Octopamine (OA) and its precursor tyramine (TA) are neurotransmitters operating in many different neuronal and physiological processes. We investigated the role of those two transmitters in Drosophila sugar responsiveness. Tyrosine-\(\beta\)-hydroxylase (t\(\beta\)h ) mutants are unable to convert TA into OA. Starved mutants show a reduced sugar response and their hemolymph sugar concentration is elevated compared to control flies. When starved to death, they survive longer. Temporally controlled rescue experiments revealed an action of the OA/TA-system during the sugar response, while spatially controlled rescue experiments suggest actions also outside of the nervous system. Additionally, the analysis of four OA- and four TA-receptor mutants suggests an involvement of both receptor types in the animals' physiological and neuronal response to starvation. These results complement the pharmacological investigations in Apis mellifera described in our companion paper (Buckemheimer et al.).