Size isn't the prob, the ants do not leave a heat signature so any IR camera will not see them, especially the Bcam ,don't like it-sorry:( Carpenter ants will not give off heat, sometimes on a good day with the right camera you can pick up the air trapped in the galleries, but no ants. If it was cold you might have picked up a critter seeking refuge for the weather and when you went back they had left - maybe. Image Insert: 6.26 KB Termite gallery in stud. Image Insert: 10.78 KB Rodent in wall.