Gustatory receptor which mediates acceptance or avoidance behavior, depending on its substrates. Required for sensing all nonvolatile repulsive chemicals, including tastants, pheromones, and especially N,N-Diethyl-meta-toluamide (DEET), the most widely used insect repellent worldwide. Functions also as a pheromone receptor for a male inhibitory pheromone leading to male-male courtship suppression. Expressed widely in gustatory receptor neurons (GRNs) that respond to aversive chemicals. In larvae, is expressed in neurons of the terminal external chemosensory organ, and the dorsal, ventral and posterior external chemosensory organs. Impairs avoiding all nonvolatile repellents tested, ranging from quinine to denatonium, lobeline, caffeine, and N,N-Diethyl-meta-toluamide (DEET). Also displays increased male-to-male courtship. Belongs to the insect chemoreceptor superfamily. Gustatory receptor (GR) family. Gr66a subfamily.