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Volume 14, Issue 29 ~ July 20 - July 26, 2006

Earth Journal by Gary Pendleton


The Official Insect of My Back Yard

Mosquito-hawks is what some people call dragonflies. If there is anything to back up that name, then I am ready to declare the green darner or perhaps the common white tail or the blue pirate as The Official Insect of my back yard.

Visual acuity and flying ability make dragonflies efficient predators. Like house flies, they have compound eyes, meaning that each eye is made of hundreds of tiny eyes. On the wing, they are remarkably agile, capable of a number of impressive aerial maneuvers.

Aerospace engineers at the University of Colorado discovered the key to the dragonfly’s flying abilities. Research revealed that dragonflies create an unsteady airflow by twisting their large wings on the down stroke, so that air moves faster over the upper surface of the wings. This results in less air pressure below the wings, which creates lift. This effect makes dragonflies super-efficient flyers. Like tiny helicopters, they can stop in mid-air, fly backward and execute amazingly sharp turns. Memo to mosquitoes: You can fly, but you can’t hide.

Why, then, are these amazing creatures of-the-air considered aquatic insects? Like the evil mosquito, adult dragonflies lay their eggs in water. The eggs produce larvae that live in streams, ponds or, in the case of some mosquitoes, your clogged gutters. Eventually the adults emerge from the damp in the more familiar flying forms that we recognize as dragonflies, mosquitoes and mayflies.

In fact, the presence of dragonfly larvae in streams is an indicator of good water quality. In many jurisdictions, teams of volunteers evaluate the condition of streams by looking at a range of factors, including the presence of aquatic insects.

Some people are unnerved to be in close proximity with these marvelous creatures. There are numerous examples from around the world of folk legends that portray them as dangerous. Still, there are many who appreciate dragonflies for their beautiful colors and striking form. You can find dragonfly images used to beautiful effect in jewelry, fabric designs and decorating motifs.

Like cockroaches, dragonflies are one of the most ancient forms of life in the world. In many ways, they have changed little over the eons — except for their size. In the age of dinosaurs, dragonflies were as big as large birds.

A hawk-sized dragonfly would have been a fearsome creature. But humans have nothing to fear from modern members of the order Odanata. They might look a little scary, but they won’t bite you, and they do help control those nasty mosquitoes.

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