Omocestus petraeus (Brisout de Barneville, 1856)

Vedenina, Varvara, Sevastianov, Nikita & Tarasova, Tatiana, 2020, Contributions to the study of the grasshopper (Orthoptera: Acrididae Gomphocerinae) courtship songs from Kazakhstan and adjacent territories, Zootaxa 4895 (4), pp. 505-527 : 511-512

Omocestus petraeus (Brisout de Barneville, 1856)

Distribution. From southern regions of Western Europe to southern Siberia.

Material. Russia: 14. Orenburg region, ab. 10 km W of Novosergievka, 52° 01.2’ N 53° 42.0’ E, 13.07.2012, song recordings in 2 ³; 15. ab. 10 km E of Orenburg, near Ural river , N 51º44.3’ E55º20.8’, 13- 14.07.2012, song recordings in 2 ³; 3 . Kazakhstan, Akmola region, ab. 60 km SE km of Nur-Sultan, near Vjacheslavskoe reservoir, environs of Vishnevka , 50°54.6’ N, 72°12.2’ E, 11.07.2019, song recordings in 3 ³ .

References to song. Faber, 1953: verbal description only, calling and courtship songs; Waeber, 1989: recordings from former Yugoslavia and Turkey, calling and courtship songs; Ragge & Reynolds, 1998: recordings from France, calling and courtship songs; Savitsky, 2005, 2009: recordings from Russia (Volgograd and Astrakhan’ regions), calling song; Tishechkin & Bukhvalova, 2009b: recordings from Russia (Saratov region), calling song; Willemse et al., 2018: recordings from Greece, calling song.

Song. The courtship song usually starts with the small-amplitude movements of one hind leg producing quiet pulses repeated at the rate of 13–19/s (element 1, Fig. 4 A–C). These quiet pulses are followed by an echeme of the calling song type (element 2). The element 2 consists of about 10–20 syllables. Each syllable lasts for about 250–400 ms reaching maximum intensity by half of its duration. All the syllables begin and end quietly, resulting to a spindle-shaped oscillogram. The syllable repetition rate is typically about 4/s at the beginning and about 2/s by the end. The syllables are produced either by synchronous ( Fig. 4 E ) or by antiphase movements ( Fig. 4 F ) of the hind legs. As a result, one could distinguish distinct double pulses separated by gaps or the pulses without gaps. The number of the leg movements producing a syllable varies in the range of about 20–30. Upon repetition of several echemes of the calling song type, the element 3 follows. One leg gradually rises and produces several up and down strokes until the leg reaches almost vertical position ( Fig. 4 D ). It is remarkable that almost no sound is produced during this gradual rise. After an abrupt down stroke, the legs vibrate at the rate of 4–6/s generating a syllable that lasts for about 300–400 ms. There come then several synchronous leg strokes followed by an attempt to copulate with a female. The main components of the frequency spectrum of the element 2 lie between 25 and 40 kHz ( Fig. 4 G ).

Comparative remarks. The courtship song of the specimens from Orenburg region and Kazakhstan basically differs from the courtship song of O. petraeus described by Ragge & Reynolds (1998) from France. The authors described the courtship syllables as the calling syllables but of a longer duration and with pulses repeated at the lower rate; no visual display (gradual rise of one leg) was documented in the specimens from France. Additionally, even the calling songs recorded from France ( Ragge & Reynolds, 1998) and former Yugoslavia (Waeber, 1979) differ from the calling songs recorded from Russia ( Savitsky, 2005; Tishechkin & Bukhvalova, 2009b) in the syllable duration (about 150 ms vs. 250–400 ms). The males recorded from Turkey ( Waeber, 1989) also do not produce any visual display. At the same time, the specimens from Austria ( Faber, 1953) produce single strokes with one leg after the main echeme, similarly to those recorded in specimens from Orenburg region and Kazakhstan.

The visual display recorded in O. petraeus from Orenburg region and Kazakhstan appeared to be very similar to the visual display demonstrated by all species of the Stenobothrus stigmaticus group ( Berger, 2008). Based on bioacoustics data, this group includes several west European species: Omocestus antigay (Bolivar, 1897) , O. bolivari Chopard, 1939 , O. femoralis Bolivar, 1908 , O. uhagonii (Bolivar, 1876) , S. apenninus Ebner, 1915 , S. ursulae Nadig, 1986 , and S. stigmaticus (Rambur, 1839) . All species except S. stigmaticus are local endemics of Spain and Italy, and only S. stigmaticus has a wide distribution. During courtship, all these species produce up and down strokes at high amplitude by one leg, while the other leg does not move. Some of these species produce several strokes after the main echeme, with the two alternating legs ( Berger, 2008). Similar visual display during courtship was also recorded in O. minutus Brullé, 1832 ( Waeber, 1989; Vedenina, Mugue, 2011). It should be noted that all species attributed to the S. stigmaticus group and O. minutus have quite similar syllable structure of the calling song and of the main part of the courtship song. By contrast, the structure of the main syllables in O. petraeus greatly differs from the syllable pattern in the S. stigmaticus group and O. minutus . Nevertheless, all these species produce similar up and down strokes by one leg almost without sound in the end of courtship. The similarity of visual display in these species may indicate a common origin.

Figures

FIGURE 4. Oscillograms and frequency spectrum of the courtship songs of two males (A, B) of Omocestus petraeus from Orenburg region. Song recordings are presented at three different speeds (faster oscillograms of the indicated parts of the songs shown in C–F). In all oscillograms the two upper lines are recordings of hind leg movements and the lower line is the sound recording. Different elements of the courtship song are indicated by numbers 1–3. Frequency spectrum (G) shown for element 2.