Horaeomorphus minor, 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 : 298-300

Horaeomorphus minor , new species

( Figs. 1b , 2c,d )

Material examined. – Holotype. Male, two labels: “MINDANAO, 30km NW of \ MARAMAG, 13.-17. MAY \ BAGONGSILANG, 1700 m \ Bolm lgt., 1996” [yellow, printed], “ HORAEOMORPHUS \ minor m. \ HOLOTYPUS \ det. P. JAŁOSZY SKI, ‘08” [red, printed] ( SMNS) . Paratypes. 1 male, same data as for holotype ( SMNS) ; 1 male, “MINDANAO, 1-3. May \ MISAMIS OCC., 1700 m \ DON VICTORIANO \ Bolm lgt., 1996” [yellow, printed] ( SMNS); paratypes additionally provided with identification labels analogous to that on the holotype, but yellow and annotated “ PARATYPUS ” .

Diagnosis. – This is one of the smallest species of Horaeomorphus , remarkable by not reaching 2 mm in length; it differs from all congeners also in the following combination of characters: lateral margins of pronotum slightly, but distinctly raised in posterior part to form rounded lateral longitudinal carinae; base of pronotum without groove, with two large lateral pits and very small median pit; elytra broadest near anterior third and very strongly narrowing from broadest place toward apices; legs in males non-modified; aedeagus with strongly asymmetrical, massive internal sac.

Male. – Body ( Fig. 1b ) very small (length 1.78-1.93 mm, mean 1.87 mm), slender, flattened, moderately dark brown, vestiture slightly lighter than cuticle; setae on pronotum slightly darker than those on elytra.

Head broadest at moderately large, moderately convex eyes, length 0.25-0.28 mm (mean 0.27 mm), width 0.35-0.38 mm (mean 0.37 mm); tempora as long as eye in dorsal view, regularly, weakly rounded up to posterior 3/4, where they are strongly bent toward occipital constriction; vertex weakly convex, with pair of small but deep pits located near posterior margins of supraantennal tubercles; frons weakly convex; supraantennal tubercles very distinct, strongly raised, well delimited from frons but indistinctly delimited from vertex. Punctures on vertex very fine, barely noticeable under magnification 80×; median part of frons bears dense, moderately large, distinct punctures unevenly distributed and separated by spaces 1–3× puncture diameters; setae moderately long, sparse, suberect to erect. Antennae moderately slender, shorter than half length of body, length 1.75– 0.80 mm (mean 0.78 mm); relative lengths of antennomeres (shortest antennomere II as 1): 0.83; 1; 1.07; 0.93; 0.8; 0.77; 0.73; 0.70; 0.97; 0.83; 1.5.

Pronotum inversely subtrapezoidal, elongate, broadest at anterior third, length 0.50–0.53 mm (mean 0.52 mm), width at base 0.33 mm, maximum width 0.43–0.45 mm (mean 0.43 mm); anterior margin rounded; lateral margins rounded near broadest place, then nearly straight up to indistinct subbasal constriction separating short posterior collar; lateral margins in posterior third to half raised, forming low and rounded lateral carinae; hind angles blunt, obtuse; posterior margin weakly arcuate; base of pronotum with pair of large lateral pits and very small, indistinct median pit. Punctures very small, moderately sharply marked, but well visible under magnification 40×, unevenly distributed, those on median part of disc are separated by spaces 1–3× as long as puncture diameters; setation moderately dense and long, suberect.

Elytra strongly elongate, drop-shaped, about as convex as pronotum, broadest near anterior third and strongly narrowing toward apices, length 1.03–1.13 mm (mean 1.08 mm), width 0.60–0.65 mm (mean 0.63 mm), EI 1.69– 1.73. Base of elytra arcuate so that humeri are projected anteriorly, humeral calli weakly marked, delimited from adsutural region by short and shallow, very broad basal impressions; basal foveae indiscernible; apices of elytra separately rounded. Punctures in anterior 2/3 of elytra much more distinct than those on pronotum, large, deep and relatively sharply marked; in median part of each elytron 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 distinctly more suberect than that on pronotum. Metathoracic wings long, functional.

Legs non-modified.

Aedeagus ( Figs. 2c, d ) 0.45 mm in length; median lobe moderately slender, with subtrapezoidal apical part; internal sac strongly asymmetrical, darkly sclerotized and complicated; parameres slender, not exceeding apex of median lobe, each with 4–5 apical and subapical setae.

Female. – Unknown.

Etymology. – The name minor refers to the small body of this species.

Distribution. – Philippines: Provinces Bukidnon and Misamis Occidental: Mindanao Island.

Remarks. – This small, slender and flattened species can be easily distinguished from any other congeners by the asymmetrical and very large internal sac of the aedeagus. The only other species with asymmetrical internal sacs are H. deformatus Jałoszy ski, 2006 from W Malaysia (Kuala Terengganu), and H. pseudosabahensis Jałoszy ski, 2006 from Sabah and Sarawak. The latter species has distinctly different body form (much larger and strongly convex). Horaeomorphus deformatus is relatively similar to H. minor in general body shape, but it can be easily distinguished on the basis of strongly modified metatrochanters and metafemora in males.

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. 2. Aedeagus in ventral (a, c) and lateral (b, d) views: a, b, Horaeomorphus imitator, new species; c, d, Horaeomorphus minor, new species. Scale bar = 0.2 mm.