Ancystrocerus philippinus, Yin, 2020

Yin, Zi-Wei, 2020, Two new species of Ancystrocerus Raffray from the Oriental region (Coleoptera, Staphylinidae, Pselaphinae), ZooKeys 958, pp. 29-34 : 29

Ancystrocerus philippinus sp. nov. Fig. 2

Type material.

Holotype: Philippines: ♂, 'Philippines: Alamada, North Corabato, Mindanao, i.2019, local collector’ (SNUC).

Diagnosis.

Male. Length 2.6 mm (combined length of head, pronotum, elytra and abdomen). Head and pronotum finely punctate. Antennomeres 4 longer than 5, antennomeres 9 expanded and projected laterally, 10 hardly so, lateral margin of antennomeres 9 and 10 with one bunch of bristles. Pronotum with small, conical discal spine. Tergite 1 (IV) with median carina extending through entire tergal length, tergite 2 lacking such carina. Aedeagus relatively stout, median lobe symmetrical in dorso-ventral view; endophallus with several short and two elongate sclerites; parameres each elongate and with two long apical setae.

Description.

Male (Fig. 2A ). Length 2.6 mm. Head (Fig. 2B ) as long as wide, length from anterior margin of clypeus to posterior margin of vertex (excluding occipital construction) 0.46 mm, width across eyes 0.46 mm; dorsal surface finely punctate; postocular margins with rather dense tufts of hairs; eyes prominent, each composed of about 55 facets. Antennae (Fig. 2C ) elongate, with clubs (Fig. 2D ) formed by apical three antennomeres; scapes large, antennomeres 2 smaller than scapes, antennomeres 3-8 each subquadrate, 8 as long as wide and larger than each of antennomers 2-7, antennomeres 9-10 modified, antennomeres 11 largest, elongate, widest at 1/3. Pronotum (Fig. 2B ) slightly longer than wide, length along midline 0.58 mm, maximum width 0.49 mm, finely punctate, disc with small, acute spine at middle. Elytra much wider than long, length along suture 0.74 mm, maximum width 0.94 mm; shallow broad discal striae extending posteriorly to less than half elytral length. Legs simple, elongate. Abdomen wider than long, length along midline 0.78 mm, maximum width 0.87 mm. Tergite 1 (IV) approximately as long as tergite 2 (V), tergite 1 with entire and distinct median carina, which is absent on tergite 2. Length of aedeagus (Fig. 2E, F ) 0.35 mm, relatively stout, well sclerotized; median lobe curved ventrally at apex in lateral view; endophallus composed of three thick and short sclerites at apex and two elongate ones on the left; parameres elongate and flattened, each with two long setae at apex.

Female. Unknown.

Comparative notes.

Males of the new species can be readily separated from all congeners by the presence of very dense hairs along the postocular margins, the unique shape of antennomeres 9 and 10, and the structure of the aedeagal endophallus. The elongate antennomeres 9 and 10 of A. philippinus are somewhat similar to those of A. chinensis , however, the antennomeres 9 are much less expanded in the new species and the aedeagus is totally different in form and structure. Ancystrocerus philippinus further differs by tergite 1 with a complete median carina, which in A. chinensis is short and extending posteriorly only to less than half of tergal length.

The antennomeres 10 of A. irregularis Raffray, A. sumatrensis Raffray, A. rugicollis Raffray, and A. punctatus Raffray all bear one bunch of bristles on the lateral surface. In addition to the form of the aedeagal median lobe, the unique structure of the endophallus, and the different proportions of antennomeres 9-11, A. philippinus can be readily separated from the former three species by the presence of a thin bunch of bristles also on antennomeres 9, and from A. punctatus by the smooth mesal margin of antennomeres 10 (strongly protuberant in A. punctatus ).

Distribution.

Philippines: Mindanao.

Biology.

Unknown.

Etymology.

The specific epithet refers to the Philippines, where the type locality of the new species is located.

Figures

Figure 2. Ancystrocerus philippinus sp. nov., male A habitus B head dorsum and pronotum C right antenna D antennal club of right antenna E, F aedeagus in dorsal (E) and lateral (F) view. Scale bars: 1.0 mm (A); 0.3 mm (B, D); 0.5 mm (C); 0.2 mm (E, F).