This is a Plains Clubtail, an endangered species in Ohio. Plains Clubtails look very similar to Pronghorn Clubtails, but Plains Clubtails are larger, and the side of segment eight is black and yellow (rather than all yellow). A Plains Clubtail could also be confused with a Handsome Clubtail. Their clubs are similar, but the thoracic stripes are different. Plains Clubtails live near large rivers. I found this individual along the banks of the Great Miami River near Miamisburg, on June 3, 2017. 

This is another Pronghorn Clubtail, found at Spring Lakes Park. This species gets its name from the small "horns" on the ends of the cerci. Also, note the design at the end of the abdomen that resembles a stovepipe hat over a small diamond.

This is a teneral (newly emerged) Pronghorn Clubtail. Its wings are still shiny, and its eyes have not yet developed their mature blue-green color. 

Another teneral Pronghorn Clubtail, with iridescent wings. Pronghorn Clubtails emerge in large numbers at Spring Lakes Park from mid-May to late May. Most of these teneral individuals mysteriously disappear soon after emergence. A few mature individuals return in June and early July. 

This is a close-up view of a Pronghorn Clubtail's distinctive horned cerci. (Note that this is a teneral individual, so the color pattern is fainter and less distinct than it would be on a mature individual.) 

Pronghorn Clubtails can be found at both ponds and rivers, although populations tend to be localized. There is a good population at Spring Lakes Park in Bellbrook, where this individual was photographed. 

This is a close-up of a mature Pronghorn Clubtail's club, showing the horned cerci. 

In addition to Spring Lakes Park, I have also found Pronghorn Clubtails at Caesar Creek, Pearl's Fen, Germantown MetroPark, and along the Great Miami in Miamisburg. 

Female Pronghorn Clubtail, photographed at Caesar Creek. 

Close-up of the female Pronghorn Clubtail's club.