Most xylophagous animals are
arthropods, primarily
insects of various kinds, in which the behavior is quite common, and found in many different
orders. It is not uncommon for insects to specialize to various degrees; in some cases, they limit themselves to certain plant groups (a
taxonomic specialization), and in others, it is the physical characteristics of the wood itself (e.g., state of decay, hardness, whether the wood is alive or dead, or the choice of
heartwood versus
sapwood versus
bark). Many xylophagous insects have
symbiotic protozoa and/or
bacteria in their
digestive system which assist in the breakdown of
cellulose; others (e.g., the
termite family
Termitidae) possess their own
cellulase. Others, especially among the groups feeding on decaying wood, derive much of their nutrition from the digestion of various
fungi that are growing amidst the wood fibers. Such insects often carry the
spores of the fungi in special structures on their bodies (called "
mycangia"), and infect the host tree themselves when they are laying their eggs. ==Examples of wood-eating animals==