The Pocket Book of INSECT ANATOMY
Across the great and varied sweep of life on Earth, insects stand out as one of the greatest success stories.
Most invertebrate animals live in the oceans and fresh waters, but insects have truly conquered the land, and (as the only winged invertebrates that have ever lived) they have also mastered the air. This mastery comes courtesy of a basic anatomy that meets the challenges of life out of water, and thanks also to countless anatomical modifications that allow insects to thrive in so many different habitats and ecological niches.
For all their fabulous variety, insects have the same fundamental body-plan, which allows them to be recognised at a glance. e segmented body has three distinct sections: the head, the thorax and the abdomen. there are six legs and (usually) two pairs of wings attached to the thoracic segments, and there are obvious eyes and various sensory and feeding appendages on the head. Whether the insect crawls, runs, climbs or hangs, whether it flies with a rattling zoom, a buzz or a flutter, whether it hunts prey, chews leaves or sucks nectar (or blood), it does so with its own version of the same physical equipment that first evolved more than 350 million years ago.
One of the keys to insects’ success in the open air lies in their outer covering – a waxy cuticle that helps prevent their tiny bodies from dehydrating. To take oxygen from the air, they use spiracles – breathing apertures in the body segments, which take in air passively and can be opened and closed as needed. Instead of blood contained in vessels, they have free-flowing haemolymph, which helps keep their bodies rigid and aids
movement, as well as transporting nutrients and waste materials to the appropriate parts of the body. the nervous system is modular – in a sense each of the body segments has its own individual and autonomous brain – and some other body systems show a similar modularisation. these are just
a few of the many ways in which insect bodies are structured and function completely differently to our own, though it is the process of complete bodily metamorphosis, from worm-like larva to winged adult, that astounds us most of all.