what are those holes in my trim?
Small areas of dirty looking sawdust on the siding right underneath trim boards and holes in trim boards are the calling cards of carpenter bees. The excerpt below is from an article published by the University of Kentucky and explains why carpenter bees are boring into your house. The full article can be found at: https://entomology.ca.uky.edu/ef611.
Female carpenter bees bore into wood, excavating a tunnel to lay their eggs. The entrance hole in the wood surface is perfectly round and about the diameter of your little finger. Coarse sawdust may be present below the opening, and tunneling sounds are sometimes heard within the wood. After boring in a short distance, the bee makes a right angle turn and continues to tunnel parallel to the wood surface. Inside the tunnel, about five or six cells are constructed for housing individual eggs.
After the bees lay their eggs, woodpeckers come and peck at the trim boards to expose the larvae. The holes from woodpeckers are usually the damage that is noticed. The photo below shows the damage from carpenter bees and the resulting woodpeckers on the fascia of two dormers.
Unfortunately, carpenter bees return to the same area year after year for hibernation. Their tunnel networks are extensive, and woodpeckers do not always get to all of the larvae. Replacing the boards with new wood will repair the immediate damage, but the bees will typically begin boring into the new wood.