What are insects? And how many species of insects are there? Stuart Blackman explains
Like ‘bugs’ and ‘creepy-crawlies’, the word ‘insects’ is often used as a catch-all term for any small, boneless creatures that buzz, scuttle, flit and, yes, creep and crawl.
But while all insects could be called creepy-crawlies, not all creepy-crawlies are insects.
What are insects?
Insects belong to the phylum arthropoda, a huge assemblage of animals which also includes crustaceans, arachnids and myriapods (millipedes and centipedes).
All arthropods possess a rigid, jointed exoskeleton that is moulted as the animal grows, but unlike other arthropods, insects’ bodies are composed of three distinct parts: a head, a thorax (bearing wings and six legs), and an abdomen. Their immature stages often look remarkably different from the adults – think of a caterpillar and a butterfly, for instance
How many species of insects are there?
More than half of all the animal species described by science are insects, and it is estimated that there are more than five million extant species. That’s a lot of beetles, butterflies, moths, ants, bees, wasps, flies, termites, crickets, grasshoppers, cockroaches, mantids, dragonflies and earwigs, to name just some of the more familiar ones.
Insect flight
Insects’ remarkable success is thought to be due in part to being the only invertebrates to have evolved powered flight, which has allowed them to exploit various niches that are unavailable to more earthbound groups.
Insect flight manifests itself in many different ways, whether it’s the breathtaking control of a dragonfly, the exasperating agility of a house fly, the winsome scattering of a cabbage white, the dogged whirring of a stag beetle or the clumsy bumblings of a daddy longlegs.
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