Effective elimination relies on understanding the feeding and social behavior of the ants that have invaded. As examples: if a bait is placed in an area where the they don’t travel, or it consists of a food ingredient to which it is not attracted, the bait will do little except collect dust. If inspection is conducted outdoors for the colony of an indoor-nesting ant, the time will be spent in vain. If only a single colony of a multi-nest ant is found and treated, the infestation is unlikely to be eliminated.
Even within a species, complexities can arise. For example, the pavement ant often will nest under sidewalks and driveways in temperate weather — then move indoors during the winter, nesting under the foundation or near a heat source. They also can have seasonal variations in food preferences, with many foraging for proteins in the spring as they work to build up the colony, then preferring more sugar/carbohydrates in the summer and fall.
Baits are the most effective form of treatment for the majority of ant species, especially those which invade structures.* This is because the worker ants will feed on the bait — which contains an attractant and an insecticide — and carry it back to the nest to share with other colony members, including the reproductive queen. They are able to do this because they have two stomachs — one which holds the food for its own consumption, the other for the food that is to be shared with other ants through trophallaxis, e.g., regurgitation.
While some ant species are monomorphic (having all its workers of similar size), others show the evolutionary trait of polymorphism (having workers of varying size). This variation enables a division of labor. Some species, for example, have soldier ants, which are large, sterile females with strong mandibles, enabling them to defend against predators as well as to crush food sources, while the bite of the smaller worker is better suited for cutting.
For a bait to be most effective, access to alternate food and water sources needs to be reduced as much as possible. This means maintaining a sanitary environment, cleaning up spills and crumbs, keeping garbage emptied, repairing leaks, eliminating equipment harborage areas, etc. It also is important to understand that bait does not take effect immediately, but it is a long-term solution. While it can take a week or two to stop seeing ants, the feeding of the bait to the colony and queen enables complete kill of the ants that you don’t see, instead of just the workers that you do.
*Although bait is generally the best choice for controlling ants, applicators need to always ensure the specific application is listed on the label and allowed by the food plant’s third-party audit standards, and that the bait is on the approved products list before any applications are made.