Postembryonic development of the complex tibial organ in the foreleg of the bushcricket Ephippiger ephippiger (Orthoptera,Tettigoniidae)

Summary The postembryonic development of the morphology and anatomy of the complex tibial organ in the foreleg of the bushcricket Ephippiger ephippiger is described. All the receptor cells are present in the subgenual organ, the intermediate organ and the crista acustica in the 1st larval instar. Generally, even in the 1st instar, the arrangement of the scolopidia in the three organs resembles the adult structure. The acoustic trachea, the tympana, the tympanal covers and the acoustic spiracle develop step by step in subsequent instars. The acoustic trachea resembles the adult structure for the first time in the 4th instar, although its volume is still small. The auditory threshold curves recorded from the tympanal nerve in instars 4, 5 and 6 show the same frequency maxima as those in the adult. The overall sensitivity significantly increases after the final moult. The dimensions of structures that lie within the crista acustica and that are probably involved in stimulus transduction and in frequency tuning have been analysed. The dorsal wall of the anterior trachea, the tectorial membrane and the cap cells have similar dimensions, especially in the last three instars and in adults.