The hydrometra, the gerridae, the mosquitoes and other very light insect species manage to walk on water without sinking, exploiting the surface tension. This property of water is the consequence of the action of the cohesive force between molecules: while the molecules inside the liquid are attracted to all parts by other molecules, those placed on the surface are attracted only by the underlying molecules, thus being recalled downward.

The surface tension makes the liquids enclosed by an elastic membrane seem, just think of the drops and the way they are formed. Lighter insects use this elastic property to walk on the surface of the water. Looking closely, in fact, they seem to skate and we see that the surface of the liquid is curved downwards at the legs.

In addition, many insects that walk on water are provided with surface hair covered with oils, that is hydrophobic substances that repel water and allow the terminal part of the legs, consisting of tarsus and pretarso, not to sink.