Rhionaeschna jalapensis
Netta Smith's photo.
Male body length: 66-70 mm.

This darner (hawker) is widespread from northern Mexico to Panama, occurring mostly on ponds and lakes at higher elevation. The blue eyes, narrow thoracic stripes and mostly black abdomen are typical of males, as are the forked cerci (superior appendages). Here is a male that was harassing a copulating pair, attempting to mate with the female. The harassment almost caused the pair to drown, but they were saved by the photographer.
Dennis Paulson's comments.
Rhionaeschna jalapensis