The taste system controls many insect behaviors but is greatly understudied in mosquitoes. Little is known about how tastants are encoded in mosquitoes or how they regulate critical behaviors. Here we examine how taste stimuli are encoded in mosquitoes and how these cues regulate biting, feeding, and egg laying. We identify three functional classes of taste sensilla with an expansive coding capacity. Complex cues, including human sweat, nectar, and egg-laying site water, elicit distinct response profiles from the neuronal repertoire. Certain bitter compounds suppress physiological and behavioral responses to sugar, suggesting their use as potent stop signals against appetitive cues. We identify key tastants on human skin and in sweat that synergistically promote biting behaviors. Lastly, we also identify a new class of compounds that effectively deter biting behaviors. Our study sheds light on key features of the taste system that suggest new ways of manipulating chemosensory function and innovating methods of vector control.