An international study, led by Professor Alexey Polilov of Lomonosov Moscow State University (Russia) and published this week in the journal Nature, explains why the feathered wing beetle (paratuposa placentis) flies amazingly well for its size: a combination of its style of flight together with the morphology and lightness of its wings.
The feathered wing beetle (a fringed-edged wing structure) is one of the smallest non-parasitic insects in existence, with an average size of just 395 microns (less than half a millimeter), which is equal to that of single-celled protists such as amoebas.
A highly efficient flying style
An insect's flight speed is usually related to its size: the bigger, the faster it flies. At small scales there are limitations in terms of air friction, which is usually greater than the power of flight.
However, tiny beetles like paratuposa placentis it can fly at speeds similar to those reached by insects three times as fast.
These beetles can fly at speeds similar to those reached by insects three times faster
The article describes in detail the peculiar flight style of these beetles and shows how their fringed wings, whose mass is much less than other membranous ones for the same extension, work very well in very small arthropods.
"For larger insects, fringed wings are ineffective," Polilov tells SINC, "but on such a small scale, the viscous frictional forces of the air are large enough compared to those of inertia that this type of wings are almost as good - in terms of keeping air out - as the membranous ones of the largest insects".
as if they were swimming
At the scale of these tiny beetles, the air behaves, in terms of viscosity, as if it were water, "which allows them to fly in a style similar to swimming, as if rowing with broom-shaped oars," explains the investigator.
On this very small scale, air behaves in terms of viscosity as if it were water.
The authors have used state-of-the-art techniques, such as optical, electron, confocal laser microscopy and three-dimensional computer modeling, to perform the morphological analysis of the beetles.
"To study their locomotion we have used high-speed infrared video, and 3D reconstruction of the trajectories and movements of the parts of the body in flight, as well as new methods of computational aerodynamics", Polilov points out to SINC.
The study of air flows and forces during the movement of the wings has been analyzed by building scale models of them, and simulating air conditions using glycerol.
"This study is the first to perform a numerical simulation of the flight of this type of insect, and resolves the airflow over individual bristles in a highly realistic 3D configuration," says Polilov.
According to the researcher, the flight cycle they have described in these beetles is different from that of any other known insect, consisting of two power strokes that produce a large upward force and two recovery strokes that generate a smaller downward force.
The flight cycle they have described in these beetles is different from that of any other known insect.
"Until recently, it was assumed that insects such as feathered-wing beetles could not match larger ones in terms of speed and maneuverability in their flight," says Polilov, who anticipates: "In the future we plan to extend our detailed analyzes to other extremely small flying insects, such as parasitic wasps".
Despite their extremely small size, these beetles are multicellular animals capable of advanced behavior and complex movements, including efficient flight.
The Russian researcher's team discovered in previous works that this type of insect flies amazingly well for its size, and what they have now done is "describe its style of flight, which is quite unusual," the researcher emphasizes.
Miniaturization for evolutionary success
The authors conclude that these adaptations could explain how tiny insects have retained such excellent flight performance during their miniaturization process, which could be an important component of their evolutionary success.