The expression of Gr58c^Scer\UAS.cDa under the control of Scer\GAL4^Gr89a.2 leads to the following electrophysiological response changes of labellar sensilla to bitter tastants, as compared to controls: I-a sensilla display novel responses to Myricetin, Strychnine nitrate salt and Coumarin, and significantly increased responses to Quinine, (-)-lobeline HCl and Denatonium benzoate; I-b sensilla display a novel response to Denatonium benzoate, a significantly increased response to (-)-lobeline HCl, and significantly decreased responses to Caffeine, Theophylline and Umbelliferone; S-a sensilla display significantly decreased responses to Umbelliferone and Aristolochic acid; these labellar sensilla types display no significant electrophysiological response changes to Rotenone, N,N-Diethyl-m-toluamide, Escin, Gossypol, Theobromine, Cucurbitacin I hydrate, D-(+)-sucrose octaacetate, Azadirachtin, Saponin, Sparteine sulfate salt and Berberine chloride.