This is a Rapids Clubtail. Unlike the Unicorn Clubtail, this is a rather uncommon and localized species. It is also one of our smaller clubtails. Notice the two yellow half-circles on the side of the club. 

Unicorn Clubtails are typically found around ponds from late May through early July. This is one of the few clubtail species that prefers ponds rather than rivers. 

You would think that something named "unicorn" would be rare, but the Unicorn Clubtail is actually one of our most common clubtails. This dragonfly gets its name from a very tiny horn on its forehead.

The top of the club (Segments 8 & 9) is all-black in a Rapids Clubtail. This distinguishes Rapids Clubtails from other small clubtails - such as the Lancet Clubtail, which has yellow on the top of Segments 8 & 9.  

Unicorn Clubtails are very distinctive due to the golden claspers at the end of the abdomen. The only two similar species in Ohio are the Lilypad Clubtail (not documented in southwestern Ohio) and the Jade Clubtail (only known from Lake Loramie, where it was discovered in 2018). 

All of my Rapids Clubtail sightings have been in early and mid-June (between June 1 - June 18). This species has a mass, synchronized emergence. You need to be in the right place at the right time to see them. 

I usually see Rapids Clubtails at Germantown MetroPark, but I also have one sighting along the Great Miami River at Miamisburg.