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Backyard water spots big draw for dragonflies

| Friday, Feb. 28, 2014, 6:17 p.m.
Jessica Walliser
Widow Skimmer Dragonfly

Water features have become quite popular among backyard gardeners in recent years and for good reason. They fill the garden with the relaxing sound of moving water, lure birds and increase the diversity of flora and fauna by creating a new habitat.

One of the beneficial insects often drawn to water features is the dragonfly and its close relative, the damselfly. There are more than 425 species of these valuable insects in North America, all in the Order Odonata, and all serving to help control insect pests.

Dragonflies are among the fastest fliers in the insect world. They are swift and agile aviators and can turn on a dime, and they are predators as both adults and nymphs. As generalist predators, the adults feed on mosquitoes, flies, bees, ants, moths, wasps and pretty much anything else they can nab midflight. They then find a perch and consume their victim using the teeth in their lower jaw.

Both dragon- and damselflies have two pairs of translucent wings that each move independently of each other and can be used to steer the insect like rudders. A quick and easy way to distinguish the two groups is to observe the way the wings are held when the insect is resting. Dragonflies lack a “hinge” to close their wings and so they rest with their wings out flat. They also have two large compound eyes that face forward and sometimes touch. Damselflies fold their wings together up over their long, delicate abdomen when they are perched, much like a resting butterfly. The compound eyes of damselflies are wide-set. Both also have three simple eyes grouped together between their stubby antennae.

Dragon- and damselflies are most often found near water as they spend their larval stage on the bottom of ponds, streams, lakes, creeks and rivers. The naiads (the technical name for their larvae) breathe through gills and eat the likes of tadpoles, snails, mosquito larvae and other aquatic insects. A significant portion of the lives of these creatures is spent as a naiad.

While — depending on the species — they may spend anywhere from 11 months to several years as a larva, their adult life lasts a mere month. Naiads undergo a series of molts as they grow. Just before the final molt, the insect crawls from the water and positions itself on a rock or plant stem, head pointed upwards. The larval skin then splits and the partially emerged adult hangs upside down until its skin hardens. Eventually, the wings fill with blood and the insect is able to fly. The whole process takes less than an hour. They soon develop their full coloration and are ready to begin the mating process a week or two later.

Some species lay eggs by flying over the water's surface and repeatedly dabbing their abdomen into the water, each time, depositing an egg. Other species insert eggs into plant tissue or “glue” them to rocks or plants in shallow water. The resulting naiads have a harpoon-like jaw that rapidly juts out from their mouth, nabs prey, and then conveniently deposits it back into their mouth.

There are many common species that can readily be found flitting around backyard water features here in Western Pennsylvania, including the common green darner, the Eastern pondhawk, bluets and the widow skimmer.

Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio. She is the author of several gardening books, including “Attracting Beneficial Bugs to Your Garden: A Natural Approach to Pest Control” and “Good Bug, Bad Bug.” Her website is www.jessicawalliser.com.

Send your gardening or landscaping questions to tribliving@tribweb.com or The Good Earth, 503 Martindale St., 3rd Floor, D.L. Clark Building, Pittsburgh, PA 15212.

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