Division of labor, the specialization of workers on different tasks, largely contributes to the ecological success of social insects [1, 2]. Morphological, genotypic, and age variations among workers, as well as their social interactions, all shape division of labor [1-12]. In addition, individual experience has been suggested to influence workers in their decision to execute a task [13-18], but its potential impact on the organization of insect societies has yet to be demonstrated [19, 20]. Here we show that, all else being equal, ant workers engaged in distinct functions in accordance with their previous experience. When individuals were experimentally led to discover prey at each of their foraging attempts, they showed a high propensity for food exploration. Conversely, foraging activity progressively decreased for individuals who always failed in the same situation. One month later, workers that previously found prey kept on exploring for food, whereas those who always failed specialized in brood care. It thus appears that individual experience can strongly channel the behavioral ontogeny of ants to generate a lasting division of labor. This self-organized task-attribution system, based on an individual learning process, is particularly robust and might play an important role in colony efficiency.

In most circumstances, social insects recognize their nestmates. They can discriminate against alien adults and also against alien larvae. Results presented here indicate that the mechanism of colony-brood recognition is acquired in large part during larval life and persists through the metamorphosis into the adult stage. During the first days after emergence of the adult, a weaker form of learning can also occur. These phenomena are discussed in relation to kinship theory. It appears that kin recognition is determined not so much by genetic relatedness as by spatial proximity of the individuals during the early stages of life.Most social insects can discriminate nestmates from nonnestmates (1). The hostility shown to adults of alien colonies is evidence of colony recognition. Recent data have revealed that intraspecific brood discrimination also exists in some ant species (2-5) and wasps; such discrimination manifests itself in differential brood-nursing activities (5-7). For the honey bee, comparable discrimination is not clearly established, as contradictory results have recently been published (8, 9).In Cataglyphis cursor Fonscolombe, brood-nursing ants prefer larvae from their own colony to those from an alien colony, which they give only half as much care as their own brood (unpublished data). We report here results that indicate an important role for learning such discrimination very early in life, during the larval stage. METHODS AND RESULTSExperiment 1: Effect of isolation during the first 10 days of adult life Young C. cursor workers were taken from their colony less than 8 hr after eclosion and were placed for 10 days in one of three situations.In one group (Gi; 98 ants) each ant was completely isolated until age 10 days. The workers were then formed into subgroups of seven workers each, and 15 min later they were tested by being offered a choice among three nestmate larvae (NL) and three alien larvae (AL). The larvae in this and other experiments were identified by sticking colored plastic spots on them. Each instance of licking or carrying of a larva for the next 15 min was recorded.In another group (G2), each of 82 young workers was familiarized with members of an alien colony, here called the "familiar colony," by being kept with two adults and two larvae (FL) from that colony for 10 days. These ants too were then formed into groups, of about seven each, and 15 min later were tested, in this case for their choice among three NL and three FL.The 98 newly hatched ants of the third group (G3) were kept for 10 days in groups of seven nestmates each and then were tested for choice among three NL and three AL.In G1 and G3, NL were clearly preferred to AL (Fig. 1) (P < 0.01) (except where noted otherwise, Wilcoxon tests were used). Early isolation as adults (Gi) did not reverse the ants' preference for their NL, although this preference was weaker than in the group kept with nestmates (G3) (P < 0.05, Mann-Whitney U test).The ants of G2 (familiarized with individuals from an alien colony) still sl...