Somewhere in Poland, there is an ex-Soviet nuclear bunker which was sealed off for radiation. There was a ventilation pipe in which ants would fall down and then become cannibals.

The queen-less colony of worker drowns was about a million strong.

In 2016, they did an experiment, where they installed a wooden board to let them back out to see what would happen.

(I can only assume they did not watch enough trashy c-tier horror flicks, or any kaiju monster flicks, because this is how the world ends. )