(a–c) The GAL4 expression patterns, detected by UAS-eGFP (green), in the adult brain of three different drivers that primarily express in the pars intercerebralis: (a) c929-GAL4, (b) 50Y-GAL4 and (c) dIlp2-GAL4. Neuropil is marked with an anti-Dlg antibody (red). Arrowheads denote the pars intercerebralis. Scale bar=100 μm. (d) Fighting frequencies of flies expressing UAS-tllRNAi in different regions of the fly brain using c929-GAL4, 50Y-GAL4, dIlp2-GAL4, GMR-GAL4, cry-GAL4 and c819-GAL4 and a control line of UAS-tllRNAi/+. Only c929>tllRNAi, 50Y>tllRNAi and dIlp2>tllRNAi males showed statistically significantly higher median fighting frequencies (Kruskal–Wallis ANOVA, **P<0.01 and ***P<0.001, n=minimum of 70 pairs for each genotype). (e) Fighting frequencies of flies with tailless knocked down in 50Y neurons or of flies co-expressing tsh-GAL80, elav-GAL80 or TubP-GAL80 (GAL80 abbreviated as G80). Asterisks denote statistically significant rescue in elav-GAL80 and TubP-GAL80 co-expressing males (Kruskal–Wallis ANOVA, ***P<0.001, n=minimum of 60 pairs for each genotype). (f) Fighting frequencies of flies with tailless knocked down in 50Y neurons and control lines of flies expressing a component of the GAL4/UAS system. Fighting frequencies of flies co-expressing tllRNAi and either fly tll or human NR2E1 and eGFP in 50Y neurons and control lines expressing only one component of the GAL4/UAS system. Letters denote groups with statistically significant different median fighting frequencies. Black bars show statistically significant rescue in males co-expressing UAS-Tll or UAS-NR2E1 compared with 50Y>tllRNAi and 50Y>tllRNAi males co-expressing UAS-eGFP (Kruskal–Wallis ANOVA, n=minimum of 70 pairs for each genotype). Bar graphs represent means±s.e.m.