later on, in the context of consolidation treatment. Discolouration of mineral
pigments due to excretion of organic acids has already been considered.
Interaction of microbes and faunal elements. Besides the stimulatory and
competing interactions between different microorganisms, coexistence of
microbes with faunal elements like mites, springtails and even mosquitos can
be observed by means of microscopy, especially scanning electron microscopy.
Faecal pellets, eggs, silk and exuviae sampled from wall paintings have been
shown to be usually infected by fungi and bacteria. Despite the well-known
symbiotic interactions between arthropods and fungi within guts, little or no
investigations have been done to assess other possible impacts.
As for the animals, they may feed on microbes directly or may use micro-
bial enzymes for digestion purposes. The microbes, however, may profit by
the fact that they can be transported over relatively long distances and thereby
colonise large parts of the paintings, as long as the animals are mobile and carry
the microbial cells on their body. Some of them, however, may also be trans-
ferred after passing through the insect digestion system.
For example, flies may already be infected by fungi while still alive and
mobile; dead individuals with spore-bearing conidiophores growing from
their body have been observed. Some mosquitos sampled from wall paintings
(Kodersdorf crypt of a parish church, dating back to the eighteenth century)
immediately after dying did not prove to be infested (see Figure 6) but later,
however, the exuviae were completely overgrown (see Figure 7), especially
by the fungus Verticillium.
Although some species of the genus Verticilliumhave been described that
grow on chitinous substrates (important components of the insect exoskeleton),
Wall Paintings: Aspects of Deterioration and Restoration 253
Figure 6SEM of sample from Kodersdorf, Germany, mosquito body without infestation