Exploration/aggregation in odours gradients. We used a chamber and three systems as detailed in the drawing (top). Grape juice (50 μl, 100 μl and 300 μl) was placed inside the three systems. The protocols are described in the Methods section. Briefly, tubes are painted black to eliminate any visual interference with exploration. One set of experiments is carried out in an aerated chamber (odour gradients are maintained), the other in grape juice-saturated atmosphere (see figure 4 and Methods section). One hundred flies were placed in the chamber and the flies inside the 3 tubes were counted 10 hours later. (A) tube with 50 μl, (B) 100 μl and (C) 300 μl. The mutants GC253bv, GC207ca and GC782ca were analyzed along with genetic background ca and bv. Values are mean ± SEM (n = 10).