Dragonfly nymphs are dragonflies that have not yet matured into adults. Dragonflies generally have what is known as an "incomplete metamorphosis" life cycle, because these insects do not generally have a larval stage. Instead, dragonfly nymphs hatch directly from the eggs. These nymphs typically live in water, and will periodically shed their skins as they mature. The average dragonfly nymph sheds its skin eight to 17 times during its maturation into an adult, which can take up to four years, depending on species.
Female dragonflies usually lay their eggs in the water, near the water, or in the stalks of aquatic plants. Often, the fertilizing male guards the female until the laying of eggs is complete. While most adult dragonflies live for only a couple of months, the average female will lay several batches totaling many thousands of eggs. The eggs will generally hatch in about two weeks, allowing the nymphs, also known as naiads, to emerge.
Depending on species, dragonfly nymphs can spend up to four years in the water before they undergo their final transformation into adults. Most dragonfly nymphs have abdominal gills found in the interior of the rectum. They can usually propel themselves about by sucking water into their abdominal gills and squirting it back out again. In this manner, dragonfly nymphs can get up the speed to capture prey or escape from predators.
Water fleas, newt larvae, bloodworms, and pond snail eggs are among the organisms typically preyed upon by dragonfly nymphs. The nymphs are typically preyed upon in turn by larger insects, fish, and leeches.
It can take anywhere from one to four years for the typical dragonfly nymph to reach adulthood. The nymphs typically remain in the water until they mature. During their nymph stage, dragonflies will usually shed their skins and grow larger eight to 17 times. The developmental period between each molting is typically known as an instar.
Once the dragonfly nymphs have become sizable enough, they will generally leave the water to undergo their final molting. This final molting typically reveals the dragonfly's adult wings. Dragonfly nymphs often undergo their final molting at night, and will often do so in large groups. Biologists believe that dragonflies may molt on a large scale to ensure the availability of a mate, and as protection against predators. Once the dragonflies have matured, they will typically live for another six to eight weeks.