Bioacoustics of Isophya longicaudata

Diagnosis : The largest species within this complex (hind femur> 20–28 mm ) with the longest ovipositor in the genus (> 17–25 mm ). The body colouration is similar to that in I. plevnensis— bluish- or greyish-green with whitish opalescence. Male tegmina are equal or (usually) longer than pronotum; their disc (the Medio-Anal area) is yellowish-brown, more bulged and membranous than in the other taxa. CuP vein is yellowish, very long (>3/4–>4/ 5 of the width of metazone) and thick, situated closer to CuA in comparison with the other species in the complex. The stridulatory file is longest within the complex (> 3.5 mm ), with 145–160 teeth. The song consists of single syllables, repeated at intervals of few seconds to more than a minute. The syllables are compact (instead of these in I. modesta ) and last 0.5–1 s (at Т°>25°C) to> 1.5 s (at Т°<20°C). Each syllable has 45–80 impulses arranged in two attached parts—first one of compact decrescending impulses, and second one of loose impulses with a fusiform amplitude modulation. This species shows features in the male song pattern and morphology of the tegmen, which clearly distinguish it from I. modesta . Therefore its species status was restored by Chobanov (2009a). The species has two subspecies, distributed along the Western Black Sea coast between the Danube in North and Strandzha Mountains in South (for phenology see the subspecies).

Diagnosis : see Chobanov 2009a. This subspecies shows more primitive features than the nominate one that are transitional to those of I. plevnensis . The differences from I. l. longicaudata are as follows: CuP is shorter and less thick; lateral margins of metazone stronger S-shaped, ovipositor shorter (about 18 mm after Peshev 1985; in I. longicaudata usually> 20 mm ); male song consists of shorter syllables (400–850 ms at 27–28°C) with 58–75 impulses and less clearly differentiated parts. The first syllable part (when distinct) was 285–326 ms long with 43– 64 impulses and impulse period of 5–20 ms, the second part—250–494 ms with 9–19 impulses and impulse period of 11–108 ms (Chobanov 2009a).

Diagnosis : see references above. The nominate subspecies is characterised by longer and thicker CuP vein and longer ovipositior (compare Peshev 1985) and characteristic song. Bioacoustics : We studied specimens from two remote regions. In the specimens from the Bulgarian Black Sea coast (Bolata Bay) at 28-30°C the syllables lasted 850–1100 ms and had 61–76 impulses, arranged in two parts ( Fig. 160 ): first (main) part of dense impulses, produced by fast closing of tegmina—130–170 ms with 32–46 impulses and impulse period of 2–10 ms; second (additional) part of loose impulses, produced by slower closing of tegmina—500–1000 ms with 16–43 impulses and impulse period of 7–217 ms (see Chobanov 2009a). The specimens from the inland Dobrogea (Balik-Pchelnik Villages, Suha Reka Valley, NE Bulgaria ) at 24– 27°C showed similar to the described song structure, while specimens from the neighbouring territory of Romania (Bäneasa, Suha Reka Valley, SE Romania ) showed slight transition to the song of I. modesta : first part—136–146 ms with 21–24 impulses and impulse period of 5–10 ms; second part—1060–1330 ms with 23– 26 impulses and impulse period of 9–178 ms; both parts were clearly separated by intervals of 44–239 ms and thus the total length of the syllable was 1300–1450 ms. A very interesting song is produced by individuals in Central Dobrogea (Cheile Dobrogei, Romania ), with clear transition to the acoustic signals of I. modesta : opening hemisyllable—72–81 ms with 20–27 impulses, impulse period 2–7 ms and a longer closing hemisyllable—270–305 ms with 27–33 impulses, impulse period 4–38 ms. The two hemisyllables are divided by a 75–109 ms time interval.

Diagnosis : The body shape and colouration is similar to that of I. longicaudata— the general colour may be dark green or greyish-green with whitish lateral opalescence. Male tegmina are equal or longer than pronotum, the disc is dark green or yellowish with brown stridulatory area. The disc of tegmina is less bulged than that of I. plevnensis and I. longicaudata . CuP has the colour of the disc of tegmina or is lighter; it is shorter and thinner than that of I. longicaudata , about 2/3–3/4 of the width of metazone. The stridulatory file is 3.1–3.65 mm long with 95– 143 teeth, similar to that of I. plevnensis , shorter and with fewer teeth than that of I. longicaudata . The song has single syllables that, due to an interruption in the stridulatory movement, are divided into two parts separated by an interval of 4–9 seconds, thus the syllable is the longest known within genus Isophya . Considering each of the parts separately, they are in amplitude and time pattern similar to those in the song of I. l. longicaudata (compare Figs 160 and 161 ). The first part lasts 120–240 ms (Т=19–27°C) and has 16–46 impulses, the second—200–2500 ms with 8–44 impulses. As a result of the “splitting” of the syllable (observed for I. m. modesta by Orci and Heller 2004) the females can produce two responses to one syllable of the male—after the first syllable part (main impulse series) and after the second one (terminal impulse series). The species is known with two subspecies distributed in the southeastern part of Central Europe, the Carpathian basin and Southern Ukraine to the southeastern parts of European Russia .