Acoustical analysis of the auditory system of the cricket Teleogryllus commodus (Walker)

The basic auditory physiology of crickets, and particularly of Teleogryllus commodus (Walker) is examined and its behavior simulated by electrical analog networks, beginning from the simplest possible model and progressing by stages to the full system found in the real insect. It is found that the attenuation of sound in the auditory trachea plays a crucial role in the mechanism for directional hearing in even the simplest model and that the tracheal diameter is in fact appropriate to produce the desired attenuation. In a more complex model in which it is recognized that the auditory system probably responds to pressure changes in the tracheal sacs underlying the tympana rather than simply to tympanic motion, it is found that the phase shift produced by the combined effects of the central septum and the adjoining cavities leading to the spiracles is also important to hearing directionality. The final model which includes both tympana and spiracles is able to simulate both the hearing directionality and, in part, the frequency selectivity of the system. It appears, however, that a large measure of the observed frequency selectivity is due to some form of selectivity in the neural transducers themselves rather than in the simple acoustic components of the system.