AbstractSystems of oscillators, whether animate or inanimate, often converge to a state of collective synchrony, when sufficiently interconnected. Twenty years ago, the mathematical study of models of coupled oscillators revealed the possibility for complex phases which exhibit the coexistence of synchronous and asynchronous clusters, since then referred to as “chimera states”. Beyond their recurrence in theoretical models, chimera states have been observed in specifically-designed, non-biological experimental conditions, yet their emergence in nature has remained elusive. Here, we report robust evidence for the occurrence of chimera states in a celebrated realization of natural synchrony: fireflies. In video recordings of collective displays of Photuris frontalis fireflies, we observe, within a single swarm, the spontaneous emergence of different groups flashing with the same periodicity but with a constant time delay between them. From the three-dimensional reconstruction of the swarm, we demonstrate that these states are stable over time and spatially intertwined, but find no evidence of enhanced correlations in their spatial dynamics. We discuss the implications of these findings on the synergy between mathematical models and firefly collective behavior.
