9222108 Jeanne The most remarkable of the social wasps are the tropical species in which new colonies are established by large groups called swarms. The 24 "swarm-founding" genera evolved from a more primitive type, still represented in the tropical fauna, in which colonies are founded by one or a few inseminated queens acting independently, without the help of workers. Not only do the swarm-founding species form the largest, most conspicuous, and most pugnacious colonies, but they dominate the "independent-founders" ecologically, exceeding them in sheer numbers in some localities by several thousand to one. An important reason for the striking success of the swarm-founders is that their entire life cycle is spent as a group. This gives them an advantage in countering the high risk of predation that faces life in the tropics. Swarming cannot work unless the scout wasps, who choose a site suitable for a new nest, can communicate its location to the rest of the swarm. How this is done is known for one species only: the scouts lay a trail of chemical scent-marks, which their swarm-mates follow to the new site. The scent is produced by a particular gland on the abdomen in this species. A number of other swarm- founding genera have the same gland, but in some of these the form of the gland is different, suggesting other functions. In still other species the gland is entirely lacking, suggesting other means of recruiting swarm members. These facts suggest (1) that chemical trails are not universal among swarm-founders and (2) that swarm-founding itself may have had two or more independent origins. The ultimate objective of Dr. Jeanne's research is to determine the specific swarm-recruitment mechanisms utilized by seven key swarm-founding genera and to use the results to test among several hypotheses on the evolution of these mechanisms. The results will yield a much-improved picture of the varieties of communication evolved among the swarm-founding genera and provide an explicit phylogenetic model for the evolution of swarm-recruitment mechanisms. This will make it possible to conduct rigorous comparative studies on the adaptive significance of these mechanisms. Finally, the research will contribute significantly to understanding the evolution of an extraordinarily successful form of social behavior in insects.
