A number of biologists have probed the history of insects to determine what factors account for their huge diversity. Peter Mayhew, a biologist at the Univer- sity of York, has tested the leading hypotheses. Insects don’t seem to have a par- ticularly high rate of speciation, he has found, but they do seem good at with- standing extinctions. Fifty percent of all families of insect species alive today existed 250 million years ago. None of the families of tetrapod species alive 250 million years ago exists today; all have been replaced by newer groups. So what gives insects their sticking power? Mayhew argues that a few key.
