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)