What Was the Biggest Insect That Ever Lived?

Atlas moth

We like big bugs and we cannot lie.

So when our friend Doug Rhodehamel wondered, “What’s the largest insect that ever lived?” Weird Animal Question of the Week went hunting for giants, past and present.

We found some ancient behemoths, some lovely ones, and some that could pass for Halloween decorations.

A Big Bug’s Life

Imagine a dragonfly so big its wings could block your 27-inch TV screen.

The largest insect fossils ever found are griffinflies and giant dragonflies, says Matthew Clapham, a paleobiologist at the University of California, Santa Cruz. Subtle anatomical differences separated the two groups.

With wingspans that could reach 27 inches, the largest known insects of all time are griffinflies from the genus Meganeuropsis, Clapham says via email. The largest of their fossils were found in France and Kansas and were 300 million to 280 million years old. By comparison, modern dragonfly wingspans top out at about eight inches.

Not that we’re complaining, but why did these big bugs shrink?

Tom Turpin, an entomologist at Purdue University, says that it may have to do with high oxygen levels in the prehistoric atmosphere. All that oxygen would have supplied big insect bodies well, but when oxygen levels decreased, it’s possible that larger insects were unable to survive, Turpin says via email.

The rise of birds may also account for the shrinkage of bugs. One piece of evidence for this idea: Insect size decreased in the late Jurassic period when birds became more agile fliers, even though oxygen levels rose at the time, Clapham showed in a 2012 study.

“Large insects would have been less maneuverable, especially when taking off from tree branches or the ground,” and would be easier prey for birds, with whom they would also be competing for food, Clapham said via email. (Related: “Giant Bugs Eaten Out of Existence by First Birds?”)

Modern Monsters

These days the biggest wingspan belongs to the beautiful white witch moth of Central and northern South America, which measures from 10 inches to nearly a foot across, says Katy Prudic, an entomologist at the University of Arizona. The Asian Atlas moth boasts the largest wing surface area of 62 square inches, slightly larger than a DVD box, which is 44 square inches.

The crown for largest butterfly wings goes to Queen Alexandra’s birdwing of New Guinea, with a wingspan of 7.5 to 11 inches. In butterflies, “the boys are more showy, similar to many birds,” Prudic says. (See video: “World’s Largest Spider”)

In our creepiest Halloween decor category, the heaviest “reliably reported” insect, according to the University of Florida’s Book of Insect Records, is the giant weta. According to Fact Bites: Bug Bites by Roger Priddy, the weta is referred to by the Maori as “the god of ugly things.”

This endangered member of the cricket family is found only in New Zealand and can weigh as much as 2.5 ounces; that’s the size of a small blue jay. (Here’s a weta sticking up for itself against a cat.)

And yet the weta is outweighed by a larvae, the grub of the goliath beetle, which weighs in at 4.1 ounces. We’d say “You big baby,” but we don’t want it to remember us when it turns into an adult.

The likeliest candidate for longest insect is Chan’s megastick, a walking stick native to Malaysian Borneo, the female of which measures in at nearly two feet long.

Considering the time of year, we’ll call her Stickabod Crane.

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