Water striders using water surface tension when mating. Photo by Markus Gayda
The family Gerridae contains insects commonly known as water striders, water bugs, magic bugs, pond skaters, skaters, skimmers, water scooters, water skaters, water skeeters, water skimmers, water skippers or Jesus bugs. There are around 500 known species, commonly placed in around 60 genera.
Water striders can vary in length from 1.6 mm (tiny species from the genus Rheumatobates) to 36 mm. Similarly, their body shape ranges from slender and elongate to almost completely round. One common feature is their elongated legs (only the first pair is short and stubby) which the animals use for moving over the water surface. The body and legs are covered with tiny hairs. The head is usually elongated in front of the eyes to form a rostrum. Similar to other bug groups (such as Pyrrhocoridae), the development of wings can vary significantly within the same population. The population consists mostly of specimens with undeveloped or poorly developed wings. However, a small number of individuals have fully developed wings which they use for colonizing new habitats and forming new populations.
These are predatory insects which rely on surface tension to walk on top of water. They live on the surface of ponds, slow streams, marshes, and other quiet waters. There they hunt for insects and other small invertebrates on top of or directly below surface using their strong forelegs which end with claws. They can move very quickly, up to 1.5 m/s. They paddle forward with the middle pair of their legs, using fore- and hind legs as a rudder.
Five species of Halobates sea skaters are the only insects that have successfully colonized open ocean habitats.
Nature of the hydrophobic legs
Water striders can stand effortlessly on water due to their non-wetting legs.
Writing in Nature, biophysicists Xuefeng Cao and Lei Jiang demonstrated that the water resistance of the legs is due to the "special hierarchical structure of the legs, which are covered by large numbers of oriented tiny hairs (microsetae) with fine nanogrooves". They go on to demonstrate that the water resistance is due more to this physical structure than the chemical properties of the wax coating of the legs.