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...

We measured the age at onset of foraging in colonies derived from three races of European honey bees, Apis mellifera mellifera, Apis mellifera caucasica and Apis mellifera ligustica, using a cross‐fostering design that involved six unrelated colonies of each race. There was a significant effect of the race of the introduced bees on the age at onset of foraging: cohorts of A. m. ligustica bees showed the earliest onset, regardless of the race of the colony they were introduced to. There also was a significant effect of the race of the host colony: cohorts of bees introduced into mellifera colonies showed the earliest onset of foraging, regardless of the race of the bees introduced. Significant inter‐trial differences also were detected, primarily because of a later onset of foraging in trials conducted during the autumn (September–October). These results demonstrate differences among European races of honey bees in one important component of colony division of labor. They also provide a starting point for analyses of the evolution of division of labor under different ecological conditions.

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This study was carried out in the laboratory on experimental groups of adult Mudskippers of both sexes; also natural populations were observed in mangrove swamps along the west coast of Madagascar. This paper deals mainly with the various aggressive postures and their role in the establishment and defense territories, the variations of aggression in an experimental group and, in the field, according to the tide movements. The hierarchial organization in the group of Mudskippers, the emergence of displacement activities and vacuum activities, the structure and dimensions of territories have also been studied.

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