How to deal with ants in wall
You should lay a bait down.  I recommend Advion, which is a product from DuPont or MaxForce, which uses fipronil.  You can do a search on Amazon or a similar site for "Advion ant" or "MaxForce ant". The bait comes in a plunger that you can use to apply in small places.  Find out where they are trailing and put a few drops down.  You can put the drops on paper if you are worried about your finish.  Every day (or couple of hours if you have a bad infestation) check to see if the bait's gone and reapply.  It may take a couple of weeks to kill them all.  

As far as Terro goes, I haven't had much luck with it either.  The attractant in Terro's all sugar-based from my understanding.  The ants may be feeding on Protein now.