These were extremely plentiful at Muscatatuck NWR on this date. I found the majority of them in the woods (closed canopy) near the Muscatatuck River, along the west river trail. Their behavior and 'sound' was similar to the Eastern Pondhawk Dragonfly. It wasn't until I made a closer inspection that I saw they WEREN'T dragonflies. Dragonflies were also flying in the area, but I couldn't determine if these flies were predating the them.