Figure 4.

Long-distance olfactory search without a cognitive map. In flying flies, olfactory search behavior emerges from a sequence of chained reflexes. Odor encounter triggers an upwind surge, in which the animal flies parallel to the wind direction. Loss of the plume evokes a crosswind cast, in which the fly flies perpendicular to the direction of flow, which allows the fly to reenter the plume and trigger another upwind surge. As the fly gets close to the target, it becomes attracted to visual objects and executes a sequence of behaviors, including deceleration, leg extension, and landing.