Dragonflies

Dragonflies: Masters of the Air

While in the garden the other afternoon, my hand brushed against something stiff and paper-like as I reached into my pocket for some tomato-tying twine. Surprised, I twisted my head over my shoulder and saw a huge dragonfly perched on my hip pocket. A wasp was gripped tightly in its legs. The dragonfly manipulated the wasp, turning it so that the wasp’s head was oriented towards its mouth, then began to calmly crunch the antennae and head! My neck was stiff from observing the whole procedure, but the dragonfly remained on its unusual perch until it had consumed most of the wasp. Suddenly, it took off again as quickly as it had appeared and disappeared into the background.

Dragonflies are such adept aerial predators, they are able to snatch their meals of insects from midair, then land on a convenient perch to partake. All of them eat insects, including mosquitoes, flies and, apparently, wasps. Some highly maneuverable dragonflies even eat other dragonflies, and at least one bird, the swallow-tailed kite, is a specialist on dragonflies too. No wonder the kites are such graceful and acrobatic fliers.

Around here, one of the most common dragonflies is the whitetail, but only the males have a chalky white abdomen. Females have a brown abdomen. Whitetails are active around shallow ponds, especially those without fish, where the males patrol the edges constantly. They watch for females or for other males. When a female appears, the male grabs her, they briefly mate, and he releases her as she begins to lay eggs. As she dips the tip of her abdomen again and again into the water to deposit eggs, he hovers over her, preventing other males from interfering.

The males use their white abdomens to signal each other. Each male controls only a small section of the pond’s shoreline as his territory, but there is never enough shoreline for the number of males present, resulting in constant intrusions from rival males. When a resident male chases off a rival, he holds the tip of his abdomen upright and the retreating male holds his abdomen angled downward. If you have a pond nearby, spend some time observing the different behaviors of males toward other males and toward females.

There are many other dragonflies and damselflies in our area. Most damselflies hold their wings folded over their body at rest whereas dragonflies hold their wings outstretched. Damselflies are also small and slender, which is why they are considered damsels rather than dragons. A new book on dragonflies, Dragonflies Through Binoculars, is a good reference if you want to identify those visiting your ponds. There is not yet an equivalent for the damselflies.

If you think the adults are dragon-like in their feeding habits, its only because they learned it as offspring. The larvae are also voracious predators. They live underwater in streams and ponds, usually buried in the sediment or under leaves. When other invertebrates come by, they erupt from the bottom in a flurry of particles and grab them with large, pincer-like mouthparts that unfold from beneath their chin. They eat prey similar in size to themselves, just as do the adults.

Eventually, the larvae must leave the water and take to the air. They climb out onto sticks or leaves that extend above the surface of the water. There they shed their larval skin, their wings unfurl, and they take off, never to return to the water except when females break its surface to deposit the eggs of the next generation. The shed larval skin looks a little like a small cicada skin. It takes some imagination to envision an adult dragonfly emerging from it. When I find a dried skin, I always stop and reflect on that transformation. From a life buried in mud, breathing in water, crawling along the bottom for months or years, a master of the air emerges in an instant, unchallenged except by the most agile birds. From nature springs philosophy!

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