The life of a dragonfly, an ancient insect belonging to the order Odonata, is defined by a complete transformation of its existence. Unlike insects that undergo complete metamorphosis with a dormant pupal stage, the dragonfly follows an incomplete (hemimetabolous) metamorphosis, transitioning directly from an aquatic young to a winged adult. This unique life cycle is characterized by a lengthy, predatory underwater phase and a much shorter, aerial reproductive phase. The entire process hinges on a profound physical shift that allows the organism to survive and thrive in two completely different environments.
Laying the Eggs
The dragonfly life cycle begins when the female deposits eggs in or near a freshwater source, a process called oviposition that varies significantly between species.
Females of some families, such as the darners, employ an endophytic strategy. They use a specialized, pointed organ called an ovipositor to slice into plant stems, moss, or submerged decaying wood. These eggs are typically elongated and are laid singly within the protective tissues of the plant, which offers defense against predators and harsh environmental conditions.
Many other species use an exophytic method, dropping or washing their eggs directly into the water or onto wet mud. These females generally lack a functional, blade-like ovipositor and instead extrude their round, elliptical eggs from the tip of the abdomen. They often fly low over the water, repeatedly tapping the surface to release the eggs, which then sink to the sediment or adhere to aquatic vegetation. This method allows for a much larger number of eggs to be laid, sometimes hundreds at a time, but provides less individual protection.
Life Underwater: The Naiad Stage
Once the egg hatches, a tiny, aquatic larva emerges, known as a naiad or nymph, beginning the longest phase of the dragonfly’s life. This stage can last anywhere from a few months to more than five years, depending on the species and the climate. The naiad is an entirely aquatic ambush predator with cryptic coloring that helps it blend into the mud, silt, or plant matter of its underwater habitat.
The most distinctive adaptation of the naiad is its hinged lower lip, or labium, often referred to as the mask because it is folded back over the face at rest. When prey, such as insect larvae, worms, or small fish, comes within range, the naiad rapidly shoots the labium forward to grasp it with terminal hooks. This strike is powered by a sudden increase in hydraulic pressure from the insect’s internal fluid.
Respiration occurs internally through a set of gills located in a chamber within its rectum. The insect draws water into the rectal chamber to extract oxygen and then expels the water rhythmically. By forcefully and rapidly expelling this water, the naiad can generate a strong propulsive jet, allowing it to dart forward to escape danger. Throughout this lengthy stage, the naiad grows by repeatedly shedding its exoskeleton, a process known as molting, which can occur between six and 18 times before it is fully developed.
The Great Emergence
The final molt marks the end of the aquatic existence and the beginning of the aerial life. Triggered by factors like temperature and the length of daylight, the fully grown naiad stops feeding and climbs out of the water, typically onto a vertical surface like a reed, rock, or tree trunk. This ascent is important, as the insect must now rely on air for respiration for the first time.
The larval skin, known as the exuvia, splits open along the thorax, and the adult slowly begins to emerge. It first pulls out its head, legs, and thorax, then arches backward, hanging from the tip of its abdomen while its legs harden enough to grip the abandoned larval case. The final step involves pulling the rest of the abdomen free and beginning the process of wing expansion.
The wings, initially soft and crumpled, are slowly inflated as the adult pumps hemolymph (the insect equivalent of blood) into the delicate veins. This entire process of eclosion can take up to three hours for larger species. During this time, the emerging dragonfly is defenseless against predators and susceptible to damage from wind or rain. The empty, brittle shell of the naiad is often left clinging to the vegetation.
From Teneral to Adult
The newly emerged dragonfly is referred to as a teneral adult, characterized by a soft, delicate body, limited flight capability, and pale, subdued coloration. The wings, while fully expanded, still have a milky sheen and are not yet strong enough for sustained, agile flight. This teneral period is a necessary phase for the insect to recover from the physical exertion of emergence and to complete its physical development.
The adult gradually moves away from the water’s edge to a safe, sheltered location where it will spend several days or sometimes a week. During this time, the body’s outer layer hardens, the flight muscles strengthen, and the species-specific, vivid adult colors intensify and become fully visible. Once this maturation phase is complete, the dragonfly achieves its full strength and returns to the water, where its remaining life will be focused entirely on finding a mate and beginning the cycle anew.