Hlavaciellus diversipilosus Jałoszyński 2021, sp. n.
Creators: name: Jałoszyński, Paweł
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Staphylinidae
Hlavaciellus
Hlavaciellus diversipilosus

description: Hlavaciellus diversipilosus sp. n.
(Figs 13–16, 25)
Type material. Holotype: MALAYSIA (Pahang): ♂, two labels: “ E.Malaysia: Sarawak / confl. Sun Oyan and / Mujong riv., E.Kapit / 50m, 18.V.1994, # 5a / Löbl & Burckhardt” [white, printed], “ HLAVACIELLUS / diversipilosus m. / P. Jałoszyński, 2021 / HOLOTYPUS” [red, printed] (MHNG). Paratype: 1 ♂, same data as for holotype (cPJ).
Diagnosis. Body very small, reaching only 1.6 mm in length; head in males with pair of transverse, shallow and indistinct postocular impressions and several setae on median frontal region divergent laterad along anterior margins of impressions; each of antennomeres 1–10 about as long as broad; aedeagus in ventral view moderately stout, 3.2 times as long as broad and distinctly narrowing both toward apex and base; parameres with thin subapical setae.
Description. Body of male (Fig. 13) stout, strongly convex, uniformly dark brown; setae distinctly lighter than cuticle; BL 1.58–1.60 mm.
Head (Fig. 14) broadest at large, strongly convex and coarsely faceted eyes, HL 0.25 mm, HW 0.43 mm; frons and vertex weakly convex at middle, vertex behind each eye with shallow transverse impression. Punctures on frons and vertex fine and inconspicuous; setae long, moderately dense and suberect, a few setae inserted on median frontal region are strongly divergent laterad along anterior margins of postocular impressions. Antennae slender, AnL 1.05 mm, BL/AnL 1.50–1.52; antennomeres 1–10 each about as long as broad, 11 distinctly shorter than 9–10 combined, twice as long as broad.
Pronotum subrectangular, broadest at base but indistinctly narrowing anterad; PL 0.45–0.48 mm, PW 0.73 mm, PI 0.62–0.66; anterior margin weakly rounded; sides with finely crenulate lateral carinae, in posterior 2/3 straight; posterior corners sharp-angled and with acute tips; posterior margin shallowly bisinuate; pronotal disc strongly convex, with area at each posterior corner distinctly impressed; antebasal pits slightly closer to posterior than to lateral margins. Punctures on pronotum fine and inconspicuous; setae long, dense, suberect.
Elytra together oval, broadest distinctly in front of middle; EL 0.88 mm, EW 0.80 mm, EI 1.09; subhumeral lines sharply marked, each developed as step-wise border between elevated humeral region and median area, slightly exceeding 0.3 EL; sides of elytra strongly rounded; elytral apices separately rounded. Punctures and setae similar to those on pronotum.
Legs long and slender, unmodified.
Aedeagus (Figs 15–16) elongate but not very slender; AeL 0.33–0.35 mm; median lobe in ventral view 3.2 times as long as broad, broadest near sub-basal third and with broadly rounded sides; endophallic structures distinct, in ventral view appearing as two elongate elements, also in lateral view two separate tubular structures can be seen, proximal one bent at sharp angle near base of median lobe, distal one with cup-like broadening situated near middle of median lobe; parameres with thin subapical setae.
Female. Unknown.
Distribution. Borneo (Fig. 25).
Etymology. The adjective diversipilosus refers to the setal pattern on the head, with some setae directed laterad along postocular impressions.
Remarks. Among SE Asian species, Hlavaciellus diversipilosus has the smallest adults, with the body length not exceeding 1.6 mm. The small size, body shape, transverse postocular impressions on the head, and the endophallic structures of the aedeagus in lateral view with a cup-like broadened distal portion of the distal sclerite is a unique combination of characters that allows for unambiguous identification of this species.
description: Published as part of Jałoszyński, Paweł, 2021, Six new species of the Oriental genus Hlavaciellus Jałoszyński (Coleoptera Staphylinidae, Scydmaeninae), pp. 1-15 in Zootaxa 4966 (1) on pages 7-8, DOI: 10.11646/zootaxa.4966.1.1, http://zenodo.org/record/4729328