BOB HIRSHON (host):
Where did all the giant insects go? I’m Bob Hirshon and this is Science Update.
Three hundred million years ago, the Earth teemed with giant insects, including dragonflies with 2-foot wingspans. Where did they all go? Well, new research supports a theory that dropping oxygen levels in the atmosphere forced insects to shrink. The study found that the respiratory system of a modern beetle takes up a larger fraction of its body the bigger the beetle is. If a beetle grew too immense today, it wouldn’t have enough room in its body for nerves and tendons. But in the past when more oxygen was available, the respiratory system didn’t take up so much room, and the beetle could grow into a giant.
And 500 million years ago, a relative of modern insects called the trilobite burst onto the scene. It turns out that there were17,000 species of trilobites; a new study in the journal Science compares nearly 1,000 of them for clues to the explosive pace of their evolution. I’m Bob Hirshon, for AAAS, the science society.