Bioacoustics of Isophya bureschi

Supplement to the description and a diagnosis : The species shows most primitive features within the group, similar to these of I. cania of the I. rectipennis group. Generally these are expressed in medium body size, more gracile than the other species of I. modesta group, and a very short main (first) part of the syllables of male song. The body colouration is fresh-green. The tegmina are not bulged, equal or slightly longer than the pronotum, green with brownish stridulatory area. The CuP vein is greenish, thin and short (≤2/3 of the width of metazone), clearly separated from CuA. The stridulatory file ( Fig. 139 A) bears low number (68–75) of sparsely arranged teeth. The ventral keels of hind femora are unarmed or have a single tooth each. The cercal tooth ( Fig. 139 B) is long, pointed. Female stridulatory apparatus is shown in Fig. 139 C. Male calling song ( Fig. 145 ) consists of groups of few syllables, each having short main (first) part (30–60 ms) with dense impulses and a second part of few wellseparated impulses (after-clicks). Both parts are separated by a silent interval (due to a pause in the stridulatory movement) and thus the syllable becomes 0.5–1 s.

Bioacoustics : The two investigated populations (from North Pirin Mts—Yundola village, and Sushtinska Sredna Gora Mts—Oborishte place) showed slight variation in the song. At a temperature between 25 and 28°С the song consisted of groups of 2–4 (usually 3) or single syllables. Within the group the syllables were separated by an interval of 0.7–3 s, which duration varied even within the same group and was dependent on the presence or absence of additional impulses (after-clicks) in the syllables. The syllables (main part) were frequently followed by additional part of few after-clicks that was usually missing in the first syllable of the syllable group. The main syllable part lasts 28–48 ms (mean 38±6; n=51) (Т=26–28°С) and consists of 12–25 detectable impulses (mean 19±4; n=46). In the available recordings the main part was “continued” by a low-amplitude echo (see Chobanov and Heller 2010). The additional syllable part (if present) follows after over 500 ms and results from by a delayed closing movement of tegmina producing 2–13 clearly detached impulses. Together with the after-clicks the syllable lasts between 0.5 and 1 s (mean 725±70; n=43).