Whirligig beetle uses lift-based thrust for fastest insect swimming

Abstract

Whirligig beetles (Gyrinidae) are the fastest-swimming insects. The one-centimeter long aquatic beetle can reach a peak acceleration of 100 m s-2 and a top velocity of 100 body lengths per second. Previous studies have suggested that drag-based thrust by their hind legs is responsible for their propulsion1,2,3,4. For the drag-based thrust to be effective, however, the leg stroke velocity must exceed the swimming velocity. Therefore, for fast-swimming whirligigs, it is unlikely that the drag-based thrust is the main source of acceleration5. Here, we demonstrate that lift-based thrust enables the rapid swimming of the whirligigs.