Blue dasher. 照片檔

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 substantially longer than those of related species. Females do, however, have a short abdomen that makes the wings appear longer in comparison.