Baits work on ant colonies with visible and non-visible mounds, such as newly established colonies.
The active ingredient is passed around from one ant to another and it eventually reaches the queen and the brood. The insecticide's active ingredient acts slowly. This gives the worker ant time to bring the bait back to the nest before it dies. An insect growth regulator as the active ingredient in a bait doesn't kill worker ants. Baits containing an insecticide will generally give noticeable reductions in fire ant workers in a couple of weeks.