2006 Photograph, Blue-tipped Dancer Damselflies (Argia tibialis) male and female "in tandem", Occoquan Bay NWR, Woodbridge, Virginia © 2007.
Male Damselflies, like Dragonflies, have their sex organs at the tip of the abdomen like most other insects.  However, because the males use the clasping organs, also at the tip of the abdomen to grasp the female's thorax during mating, they first have to transfer a sperm packet to secondary genitalia at the base of the abdomen from where the female accepts the packet during mating.  It is thought that this system of mating evolved so that the male could protect his investment in the next generation by greatly eliminating the chance that another male could mate before the eggs have been laid.  Indeed, Odonates, especially damselflies are frequently seen in  "tandem" throughout the egg laying process, in addition to the period of actual mating.

To order: