Many dragonflies will guard their partners by simply chasing off any approaching males. In some species,like the Spot-winged Glider(Pantala hymenaea), males will continue to grasp their partners in the neck refusing to let go until she deposits her eggs in the water. I assume a bird or fish grabbed the female and came away with everything but the head. Surprisingly the male wasn't able to detect the absence of most of his partner and continued trying to lay eggs.