Psyche 
[March 
198 
the beetle’s sound, without detailed consideration of the physical basis 
of sound production. 
Only two live females and one male of A. pustulosum were avail- 
able for sound studies. The animals were affixed to wire tethers 
glued to their pronotum with wax, and induced to stridulate by 
pinching their legs individually with forceps. Sound recordings were 
made with the beetles held at 1 cm from the microphone. An oscillo- 
gram of a typical chirp sequence is shown in Fig. 14A. The bi- 
syllabic composition of each chirp, indicative of the bi-directional 
movement of the ridges across the elytral margins, is clearly evident. 
Measurements made from oscillograms, of chirp repetition rates, chirp 
and syllable durations, and duration of inter-chirp and inter-syllable 
intervals, are summarized in Table 1, together with measurements 
of tooth counts and tooth spacings made from the serrate ridges. 
These parameters are evidently remarkably constant for any one 
beetle, although they differ somewhat between beetles. The Table 
does not give an indication of the gradual decline in the chirp repe- 
tition rate that characteristically took place with time following onset 
of pinching of a given leg (e.g. in a female, the rate declined from 
2.25 to 1.63 chirps/sec over a period of 4.5 seconds). The decline 
occurred by a lengthening of the inter-chirp interval, rather than by 
prolongation of the syllables or inter-syllabic interval of the chirp 
itself. Accelerated chirping (or gland eversion) always occurred 
when pinching was shifted to a new leg or increased in intensity. 
As was to be expected by analogy with the stridulatory chirps of 
Atta, and shown clearly by the oscillograms (Fig. 14B, C), the 
syllables are essentially trains of sound pulses, generated by impact 
of the elytral margins with the sequence of teeth on the ridges. 
Figs. 14D and 14E show oscillograms of individual pulses from a 
first and second syllable respectively. 
Spectrograph analysis (Fig. 15) of the chirps revealed a frequency 
composition ranging broadly from below 1 kHz to 60 kHz. The 
frenquency distribution pattern was essentially similar in the first and 
second syllables, and differed little in spectrographs made with broad- 
band (Fig. 15 top) and narrow-band (Fig. 15 bottom) filters. Since 
broad-band filtration essentially analyzed the pulses one at a time, 
rather than in groups of three to five as in narrow-band filtration, it 
follows that the pulses themselves contain essentially the full range 
of the beetle’s sound frequencies. 
Apparatus for measuring sound intensities became available only 
after the beetles had died. Intensities therefore had to be measured 
