The study of alimentary behaviour in newly founded societies of antsTapinoma erraticum (Dolichoderinae) with marks on the gaster enabled us to classify the individuals in terms of foraging and brood care. There are 3 different groups: permanent foragers (foragers in more than 80% observations), intermittent foragers (between 20 to 80%) and nurses (less than 20%). The behaviour of ants changes with age: young ants are nurses at first, them they are intermittent foragers, and permanent foragers at last. Ants less than one month old are calledyoung (under laboratory conditions): 65% of them are nurses, some are intermitent foragers (35%). Ants more than one month old are calledold: 60% are intermittent foragers, 30% permanent foragers and 10% only nurses. Young workers become nurses very quickly (in a few days) but they are not active donors to other workers. After one month most of them become members of a pool of unemployed ants able to forage and give food to the queen or larvae. Most of the foraging is done by permanent foragers, older workers. Individual development is very variable, according to social pressure, if there are not enough old foragers, young ants become foragers. This phenomenon can be reversible.