Animal personality aligns task specialization and task proficiency in a spider society.

Classic theory on division of labor implicitly assumes that task specialists are more proficient at their jobs than generalists and specialists in other tasks; however, recent data suggest that this might not hold for societies that lack discrete worker polymorphisms, which constitute the vast majority of animal societies. The facultatively social spider Anelosimus studiosus lacks castes, but females exhibit either a "docile" or "aggressive" phenotype. Here we observed the propensity of individual females of either phenotype to perform various tasks (i.e., prey capture, web building, parental care, and colony defense) in mixed-phenotype colonies. We then measured the performance outcomes of singleton individuals of either phenotype at each task to determine their proficiencies. Aggressive females participated more in prey capture, web building, and colony defense, whereas docile females engaged more in parental care. In staged trials, aggressive individuals were more effective at capturing prey, constructing webs, and defending the colony, whereas docile females were more effective at rearing large quantities of brood. Thus, individuals' propensity to perform tasks and their task proficiencies appear to be adaptively aligned in this system. Moreover, because the docile/aggressive phenotypes are heritable, these data suggest that within-colony variation is maintained because of advantages gleaned by division of labor.

Allometric scaling of metabolism, growth, and activity in whole colonies of the seed-harvester ant Pogonomyrmex californicus.

The negative allometric scaling of metabolic rate with body size is among the most striking patterns in biology. We investigated whether this pattern extends to physically independent eusocial systems by measuring the metabolic rates of whole functioning colonies of the seed-harvester ant Pogonomyrmex californicus. These intraspecific scaling data were compared to the predictions of an additive model developed to estimate collective metabolic rates. Contrary to the prediction of the additive model, colony metabolic rate allometry resembled the pattern commonly observed interspecifically for individual organisms, scaling with colony mass(0.75). Among the same-aged colonies, net growth rate varied by up to sevenfold, with larger colonies exhibiting higher net growth efficiency than smaller colonies. Isolated worker groups exhibited isometric metabolic rate scaling, suggesting that the social environment of the colony is critical to regulating individual patterns of work output. Within the social environment, individual worker locomotor velocities exhibited power-law distributions that scaled with colony size so that larger colonies exhibited a greater disparity between active and inactive ants than did smaller colonies. These results demonstrate that behavioral organization within colonies may have a major influence on colony-level metabolism and in generating intraspecific variation in growth trajectories.

Social insects inspire human design.

The international conference 'Social Biomimicry: Insect Societies and Human Design', hosted by Arizona State University, USA, 18-20 February 2010, explored how the collective behaviour and nest architecture of social insects can inspire innovative and effective solutions to human design challenges. It brought together biologists, designers, engineers, computer scientists, architects and businesspeople, with the dual aims of enriching biology and advancing biomimetic design.

Marking individual ants for behavioral sampling in a laboratory colony.

Ant societies are tractable and malleable, two features that make them ideal models for probing the organization of complex biological systems. The ability to identify specific individuals while they function as part of a colony permits an integrative analysis of social complexity, including self-organizational processes (i.e., how individual-level properties and social interactions give rise to emergent, colony-level attributes such as division of labor and collective decision making). Effects of genotype, nutrition, and physiology on individual behavior and the organization of work also can be investigated in this manner, through correlative and manipulative approaches. Moreover, aspects of colony demography (e.g., colony size, and age and size distributions of workers) can be altered experimentally to examine colony development and regulatory mechanisms underlying colony homeostasis and resiliency. This protocol describes how to sample the behavior of ants living in a colony under laboratory conditions. Specifically, it outlines how to identify and observe individuals within a colony, an approach that can be used to quantify individual- and colony-level patterns of behavior. When a lower-resolution measure of overall group behavior is desired, individual identities might not be required. Given the diversity of ants and their study, this protocol provides a very general methodology; the details can be modified according to the body size, colony size, and ecology of the focal species, as well as to specific research aims. These basic techniques can also be extended to more advanced experimental designs such as manipulation of colony demography and hormone treatment.

Ants (Formicidae): models for social complexity.

The family Formicidae (ants) is composed of more than 12,000 described species that vary greatly in size, morphology, behavior, life history, ecology, and social organization. Ants occur in most terrestrial habitats and are the dominant animals in many of them. They have been used as models to address fundamental questions in ecology, evolution, behavior, and development. The literature on ants is extensive, and the natural history of many species is known in detail. Phylogenetic relationships for the family, as well as within many subfamilies, are known, enabling comparative studies. Their ease of sampling and ecological variation makes them attractive for studying populations and questions relating to communities. Their sociality and variation in social organization have contributed greatly to an understanding of complex systems, division of labor, and chemical communication. Ants occur in colonies composed of tens to millions of individuals that vary greatly in morphology, physiology, and behavior; this variation has been used to address proximate and ultimate mechanisms generating phenotypic plasticity. Relatedness asymmetries within colonies have been fundamental to the formulation and empirical testing of kin and group selection theories. Genomic resources have been developed for some species, and a whole-genome sequence for several species is likely to follow in the near future; comparative genomics in ants should provide new insights into the evolution of complexity and sociogenomics. Future studies using ants should help establish a more comprehensive understanding of social life, from molecules to colonies.