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A Wilder View: How bugs can glide across the water

Skating Bugs
Posted at 11:41 AM, Dec 14, 2022

MISSOULA - With winter here you may be trading in your sneakers for a pair of ice skates to glide atop a frozen pond.

But if that pond wasn’t frozen those skates wouldn’t do you any good. But this wouldn't be the case if you were an insect.

So why can some bugs glide across the water as if they were ice skating?

For people, the best way for us to glide across the water is to wait until it’s frozen.

But some bugs can move smoothly on the surface of the water as if they were skating on it.

To figure out why they can skate on water, let’s get down to the molecular level and talk about atoms.

Everything in the universe is made up of atoms, and atoms are made up of parts called neutrons, protons, and electrons. The protons have a positive charge while the electrons have a negative charge. Opposite charges attract and similar charges repel each other.

Water molecules are more attracted to each other than they are to other materials, so they generate a force to stay together called surface tension.

It's the reason why water forms drops on a surface. You can see this if you put a drop of water on a table. The molecules of water in that drop will actually stick together to create a dome shape instead of just being completely flat to the table.

Picture a water molecule as a magnet. It has a positive and negative side. When pulling a magnet off a fridge some force is needed. And for water the force it takes to break through the surface is even weaker than a fridge magnet.

If the force of an insect’s foot on the water is less than the surface tension of the water, then they will float. While, if the force of their foot is greater than the surface tension, then they will sink.

What determines the amount of force the foot produces is from the weight of the insect and its foot shape. If the foot is flat and wide, the weight is dispersed across a greater surface area and the force is less than if the foot were sharp and thin.

So, the reason some insects can walk on water is by being super small, very light, and having the ability to spread out their weight.

Therefore, they are not exerting enough force to break the connections that hold water molecules together and thus have the incredible ability to glide on top of the water.

Small insects, spiders -- and even the basilisk lizard -- can take advantage of these traits. Scientists are studying the legs of all these species and water striders in particular in hopes of making materials that easily repel water and help objects move faster over water.