Arthropods came to be the dominant life form in the Carboniferous period, about 300 million years ago, when much of the earth's land surface was covered by lowland swamps. The warm, humid climate of these vast swamps permitted luxuriant plant growth, which in turn supported a variety of animal life.

Carboniferous era swamps swarmed with arthropods. Scorpions and spiders preyed on other invertebrates (animals with no backbone or internal skeleton). Carnivorous (meat-eating) centipedes, herbivorous (plant-eating) millipedes, and primitive cockroaches foraged among rotting plant remains, while giant dragonfly-like creatures patrolled the air above for small flying insects. Katydid-like insects foraged among the shrubbery.

Why is it so hard to study insect evolution? Because insects are, for the most part, soft-bodied and so decay rapidly when they die, leaving behind few clues about themselves.

There is a natural preservative that helps scientists to investigate insect history: amber, or fossilized tree resin. Insects become trapped in the sticky resin, and their fate is literally sealed when the resin turns to amber. A few million years later, scientists can study the fossilized creatures for clues to the past.