Eyes can be a useful clue in dragonfly identification. Nearly all dragonflies in the UK have a degree of contact between the eyes however the Golden-ringed Dragonfly photographed here by Jan Shields at Carding Mill Valley really pushes this point to the limit! Here the striking green eyes literally just about make contact coming together at a single point. The only exception to this rule in the UK is the Common Clubtail which is easily identified as the eyes are clearly separated on the head with no point of contact.
And just to complete the picture, damselflies all have a very different head shape with eyes clearly separated and positioned on the sides of the head.