquer Russia in 1812, were killed by typhus spread by the human body louse. In the late 1800s, yellow fever carried by Mosquitoes stopped the building of the Panama Canal 15 years and killed 20,000 workers.