They don't breed, but worker ants contribute to the survival of the colony. If all/many of the workers die, the breeding ants would die, too. See http://en.wiki

They don't breed, but worker ants contribute to the survival of the colony. If all/many of the workers die, the breeding ants would die, too. See http://en.wikipedia.org/wiki/Colony_collapse_disorder http://en.wikipedia.org/wiki/Colony_collapse_disorder for worker honey bee disappearance killing the hive (not suggesting any death-spiral/circular milling connection). But yes, a few hundred (or thousand) worker ants dying isn't a strong enough evolutionary signal to matter to the healthy hive.