Several kinds of dragonflies show this pattern of black wing spots.
Male 12-spotted skimmer: bright white spots between the black ones
Female 12-spotted skimmer: lacks the white wing spots. Abdomen dark brown with solid bright yellow lines down the outer top edges.
Female common whitetail: like the female 12-spot, but the yellow lines on the abdomen are borken and not solid.
Two rarer species also have similar wing spot patterns:
Calico pennant: has a much larger dark spot at the base of the hind wing, and a much smaller spot at the base of the forewing. Its abdomen is bright red in the male and yellow in the female.
Price baskettail: flies continuously, seldom if ever landing, and has bright green eyes.
http://www.willowbrookwildlife.com/Dragonflymain.asp
