Horaeomorphus bicornis

Zhou, De-Yao & Li, Li-Zhen, 2016, New data on Horaeomorphus Schaufuss (Coleoptera: Staphylinidae: Scydmaeninae) from the Oriental region, with description of a bizarre new species from Yunnan, Southeast China, Zootaxa 4161 (2), pp. 271-281 : 272-276

Horaeomorphus bicornis D.-Y. Zhou & L.-Z. Li, new species

Figs 1 , 3–12 , 21

Type material (2 ƋƋ). Holotype: CHINA: Ƌ, labeled ‘ China: Yunnan, Yinjiang Hsien (盈江县), Tongbiguan Country (铜壁关乡) to Nabang Town (那邦镇), 24°37'47.57''N, 97°34'59.01''E, rotten wood, sifted, 1000m, 17.ii.2016, Jian-Yue Qiu & Hao Xu leg.’ . Paratype: CHINA: Ƌ, same label data as holotype .

Diagnosis. The labral projection gradually broadening anteriorly together with the projection on the clypeus allow for an unambiguous identification of the males of H. bicornis . The mentum with a pair of large lateral lobes; each metatibiae strongly bent at anterior third with the posterior 2/3 broadened and flattened; the coarsely punctate elytra each with a longitudinal, glossy, sparsely and finely punctured area located along the elytral suture; and the aedeagus with setiferous, emarginate apex of ventral wall are also unique among all congeners.

Description. Male ( Fig. 1 ). BL 1.76–1.87 mm; flattened, reddish brown, legs and palpi slightly lighter, vestiture of setae yellowish.

Head ( Figs 3–5 ) broadest at moderately large and moderately strongly convex eyes, HL 0.27–0.29 mm, HW 0.39–0.40 mm; tempora rounded and about as long as eye in dorsal view; vertex strongly transverse and weakly convex, with pair of shallow but distinct pits located near posterior margins of supraantennal tubercles; frons strongly convex, median region of clypeus strongly projecting ( Figs 3, 5 ); supra-antennal tubercles strongly raised, well delimited from frons but confluent with vertex. Punctures on vertex and frons fine and inconspicuous; setae moderately long, sparse, suberect to erect. Antennae ( Fig. 12 ) slender, shorter than half length of body, AnL 0.75– 0.81 mm; relative lengths of antennomeres: 2.0: 1.6: 1.9: 1.8: 1.6: 1.6: 1.4: 1.4:1.8: 1.8: 2.8.

Labrum transverse, anterior margin rounded, posterior margin strongly projecting at middle, forming a slightly reflexed, flattened horn (see in Fig. 5 ), which in dorsal view ( Fig. 3 ) is gradually broadening apically and forming a transverse, rounded anterior margin. Left mandible with two subapical teeth, right mandible with only one subapical tooth (in dorsal view, Fig. 3 ). Mentum with each lateral margin strongly bent ventrally, in lateral view each forming a large lateral lobe with rounded margin ( Fig. 5 ).

Pronotum subtrapezoidal, elongate, broadest near anterior third, PL 0.50–0.54 mm, PWb 0.35–0.37 mm, PWm 0.49–0.51 mm; hind angles obtuse and blunt; posterior margin rounded; posterior collar delimited from disc by broad, but shallow transverse groove, which is slightly convex posteriorly and connects two lateral pits, median pit large and deep, located anteriorly to the antebasal groove, which is anteriorly connected to a short and narrow longitudinal groove. Punctures on disc much coarser and denser than those on frons and vertex; vestiture composed of sparse, moderately long and suberect setae.

Elytra strongly elongate, oval, slightly more convex than pronotum, broadest between middle and anterior third, EL 1.47–1.50 mm, EW 0.66–0.69 mm, elytral index 1.4 7–1.50. Each elytron with moderately distinct humerus. Punctures deep and large, with relatively sharp margins, in anterior half dense, distances between punctures are smaller than or equal to puncture diameter, in posterior half of elytra punctures gradually reducing in diameter and becoming shallower, less distinct, each elytra with a longitudinal, sparsely and finely punctured area located along elytral suture, setation moderately dense and long, composed of setae slightly thicker than those on pronotum, suberect. Metathoracic wings well developed.

Hind legs strongly modified, with each metatibia ( Figs 6–7 ) strongly bent at anterior third with the posterior 2/ 3 flattened, forming sharp outer maginal projecting at bending side.

Aedeagus ( Figs 8–10 ) oval in ventral and dorsal view, AeL 0.36 mm, broadest near middle, with slightly emarginate apex, two lateral groups of three short setae each are located apically ondorsal wall; parameres slender, each with one apical and one subapical seta; endophallus ( Fig. 11 ) complicated, in dorsal view with strongly developed central structure, which is inversely triangular and connected to a ligulate sclerite by a M-shaped structure, and relatively weakly developed lateral components.

Female. Unknown.

Remarks. Horaeomorphus bicornis is the first species of the genus with a strongly modified head bearing both median labral and clypeal projections. Such characters were also rarely reported in other Glandulariini . In the huge genus Euconnus Thomson , E. fronticornis Franz, 1980 , described as having a horn on the anterior margin of frons (“Besitz eines stumpfen Hornes nahe dem Vorderrande der Stirn”, Franz 1980), a similar structure also occurs in the Peruvian monotypic genus Protandroconnus Franz, 1989 . However, none of the foregoing species has a labral projection. The mentum in Horaeomorphus shows some interspecifically variable, with its lateral margin sometimes elevated (Jałoszyński, unpublished observations), but no other species has such large lateral lobes as those found in H. bicornis . Strongly bent metafemora are seen in H. punctatissimus Franz, 1992 (illustrated in Jałoszyński 2006), and H. samosirensis Jałoszyński, 2009 , but no species was known with each metafemur projecting laterally at the bending side. The presence of setae on the apex of aedeagal dorsal wall was reported in the genus Euconnus (e.g., Jałoszyński 2012b, figs 43–44), but this character is for the first time reported to occur in Horaeomorphus .

Within the genus, H. bicornis shares the small and flattened body, the elongate, subtrapezoidal pronotum with paired lateral antebasal pits connected by a shallow groove, and the median antebasal pit connected anteriorly to a narrow longitudinal groove, with its Malaysian congener H. wailimae (Lhoste, 1939) ( Jałoszyński 2006, 2014a).

This is the third species described from a small area of Southwest Yunnan Prov. (another two are H. punctatus Zhou & Zhang, 2016 from Yingjiang Hsien, and H. pengzhongi Zhou & Zhang, 2016 from Tengchong Hsien). Together with an unidentifiable female mentioned below, there are already four species discovered in this area, which reveals a biodiversity hotspot of Horaeomorphus out of Sundaland.

Bionomics. Type specimens of H. bicornis were collected by sifting chips of rotten log on the roadside ( Fig. 21 ).

Distribution. Southwest China: Yunnan.

Etymology. The specific epithet refers to the labral and clypeal projections.

Figures

FIGURES 1 – 2. Dorsal habitus of Horaeomorphus species. H. bicornis, holotype male (1); H. punctatissimus, male (2).

FIGURES 3 – 7. Diagnostic characters of Horaeomorphus bicornis. Head in dorsal view (3), in ventral view (4), and in lateral view (5); left metatibia in dorsal view (6), and in lateral view (7). Abbreviation: mn, mentum.

FIGURES 8 – 12. Diagnostic characters of Horaeomorphus bicornis. Aedeagus in ventral view (8), in lateral view (9), and in dorsal view; endophallus, enlarged, in ventral view (11); and left antenna, in dorsal view (12); photographed (a) and schematic (b).

FIGURES 21 – 23. Habitat of H. bicornis in Yinjiang Hsien (21). Living male adult of H. punctatissimus on a rotten log in Mt. T