The clubtails are a large group of dragonflies, often quite similar to each other.   Hence I'm not 100% sure these are plains clubtails; they could also be the sulfur-tipped clubtail (G. militaris) or possibly the pronghorn clubtail (G. graslinellus).   The photos were taken on the Konza Prairie in northeastern Kansas, where many of these dragonflies defended small territories on rocky areas on sunlit ridges.