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!