After examining the behavioral patterns of insects Chinese scientists have successfully developed a series of techniques to prevent the little creatures from damaging the Dunhuang grotto frescos, solving one of the biggest difficulties in protecting the ancient cultural treasures in west China's Gansu Province.

Scientists started the study by examining the ecology and biology of the caves. According to Wang Wanfu, deputy director of the Conservation Institute of the Dunhuang Research Academy of China, insect pests are the most common and serious problem facing the protection of the cultural relics. In recent years, insect damage to outdoor and indoor frescos, cultural relic collections in museums and ancient wood buildings has become increasingly obvious, and in some cases has resulted in substantial losses. In order to tackle this problem, the Dunhuang Research Academy has cooperated with many experts from Dunhuang Forestry Technology Promotion Center and Gansu Agriculture University to study the categories and distribution of insects and examine how they damage the frescos and the Dunhuang grottoes. After many experiments scientists have worked out a series of effective preventative measures.

The study shows that insects living in the Dunhuang grottoes can be divided into six categories including anopheles, white mosquitoes, houseflies, blowflies and other two kinds of night moths. The researchers found that adult insects hit the frescos while flying, causing the already loose surface of the cave paintings to peel off. When the scale-like bits and excrement of adult insects drop onto the surface of the frescos it can cause serious damage. Even more serious is the moisture and organic matter in the excrement of insects which together with the pigment contained in the frescos results in a chemical reaction leading to fading color, color changes and even decay.

Experts have proposed complex preventative measures combining physical and biological techniques. The physical preventative measures involve the setting up of apparatus like doors, windows and screens in the caves to catch and kill groups of insects; and the luring of eclosion insects to their death with 20 watt black light lamps, taking advantage of an adult insect's positive phototaxis. These measures are found to be simple and effective. The biological preventative measures include disrupting the insects' habitats; clearing away host flora; fostering their natural enemies and spraying specially mixed larvicide during the first ten days of June. These measures are proving to be effective in reducing the numbers of insects over the longer term.

Experts point out that the various preventative measures referred above must be used according to particular situations and on the grounds that avoiding damage to the grottoes, fresco and ecosystem is the first priority.

(china.org.cn by Wang Qian December 11, 2002)