Go Ponding! The World of Aquatic Insects

By Ted Watt Gazette Contributing Writer

Lots of us have waded into our favorite pond or swimming hole on a warm summer day and seen the green frogs leap out from under our feet at the last moment with a startled squeak. You may have seen how the painted turtles swim quietly into deeper water when people arrive and how the great blue heron fishing in the shallows flies off.

But there’s a whole other fascinating pond world right there, under our noses, just waiting to be discovered. It’s the world of aquatic insects. And exploring this world is easy—all you need is an old dish pan or other small tub, a long-handled net and a magnifying glass.

To learn more about these animals, first fill your tub half way with water. Then sweep your net through the shallow water, brush it up against water weeds and cattails and squish it through the bottom mud. Each time you bring it up, wash the contents carefully in the pond water so the tub won’t fill with mud and debris. Then gently empty the net’s contents into the tub and watch for movement. Some aquatic insects bite, so be careful how you handle them.

As you observe your catch you will start to pick out a variety of creatures. One of the most common is the water boatman. Look for a half-inch bug using “oars” to swim through the water. There’s another bug that has oars, but it swims on its back with all six of its legs sticking up towards the surface. Called a backswimmer, it sometimes has red eyes and a white back.

Your collection is also likely to include some intriguing carnivores. The giant water bug, sometimes as long as two inches, is a major predator of other insects. These creatures use their piercing beak to inject enzymes into their prey and then suck out the juices. If you are very lucky you will find a male carrying what look like many tiny beer cans glued to its back. The female deposits her eggs on the male’s back and the male transports them and keeps them safe until hatching.

Another interesting carnivore is the water scorpion, which is almost four inches long and looks like an aquatic combination of the walking stick and praying mantis. Long and skinny, it holds its legs in the prayer position waiting for something to swim within reach. Then it grabs the prey and devours it.

Not to be forgotten is the predaceous diving beetle larva called a water tiger. It vigorously swims through the pondweed searching out prey to grab with its sickle-shaped jaws. It can even eat tadpoles.

Many airborne insects have aquatic larval stages living in ponds; one of the most common is the dragonfly nymph. In addition to walking on its six legs, it has a strategy for making a quick getaway. It has gills inside its abdomen and is constantly circulating fresh water over them to obtain oxygen. When it feels threatened it squeezes its abdomen, shooting water out its rear end, scooting forward by jet propulsion—its own personal jet ski. The dragonfly larva is also a predator—able to catch and munch other insects and even small fish.

Many of these aquatic insects have to get their oxygen from the air and they have ingenious ways of doing this. Some have snorkels, like the mosquito larva. Look for insects with their butts sticking up through the water surface—these are the snorkel-breathers. Other insects carry a bubble of air down under the water with them—like miniature scuba tanks. You know you’ve found these insects when you see the bubbles under their wings or at their hind end.

For help in identifying and learning more about these fascinating creatures, I recommend the book The Golden Guide to Pond Life. You’ll soon discover a whole new world. Happy ponding!

Ted Watt is an environmental educator/naturalist at the Hitchcock Center for the Environment.

Earth Matters, written by staff and associates of the Hitchcock Center for the Environment at 525 South Pleasant St., Amherst, appears every other week. For more information, call 413-256-6006, or write to us.

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