Fig. 4.

Steck-Knaden assay. A 16 individually tracked flies are exposed to a clean-air flow. a–c A computer-controlled stimulus device generates odor stimuli, that meet the flies at a predictable time. When encountering an attractive odor, flies walk upwind. The tracking system calculates upwind speed before and after the stimulus reaches the fly. B Wind tunnel. d Flies show crosswind flights when exposed to clean-air flow. e When getting in contact with an odor plume, flies start upwind flights. A 3-D tracking system detects the time of plume contact and plume loss and calculates the flight’s directionality and upwind speed before and afterwards