What Is the Life Cycle of Dragonflies? Years Underwater
What Is the Life Cycle of Dragonflies? It runs through three stages, egg, nymph, and adult, and most of that time is spent underwater rather than in the air. A dragonfly can spend up to five years as an aquatic nymph before it ever grows wings, then live as a flying adult for only a matter of weeks.
Egg Stage
A female dragonfly lays her eggs in or right next to water: ponds, lakes, slow streams, and marshes. Some species drop eggs directly onto the water's surface in short bursts, laying large numbers of eggs if left undisturbed. Others insert eggs into aquatic plant stems or submerged wood using a blade-like ovipositor.
Egg Development
Hatching time depends on water temperature and ranges from about a week to several weeks. When an egg hatches, what emerges is not a miniature dragonfly but a nymph, also called a naiad, built for life underwater rather than in the air.
Why So Many Eggs
A single female can lay eggs numbering in the hundreds or thousands over her lifetime. Fish, other aquatic insects, and predatory nymphs of the same species eat large numbers of eggs and newly hatched larvae, so a large clutch is what keeps enough offspring alive to reach adulthood.
Nymph Stage
The nymph stage is by far the longest part of a dragonfly's life. Depending on the species and water temperature, nymphs stay submerged anywhere from a few months to as long as five years, growing from about a quarter of an inch to over two and a half inches long.
Built for the Water
Nymphs breathe through gills inside their rectal chamber and have none of the adult's coloring or wings. What they do have is a hinged, extendable lower lip called a labium, folded under the head like a mask until a prey animal comes within range.
Nymphs are ambush predators. They lie still on submerged plants or debris and wait for tadpoles, mosquito larvae, other insect larvae, or small fish to swim past. A hunting nymph can eat roughly 40 mosquito larvae in a single day, which is one reason dragonfly populations matter to mosquito control around ponds.
Molting to Grow
Because a nymph's exoskeleton cannot stretch, it molts repeatedly as it grows, shedding its outer shell and forming a new, larger one each time. Depending on the species, a nymph may molt anywhere from six to fifteen times before it is ready to leave the water.
The Strike
When prey comes close enough, the labium shoots forward in a fraction of a second, powered by a sudden rise in blood pressure inside the abdomen rather than muscle alone. Hooked palps on the end snag the prey and drag it back to the jaws. It is one of the fastest strikes among freshwater predators, though exact speed comparisons across species have not been rigorously measured.
Emergence Stage
Once a nymph reaches full size, it stops feeding, crawls up out of the water onto a reed, rock, or overhanging branch, and begins the transition to an adult.
Splitting the Old Skin
Emergence happens mostly in late spring and summer, when water temperatures favor rapid final growth. Anchored above the waterline, the nymph's skin splits along its back and the adult pulls itself free, then pumps hemolymph into its crumpled wings and abdomen to expand them to full size.
The whole process can take several hours from first split to a dragonfly capable of flight. Until its wings and exoskeleton harden, the newly emerged adult, called a teneral, cannot fly and is defenseless, which is why most species time emergence for dawn or another low-predation window.
A Vulnerable Window
Birds, ants, and other predators will take a teneral dragonfly if they find one before its wings harden. Emerging in reeds or on branches away from open water reduces the odds of being caught during this stage.
Adult Stage
A fully hardened adult dragonfly has working wings and the coloring typical of its species. Compared to the months or years spent as a nymph, its time in the air is short.
How Long Adults Live
Most adult dragonflies live for around a month, though this varies by species and weather; some survive only a few days, and a few can live for several weeks longer under good conditions. Adults spend this time feeding, mating, and, for males of many species, defending a patch of shoreline against rival males.
Hunting on the Wing
Adults hunt mosquitoes and midges most often, along with flies and other small flying insects, and can eat roughly 30 to 100 mosquitoes in a single day. Their compound eyes, which can contain up to 30,000 individual lenses, give them near 360-degree vision for spotting prey. In one 2013 study, dragonflies caught about 95 percent of the prey released into their enclosure, a hunting success rate far above that of birds of prey.
Flight Built for the Chase
Each of a dragonfly's four wings is powered by its own muscles and can move independently, letting it fly straight up or down, hover in place, and reverse direction by angling its body to roughly 90 degrees. Top speeds run close to 35 miles per hour, fast enough that few flying insects can outmaneuver them.
From Pond to Sky
The egg, nymph, and adult stages each solve a different problem: surviving in large numbers, growing safely underwater away from most airborne threats, and, finally, hunting and reproducing on the wing before time runs out. A dragonfly patrolling a pond edge in summer has already spent one to several years beneath the surface as a nymph, and has only weeks left to feed and mate before its short adult life ends.
