September 28, 2005

Secrets of Water-Walking Insects Revealed

LONDON -- Scientists said on Wednesday they have discovered how tiny insects manage to walk on water and propel themselves across the slippery slopes of ponds and puddles.

Although the surfaces of the water look flat to the human eye, for the tiny creatures they appear as huge walls of water called menisci that must be climbed to get to where they want to go.

John Bush and David Hu at the Massachusetts Institute of Technology (MIT) in the United States used a high-speed video to show exactly how three species of gravity-defying insects do it.

"The ability to climb menisci is a skill exploited by water-walking insects as they seek land in order to lay eggs or avoid predators," they said in a report in the science journal Nature.

Millimeter-sized insects cannot scale the walls of water with their usual movements so they assume a rigid body position and form dimples on the surface of the water which create forces that suck them up the slope.

The scientists compared the action to water being sucked up a thin tube by the force of its own surface tension.

"Meniscus climbing is an unusual means of propulsion in that the insect propels itself in a quasi-static configuration, without moving its appendages," the researchers added.