|Striding across the pond - REK|
Each of its three pair of legs serve a different function. The front pair are equipped with claws in the middle like a preying mantis, allowing them to grab and puncture their prey. The middle pair serves as oars, quickly propelling them across the water while the longer back legs support their weight and act as rudders. When they sense vibrations or waves from a struggling insect, they can turn rapidly and attack as fast as one meter a second.
|Responding to a twig thrown in the water - REK|
"At liquid-air interfaces, surface tension results from the greater attraction of liquid molecules to each other (due to cohesion) than to the molecules in the air (due to adhesion). The net effect is an inward force at its surface that causes the liquid to behave as if its surface were covered with a stretched elastic membrane. Thus, the surface becomes under tension from the imbalanced forces, which is probably where the term "surface tension" came from." WikipediaThe other factor is the cluster of tiny hydrophobic hairs covering their body, over 1,000 microhairs per millimeter. On the legs, they keep the strider on top of the water, riding on the surface tension. The hairs on the body prevent wetting even from rain, that otherwise would weigh them down.
|The elastic surface tension is stretched under each leg - Stan Lupo|
|Strider Astride - Stavros Markopoulos CC|
High speed video of water striders and surface tension.