Chorthippus miramae (Vorontsovsky)

Tarasova, Tatiana, Tishechkin, Dmitry & Vedenina, Varvara, 2021, Songs and morphology in three species of the Chorthippus biguttulus group (Orthoptera, Acrididae, Gomphocerinae) in Russia and adjacent countries, ZooKeys 1073, pp. 21-53 : 21

Chorthippus miramae (Vorontsovsky)

Stauroderus miramae Vorontsovsky, 1928a: 12.

Stauroderus mollis porphyroptera Vorontsovsky, 1928b: 31, 34.

Chorthippus porphyropterus (Vorontsovsky, 1928): Benediktov, 1999: 42.

Material examined.

Russia: 29 Krasnodarsky kray, environs of Gelendzhik, 06.X.2011, 8 ♂ 4 ♀, leg. V. Vedenina & L. Shestakov, song recordings in 3 ♂ (ZMMU); 30 Krasnodarsky kray, Gelendzhik district , environs of Aderbievka, 07.VII.1997, 8 ♂ 8 ♀, leg. D. Tishechkin, song recordings in 4 ♂ (ZMMU); 31 Krasnodarsky kray, Gelendzhik district , environs of Praskoveevka; 12.VII.1997, 2 ♂, leg. D. Tishechkin (ZMMU); 36 N. Caucasus, N. Ossetia, environs of Alagir, Ardon river floodplain, 09.VIII.1990, 2 ♂ 2 ♀, leg. M. Bukhvalova, song recordings in 2 ♂ (ZMMU); 37 N. Caucasus, N. Ossetia, Sunzhensky range, environs of Elkhotovo, 10-12.VIII.1990, 2 ♂ 1 ♀, leg. M. Bukhvalova (ZMMU); 38 N. Caucasus, N. Ossetia, Sunzhensky range, environs of Bekan lake , 14.VIII.1985, 3 ♂ 3 ♀, leg. D. Tishechkin (ZMMU); 47 Orenburg region, environs of Studentzy, 14.VII.2012, 1 ♂, leg. V. Vedenina & L. Shestakov, song recordings in 1 ♂ (CV); 48 Orenburg region, environs of Guberlya railway station, 07-09.VII.1996, 37 ♂ 13 ♀, leg. D. Tishechkin, song recordings in 5 ♂ (ZMMU), 29.VI.2018, 1 ♂, leg. V. Vedenina & N. Sevastianov, song recordings in 1 ♂ (CV); 69 Altai Republic, ab. 26 km SE of Ongudai, environs of Kupchegen’, 08.VIII.2017, 5 ♂ 3 ♀, leg. V. Vedenina & N. Sevastianov, song recordings in 1 ♂ (ZMMU); 70 Tyva republic, environs of Erzin, Tore-Kchan' lake , 31.VII.1989, 1 ♂ 1 ♀, leg. S. Byzov (ZMMU); 71 Tyva republic, environs of Erzin, Erzin river floodplain, 20.VII-06.VIII.1989, 3 ♂ 3 ♀, leg. M. Bukhvalova, song recordings in 3 ♂ (ZMMU); 72 Tyva republic, environs of Erzin, Tes-Kchem river floodplain, 03-06.VIII.1989, 3 ♂, leg. M. Bukhvalova (ZMMU); 73 Irkutsk region, Nizhneudinsk district , Uk river estuary, confluence with Uda, 02.VII.2003, 5 ♂, leg. D. Tishechkin, song recordings in 5 ♂ (ZMMU); 74 Buryatia, Selenginsk district , 5 km N from Novoselenginsk, Selenga river valley, 07.VII.2007, 5 ♂, leg. D. Tishechkin, song recordings in 5 ♂ (ZMMU); 76 Buryatia, Zaigrayevo district , 10 km Onokhoy, Bryanka river valley, 21.VII.2007, 3 ♂, leg. D. Tishechkin, song recordings in 3 ♂ (ZMMU) ; Kazakhstan: 46 West-Kazakhstan region, ab. 50 km W of Ural’sk, environs of Kamenka, 23.VI.2018, 5 ♂, leg. V. Vedenina & N. Sevastianov (ZMMU); 50 Kostanay region , Naurzum nature reserve , 04-11.VIII.1938, 13 ♂ 6 ♀, leg. Derevitskaya, 11.VIII-25.IX.1939, 3 ♂ leg. Pokrovskyi, 24.VII.1947, 1 ♂ A. Formozov (ZMMU); 52 Akmola region , Tselinograd district , ab. 4 km SWW from Zhaynak, 09.VII.2019, 3 ♂, leg. V. Vedenina, N. Sevastianov & T. Tarasova, song recordings in 1 ♂ (CV); 55 Akmola region , Arshaly district , 7 km N Vishnevka, Ishym river floodplain, 11.VII.2019, 3 ♂, leg. V. Vedenina, N. Sevastianov & T. Tarasova, song recordings in 2 ♂ (CV); 56 Akmola region , Jerementau district , 4.5 km NE from Baysary, 03.VII.2019, 2 ♂, leg. V. Vedenina, N. Sevastianov & T. Tarasova, song recordings in 2 ♂ (CV); 59 Pavlodar region , Ekibastuz district , ab. 3 km W of Schidert, 04.VII.2019, 6 ♂ 1 ♀, leg. V. Vedenina, N. Sevastianov & T. Tarasova, song recordings in 3 ♂ (ZMMU); 60 Pavlodar region , Zhelezinsky district , near Pyatiryzhsk, 22.VII 1 ♂ 1 ♀ leg. Ingenitskyi (ZMMU), 05.VII.2019, 2 ♂, leg. V. Vedenina, N. Sevastianov & T. Tarasova, song recordings in 2 ♂ (CV); 61 Pavlodar region , Terenkol' district , bank of the Irtysh river , 05.VII.2019, 6 ♂, leg. V. Vedenina, N. Sevastianov & T. Tarasova, song recordings in 1 ♂ (CV) .

Distribution.

(Fig. 1 ). The range of this species stretches in the form of a ribbon from the Black Sea coast eastwards to Transbaikalia. C. miramae occurs in Krasnodarsky krai and Caucasus, Orenburg region, northern Kazakhstan, Altai, Tyva, Irkutsk region and Transbaikalia. The ranges of C. miramae and C. maritimus overlap in the south-eastern part of European Russia and in surroundings of Baikal Lake.

Recognition.

(Table 1 , Figs 2 , 3 ). C. miramae can be distinguished from most species of the Chorthippus biguttulus group by remarkably long stridulatory file (Fig. 2C ). This feature was previously shown by Benediktov (1999), who described the last distal stridulatory peg to be situated at least at a level of the second tibial spine when tibia is attached to femur. Within the Chorthippus biguttulus group, a similarly long file is only shown in C. biguttulus euhedickei von Helversen, 1989, that occurs in the southern Balkans and Anatolia and in C. maroccanus Nadig, 1986, that occurs in North Africa ( Ragge and Reynolds 1988; Willemse et al. 2009). The latter two taxa, however, are quite different from C. miramae in other morphological characters and songs. In other species of the Chorthippus biguttulus group, the length of stridulatory file is noticeably shorter, and the last distal stridulatory peg is situated at least at the level of the 4th tibial spine when the legs are bent ( Benediktov 1999). Notably, in C. miramae , the number of stridulatory pegs is only slightly higher than in C. maritimus , and can’t be considered as a good character. C. miramae tends to have the longest distance between stigma and the wing tip, and the broadest width of C & Sc areas in comparison to C. maritimus and C. brunneus . The PCA based on 6 morphological characters shows that C. miramae represents a separate cluster from C. maritimus and C. brunneus , but it is stronger in males than in females (Fig. 3C, D ).

Description.

(Table 1 , Figs 2 , 3 ). The head structure as in genus. Ratio length of vertical diameter of eye to maximum length of foveolae 3.2-3.6 in ♂, 2.8-3.2 in ♀; ratio minimum interocular distance to length of subocular groove 0.6-0.8 in ♂, 0.7-1.0 in ♀. Antennae filiform. Median carina distinct and continuous. Prozona slightly shorter than metazona. Lateral pronotal keels distinctly incurved, ratio minimum to maximum widths 2.1-2.6 in ♂, 2.4-2.6 in ♀. Tympanal aperture 2.8-3.3 times in ♂, 2.8-3.4 in ♀ as long as broad. Fore and hind wings well developed in both sexes, wings far surpassing the apices of the hind knee. Width of costal area of fore wing reaches its maximum in the middle or in the last third part (Fig. 2A, B ). Width of subcostal area 0.3-0.35 mm in ♂, 0.2-0.23 mm in ♀ (measured along the line of maximal width of costal area). Ratio width of fore wing to width of C & Sc areas 3.0-3.2 in ♂, 4.3-4.5 in ♀. Length of apical constriction (distance from C and Sc confluence to the wing tip) is a quarter of the wing length. Ratio length between stigma center and the wing tip to the wing length 2.1-2.8 in ♂, 1.8-1.9 in ♀. Hind femur gracile, ratio femur length to maximum width 4.5-4.9 in ♂, 4.6-4.9 in ♀. Stridulatory file remarkably long in both sexes: distance between the last peg and the knee tip 2-2.7 times in ♂, 1.7-2.4 in ♀ as large as length of stridulatory file. In males, stridulatory pegs form one row and have different density along the file (Fig. 2C ). Most proximal part of stridulatory file starts with several rare and dispersed pegs that are followed by more densely disposed pegs. The second part of stridulatory file more prolonged, consisting of more rare pegs with stable inter-peg intervals. In the third, most distal part the peg density decreases proportionally to the length of stridulatory file, and the pegs often do not lay in one raw. In females, stridulatory pegs arranged in one row and distributed rarer than in males. The peg density decreases from the proximal towards the distal parts. The number of stridulatory pegs 118-182 in ♂, 98-157 in ♀. Body coloration similar to coloration of C. maritimus .

Measurements in mm. Body length: 14-18 in ♂, 18-24 in ♀, pronotum length: 2.9-3.3 in ♂, 3.8-4.4 in ♀, fore wing length: 13.3-14.6 in ♂, in 16.4-18.3 in ♀, fore wing width 3.1-3.6 in ♂, 3.2-3.5 in ♀, hind femur length: 9.7-10.4 in ♂, 12.6-14.0 in ♀.

Calling song.

(Table 4 , Figs 5 , 7 ). The calling song of C. miramae includes the two types of randomly alternating echemes, typical Chorthippus maritimus -like and optional Chorthippus brunneus -like echemes. The first echeme type was present in the songs of all 34 males recorded, the second echeme type - in the songs of 28 males. The song usually starts with the Chorthippus maritimus -like echeme, which is similar to the C. maritimus calling song, but lasting shorter (the median duration varies in the range of 0.3-2.9 s). The number of syllables per echeme varies in the range of 5 to 35. Each echeme starts with the low-amplitude syllables. In short echemes, the amplitude reaches its maximum in about the echeme middle (Fig. 7F ). In long echemes, the amplitude gradually increases, and keeps a constant level after about one quarter of an echeme (Fig. 7G ). The syllables are about 1.5 times as short as the syllables in C. maritimus , lasting in the range of about 66-114 ms (Table 4 ). The syllable duration is rather stable within one population; however, it is more variable between populations. Oscillographic analysis shows no distinct pulses within the syllables in some populations, whereas distinct pulses are visible on the oscillograms of the songs from other populations. The shift between the two legs is greater in C. miramae than in C. maritimus (Fig. 7I, J ).

The Chorthippus brunneus -like echemes are more often produced by the males from the Siberian and the east-european Russian populations, but they are rare in the songs from northern Kazakhstan. The echeme duration in C. miramae is almost three times as high as in C. brunneus (Fig. 5A ). Similarly to C. brunneus , the C. miramae echeme consists of the short pulses, the amplitude of which gradually increases, reaching maximum intensity at about half of its duration, and then gradually decreases towards the end. The pulse duration and the pulse rate in C. miramae are almost the same as in C. brunneus (9-13 ms and 77-96 /s respectively, data are given for 29-30°C). However, the leg movement patterns are different in two species. In C. miramae , the Chorthippus brunneus -like echeme is produced by simple up and down leg-movements that vary in amplitude and duration (Fig. 7J ). In C. brunneus , each leg generates a simple upstroke but a two-step downstroke (Fig. 4D ). The oscillographic analysis of the C. miramae song shows that the pulses highly vary in amplitude and duration, whereas the pulses in the C. brunneus song are much more stable in these parameters. In some males of C. miramae , the pulses are tended to group into syllables; the pulse number per syllable is unstable (Fig. 7H ).

The order of the two echeme types in the C. miramae song is erratic, though there are some common variants in different populations. For example, several Chorthippus maritimus -like echemes are followed by one Chorthippus brunneus -like echeme (Fig. 7D ). Another variant implies alternation of the two echeme types. A rarer case is when one Chorthippus maritimus -like echeme is followed by several echemes of the second type (Fig. 7A, E ). The intervals between echemes of the same type may exceed the echeme duration 1.5-3 times for the Chorthippus maritimus -like echemes, and 3-5 times for the Chorthippus brunneus -like echemes. An interval between the Chorthippus maritimus -like and the subsequent Chorthippus brunneus -like echemes can be very short (Fig. 7F, J ), or can exceed the echeme duration 3-5 times.

Courtship song and female response song.

(Fig. 8 ). The courtship song of C. miramae consists of the Chorthippus brunneus -like echemes. However, the courtship sound is much softer than in the calling song. The courtship echemes are shorter than in the calling song, not reaching 1 s (the median duration is about 0.4 s). The echemes are usually repeated at the rate of about 0.2-0.6/s, and their duration varies from 0.7 to 1.0 s. Pulses are short (6-9 ms), frequent (repeated at the rate of 61-95/s), and of a low amplitude (Fig. 8F ). In some cases, the leg movements do not produce any sound at all (Fig. 8A, D ).

A female produces the Chorthippus brunneus -like song in response to the male courtship or rivalry song (Fig. 8A, B ). The female alternates her response echemes with the male echemes (Fig. 8D ). The duration of the female echeme is similar to that in the male courtship, or 1.5-2 times longer than in the male courtship. The leg movement pattern in the female response song is similar to that in the male courtship song, but less regular (Fig. 8E, F ). The pulses are longer (10-21 ms) and repeated at the rate of 43-77/s, especially in the first third of the echeme (Fig. 8D, E ).

Rivalry song.

(Fig. 9 ). Several males of C. miramae sitting close to each other produce a diversity of echemes of different duration, structure and leg movement pattern. For example, one can find a rivalry song similar to that of C. maritimus , which starts with the prolonged first syllable, which results from the prolonged first downstroke (Fig. 9D, E ). The pulses produced during the first downstroke follow twice as slowly as the pulses of the subsequent syllables. The subsequent syllables are of the same structure as in the Chorthippus maritimus -like echeme of the calling song.

Most often, the males produce single syllables similar to the first one with distinct pulses described above. These syllables are repeated at the rate of about 2-2.5 /s (Fig. 9F, G ). Notably, the two legs may produce different number of the up and down strokes. Rarely, the males produce the Chorthippus maritimus -like echeme without the first syllable of distinct pulses (Fig. 9H ).

The same male may produce echemes of different structure in the rivalry situations. Some females are actively responding to the male rivalry songs.

Figures

Figure 1. Map of localities where the specimens of Chorthippus brunneus (green triangles), C. maritimus (red squares) and C. miramae (blue circles) were collected. The localities with song recordings are numbered and marked by filled icons.

Figure 2. Morphology of fore wing and hind leg in Chorthippus miramae (Vorontsovsky) from Orenburg region A fore wing with complete venation B fore wing with main veins; C hind leg. The measured morphological characters are indicated with arrows and brackets.

Figure 3. Morphological differences between Chorthippus brunneus (green dots), C. maritimus (red dots), and C. miramae (blue dots). A, B length of stridulatory file vs. distance from the last stridulatory peg to the tip of knee in males (A) and females (B) C, D results of Principal Component Analysis based on 6 characters are shown for PC 1 and PC 2 in males (C) and females (D) E loadings of different characters to PC 1 and PC 2.

Figure 4. Oscillograms of calling songs A-E and rivalry songs F, G in Chorthippus brunneus from Kostroma region (A) Poltava region (B) and Saratov region (F). Song recordings are presented at four different speeds (faster oscillograms of the indicated parts of the songs shown in C, D, E, G). In all oscillograms the two upper lines are recordings of hind leg movements and the lower line is the sound recording. Different song parameters are indicated by brackets and arrows. The ambient temperature near a singing male was 29 - 32 ° C.

Figure 5. Differences in calling songs between Chorthippus brunneus, C. maritimus, and C. miramae A-D boxplots for the Chorthippus brunneus - like echeme duration (A) for the Chorthippus brunneus - like pulse rate (B) for the Chorthippus maritimus - like echeme duration (C) and the Chorthippus maritimus - like syllable duration (D) medians (dots), first and third quartiles (boxes), the 10 th and 90 th percentiles (whiskers), and outliers (dots beyond whiskers) are shown E results of Principal Component Analysis based on 5 song characters are shown for PC 1 and PC 2 in C. brunneus (green dots), C. maritimus (red dots), and C. miramae (blue dots) F loadings of different characters to PC 1 and PC 2.

Figure 7. Oscillograms of calling songs of Chorthippus miramae from Orenburg region A, West-Kazakhstan region C and Buryatia D, E. Song recordings are presented at three different speeds (faster oscillograms of the indicated parts of the songs shown in F-J. At small scales (A-D) the Chorthippus maritimus - like echemes can be distinguished from the Chorthippus brunneus - like echemes by the higher amplitude. In all oscillograms the two upper lines are recordings of hind leg movements and the lower line is the sound recording. The ambient temperature near a singing male was 34 - 35 ° C in (A, E) and 29 - 31 ° C in other cases.

Figure 8. Oscillograms of courtship songs and female response songs in Chorthippus miramae from Pavlodar region A West-Kazakhstan region B and Altai republic C. Song recordings are presented at three different speeds (faster oscillograms of the indicated parts of the songs shown in D-F). During courtship, a male can produce audible (C, F) or silent (A, D) variants of song. Female responses with leg movements recordings (B, E) and without them (A, D) are shown. In all oscillograms the two upper lines are recordings of hind leg movements and the lower line is the sound recording. The ambient temperature near a singing specimen was 29 - 31 ° C.

Figure 9. Oscillograms of rivalry songs in Chorthippus miramae from Altai republic A and Pavlodar region of Kazakhstan B, C. Song recordings are presented at three different speeds (faster oscillograms of the indicated parts of the songs shown in D-H). In all oscillograms the two upper lines are recordings of hind leg movements and the lower line is the sound recording. The ambient temperature near a singing male was 29 - 31 ° C.