Behavioral response of house flies (Diptera: Muscidae) to 3 bittering agents

House flies, Musca domestica L., are pests at livestock facilities. House fly numbers are controlled mainly by manure management and chemical controls, like use of toxic baits. Some toxic baits contain denatonium benzoate as a bittering agent, to avoid poisoning of children. House fly behavioral response to denatonium benzoate was examined, using 2 different diluents, sucrose solution or orange juice. Response of flies to quinine and sucrose octaacetate, 2 other bittering agents, was also examined in sucrose. Sucrose is the sweetener in commercially available toxic house fly baits. The proboscis extension response of both male and female flies was significantly reduced by addition of 1,000 ppm of denatonium benzoate to sucrose. Response in males was also reduced at 100 ppm. Consumption of sucrose by both male and female flies was reduced by addition of 100, 500, and 1,000 ppm of denatonium benzoate, but consumption by males was also reduced at 10 ppm. Addition of sucrose octaacetate had no detectable effect on consumption of sucrose at 100, 500, or 1,000 ppm. In contrast, addition of quinine reduced consumption by both male and female flies in all tested concentrations. In orange juice, 10 ppm of denatonium benzoate is often avoided by children. With orange juice, fly proboscis extension response patterns were the same for both sexes, with a reduction at 1,000 ppm of denatonium benzoate. Orange juice consumption by flies was reduced significantly at 1,000 ppm of denatonium benzoate for females but not at any of the concentrations tested for males.