From the Editor-in-Chief
I always wondered…. They act like drunk racecar drivers – bolting back and forth, up, down, and around. Their speed is shocking, but their agility is what always catches my attention. One individual is usually chasing the other, which I interpret as them having fun on a summer day. But then they are sometimes locked together as a pair – sometimes backwards, forming a heart shape… what these animals won’t do to have fun! T’is that season in New England, and they are at it again. My mom’s favorite pendant was a dragonfly also. She wore it proudly, believing that it gave her good luck, it helped her garden grow, and it may have even reminded her of watching their acrobatics as a kid. If she only knew… it is all about the mating, of course. Dragonflies and damselflies form a clade, the Odonata, members of which have been around over 300 million years. Dragonflies are generally larger than damselflies, and when they alight on a limb, dragonflies hold their pairs of wings to the sides. Damselflies have smaller, more slender bodies and hold their wings over their body when at rest. This is important knowledge to have at hand for when kids at the park see these special insects, or when the late summer picnic shifts to small talk. Many of these beautiful and graceful creatures have excellent vision and are extremely territorial. Male dragonflies rely mostly on their eyesight to find and distinguish potential invaders of their territory, or to identify potential female partners among the dense autumn population. A male can recognize a conspecific female by taking inventory of her characteristic flight movements, her colors and their patterns, and her size. When a male sets out to “subdue” the female, he approaches her in flight and grasps her body with his legs; he may bite, clasp, poke, and even land on the female in the process of subduing her. He then must pull his abdomen forward and use his anal appendages (that does not sound good) to grab her tightly by the neck and then extend his body just to mate – all while continuing to fly with her. Clearly good grip strength of one’s anal appendages is important here. If the female has not shaken, bitten, or poked the male off, he will prepare for sperm transfer, i.e. dragonfly sex. The male dragonfly penis is different than in humans (Really different – my research confirms this!). Male dragonflies have two sets of sex organs: the testes are located at the end of the male's abdomen, behind its legs, whereas the penis and a small sac-like structure for storing sperm are much further up the body. Before copulation, a male dragonfly must move his sperm from the testes to the storage pouch, and then into the penis. Only after his penis is fully loaded will he be able to inseminate the female he spotted, tracked, and subdued. The female's genital opening is near the end of her abdomen (same location as the testis is in males). Since the male's penis is closer to his thorax, and on its underside, the female must bend her abdomen forward to bring her genitalia into contact with his penis. These mid-flight acrobatics create many body shapes – including that of a heart – and is a behavior unique to Odonata . . . and is striking to the casual summer observer. So cool! But wait, there’s more! Odonata have been intensively studied because of their interesting characters of territorialism, mating, vision, etcetera, but they also serve as excellent models for studying sperm competition. These animals were (one of) the first examples in which the “last in, first out” model of sperm competition was described. A male dragonfly increases his chances of reproduction if his sperm are the last cohort to be inserted into the female. This strategy is enforced in some species by males trailing his recent mate to keep other suitors away from her until she lays her eggs, which were previously fertilized with his sperm. But that is a lot of work! So an alternative strategy is for the male to use its multi-purpose penis to first scoop out any sperm previously deposited in the female, and then insert his own sperm. Some male dragonflies have backwards-facing hooks or barbs on their penises to facilitate this sperm exchange. Other male dragonflies use their penises to move competing sperm aside before inserting his own, which would now be optimally placed for a pending fertilization. The abundance of Odonata species corresponds to a diversity of approaches that address sperm competition, and indeed these flies have educated us in just how talented a penis can be! So, whether or not wearing a dragonfly pendant brings good luck or a prosperous garden is still unclear, but learning how diverse and exciting reproductive competition is in the world – now that helps me see these beautiful, agile, and dream-inducing insects in a different light.
Gary Wessel Waage, J. 1979. Science 203:916. ngm.nationalgeographic.com/print/2006/04/dragonfly-mating/ackerman-text
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I always wondered…. They act like drunk racecar drivers – bolting back and forth, up, down, and around. Their speed is shocking, but their agility is what always catches my attention. One individual is usually chasing the other, which I interpret as them having fun on a summer day. But then they are sometimes locked together as a pair – sometimes backwards, forming a heart shape… what these animals won’t do to have fun! T’is that season in New England, and they are at it again. My mom’s favorite pendant was a dragonfly also. She wore it proudly, believing that it gave her good luck, it helped her garden grow, and it may have even reminded her of watching their acrobatics as a kid. If she only knew… it is all about the mating, of course. Dragonflies and damselflies form a clade, the Odonata, members of which have been around over 300 million years. Dragonflies are generally larger than damselflies, and when they alight on a limb, dragonflies hold their pairs of wings to the sides. Damselflies have smaller, more slender bodies and hold their wings over their body when at rest. This is important knowledge to have at hand for when kids at the park see these special insects, or when the late summer picnic shifts to small talk. Many of these beautiful and graceful creatures have excellent vision and are extremely territorial. Male dragonflies rely mostly on their eyesight to find and distinguish potential invaders of their territory, or to identify potential female partners among the dense autumn population. A male can recognize a conspecific female by taking inventory of her characteristic flight movements, her colors and their patterns, and her size. When a male sets out to “subdue” the female, he approaches her in flight and grasps her body with his legs; he may bite, clasp, poke, and even land on the female in the process of subduing her. He then must pull his abdomen forward and use his anal appendages (that does not sound good) to grab her tightly by the neck and then extend his body just to mate – all while continuing to fly with her. Clearly good grip strength of one’s anal appendages is important here. If the female has not shaken, bitten, or poked the male off, he will prepare for sperm transfer, i.e. dragonfly sex. The male dragonfly penis is different than in humans (Really different – my research confirms this!). Male dragonflies have two sets of sex organs: the testes are located at the end of the male's abdomen, behind its legs, whereas the penis and a small sac-like structure for storing sperm are much further up the body. Before copulation, a male dragonfly must move his sperm from the testes to the storage pouch, and then into the penis. Only after his penis is fully loaded will he be able to inseminate the female he spotted, tracked, and subdued. The female's genital opening is near the end of her abdomen (same location as the testis is in males). Since the male's penis is closer to his thorax, and on its underside, the female must bend her abdomen forward to bring her genitalia into contact with his penis. These mid-flight acrobatics create many body shapes – including that of a heart – and is a behavior unique to Odonata . . . and is striking to the casual summer observer. So cool! But wait, there’s more! Odonata have been intensively studied because of their interesting characters of territorialism, mating, vision, etcetera, but they also serve as excellent models for studying sperm competition. These animals were (one of) the first examples in which the “last in, first out” model of sperm competition was described. A male dragonfly increases his chances of reproduction if his sperm are the last cohort to be inserted into the female. This strategy is enforced in some species by males trailing his recent mate to keep other suitors away from her until she lays her eggs, which were previously fertilized with his sperm. But that is a lot of work! So an alternative strategy is for the male to use its multi-purpose penis to first scoop out any sperm previously deposited in the female, and then insert his own sperm. Some male dragonflies have backwards-facing hooks or barbs on their penises to facilitate this sperm exchange. Other male dragonflies use their penises to move competing sperm aside before inserting his own, which would now be optimally placed for a pending fertilization. The abundance of Odonata species corresponds to a diversity of approaches that address sperm competition, and indeed these flies have educated us in just how talented a penis can be! So, whether or not wearing a dragonfly pendant brings good luck or a prosperous garden is still unclear, but learning how diverse and exciting reproductive competition is in the world – now that helps me see these beautiful, agile, and dream-inducing insects in a different light.
Gary Wessel Waage, J. 1979. Science 203:916. ngm.nationalgeographic.com/print/2006/04/dragonfly-mating/ackerman-text
743
