THE Beautiful Demoiselle, the Azure Hawker and the Green Darner: with names as beautiful as they are, who wouldn't want a dragonfly whirring round their garden?

But, the British Dragonfly Society is warning, if we don't do something to help them soon, the Downy Emerald, the Vagrant Emperor and all their other iridescent, hovering chums could soon be no more.

A third of Britain's 39 species of dragonfly and its close relation, the damselfly, are threatened because of modern agricultural techniques and loss of their important habitats.

In the last 40 years alone, three species have already died out.

Brian Edwards is a surveyor with the Dorset Environmental Records Centre and he says that dragonflies thrive where there are plenty of bogs and clean ponds where they can breed and grow underwater.

"They need plenty of emergent vegetation by the side for them to use to walk out of their watery world," he says.

"They also love hedges too.

"They patrol them looking for insects to eat and use them for shelter in rainy weather."

To try and preserve these habitats, the British Dragonfly Society is launching a five-year project to keep an eye on dragonfly areas, producing a Dragonfly Atlas showing where they live and preserving their favourite haunts.

Conservation officer Katherine Parkes says: "Understanding when and how our dragonflies are moving will help us to plan for the future."

According to Bryan Edwards, Dorset is well-off for dragon and damselflies.

In fact, he says: "This county is one of the best places to spot them," especially the Southern Damselfly, which is specially protected by European legislation.

Top areas include all heathland and the Purbecks.

"They love the boggy bits and the little clay ponds provide a great habitat for them to breed and live and so do the former quarries," says Bryan.

"Any areas of unpolluted still or running water, like a garden pond, are good for them too."

It's hard to believe that anyone would wish any harm on these fascinating creatures, but, says the Dragonfly Society, they have been the victims of all kinds of unhelpful myths and old wives' tales. An old name for damselflies was Devil's Darning Needles or the Devil's Bodkin.

This stems from an old myth that if you went to sleep by a stream on a summer's day, damselflies would use their long, thin bodies to sew your eyelids shut!

The society is keen to point out that there's no truth in that, just as there's no truth in the idea that they were called "horse-stingers" because they attacked horseflesh.

"This name may come from the way a captured dragonfly curls its abdomen as if in an attempt to sting," says the society.

"Another possible explanation of this name is that the big Aeshnids were often seen flying round horses in fields.

"They were actually feeding on the flies attracted to the horses but occasionally a fly would irritate or bite a horse enough to make it twitch or skip about.

"People seeing it made the inference that it was the dragon, being big and obvious, stinging, rather than an unseen fly biting."

Dragonfly bites are nearly as rare as dragons themselves; they prefer to feast on insects, which is why wet summers like the one we had last year are so devastating for them because, says Bryan Edwards, "their prey doesn't fly and neither do they".

However, they do not, as another popular myth suggests, live for only one day.

Most of their time is spent in larval form and their lives may last anything from six months for some species, to six years for others.

As for the biggest dragonfly question of all, how they got their name, no one is too sure.

The Dragonfly Society says: "We think the earliest reference to the name is from Francis Bacon's Sylva Sylvarum: or a Naturall Historie in Ten Centuries.

"This book was published in 1626, where he first used common name Dragon-fly'.

"At a guess, Bacon had picked up on a common, folklore name in use at the time."

Preserve them all by visiting the Dragonfly Society's website dragonflysoc.org.uk and sign up for the Dragonfly Atlas.