The Nature Writers of Texas

The best nature writing from the newspaper, magazine, blog and book authors of the Lone Star State . . .

Sunday, July 22, 2007

Dragonflies Eat Mosquitoes by Ro Wauer

With all of our wet weather of late, we are certain to experience a greater than normal mosquito population. These little annoying insects breed in every conceivable place with standing water, and spraying/fogging of various insecticides can only keep the mosquito numbers at a reasonably low number. Also important for reducing mosquitoes are various natural predators, especially dragonflies that also increase during similar weather conditions. These dragons are voracious predators on many kinds of flying insects that they chase down in flight. Mosquitoes, ants, flies and midges all are utilized.

Two years ago we (Betty and I, along with son Brent and two Austin friends) constructed a "dragonfly pond" in our back yard. It was built more as a way to study and photograph dragonflies and damselflies than as a way to control mosquitoes. In fact, it is necessary to place "mosquito dunks" in the pond monthly to keep mosquitoes from taking advantage of that potential breeding place; it seems to have worked very well. Within only a few days after pond completion, two dragonfly species - roseate skimmer and blue dasher - put in their appearance. And by summer, a dozen additional dragonfly species began frequenting the pond and surroundings: eastern pondhawk; common green darner; variegated meadowhawk; black saddlebags; band-winged dragonlet; banded pennant; twelve-spotted, golden-winged, neon, and widow skimmers; wandering glider; and common whitetail. I managed to get photos of each.

Dragonflies, or course, are cold-blooded insects, but they are some of the earliest insects to put in an appearance during the morning hours, even before butterflies. They fly here and there over the yard, gobbling up various flying insects. But once the day warms up a little many perch around wetland areas, including my dragonfly pond. There they perch on the six sticks that I have placed around the pond for that purpose. At this writing, each stick is in use by two blue dashers, two roseate skimmers, a neon skimmer, and a band-winged dragonlet. And adjacent sticks are also in use. Our dragonfly population is at a peak.

Dragonflies often are misunderstood, and occasionally are even feared. Although some people fear all insects, as well as other critters they do not understand, dragonflies seem to be especially frightening. Maybe it is because of their large size, swift flight, and huge eyes. But actually dragonflies are fascinating insects that cannot cause people any harm at all. They do not sting and they eat lots of mosquitoes and other bothersome flies. They also are fascinating because of their amazing flights up to 60 miles per hour and ability to fly straight upward, sideways, glide, or hover. Amazing aerobatics! They beat their wings more than 30 times a second.

Dragonflies are closely related to damselflies, two insect groups within the order of odonates, of which there are approximately 5000 species worldwide and 435 in North America. The two groups are easy to separate: damselflies usually perch with their four wings pressed over their backs, while dragonflies perch with their four wings held straight out to the sides. All odonates utilize a three-part life cycle, including eggs, larva, also called naiad or nymph, and adult. Males are territorial, usually flying or perching at the edge or over water or other moist places. Their average lifespan is two to four weeks. They eventually mate with a passing female that lays her eggs in the water, on emergent plants, or in bottom sediments. Thus their relationship to my dragonfly pond, a natural attractant.

1 Comments:

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