Colonies of white ants which have been responsible for damaging ancient buildings in Xi'an are spreading across the city, according to a new study.

The Xi'an Institute for Prevention and Control of White Ants said the amount of areas the termites were found active in had increased to 15 percent from 10 percent in 2002.

Lu Xiansheng called out experts from the institute after finding them in his property in the capital of northwest China's Shaanxi Province.

"They were like small moths flying around, and I felt nervous because they had caused damage to my wooden floor," Lu said.

As a capital for 13 dynasties in Chinese history, Xi'an has a large number of ancient remains built from wood, which are under threat from the insects.

The ants eat any wooden materials and reproduce there.

March and April are the period the termites reproduce, according to experts.

Xi'an has suffered a major problem with white ants in recent years.

Gao Lianggang, director of the institute, said the termites had caused more than 15 million yuan (US$1.85 million) of damage annually in the city since the late 1990s.

Among the 24 large and important ancient buildings in Xi'an, 17 have been damaged by white ants. They include the Beilin Museum, built during the Tang Dynasty (AD 618-907), the Dayan Pagoda, which was built some 1,400 years ago, and the Chenghuangmiao Temple, built more than 600 years ago, Gao said.

Before the 1990s, Xi'an saw few such termites but since then, as the climate has become warmer and damper, more have arrived.

Despite great efforts to control their spread, the number of ants has grown quickly in recent years. Between 1995 and 1998, the institute received about 1,000 reports of white ant sightings. But in 1999 alone, it received 3,000.

"The local government and enterprises, as well as residents, should pay more attention to the prevention and control of the termites, and more funds, workers, technologies and facilities should be introduced in the fight against them," said Gu Quancheng, a social and urban development expert from Shaanxi Provincial Construction Department.

(China Daily April 28, 2006)