How the world's smallest beetle can fly as fast as a large insect

Up until now, scientists believed that the world's smallest beetle couldn't fly. 

They suspected the featherwing beetle, which is less than one-third of a millimetre long, had to be carried by the wind, like how plankton float with air currents.

But a team of entomologists was curious, and driven to explore the microscopic world. They travelled to Vietnam and climbed up trees to study the tiny creatures, unraveling the mystery of the beetle's flight. They discovered the featherwing can fly as fast as much larger insects thanks to its narrow and feather-like wings.

The findings were published in the journal Nature last week.

"This is something that was quite unexpected," study author Pyotr Petrov,  a senior research fellow at Moscow State University, told As It Happens host Carol Off.

Flying for them is a little bit like swimming in syrup would be for us- Pyotr Petrov, entomologist and study author

Not only did Petrov see the tiny beetles flying well, but he described it as a "very peculiar flight."

The entomologists recorded footage of the beetles and later zoomed in to see how they row their long and lightweight wings "like crazy" in the shape of a wide figure eight. 

At the same time, featherwing beetles also use their wing cases — a pair of wings, hardened and thickened as a protective shield for folding — to row and stabilize the position of their bodies in flight.

This helps them move through air that would normally be too thick and viscous for such small creatures to navigate. The general rules of physics say that air viscosity grows relative to weight — so the bigger an animal is, the faster it can fly. But at this scale, the featherwing beetle shows how the laws of physics can work differently.

No other beetles are known to use their wing cases to fly.

"We expected that there would be something special," Petrov said. "Because flying for them is a little bit like swimming in syrup would be for us."

Canadian entomologist Gil Wizen, who got up close to another insect and won an award for the photos he captured last year, is impressed by the scope of this study.

"I am interested in the life history of insects, especially the overlooked ones like these," Wizen said in an email to As It Happens. "The tiny beetles live inside mushrooms growing high up on tree canopy. How do they get up there? How well do they fly in terms of speed and aerodynamics? Now, thanks to this study, we know."

Wizen also noted how as a macrophotographer, he sees the videos of the tiny, featherwing beetles as a technological achievement.

"Don't forget this 400 micron (or 0.4 mm) multicellular beetle is as small as a unicellular organism," he said.

Petrov says the size of featherwing beetles is part of their evolution, as bugs have historically been getting smaller.

"[The] earliest insects that existed 400 million years ago were never so small as the smallest insects today....This is one of the ways which allows animals, not exclusively insects, to live [and] survive," he said.

"The whole thing is about understanding how evolution works and, in this case, how evolution of flight works," he said.

Written by Mehek Mazhar. Interview with Pyotr Petrov produced by Chris Trowbridge.