20. Giant Dragonfly

Related to modern dragonflies, the Meganeura is the biggest predatory flying insect ever discovered. Its wingspan reaches from 25 to 28 inches. This terrifying insect lived on Earth roughly 300 million years ago. Higher oxygen concentrations in prehistoric times made it possible for this bug to breathe enough to support its size. Luckily, we don’t have to worry about encountering these bugs that are one quarter the size of a human!

Additionally, a lack of predators contributed to the Meganeura being able to evolve to be so large. Scientists also believe that because they were developed in water before appearing on land as adults, they were more equipped to handle high oxygen levels. Meganeura was a predatory species and feasted on other insects. It’s also possible that they ate small amphibians.