The darner family of dragonflies can be identified by their large eyes which come together in a long line at the top. Many other types of dragonflies eyes meet only at a single point. Their huge eyes give them the appearance that they are wearing a helmet. Darners are large dragonflies and they are very strong flyers.
These are Canada darners. They are part of a group of darners that are often refereed to as blue or mosaic darners. To distinguish one mosaic darner from another you often have to look at the shapes of the side stripes. In this case the small notch in the middle of the front side stripe as well as the small backward flag at the top of the front side stripe are the field markings that identify these as Canada darners. The pair in the photo below are in the process of mating. All dragonflies mate using this wheel type of position.