Probably, many have observed such a picture, when a large dark-colored beetle with an oval body bordered by a yellow strip along the pectoral shields and elytra rises from the depths of the reservoir to the surface. This is an insect belonging to the aquatic order Coleoptera, the swimming beetle. The photo shows how bright and attractive it can be.
There are more than four thousand species in the world, and about three hundred species in fourteen territories in Russia. Swimming beetles inhabit deep bodies of water with stagnant water, rich in vegetation and animals. The swimmer is a predator. Ponds with a sparse population will not be able to provide the beetles with an adequate supply of food. Since the swimmer is the most insatiable aquatic predator, it is not limited to eating small aquatic animals, sometimes it also attacks fish or newts. May attack creatures larger than himself.
The beetle itself is unattractive for predatory animals, as it has impressive arguments against those who want to profit from it. In case of danger, the swimmer from under the chest shield releases a fountain of whitish caustic liquid, in addition, color helps it. For waterfowl, the beetle is hardly noticeable.
Periodically, the swimming beetle emerges from the water, exposingthe back of his body, and hangs in that position for a while. Why does he write such somersaults? The fact is that his respiratory system is designed in such a way that oxygen enters through the spiracle located at the end of the abdomen. During the rise to the surface, the air valve opens, and so the beetle receives a portion of oxygen. Soon, the swimmer again plunges into the water, taking with him an air bubble under the elytra. The beetle needs it not so much as a supply of air, but as a hydrostatic device. Having exhausted the oxygen reserve, the swimmer rises to the surface of the water again. As a rule, the swimming beetle emerges every eight minutes.
Since the body of the beetle is lighter than water, the swimmer floats to the surface without any effort (the water simply pushes it out), but diving requires considerable effort and intense movements. To stay under water, the beetle is forced to cling to any water objects - algae, sticks, stones, and so on. His front limbs, equipped with sharp hooks, help him to catch on.
Male have suction discs on the front pair of limbs. They help to attach to objects with a smooth surface, and also serve as a kind of device for capturing the female during mating. These suckers are believed to work with a sticky, water-insoluble liquid. Females do not have suckers, so their elytra are more furrowed, although females are sometimes found with smooth elytra.
Thanks to well-developed wings, the beetle is able toleave their body of water and fly inland for considerable distances. The swimming beetle is a rather strong insect. In the water, it is helped to move by an oar-shaped, overgrown with hairs, hind pair of limbs. Like a rower, a swimmer overcomes the density of water and sometimes develops a speed at which it is able to move faster than some fish.
By drilling holes in plants, the female lays eggs, from which larvae appear, and at the end of her development, the larva crawls onto land and pupates. A few weeks later, a swimming beetle emerges from the chrysalis, returns to the water, and life continues.
