The paddle-tailed darner is one of a confusing group of very similar dragonflies that are often lumped under the term 'mosaic darners.'   Paddle-tailed darners resemble the more common blue-eyed darner but have less intensely blue eyes and some other subtle differences, including the paddle-like tail appendages that give them their common name (not clearly visible in most of these images).   I photographed this one at River Springs in Mono County, California (many thanks to Ron and Barbara Oriti for showing us this place, and other good Eastern Sierra dragonfly locations).