Ohio, and surrounding states I'm sure, have experienced a blitzkrieg of migrant dragonflies in the past few days. I've received about a dozen reports at work, a few more here at home, and have seen reports of dragonfly swarms on Facebook and other places. The vast majority of these dragonflies are the highly migratory Green Darner, as shown in Dave's shot above. These dragonflies are headed to points south, and pushing through in vast inestimable waves in front of the coming cold front.
I penned an article about this time of year in 2011, for my employer the Ohio Division of Wildlife. That column made its way to a number of newspapers, and is still findable on the net, apparently - it was the catalyst for a number of the reports that I received. Following is that piece, which goes into more detail about Green Darners and dragonfly migration. It is just as relevant to the current flight as it was a few years ago.
A lot remains to be learned of dragonfly migration, and observations of large swarms are helpful to researchers. If you have witnessed a dragonfly swarm, please report it to