Question / What are those patterns on dead wood?

Q: Have you seen this kind of pattern on tree branches or trunks? What are they called?

A: These patterns are called an insect gallery. The trails are created as larvae eat their way through the cambium layer of the tree. The normal passerby will likely see these galleries on dead branches and trunks of trees. They're absolutely gorgeous, and somehow, they also give me a bit of the shivers.