So-called water spiders aren’t spiders at all but insects specially evolved to walk on water.

There are 1,700 species of these water striders, which have existed on Earth for millions of years.

If you’ve ever wondered how they skate so effortlessly across a pond without falling in, the answer is surface tension—and their very specific adaptation to it.

Water molecules, as we’ve discussed on prior EarthDates, bond together tightly, especially where water meets air. This creates a membrane-like surface that the water skaters take advantage of.

Their long legs are useless on land. But they’re equipped with thousands of microscopic hairs that trap air in nanogrooves. The air repels water, keeping the surface tension intact though the insect is moving across it.

And move they do, at up to 100 body lengths a second—the equivalent of a human traveling at 400 miles an hour.

They use their incredible speed to catch prey that also live in this unique environment: other insects, small spiders, and, their favorite food, mosquito larvae.

This makes water striders a beneficial insect in controlling mosquito populations.

In ideal conditions, water skaters can live up to a year, hatching new eggs every two weeks. And when their ponds are drying up, they’re able to spawn a new generation with wings, to fly off to find another pond to skate on.