I suspect this was caused by an accidental hacking of the ants's signalling mechanisms, caused by freezers not existing in the ants's natural environment. Normally when an ant gets harmed it releases order telling other ants to stay away, but when an ant gets frozen it doesn't get a chance to indicate that it's harmed (actually, it might not be - we didn't try unfreezing the ants to see if they still worked).
My thought is that one could use this effect intentionally. If there was a custom-built freezer with a line of ant pheremone leading into its entrance, it could immediately attract the local ant colony, then lead them all into a black hole until the colony was depleted of resources and died.
Anybody know if this has been tried before? For that matter, anybody know what the mass of all the ants in the local ant colony is likely to be? I can pretend to know the typical size of an beehive, but not an ant colony.