The Common Whitetail - Libellula lydia - is a species that exhibits extreme sexual dimorphism. The males have a single large black patch on each wing, and their abdomens develop extreme pruinosity - a blue-white waxy coating - as they mature. The females in contrast look very much like female Twelve-spotted skimmers (Libellula pulchella). The only obvious difference is in the abdominal stripes - whitetails have an interrupted line while the 12-spots have a continuous line.
