Skimming the surface

With a mind-boggling ability to walk on pools, rivers and even the ocean, water skaters are Nature’s great survivors, says Ian Morton

- Ian Morton

THEY live where air and water meet. Appearing on stream, pool, lake and slow-moving river, where they scavenge the bodies of the dying and the dead, they are the neuston, a category of insect classified in 1917 by Swedish limnologist Einar Naumann. Their appearance and features—let alone their name—might suggest mysterious aliens in a science-fiction television series, but they are both real and truly remarkable.

In their most familiar form, we know them as water skaters, water skimmers, water striders, water skippers or pond skaters; in southern states of the US, they are irreverently known as Jesus bugs. They seem to be the least feasible of life forms, existing in sheer defiance of the concept of material reality: if you walk on water, you sink—but not this neuston. Ugly, skinny and long-legged Gerris lacustris may be, but the common water skater conquers the laws of Nature. It does this by growing thousands of tiny, grooved, wax-covered hairs that prevent the ingress of water, an attribute described by science as epipleustonic.

The insect’s short front legs are employed for holding prey, which its powerful mouthparts pierce and suck. Its other four legs spread its slight weight and use the surface tension of water, that invisible layer where hydrogen atoms in the H2O molecules create a web of attachment, causing a net inward force that resists surface breakage in one of the most extraordinary dynamic balances to be found in the natural world. The legs are so buoyant that they can sustain 15 times the insect’s weight, even in rainy or choppy conditions.