Spot-winged Glider - Pantala hymenaea , 43-51 mm
Species page here: BugGuide

A swarm of more than 100 dragonflies stayed 10-30 feet above one end of the pond for an hour or so and then moved on shore to a shady wooded area. They stayed there for another hour in a fairly small area. They flew from bush level to about 20 feet. Only three were observed to land during that time. Two were Spot-winged and one a Wandering Glider. As they dispersed or moved on, there were a few darker dragonflies staying back, possibly Black Saddlebags.