Diochus borneensis Cameron 1933
Creators: name: Huang, Tian
name: Janák, Jiří
name: Zhou, Hong-Zhang
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Staphylinidae
Diochus
Diochus borneensis

description: 10. Diochus borneensis Cameron, 1933
(Fig 1C; Fig 10)
Diochus borneensis Cameron, 1933: 344 (Type locality: British North Borneo: Kenokok); Hammond, 1984: 205 (checklist).
Type material examined. MALAYSIA: SABAH: Holotype: female, “Type” (printed black, rounded label with red borders), “ B.N. BORNEO. Mt. Kinabalu, Kenokok,” (printed, light reddish label), “ 3.300 ft. 23 Apr. 1929 ” (printed and handwrited, light reddish label), “ D. borneensis Cam. TYPE” (black and red, Cameronʼs handwriting), “ M. Cameron. Bequest. B.M.1955-147” (NHMUK).
Additional material examined. MALAYSIA: SABAH: 1 female, Poring Hot Springs, 500 m, 8. V. 1987, Burckhardt-Löbl (MHNG).
Note. We examined the unique female type from Cameronʼs collection (NHMUK), which we considered as a holotype as only “one example” is mentioned in the description (Cameron 1933: 344).
Measurements. BL = 5.60 mm, FL = 2.98 mm, HL = 0.87 mm, HW = 0.65 mm, EyL = 0.22 mm, TL = 0.53 mm, ANL = 1.75 mm, ANT1 = 0.29 mm, ANT2 = 0.14 mm, ANT3 = 0.19 mm, ANT4 = 0.14 mm, ANT 11 = 0.17 mm, PL = 1.11 mm, PW = 0.88 mm, EL = 1.07 mm, EW = 1.18 mm, SL = 0.79 mm.
Redescription. Body long, narrowed anteriorly and posteriorly, large-sized. Body black or dark brown, posterior parts of abdominal segments lighter, reddish brown, intersegmental membrane reddish yellow. Legs yellowish brown with apical three quarters of tibiae at least partly blackish. Antennae brown with first 1–3 antennomeres partly and apex of each antennomere lighter, light reddish brown. Maxillary and labial palpi yellowish brown.
Head (Fig 10A, E). Very oblong in shape, 1.35 times as long as wide. Tempora regularly rounded, noticeably apically narrowed in basal third of head, posterior angles indistinct. Dorsal surface shiny, bearing very shallow and less distinct transverse microstriae, also with coarse and sparse punctures and scattered micropunctures. Head with about 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 medium-sized, only slightly protruding laterad, longitudinal diameter shorter than half the length of tempora (eye: tempora = 0.42). Epistoma not flattened, abruptly oblique, anterior margin slightly emarginate medially. Distance between antennal insertions (0.20 mm) distinctly longer than distance from antenna to eye (0.08 mm).
Antennae (Fig 10B, F). Scape rod-shaped, slightly thickened apically, slightly shorter than two subsequent antennomeres combined; antennomere 2 slightly elongate, antennomere 3 distinctly longer than 2; length of antennomere 4 about twice of width, antennomere 4 to 10 gradually shortened, antennomere 4 observably longer than 10; antennomere 11 distinctly longer than 10.
Mouthparts (Fig 10A, E). Labrum nearly hexagonal, lateral margin straight, widest at basal 1/3 to 1/2; width of anterior margin is about 3/5 the width at the widest point.
Neck (Fig 10A, E). Cylindrical, shiny, microsculpture indistinct, width 0.16 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 10A, E). Pronotum distinctly elongate (PL to PW ratio 1.26), 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, with scattered micropunctures, but without any microsculpture. Each side of longitudinal midline with one row of punctures composed of 3 large punctures (atypically with one additional puncture in left row in holotype) and 2 additional punctures outside of puncture row, 13–15 punctures scattered near each margin (including anterior, lateral and posterior margins).
Pterothorax (Fig 10A, E). Mesoscutellum triangular, surface shiny, bearing slightly transverse very fine mesh, but without any punctures.
Elytra (Fig 10A, E). Elytra slightly transverse (EL to EW ratio 0.91), about as long as 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 5–7 punctures along suture, two rows of 4–6 punctures in median, also with 3−4 rows of punctures on deflexed portion.
Legs (Fig 10G). First four segments of protarsi heart-shaped, moderately dilated, and those of meso- and metatarsi slender. Last segment of protarsi shorter than 2−4 together, that of metatibia only slightly longer than length of first segment.
Abdomen. Broadest at segment IV. 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 fine transverse or polygonal mesh, with dense punctures. Posterior margin of tergite VII with distinct palisade fringe.
Male. Unknown.
Female (Fig 10C, H−K). Head without elevation between eyes. Tube of spermatheca with three bends. Apical circle of the tube large in size but apical lobe small.
Diagnosis. The species can be easily distinguished by the large body, narrowed pronotum and noticeably apically narrowed and partly black tibiae.
Note. The female from Poring Hot Springs is externally very similar to the holotype, but differs by having the basal part of the tube of spermatheca more symmetrical and with less pronounced bends.
Distribution. Kalimantan (Borneo).
description: Published as part of Huang, Tian, Janák, Jiří & Zhou, Hong-Zhang, 2025, Revision of the genus Diochus Erichson (Coleoptera: Staphylinidae, Staphylininae, Diochini) from Indonesia, Malaysia and Singapore, pp. 441-479 in Zootaxa 5632 (3) on pages 471-473, DOI: 10.11646/zootaxa.5632.3.2, http://zenodo.org/record/15372327