For flying animals, the speed depends on the size. A ladybug, for example, is slower than a griffon vulture. On the one hand, the braking surface shrinks relative to the body mass with increasing size, on the other hand, large wings can also generate more thrust. Very small animals even have an additional problem: if you are less than half a millimeter tall, like the dwarf beetle Paratuposa placentis, the tenacity of the air begins to make itself felt. But in fact, the paratuposa does not slow down at all. The small insect flies even faster than its body size allows. Its speed is more suitable for an animal three times its size.
Experts around Alexei A. Polilow from the Lomonossow University in Moscow have now examined in detail how the tiny dwarf beetle undermines the laws of aerodynamics. As the working group in "Nature" reports, the noticeable toughness of the air on its size scale even helps him. It allows him to make a wing shape that would not work at a goose vult. Instead of a wing membrane, paratuposa placentis uses a curved bar from which all -round fine bristles go off. The construct is similar to a mixture of dust fronds and down feather. But that alone does not explain the unusual flight performance of the dwarf beetle. Many very small beetles have such feathered wings.
To find out how the little beetle uses its wings, Polillov's team recorded its wing beats with a high-speed camera. It turned out that the superfast Paratuposa performs a wing beat that has never been observed before. Each beating cycle consists of four wing beats in which the wing moves along a lying figure-of-eight. At both ends of the eight, a strong downward stroke generates buoyancy, followed by a slow diagonal upward stroke to the starting point of the next downstroke.
The working group then modelled the air flows around the wings as well as the movements and forces that occurred during the novel wing stroke. Her result shows that the special sequence of movements distributes muscle strength better within the stroke cycle and makes the flight more efficient, she reports. This complex impact cycle is probably only possible with the light feather wings of the insect – membrane wings would probably be simply too heavy. The team's results suggest that, on the one hand, the particularly light wing and, on the other hand, the special impact cycle made possible by it enables Paratuposa placentis to fly with exceptional speed and acceleration.
