Whoa! Rotational error, rotational error!!
Female Darter returning to perch... she made it!
Pure luck and shutter speed has allowed the capture of the wing rotation [one up/one down on the hindwings here] that is more easily seen in the smaller damselflies that use a much slower wingbeat.
Here though, because of the angle of the shot, it looks like a helicopter with one blade out of place.
Darter Dragonfly [PK76941]