Extended Data Figure 6. Schematic of collective odour avoidance in Drosophila.

a, A group of flies experiences odour flow on the right half of the arena. The direction of odour or air flow is indicated by red and black arrows, respectively. Odour increases the probability of spontaneous walking (black fly). b, Walking increases the probability of encountering a stationary fly, producing an Encounter Response. c, Walking flies cause additional Encounters and a cascade of Encounter Responses in the odour zone. d, Walking flies pass into the non-odour zone through interactions with the arena walls and possibly by sensing the direction of odour flow. e, The influx of walking flies to the air zone results in additional Encounter Responses. f, The propensity to turn around at the air-odour interface (perhaps compounded by the effects of unknown aggregation pheromones) causes flies to remain in the air zone, resulting in higher odour avoidance.