Dragonfly Wins State Title; Mosquitoes Miffed
Alaska will have a state insect---officially---on Aug. 24. After an energetic campaign by students from the Auntie Mary Nicoli Elementary School in Aniak, the winner is the four-spot skimmer dragonfly. It mauled the mosquito. It battered the butterfly. And it bested the bumblebee in a tight contest to be the Last Frontier's official insect.
Dragonflies, also known in some parts as mosquito hawks, horse stingers and devil's darning needles, dart through the Alaskan air, tiny helicopters in search of mosquitoes and other prey. Actually, it's an insult to compare the flying ability of dragonflies with any man-made aircraft. Dragonflies can stop on a dime at 35 miles an hour, fly backward, and cut turns that are too abrupt for any human pilot to stomach.
Aerospace engineers at the University of Colorado set out to learn some of the secrets of dragonfly flight a few years ago in pursuit of a better flying machine, as was detailed in National Wildlife magazine. The late Marvin Luttges, along with then-graduate student Mark Kliss and others, tethered dragonflies inside a wind tunnel to study their wing movements.
Wind tunnels are by no means the greatest obstacle dragonflies have faced in their 300 million years on earth. Today's dragonflies differ little from their ancestors, except their wingspan is no longer as large as a raven's. They hatch into nymphs from eggs their mother laid in water, and quickly become aggressive predators who ferociously gobble other insects, tadpoles and fish fry. Eventually they climb out of the water onto a plant stem or land, sprout four wings, and begin their lives as efficient airborne hunters who can spot a mosquito at 40 yards.
The wings of a dragonfly must be the envy of engineers. Measuring about two inches long and shaped like the business end of a butter knife, the wings are composed of a network of tubular veins coated with a transparent film of chitin, the light, resilient material that makes up the external shell of many insects.
Unlike more recently evolved insects, dragonflies can't fold their wings back, as can butterflies or damselflies, which look like small dragonflies but have bugged-out eyes that make them look like a ball-peen hammer with wings. The easiest way to tell these cousins apart is that a resting damselfly folds its wings, while a dragonfly's wings stay extended to its side.
After capturing dragonflies (helped by the observation that the insects always take off at a 45-degree angle when startled), the Colorado researchers refrigerated the dragonflies to slow them down, then photographed them flying in a wind tunnel, adding nontoxic smoke to the wind to see how it was affected by the dragonflies' wings. By freezing the action on film, the researchers saw something unexpected---the dragonflies twisted their wings on the down stroke. This created whirlwinds that made the smoke curl off like strips of freshly planed wood on the top surface of the wings. This indicated the presence of what engineers call "unsteady airflows," which move air faster over the upper surface of the wings, creating less air pressure there and giving incredible lift.
By using this unsteady airflow, as opposed to the steady airflow man-made aircraft employ, the dragonflies generated enough lift during certain parts of their wing beat to keep 15-to-20 times their weight in the air. That's an efficient flying machine.
After the votes were tallied from every public school in the state, the dragonfly downed the mosquito 3,914 to 3,035. In a sponsor statement for House Bill 239, which Gov. Knowles signed into law in May, Rep. Irene Nicholia stated a reason the dragonfly was more worthy to represent the state than the mosquito: "The dragonfly's ability to hover and fly forward and backward reminds us of the skillful maneuvering of the bush pilots in Alaska."
Maybe someday we'll have an aircraft as efficient as the Alaska state insect. If only 747's would eat mosquitoes.
