During a walk, I found a young tree that is completely infested with an odd bug. The tree is completely dead. Hanging from the branches are threads, at the end of the threads there are what looks like tiny (up to 1 inch long) dead leaves, or tiny pieces of bark. Upon further inspection, I noticed that these little dead leaves/bark pieces were actually moving all over the tree bark and the ground. Looking even closer one can see that the leafy things are actually little houses for a small black worm-like organism. These creatures have already spread to the next tree. What are these bugs?