Is the well-trodden path always the correct path? New insights into the role of footprint hydrocarbons during ant foraging

Positive feedback and negative feedback are crucial mechanisms in the regulation of biological systems and whilst the role of positive feedback has been well studied in social insect networks, the role of negative feedback has not. This thesis presents evidence of a novel negative feedback mechanism at work during foraging by the ant Lasius niger. In a foraging context, cuticular hydrocarbons, passively deposited on substrate by ants as they walk, can act as a repellent cue. This effect can be measured through branch selection by foraging workers at a trail bifurcation. Evidence from both a highly controlled experimental set up and a more natural foraging context are provided to support this claim. The possible role of this signal in ant foraging networks is considered and comparisons with other known negative feedback mechanisms in ant foraging networks are drawn. Experiments with the ant Monomorium pharaonis were unable to show negative feedback signals being used to optimise food search tactics and this finding is evaluated in relation to the ecology of M. pharaonis. Circumstantial evidence is also presented in support of the hypothesis that L. niger workers can use alarm pheromones to recruit nest mates to unexplored territory. The need for further work testing this hypothesis is highlighted. The communication role of ant interactions during foraging is discussed and, based on new observations with L. niger workers, the position of the signaller relative to the recipient during the interaction is proposed as a possible component of the signalling mechanism. Further possible experiments based on both empirical observations and computational models are proposed to help augment the findings presented in this study.