The debris from carpets can collect in the joints between floor boards, edges of skirting boards and in the floorspace under a floor which has had carpet coverings over the years. The amount of material here can be quite substantial and provide the protein required by these animals. Also wool type insulation etc in lofts is a possible source. They must be getting sustainence somewhere in your house, so give it some thought. Ask yourself where? What sort of furniture do you have and do you have any animal skins around etc, etc...........use a SUITABLE insecticide once you think you are onto the little blighters.