(ORDO NEWS) — In terms of insect flight, when the wings are compressed, the force of friction overpowers the energy of flight. When the wings shrink, the friction of the air absorbs the energy of the flight – that’s why dragonflies hover while hoverflies flutter. However, a beetle the size of a grain of sand turns this principle on its head.
The stag beetle (Paratuposa placentis) is less than half a millimeter long, smaller than some single-celled amoebae.
At this size, the air environment turns into syrup, and scientists at first believed that the beetles simply drift where the wind takes them. However, a new analysis published in the journal Nature shows how they use light wings to keep up with species that are three times their size.
These beetles have bristly, feather-like wings. These porous appendages are soft and produce much less friction than the standard webbed wings that flies have, which helps the beetles move.
A number of insect species, including parasitic wasps, have evolved related wings as they shrank in size, but these beetles are using a previously unknown method to generate their enormous flying abilities, according to the authors of the new study.
In 2017, experts collected these beetles from pieces of mushrooms in the jungles of Vietnam. To capture the beetles’ infinitesimal flight patterns, the experimenters placed them in a transparent camera and filmed them with two high-speed cameras at nearly 4,000 frames per second during a series of tests. They used these recordings to create a 3-D model of a miniature beetle and calculate its aerodynamics.
According to study co-author Dmitry Kolomensky, a physicist who studies fluid mechanics at the Skolkovo Institute of Science and Technology, the researchers found that instead of flapping their wings up and down, feathered beetles loop in an “exceptional” figure-eight pattern.
After the bristly wings unfold from a protective sheath called elytra, they mirror each other as they move, flapping against each other in front of and behind the insect a movement that Kolomensky says is reminiscent of a redundant model of swimming strokes like the butterfly. The elytra stabilize the beetle and its flickering wings, preventing it from spinning.
The similarity of the specimen to swimming greatly intrigued Arvind Santanakrishnan, a mechanical engineer who studies the aerodynamics of tiny beetles at Oklahoma State College.
“Sometimes this swimming is seen in small aquatic crustaceans such as water fleas,” says Santanakrishnan, who was not involved in the study. “It was pretty amazing to see tiny feathered beetles using a similar technique to get around.”
Kolomensky and his colleagues hope they can take flight models of other, equally tiny beetles as an example. They argue that their findings could influence how engineers cut flight know how though Kolomensky admits it could take some serious engineering feat to create a drone with the proportions of a feathered beetle.
“Most likely it won’t be that small,” he says. “However, this remains to be explored.”
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