How to become one: the proximate mechanisms of self-assembly behaviour in social insects (Hymenoptera: Formicidae, Apidae)

Carlesso, D.; Reid, C.R.

Abstract: Collective behaviour is an integral part of social insects’ lives. From nest building to complex foraging networks, insects have evolved extraordinary abilities to organize and coordinate their actions to solve challenges outside the reach of the capabilities of an individual. One of the most striking examples of collective behaviour observed in social insects is that of self-assemblages: sophisticated three-dimensional structures that insects form by linking their bodies together. Selfassemblages are extremely dynamic, can rapidly adapt to colony needs and local conditions, and rapidly disassemble when no longer needed. As other forms of collective behaviour, these structures are completely self-organized. They emerge from relatively simple and locally mediated interactions among colony members, which are only locally informed and without any blueprint. Research on the proximate mechanisms underlying the emergence of self-assemblages has long been hindered by their inherent complexity. In the last twenty years, however, increased access to advanced technological tools has allowed scientists to describe the individual-level rules used by insects when self-assembling. Here, we review the current knowledge on the behavioural rules governing self-assembly behaviour in social insects, highlighting the striking similarities observed within and among genera. We discuss the impact that two factors – inter-individual heterogeneity and environmental geometry – may have on self-assemblages and suggest these as promising areas for future research in the field. Lastly, we propose a simplified algorithm for self-assembly behaviour in the two ant genera for which we have the most individual-level data – Eciton army ants and Solenopsis fire ants – showing that a few behavioural rules can be generalised to multiple structures. Further research on the proximate mechanisms underlying self-assemblages is necessary to understand the evolutionary history of this behaviour in insect societies and to provide insights to engineers and roboticists for developing adaptive algorithms for artificial swarm systems.

Myrmecol. News 33: 149-168