Ant invasions usually start with a few lone ants striking out to find a food source for the rest of the colony. Sometimes if you can see a few lone ants in your house you might be able to stop an invasion before it gets really established in your home. Those scout ants mark a scent path to the food and then return to the colony. That scent trail leads other worker ants straight to the food source, and the food source is your home.
Soon larger numbers of ants will follow that trail to the food. One way to interfere with ants who are trying to invade is to destroy that scent trail.
Identifying the Entry Point
An ant's scent trail usually becomes first noticed inside a home through a cracked area in a wall or floor. It may also be first visible from a baseboard along the floor. Other entry points might be unsealed holes to the exterior, including plumbing entry points. Usually, the trail continues in a fairly straight line towards a food source. Often the food source is an area of crumbs or a sticky spill. It might also be a pantry, food cabinet, or even a small appliance with food residue. Outside scent trails can lead to the same types of items or even dead bugs.
Finding the Ant Scent Trail
An ant scent trail is invisible to humans. There is no way to see the trail that has been left unless the ants themselves are present and following the trail.
The easiest way to see a scent trail is to watch the ants traveling in a line. Very rarely will a few ants break off from the line to scout new food sources. Early on in an invasion, the unbroken line to the food will mark the pathway of the scent trail. By following it, you may find the reasons the ants are coming, where they are coming from and how to stop them.
What to Do When You Find the Trail
If you see a group of ants in your home you may be able to follow the trail out to where the ants are coming in. Instead of just destroying the entry point, be sure to clean the trail the ants traveled along to avoid having the same issues. Vinegar, a diluted bleach solution, and peppermint essential oil diluted with water in a spray bottle are just a few options to remove the ant scent trail. Many of these will kill the ants along the trail as well. You'll have to wipe up the dead ants and the solution that you use. Dry the area thoroughly and keep an eye on it for the next week or so.