Robot Helps Show That Water Striders "Row" on H20

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But Bush and his colleagues were able to disprove this theory by using high-speed video, particle-tracking studies, and dyed water to examine water strider movements more closely.

The results of this research, published this week in the scientific journal Nature, show that with each stroke of their middle legs water striders create hidden, underwater currents. These swirling vortices carry enough momentum to propel the insect at high speed.

Bush said: "This is how rowboats work. The oar goes in the water and scoops fluid backwards. Water striders do the same, except they don't break the surface. The dimples they create act like the blades on an oar."

Michael Dickinson, a professor of bioengineering, added: "It is the rearwards motion of these vortices, and not the surface waves, that propel the animal forwards."

Fast Movers

Water striders can cover 100 body lengths in one second. This is equivalent to a six-foot-tall (1.8-meter-tall) human swimming at speeds of over 400 miles per hour (644 kilometers per hour), a velocity faster than many jet aircraft.

Basing its design on their observations, the researchers built a working replica of the insect. Like its inspiration, Robostrider creates surface ripples and hidden vortices as it moves across the water.

Fashioned from lightweight aluminum, Bush admits this mechanical model doesn't quite match the grace and speed of its natural counterpart, and travels only half a body length per stroke.

He added: "It's fair to say our Robostrider isn't nearly as elegant as the real thing, but it does work."

Having solved the mystery of the water-walking Jesus bug, Bush is turning his attention to locomotion in other waterborne creatures.

He said: "It's a fascinating world, completely dominated by surface tension. People have done a lot of work on birds and fish, but this is in between—neither flying nor swimming."

So take a good look at those other water bugs out there. Their secret could soon be out.

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