Fig. 2. Inter-individual conservation and bilateral symmetry of odour-induced signals in the drone antennal lobe. (A) Calcium signals obtained in five different drones (1-5), on three left and two right antennal lobes (AL) to the odours 1-hexanol and 9-ODA. Each activity map (calculated as in Fig. 1) is scaled to its own minimum and maximum. While 1-hexanol triggers in all five antennal lobes, a similar pattern of a few activated glomeruli [in particular a large egg-shaped glomerulus (H) on the ventro-lateral side], 9-ODA induces activity almost exclusively in the large dorso-lateral region corresponding to MG2. The arrangement of activated glomeruli is symmetrical in left and right antennal lobes. (B) Simultaneous bilateral optical imaging of the drone AL. On the left, a view of the brain showing the recording window and the localisation of the ALs. Scale bar, 100 µm. On the right, a recording to 1-hexanol showing symmetrical activity patterns in four glomeruli in each lobe. Note that glomerulus H can be identified in both lobes. OL, optic lobe; MB, mushroom bodies; v, ventral; d, dorsal.