Oecanthus castaneus Felix & Bouwman & Odé & Ketelaar & Pham & Bailey 2025, sp. nov.
Creators: name: Felix, Rob
name: Bouwman, Jaap
name: Odé, Baudewijn
name: Ketelaar, Robert
name: Pham, Duc Minh
name: Bailey, James
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Orthoptera
Gryllidae
Oecanthus
Oecanthus castaneus

description: Oecanthus castaneus Felix & Bouwman sp. nov.
Figs 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172
References for Socotra.
Krauss 1907: 17, 27, 30 [partim; as Oecanthus indicus]; Uvarov (in Uvarov and Popov (1957)): 364–365 [partim; as Oecanthus chopardi]; Gorochov 1993: 92 [partim; as O. chopardi]; Wranik 2003: 316, plates 146, 149 [partim; as O. chopardi]; Chintauan-Marquier et al. 2016: 60, 70 [as O. chopardi]; De Campos et al. 2022: 6 [as O. chopardi].
Material examined.
Holotype. YEMEN ● 1 ♂, on alcohol; Socotra, Aloove area, Aloove vill. env. Jatropha unicostata shrubland with Boswellia elongata trees; 221 m a. s. l.; 12°31.2'N, 54°07.4'E [12.5200°N, 54.1233°E]; 19–20 Jun 2012; J. Bezdĕk, J. Hájek, V. Hula, P. Kment, I. Malenovský, J. Niedobová & L. Purchart leg.; NMPC SpCZ 12 YE 024 A.
Paratypes. YEMEN ● 1 ♂; Sokótra; Jan 1899; O. Simony leg.; NMW ● 1 ♀; Sokótra; Feb 1899; O. Simony leg.; NMW ● 1 ♂ [former paratype of Oecanthus chopardi Uvarov, 1957]; Socotra, Moabbadh plain [Maabad], east of Hadiboh; [12.6377°N, 54.1499°E]; 10–12 Feb 1953; G. Popov leg.; NHMUK 016032520 ● 1 ♂; Socotra, Qualansiyah [Qalansiyah]; [12.6888°N, 53.4877°E]; 25 Mar 1967; K. Guichard leg.; NHMUK 016032747 ● 1 ♀; same as for previous; NHMUK 016032489 ● 2 ♂; Socotra, Hadiboh Plain; 50 m a. s. l.; [12.6216°N, 54.0522°E]; 12 Apr 1967; K. Guichard leg.; NHMUK 016032577, NHMUK 016032824 ● 1 ♀; same as for previous NHMUK 016032601 ● 2 ♀; Socotra, Hadiboh Plain; 30 m a. s. l.; [12.6216°N, 54.0522°E]; 2 May 1967; K. Guichard leg.; NHMUK 016032587, NHMUK 016032767 ● 1 ♀; Socotra, Husaant [Haasan]; 12.5016°N, 54.1452°E]; 29 Nov 1999; W. Wranik leg.; NMPC ● 1 ♀; Socotra, Di Lisha [Di Hashus]; 12°31'48"N, 53°59'08"E [12.5300°N, 53.9855°E]; 4 Apr 2008; B. Massa leg.; BMPC ● 1 ♂; Socotra, Qalansiyah river (Shata) [Bi’r Haarso]; [12.6273°N, 53.6076°E]; 6 Apr 2008; B. Massa leg.; BMPC ● 2 ♂, 3 ♀; Socotra, Wadi Ayehv [Wadi Ayhaft]; 12°37'17"N, 53°56'16"E [12.6213°N, 53.9377°E]; 10 Apr 2008; B. Massa leg.; BMPC ● 1 ♂; Socotra, Wadi Ayhaft; 266 m a. s. l.; 12.6059°N, 53.9927°E; 22 Feb 2009; R. Felix, J. Bouwman & R. Ketelaar leg.; RFPC SpRF 09 YE 327 ● 1 ♀; same data as for previous RFPC SpRF 09 YE 322 ● 1 ♂; Socotra, Ridah [Begobig], Momi Plateau; 350 m a. s. l.; [12.5294°N, 54.2949°E]; 24 Feb 2009; R. Felix, J. Bouwman & R. Ketelaar leg.; RFPC SpRF 09 YE 324 ● 1 ♂; Socotra, Halmi beach; 12°21.324'N, 54°04.780'E [12.3554°N, 54.0796°E]; 16 Jun 2009; V. Hula leg.; NMPC ● 1 ♂; Socotra, Wadi Ayhaft; 266 m a. s. l.; 12.6059°N, 53.9927°E; 26 Oct 2010; R. Felix, J. Bouwman & R. Ketelaar leg.; RFPC SpRF 10 YE 018 ● 1 ♂; Socotra, Hadiboh; 23 m a. s. l.; 12.6453°N, 54.0128°E; 3 Nov 2010; R. Felix, J. Bouwman & R. Ketelaar leg.; Sound recording RecRF 10202–206; RFPC SpRF 10 YE 119 ● 1 ♀; Socotra, Wadi Ayhaft; 200 m a. s. l.; 12°36.5'N, 53°58.9'E; [12.6083°N, 53.9816°E]; 7–8 Nov 2010; J. Hájek leg.; NMPC ● 1; Socotra, Shahab area, Baa vill. env. [Ba’a]; [12.5413°N, 54.1730°E]; 9 Nov. 2010; J. Hájek leg.; NMPC ● 1 ♀; Socotra, Noged Plain, Sharet Halma vill., env.; 20 m a. s. l.; 12°21.9'N, 54°05.3'E; [12.3650°N, 54.0883°E]; 10–11 Nov 2010; J. Bezdĕk leg.; NMPC ● 1 ♂; Socotra, Delisha vill. env. Jatropha unicostata shrubland, at light; 36 m a. s. l.; 12°41.2'N, 54°07.7'E; [12.6866°N, 54.1283°E]; 8 Jun 2012; J. Bezdĕk, J. Hájek, V. Hula, P. Kment, I. Malenovský, J. Niedobová & L. Purchart leg.; NMPC SpCZ 12 YE 032 ● 1 ♀; same as for previous NMPC SpCZ 12 YE 031 ● 1 ♀; Socotra, Noged Plain, Abataro, border of dunes and succulent bush; 20 m a. s. l.; 12°22.1'N, 54°03.4'E [12.3683°N, 54.0566°E]; 12–13 Jun 2012; J. Bezdĕk, J. Hájek, V. Hula, P. Kment, I. Malenovský, J. Niedobová & L. Purchart leg.; NMPC SpCZ 12 YE 039 ● 2 ♂; Socotra, Aloove area, Aloove vill. env. Jatropha unicostata shrubland with Boswellia elongata trees; 221 m a. s. l.; 12°31.2'N, 54°07.4'E [12.5200°N, 54.1233°E]; 19–20 Jun 2012; J. Bezdĕk, J. Hájek, V. Hula, P. Kment, I. Malenovský, J. Niedobová & L. Purchart leg.; NMPC SpCZ 12 YE 024 B, C ● 1 ♀; same as for previous; NMPC SpCZ 12 YE 022 ● 1 ♂; Socotra, Wadi Matyaf (lower part), Noged; [20–30 m a. s. l.]; [12.4505°N, 54.3013°E]; 21 Jan 2014; A. Carapezza leg.; BMPC.
Additional material.
YEMEN ● 1 ♂; Socotra, Hadiboh; 16 m a. s. l.; 12.6488°N, 54.0129°E; 21 Feb 2009; R. Felix, J. Bouwman & R. Ketelaar leg.; RFPC SpRF 09 YE 323 [damaged; only genitalia available] ● 1 ♂; Socotra, Shuab; 8 m a. s. l.; 12.5779°N, 53.4002°E; 1 Mar 2009; R. Felix, J. Bouwman & R. Ketelaar leg.; RFPC SpRF 09 YE 326 [damaged].
Generic placement.
Oecanthus castaneus Felix & Bouwman, sp. nov. (Figs 162, 163), as well as O. chopardi Uvarov, 1957 (Fig. 173), the other tree cricket existing in the Archipelago, belong to the above-mentioned suprageneric ranks, based on the following characteristics, amongst others: the lateral field of the tegmen forming a sharp angle with the dorsal field; ovipositor straight in lateral view; male tegmen with a large mirror with two dividing veins and an almost absent apical field; dorsal valves of the ovipositor bifurcated apically; pseudepiphallic sclerite wider than long, with two main lobes and long rami; arc projecting anteriorly, with two long distal prolongations; cerci longer than FII (De Campos et al. 2022).
The two Socotran species have many characteristics that are considered diagnostic to Viphyus (Otte, 1988): a weakly prognathous head (Fig. 164 A); two thin dark lines bordering the light mid-line of the pronotum (Fig. 164 B), ventral apical spurs on both TI and TII (Fig. 164 E); black spots on the basal antennal segments (Fig. 164 A); spots on the outer surface of the hind femur (Figs 164 C, 165 A); two outer and three inner, dorsal, subapical spurs on TIII (Fig. 164 F); a well-developed metascutum and metascutellum, both more or less of the same length (Fig. 166); extensive dark markings on the tegmina (Toms and Otte 1988). See Cigliano et al. (2024 b) for photographs of Viphyus victorinoxi Otte, 1988, the type species of the genus.
Viphyus, however, has a median scutal tubercle, missing in O. castaneus sp. nov. and O. chopardi (Fig. 166). Furthermore, in Viphyus, the main lobes of the pseudepiphallus in the phallic complex are steeply pointing upwards. In the Socotran species, the main lobes of the pseudepiphallus do not steeply slope upwards (Fig. 168 E, F). At the same time, the pseudepiphallic parameres in the Socotran species differ from those in Viphyus and resemble those of Oecanthus. In (most) Oecanthus, however, there are no ventral apical spurs on TI or TII, only the metascutum is elaborately modified, a median scutal tubercle is presen, and TIII generally has 4–5 pairs of subapical spurs instead of 2–3 (Chopard 1955; Walker and Gurney 1967; Toms and Otte 1988; Collins in litt 2024).
Diagnostic notes.
Oecanthus castaneus Felix & Bouwman, sp. nov. can be separated from O. chopardi by its distinctive warm appearance due to its orange-brown colours and extensive brown markings on the wings (Figs 162, 163). Oecanthus chopardi is never brownish, but always uniformly whitish to pale straw, often with bright greenish tones (Fig. 173). Where the sides of the head, pronotum and legs are orange-brown in O. castaneus sp. nov., they are whitish to pale straw in O. chopardi. Dorsally, the head and pronotum of O. castaneus sp. nov. are darker brown, whereas O. chopardi has greenish tones in those parts (Fig. 173). O. castaneus sp. nov. has almost entirely blackish-brown antennae, except for the lighter scape and pedicle, while in O. chopardi, the antennae are light and of the same colour as the body (Figs 173, 177). The tegmina of O. castaneus sp. nov. are extensively marked blackish-brown, but there is variation in the extent (Fig. 167 A). The base of the tegmina is variably dark brown and the file and the plectrum are flanked with intensive blackish markings (Fig. 167 A, C). There is a large brown spot in the chordal area, halfway to the inner edge of the tegmina. The veins in the distal part of the dorsal field are all bordered brown, the cells are marked with infumated spots and the wing’s apex is heavily infumated (Fig. 167 A). In O. chopardi, the tegmina are translucent white to greenish, with only two small dark markings, one on the distal part of the file bordering the plectrum and a smaller one in the chordal area (Fig. 167 B). The tegmina in male O. castaneus sp. nov. are slightly narrower and shorter than O. chopardi (Table 8; Fig. 167); in females, they are at least shorter (width not measured). The female cerci and ovipositor of O. castaneus sp. nov. are shorter (<4.0 mm and <4.5 mm, respectively) than in O. chopardi (> 4.5 mm and> 5.0 mm, respectively) (Table 8; Fig. 165). In O. castaneus sp. nov., both inner and outer ventral lobes of the hind knee are lined black dorsally (Fig. 165 A), whereas, in O. chopardi, they are only tipped black (Fig. 165 B). The female subgenital plate of O. castaneus sp. nov. is triangular with an obtuse apex; in O. chopardi, it is more trapezoid with a broadly rounded to truncated apex. The metanotum of both species does not differ markedly, which is a common phenomenon in closely-related species (Walker and Gurney 1967).
The stridulatory file in O. castaneus sp. nov. is straight with 45–54 teeth (Fig. 167 C). The only studied specimen of O. chopardi has 59 teeth (Table 8) and a slightly more sinuous file (Fig. 167 D).
The pseudepiphallic sclerite in O. castaneus sp. nov. forms a transverse, narrow bridge with a slightly curved anterior margin in the dorsal view (Fig. 168 A). In O. chopardi, the transverse bridge is broader and the anterior margin is almost straight in dorsal view (Fig. 168 B). The main lobes of the pseudepiphallus differ slightly between both species. In O. castaneus sp. nov., the two lobes point more directly caudal and are somewhat slender, while in O. chopardi, the lobes curve more inwards and are somewhat coarser with a broader base (Fig. 168).
O. castaneus sp. nov. is distinguished from the following three species of Oecanthus known from the Arabian Peninsula: O. pellucens (Scopoli, 1763), O. dulcisonans Gorochov, 1993 and O. turanicus Uvarov, 1912. These three species have a median scutal tubercle, a TIII with 5–6 pairs of subapical spurs and no ventral apical spurs on TI or TII. These species lack the dark markings on the tegmina and the diagnostic colouration of O. castaneus sp. nov.; they all are pale, plain straw-coloured or greenish. O. dulcisonans and O. turanicus are significantly larger (14–17 mm in males).
Description.
Male holotype. Like other species within the genus Oecanthus, it is slender-bodied and fragile (Figs 162, 163). Head: weakly prognathous (Fig. 164 A); head and pronotum with a light mid-line bordered by two thin dark lines (Fig. 164 B); no black postocular marking; scape and pedicel with a small black spot on their ventral face (Fig. 164 A); black dot on the scape sometimes very weak; spot on the pedicel somewhat thickened or callous. Pronotum: as wide as long, sometimes slightly wider than long (Table 8); saddle-shaped with ventral caudal corners of the paranotal lobes strongly curved inwards; hind margin slightly undulated, with bristles (Fig. 164 B). Metanotal gland: metascutum and metascutellum both well-modified and of more or less equal length (Fig. 166); main scutal relief inverted U-shaped with slightly swollen anterior and lateral margins (Fig. 166 a); posteriorly, with two posterad projecting flat processes, both with a tuft of long setal brushes on both sides of their apex; a deep transverse depression situated beneath the two processes; scuto-scutellar suture obtusely trapezoid (Fig. 166 b); main scutellal relief V-shaped, smaller than the scutum (Fig. 166 c), with a U-shaped depression in its anterior face; anterior margin of the scutellum, along the scuto-scutellar suture, with a pair of posterad, hook-like processes, bearing some setae; posterior margin of the scutellum with an obtuse angle; a median scutal tubercle is absent. Right tegmen: veins light; tegmina marked more or less extensively blackish-brown; base of the tegmina dark brown due to the infumation of the cells and margins of the veins; cells bordering the file and the plectrum intensively marked dark brown; chordal area with a large brown spot; cells in the dorsal field thinly margined brown along the veins and variably and locally marked with smooth infumation (Fig. 167 A, C). Stridulatory file: stridulum with 54 teeth, situated on a proximally sharply raised ridge, which gradually descends to the same level as the anal vein towards the plectrum (Fig. 167 C). Hind wings: light-coloured, apex brown, surpassing the tegmina with 2.2 mm. Legs: TI with an oval inner and outer tympanum; TI with an outer, apical, ventral spur; TII with an inner, apical, ventral spur (Fig. 164 E). Fore- and mid-legs with scattered small black spots (Figs 162, 163); FIII with thinly distributed small black spots on the lateral and dorsal outer surface and with black markings on the ventrolateral carinae (Fig. 164 C); TIII with two outer and three inner, dorsal, subapical spurs (Fig. 164 F), serrulated over the entire length, with small, but thick spines on the tibiae’s dorsal margins; serrulation denser in the basal than in the apical part; inner serrulation: no spine before the first subapical spur, 0 spines between the first and second spur, 1–2 spines between the second and third spur and 12–13 above the third spur; outer serrulation: 2–3 spines before the first subapical spur, 3–4 spines between the first and second spurs and 13–14 spines above the second spur; inner, apical three times shorter than inner, apical, dorsal spur; inner, apical, dorsal spur two times longer than outer, apical, dorsal spur; spurs and spines dark; ventral lobe of the hind knee dorsally lined black (Fig. 165 A). Abdomen: cerci slightly sinuous in both the basal and apical fifth and densely covered with long hairs (Fig. 164 D); subgenital plate with a rounded apex (Fig. 164 C). Genitalia: Pseudepiphallic sclerite is a narrow transverse bridge that is widely U-shaped; the anterior margin is slightly curved in dorsal view. Main lobes (MLPs.) placed on the posterior margin, more or less diamond-shaped in dorsal view, with rounded inner sides and angled outer sides; in lateral view, MLPs angled obliquely up- and backwards, resembling two triangular blades or scoops; inner space between the two main lobes slightly smaller than the width of one lobe at its base. Two widely-rounded, triangular pseudepiphallic apodemes (Ps. Ap.) directing anteriorly. Pseudepiphallic parameres (Ps. P.) much shorter than MLPs., rounded apically and directed inwards. Rami long and slender; arc projecting anteriorly, with two long distal prolongations and two short ectophallic apodemes (Ec. Ap.) (Fig. 168).
Colouration: sides of the head yellowish to orange, dorsally orange-brown to brown; eye colour orange-light reddish-brown (in vivo); scape and pedicel orange to orange-brown, the remaining antennomeres blackish brown; tarsi, tibiae and femora light yellow to orange-brown, gradually darkening towards the joints (Figs 162, 163); abdominal tergites largely coloured dark brown with light margins (Figs 162, 163); sternites light; cerci light; subgenital plate mottled brown at its base, rest light yellow.
Morphometrics holotype. Body length (anterior margin labrum – apex subgenital plate): 11.7 mm; pronotal length: 1.9 mm; pronotal width: 2.0 mm; right tegmen length: 10.3 mm; width dorsal field right tegmen: 3.6 mm; total width right tegmen: 5.4 mm; cercus length: 4.2 mm; FIII length: 7.1 mm; TIII length: 8.0 mm; stridulatory file length 1.4 mm; stridulatory teeth number 54.
Female. Same as male, except for the following characteristics: tegmina dark brown on the dorsal and lateral fields, translucent along the transition between the dorsal and lateral fields; due to light underwings, tegmina appear to be striped (Fig. 172); ovipositor short, apex denticulated; cerci slightly surpassing the apex of the ovipositor (Fig. 165 C); subgenital plate triangular with a rounded apex.
Biometrics of holo- and paratypes are shown in Table 8.
Variation.
In the paratype series, the extent of black markings varies, whether on the wings, legs or antennae and may fade in dried specimens. See Table 8 for variation in biometrics in the paratype series.
Discussion.
Based on its characteristics, mainly the ventral apical spurs on both TI and TII, O. castaneus sp. nov. (and O. chopardi) might merit assignment to Viphyus or a new genus close to the latter. However, taxonomic changes at this level should preferably be accompanied by a thorough phylogenetic analysis, based on DNA. Therefore, we tentatively describe the species here as a member of Oecanthus and leave the decision about the generic placement of both Oecanthus species from Socotra to a future study.
Etymology.
Oecanthus castaneus Felix & Bouwman, sp. nov. is named after its warm brown appearance due to a combination of orange and brown hues. This characteristic distinguishes the species immediately from O. chopardi, the other tree cricket species on the island.
Distribution and occurrence.
Endemic to Socotra. The species occurs throughout the island and is common, possibly less so higher in the mountains (Fig. 169).
Habitat and biology.
The species occurs in all vegetated habitats, from 0–900 m a. s. l. and can be found in herbs, shrubs and trees like Jatropha unicostata and Croton socotranus. Records are from all seasons.
Bioacoustics.
The calling song of Oecanthus castaneus Felix & Bouwman, sp. nov. is a continuous echeme, sometimes mixed with very short silences (50–100 ms) (Figs 170 A, 171 A). Echemes consist of equal syllables, repeated at 48–60 per second (Figs 170 B, 171 B). The carrier frequency of the song is around 3.7–4.4 kHz and has few harmonics at higher frequencies (Figs 170 C, 171 C).
Remarks.
Chintauan-Marquier et al. (2016) genetically analysed a specimen from Ayhaft. It is mentioned there as Oecanthus chopardi, the only species known to the island at the time of publication. The same applies to De Campos et al. (2022). Sequences of O. castaneus sp. nov. are stored in GenBank (as O. chopardi) with voucher numbers KR 904148.1, KR 903784.1, KR 903493.1, KR 903270.1 and KR 902990.1.
description: Published as part of Felix, Rob, Bouwman, Jaap, Odé, Baudewijn, Ketelaar, Robert, Pham, Duc Minh & Bailey, James, 2025, The grasshoppers and crickets (Orthoptera) of the Socotra Archipelago (Yemen): a comprehensive overview and a description of a new Oecanthus Tree Cricket (Oecanthidae), pp. 21-166 in Contributions to Entomology 75 (1) on pages 21-166, DOI: 10.3897/contrib.entomol.75.e144389