In the human world, speed is associated with the small, the graceful, the streamlined. But in the insect world things work differently. How fast an insect flies generally depends on its size, yes: but interestingly, the bigger the insect, the faster it flies. That’s why this tiny flying beetler puzzles entomologists so much: it can reach speeds typical of insects three times its size and now we know why.
The fastest bug in town. That relationship between size and speed is well known. In fact, it is due to a purely aerodynamic issue: unlike what happens in human dimensions, the friction of the air generally exceeds the power of flight when we go to very small scales. Therefore, insects need to grow in size in order to develop a power to overcome this friction. Some insects, actually.
I present them to you Paratoposa cakes. The feathered-winged beetle is one of the smallest insects in the world: it measures less than half a millimeter (395 μm) and, as I say, it can fly at speeds similar to those reached by insects that are three times its size. This flight performance has intrigued entomogolians for a long time because it reflected our misunderstanding of the crazy miniaturization race these beetles had gotten themselves into.
A new way to fly. Alexei Polilov and his team has combined 3D reconstructions of the structure and movement of the wings of P. placentis to try to see what happened to it. Their conclusions are that this beetle not only has bristly wings that are lighter than equivalently sized membranous wings, but also that these wings move in a previously unknown way.
Here are some visual examples:
Lessons for microrobotics. As we can see in the videos, the P. cakes it has a flutter cycle of two medium power strokes that produce a large upward force, followed by two slow recovery strokes that produce a smaller downward force. On the other hand, the elytra (stiffened front wings) function as brakes to stop the excessive oscillations that the wingbeat cycles can generate.
These adaptations could explain how the tiny insects have retained such excellent flight performance during their miniaturization process; but, in addition, they can give us very interesting clues when it comes to designing new generations of ever smaller drones.