Odontolabis pareoxa vietnamensis Yamamoto & Pham, 2025

Odontolabis pareoxa vietnamensis Yamamoto & Pham , new subspecies

( Figs 1–6 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 ; 7C View FIGURE 7 )

Odontolabis pareoxa View in CoL : Bartolozzi & Bambi 2019: 266.

Odontolabis sp. : Maruyama 2024: 31, 91.

Type locality. Vietnam, Yên Bái .

Type material. (11♂♂). Holotype: ♂ (telodont form), “N. Vietnam: / Yen Bai, / July 2023 ” ( IEBR) . Paratypes (n=10): 1 ♂ (priodont form), Mù Cang Chải , Yên Bái, Vietnam, June 2020 ( IEBR) ; 1 ♂ (telodont form), same data, but August 2021 ( IEBR) ; 1 ♂ (telodont form), same data, September 2022 ( IEBR) ; 1 ♂ (amphidont form), same data, but June 2023 ( IEBR) ; 1 ♂ (amphidont form), Yên Bái, North Vietnam, June 2020 ( IEBR) ; 1 ♂ (telodont form), same data, but July 2020 ( IEBR) ; 2 ♂♂ (mesodont form), same data, but May 2021 ( IEBR) ; 1 ♂ (telodont form), same data, but June 2021 ( IEBR) ; 1 ♂ (telodont form, damaged), same data, but August 2021 ( IEBR) .

Diagnosis. The new subspecies is closely allied to the nominotypical subspecies in general appearance but can be differentiated by the following combination of characters in the males:

1) Post-ocular margin less developed, only weakly to moderately produced laterally ( Fig. 7C View FIGURE 7 ), rather than strongly projecting laterally ( Fig. 7A, B View FIGURE 7 );

2) Pronotal anterolateral margins, particularly in the telodont form, usually smooth and rounded (sometimes only weakly emarginate) ( Fig. 7C View FIGURE 7 ), instead of apparently roundly emarginate ( Fig. 7A, B View FIGURE 7 );

3) Pronotal anterior angles more or less rounded ( Figs 4A View FIGURE 4 ; 7C View FIGURE 7 ), whereas those being angulate in O. pareoxa pareoxa ( Fig. 7A, B View FIGURE 7 );

4) Pronotal posterolateral angles, especially in the telodont form, only weakly emarginate ( Fig. 7C View FIGURE 7 ), rather than deeply and strongly emarginate ( Fig. 7A, B View FIGURE 7 ).

Description of holotype, telodont male. Size small for the genus, BLM: 45.3 mm. Measurements of different body parts in millimetre (mm): BL, 33.5; BW, 16.4; ML, 12.2; HL, 6.1; HW, 13.1; PL, 8.5; PW, 16.4; EL, 19.1; EW, 15.7.

Body ( Fig. 1A–C View FIGURE 1 ) rather narrowly elongate, about 2.8 times (with mandibles) longer than wide. Surface ( Fig. 1A–C View FIGURE 1 ) generally glabrous; dorsal surface matte in forebody, but strongly glossy in elytra ( Figs 1A View FIGURE 1 ; 3A View FIGURE 3 ). Color uniformly blackish-brown to black; tarsi ventrally with yellowish-reddish brown fine and dense setae.

Head ( Figs 1A–C View FIGURE 1 ; 3A View FIGURE 3 ; 4A, C, D View FIGURE 4 ) comparatively small, rectangular, moderately transverse, about twice as wide as long, widest across post-ocular projection, maximum width narrower than that of pronotum or elytra; surface matte textured; anterior margin broadly emarginate, somewhat vertically, shield-like in frontal view ( Fig. 4D View FIGURE 4 ); pre-ocular margin with canthus well developed, flattened, with broadly arcuate lateral margin ( Fig. 4A View FIGURE 4 ); post-ocular margin or temple ( Figs 1A View FIGURE 1 ; 4A View FIGURE 4 ) somewhat projecting laterally, very slightly beyond level of ocular canthus; frons and vertex with large and shallow depression forming inverted triangle. Eyes ( Figs 1A–C View FIGURE 1 ; 3A View FIGURE 3 ; 4A, C View FIGURE 4 ) moderately large, each completely margined with developed canthus. Mandibles ( Figs 1A–C View FIGURE 1 ; 3A View FIGURE 3 ; 4A, C View FIGURE 4 ) long, slender, L-shaped, strongly curved near basal 1/3, about 2.0 times as long as head, shorter than head capsule and pronotum combined; first (basal) inner teeth short, inconspicuous, weakly directed inwards; median inner teeth absent; subapical longest (2 nd) inner teeth short, simply pointed inward, with serration consisted of two small teeth between 2 nd inner teeth and apex of mandibles ( Fig. 4A View FIGURE 4 ). Clypeus small, narrow, weakly produced anteriorly, not visible dorsally. Antennae ( Fig. 4A, C View FIGURE 4 ) with three-segmented club. Mentum ( Fig. 4C View FIGURE 4 ) strongly transverse, trapezoidal, about 2.7 times wider than long, with weakly bilobate anterior margin, lacking keel in middle.

Pronotum ( Figs 1A View FIGURE 1 ; 3A View FIGURE 3 ; 4A View FIGURE 4 ) short and wide, about 1.9 times wider than long; anterior margin with median area only weakly produced apically; pronotal anterolateral margins smooth, arcuate (not roundly emarginate); pronotal anterior angles rounded, rather than angulate; lateral margins in apical 3/4 almost parallel (except apical narrrowing), only very weakly narrowed apically; basolateral margins rather weakly emarginate, forming obtusely acute posterolateral angles; posterior margin moderately sinuate; disc leathery, uniformly finely granulate. Prosternal process between procoxae ( Figs 1C View FIGURE 1 ; 4C, D View FIGURE 4 ) strongly produced, subparallel-sided, with rounded apex. Scutellum ( Fig. 4A View FIGURE 4 ) subtriangular, slightly wider than long, uniformly black; surface leathery, finely granulate.

Elytra ( Figs 1A View FIGURE 1 ; 3A View FIGURE 3 ) long, elongate-oval, about 1.2 times longer than wide, broadest in basal 1/4; shoulders obtusely angulate; lateral margins broadly curved; surface smooth, very strongly glossy, coarsely very finely punctate, without metallic sheen.

Legs ( Figs 1A–C View FIGURE 1 ; 3A View FIGURE 3 ; 4A, C View FIGURE 4 ) short; protibiae somewhat thick, straight, gradually widened apically, with three noticeable and one inconspicuous teeth and apical bifurcate paired teeth along outer margins in apical half ( Fig. 4A, C View FIGURE 4 ); protibial teeth short, moderately developed, somewhat wide but acutely projecting; mesotibiae straight, with row of yellowish dense microsetae along inner edges, outer margins without external spines, apices with large apical spines; metatibiae similar structure and size with mesotibiae (but with shorter apical outer spines), as long as metatarsi.

Abdomen ( Fig. 1B View FIGURE 1 ) short, broad, strongly tapering posteriorly; ventrite V about 1.3 times as long as ventrite IV, with feebly medially emarginate apex. Tergite VIII ( Fig. 5A View FIGURE 5 ) crescent shape, with membranous band along basal (anterior) margin, with incised longitudinal membranous area along midline of basal half. Sternite VIII ( Fig. 5B View FIGURE 5 ) very strongly transverse, with small emargination along basal margin medially. Pleurite IX ( Fig. 5C View FIGURE 5 ) not conterminous dorsally, well separated by membranous area. Sternite IX ( Fig. 5D View FIGURE 5 ) with posterior margin weakly sclerotized.

Aedeagus ( Fig. 6A–D View FIGURE 6 ) elongate, about 2.9 times longer than wide; basal piece ( Fig. 6B–D View FIGURE 6 ) slightly longer than parameres, moderately constricted in basal part, constriction somewhat narrowed in dorsal and ventral views ( Fig. 6B, C View FIGURE 6 ) or nearly straight in lateral view ( Fig. 6D View FIGURE 6 ); flagellum thick and very long, weakly expanded at apex; parameres simple, with apex curved outward, acutely pointed in lateral view ( Fig. 6D View FIGURE 6 ).

Variation. Male paratypes (n=10). Large sized (i. e., telodont form) males much more easily and frequently found than those of nominotypical subspecies (cf. BLM: 28.0– 45.2 mm in O. pareoxa pareoxa ; Maruyama 2024). Telodont form ( Figs 1D–F View FIGURE 1 ): body shape and size (BLM: 42.4–46.3 mm (average 44.68± 1.79 mm, n=5)) generally similar to the holotype without evident morphological variations, but one specimen ( Fig. 1E View FIGURE 1 ) with protibial teeth seemingly more developed. Mesodont and amphidont forms ( Figs 2A, B View FIGURE 2 ; 3B, C View FIGURE 3 ; 4B View FIGURE 4 ): body size (BLM: 35.1–38.6 mm) smaller, with mandibles similar to those of mesodote and amphidont forms in O. pareoxa pareoxa and O. platynota ; head with anterior margin not shield-like in frontal view ( Fig. 4E View FIGURE 4 ; protibiae and other features generally matched with the holotype). Priodont form ( Figs 2D–F View FIGURE 2 ; 3D View FIGURE 3 ; 4E View FIGURE 4 ): body size (BLM: 30.8 mm) much smaller, with short and entirely serrate mandibles; head with anterior margin not shield-like in frontal view ( Fig. 4E View FIGURE 4 ), post-ocular projection slightly but more produced ( Fig. 2D View FIGURE 2 ); protibiae and other features generally matched with the holotype. Measurements of the paratypes (n=10) in millimetres: BLM, 30.8–46.3; BL, 26.2–34.5; BW, 12.9–16.4; ML, 4.6– 13.1; HL, 4.1–6.9; HW, 9.2–13.4; PL, 6.8–8.7; PW, 12.9–16.4; EL, 16.1–20.2; EW, 12.4–16.1.

Female. Unknown.

Etymology. This new subspecies is named after the country of origin, Vietnam.

Distribution. Vietnam (Yên Bái, but also in Lào Cai based on Bartolozzi & Bambi 2019).

Bionomics. The detailed lifestyle has not been known yet, although the specimens were collected from early to late summer (May–September).