Figure 1

Experimental set-up. A) Closed taxis box, and B) taxis box in an open position. Mosquitoes were placed in the middle chamber and remained there until a pulley mechanism was used to lift the barriers, allowing access to the two side chambers. C) Due to the design of the entry points, mosquitoes could easily fly into a side chamber, but could not return to the centre. Taxis boxes containing mosquitoes exhibiting D1) positive taxis (majority move towards (T) the stimulus), D2) kinesis (mosquitoes distributed randomly between the three chambers), and D3) negative taxis (majority move away (A) from the stimulus) in response to a directional olfactory stimulus indicated by the arrow. E) Taxis boxes within the semi-field tunnel, and F) four taxis boxes set up in parallel at each distance for the full open field experiment in Ifakara, Tanzania. The human experimenter opens and closes the barriers separating the three chambers by a pulley mechanism to allow mosquitoes to orient towards or away from the point of stimulation.