For small creatures, the surface of the water is not nearly as permeable as it is for us. Water striders glide over it easily using surface tension. And biologists John Gould and Jose Valdez have found that some beetles are able to navigate the film from below and feel great about constantly walking on the ceiling. Scientists describe this behavior in an article published in the journal Ethology, according to Naked science.
Australian Gould accidentally noticed these tiny beetles while working on an expedition in Watagans National Park in New South Wales. He managed to immediately capture the insect moving along the film of water, calmly changing direction, stopping and continuing its course again. And all this is upside down. According to the scientist, in the scientific literature, such behavior has so far been described extremely poorly.
With the support of a colleague from Germany, Jose Valdes, Gould identified the insect as a representative of the order Hydraenidae – small (usually one to three millimeters) aquatic beetles. Scientists believe that the air bubble, which was able to be seen on the abdomen turned up, helps them to stay “on the ceiling”. It presses the insect to the surface film, allowing it to push off with its paws. However, a better understanding of this mechanism will require new studies of the anatomy and morphology of the beetle limbs, as well as their hydrophobic properties. It is possible that the body of the water freak itself is hydrophobic, and the legs are hydrophilic.
The authors believe that such an unusual ability allows the beetles to stay in the water, but keep as far away from local predators that hunt closer to the bottom as possible. Perhaps, in case of danger, insects are able to jump to the opposite side of the surface film and move in the usual way, like the same water striders.