Blue Dasher (Pachydiplax longipennis) - Tentative   I am going to call this one a Blue Dasher. The terminal segments are black and there is dusky coloration at the terminal half of the wings. A discussion on the University of Wisconsin Milwaukee Field Station says that male Blue Dashers are pretty territorial, although their territory is movable. Within his territory the male chases other dragonflies energetically—not solely those of his species, but similarly-colored species like Slaty Skimmers. He flies out from his perch every minute or less, returning to it if the coast is clear. This behavior was evident as I watched these guys in the detention pond area.