All dragonflies and damselflies have long bodies, plus two pairs of densely veined wings. These insects often brightly coloured. In general the dragonflies are large and chunky. Adult dragonflies are large insects. The biggest British species has a wing span of about 10 cm, and a body length of about 8 cm. They have huge eyes, occupying most of the globular head. They rest with their wings stretched out. In contrast damselflies are much smaller. They have a relatively weak fluttering flight, frequently resting on vegetation. When at rest they tend to fold their wings. The eyes of damselflies are also smaller and have a different position on the head.
Together dragonflies and damselflies belong to the order of insects called Odonata (meaning ‘toothed jaw’). The Odonata are a remarkable group, with about 5500 species in the world today. Although still common and widespread today, they were among the first flying insects to appear on earth. Indeed, fossils of dragonfly-like insects occur in Carboniferous rocks over 350 million years old.