They appeared on earth 400 million years ago, long before the first reptile, bird or mammal, and they may well last 400 million more. They make up about 75 per cent of the 1.2 million currently known species of animals and no-one knows how many millions of them have yet to be discovered. As many as 30,000 of them co-exist and interact in one square yard of the top inch of a forest's soil. The success story of insects, unparalleled in evolution or...