Abstract
We explained the reason why a water strider can be on a water surface according to experimental results. We analyzed force balance of a floating circular cylinder as a leg of a water strider. To check the analysis we investigated experimentally the floating state of the circular cylinder with various diameters and the legs of a water strider. We showed that the surface property of a thin circular cylinder must be hydrophobic to take advantage of surface tension as a lifting force. Function of hydrophobic setae of the leg seems to be for retaining the air layer around the leg for increasing contact angle rather than an increment of length of contact line with water surface.
