bookworm (literal and figurative); book louse; pedant

traitor; public enemy

bark beetle (zoology)

public enemy number one

to decay and be eaten by worms etc; to overhoard grain so that it rots

to be worn out

sinecurist

(archaic) tooth decay

lit. a door hinge never becomes worm-eaten; constant activity prevents decay (idiom)

lit. flowing water does not rot, nor a door-hinge rust (idiom); fig. constant activity prevents decay