@Scrwd why use a nuke when you have superhumans that can do it? Also, their greatest strengths are the blast wave and the fallout, both things an underground ant colony wouldn't care about.
@Scrwd It was stated early on that normal weapons and tools don't work at all on things inside a dungeon, both the monsters and the terrain. Only Hunters and their weapons are effective. A nuke would do basically nothing, and that's assuming they wouldn't see it coming and shred it before it could even detonate.
@optiso drop a couple nuclear bunker busters in the same place over time
the first one will kill the ones on the upper levels and soften the ground
the second will penetrate deeper and move more dirt
the third will go even deeper because of the previous 2
then again in my opinion it would be easier to find all the exits and seal then then activate a bunch of Thermobaric bombs which would kill the oxygen in there and ants cant take heat so it wont be long till they either suffocate or
at least for the ones closer to the surface you can also just go in with flame throwers if they have many exits and shit (burn em out like the japanese)