Scientists at the University of California in Santa Cruz have found why insects got smaller despite rising oxygen levels about 150 million years ago. This fossil wing of Stephanotypus schneideri from the period about 300 million years ago when insects reached their greatest sizes, measures 19.5 cm (8 inches) long. The largest species of that time were even bigger, with wings 30 cm long. For comparison, the inset shows the wing of the largest dragonfly...
