Panacanthus pallicornis (Walker, 1869)

The calling song of this species is remark- able for a very low audio principal carrier frequency (Fig. 12). Ten specimens were recorded in the field at 18 '' C and their mean dominant peak, per single-note spectra, was 5.0kHz (standard error 1/4 0.6 kHz, range 4.6-6.1 kHz). High energy audio this low is unusual in tettigoniids (Heller, 1995) but is known for a few Neotropical species (i.e. Choeroparnops; Morris et al., 1994). It puts the most intense peak of the insect's carrier near our best human sensitivity and so makes the species seem very loud to human listeners. At 24''C, the call of ten males measured in the laboratory (10 cm dorsal, impulse) had a mean sound level of 97.6 dB (range 94-101 dB).
Eleven males were recorded successfully and analysed with full frequency range (ultrasonic effective) equipment under laboratory conditions; the average values below are based on this sample. Their dominant frequency was 4.6 kHz. No significant energy was found beyond 25 kHz (Fig.12B). Although the low and consistently prominent audio principal peak is rather narrow, the spectrum may still be best regarded as low-Q. There is a second broad band of energy from 15 to 25 kHz, peaking near 21 kHz (n1/411). Each song lasted 54ms, incorporating about 203 complex waves (Fig. 11C, D).

The shortest time-amplitude song element of this species resolvable by the human ear is a tick (short, noisy without perceptible infrastructure). Tegminal movement is readily observed and sound emission is seen to coincide with tegminal closure. Ticks are given in bouts of one to five with a bout period of 0.24 s. Between bouts there occur silences rather vari- able in duration of 2 s to tens of seconds. A succession of bouts incorporates increasingly more ticks to a maximum of five.

Tremulation calling was sometimes observed in this species, alternating with the airborne signal, but not all individ- uals did this. The simplest element of tremulation display was a succession of vertical body oscillations; a 'quiver'. Quivers were repeated at an irregular rate of five or so in a bout. The time between these tremulation bouts was 5 s to several tens of seconds. [1]

References