Prehistoric insects are various groups of insects that lived before recorded history. Their study is the field of paleoentomology. Insects inhabited Earth since before the time of the dinosaurs. The earliest identifiable insect is the Devonian Rhyniognatha hirsti, estimated at 407 to 396 million years ago. Forms similar to many modern insects had already evolved before the dawning of the dinosaur and lived alongside them and beyond up to the present day. Like today, prehistoric insects were an important part of the food chain in their time.
The differences between modern and prehistoric varieties can be essential, and, like many other creatures of prehistory, the latter tended to be much larger than their contemporary equivalents. This size difference is thought to be due to higher atmospheric oxygen levels (allowing diffusion through spiracles over greater distances) and higher temperatures (enhancing metabolism).
Since insects have chitin exoskeletons rather than mineralized bones, their burial processes differ compared to the fossils of much larger vertebrates such as dinosaurs. Many insect remains are found preserved in the hardened sap of ancient trees (amber).
Examples of prehistoric insects include: