Siamites thantonus, Jałoszyński, 2020

Jałoszyński, Paweł, 2020, Four new species of the Oriental genus Siamites Franz (Coleoptera, Staphylinidae Scydmaeninae), Zootaxa 4751 (1), pp. 187-195 : 189-191

Siamites thantonus sp. n. ( Figs 7–12 )

Type material. Holotype: THAILAND (Yala Prov.): ♂, two labels: “ Thailand, 1.2.1991 / Banglang Nat. Park / Than To Waterfall, / Than To Dist. 150m / P. Schwendinger ” [white, printed]; “ SIAMITES / thantonus m. / det. P. Jałoszyński, 2020 / HOLOTYPUS ” [red, printed] ( MHNG).

Diagnosis. Male macrophthalmous; head with six vertexal tufts of bristles fused to form continuous transverse row; aedeagus with large apical plate with concave apical margin, base of median lobe rapidly narrowing toward basal foramen.

Description. Body of male ( Fig. 7 ) moderately convex and moderately slender, uniformly light brown, covered with yellowish vestiture. BL 1.00 mm.

Head ( Fig. 8 ) broadest at large, strongly convex and coarsely faceted eyes, HL 0.15 mm, HW 0.21 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. 8 ) composed of six tufts of dense and relatively short bristles, all connected to form continuous transverse row on 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 tetramerous 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 shortly behind middle; PL 0.25 mm, PW 0.25 mm. All margins weakly and evenly rounded; lateral carinae indistinct, visible only 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 0.60 mm, EW 0.45 mm, EI 1.33; humeral calli weakly marked, each with indistinct, 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 9–12 ) stout; AeL 0.08 mm; median lobe subtrapezoidal, broadest near middle but strongly narrowing only toward base, apical margin broadly concave at middle; endophallic structures darkly sclerotized; parameres short and moderately broad, each with two long apical setae.

Female. Unknown.

Distribution. Southern Thailand ( Fig. 25 ).

Etymology. After Than To Waterfall and a district of the same name.

Remarks. The aedeagus of S. thantonus is most similar in general form to that of S. loebli (illustrated by Jałoszyński (2005)). However, the basal region of median lobe in ventral view is broadly and evenly rounded in S. loebli (vs. rapidly narrowing in S. thantonus ), and the shape of the darkly sclerotized internal structure is clearly different in these two Thai species.

Figures

FIGURE 25. Distribution of nominal Siamites species.

FIGURES 7–12. Siamites thantonus sp. n., dorsal habitus (7); head in anterodorsal view (8); aedeagus in ventral (9, 11) and lateral (10, 12) views.