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Hysteresis stabilizes dynamic control of self-assembled army ant constructions.
Helen F McCreery1, Georgina Gemayel2, Ana Isabel Pais3,4
1School of Engineering and Applied Sciences, Harvard University, Boston, MA, 02134, USA. hmccreery@gmail.com.
Nature Communications
|March 5, 2022
Summary
Army ants build bridges that adapt to changing gaps, showing hysteresis. This dynamic control emerges from individual ants
Area of Science:
- Collective behavior and self-assembly in biological systems.
- Animal behavior, specifically social insects and swarm intelligence.
- Complex systems, control theory, and emergent properties.
Background:
- Biological systems require robust control mechanisms to adapt to dynamic environments.
- Decentralized systems face challenges in implementing effective control amidst noise and uncertainty.
- Army ant bridges, formed by living ants, provide a model for self-assembled structures responding to environmental changes.
Purpose of the Study:
- To characterize the dynamic response of army ant bridges to changing gap sizes.
- To identify the underlying control mechanism governing bridge formation and adaptation.
- To understand how individual ant decisions lead to emergent collective behavior and robust structures.
Main Methods:
- Field experiments were conducted to observe army ant bridge construction in response to varying gap sizes.
- Computer simulations were used to model individual ant behavior and collective bridge formation.
- An accumulator model was employed to explain the observed hysteresis in bridge size.
Main Results:
- Army ant bridges exhibited hysteresis: they were larger when the gap increased compared to when it decreased.
- The accumulator model successfully explained this hysteresis, linking individual decisions to current and equilibrium bridge states.
- Field data indicated distinct cues for joining (high bridge performance) and leaving (ant excess), promoting stabilizing hysteresis.
Conclusions:
- Army ant bridges demonstrate a robust collective control mechanism that adapts to persistent environmental changes while filtering transient fluctuations.
- Stabilizing hysteresis, driven by individual ant responses to performance and density cues, is crucial for resilient self-assembled structures.
- The findings offer insights into dynamic control in decentralized systems, applicable to both biological and engineered applications.
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