Bioacoustics of Pseudochorthippus geminus

Description. Head somewhat shorter than pronotum; face oblique in lateral view ( Figs 2–5 ). Frontal ridge slightly widened between antennae, its maximum width 2.4 times less than maximum width of vertex between eyes. Fastigium of vertex triangular, depression of vertex shallow, median carina indistinct or visible only due to lighter coloration. Foveolae with distinctly incurved outer margins ( Figs 6–9 ) (with more or less straight outer margins in studied specimens of P. parallelus from Kazakhstan ; Figs 10–11 ), sometimes posteriorly expanding, 2.5–3.5 times as long as their maximum width in specimens from environs of Tokmak and 3.0–3.5 times as long as their maximum width in specimens from environs of Alatau (3.2–3.3 times as long as their maximum width in specimens of P. parallelus from Kazakhstan ). Vertical diameter of eye 1.4 times greater than subocular furrow in female ( Fig. 12 ) and 1.8–2.3 times greater than subocular furrow in males (1.9 greater than subocular furrow in studied males of P. parallelus from Kazakhstan ). Antennae filiform, 23-segmented, 11 th –13 th segments 1.2–2.0 times as long as their width in broadest aspect (studied males of P. parallelus from Kazakhstan have same number and proportions of antennal segments). Visually, pronotum is crossed by main transverse furrow distinctly behind middle, but in fact, length ratio of prozona and metazona measured along middle line 1.0–1.1 ( 1.1 in studied males of P. parallelus from Kazakhstan ). Anterior margin of prozona rounded or almost straight; posterior margins of metazona almost straight, projecting backwards at an obtuse angle. Lateral carinae concave in prozona, slightly divergent or almost parallel in back part of metazona. Length of lateral lobes of pronotum measured along lateral carina exceeds their maximum width by 1.2–1.4 times. Mesosternal lobes are 1.5–1.8 times as wide as mesosternal interspace ( Fig. 13 ), mesosternal interspace trapezoidal, its minimum width 1.0–1.2 of its length along midline, metasternal interspace distinctly longer than its width (proportions of meso- and metasternum in studied males of P. parallelus from Kazakhstan are the same). In males, tegmina not exceed hind knees, only sometimes almost reach bases of darkcolored distal parts of hind femora, with narrowly rounded apices; hind wings shortened, half as long as tegmina ( Figs 2–3 ). In female, tegmina strongly shortened, do not reach middle of hind femora ( Figs 4–5 ). Length of hind femora in both sexes 4.8–5.0 times greater than their maximum width (5.0 times greater than their maximum width in studied males of P. parallelus from Kazakhstan ). Number of stridulatory pegs 102–106 ( 104–113 in P. parallelus from our material; according to Reynolds (1980) , maximum number of pegs in European males of P. parallelus reaches 110). Length of stridulatory file averages 4.0– 4.2 mm (same in P. parallelus from Kazakhstan ). Hind tibiae with 13–14 outer and 12–14 inner dorsal spines (12–13 and 11–13, respectively, in studied males of P. parallelus from Kazakhstan ). Arolium reaches apices of claws, rather long and narrow, its length to maximum width ratio averages 1.5–1.9 (same in P. parallelus from Kazakhstan ). Tympanum wide, oval. Cerci conical, 2.0 times as long as their width at base. In shape of male genitalia indistinguishable from P. parallelus ( Figs 14–17 ). Coloration same as in P. parallelus . In dorsal view, body brown, usually, with variable dark pattern on head and pronotum, ventrally, greenish yellow. Hind femora brown with yellowish ventral and inner parts and dark brown or black knees. Hind tibiae brown, dorsal spines with black apices. In males, end of abdomen usually with reddish tinge. Measurements. Length of head in dorsal view: ♂ , 2.8–3.0 mm, ♀ , 3.6 mm ; length of pronotum (prozona + metazona): ♂ , 3.0– 3.7 mm (1.5–1.9 + 1.5–1.8), ♀ , 4.5 (2.3 + 2.2) mm; length of tegmina: ♂ , 8.2–11.6 mm , ♀ , 7.5 mm ; length of hind wings: ♂ , 5.3–5.8 mm ; length of hind femora: ♂ , 9.1–10.6 mm , ♀ , 12.5 mm . Song. Usually, the calling song of P. geminus is an echeme-sequence consisting of 3–5 echemes following each other with a period of 2–4 s (occasionally, up to 5–10 s; Figs 18–19 ). In both localities studied, the density of insects was very high and the distance between singing males averaged 0.5–1.0 m. For this reason, echemes of different males alternated ( Figs 19, 21, 26 ) and quite often the male produced only one or two echemes, apparently, reacting in this way to the song of another male singing nearby. Number of syllables per echeme varies from 3–4 up to 6–7; echeme duration is 0.23– 0.60 s ( Figs 20–29 ). Syllable repetition period is 70–118 ms in males from the environs of Tokmak, Kyrgyzstan and 52–106 ms in males from the environs of Alatau, Kazakhstan ; most probably, this is due to difference in temperature during recording (30 and 35 o C, respectively), since in all insects, the repetition rate of signal elements increases with temperature. Number and duration of gaps and, as a consequence, the shape of syllables vary greatly even in males from the same locality ( Figs 22–25, 28–29 ). Sometimes, syllables merge with each other and boundaries between them are indistinct ( Fig. 21 ). Temporal pattern of songs of P. parallelus from southern Kazakhstan is the same as in males from Western Europe ( Reynolds, 1980 ; Ragge & Reynolds, 1998 ), European Russia (Tishechkin & Bukhvalova, 2010), semi-deserts of the Lower Volga Region ( Savitsky & Lekarev, 2007 ), and Altai Mts., Western Siberia ( Benediktov, 2005 ). The song is a very long echeme-sequence lasting sometimes for a minute or more ( Fig. 30 ). The number of syllables per echeme in P. parallelus is much higher than in P. geminus and usually averages 10–15; the temporal pattern of syllables is also completely different ( Figs 31–34 ). In males of P. parallelus from Kazakhstan , the syllable repetition period averages 87–109 ms at 35–38 o C; in the songs of the male from Astrakhan Oblast of Russia recorded at 37–39 o C it occupies almost the same range, 95–145 ms ( Savitsky & Lekarev, 2007 ). Thus, in this parameter, songs of P. parallelus and P. geminus are similar, but in other characters they have almost nothing in common with each other.