Chorthippus angulatus Tarbinsky, 1927

Vedenina, Varvara, Tishechkin, Dmitry, Kovalyova, Evgenia & Sevastianov, Nikita, 2025, A new species of the subgenus Chorthippus Fieber, 1852 (Orthoptera: Acrididae: Gomphocerinae: Chorthippus) from Kazakhstan and Kyrgyzstan, closely related to C. angulatus Tarbinsky and C. karelini (Uvarov), Zootaxa 5653 (2), pp. 246-262 : 254-255

Chorthippus angulatus Tarbinsky

Chorthippus angulatus Tarbinsky, 1927: 203 .

Material examined. Kazakhstan: 7 Almaty, environs of Zoology Institute, 01.07.1994, 12♂, 1♀, leg. D. Tishechkin ( ZMMU), song recordings in 7 ♂; Almaty, Botanic Garden, 28.06.1994, 4♂, leg. D. Tishechkin ( ZMMU); environs of Chemalgan , 20 km W of Almaty, 08.07.1994, 2♂, leg. D. Tishechkin ( ZMMU); Jetisu region , Alakol district , ab. 7, 5 km S of Koktuma, N 45°47.739’, E 81°38.271’, 655 m a.s.l., 26.06.2023, 1♂, 1♀, leg. V . Vedenina, N. Sevastianov & T . Tarasova ( CV); 8 Jetisu region, Kerbulak district, environs of Basshi , along stream, N 44°10.136’, E 78°45.064’, 988 m a.s.l., 05.07.2016, 4♂, 1♀, leg. V . Vedenina & T . Pushkar ( CV), song recordings in 2♂; same locality, 22.06.2023, 3♂, 2♀, leg. V . Vedenina, N. Sevastianov & T . Tarasova ( CV), song recordings in 3♂; Jetisu region, Panfilov district , ab. 6 km SW of Zharkent, N 44°08.431’ E 79°55.325’, 594 m a.s.l., 21.06.2023, 1♂, leg. V . Vedenina, N. Sevastianov & T . Tarasova ( CV); Jetisu region, Kerbulak district, Altyn-Emel pass, N 44°12.606’, E 78°30.392’, 1667 m a.s.l., 22.06.2023, 1♂, leg. V . Vedenina, N. Sevastianov & T . Tarasova ( CV); Almaty region, Kegen district, ab. 4 km SE of Kegen, flood-lands of Kegen river , N 42°59.65’, E 79°16.47’, 1824 m a.s.l., 20.06.2023, 1♂, leg. V . Vedenina, N. Sevastianov & T . Tarasova ( CV); Semipalatinskaja gub., 12.08.1895, 1♂, leg. I. V . Ingenitzkii ( ZMMU); Semirech’je, B. Almatinka , 25.07.1928, 1♀, leg. Shnitnikov ( ZIN) ; Uzbekistan: 1♂, Tashkent, Turkest. Expedition of A.P. Fedchenko, 1868 ( ZMMU); Tashkent , 18.0?.1871, 2♂, leg. A. Fedchenko ( ZMMU) . Kyrgyzstan: Issyk-Kul’, 28.07.1903, 1♀, ( ZMMU); Suzak, 19.07.1935, 1♂, leg. D. Dovnar ( ZMMU); Semirech’je , Issyk-Kul’ , 15.07.1927, 1♀, leg. Zheludkova ( ZMMU); Belovodskoe , 12.07.1935, 1♂ ( ZMMU); Issyk-Kul’ , river Chon , Kyzyl-Su, 31.08.1962, 1♀, leg. R . Zlotin ( ZMMU) .

Distribution. The species inhabits the southern and south-eastern Kazakhstan and Central Asia. We can’t exclude the occurrence of this species in the north-western China.

Morphology. The males of C. angulatus can be distinguished from those of the C. albomarginatus group and of the new species by almost straight R vein of tegmen ( Fig. 7 C ). Thus, R field is relatively narrow in C. angulatus . This is the reason why the ratio of C+Sc areas width to R area width of tegmen is the largest in C. angulatus in comparison to C. karelini and the new species, despite this difference is not significant (Table, Fig. 5 B ). The similar differences between C. angulatus and other species mentioned, but weaker, can be found in females (Table). Both sexes of C. angulatus differ from C. karelini and C. kegenicus by tegmen tapering towards the tip and frequent absence of stigma ( Fig. 7 C, D ). The structure of stridulatory file strongly differs between C. angulatus and C. karelini . In males of C. angulatus , the proximal pegs arrange in one row ( Fig. 4 E ), whereas they arrange in two or even three rows in C. karelini males. In the C. angulatus females, stridulatory pegs are well-developed ( Fig. 4 F , 6 C ), whereas they are thin and resemble the bristle stumps in the C. karelini females. The differences in stridulatory files between C. angulatus and C. kegenicus are relatively weak: the male proximal pegs arrange in a straight row in C. angulatus but in a slightly sinuous row in the new species.

Calling song. The calling song of C. angulatus is a series of about 10 echemes lasting for 0.9–1.1 s and separated by intervals of 0.7–1.4 s ( Fig. 8 A–C ). Each echeme is composed of 19–25 syllables repeated at the rate of 22–40 /s. Oscillographic analysis shows that the legs produce a soft sound during upstroke and a louder pulse during downstroke. At the very beginning of every echeme, the legs are usually lifted higher, producing the first syllable slightly longer than the subsequent syllables ( Fig. 8 C ). Moreover, one leg is often moved higher than the other leg at the beginning of echeme, and the two legs change their roles on the next echeme. Nevertheless, the two legs are always moved synchronously.

The calling song of C. angulatus strongly differs from the calling songs of C. kegenicus and C. karelini . The syllable number per echeme is about four times more in C. angulatus than in C. kegenicus ; the syllable rate is at least three times higher in C. angulatus than in C. kegenicus . The calling songs of these two species are, however, similar in the echeme duration and period. The difference between the calling songs of C. angulatus and C. karelini is even stronger: the echeme duration is twice more in C. angulatus than in C. karelini , and the pulse rate within echeme is about 4-5 times less in C. angulatus , than in C. karelini .

Courtship song. The courtship song starts with the small-amplitude movements of the hind legs, which generate short syllables repeated at the rate of about 5/s (element 1, Fig. 8 D, E ). The syllables contain 3–4 pulses of variable amplitude, which are only produced during synchronous down leg-movements. In about 0.5–1 min, there comes an element 2; in contrast to the element

1, it is produced by rather complex leg movements. Each leg alternate low- and high-amplitude movements, and the two legs are moved alternately: one leg produces the high-amplitude upstroke, whereas the other leg produces the low-amplitude upstroke. During the downstroke, both legs vibrate at the rate of 20–30/s ( Fig. 8 F ). During the upstroke, a loud pulse of longer duration is generated; during the downstroke, several (2–4) short, quieter pulses are produced. The syllables are repeated at the rate of about 5–6/s. The element 2 lasting from 3 to 15 s is followed by an element 3, which is similar to the calling echeme of C. angulatus . The leg movements are identical to those during the calling echeme, however, the sound syllables are much softer than during the calling song. The element 3 may include one echeme of the calling type or several echemes ( Vedenina et al., 2020). Usually, the element 3 alternates with the element 2 for more than 1 min.

The courtship songs between C. angulatus and C. karelini strongly differ.As it was written above, the courtship song of C. karelini includes five elements, which alternate in a very specific order. After a long alternation of the elements 1 and 2, the complex of three other elements is repeated two or three times, accompanied by visual display (the stroke by hind tibiae). By contrast, the courtship songs of C. angulatus and C. kegenicus have some similarities, despite they are clearly conspecific ( Figs. 8 , 10 ). The element 1 is similar in the songs of both species, but elements 2 and 3 are different both in the leg-movement patterns and the sound produced. In the element 2, the syllable rate and the pulse rate are higher in C. angulatus than in C. kegenicus . The element 3 in the C. angulatus courtship is similar to the calling song, which is produced by relatively simple leg movements, whereas the element 3 in C. kegenicus is the most complex element in terms of the leg movements.

Figures

FIGURE 4. Proximal part of the stridulatory file on inner side of hind femur: Chorthippus karelini male (A), female (B); C. albomarginatus male (C), female (D); C. angulatus male (E), female (F); C. kegenicus sp. nov. male (G), female (H). Scale 200 mkm.

FIGURE 5. Morphological differences between males of Chorthippus karelini (blue circles), C. angulatus (green triangles), and C. kegenicus (red squares). (A) peg number (ln) vs. ratio of tegmen length to distance between tegmen base and bifurcation of M vein; (B) ratio of prozona length to pronotum length vs. ratio of C+Sc areas width to R area width of tegmen.

FIGURE 6. Proximal and middle parts of the female stridulatory file on inner side of hind femur: Chorthippus karelini (A); C. albomarginatus (B); C. angulatus (C); C. kegenicus sp. nov. (D). Scale 100 mkm.

FIGURE 7. Tegmina of Chorthippus karelini male (A), female (B); C. angulatus male (C), female (D); C. kegenicus sp. nov., paratypes, male (E), female (F) and C. kegenicus sp. nov., paratypes, head and pronotum, dorsal view in male (G) and in female (H). Scale 2 mm.

FIGURE 8. Oscillograms of the calling song (A–C) and the courtship song (D–F) in Chorthippus angulatus from Kazakhstan (locality 8). Song recordings are presented at three different speeds (faster oscillograms of the indicated parts of the songs shown in B–C and E–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, element 1 is presented in (E).

FIGURE 10. Oscillograms of the courtship songs in Chorthippus kegenicus sp. nov. from Kazakhstan, locality 9 (A) and locality 10 (B). Song recordings are presented at two different speeds (faster oscillograms of the indicated parts of the songs shown in C–E). 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.