Dragonflies have a life cycle intrinsically linked to freshwater environments, with the entire pre-adult phase occurring beneath the surface. The reproductive process begins when the adult female seeks a suitable aquatic site to lay her eggs, a choice that is vital for the survival of the species. Selecting the correct location dictates the conditions the offspring will experience, directly impacting their growth and development over the next several months to years. This necessity for precise habitat selection highlights the connection between the adult’s brief aerial life and the long, submerged existence of its young.
Different Ways Dragonflies Lay Eggs
The physical act of depositing eggs, known as oviposition, is executed through two distinct strategies, each corresponding to a different female anatomy. The first method is endophytic oviposition, where the female uses a specialized, blade-like organ called an ovipositor to cut into and insert eggs within plant tissue, wet wood, or mud near the water’s edge. This technique, used by species like the darners (family Aeshnidae), provides protection for the elongated eggs, which are laid singly or in small groups. The mechanical process of insertion means fewer eggs are deposited in a single event, often fewer than 300, but they are better shielded from predators and desiccation.
The second, less protective method is exophytic oviposition, utilized by most other dragonfly families, such as the skimmers (Libellulidae) and clubtails (Gomphidae). Females using this strategy lack a fully developed ovipositor and instead simply extrude their spherical or ellipsoidal eggs directly into the water. This can happen in a few ways: the female may tap the tip of her abdomen onto the water surface while in flight, releasing the eggs to sink, or she may attach them in a gelatinous mass to submerged objects. The simplicity of this technique allows for a much higher reproductive output, with some species laying over 1,500 eggs in a single clutch, though they are more vulnerable to aquatic predators.
Required Aquatic Environments for Egg Sites
The aquatic environment required for egg-laying falls into two general categories: standing or flowing water. Many dragonflies, particularly those that use the exophytic method, prefer still or slow-moving water bodies such as ponds, marshes, lakes, and wetlands. These habitats provide the calm surface necessary for females to drop their eggs without the risk of them being swept away. The presence of floating vegetation, submerged plants, or a muddy bottom is often required, as these offer the specific substrate for eggs to adhere to or be inserted into.
Conversely, some families require moving water, such as the clubtails (Gomphidae) that breed in running streams and rivers. Site selection involves physical characteristics beyond just water flow, including a sunlit stretch of shallow water or the specific type of algae or mud present. The precise selection of a high-quality oviposition site is important, and males of many species will defend a territory that contains the preferred features.
Some species have evolved eggs that resist drought, allowing them to utilize temporary pools that may dry up seasonally. Others lay eggs on emergent plants above the water, delaying development until the vegetation withers and is immersed.
Life Beneath the Water Surface
Once the eggs hatch, the dragonfly enters its larval stage, known as a nymph or naiad, which is the longest period of its life cycle, lasting from a few months to five years in some larger species. These aquatic nymphs are lie-in-wait predators, using a specialized lower lip, the labium, to rapidly capture passing prey. The nymph’s diet consists of invertebrates, and larger individuals are capable of consuming tadpoles and small fish.
Nymphs are completely dependent on the water for respiration throughout this extended developmental period. They breathe by drawing water into their abdomen and over internal gills, a process which also allows them to use a form of jet propulsion by rapidly expelling the water. When development is complete, the nymph crawls out of the water onto emergent vegetation for its final molt. This process concludes the aquatic phase and begins the adult’s short, flying life.