Behaviour of group-living outbreaking insects

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Insect outbreaks, from seething swarms of locusts to writhing masses of caterpillars, can be spectacular, not only by their sheer numbers, but also by the way multitudes of individuals move and feed in concert. This pattern of collective behaviour is an emergent group property that arises from the responses of individuals to each other and to the environment. Emergence means that interactions between individuals generate feedback loops leading to group behaviour that cannot be predicted from the behaviour of individuals. Therefore, studying the behaviour of groups, and how it emerges from that of individuals, is necessary to understand the ecology of group-living species. The forest tent caterpillar is a group-living outbreaking forest pest across most of Canada. These caterpillars live in colonies that travel together between resting and feeding sites, laying pheromone trails behind them. The purpose of my research is to show how individual behaviour generates the dynamics observed at the colony level, and to determine the role played by these dynamics in the species' ecology. Specifically, the questions I intend to answer are: 1. How do colonies stay together and keep synchronized? 2. How does food quality influence the timing and duration of caterpillar meals? And, 3. How do patterns of colony collective foraging emerge from the answers to the previous two questions? My research uses a bottom-up approach, starting by characterizing behaviour and determining the proximate mechanisms involved. Observations of individual caterpillars will be used to build computer models, whose predictions will be compared with the behaviour of colonies in the field. This research programme will bring important insights to fundamental science in behavioural ecology by explaining how groups collectively make choices about when and where to feed. It will also contribute to applied entomology by shedding insight into the role of group dynamics in both the individual and population ecology of outbreaking insects.