By Helen Briggs BBC News science reporter

The elephant hawkmoth (Image: Roy Leverton, Butterfly Conservation)

As we reach the moth trap, bathed in bright white light, they are suddenly everywhere; in my hair, crawling down my neck. The moths skip and dance around us, attracted to the mercury vapour bulb.

Word has reached us that a rather special moth has been found. But all I can see at the bottom of the Perspex box is a large, dull, brown insect.

Mark Calway, who leads the Berkshire Moth Group, reaches in and gently fishes it out.

"An elephant hawk-moth," he says, and the small group of adults and children that have gathered around him move in closer.

He turns the moth over. It is nothing like the brownish creature of first glance. Its beautiful deep pink wings, edged in iridescent green, would put even the brightest of butterflies to shame.

'Beautiful creatures'

It's the evening of National Moth Night and Day, and I've joined some of Britain's army of amateur naturalists who are taking part in the country's largest survey of moth species.

Grahame Hawker (left) and Norman Hall

Among them is Grahame Hawker, one of the organisers of tonight's moth hunt at the Maiden Erlegh Local Nature Reserve in Earley, near Reading.

"To get a bunch of creatures together and name them - there is a human instinct for that," he says.

"But you are dealing with beautiful creatures - they've got beautiful intricate markings, fabulous colours and the closer you look the more beautiful they are."

'Fantastic shapes'

Our walk takes us past several traps set up around the reserve's meadows, woods and lake.

Fifty-three-year-old Nigel Parsons has come up from west London for the occasion. Originally interested in butterflies, he has recently become a moth convert.

An elephant hawkmoth (right) is among the catch

We stroll through the wild flower meadow, where the air smells of wet grass and smoke from a distant barbecue. When we reach the trap, a man with a torch strapped to his head looms out of the shadows.

Norman Hall, who has been studying moths in England, France and Spain for the past 30 years, takes egg boxes out of the bottom of his trap and taps the moths clinging to them on to a sheet spread over the grass. Then he lifts each moth gently on to his finger for identification.

"This is the hearts and darts," he says, pointing to a moth with a little heart and a little dart on each wing.

He writes each species down in a notebook, the Latin name next to the common English name.

As he works, more people appear - parents with young children excited at being up so late; a group of surly teenagers who have been getting up to goodness knows what in the woods; members of the Earley environmental group conducting a survey of local wildlife for the parish council.

Their enthusiasm is infectious: I'm starting to see what all the fuss is about.

Moth 'addiction'

Hawker takes me to meet Susan Nicholls, aged 51, from nearby Caversham, who has set up a sugar trap on the edge of the lake. We examine a sheet of wood smeared with an enticing treat for moths - half a pint of beer, a kilo of molasses sugar, a tin of black treacle, and rum, all boiled together.

It's an addiction; there is so much to learn Susan Nicholls

"By the end of 20 minutes I was hooked," she says. "I could only think this is what I want to do."

Nicholls now sets up moth traps in her garden and rears caterpillars in her kitchen. She is particularly fascinated by metamorphosis, the point at which an adult emerges from its chrysalis.

"It's so magical I just want to keep on doing it," she says. "It's an addiction; there is so much to learn."

Threatened habitat

Moth hunting had its heyday in the Victorian era, when collectors went out to beat caterpillars down from the trees.

Since then, many British moths have become extinct, from the gypsy moth, last seen in around 1907, to the Essex emerald, which disappeared in 1991.

Hawker, aged 46, remembers seeing the huge hairy caterpillars of the garden tiger moth on his journey home from school.

"Every kid knew them," he says. "They used to be called the woolly bear. But they haven't been seen for a very long time around here."

He blames the loss of the British countryside, and modern farming methods that have turned ancient flower meadows into green deserts, where moths and butterflies cannot breed.

"The countryside should be mauve, yellow, cerise," he says. "It should be everything but green."