Termites are endemic in California. Houses that are sold here are typically tented for termites during the period after the seller moves out and before the buyer moves in.
Ants are endemic in California.
Termites and ants are natural enemies that fight over territory. Ants living outside a house that has recently been tented for termites will move into the walls and feast on termite corpses, while you, the new homeowner, remain blissfully ignorant because none of the approximately three hundred people involved in the real estate transaction will have bothered to mention this simple fact to you.
The gas used to kill termites has no effect on the ants that will later eat them.
Eventually, the ants that move into your walls will either run out of termite meat or grow bored of their all-termite diet. At that point, they will begin to leave the walls to look for food sources inside the house.