Siamites sabahensis Jałoszyński 2020, sp. n.

Siamites sabahensis sp. n.

(Figs 19–24)

Type material. Holotype: E MALAYSIA (Sabah): ♂, two labels: “ SABAH: Poring Hot / Spring, 500 m / 7.V.1987 / Burckhardt - Löbl” [white, printed]; “ SIAMITES / sabahensis m. / det. P. Jałoszyński, 2020 / HOLOTYPUS ” [red, printed] (MHNG).

Diagnosis. Male macrophthalmous; head with four separate tufts of bristles evenly distributed along posterior margin of vertex; aedeagus with large distal plate strongly constricted at base and with a pair of apical hooks.

Description. Body of male (Fig. 19) moderately convex and moderately slender, uniformly light brown, covered with yellowish vestiture. BL 0.93 mm.

Head (Fig. 20) broadest at large, strongly convex and coarsely faceted eyes, HL 0.13 mm, HW 0.18 mm; tem- pora in dorsal view slightly shorter than eyes; vertex with indistinct posteromedian impression, strongly transverse; frons confluent with vertex, with shallow median impression between weakly elevated supraantennal tubercles. Punctures on vertex obscured by bristles, those on frons fine, inconspicuous. Vestiture of head dorsum (Fig. 20) composed of four separate tufts of dense and relatively short bristles evenly distributed along posterior margin of vertex, outer tufts slightly larger than inner pair; long and thick sparse bristles directed posterodorsad and situated slightly in front of posterior tufts; and sparse, suberect setae on frons. Antennae short, with moderately strongly broadened, indistinctly delimited tetramerous club, AnL 0.38 mm; scape and pedicel strongly elongate; antennomeres III–VII each about as long as broad, VIII–X each strongly transverse, XI distinctly shorter than IX–X com- bined, narrower than X, almost as long as broad.

Pronotum subconical with broad anterior margin, broadest near posterior third; PL 0.25 mm, PW 0.25 mm. All margins weakly and evenly rounded; lateral carinae barely discernible, blunt, marked in posterior third of pronotum; base with transverse groove distinctly deepened at each end. Punctures on pronotum fine and sparse, unremarkable; setae sparse, suberect, moderately long.

Elytra slightly flattened, together oval, broadest distinctly in front of middle; EL 0.55 mm, EW 0.40 mm, EI 1.38; humeral calli weakly marked, each with indistinct and rounded humeral carina not exceeding 1/4 of elytral length; basal impressions shallow and short; apices of elytra rounded together. Punctures on elytra more distinct and denser than those on pronotum but superficial and inconspicuous; setae sparse, short, suberect.

Wings long and functional.

Aedeagus (Figs 21–24) elongate; AeL 0.13 mm; median lobe in ventral view cup-shaped with large apical plate projecting from ostium, plate constricted in basal region; endophallus with indistinctly delimited, moderately darkly sclerotized structures (very dark area visible near middle of median lobe in Figs 21 and 22 is an artifact); parameres short and broad, each with three long apical setae.

Female. Unknown.

Distribution. East-northern Borneo (Fig. 25).

Etymology. After Sabah.

Remarks. The four tufts of bristles visible on the vertex in S. sabahensis seem to be a result of fusion of the lateralmost tufts from the original number of six. This character may be helpful to identify S. sabahensis, but examination of the uniquely shaped aedeagus is necessary to confirm determination.