There are certain peculiar types of bugs called ‘Back Swimmers’ (Greater-water Boatman) that can swim upside down. These back-swimmers are also called boat bugs. Although they spend most of their lives in water, they are able to fly long distances. These insects are small, usually 3 to 17 mm (0.13 to .63 inch) in length. Instead of wings they use their legs to swim. They swim on their backs and make use of their hind legs to paddle through the water. These flat ‘paddles’ are ideal for swimming, and are often made even more efficient by a fringe of hairs which runs down each side. This makes a broader surface to push against the water. The insect uses its short front legs for holding the prey.
Back swimmers hold a bubble of air between their wings and body. This air is used for breathing when they are underwater. This lets them stay underwater for as long as six hours. In winter, back swimmers bury themselves in the mud at the bottom of a pond or stream.
They have sharp beaks which they use for stabbing fish and other small water animals and suck out their juices. Back swimmers sometimes even bite human beings.
These creatures belong to Notonectidae family which has in all about 200 species. They are found generally all over the world. They cause great harm to fishes and tadpoles. They deposit their eggs in the plant tissue of pond vegetation.