Brains were dissected and stained as previously described \cite{Halter_Fischbach_Stocker_1999} 3-4 days after eclosion with an anti-GFP antibody (1:1000, Molecular Probes) and the monoclonal antibody nc82 (1:50, DHSB), which recognizes neuropil. Frozen antennal sections were stained as described previously \cite{s_Chiappe_Amrein_Vosshall_2004} using an anti-GFP antibody (1:1000, Molecular Probes), and an anti-Orco antibody (1:5000) raised against the peptide (SSIPVEIPRLPIKS) by AbFrontier.