What is a strong indication that an ant colony is inside a building?

Observing inside swarming is a strong indication that an ant colony is inside a building because it typically signifies that the colony is reaching maturity and that it's reproducing. During this process, winged reproductive ants, known as alates, leave the nest to mate and establish new colonies, which often occurs inside structures. The presence of these swarms is a clear signal that the ants have established a thriving colony within the building, as they choose sheltered environments conducive to their growth and survival.

While visible nests in walls can also indicate a colony's presence, it is not always visible to an untrained eye. Frequent road traffic and no signs at all do not relate directly to the presence of an ant colony inside the building, as traffic patterns have no connection to ant behavior or habitation, and a lack of signs would suggest there is unlikely to be an infestation. Therefore, inside swarming provides a direct observation of the colony’s reproductive activity, confirming its presence.