A hearing defect in iav mutants. Recordings of antennal sound-evoked potentials from control (iav⁺), iav mutant, and transgenic iav; P[iav⁺] flies in response to repeated pulse trains. Records shown are averaged responses in single antennae to 10 or (where noted) 100 pulse stimuli. Mutants hemizygous for either iav allele show no trace of a response, whereas a single wild-type transgene P[iav⁺ 2.2] restores a normal response to the iav¹ background.