Tympanic ears in modern insects occur on a bewildering variety of body parts and are thought to have evolved from ubiquitous stretch or vibration receptors. A novel set of hearing organs was found in a relatively ancient, atympanate bladder grasshopper (Bullacris membracioides) capable of signaling acoustically over about two kilometers. Within single individuals of this species, six pairs of serially repeated abdominal ears exhibit functional continuity from simple to more complex forms, providing evidence for the transition in function and selective advantage during the evolutionary development of a complex feature. These chordotonal hearing organs comprise up to 2000 sensilla, in contrast to the relatively modest numbers found in modern grasshoppers (ca. 70). Together with multiple attachment sites at the cuticle, this large number of cells suggests the possibility of functional organization. Here we take a detailed look at the anatomical structure of the hearing organs.