Featherwing beetles are some of the world’s smallest flying insects. Yet they can rocket along with the speed and agility of much larger insects. Now, scientists have figured out how the beetles do it.
A wide wing stroke combined with lightweight, bristled wings allow the beetles to efficiently propel themselves through the air, researchers report online January 19 in Nature.
Some species of featherwing beetles are particularly tiny; two of the insects set end to end would barely reach a credit card’s thickness. At such small sizes, the air is viscous and air friction becomes a serious obstacle to flight. But previous research from entomologist Alexey Polilov of Lomonosov Moscow State University in Russia and colleagues showed that the insects can fly at speeds comparable to that of beetles three times as large.
Polilov and his team investigated this flying prowess further, studying one of the smallest featherwing beetles, Paratuposa placentis, using high-speed video and computational simulations.
The beetle’s style of beating its wings is unlike anything previously described, the team found. Its wings make a wide, figure-eight pattern, clapping together at the top of their upstroke to reduce drag and meeting again at the bottom of the downstroke. This wide motion gives the beetle extra power to push through the air.
Crucially, the beetle’s wings are made of bristles. Because of the air friction at these small sizes, those bristles allow the wings to have the flapping power of wings made of membranes, like those of a housefly, but for a lot less mass.
“The bristled wing rows almost as well [as membranous wings] without letting much air through, like the feather of a bird,” Polilov says. Video recordings of some other featherwing beetles show they have a similar flying style, the researchers say.
The beetles’ ancestors were larger than their modern kin. The findings give insights into how insects can retain important athletic abilities as they scale down in size.