This is a male Clamp-tipped Emerald, named for the distinctive clamp-shaped claspers at the end of his abdomen. Clamp-tipped Emeralds patrol shady forest streams, and sometimes venture into nearby fields or open fens to feed. This male was photographed at Cedar Bog. I've also seen many Clamp-tipped Emeralds at the Beavercreek Wildlife Area, but it can be tricky to find a perched individual to photograph. 

This is a female Clamp-tipped Emerald. Both males and females have brilliant green eyes (sometimes dull in older individuals). Clamp-tipped Emeralds have much thicker abdomens than the super-thin Mocha Emeralds. Clamp-tipped Emeralds also have two yellow stripes on the side of the thorax (Mocha Emeralds are unstriped). Clamp-tipped Emeralds do not have yellow dots along the abdomen like Mochas do. 

Swift River Cruisers are fairly common in our area but very difficult to find perched. I photographed this Swift River Cruiser at High View, Twin Creek MetroPark, on June 18, 2016. It was a very hot day, and this dragonfly was making short patrols through a cedar glade at the bottom of the hill. After I watched him zoom back and forth for a long time, the dragonfly finally got tired and perched in a tree. My patience was rewarded at last.

Female Clamp-tipped Emeralds have a thorn-like ovipositor (below the abdomen tip). Females often have mud-stained abdomens, from depositing their eggs in muddy surfaces. The individual at left was photographed on October 7, 2017, at Spring Lakes Park in Bellbrook. That is an unusually late date for Ohio. Clamp-tipped Emeralds are more common in July and August. 

Swift River Cruiser, perched high in a tree at Crain's Run Nature Park (south of Miamisburg). These large dragonflies are swift fliers and patrol medium to large rivers and creeks. Swift River Cruisers have brilliant green eyes (like the Clamp-tipped Emerald above), but they can be distinguished by the bright yellow spot on their abdomen (just above the club). River Cruisers also have a single yellow stripe on the side of the thorax (Clamp-tipped Emeralds have two stripes). 

This is a newly-emerged, teneral Swift River Cruiser. I found it early in the morning, on the banks of the Great Miami River near Miamisburg. Swift River Cruisers fly from June through early September. There are two subspecies of Swift River Cruisers; the one in our area (sometimes called the Illinois River Cruiser) is less brightly marked than the Swift River Cruisers in the south. 

Mocha Emeralds are usually found along small creeks in shaded areas. They are probably more common than our records indicate, but Mochas are very difficult to find perched. They perch in shady spots on tree branches, where their dark brown color  makes them almost impossible to see. I was very lucky to find this teneral female. She fluttered right past my face and stayed perched for a long time. Photographed June 30, 2019, at Siebenthaler Fen. 

This is a female Mocha Emerald. She is very teneral (newly emerged). Mocha Emeralds have long, thin abdomens with small yellow dots (these dots might be faded in some individuals). There are no visible stripes on the side of the thorax.