Yesterday we had a customer from Raleigh, NC who had some house plants that were not only covered in odorous house ants, but there were also many tiny puffs of what looked like cotton on the plants stems and leaves. These tiny puffs of cotton were actually mealybugs.
Mealybugs are common to the Raleigh Triangle area and are very similar to scale insects. They suck juices from the plants (causing the leaves to yellow and die), and in the process they secrete honeydew, which attracts the ants. In return for the honeydew, the ants gather around the mealybugs in order to protect them from natural predators such as ladybeetles.
Mealybugs are not hard to get rid of. It may be as simple as wiping the leaves with a wet cloth whenever you see them. If they keep coming back, you could try an insecticidal soap or a pesticide labeled for houseplants. If the ants continue to be a problem, then you may need to call in the professionals.