Dragonflies have a round head and quite large relative to their body covered largely by two large double eyes, the legs that can easily catch prey while in flight. The two wings are similar, long, thin, and nearly transparent, and move independently. The vein system is very thick, many intricate, complex dashed ribs, the anterior end of the wing usually has a wing eye that is a regulator to suppress mechanical vibration, ensuring a firm wing. The belly is long. Oral crushed organs, with slender legs facing forward. Beard is small, has two segments and a small, long hairs segment. Anus appendages in the third, fourth (in males) and second (in females) segments; genital organs in the ninth abdominal burning; secondary copulatory organ on the second (in males).
The world’s largest dragonfly species today is the Central American giant needle dragonfly, Megaloprepus coerulatus and Anax strenuus, a species of dragonfly endemic to the Hawaiian Islands. In the past, there was a dragonfly with a wingspan of 60 cm long, fossils dating back 285 million years. There are about 4,500 known species currently. In Vietnam, over 500 species. Most species of dragonflies are beneficial insects that are natural enemies that eat many plant pests and flies and mosquitoes.
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