Flooding is threatening a unique insect known as the ‘Jewel of York’. STEPHEN LEWIS reports on efforts to save the tansy beetle.

YORK’S Landing Lane could do with a new name. For a couple of months in spring, it might be better known as Lover’s Lane, judging by the number of amorous couples to be found there.

Not hormonal teenagers, thankfully. These lovers are only about the size of your little finger.

April to June is usually the breeding season for tansy beetles. If anything, they’ve been a bit late this year, because of the cold spring.

But on a recent weekday morning they were clearly out to make up for lost time. There were scores of them, locked in passionate embrace on fronds of grass or the fern-shaped leaves of the tansy plant itself.

Look carefully, and you could even find their eggs.

“There’s some,” said biologist and beetle expert Geoff Oxford, parting some green leaves carefully. “They look a bit like butterfly eggs. They stand up on end.”

The tansy beetles at Lovers Lane – sorry, Landing Lane – are clearly in rude health. But appearances can be deceptive.

This beautiful beetle, known locally as the ‘Jewel of York’ for its flashing, iridescent green-and-bronze body, is found in only one place in the UK: along the banks of the River Ouse in and near York.

Despite continuing efforts to save it, numbers are declining here and elsewhere in the world where it is found, from Scandinavia to the Mediterranean.

Dr Oxford, a retired University of York academic, has some startling figures to illustrate the decline.

In summer 2011, he surveyed a short stretch of the River Ouse near Beningbrough as part of an annual count of beetle numbers, and found 950 tansy beetles.

Last year, along the same stretch of the river north of York, he found only nine.

There had been a catastrophic slump in only 12 months.

He knows exactly why: the floods which hit the area last June. That is when the tansy beetles’ eggs have hatched, and the young larvae are feeding voraciously on the tansy leaves which are their only food.

Because the tansy plant is now found mainly along the edge of the river, when the floodwaters rose the feeding larvae drowned. Virtually the whole population along this northern stretch of the river was wiped out.

Some people ask why this is such a problem, Dr Oxford says. They point out that the River Ouse has always suffered periodic flooding. If the beetles survived in the past, why can’t the population recover this time?

He has an answer to that.

“Decades ago, the land away from the river was probably less intensively farmed, and there may well have been tansy plants further inland. It is now pretty much restricted to a thin strip along the bank.”

This makes the beetles desperately vulnerable to flooding.

The collapse in tansy beetle numbers along that northern stretch of the Ouse doesn’t provide a complete picture, thankfully.

In areas such Landing Lane, which did not flood so badly, the numbers remain good. And in other areas – such as on the banks near Acaster Malbis – the number of tansy beetles increased from 2011 to 2012.

But overall, an estimated 2011 population of about 4,800 in and around York – the entire UK population, don’t forget – had fallen to about 2,700 by 2012.

August, when the tansy larvae emerge from their pupae and begin to feed, is when they are particularly vulnerable to flooding.

“So if we get another season of floods like last year, it could be the end of the tansy in Britain,” Dr Oxford said.

You might wonder why we should be worried. Well, the tansy beetle is a beautiful, unique creature – and once it is gone, it is gone, says City of York Council countryside officer Bob Missin.

“You could say why bother about anything? Why do we bother to protect the tiger? They are species which are endangered, that is why. The tansy beetle is beautiful, and it is a bit of wild Britain.”

Dr Oxford agrees that the prime reason for protecting the tansy is because it is worth protecting. But there is another reason for protecting the beetle – along with as many other endangered plant and animal species as we can, he says. We never know when they might prove to be useful.

Take the harlequin ladybird, for example. Widely regarded as a pest since invading Britain, German scientists found a couple of years ago that a sticky, blood-like substance produced by the insect could kill a range of germs, including tuberculosis, MRSA and malaria.

“So it is very dangerous to think that we will only keep things that we can use,” Dr Oxford said. “We don’t know what we might be able to use in future.”

In order to try to save the beetle in the UK, a tansy beetle action group has been set up.

The group – which has the catchy acronym TBAG – is made up of representatives from the University of York, City of York Council, North Yorkshire County Council, the Environment Agency, the National Trust and insect charity Buglife, as well as lots of willing volunteers.

It surveys the beetle’s numbers every year; plants new tansy plants to try to encourage more beetles, and cuts back trees and other shady plants that stop the tansy growing.

Where tansy plants are at risk of being grazed by cattle – such as along the river near Beningbrough – enclosures have been built to protect the plant, and thus the beetles who live on it.

A few years ago, Dr Oxford, a member of TBAG, helped introduce the beetle to the banks of the River Ouse along a stretch north of York, including at Beningbrough, where it flourished until last year’s floods. And more recently a number of tansy ‘Arcs’ have been set up away from the river’s flood plain – including at Museum Gardens – where beetles were released into specially created habitats.

Among the volunteers out last summer helping to plant tansy plants was the then First Lady of York, Karen Hyman.

She was part of a field trip to Fulford to look for the beetle and plant tansy plants.

Despite such high-profile help and the obvious goodwill of volunteers, however, Dr Oxford admits that he won’t rest easy until a tansy beetle population is established somewhere other than York and the River Ouse.

He hopes that one day soon, a population can be reintroduced at Wicken Fen, in Cambridgeshire, where it was once found. The beetle was last recorded there in 1981.

Re-establishing it there would mean the UK population was much less vulnerable to flooding along the Ouse.

“If we can get them down there, I will breathe a huge sigh of relief,” he said.

A year in the life of a tansy beetle

• April-June: adults mate and lay eggs
• May-July: eggs hatch into larvae, which feed on the tansy plant
• July: the larvae burrow underground at the base of tansy plants and turn into pupae
• August: the pupae hatch as young adults, and can be seen on tansy plants until September.
• September-April: the young beetles burrow underground and spend the winter there until April and the new breeding season