Bioacoustics of Isophya pavelii

Stridulatory row in 2 studied specimens is about 2.9 mm long, 0.08 mm wide in middle, bearing about 100 (98 and 99) densely distributed teeth (Fig. 3B). Stridulatory row length, teeth number and distribution in I. pavelii and the other studied representatives of the Isophya rectipennis group are compared in Ta- ble 1. Female stridulatory apparatus is shown on Fig. 3C. Song (Fig. 4) description (song terminology follows RAGGE & REYNOLDS 1998 and HELLER et al. 2004). Male calling song consists of sequences (echeme-sequen- ces) of 5-13 syllables (mean 8.2 ±1.8, n=21), repeated in an interval of 9-15(26) s by actively singing males, especially when few males duetting; sometimes the interval is prolonged to more than half a minute. Each sequence starts with a slightly shorter syllable with lower amplitude; while the amlitude fastly reach max- imum in the next 1-2 syllables. The syllables are compact, decrescending, con- sisting of about 30-45 impulses. The length of sequences, syllables and syllables interval (here measured as the syllable and the following interval to the first im- pulse of next syllable) are influenced by the body temperature. At 25 °C the re- spective duration was: sequences 3.7-7.3 s (mean 5.6 ±1.2, n=6) with number of syllables 6-10 (mean 7.5 ±1.4, n=6); first syllable interval 432-596 ms (mean 520 ±57, n=6), next syllable intervals 675-2000 ms (mean 960 ±321, n=34); first syllable ~40-50 ms, next syllables 89-112 (mean 102 ±9, n=5). At 27 °C the dura- tion was: sequences 2.3.-5.5 s (mean 4.7 ±1.2, n=15) with number of syllables 6- 13 (mean 8.5 ±1.9, n=15); syllable intervals 428-846 ms (mean 588 ±107, n=37) (first syllable interval here does not differ much that the others); first syllable 26- 43 ms (mean 35 ±8, n=6), next syllables 54-95 (mean 68 ±11, n=34). The frequency spectrum (Fig. 5) of the song lies between 10 and 20 kHz with a maximum at 13 kHz. Generally the song much resembles those of I nervosa and I. ilkazi (as partly described in HELLER 1990), though good diagnosis is still difficult. On the contrary, the song of I. pavelii well differs from the song of I. rectipennis (see Fig. 5), which consists of echeme-sequences of more syllables (about 30), with a much higher repetition rate. The frequency spectrum is wider and higher – main part between 12 and 32 kHz, with a maximum at about 20 kHz. This is another evidence of the subgrouping within this species group.