Honey bees undergo an age-related, socially regulated transition from working in the hive to foraging that has been previously associated with changes in the expression of thousands of genes in the brain. To understand the meaning of these changes, we conducted microarray analyses to examine the following: (i) the ontogeny of gene expression preceding the onset of foraging, (ii) the effects of physiological and genetic factors that influence this behavioral transition, and (iii) the effects of foraging experience. Although >85% of Ϸ5,500 genes showed brain differences, principal component analysis revealed discrete influences of age, behavior, genotype, environment, and experience. Young bees not yet competent to forage showed extensive, age-related expression changes, essentially complete by 8 days of age, coinciding with previously described structural brain changes. Subsequent changes were not age-related but were largely related to effects of juvenile hormone (JH), suggesting that the increase in JH that influences the hive bee-forager transition may cause many of these changes. Other treatments that also influence the onset age of foraging induced many changes but with little overlap, suggesting that multiple pathways affect behavioral maturation. Subspecies differences in onset age of foraging were correlated with differences in JH and JH-target gene expression, suggesting that this endocrine system mediates the genetic differences. We also used this multifactorial approach to identify candidate genes for behavioral maturation. This successful dissection of gene expression indicates that, for social behavior, gene expression in the brain can provide a robust indicator of the interaction between hereditary and environmental information. T he honey bee, Apis mellifera, is one of the model organisms being used to achieve a comprehensive understanding of social life in molecular terms: how social life evolved, how it is governed, and how it influences all aspects of genome structure, genome activity, and organismal function (1). Honey bees offer complex but experimentally accessible social behavior, a compact and well studied brain, and a sequenced genome that provides the foundation for ever-increasing genomic resources.Honey bees, like many species of social insects, display a division of labor among colony members that is based on behavioral specializations associated with age (2). Adult worker honey bees perform a series of tasks in the hive when they are young (such as brood care or ''nursing'') and, at Ϸ2-3 weeks of age, shift to foraging for nectar and pollen outside the hive. The transition to foraging involves changes in endocrine activity, metabolism, circadian clock activity, brain chemistry, brain structure, and brain gene expression (3).The pace of behavioral maturation in honey bees is not rigid, because the onset age of foraging depends on the needs of the colony. Pheromones and other social cues mediate this behavioral ontogeny and affect foraging onset (4). These cues are thought to act direct...

Previous research showed that the presence of older workers causes a delayed onset of foraging in younger individuals in honey bee colonies, but a specific worker inhibitory factor had not yet been identified. Here, we report on the identification of a substance produced by adult forager honey bees, ethyl oleate, that acts as a chemical inhibitory factor to delay age at onset of foraging. Ethyl oleate is synthesized de novo and is present in highest concentrations in the bee's crop. These results suggest that worker behavioral maturation is modulated via trophallaxis, a form of food exchange that also serves as a prominent communication channel in insect societies. Our findings provide critical validation for a model of self-organization explaining how bees are able to respond to fragmentary information with actions that are appropriate to the state of the whole colony.

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Our aim was to show how interindividual interactions, based on specific recognition signals that induce aggregation, can lead to the emergence of a segregation pattern between species. Groups including two cockroach species, Periplaneta americana (L.) (P.a.) and Periplaneta fuliginosa (Serville) (Dictyoptera: Blattidae) (P.f.) were tested. Behavioural choice tests between two resting sites demonstrated aggregation behaviour in the two species. Aggregation in both species is based on chemical cues. Periplaneta fuliginosa has a higher aggregation level than P.a. and responds only to its conspecific odour. Periplaneta americana is attracted by the odour of both species presented alone. In the presence of the odours of both species, P.f. selects its own odour, but P.a. neither selects its own odour, nor aggregates under these conditions. This could mean that the perceived chemical signals impair the aggregation process. In mixed groups including larvae of these two species, segregation between species occurs. We assumed that the first species that happened to form an aggregate on one of the resting sites induced the other species to occupy the remaining site. The emergence of a segregation pattern between the two species could be a consequence of the aggregation processes.