... Defects such as visible decay, insect galleries, splits, checks, and other defects
will sharply reduce the volume and grade of lumber recovered from a given log ...
www.fs.fed.us/pnw/bmnri/pubs/tn8.pdf

obrazek tu:
http://ohioline.osu.edu/b614/f37-40.html
Figure 37. Insect galleries left by the European Elm Bark Beetle. These are common on wood under the bark of trees infected with Dutch Elm Disease.