Small Black Ants
There are many species of ants that can become a nuisance in homes. They are attracted to food odors and even moisture sources. Clean all areas where ants gather. Check for routes of entry and improve the caulking and weatherstripping around windows, doors, and utilities to prevent entry (do not discount blocking off points of entry - caulking).
If this does not work try baits.
Ants are attracted to different baits at various times of their lifecycle. Sometimes they are attracted to sugars and sometimes proteins. You can try an ant bait with the active ingredient boric acid and a sweetener. If this does not work try another type such as a gel bait. There may be several manufacturers and may come in a syringe type tube. You can place pea sized baits of gel in areas of ant activity or along points of entry.
Do not clean up around the baits as ants have trails that they follow to and from the nest. Watch the ants as they come and go and may help determine if coming from inside or outside. It is not always possible to determine the exact location of a nest especially if they are between floors, behind baseboards, etc. For more information on ants see our publication http://extension.umd.edu/sites/extension.umd.edu/files/_images/programs/hgic/Publications/HG7_Ants.p...