Dragonflies (order Odonata) are ancient, accomplished fliers known for their powerful wings and aerial agility. They perform complex maneuvers near water, their breeding habitat. These coordinated flight patterns are integral to their reproductive strategy. Dragonflies mate while flying, a demanding feat requiring specialized anatomy and synchronized movements between the male and female.
Specialized Reproductive Anatomy
The ability of dragonflies to mate in mid-air relies on a unique reproductive system. Unlike most insects, the male dragonfly has two distinct genital structures. The primary genital opening, where sperm is produced, is located near the tip on the ninth abdominal segment. This location is far from the functional copulatory organ.
The male’s functional copulatory organ, often called the hamulus, is a set of secondary genitalia located on the underside of the second and third abdominal segments, closer to the thorax. Before copulation, the male must bend his abdomen forward to transfer a packet of sperm from the primary opening to this secondary organ. This “charging” process is performed before or immediately upon catching a female.
The female’s genital opening is located on the underside of her eighth abdominal segment. The male also possesses specialized anal appendages, or claspers, at the end of his abdomen. These claspers are used to firmly grasp the female during mating. They are species-specific, fitting precisely into corresponding structures on the female’s head, which helps prevent interspecies mating.
The Aerial Mating Process
The mating process begins with the male seizing the female in a formation known as the “tandem linkage,” often initiated in flight. The male uses his claspers to clamp onto the female, gripping her behind the head. In this tandem position, the male tows the female and controls the flight path.
Copulation requires the female to cooperate by curling her abdomen sharply forward. This brings her genital opening into contact with the male’s secondary genitalia. This maneuver creates the distinctive, closed loop known as the “copulation wheel” or “heart” shape. While some species settle on a perch, many dragonflies initiate and complete the transfer in continuous flight.
During coupling, the male engages in sperm displacement to ensure his paternity. The male’s secondary genitalia are often equipped with structures used to first remove or displace sperm left by previous mates inside the female’s storage organs. After this “cleaning” process, the male deposits his own sperm, increasing the likelihood that his genetic material will fertilize the eggs. Copulation in flight can be brief, sometimes lasting only a few seconds.
The Role of Territoriality in Mating
The mating sequence is often preceded by intense territorial behavior, which dictates which males successfully breed. Male dragonflies vigorously defend specific territories, typically high-quality breeding habitats near water sources like ponds or streams. Territory defense involves aggressive aerial displays and chasing off rivals of the same species.
A male’s ability to maintain a prime territory correlates directly with his reproductive success. Females visit these sites specifically to mate and lay eggs. By choosing to mate with the defending male, females are effectively selecting the best available habitat for their offspring. The strongest males, who can conquer and defend these disputed territories, are therefore most likely to secure a mate.
This focus on territorial defense means that male dragonflies spend significant energy on patrolling and combat. Successful territory holders achieve a much higher rate of copulation and subsequent egg-laying events than non-territorial males. Females may allow the first male they encounter to capture them, but then choose whether or not to oviposit based on the territory’s quality.
Post-Mating: Where Eggs Are Laid
Immediately following the aerial coupling, the female must deposit her newly fertilized eggs in a suitable aquatic location, a process called oviposition. Dragonflies utilize two main strategies for this, depending on the species and the female’s anatomy.
Endophytic Oviposition
The endophytic method involves the female using a specialized, blade-like ovipositor to cut into and insert eggs directly into plant tissue, mud, or rotting wood. This is common among hawker dragonflies. These eggs are typically elongated and are laid at a slower rate, offering them protection within the substrate.
Exophytic Oviposition
The more common exophytic method involves the female simply dropping or washing her eggs onto the water surface. The female achieves this by repeatedly dipping the tip of her abdomen into the water while in flight, releasing spherical eggs that sink to the bottom. This method is much faster, with some females laying hundreds of eggs per minute.
After mating, the male often exhibits “guarding behavior” to protect his genetic investment from other males. In some species, the male remains physically attached to the female in the tandem position throughout the entire egg-laying process, which is called tandem guarding. In other cases, the male engages in non-contact guarding, hovering nearby to chase off any approaching rivals. This ensures that the female completes her oviposition without being intercepted for another mating attempt.