What you see here are a male and female, on the ground, with the end of the female’s abdomen locked onto the male’s secondary genitalia (at the base of his abdomen). I found them in this awkward predicament after hearing their wings rattle as they tried to take flight. What must have happened was that, while copulating, the male’s appendages at this tip of his abdomen (cerci and epiproct) lost their grip on the female’s head, but her abdomen remained firmly bound to his. They dropped to the ground and were going nowhere fast. The female (the one face-planted into the sand) looks especially uncomfortable. How embarrassing!
Imagine that the male was able to become airborne with the female still attached in this way: the female would be hanging by her abdomen and facing backwards. She would no doubt try to fly in order to orient herself properly, but that would be at odds with the male. If the female was able to take flight, the male would be hanging upside down by his genitalia (ouch!) and facing the wrong direction. With the wheel broken in this manner, flight becomes impossible. My last post illustrates how copulating dragonflies maintain flight.
I snapped a few pictures of this unfortunate pair and was about to provide assistance, but I guess the sight of a hominid reaching toward them was just the incentive they needed to finally break their bond and take refuge in the trees. For comparison, the first link above includes a far more elegant example of Stylurus olivaceus copulation.