Diochus elongatus Huang, Janák & Zhou, 2024

Huang, Tian, Janák, Jiří & Zhou, Hong-Zhang, 2024, Taxonomy of the genus Diochus Erichson (Coleoptera: Staphylinidae, Staphylininae, Diochini) of Papua New Guinea, Vanuatu and Solomon Islands, Zootaxa 5519 (1), pp. 103-118 : 105-109

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

( Fig 1A ; Figs 2-1; 2-2 )

Type locality. Papua New Guinea: Kainantu : Onerunka.

Type material. Holotype: male, PAPUA NEW GUINEA: Kainantu : Onerunka, 28. VIII. 1979 ( MHNG) . Paratypes: PAPUA NEW GUINEA: Kainantu: 1 female, Onerunka , 25. VIII. 1979 ( MHNG); Madang : 1 male, “ NEW GUINEA: Madang. Dist., Budernu c. 4000 ft. 15−24.X.1964 ”, “Stn. No 64”, “M.E: Bacchus. B.M.1965-120” ( JJRC) ; 1 male, “ NEW GUINEA: Madang. Dist., Budernu c. 4000 ft. 15-24.X.1964 ”, “Stn. No 66”, “M.E: Bacchus. B.M.1965-120” ( NHMUK) ; 1 male: “ NEW GUINEA: Madang. Dist., Mt.Abilala c. 9000 ft. 19-22.XI.1964.”, “Stn. No 102.”, “M.E: Bacchus. B.M.1965-120” ( NHMUK) .

Measurements. BL = 5.82 mm, FL = 3.08 mm, HL = 0.85 mm, HW = 0.61 mm, EyL = 0.18 mm, TL = 0.54 mm, ANL = 1.92 mm, ANT1 = 0.25 mm, ANT2 = 0.16 mm, ANT3 = 0.22 mm, ANT4 = 0.17 mm, ANT 11 = 0.19 mm, PL = 1.09 mm, PW = 0.84 mm, EL = 1.02 mm, EW = 1.06 mm, SL = 0.77 mm.

Description. Body ( Fig 1A ) long, narrowed anteriorly and posteriorly, large-sized. Body blackish brown, abdominal intersegmental membrane lighter. Legs dark brown, tarsi distinctly lighter. Antennae dark brown, apex of each antennomere lighter. Maxillary and labial palpi brown.

Head ( Fig 2-1A ). Oblong in shape, 1.39 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 tempus and near posterior margin. Each side of cranium 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 about 1/3 the length of tempora (eye: tempora = 0.33). Epistoma not flattened, abruptly oblique, anterior margin slightly emarginate medially. Distance between antennal insertions (0.19 mm) distinctly longer than distance from antenna to eye (0.12 mm). Ventral surface with scattered punctures, interspaces between them about 4 puncture diameters. Gular sutures deep, confluent near the base.

Antennae ( Fig 2-1B ). Scape rod-shaped, slightly thickened apically, distinctly shorter than two subsequent antennomeres combined; antennomere 2 slightly elongate, antennomere 3 distinctly longer than 2; 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 2-1A ). Labrum nearly hexagonal, lateral margin straight, widest at basal 1/3 to 1/2; width of anterior margin is about 1/3 the width at the widest point. Mandibles ( Fig 2-1D ) falciform, left one with three small teeth on inner margin, whereas right one with two.

Neck ( Fig 2-1A ). Cylindrical, shiny, only bearing shallow microsculpture, width 0.18 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 2-1A ). Pronotum blackish brown, elongate (PL to PW ratio 1.29), distinctly longer and wider than head. Anterior region near anterior angles 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 composing 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 ). Mesoscutellum triangular, surface shiny, bearing distinct microstriae, but without any punctures. Transverse ridge on mesoventrite wave shaped; the paired oblique furrows short but deep; the carina limiting mesocoxal cavity slightly arcuate. Discrimen region on metaventrite normally elevated.

Elytra ( Fig 2-1A ). Elytra blackish brown, slightly transverse (EL to EW ratio 0.96), distinctly 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 6 punctures along suture, row of 6 punctures in median, also with 4−5 rows of punctures on deflexed portion.

Legs ( Fig 2-1C ). 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- nearly equal to the length of each 2−3.

Abdomen ( Fig 1A ). 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 reticulum, 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 ). Head with a small oval elevation between eyes. Posterior margin of sternite VIII emarginated medially, nearly trapezoidal, each side shallowly concaved ( Figs 2-1E, L, M; 2-2B ). Posterior margin of tergite VIII arcuate ( Figs 2-1F; 2-2C ). Tergite IX ( Figs 2-1H; 2-2D ) symmetrical, connected mediobasally, narrowed apically. Sternite IX ( Figs 2-1G; 2-2E ) asymmetrical, widest near basal 1/2; basal margin straight, apical margin normally emarginated; width of apical margin distinctly shorter than of basal margin. Tergite X ( Figs 2-1H; 2-2D ) symmetrical, triangular. Aedeagus ( Figs 2-1I–K; 2-2A ) symmetrical, large-sized, ca. 0.90 mm long, normally sclerotized. Parameres symmetrical, thick and short, about 1/6 length of median lobe. Internal structures sclerotized, composed of five parts: a Y-shaped sclerite and paired rod-shaped sclerites on top, symmetrical, brown color; 3 pair of sclerites located on both sides: paired small round shaped sclerites and paired large irregular shaped sclerites in black color; paired rod-shaped sclerites in brown color; 3 sclerites in the middle: paired small irregular shaped sclerites in brown color, one tongue-shaped sclerite in brown color. Sperm pump coiled, thinned toward apex.

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

Distribution. Papua New Guinea.

Diagnosis. According to the large body size, long antennae and dark coloration, the species can be easily distinguished from other species.

Etymology. The species epithet is derived from the Latin word “ elongatus ”, to indicate the large and long body of the new species.

Figures

FIGURE 1. Habitus of four species from Papua New Guinea, Vanuatu and Solomon Islands in dorsal view:A. Diochus elongatus sp. nov.; B. D. chambrieri sp. nov.; C. D. papuanus Cameron, 1939, D. D. loebli sp. nov. (Scale bar: 0.5 mm).

FIGURE 2-2. Diochus elongatus sp. nov.: A. aedeagus, dorsal view; B. male sternite VIII; C. male tergite VIII; D. male tergites IX–X; E. male sternite IX; F. female sternite VIII; G. female sternite X; H. female sternite IX; I. spermatheca.(Scale bars: A = 0.05 mm, B–I = 0.1 mm).