Dragonflies are well-known insects, and many people appreciate their striking colours and equilibristic flight. They are recognized by their long and slender abdomen, their large globular eyes, which often make up a large portion of the head, their short antennae and their long wings. Their larvae live in running and standing freshwater environments. Some species are tolerant of brackish waters. Many species have small ranges, and are specific to certain habitats such as alpine mountain bogs or desert wadis. In the temperate regions of the world, dragonflies are frequently used as indicators of environmental health. Dragonfly larvae prey on all kinds of small animals up to the size of tadpoles and small fish. They take from a few weeks to several years to develop. Emergence takes place above the water on plants or on the shore, after which most species leave the water edge to mature. The males return to the water to search for females or to establish territories, whereas the females often return only to mate and to lay their eggs.
With about 5,680 species, the dragonflies constitute a relatively small insects order and most species are found in the tropics. Their sensitivity to habitat quality and their amphibious life cycle make dragonflies well suited for evaluating environmental changes. The relative ease of their identification makes it possible for volunteers to conduct mapping schemes, which produce distributional data that may be used in management plans.
The two suborders of Odonata, damselflies and dragonflies, are easy to recognize. In damselflies the fore- and hindwing have the same shape, the eyes are widely separated and most species keep their wings shut when at rest. In dragonflies the hindwing is much broader than the forewing, the eyes touch each other in most species and the wings are spread out when at rest.