The waterlily beetle exploits properties of the interface where air and water meet to glide quickly across the surface of ponds.

Credit: Mattias Lanas

Manu Prakash at Stanford University in California and his colleagues filmed waterlily beetles (Galerucella nymphaeae; pictured) at 3,000 frames per second to characterize the mechanics of the insect's unusual mode of flight on the two-dimensional surface. They found that the claws on the beetles' legs remain submerged during flight, anchoring the insects to the water.

Keeping four of their six legs on the water, the insects use the fluid's surface tension to support their body weight and move by flapping their hind wings, cruising along the water's surface at speeds of up to half a metre per second. Moving any faster would render them airborne, because the ripples they produced on the water would release their anchors.

J. Exp. Biol. 219, 752–766 (2016)