Many types of insects feed on and make their home in wood. Beetles, moths and wasps are the most common types. Most insect borers are "secondary invaders" or are attracted to wood that is already weakened, damaged, or dying. The insect’s presence usually means the tree is already in poor health. Wood boring insects produce sawdust like frass (excrement). Their holes are usually round and are scattered in a random pattern across the wood. Wood content must be over 30% moisture content for insects to thrive. Pin wormholes are wormholes that are smaller than ¼" in diameter.