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Reddit"Gomphid!" someone shouted, and the little thing with the gleaming fuselage hovered, then sped away. I was standing on the whitish gypsum-rich hardpan that passes for soil in the desert about 15 miles north of Roswell, New Mexico. The air around me was filled with mostly unidentified flying objects.
I now knew that this yellow-and-black creature was a Gomphid, a genus of dragonfly. But many of the dozens of other Odonata, the general scientific name for dragonflies and damselflies, which flew aerial gymnastics around me, remain nameless. This particular location—the Bitter Lake National Wildlife Refuge—hosts a great variety of these curious creatures.
My expert guide, Robert R. Larsen, is a well-built man who carries a big white net as comfortably as many men carry a briefcase. By training a botanical illustrator and by preference a biological "investigator," Larsen was the scientist to whom the managers of the Bitter Lake National Wildlife Refuge turned when they identified an unusually large number of Odonata species helicoptering around the sinkholes of the refuge in 1998.
With funds from the state Game and Fish Department, Larsen—a resident of Roswell who had been analyzing the plant life of the refuge—netted more than 50 species of dragonfly and some 30 species of damselfly. They included the largest dragonfly found in the United States (Anax walsinghami) and one of the nation’s smallest damselflies (Ischnura hastata). An easy way to distinguish between a dragonfly and a damselfly is to observe the wings: the rear, or posterior, pair of dragonfly wings are broader than the front, or anterior, pair, while both sets of a damselfly’s wings are essentially equal in size.
Other distinguishing characteristics include the eyes of the damselfly, which are on opposite sides of its head, while dragonfly eyes are typically closer together, sometimes even connected. These bulging and usually colorful organs have up to 30,000 facets. Both creatures, however, enjoy expanded peripheral vision, a formidable feature for a predator, which both dragonflies and damselflies become early on in their lives.
"I’m really glad the larvae aren’t huge, or that I’m not really small," said Karen Gaines, a graduate student at the University of New Mexico who has been studying Odonata larvae at the refuge. Most dragonfly larvae, which are aquatic for one to two years, are utterly insatiable, eating everything they come across, including tadpoles, fish, and mosquito and other insect larvae. They even eat their own siblings.
Eventually, the larva climbs out of the water; its outer "skin," or exoskeleton, splits open, it pulls its telescoped abdomen out of the casing and it gradually extends to full length. Within one to two hours, the wings clear, dry out and open up. After its wings harden, over the course of several hours to several days, the creature will become a remarkable aerialist. Some species can fly up to 35 miles per hour. Their wings work independently, so they can hover and change direction instantaneously. Some species are migratory and, with the wind’s help, may travel hundreds of miles.
Adult life is relatively brief, typically a matter of weeks, though some species can live for as long as a year. The time is spent voraciously feeding on mosquitoes, assorted moths and butterflies, and mating, a complex affair that turns a pair into an acrobatic and often airborne pretzel. Larsen reports seeing a large dragonfly carry off a minnow, a sight so remarkable that other scientists have questioned him on it. While I was standing right next to her, Karen Gaines swished her net in the air and caught a Gomphus militaris with the wing of a damselfly still hanging from its mouth. (Additional excellent detail about the biology of Odonata is covered in Dragonflies of the World by Jill Silsby, a new book published by Smithsonian Institution Press.)
thanks-- this is a good model, but it's time for another dragonfly story, so I have it for you with good pictures coming. really beautiful pictures on your way. they are very hard work, almost as difficult as lycaenidae...
Posted by pogo on May 17,2008 | 09:59AM