Mosquitoes mostly mate in the context of swarms: to facilitate encounters with females, males form disordered aggregations over a visual marker, which serves as a positional reference. Due to the scarcity of high-resolution data, it remains unclear whether swarms are the result of individuals interacting independently with the marker, or whether they are the expression of a genuine collective behavior produced by spontaneous interaction between individuals. Here, with a unique dataset comprising three--dimensional trajectories of 27 laboratory swarms of different size (ranging from 80 to 400 mosquitoes), we investigate swarming behavior of Anopheles gambiae mosquitoes. With a statistical physics approach, we provide experimental evidence of an effective male-male interaction. We find that individual speed fluctuations are strongly correlated in space, meaning that mosquitoes in close proximity tend to display similar deviations from the group average, effectively flying at a similar speed. We also prove that this correlation is not compatible with a random arrangement of individuals, indicating that an interaction process is at play. Our findings suggest that collective behavior in lab-based mosquito swarms indeed emerges from an interaction mechanism that, unexpectedly, does not involve the direction of flight, as observed in other biological systems, but rather their speed.
Iacomelli et al. (Fri,) studied this question.