Carpenter bee damage is usually only seen on just the surface. Soft unpainted wood is usually the first target of the female. Painted surfaces can help detour carpenter bee burrowing. They are especially attracted to cypress, pine, and cedar wood. The whole that you see is just the beginning of the destruction caused by carpenter bees. The female burrows straight into the wood then take a hard left or right. The hole can be from 6 to 8 inches deep. The main tunnel can branch off into several smaller ones shared by multiple bees. 

Once the hole is burrowed the female creates chambers by depositing an egg then packing food supply in front of it. It will then seal it off & repeat the process. Usually there are 6 to 8 chambers created by each female carpenter bee. The larva will hatch from the egg and eat the food source provided in the chamber. The adult carpenter bee emerges approximately 3 months later in late summer. They will gather and feed on pollen and nectar, then return to the tunnels to spend the winter. Sometimes the very tunnels they emerged from. In spring they will emerge and start the cycle all over again. This is why people seem to think they return every spring to the same place. They aren’t actually returning they were already in the tunnels and are just emerging in spring. 

Over time the tunnels will be added to and sometimes widened. Over several years the tunnels can reach lengths of 10 to 12 ft deep. The face of the wood can sometimes weaken and chip away exposing large hollow chambers. The damage over time can be devastating to the structure. Sometimes woodpeckers and other animals will peck or open up the wood to get at the carpenter bee larva, which make a great meal.