The first endocrinological regulating mechanism for plasticity in division of labor identified in a eusocial insect, the honey bee (Apis mellifera), is juvenile hormone (JH). The evolution of JH as a regulator of division of labor by age-based task performance (age polyethism) in advanced eusocial insects will be examined in this research. What will be sought are correlative and causal relationships between JH titer and age polyethisms in workers of two species exhibiting independently- evolved advanced eusocial behavior: the stingless bee Melipona favosa and the swarm-founding wasp Polybia occidentalis. Field studies in Panama are to encompass three topics: (a) association of JH titer with behavioral differences, by examination of correlations between endogenous JH titer (assessed by radio-immunoassay) and rate of age polyethisms in workers from unmanipulated colonies, (b) effects of increased JH on behavior, by application of JH topically to M. favosa workers and then testing for dose-dependency effects on age polyethism, (c) correlation of JH titer with plasticity of behavioral role, to be studied by removal of workers from foraging and nest working tasks, then gauging the JH titers of behaviorally altered individuals compared with non-responsive ones. Results will elucidate patterns of the evolution of division of labor, a central component of insect colony integration of advanced eusocial insects. %%% Insect societies are complex, self-organizing entities that are useful as models for other systems such as nervous systems and organismal development. This study will augment our knowledge of rules governing colony function by enhancing understanding of how the behavior of individual components of the system are regulated physiologically. Comprehending mechanisms by which individual behavior is translated into colony function is a central focus of insect sociobiology. Such information is critical to discovering the elements responsible for evolutionary success and ecological impact of eusocial insect in contemporary terrestrial ecosystems, especially tropical ones such as these Hymenopterans inhabit.
