Horaeomorphus samosirensis, ski, 2009

ski, P. Jałoszy, 2009, Four New Species Of Horaeomorphus Schaufuss From The Oriental Region (Coleoptera: Staphylinidae, Scydmaeninae), Raffles Bulletin of Zoology 57 (2), pp. 297-303 : 302

Horaeomorphus samosirensis , new species

( Figs.1d , 3c, d , 4b )

Material examined. – Holotype. Male , three labels: “NORD- SUMATRA: \ Umg. Partungkoan \ Samosir, 28.8.91” [white, printed], “ 1600m, Urwald, \ unt. Pinus-Rinde \ ERBER ” [white, printed, middle line handwritten in black], “ HORAEOMORPHUS \ samosirensis m. \ HOLOTYPUS \ det. P. JAŁOSZY SKI, ‘08” [red, printed] ( SMNS).

Diagnosis. – This stout and moderately large species is unique in having a hook-like ventral projection on metafemora and strongly bent metatibiae of males.

Male. – Body ( Fig. 1d ) moderately large (length 2.20 mm), with pronotum and elytra very broad and slightly flattened, dark brown, vestiture slightly lighter than cuticle.

Head broadest at moderately large, strongly convex eyes, length 0.38 mm, width 0.48 mm; tempora much longer than eye in dorsal view, very weakly arcuate up to posterior 4/5, where they rapidly bend toward occipital constriction; vertex weakly convex, with pair of small and very shallow pits located near posterior margins of supraantennal tubercles; posterior part of frons flattened, anterior part convex; supraantennal tubercles very distinct, strongly raised, well delimited from frons but indistinctly delimited from vertex. Punctures on vertex and frons very fine, shallow and sparse, unevenly distributed, separated by spaces 2-4x as long as puncture diameters; setae moderately long, sparse, suberect to erect. Antennae moderately slender, distinctly shorter than half length of body, length 0.88 mm; relative lengths of antennomeres (shortest antennomere VIII as 1): 1.4; 1.2; 1.24; 1.2; 1.16; 1.04; 1.04; 1; 1.2; 1.6; 2.

Pronotum very broad, nearly circular, broadest between middle and anterior third, length 0.75 mm, width at base 0.38 mm, maximum width 0.73 mm; anterior and lateral margins rounded together; posterior collar extremely short, indistinctly separated from disc by very shallow constriction and dorsal row of three very small and shallow pits located in narrow and deep groove, median pit prolonged anteriorly by short longitudinal groove; hind angles of pronotum blunt, obtuse; posterior margin weakly arcuate. Punctures on disc small and shallow but distinct, unevenly distributed, those in middle are separated by spaces 1.5–4× as long as puncture diameters; punctures become gradually smaller and shallower toward margins of disc; vestiture sparse, moderately long, suberect.

Elytra very broad, oval, as convex as pronotum, broadest between middle and anterior third, length 1.08 mm, width 0.85 mm, EI 1.26. Base of elytra arcuate, so that humeri are projected anteriorly; humeral calli weakly marked, delimited from adsutural region by short, broad and relatively deep basal impressions; basal foveae indiscernible; each elytron is slightly impressed near suture in anterior third; apices of elytra separately rounded. Punctures in anterior 2/3 of elytra much larger, deeper and denser than those on median part of pronotum, those on adsutural impression are separated by spaces distinctly shorter than puncture diameters; punctures are gradually smaller and shallower toward apices and lateral margins of elytra. Vestiture slightly longer and more erect than that on pronotum. Metathoracic wings long, functional.

Hind legs strongly modified, as in Fig. 4b .

Aedeagus ( Figs. 3c, d ) 0.28 mm in length; median lobe relatively slender, with short, subtriangular apical part; internal sac simple and lightly sclerotized; parameres slender, distinctly exceeding apex of median lobe, each with three short apical and subapical setae.

Female. – Unknown.

Etymology. – Locotypical, after the type locality, Samosir Is. on Sumatra.

Distribution. – Indonesia (Sumatra), North Sumatra Prov.: Samosir Is.

Remarks. – The only species of the genus with hook-like projections on the metafemora known so far was H. heissi Franz, 1985 from W Malaysia (Pahang) and Indonesia (Sumatra). The latter species is distinctly different in the general body form, it is smaller, more slender and distinctly flatter than H. samosirensis ; it also has only slightly bent metafemora, whereas those in H. samosirensis are strongly bent. This new species is the first Horaeomorphus reported to occur in an island located on a lake.

Figures

Fig. 1. Dorsal habitus of holotype males: a, Horaeomorphus imitator, new species; b, Horaeomorphus minor, new species; c, Horaeomorphus fakfakensis, new species; d, Horaeomorphus samosirensis, new species (d). Scale bar = 0.5 mm.

Fig. 3. Aedeagus in ventral (a, c) and lateral (b, d) views: a, b, Horaeomorphus fakfakensis, new species, c, d, Horaeomorphus samosirensis, new species. Scale bar = 0.2 mm.

Fig. 4. Hind trochanter and femur (a), and hind trochanter, femur and tibia (b). Horaeomorphus imitator new species (a), Horaeomorphus samosirensis new species (b). Scale bar = 0.2 mm.