I found a carpenter ant (large black ants) complete with eggs under a toilet between the sub floor and a 1/4" plywood fastened to the top. The ants had burrowed between. I have eradicated the whole nest and removed the wood. How can I insure that there are not any other nests in the house. Is there are bait or other way to look for other nest(s). Can we use AMDRO bait to eradicate the ants in the house? Any advise would be greatly appreciated.

Check your subfloors for dampness. Carpenter Ants prefer softer wood to nest in, and damp wood is softer than dry. Amdro brand baits are moderately effective for Carpenter Ants, but I would recommend a program of treating the perimeter of the building with a 'pass-along' insecticide that the workers carry back to kill the larvae.