Lively, light, the gyrins crisscross the surface of fresh water with their metallic shine, in a dizzying ballet of speed.
The speedboat of fresh water
They move at full speed on open waters, gather peacefully in the plants and dive to escape from predators. They live between air and water. Gyrins, small beetles of aquatic environments, hold the speed record of floating insects, with their 4 back legs they propel their 12 grams, in random but precise curves, avoiding for sure any collision. These insects of a few millimeters, 6 at most, with varied dark colors, have 3 genera and many species, all of the family Gyrinidae.
A life between air and water
Floating on water, Gyrinids breathe oxygen from the air, like any terrestrial insect. Their tracheas carry gases to all their organs. But at the slightest alert, they dive under water, take refuge in the grass beds, do not move any more. Do they hold their breath, do they have a snorkel like the nephrops or the eristalus? No, just before diving, with the tip of their abdomen, they capture a bubble of air, a precious reserve that ensures them to go back up when the danger has passed. Their daily activities, such as hunting, take place on the surface.
A predator on the water mirror
Untiring, the Gyrins watch and survey their territory, a vast and totally flat area. With their antennae on the surface of the water, they pick up the vibrations of insects, spiders, shipwrecked airborne creatures, desperately struggling to escape drowning. Spotted, they are seized by the front legs, ingested by a crushing mouth apparatus. And if no aerial prey presents itself, mosquito larvae, small crustaceans, will at some point pass near the surface, within reach of the paws of a hungry Gyrin.
Eyes for water, eyes for air
Between air and water, how can the Gyrin switch so quickly from an aerial hunt to an aquatic hunt? How does it spot a predator from the depths or diving from the sky? Its adaptation is simple, obvious: its eyes are divided into two parts, one for aerial vision, the other for underwater vision. To surprise him becomes a real challenge. And to escape him too. Especially since its adaptation to swimming is also remarkable.
Swimmers and trainers
The spectacle of the Gyrins spinning, twirling, so fast that the eyes cannot follow them, announces long afternoons of contemplation at the edge of the pond. Their back legs are said to be swimming, equipped with bristles they offer a powerful support on the water, activate vigorously several tens of times per second, and propel the Gyrin at high speed. The oars at rest are folded in a special box, so the small carinated and oiled body of the beetle finishes its slide with fluidity...
Males and females, aquatic meetings
Following a terrestrial hibernation, under the stones of the banks, the couples of Gyrins are formed, the females will lay about thirty eggs on the plants. These eggs will give birth to a larva which, as with all beetles, does not look like the adult. 15 mm long, whitish, thin, it crawls on the bottom or wriggles in the water, feeding on small animals. Its breathing is aquatic, abdominal feathery tracheal gills ensure the gas exchanges of its organism. After three larval stages a terrestrial nymph is formed, the metamorphosis will give birth to the Gyrins whirling on the water.
They float, spin on the water at full speed, they dive and swim, their young breathe under water... And moreover they can fly. Their wings spread, they leave to discover new environments, with calm waters, vegetated banks, with large areas to glide without hindrance.
