They have mouths adapted for biting and two nearly equal pairs of elongated membranous wings. The abdomen is relatively long. The legs are located far forward on the body and are seldom used for walking. The damselflies are generally smaller and weaker in flight than the true dragonflies. Both types are known by popular names such as darning needle, devil's darning needle, snake feeder, snake doctor, and mosquito hawk.
Dragonflies undergo incomplete metamorphosis during their development.
The eggs of all species hatch into nymphs, which mature in the water, feeding on various forms of aquatic life. Nymphs of some of the large species will even attack small fish. Dragonfly nymphs have a special extensible lower jaw, called the mask, with which they seize their prey. The length of time that dragonflies spend in nymphal form varies from one to three or more years, during which the nymph molts ten or more times. When nymphs have fully matured they leave the water and undergo metamorphosis into the adult form.