a harmful person who damages a country or organization from within

bark beetle (zoology)

public enemy number one; a major parasite on society or the state

the principle that constant activity prevents decay or stagnation, just as a frequently used door hinge does not become worm-eaten

codling moth (Cydia pomonella)

to cause damage or injury; to endanger

any of several moths of the family Cossidae whose larvae bore into wood

an insect that damages books by feeding on paper and glue

to exploit the state and harm the people (idiom)

to be damaged or eaten by moths or wood-boring insects

(archaic) tooth decay

a person who harms the state or society, typically a corrupt official or traitor who drains national resources

to decay and be eaten by worms or insects

literally meaning that flowing water does not rot and a door hinge does not get worm-eaten; used to signify that constant movement or exercise prevents stagnation and decay

to be worn out

Danger appears where many harmful factors exist.

deep-seated abuses or corrupt practices that cause internal decay within an organization or system

parasitic government

old worm-eaten books