Flies were raised at 25°C and 60% relative humidity on standard cornmeal fly food under 12:12h light:dark cycle. 4–7 days old flies were used for experiments and were transferred to fresh food vials 48h before behavioral tests. Fly population was randomized but was kept age matched in each trial. For food deprivation, flies were kept in empty bottles with a wet cotton plug to prevent desiccation. The following fly lines were ordered from Bloomington stock center: Npf-Gal4 (25681), npfr mutants (10747), 20XUAS-TTS-shi[ts1]-p10 (66600; referred to as UAS-shibirets1 in the text), UAS-TrpA1 (26263), MB461B (68327), MB370B (68319), MB504B (68329), MB296B (68308), MB320C (68253), MB077B (68283) and MB112C (68263). UAS-npf-RNAi (108772), UAS-npfr-RNAi (107663) and VT50658 (200166) were ordered from the Vienna Drosophila Resource Center. Other fly lines were described previously: redeye6 (link), R26E0115 (link), R35B1216 , and UAS-CaLexA17 (link). The background control line was Canton-S (Heisenberg) strain.