Six-Legged Swimmers

by Beverly J. Letchworth
photography by Jim Rathert

Bugs love water, too!

Hot and tired from hiking through the woods, you come to a slow-moving stream. You take off your shoes and socks and dangle your feet in the cool water.

You notice little fish swimming about. Nice, silvery fish. But hey, what's this! There's bugs in here, too!

You see a gang of black ones going around in circles, and some long-legged things.

A bug as big as a quarter hangs head down, and an even bigger one has a pointed face.

Bugs in a stream? What's going on?

Actually many insects live in streams, lakes and ponds. Some of them have shapes and movements that make them easy to identify, like those long-legged things. You just have to know what to look for.

Aquatic insects are fun to watch, study closely and even photograph, but they also are the base of a food pyramid that includes fish and the animals that eat fish, including humans. A healthy stream, pond or lake will have lots of insects. Stream Team volunteers count bugs in streams in order to assess the quality of the water.

Next time you're out hiking or exploring and come across a slow stream, settle down beside the stream, keep your eyes open and watch for water insects.

Zigzag Is The Thing
If you see some bugs wildly jerking here and there that have a color pattern that looks like fine crossbands, you've spotted water boatmen. Their middle and hind legs are flat and act as paddles.

They have trouble staying underwater. Oops, up they come. They usually need to hold onto something like a plant or stick to keep themselves submerged. While underwater, they scoop up algae and decaying plant and animal matter to eat.

Do The Backstroke
Backswimmers are torpedo-shaped insects that swim upside down. They're master predators and catch their victims by quietly swimming underneath them.

If danger comes their way, they submerge and hide. They can hold enough air in their abdominal pockets that they can stay underwater for six hours. Sometimes they're called water bees or water wasps, because they can bite a hand or leg in the water.

Monster, Ho
The big bug with the pointed face is a ferocious water bug. The largest of the true bugs, it can reach almost 2.5 inches long and be an inch wide. This bug is so big it eats tadpoles, fish and salamanders.

Watch for the giant water bug crawling around on the stream bottom. You also may see it rising to the top of the water, where it sticks out two breathing tubes for more air.

Man Those Oars
Head down, tummy up, is a common position for the predaceous diving beetle. Look for it just under the water surface as it hangs head down with the tip of its abdomen sticking up in the air. In this way, it can trap air in its special chambers.

When this beetle swims, it works its hind legs like oars. Other beetles move their legs one and then the other. It eats insects and prey larger than itself, such as small fish and tadpoles, with its sickle-shaped jaws.

Let's Skate
Those long-legged things are water striders. They glide and jump about on the surface film of the water. With long legs spread out, they look as though they're skating. In fact, in Canada they're called "skaters," and in Texas they're often called "Jesus bugs" because they walk on water. Sometimes you see them lying quietly, too. Perhaps they're resting after performing all those figure 8s.

Water striders are predaceous insects, which means they prey on other creatures. They eat small aquatic insects and land insects that might fall into the water.

Circle Right, Circle Left
That gang of black bugs going around and around are whirligig beetles.

Watch for swarms of them as they swim in quick, little circles on top of the water. They're restless insects and are as much at home below water as on the surface.

They can watch for enemies above the water and insect prey below at the same time with their two pairs of eyes.

Watch for these six, six-legged swimmers next time you're by a stream. You'll be able to see some of them on ponds and lakes, too. Next time you see them, you'll have fun knowing what they are.