by Heather Montgomery, Fandangle Magazine, April 2007

Have you ever watched a dragonfly swoop down to catch a mosquito on the wing? Like a dragon, it is speedy, ferocious and powerful. But it is in water that dragonflies have a magic all their own.

You won’t find an adult dragonfly in water. But if you watch closely, you may see a female swoop over a pond to lay her eggs. A young dragonfly is born from one of those eggs. It becomes a nymph, a teenage dragonfly, and looks like a tiny monster lurking at the bottom of the pond.

Getting Dinner

A baby mosquito wiggles through the water. Suddenly it’s gone. Like a rabbit disappearing into a magician’s hat, it has just vanished. If you were watching through a slow motion camera, you would have seen that, out of nowhere, a hinged brown jaw reached out and grabbed it. The mosquito is whipped away and into the waiting mouth of the dragonfly nymph. Covered in mud and algae, that nymph was so camouflaged no one even noticed it.

When at rest, the nymph’s lower jaw folds up neatly under its head. When a tasty bug swims by, the nymph’s jaw unfolds to snag his dinner. That jaw is half as long as the bug’s body. Imagine if your jaw could stretch as long as your arm!

Catching Its Breath

The dragonfly nymph breathes underwater through its rear-end. Its gills are in a sac near its tail. The nymph sucks water into the sac, absorbs the oxygen and then releases the water. If there is not enough oxygen in the water, a nymph will crawl out of the pond. Like magic, it can start breathing through its skin.

Getting Around

Looking like a six-legged robot, a nymph stalks slowly along a dead plant. Each foot is equipped with nifty hooks that help it hang on. When a large fish comes by, the nymph jets to safety under a log. To activate this jet-power, the nymph squeezes the water out of its gill sac, shooting forward several times its body length. If you have ever let go of an untied balloon, you have seen this kind of jet action at work.

Growing Up

Even the way a dragonfly nymph grows up is extraordinary. It does not become a cocoon like a butterfly. Instead, it sheds its own skeleton in order to grow. This skeleton, called an “exoskeleton,” is on the outside of its body, so it looks like skin. Just like you get rid of clothes that are too small, it has to get rid of its old skeleton.

A nymph sheds many times while it is still in the water. Before its last shed, it pulls itself all the way up a plant stem and breaks out into the fresh air. Emerging from the old skeleton, it is soft and white. It must wait patiently for its body to harden. Then magically, it transforms into a beautiful, winged dragon of the sky.

References

Bland, Roger G. and H.E. Jaques. 1978. How to Know the Insects. Dubuque, Iowa: Wm. C. Brown Company.

Evans, Howard E. 1984. Insect Biology. Reading, Massachusetts: Addison-Wesley.

Voshell, J. Reese. 2002. A Guide to Common Freshwater Invertebrates of North America. Granville, OH: McDonald and Woodward.