Dragonfly in Huntley Meadows Park, Alexandria, Virginia. The dragonfly is a Blue Dasher (male) - Pachydiplax longipennis.

From Wikipedia: The Blue Dasher (Pachydiplax longipennis) is a dragonfly of the skimmer family. It is common and widely distributed in the United States.

Mature males develop a bluish-white pruinescence on the back of the abdomen and, in western individuals, on the thorax. They display this pruinescence to other males as a threat while defending territories at the edge of the water.

Although the species name longipennis means "long wings", the wings are not particularly long. Females do, however, have a short abdomen that makes the wings look longer in comparison.