While initial damage from carpenter bees is limited to a small nesting hole, that hole is likely to be expanded by subsequent generations. Over time, structural damage may occur as the bees branch out into new and larger tunnels. Since these expansive structures are hidden, identifying a problem can be difficult. Keep an eye out for bare, weathered or unpainted wood areas and holes or indents that appear to be perfectly round. Additional identifiers include fresh sawdust and a humming sound from within the wood structure.