Giant Dragonflies

Dragonflies are quick, light, and pretty bugs. They zip through the air, snatching mosquitoes and flies in the blink of an eye. It is hard to imagine these tiny creatures are related to the biggest bugs that ever lived.

300 Million Years Old

Three hundred million years ago, giant dragonflies ruled the skies. These prehistoric dragonflies were huge. The largest had wings 28 inches wide, a body 17 inches long, and weighed 1 pound. The largest butterfly in the world today has a wingspan of only 12 inches—less than half the size! Fossils of prehistoric dragonflies were found over 100 years ago. The largest dragonfly species ever found was named Meganeuropsis. The name means ―large veined‖, referring to the large veins in dragonfly wings. Scientists were baffled by their large size. 

After all, bugs are not usually this big, and for a good reason. Smaller bugs can hide better from predators and fly faster. Modern dragonflies are very fast and agile, flying around 35 mph. They are called ―mosquito hawks‖ for their awesome ability to catch prey. Prehistoric dragonflies would have been much slower in the air, more like a big commercial jet rather than a swift fighter plane.

Why So Large? 

So why did prehistoric dragonflies get so huge? Scientists think the Earth’s climate 300 million years ago is the key to solving this mystery. The Earth was warm and humid, much like today’s tropics. The tropical conditions were perfect for early plants, like ferns and club mosses, to grow fast.

Thick forests covered the land, releasing more and more oxygen into the Earth’s atmosphere. The oxygen levels reached 35 percent, much greater than today’s level of 21 percent. Bugs could get oxygen into their bodies more easily and grow bigger. The giant dragonfly wasn’t the only large bug found during this period.

Others include a 6-inch cockroach, a grasshopper-like insect with a 14-inch wingspan, a 6 -foot long millipede, and a 7-foot long giant sea scorpion. Meganeuropsis probably hunted in the swamps for mayflies, cockroaches, and small amphibians to eat. As time went by, the Earth’s climate grew colder and drier, with less oxygen.

Giant dragonflies died out around 250 million years ago, but their smaller relatives still remain.