Acanthoplus longipes

The calling song of A. longipes males (Fig ure 2A) was produced in the late evening. The males were persistent singers, often singing for severa l minutes without any interruptions. Most stayed in one place, usually elevated , while singing, but some walked around without stopping to sing. The sound pressure level reached about 87 dB SPL in a distance of 10 cm caudal ( n = 4). The calling song cons isted of a sequence of verses that were separated into two pulses by a pause of about 16 ms (Fig ure s 2A, 2 C). These two pulses consisted of 2 to 7 impulses, which differed between the tested males (Fig ure 3), but all males had fewer impulse s in the first p ulse than in the second pulse. In one of the six males (M2 in Fig ure 3) the second pulse more than doubled the number of impulses in the first pulse. The impulse interval (3.5 ms, n = 2811; SD = 0.68) was similar in the first and the second pulse s (Fig ure 2C), which were separated by an interpulse interval of about 16 ms. The verse interval was about 50 ms. The mean verse duration was 40 ms (Fig ure 4A) , and the mean number of impulses per verse was 8.53 pulses (Fig ure 4B). Disturbance stridulation (Fig ure 2B) could be more easily elicited during the day than during the night and from resting insects than from walking insects . For two males , recordings from both types of sounds were compared (Fig ure 4). The disturbance sound showed three characteristic diff erences to the calling song. First, the disturbance stridulation lasted only a few seconds. Second, the disturbance stridulation consisted of verses with only one pulse. Third, the pulses consisted of about 13 or 14 impulses per verse in contrast to the ma ximum number of 10 impulses per verse in the calling song (Fig ure 4A). The mean number of impulses per verse between the calling song and the disturbance stridulation was significant ly different (Fig ure 4; unpaired t - test; p < 0.0001; t = 45.45; df = 1495; calling song: n = 1262; disturbance sound: n = 235) in both males. However, the duration of the verses of both sounds was not different (Fig ure 4B). The sound pattern resulted in two groups of interval durations (Fig ure 2D). The verse interval wa s rather variable (mean = 98 ms; n = 220; SD = 62.50), but the impulse interval (2.9 ms; n = 2028; SD = 0.78) was invariant and significant ly different from that of the calling song ( p < 0.0001, unpaired T - test, dft = 26.13, df = 4837). Both types of song s had similar frequency spectra within the investigated range with a peak around 15 kHz and a steady decrease in the ultrasonic range (Figure 5) [1].

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