Air Show

by Joan Banks

Millions of micro-organisms and other tiny life forms supply the world with the right amount of...



n the summer, there's an air show over my pond. The fliers dip and dive and narrowly miss having mid-air collisions. They hover and somersault. They even fly backward.

The stunt fliers aren't airplanes or helicopters. They're insects called dragonflies. Neon green and blue bodies of green darners zip here and there over the pond. Twelve-spotted skimmers look like flying checkerboards with three dark spots on each wing. Dragonfly wings are made for aerial acrobatics and can work together or separately to do stunts.

I try to sneak up on one when it lands. No way! Its eyes are built to see the slightest movement. A human eye has one lens; a dragonfly's eye has up to 30,000 facets, or surfaces. The facets wrap around its head so the speedy insect can see where it has been as well as where it's going. Wouldn't that be handy?

Some common dragonflies have been clocked at speeds of 5H miles per hour, and they can fly even faster in bursts of speed.

Colorful dragonflies, like this green darner dragonfly, are harmless and are found throughout Missouri. Has one ever landed on you?

Jim Rathert photographs

Sometimes you'll see two dragonflies attached to one another in flight, forming a circle or a heart. They're mating. The male often stays with the female until she lays the eggs. He keeps the other males away.

Some dragonflies bury their eggs in the bottom of ponds or streams. The twelve-spotted skimmer often drops her eggs into the water. The green darner makes slits in the stems of underwater plants and lays an egg in each slit.

From the eggs come nymphs, the dragonfly stage between egg and adult. Dragonfly nymphs live underwater and breathe through gills located in a gill chamber inside the abdomen. The gills let oxygen from the water pass into the insect and carbon dioxide pass out.

As the nymph grows, its exoskeleton, or shell, becomes too small. It sheds its exoskeleton seven to 14 times before it reaches adulthood. Dragonflies spend from a few months to four years or more as nymphs.

Try, Try Again I wanted to see a nymph for myself, so in April I headed down to the pond. I retrieved a slimy tree limb from the water that looked as if it had been there since the summer before, when dragonflies laid their eggs. Maybe I would find a nymph there.

A snail clung to the wet stick, and something long scurried under a piece of loose bark. I pulled away the bark and studied the little critter. It had three flat fins, or gill plates, at its tail end that told me it was a damselfly nymph--a close relative, but not a dragonfly.

I put the limb and damselfly back in the water and scooped through the muck on the bottom of the pond with a kitchen strainer. When the water drained through the strainer, I was left with some soggy leaves, some rocks and several critters. I dumped them into a shallow pan.

Like other insects, the bodies of dragonflies and their nymphs are divided into three parts: head, thorax and abdomen. The critters I'd found were definitely insects. They were about 1 inch long with oval-shaped abdomens, and they looked like the pictures I'd seen of dragonfly nymphs.

I put some pond silt in the bottom of the pan. When disturbed, a dragonfly nymph contracts the walls of its gill chamber and shoots water out the tail end of its abdomen. I couldn't see this, but I saw the result: The nymph jetted forward, leaving a trail in the silt. This "jet" action was a sure sign that this time I had found dragonflies, not damselflies.

Dinner Is Served The nymphs were a brown color with darker markings. They blended well with the pond silt. In fact, when left for a while, they became kind of fuzzy with it. I released them into the pond, and they sank back into the muck at the bottom.

This camouflage hides them from their predators--fish and other insects. It also helps them surprise their own prey. When an insect or tadpole happens by, the lower lip of the nymph shoots out and grabs it.

This lower lip is pretty amazing. First of all, when it's stretched out, it's almost as long as the nymph's foreleg. That's some lip! At its tip is a set of grasping jaws. The lip draws back and delivers the dinner to the waiting mouth of the nymph. The lip serves as sort of a table while the nymph eats--just in case any crumbs fall. When the dragonfly is waiting for prey, the lip is folded neatly beneath its head.

Nymphs have healthy appetites. One scientist reported that a nymph ate 60 mosquito larvae in 10 minutes.

When the nymph is fully developed, it will climb up a stick or post or onto a rock above water and split out of its exoskeleton. If you look in dragonfly territory, you may find a discarded skin. This last molt is a dangerous time for a dragonfly because it must rest for an hour or so to dry its new wings. Unable to fly or swim, it is helpless. To be on the safe side, most nymphs crawl out of the water at night or early in the morning when the birds are sleeping. Birds, frogs, toads and other dragonflies are its worst enemies.

Once the dragonfly takes to wing, it's safe from most predators, but not all. Insect-eating birds, such as flycatchers, and other dragonflies may gobble them, and some people in parts of Asia dine on them the way we eat shrimp.

Fast Food Most people like fast food, and so do dragonflies. That doesn't mean they like to chow down on French fries or a burger to go--flying insects are more to its taste.

Nymphs have a strong, extendible lip they use to catch and eat insects, small minnows and other aquatic species.

David Besenger illustrations

The nymph uses its lip to gather food, but the adult uses its legs. It gathers its legs up like a basket and scoops for its dinner. Then using its sharp teeth, it cuts its prey into bite-sized pieces. And all of this while it's in the air!

Adults only live for about 30 days. But during that time, each will eat thousands of insects. Because they eat so many mosquitoes, some people call dragonflies "mosquito hawks."

They have other names, too. Scientists put them in the group, or order, called Odonata. In Greek the word "odon" means tooth. Damselflies are Odonata, too.

My grandmother called them "snake doctors" and said they could bring dead snakes back to life. Other people called them "horse stingers" and believed they could kill a horse. But dragonflies don't have stingers, though their long tails look as if they might be armed and dangerous.

Old Timers Dragonflies were around before dinosaurs. The fossil of one shows a wingspan of nearly 30 inches. Imagine what a bunch of those would be like hovering over a pond! The wingspan of today's green darners is a little over 4 inches. In other parts of the world, there are dragonflies with wingspans of about 7 1/2 inches.

How have dragonflies managed to survive so long? Dragonflies eat all kinds of different insects and even other small aquatic animals. The dragonfly's adaptability has helped it survive.

Dragonflies also have adapted to different climates and have become widespread. They live in temperate places, like Missouri, and in tropical ones, like those near the equator. There are more than 3,500 kinds of dragonflies in the world. About a hundred species have been identified in Missouri so far. New species are still being found.

Their skill as predators has helped them survive, too. "I've seen them fly into a cloud of insects," says Dr. John Belshe, professor of biology at Central Missouri State University, "and you know they're catching something, but you can't even see it."

Dragonflies also are fairly tolerant of changes in water quality, according to Dr. Belshe, but we may have already lost some species when their watery habitat has been destroyed or polluted. Other species may be threatened.

My next goal is to catch a dragonfly with a butterfly net. Dr. Belshe has given me a tip: "Wait until the dragonfly goes by, then swing the net up. They don't see as well from below and behind."

I swing and miss over and over again. These amazing stunt flyers evade my net every time. It's a good thing I'm not counting on dragonflies for dinner! s

Joan Banks watches dragonflies on her pond just a stone's throw from Joplin. She has written novels and for many publications, ranging from Harris' Farmers Almanac to National Geographic World. This is her first Outside In article.

	Dragon or Damsel?
	DRAGONFLIES	DAMSELFLIES
	Hold their wings flat when at rest.	Most of them hold their wings up and over their bodies when at rest.
	Usually are faster and stronger fliers.	Flight is more fluttery.
	Some have eyes that meet at the top of the head.	Eyes are set far apart and bulge to the outside
	Nymph can jet forward by expelling water from abdomen.	Nymph has three flat gill plates at tip of abdomen.
	Nymph is stout.	Nymph is slender and widest at the head.