That glittering fairy fluttering in the dappled shade near the brook at this time of year is probably an Ebony Jewelwing, Calopteryx maculata, a type of Broad-winged Damselfly. The body is 40-50mm long, and this one is a male, with an iridescent turquoise body and ebony black wings and eyes. Look closely, and you can even see how the wings attach to the thorax.
This one is a female: browner, and with a white spot on the wing tips.
They eat small insects: this guy has just caught one:
The nymph stage lives in slow-moving streams, so the adults are typically found close to water, in sunny openings on low shrubs. As you might expect given their habitats, they in their turn are eaten by both land and water predators, such as birds, bats, turtles, larger fish.
The scientific name Calopteryx comes from the Greek “kalos” (beautiful) + “pteron” (wing or feather), and maculata comes from the Latin “macula” (a spot) – a reference to the white spot near the tip of the female’s wing. They are found throughout eastern North America.