We thought that our Twelve-Spotted Skimmers had left us, then the handsome fellow below showed up Tuesday, September 4. (We know that this is an adult male because it has both brown and white spots; females and young males only have white spots. )
There is an ever-widening investigation by scientists and volunteers to determine which dragonflies migrate and which end their lives in the cold of the North. Twelve-Spots have been sighted within swarms of migrating dragonflies moving southward along the Atlantic coast; Twelve-Spots also usually become evident in the South later than other dragonflies, which is another indication that they might be migrators.
For comparison to the male above, here's an older image of a female Twelve-Spot and a Common Green Darner – a known migrant: