Inside some park ponds, if you look closely, you can definitely find this creature: the water shrew. I remember seeing this bug as a child and thinking it was amazing because it could swim like skating on the water. It has many other names: water horse, water spider, jellyfish, water bench, water mosquito, water grasshopper, fire fork, water tank. There are also netizens who call it "Lingbo Fairy", have you ever seen it?
The water shrew is an aquatic hemiptera insect of the family Shrews that inhabit still water or slow flowing streams.
Adult water shrews are 8 to 20 mm long, dark brown, and the head is triangular and slightly longer. The body is small to large, elongated or oval. The muzzle is slightly longer, divided into 3 segments, the 2nd segment is the longest; the antennae are filamentous, 4 segments, protruding from the front of the head. The forebrain is elongated, the back is mostly dark and dull, there are no distinct spots, the forewings are leathery, and there is no membranous part.
The water shrew has 3 pairs of feet, the forefoot is short, the middle and hind feet are very long, stretched out in all directions, and the hindfoot leg segment extends farther across the end of the abdomen. The forefoot is significantly shorter. The tarsal segment has 2 segments, the end of the terminal segment splits into 2 leaves, and a pair of claws are born at the base of the fissure. The back pair of legs can be used to control the direction of sliding, and the middle pair of legs is the driving leg, which is particularly long. The front pair of legs is relatively short and is only used for hunting.
Water mole feeds on the bodily fluids of small insects, dead fish or insects that fall into the water. Through the very sensitive organs on their legs they can feel the struggle of insects falling into the water. By sliding a pair of legs in the middle of them they can move on the water to reach a speed of 1.5 m / s, in addition they can do 30 to 40 cm high and far jumps. When eating, the mouth is smoked in a tubular shape.
Their habitats generally live in still water, often gathering in groups on the surface of the water, which can be seen in parts of southern China over the years. Some species also live exclusively in running water.
Why can the water weed float on the surface of the water without sinking? Researchers have found that the legs of the water shrew can drain 300 times the amount of water in its body volume, which is why this insect has extraordinary buoyancy. One long leg of the water weasel can support 15 times the weight of the body on the surface of the water without sinking. The tension between the grease layer and the surface of the water is not so buoyant. Water shrews glide across the water at great speed to catch prey. It can glide 100 times the length of its body every second on the surface of the water, which is equivalent to a person 1.8 meters tall swimming at 400 miles per hour.
The reason why the water mole can float on the surface of the water, the special micro and nano structure of its legs is the real reason, Jiang Lei led the research team under the high-power microscope found that there are thousands of multi-layered micron size bristles arranged in the same direction on the legs of the water mole. The diameter of human hair is about 80-100 microns, and these needle-like micron bristles are less than 3 microns in diameter, forming spiral-shaped nanostructured grooves on the surface, and the bubbles adsorbed in the grooves form air cushions, so that the water mole can glide freely on the surface of the water without getting the legs wet. The hairy legs of the water shrew are able to draw 4 mm long ripples on the surface of the water at a time.
It is precisely by using the special micro-nano structure of its legs that the air is effectively adsorbed in the gaps of these micron bristles and spiral-shaped nano grooves of the same orientation, forming a stable air film on its surface, hindering the infiltration of water droplets, and macroscopically showing the superhydrophobic characteristics of the water weasel's legs. It is this super load capacity that allows the water to move freely on the surface of the water, even in storms and rapidly flowing water.
The hydrophobicity of the bristles on the legs of the water is similar to the hairs on the back of a duck, but the general hydrophobicity (or water resistance) may cause the insect to stay on the surface for a while, and the slightest touch or disturbance can upset this balance. However, the air cushions formed between the legs and the surface of the water allow them to walk or run quickly and steadily on the surface of the water.