YORK'S flooding problems may deter some people from setting up home too close to the city's riverbanks.

But others appear to find the low-lying land that borders the temperamental waters of the River Ouse a perfect des res.

It has been known for several years that York has its own special beetle - and nobody is quite sure why.

The tansy beetle is rather like a large ladybird, except it is bright iridescent green, and it lives on tansy, a wild herb common to riverbanks all over the country.

Everywhere else the beetle has declined until it is almost extinct, but in York it is thriving and on the increase.

The secret of its success in North Yorkshire could be on the point of being revealed, thanks to the work of a York university student.

Duncan Sivell, a PhD student, has been studying the tansy beetle. He is going to give some of his answers to the puzzle at the Royal Entomological Society's post-graduate forum, which is being held next Wednesday at the University of Leeds.

"We think it may be something to do with York's riverbanks flooding," suggests Duncan.

"It's not that the beetle likes water - it's a leaf beetle - but that flooding disturbs the ground which encourages the plant. We also think flooding may discourage the beetles' predators."

Duncan has finished his PhD, but another post-graduate student is going to take over the quest to answer the question: Why does the tansy beetle choose York?

Updated: 11:05 Wednesday, October 08, 2003