The surface of a pond, river, puddle and any other body of water can be safely called a unique ecological niche. The fact is that on the surface of these reservoirs are concentrated two completely different environments for living organisms - water and air.
A bit of physics
Before revealing the secret of water striders, you need to remember some of the basics of the physical properties of water. As you know, air and water media are separated by a special film of surface tension. At the boundary of two phases, the forces of attraction arising between water molecules are not balanced, i.e. the sum of the forces that act downward turns out to be many times greater than the sum of the forces that act upward. Due to this, the density of water on the surface of the reservoir is slightly higher than in the main water layer.
But that's not all! Molecules, tending downward, lead to the emergence of a kind of elastic membrane, which is capable of supporting objects with a density higher than this on the surface of the water. However, there is one condition: these objects must be dry. If they are moistened, they will independently attract water molecules to themselves, which will disrupt the structure of the surface film.
It is curious that these amazing physical properties of the water film are used for their own purposes by various living organisms. It is worth moving from physics to zoology. As you know, life on the border of two habitats has a very noticeable advantage. The most famous inhabitants of the surfaces of reservoirs are, of course, water striders.
Who are water striders?
These are small insects from the Hemiptera order. Simply put, these are bedbugs. Like their relatives, water striders are equipped with a piercing-sucking mouth apparatus (proboscis), which allows you to inject special substances into the body of its prey that paralyze and decompose its tissues. This is necessary in order to suck the ready-made "broth" out of the victim.
Water striders are predatory creatures. Their main food is insects that have accidentally fallen to the surface of the water. If the future lunch is large enough in size, then several water striders can enjoy it at once. However, these creatures prefer to hunt and feed alone.
How does a water strider stay on the water?
This simple ability of water striders is explained by the above-described physical properties of water. The so-called surface tension force is to blame. If we briefly retell the essence of this "trick", we will get the following: in the boundary layer between the air and the water column there are water molecules, on which from below (from the depths) a force acts several times greater than from above. Because of this, a kind of thinnest membrane forms on the surface of the water. It is she who holds the water strider, which happily conducts its life.
