The four-spotted skimmer is a circumpolar species and can be found in Europe, Asia, northern Africa, and North America. In Europe they are called the four-spotted chaser and some develop much larger wing spots at the base of the hindwing then those in North America.
Four-spotted skimmers are ambush style hunters. They usually have a favorite perch or two from which they will hunt, often coming back to the perch to feed or try again. This makes them a good dragonfly to photograph. Males and females both look the same so I am not sure which these are.