Larger Yellow Ant
The larger yellow ant, a common ant species found throughout Iowa, is also called the foundation ant. Normally these ants live outdoors in old logs and stumps and under stones. The workers are observed indoors on relatively rare occasions. The workers feed almost exclusively on honeydew gathered from aphids or mealybugs and they are active at night.
Pest problems with larger yellow ants usually occur in the late summer and fall when mixed colonies of winged swarmers and wingless worker ants move toward buildings and try to enter through cracks or gaps in the foundation. The temporary indoor, winter nest is usually somewhere in the basement under a loose brick or board or in a crack in the wall or floor. The ants do not forage for food through the house and apparently cause very little damage except to create piles of dirt at the entrance to the nest. Reportedly, these ants try to return to the outdoors sometime in the early spring if left undisturbed.
Control of larger yellow ants is not critical, since they cause little damage other than the annoyance of their presence. Ants found indoors in the winter can be vacuumed or swept up and discarded. If their temporary nests are located, these can be sprayed with an indoor ready-to-use insecticide labeled for use against ants. For more information on insecticides please see this article.