蠹 is the woodworm that eats books and timber.
韩非 names five kinds of people who eat a state away from inside: Confucian scholars, persuaders who trade in alliances, private swordsmen, men who escape army service through powerful patrons, and merchants and artisans. His point is that times change, so a ruler who governs by the ways of the ancient kings is like the farmer of Song waiting by the stump for another rabbit.
