After 20 years of being in the pest control business, I still learn different things every day. Ants hide can hide in the tightest cracks and crevices. They can live in wall voids, electrical outlets, and conduit boxes. Ant can cause nightmares for exterminators because of the numerous unseen places that they can hide.
On an early morning in May, after a rainstorm, I was called to investigate an ant problem that one of my customers kept having in the same spot of the home. I have checked and serviced this home more than four times for ants. All bases were covered. Until, my customer called and said some mounds have appeared in the yard along the crevices under the kitchen window. I have checked this area many times. Well, it turned out that the grass along the house boarders was not always grass. What appeared to be a perfect lawn was not the case. I pulled the lawn back like sod and discovered that this use to be an old landscape. Rocks, ground cover, and under the ground cover, the mother load. There must have been thousands of ants.
So if you are having an ant problem, check for ground cover that may have been over grown by grass. You may find a landscape project that may have been forgotten. Perfect dwelling for ants.