Diochus acehensis Huang, Janák & Zhou, 2025

1. Diochus acehensis Huang, Janák & Zhou , sp. nov.

( Figs 1L View FIGURE 1 ; 2-1; 2-2 View FIGURE 2-2 )

Type locality. Indonesia: Sumatra: Aceh.

Type material. Holotype: male, INDONESIA: Sumatra: Aceh #25a, Mt. Leuser NP , 300–500 m, Ketambe , 23–30. XI. 1989, Löbl, Agosti, Burckhardt ( MHNG) . Paratypes: INDONESIA: Sumatra: 5 males, Aceh #26a, Mt. Leuser NP, Ketambe , 800 m, 28. XI. 1989, Löbl, Agosti, Burckhardt ( MHNG, JJRC) ; 2 males, W Sum., Padangpanjan , 600 m, 17. XI. 1989, Agosti, Löbl, Burckhardt ( MHNG) ; 1 female, W Sum. #18, Anai V. Nat. Res., 10 km W Padangpanjan , 250 m, 17. XI. 1989, Löbl, Agosti, Burckhardt ( MHNG) ; 1 female, W Sum. #19, Anai V. Nat. Res., 10 km W Padangpanjan , 200 m, 17. XI. 1989, Löbl, Agosti, Burckhardt ( MHNG) ; 2 females, W Sum. #21, Palopo Nat. Res. N, Bukittinggi , 900 m, 18–20. XI. 1989, Löbl, Agosti, Burckhardt ( MHNG, JJRC) .

Measurements. BL = 3.93 mm, FL = 1.73 mm, HL = 0.50 mm, HW = 0.40 mm, EyL = 0.10 mm, TL = 0.29 mm, ANL = 1.00 mm, ANT1 = 0.15 mm, ANT2 = 0.09 mm, ANT3 = 0.09 mm, ANT4 = 0.07 mm, ANT 11 = 0.11 mm, PL = 0.65 mm, PW = 0.52 mm, EL = 0.61 mm, EW = 0.71 mm, SL = 0.44 mm.

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

Head ( Fig 2-1A View FIGURE 2-2 ). Trapezoid in shape, 1.27 times as long as wide. Tempora distinctly widened backwards, 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, not distinctly protruding laterad, longitudinal diameter distinctly shorter than half the length of tempora (eye: tempora = 0.35). Epistoma not flattened, abruptly oblique, anterior margin slightly emarginate medially. Distance between antennal insertions (0.11 mm) distinctly longer than distance from antenna to eye (0.09 mm). Ventral surface with sparsely scattered punctures, interspaces between them as large as about 4 puncture diameters. Gular sutures deep, approaching to each other before base, but not confluent.

Antennae ( Fig 2-1B View FIGURE 2-2 ). Scape rod-shaped, slightly thickened apically, slightly shorter than two subsequent antennomeres combined; antennomere 2 not distinctly elongate; antennomere 3 about the length of 2; length of antennomere 4 about 1.3 times of width, antennomere 4 to 10 nearly equal in length, but gradually widened; antennomere 11 distinctly longer than 10.

Mouthparts ( Fig 2-1A View FIGURE 2-2 ). Labrum nearly hexagonal, lateral margins rounded, widest at basal 1/2; anterior margin about half of width at the widest point. Mandibles ( Fig 2-1D View FIGURE 2-2 ) falciform, left one with three small teeth on inner margin, whereas right one with two.

Neck ( Fig 2-1A View FIGURE 2-2 ). Cylindrical, shiny, only bearing shallow microsculpture, width 0.13 mm, slightly 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 2-1A View FIGURE 2-2 ). Pronotum elongate (PL to PW ratio 1.26), 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 2-1A View FIGURE 2-2 ). Mesoscutellum triangular and small, 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 2-1A View FIGURE 2-2 ). Elytra distinctly transverse (EL to EW ratio 0.86), shorter but 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 5 punctures on disc, also with 4−5 rows of punctures on deflexed portion.

Legs ( Fig 2-1C View FIGURE 2-2 ). First four segments of protarsi heart-shaped, moderately dilated, and those of meso- and metatarsi slender. Last segment of protarsi about the length of 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 2-1E–J; 2-2A–E View FIGURE 2-2 ). Head without elevation between eyes. Posterior margin of sternite VIII slightly emarginate medially, basal transverse carina wave-shaped, emarginate medially ( Figs 2-1E; 2-2B View FIGURE 2-2 ). Posterior margin of tergite VIII arcuate ( Figs 2-1F; 2-2C View FIGURE 2-2 ). Tergite IX ( Figs 2-1H; 2-2D View FIGURE 2-2 ) symmetrical, connected mediobasally, narrowed apically. Sternite IX ( Figs 2-1G; 2-2E View FIGURE 2-2 ) symmetrical, widest at basal 1/3 to 1/2; basal margin deeply emarginate, apical margin slightly emarginate; width of apical margin slightly wider than basal margin. Tergite X ( Figs 2-1H; 2-2D View FIGURE 2-2 ) symmetrical, triangular. Aedeagus ( Figs 2-1 View FIGURE 2-2 I−J; 2-2A) asymmetrical, small-sized, ca. 0.38 mm long, normally sclerotized. Parameres symmetrical, reaching above top of median lobe. Internal structures sclerotized, with a heart-shaped sclerite and two elongated sclerites in middle. Sperm pump coiled, thinned toward apex.

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

Distribution. Indonesia (Sumatra).

Diagnosis. This new species is small in size, with light coloration and short antennae, and males have a head without an elevation between eyes. Males can be easily separated from congeneric species but are similar to D. antennatus , which also has a similar aedeagus. However, this species is distinctly smaller in size, and the aedeagus lacks a T-shaped sclerite distally.

Etymology. The species epithet is derived from the name of type locality, Aceh ( Indonesia, Sumatra).