That fleeting glimpse of gemstone colour as a dragonfly darts past in summer is also a peek into pre-history.

From fossil records of some two million years ago, we know that dragonflies sported a wing span that could have been up to 75cm. Although today’s largest of the UK’s 34 species, the brown hawker, has a wingspan that is some seven times smaller, the basic design has remained largely unchanged. Many native species can be seen in Dorset throughout the summer, especially along the rivers Frome and Stour or around heathland ponds and disused clay pits.

And while the size may not be as impressive as its earliest ancestors, today’s dragonfly can attain a very creditable maximum flight speed of some 25-30 mph, which perhaps gives rise to some of the common names, such as ‘darters’ and ‘skimmers’.

The subject of much myth and legend, the dragonfly has been both praised and derided in almost equal measure. Legend claims that Japan was once known as the ‘Isles of the Dragonfly’ after an Emperor saw one catch and eat a horse fly that had just stung him. Others insist that they bite and sting, perhaps leading to folk names that include ‘horse stingers’, ‘devil’s darning needle’ and ‘devil’s riding horse’ – none of which truly describes their characteristics.

Their Latin labels give more practical clues. Along with damselflies they are members of the order odonata, which means ‘tooth jawed’ and accurately describes their serrated mouthparts. Their infra order name, anisoptera, indicates their ‘unequal wings’ as the back wings of dragonfly are broader and shorter than the front. Unlike the ‘yoke winged’ damselfly (Zygoptera), dragonflies are strong flyers, both near and away from water, and can be easily distinguished from their smaller relative by their larger size and usual habit of resting with their wings stretched out as if ready for flight. The weaker-flying damselfly will stay close to the water surface and margins of rivers, streams, ponds or other inland water areas.

Slightly longer lived than is often assumed, the dragonfly has two distinct life stages after the eggs are laid in water – larval and adult.

In Britain the dragonfly can live for two months as a free flying adult, but the damselfly usually for only a couple of weeks. A poor summer will mean heavy losses through starvation, as neither they nor their prey (midges, mosquitoes, butterflies, moths) can fly in stormy wet conditions.