4 Giant Prehistoric Bugs

Do you get uneasy at the sight of bugs? Just be thankful you don’t live in prehistoric times. Hundreds of millions of years ago, Earth was populated by massive insects. We’re not talking about a few inches long—we’re talking bugs the size of dogs and vermin the size of cars.

So today, we’re going to take a look at 4 giant prehistoric insects you’ll be glad are now extinct.

1. Meganeuropsis

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Meganeuropsis is an extinct order of insects that are related to modern-day dragonflies. Meganeuropsis could measure over a foot long and have a two-foot wingspan, making them the largest known unambiguous insect in history. These giant dragonflies satiated their presumably massive appetite on frogs, mammals, reptiles, and other insects. So if modern dragonflies freak you out, just be glad you aren’t dealing with one the size of a small child.

2. Jaekelopterus

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Although not technically an insect, Jaekelopterus is the largest known arthropod to have ever existed. Jaekelopterus possessed a set of large pincers and is thought to have reached sizes up to 8 feet long. You think modern scorpions are bad? Just imagine an ancient scorpion as long as a surfboard with claws the size of your head. Scientists believed that Jaekelopterus was a highly efficient apex predator that hunted using its large claws and excellent eyesight.

3. Arthropleura

Modern millipedes are known for their numerous legs and worm-like bodies. Arthropleura is an extinct genus of millipede which regularly grew to sizes greater than 10 feet long. With their long, flat bodies, Arthroplerua scuttled around on rainforest floors, like giant armored carpets. Despite its fearsome size and large mandibles, Arthropleura was herbivorous and subsisted off decaying vegetation on forest floors. Arthropleura went extinct about 300 million years ago after the collapse of Carboniferous rain forests.

Credit: Spencer Wright via Flickr CC-BY-2.0

4. Megarachne

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Discovered in 1980, Megarachne was an extinct genus of sea scorpions that lived about 300 million years ago. Megarachne was thought to grow up to 2 feet long with 8 limbs that it used to sweep food into its mouth. Megarachne was originally identified as an extinct genus of spiders, which would have made it the largest known species of terrestrial spider. However, further research showed that it actually was a kind water-dwelling arthropod. Either way, imagining a 2-foot wide sea spider with bladed limbs is sure to give your nightmares.

Why Were They So Big?

The largest known existing insects rarely top more than one foot. So what happened and where did all the giant bugs go?

Giant bugs were able to evolve thanks to the higher oxygen content in the early Earth’s atmosphere. 300-200 million years ago, Earth’s oxygen levels were about 50% higher than they are today. Since bugs breathe through small holes on their bodies (called spiracles), prehistoric insects could take in a lot more oxygen and grow to considerable sizes.

However, this increased size was also a disadvantage. As dinosaurs evolved to fly, they quickly cut down on the number of giant insects by controlling the skies. As oxygen levels fell over time, insect sizes fell as well.