All the work is done by smell in an anthill. The first thing an ant does when it finds food like larvae is to sprinkle a smell on it. Thereafter as it rushes back to inform other ants about the discovery, it goes on sprinkling smell at various places on the way so that all the ants coming for the food can take the same route. An amazing arrangement of Nature is that the ants of each colony have distinctive smell. That is why when two ants meet they never fail to ascertain whether they belong to the same anthill by means of sniffing each other. If the smell differs, the interloper is immediately attacked and chased away. The importance of distinct smell for an ant can not be exaggerated because devoid of that peculiar odor the ant will run the risk of attack by other ants of its own colony!
In short, each ant must carry its ID in the form of the colony’s smell all the time.