Diochus robustus Huang, Janák & Zhou, 2025

3. Diochus robustus Huang, Janák & Zhou , sp. nov.

( Figs 1A View FIGURE 1 ; 4-1; 4-2)

Type locality. Thailand: NE Bangkok.

Type material. Holotype: male, THAILAND: NE Bangkok: Khao Yai Nat. Park, E Heo Suwat Waterfalls , 800−900 m, 1. XII. 1985, Burckhardt-Löbl ( MHNG) . Paratypes: THAILAND: 4 females, same data as holotype ( MHNG, JJRC) . Holotype with an identification label: “ HOLOTYPUS Diochus robustus sp. nov. Huang, Janák & Zhou det. 2024”. Paratypes with identification labels: “ PARATYPUS Diochus robustus sp. nov. Huang, Janák & Zhou det. 2024”.

Measurements. BL = 7.63 mm, FL = 2.96 mm, HL = 0.77 mm, HW = 0.57 mm, EyL = 0.19 mm, TL = 0.47 mm, ANL = 1.72 mm, ANT1 = 0.24 mm, ANT2 = 0.15 mm, ANT3 = 0.22 mm, ANT4 = 0.15 mm, ANT 11 = 0.18 mm, PL = 1.03 mm, PW = 0.81 mm, EL = 1.06 mm, EW = 1.10 mm, SL = 0.74 mm.

Description. Body long, narrowed anteriorly and posteriorly, large sized. Body light brown, abdominal intersegmental membrane lighter. Legs yellowish brown, tarsi distinctly lighter. Antennae dark brown to yellowish brown, apex of each antennomere lighter. Maxillary and labial palpi yellowish brown.

Head (Fig 4-1A). Oblong in shape, 1.36 times as long as wide. Tempora straight and parallel, posterior angles rounded. Dorsal surface shiny, bearing distinct and transverse microstriae, also with coarse and sparse punctures. Head with 5−7 irregular punctures scattered around each eye and numerous smaller punctures on deflexed portion of temple and near posterior margin. Each side of head with characteristic punctures: one frontal puncture on frontal region, two anterolateral punctures near antennal insertion, three lateral punctures near dorsal margin of eye, with temporal puncture and occipital puncture near basal margin; disc surface bearing two additional paired punctures in middle area. Frontal furrows and anteocular furrows absent. Eye small-sized, distinctly protruding laterad, longitudinal diameter shorter than half the length of tempora (eye: tempora = 0.40). Epistoma not flattened, abruptly oblique, anterior margin slightly emarginate medially. Distance between antennal insertions (0.17 mm) distinctly longer than distance from antenna to eye (0.09 mm). Ventral surface with scattered punctures, interspaces between them as large as about 4 puncture diameters. Gular sutures deep, confluent at basal 1/3, then extended to base.

Antennae (Fig 4-1B). Scape rod-shaped, slightly thickened apically, distinctly shorter than two subsequent antennomeres combined; antennomere 2 distinctly elongate; antennomere 3 distinctly longer than 2; length of antennomere 4 about thrice of width, antennomere 4 to 10 gradually shortened, antennomere 4 observably longer than 10; antennomere 11 distinctly longer than 10.

Mouthparts (Fig 4-1A). Labrum oval-shaped, lateral margin rounded, widest at basal 1/2; width of anterior margin about 1/2 the width at the widest point. Mandibles (Figs 4-1D) falciform, left one with three small teeth, whereas right one with two.

Neck (Fig 4-1A). Cylindrical, shiny, only bearing shallow microsculpture, width 0.17 mm, shorter than 1/3 of head width. Dorsal surface with distinct groove; ventral surface with gular sutures forming obvious triangular region, with deep transverse median furrow.

Prothorax (Fig 4-1A). Pronotum elongate (PL to PW ratio 1.28), distinctly longer and wider than head. Anterior region near anterior angles slightly deflexed, lateral margins widened posteriad to basal 1/4 (widest at 1/4), then convergent backwards, anterior and posterior angles broadly rounded. Dorsal surface glossy, extensively with micropunctures, but without any microsculpture. Each side of longitudinal midline with one row of punctures composed of 3 large punctures and 2 additional punctures outside of puncture row, 13–15 punctures scattered near each margin (including anterior, lateral and posterior margins). Prosternum bearing an observable transverse ridge between basisternum and furcasternum, angularly backwards.

Pterothorax (Fig 4-1A). Mesoscutellum triangular, surface shiny, bearing distinct microstriae, but without any punctures. Transverse ridge on mesoventrite wave shaped; paired oblique furrows short but deep; carina limiting mesocoxal cavity slightly arcuate. Discrimen region on metaventrite normally elevated.

Elytra (Fig 4-1A). Elytra slightly transverse (EL to EW ratio 0.96), longer and wider than pronotum. Humeri well developed, lateral margins divergent posteriorly, posterior margin not rounded, but obliquely truncate. Dorsal surface shiny, flattened, without microsculpture; each elytron with row of 5 punctures along suture, row of 6 punctures on disc, also with 4−5 rows of punctures on deflexed portion.

Legs (Fig 4-1C). First four segments of protarsi heart-shaped, moderately dilated, and those of meso- and metatarsi slender. Last segment of protarsi slightly longer than 2−4 together, that of meso-, meta- slightly shorter than the length of each 2−3.

Abdomen. Broadest at segment V. Tergites III–VII covered with dense and obvious transverse microstriae; each tergite with dense brown pubescence, also with row of darker and coarser setae at posterior margin of III–VI. Tergites III–VII with a basal impression near anterior margin, respectively, each one only possessing one basal transverse carina; all abdominal tergites with surface shiny, bearing polygonal microsculpture, with dense punctures. Posterior margin of tergite VII with distinct palisade fringe. All abdominal sternites shiny, with microstriae and punctures as those on tergites.

Male (Figs 4-1E–J; 4-2A–E). Head with small oval elevation between eyes. Posterior margin of sternite VIII nearly straight, sharp on posterior angles (Figs 4-1E, L; 4-2B). Posterior margin of tergite VIII arcuate (Figs 4-1F; 4-2C). Tergite IX (Figs 4-1H; 4-2D) symmetrical, connected mediobasally, narrowed apically. Sternite IX (Figs 4- 1G; 4-2E) asymmetrical, widest near 1/2; basal margin straight, apical margin normally emarginate; width of apical margin about twice the length of basal margin. Tergite X (Figs 4-1H; 4-2D) symmetrical, triangular. Aedeagus (Figs 4-1I−J; 4-2A) symmetrical, large-sized, ca. 0.75 mm long, mostly membranous. Parameres symmetrical, thin and short, reaching to about half of median lobe. Internal structures sclerotized, paired elongated sclerites in middle, in brown color. Sperm pump coiled, thinned toward apex.

Female (Figs 4-2F−I). Head without elevation between eyes. Sternite VIII (Fig 4-2F) with posterior margin rounded. Tergite IX bearing numerous setae, elongate and sharply pointed apically. Sternite IX (Fig 4-2H) symmetrical, with deep concave margin in middle. Tergite X broad, basal margin curved. Sternite X (Fig 4-2G) slender and rhomboidal, with numerous setae in lower half. Tube of spermatheca long and sclerotized, with several bends (Fig 4-2I).

Distribution. Thailand.

Diagnosis. This new species is very large in size and has long antennae, which easily separate it from congeneric species. In this species, the posterior margin of male sternite VIII is nearly straight, and the aedeagus is elongate and mostly membranous, which can also be used to distinguish it from other species.

Etymology. The species epithet is derived from Latin word robustus , to indicate the large-sized body.