Dragonfly sex involves one very unusual step: before mating, the male must transfer sperm from his sperm-producing genitals (located in segment 9, at the tip of his abdomen) to the accesory genitals located on segments 2 and 3, underneath his abdomen. These include a sperm resrvoir and a penis.  Male dragonflies accomplish this transfer solo, before they attempt to copulate. This type of sperm transfer is unique to the Odonates among insects, although it is common in spiders.

The female pictured above has her genitals (also located in segment 9 at the tip of her abdomen) clasped against the male's penis and sperm reservoir. The male holds the female behind the head with his 3 claspers, and she holds onto his abdomen with her middle pair of legs. They are able to fly while united thus, albeit slowly and clumsily, with the male towing the female. I followed these two around for about 10 minutes, until they'd had enough of me and flew off across the river.

After mating, the male green darner will tow the female around and over water, where she will insert her eggs into the stems of water plants. Flying in tandem, the male can guard his mate from sexual assaults by other males. This practice is known as contact guarding, and is a common among damselflies as well. [1]

Dragonfly docking apparatus - male claspers latch onto female's head

Odonates are completely harmless - they do not sting or bite. Indeed, they are beneficial in the same respect spiders and other predators are beneficial - they keep the burgeoning insect population in check. Many of these species prey on each other; I often see dragonflies with damsels in their clutches. Dragonflies are among the most ancient of living creatures. Fossil records, clearly recognizable as the ancestors of our present day odonates, go back to Carboniferous times which means that the insects were flying more than 300 million years ago, predating dinosaurs by over 100 million years and birds by some 150 million.

Much larger dragonfly species existed in the distant past than occur on earth today. The largest, found as a fossil, is an extinct Protodonata named Meganeura monyi from the Permian period, with a wingspan of 70-75 cm (27.5-29.5 in). This compares to 19 cm (7.5 in) for the largest modern species of odonates, the Hawaiian endemic dragonfly, Anax strenuus. The smallest modern species recorded is the libellulid dragonfly, Nannophya pygmaea from east Asia with a wingspan of only 20 mm, or about ¾ of an inch.

Dragonflies are the world's fastest insects and, although estimates of their speed vary wildly, most credible authorities say they are capable of reaching speeds of between 30 and 60 km/h (19 to 38 mph). A study showed that dragonflies can travel as much as 85 miles in one day.