Siamites sumatrensis Jałoszyński 2020, sp. n.

Siamites sumatrensis sp. n.

(Figs 13–18)

Type material. Holotype: INDONESIA (Sumatra): ♂, two labels: “ SUMATRA: Aceh #27 / Mt. Leuser N.P. / Ketambe, 1000 m / 28-29.XI.1989, Löbl / Agosti, Burckhardt” [white, printed]; “ SIAMITES / sumatrensis m. / det. P. Jałoszyński, 2020 / HOLOTYPUS ” [red, printed] (MHNG). Paratypes: 1 ♂, 1 ♀, same data as for holotype, except for standard yellow “ PARATYPUS ” labels (cPJ, MHNG).

Diagnosis. Male macrophthalmous; head with six separate tufts of bristles evenly distributed along posterior margin of vertex; aedeagus with conspicuously long median tubular endophallic structure projecting through ostium far beyond apex of median lobe.

Description. Body of male (Fig. 13) moderately convex and moderately slender, uniformly dark brown, covered with light brown vestiture. BL 0.99–1.03 mm.

Head (Fig. 14) broadest at large, strongly convex and coarsely faceted eyes, HL 0.15 mm, HW 0.20 mm; tempora in dorsal view slightly shorter than eyes; vertex with distinct 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. 14) composed of six separate tufts of dense and relatively short bristles evenly distributed along posterior margin of vertex; long and thick sparse bristles directed posterodorsad and situated slightly in front of posterior tufts; and sparse, suberect setae on frons. Antennae short, with strongly broadened, indistinctly delimited pentamerous club, AnL 0.40 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 combined, narrower than X, almost as long as broad.

Pronotum subconical with broad anterior margin, broadest at base; PL 0.25–0.28 mm, PW 0.25 mm. All margins weakly and evenly rounded; lateral carinae barely discernible, blunt, marked in posterior third of pronotum; base with distinct transverse groove indistinctly 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 0.59–0.60 mm, EW 0.40–0.43 mm, EI 1.38–1.50; 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 15–18) elongate; AeL 0.10 mm; median lobe in ventral view narrower than in lateral view, broadest in submedian region; endophallus with conspicuously long median tubular structure extending from ostium far beyond apex of median lobe; parameres short and broad, each with two long apical setae.

Female. Externally differs from male in vestigial eyes, reduced to one ommatidium on each side, situated close to antennal insertion. BL 1.00 mm; HL 0.15 mm, HW 0.20 mm, AnL 0.38 mm; PL 0.28 mm, PW 0.28 mm; EL 0.58 mm, EW 0.45 mm, EI 1.28.

Distribution. Northern Sumatra (Fig. 25).

Etymology. After Sumatra.

Remarks. The aedeagus of S. sumatrensis is unique and conspicuously shaped. Externally, however, this spe- cies is too similar to all its congeners with separate vertexal tufts (i.e., most known species) to be identifiable without dissection.