They damage wood at the larval stage for food. Once they turn adults, they eat their way into the wood and leave back holes that damage your furniture over a long period of time.
If you spot any such holes in your wooden furniture, it is your first clue to a wood-borer infestation. You will also see a lot of wooden frass (powder) that keeps falling through small holes in your wood. This is yet another sign of infestation.