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The dragonfly is a flying insect belonging to the infraorder Anisoptera of the order Odonata. About 3,000 extant species of true dragonflies are known. Most are tropical, with fewer species in temperate regions. Adult dragonflies are characterized by a pair of large, multifaceted, compound eyes, two pairs of strong, transparent wings, sometimes with coloured patches, and an elongated body. Many dragonflies have brilliant iridescent or metallic colours produced by structural coloration, making them conspicuous in flight. An adult dragonfly's compound eyes have nearly 24,000 ommatidia each. Dragonflies are predatory insects, both in their aquatic nymphal stage (also known as "naiads") and as adults. In some species, the nymphal stage lasts up to five years, and the adult stage may be as long as 10 weeks, but most species have an adult lifespan in the order of five weeks or less, and some survive for only a few days. Loss of wetland habitat threatens dragonfly populations around the world. This male Onychogomphus forcipatus dragonfly was photographed in Kresna Gorge, Bulgaria.Photograph credit: Charles J. Sharp