1. L3 is an auditory interneuron in the prothoracic ganglion of the cricket, Acheta domesticus. The degree of syllable period (SP) specific decrement to model calling songs is age-specific in L3. In response to calling songs having 50 ms SPs, L3s in old females (23-28 days) exhibit less response decrement than those in young (4 days) females (Figs. 1, 2). 2. Two to 4 days after juvenile hormone III (JHIII) application to old females, L3s respond in a decrementing manner similar to those of young females. The changes in the SP selectivity of L3 by age and JHIII application, correlate well with changes that have been demonstrated to occur in the selectivity of phonotaxis under similar conditions (Fig. 3). 3. The threshold of L3 does not change with age, while changes in L3's decrement result from decreased excitation in old females in response to the first syllable of a chirp (Figs. 4, 5). 4. Injection of patterned current pulses (which reproduce the temporal pattern of the calling song) do not elicit decrement (Fig. 6). 5. Age-related changes in selectivity to SP of the calling song occurs above and below L3s threshold (Fig. 7). © 1992 Springer-Verlag.