If you buy old wooden objects, especially masks and carvings from Africa, they are very likely to show some (or extensive) signs of wood worm or other wood-eating insects, generally holes and small tunnels. Sometimes, a gentle knock on the surface will reveal hollow spots, and the little particles of wood inside will make the object sound like a rattle when you shake it. The bugs themselves are rarely visible, but you can occasionally hear them (especially at night) eating away at your precious objects. The sound will be like a slight and irregular ticking. In that case, the next day you will find a little mound of fine sawdust beside or underneath the object and close to one of the holes or tunnels, which proves that the little devils are alive and active. If you have a fridge with a large freezer (or just the freezer), and you think the object is not too large for it, just wrap it in plastic (a plastic bag will do) and place it in it. You can even lower the temperature of the freezer to make sure it will work. You can leave the object there as long as you wish, but in order to be sure of the result, anything between one and four weeks will do. Little animals from the tropics can be very tough to get rid off, so don't take any risks! Once you have removed it, do NOT place it directly in the sun (you shouldn't do this even if there are no bugs), so that it gradually recovers its room temperature and does not crack. Check the object regularly, lift it from time to time to see if there is any sawdust, and if you DO find it, repeat the operation. If this doesn't work, you should turn to chemicals or consult a specialist. Good luck!