The insect world may largely go unnoticed in most people’s day-to-day lives, but these tiny creatures are capable of superpowers we can only dream of. Across the insect world are species that can leap hundreds of times their own body length, lift objects thousands of times their own weight, and even walk on water.
What types of bugs walk on water, and why?
If you’ve ever spent time around a pond or lake, you’ll probably have noticed dozens of tiny critters skimming the surface of the water. Several marine insect species get around, not by swimming, but by walking over the surface of the water.
Most of these bugs belong to the family Gerridae, a group more commonly known as the water striders. Water striders are found in freshwater habitats throughout North America, where they skate around the surface of the water of their long legs to feast on other bugs. These predatory insects have a variety of adaptations that make them fierce hunters, and they can move at speeds of up to 1.5m per second.
Fishing spiders are another type of bug with the ability to walk on water and, like water striders, are often found around ponds and lakes. These arachnids also hunt aquatic insects, and can even catch small fish as they skim the surface of the water.
Clearly, this special ability is a great asset for predatory marine insects, but how do they do it? Insects that are able to walk on water can do so with the help of physics and a few special adaptations of their own.
What is surface tension?
For water-walking insects, surface tension is key. Without it, they would sink just as quickly as you do – but what exactly is surface tension, and how to bugs use it?
Water molecules are more strongly attracted to one another than they are to air molecules. This causes them to draw cling together tightly in a body of water, due to cohesion. The molecules at the surface of the water do not have water molecules on all sides of them and, as a result, are more strongly attracted to the water molecules between them.
This creates an inward force at the surface which forms a ‘film,’ causing the water to behave as though it were covered with a thin membrane. This phenomenon is known as surface tension.
How do insects use surface tension?
Certain insect and spider species are able to use surface tension to their advantage. Their tiny weight is not enough to overcome the force of surface tension, so they don’t break the surface of the water when they stand on it. Rather, their feet create dimples or indentations in the surface, which then springs back to propel the insect forward.
This allows them to scoot quickly over the surface of ponds, lakes, and rivers in their hunt for prey. However, surface tension isn’t the only thing that’s required to enable them to do this. Bugs that walk on water also have a few other key adaptations, without which they wouldn’t be able to perform this unique skill.
What other adaptations allow insects to walk on water?
How do water striders walk on water? We’ve covered the basics of surface tension, but what else do water-walking bugs have that allows them to do what they do?
Water striders have hairy bodies
The secret weapon of any insect that walks on water is in its body hair. Water striders and fishing spiders both have legs and bodies that are covered in a thick layer of tiny hairs. These hairs trap air in between them, repelling water and helping them keep the bugs afloat. If the insect were to get wet through, it wouldn’t be able to walk on the surface of the water anymore.
Water striders have long legs
Another key adaptation of the water strider is its legs. Like all insects, these bugs have six legs. However, the middle and hind legs are much longer than the front two, and these are used to propel the water strider over the water’s surface. Like their bodies, the water strider’s legs are covered in a layer of hairs that repel water. This creates a tiny air cushion between the bug’s feet and the water, which allows them to glide over the surface.
What other animals can walk on water?
The diminutive size of certain marine bugs plays a big part in their ability to walk on water, as their weight is small enough to be supported almost entirely by surface tension.
However, it’s not only insects that have mastered the skill of walking on water. Certain species of reptile, such as the Basilisk Lizard, also possess this talent.
The Basilisk Lizard escapes predators by dropping from its home in the trees onto the river below, before running off over the surface of the water. It is able to do this with the help of its long, webbed toes, which trap pockets of air beneath them and act as a buoyancy aid. This only works while the lizard is running fast, however – as soon as it starts to slow down, it breaks the surface of the water and sinks.
The Brazilian Pygmy Gecko can also walk on water because, like insects, it has a hydrophobic (water-repelling) body and very small size. This enables it to walk over the surface of the water without breaking the surface.
Insects are capable of things we humans can only dream of, superpowered skills that have come about over thousands of years of adaptation. One such talent is the ability to walk on water, a trick that certain species of insect and spider use to capture and kill prey. By making use of the phenomenon of surface tension, and a few unique features of their own, these bugs are able to perform the impossible and walk across the surface of ponds, lakes, and rivers without ever getting wet!