This is mind blowing.
It is very well written, and easy to understand. Another very cool use of scanning electron microscopy, and computational fluid dynamics.
"Our experiment combines three-dimensional reconstructions of morphology and kinematics in one of the smallest insects, the beetle Paratuposa placentis (body length 395 μm)."
Check out the size of the beetle!
Another interesting thing to ponder is how flight is achieved/controlled, at such small scale. This goes far beyond the standard discussions between lift and thrust.
"Compared with larger sizes, flight at small sizes is dominated by viscous air friction rather than inertial forces resulting from the acceleration of the surrounding air. This competition between friction and inertia is key for flight at all size scales and thus applies to all animals that move through air."
It would be really helpful to see an animated model of the wing stroke. It's rather difficult to visualize for someone (like me) unfamiliar with the language of this specialty.
The tl;dr: is that the wing made of bristles provides 68% of the lift of a membrane wing, yet masses only a fifth as much, so they don't need to store and recover elastic energy, like most beetles, to fly 3x as fast as their size would suggest.
I found a swarm of almost invisibly tiny thrips settled on a surface in my backyard, years back, and was duly amazed, but these are much smaller! Notice the pic in the article comparing the whole beetle to a single-celled amoeba.
They note the wing mass of 0.013 micrograms, less than a fifth what a membranous wing would mass. In the methods section, they reveal they got this mass by adding up how much the measured volume of chitin must weigh. Actually weighing something 0.013 ug would be very hard. Imagine collecting the wings of 38,000 beetles to get up to a milligram so you could weigh them!
This beetle innovates vs other bristle-winged insects by having bristles on the bristles, improving their effectiveness. The bristle is very tiny. Can the finer detail really be made of separate cells? Or are they sculpted of raw chitin by the cells making up the bristle?
Another interesting thing to ponder is how flight is achieved/controlled, at such small scale. This goes far beyond the standard discussions between lift and thrust. "Compared with larger sizes, flight at small sizes is dominated by viscous air friction rather than inertial forces resulting from the acceleration of the surrounding air. This competition between friction and inertia is key for flight at all size scales and thus applies to all animals that move through air."