The respiratory system of insects is made up of small tubes, called tracheoles, which are connected to the outside of the body. Tracheoles are filled with liquids, through which gaseous exchange takes place.
The water beetle stores the oxygen under the elytra, forming an air chamber in a place where there are numerous tracheoles. The water beetle resists about to 15 minutes in apnea, after which the air reserve is regularly renewed.
The larvae of friganea have feathery gills on the sides of their body, inside a protective case. The case is open on the sides, to guarantee the flow of water and increase gaseous exchanges.
There are those who walk underwater…
There are species of insects that move on the bottom of the water or among the submerged vegetation using not very specialized limbs. The water scorpion has the first pair of limbs transformed into claws. has two pairs of wings that are unusable due to regression of the wing muscles.
…and those who skate…
The gerrids cannot swim or dive; they skate keeping the median and hind legs very spaced apart, moreover they retract the nails of the tarsi so that they don’t pierce the surface of the water. They produce an oily secretion which makes them waterproof.
…there are those who swim…
Some aquatic insects have developed particular adaptations to swimming, such as a hydrodynamic body and the last pair of hind legs flattened (swimming legs) and used as oars. All families of water beetles are excellent swimmers thanks to the flattened and hydrodynamic body. The third pair of legs is covered with hydrophobic swimming hairs, used as oars. The notonectidae is very agile in the water and moves hanging under the surface of the water.
…and those who walk on the surface of the water.
Some species belonging to the family of Gerridae, Veliidae and Hydrometridae, move skating on the surface of the water thanks to their lightness and long legs. The hydrometer has a narrow body, covered, in the ventral part, by a very short adherent, water-repellent and impermeable pubescence. It moves along the edges of ponds and puddles, walking slowly on its threadlike legs.
THE METAMORPHOSIS OF DAMSELFLY
The mating of the damselfly is somewhat extravagant: the male and the female curve their abdomens to assume the characteristic heart shape. This happens because there is no correspondence between the position of the sexual organs of the male (located in the second abdominal segment) and of the female (located in the eighth segment of the abdomen). Once fertilization occurred, the female lays her eggs by dropping them into the water. After about a month, a larva (nymph) emerges from the egg, from which the wings will slowly develop. Once the nymph is fully grown, it separates from the old cuticle allowing the adult to emerge in it’s full form.