What are the biggest threat to Ant colonies?
Probably Anteater colonies. Seriously, the biggest threat to ant colonies historically has been other ant colonies, they attack and test other colonies continuously for weaknesses they can exploit. The rule in the ant kingdom is attack,conquer and eat. -That having been said, the new champion for biggest threat to ant colonies is mankind. With the industrial age came many toxic chemicals the ants have no defense against (agricultural insecticides,industrial runoff, the paving of America-concrete/asphalt,etc.). While ants (and any other creature) attacking a colony can devistate a colony, there are usually enough stragglers surviving to restart a new colony elsewhere. Not so with mans destruction- it is terribly efficient in the colony(s) total destruction.
