Flight trajectory of a nocturnal fly, filmed under IR conditions using two PTZ cameras. The fly flew from a starting platform (shown on the left) toward a “virtual cricket” represented by a loud-speaker on the floor. The observed volume was approx. 10m3. When the fly passed a previously defined plane, a different virtual cricket began to sing (left loud-speaker), and the fly subsequently altered its flight course toward the new sound source. Image courtesy of Pie Müller. Results are published in Müller and Robert (2002). Also see Fry et al (2004), Müller and Robert (2001) for related publications.