Whirligig beetles, the world’s fastest-swimming insect, achieve astonishing speeds by using a tactic shared by fast marine animals and waterfowl, according to a study.The centimetre-long beetles may accelerate to 100 metres per second and achieve a maximal speed of 100 body lengths per second (or one metre per second).The study was published in Current Biology.Not only do the findings explain the whirligig’s Olympian speeds, but they also provide useful information for bio-inspired designers of near-surface water robots and unmanned boats.
Until previously, researchers believed that whirligigs achieved their astounding speeds through a propulsion system known as drag-based thrust.To generate push, the insect’s legs must move faster than its swimming speed. To accomplish such high swimming speeds, the whirligig beetle’s legs would have to push against the water at ludicrous speeds.”It could have well been questioned,” said Chris Roh, assistant professor of biological and environmental engineering. “The fastest swimmer and drag-based thrust don’t usually go together in the same sentence.”
Fast-swimming marine mammals and waterfowls tend to forgo drag-based thrust in favour of lift-based thrust, another propulsion system.Using two high-speed cameras synchronized at different angles, the researchers were able to film a whirligig and observe a lift-based thrust mechanism at play.Lift-based thrust works like a propeller, where the thrusting motion is perpendicular to the water surface, eliminating drag and allowing for more efficient momentum capable of greater speed.
Lift-based thrust has previously been identified in large-scale organisms, such as whales, dolphins and sea lions.”In this work, we extended the length scale down to one centimetre, which means that whirligig beetles are by far the smallest organism to use lift-based thrust for swimming,” said Yukun Sun, a doctoral student in Roh’s lab and the paper’s first author.
“We’re hoping that this speaks to bio-inspired robotics and other engineering communities to first identify the right physics and then try to preserve that physics in creating the robotics,” Roh said.
