Drusilla spiniventris, Assing, 2019

Assing, Volker, 2019, On the Lomechusini fauna of the Palaearctic and Oriental regions. XXVI. New species, a new synonymy, and additional records (Coleoptera: Staphylinidae: Aleocharinae), Beiträge Zur Entomologie = Contributions to Entomology 69 (1), pp. 33-70 : 60-61

Drusilla spiniventris spec. nov.

urn:lsid:zoobank.org:act:BB6FB0AD-90DC-457E-90A1-0534A8AE43D6

(Figs 53–58,145–147)

Type material: Holotype: “ PHILIPPINES: Mindanao , Sitio Bitaugan, Kawa-kawa River, 300 m, 6°46'31"N, 126°08'41"E, stream bank, wet litter, debris, dead wood, 24–26.III.2018, leg. Shavrin / Holotypus Drusilla spiniventris sp. n., det. V. Assing 2018” (cAss) . Paratype: same data as holotype (cAss).

Etymology: The specific epithet (adjective) alludes to the conspicuous spine-like process at the posterior margin of the male sternite IV.

Description: Body length 4.2–4.4 mm; length of forebody 1.8–1.9 mm. Habitus as in Fig. 53. Coloration: forebody blackish with the humeral portions of the elytra diffusely paler; abdomen black with the anterior margins of tergites III–V and the anterior halves of paratergites III–V yellow to yellowish-brown; tibiae and tarsi pale yellowish; femora black with the bases of the meso- and metafemora pale yellowish; antennae darkbrown with antennomeres I–II slightly paler brown; maxillary palpi dark-brown with the apical palpomere yellow.

Head (Fig. 54) weakly transverse and wedge-shaped; punctation extremely fine and very sparse; interstices without microreticulation. Eyes rather large, nearly twice as long as distance from posterior margin of eye to posterior constriction in dorsal view. Antenna (Fig. 55) 1.7–1.8 mm long and moderately massive; antennomeres IV and V distinctly oblong, VI–X weakly oblong, and XI slightly shorter than the combined length of IX and X.

Pronotum (Fig. 54) strongly convex in cross-section, weakly transverse, approximately 1.05 times as broad as long and approximately as broad as head, broadest at anterior angles, distinctly tapering posteriad; along midline with sharp and narrow sulcus posteriorly terminating in a deep impression; lateral margins straight in dorsal view; posterior angles obtusely marked; punctation dense and distinct; interstices without microsculpture.

Elytra (Fig. 54) approximately 0.75 times as long as pronotum, strongly transverse (width combined); punctation very dense and moderately coarse; interstices reduced to narrow ridges, without microsculpture. Hind wings not examined. Metatarsomere I longer than the combined length of III and IV.

Abdomen (Fig. 56) broader than elytra; tergite III with sparse and very fine setiferous punctation; tergites IV–VII with very sparse and extremely fine punctation, median portions of these tergites largely impunctate; tergites III–VIII practically without microsculpture, shallow traces of such microsculpture visible only at high magnification (100 x); posterior margin of tergite VII with palisade fringe.

: sternite IV (Figs 57–58) in the middle of posterior margin with a process of triangular shape; tergite VIII ( Fig. 145 ) with broadly and weakly concave, nearly truncate posterior margin, in anterior portion with numerous gland openings; sternite VIII distinctly longer than tergite VIII, with convex posterior margin, in anterior portion with numerous gland openings; median lobe of aedeagus approximately 0.55 mm long and shaped as in Figs 146–147 ; ventral process sinuate and apically acute in lateral view; parameres approximately 0.45 mm long.

: unknown.

Comparative notes: This species is characterized particularly by the modified male sternite IV and the shape of the median lobe of the aedeagus. It additionally differs from the syntopic D. shavrini , with which it shares a similar habitus and a similar coloration, by smaller body size, more extensively black meso- and metafemora, more slender antennae with oblong antennomeres V–X, smaller and less convex eyes, a pronotum with a deeper median sulcus and with straight lateral margins, longer elytra, and even less distinct microsculpture on the posterior tergites. Aside from the male primary and secondary sexual characters, D. spiniventris is distinguished from other species previously recorded from the Philippines by the combination of body size and coloration alone (see comparative notes in the section on D. shavrini ).

Distribution and natural history: The type locality is situated in the southeast of Mindanao, Philippines, and identical to that of D. shavrini . The specimens were sifted from wet litter, debris, and dead wood near a river at an altitude of 300 m.

Figures

Figs 145–165:Drusilla spiniventris(145–147), D. breviuter(148–152), Pheidologitonetes biplicatus (153–154), Zyras conlectus (155– 157), Z. hetzeli (158–159), Z. reductus(160–162), andZ. shavrini(163–165): male tergite VIII (145, 148); median lobe of aedeagus in lateral and in ventral view (146–147, 149–150, 153–156, 158–161, 163–164); female tergite VIII (151); spermatheca (152); paramere (157, 162, 165). Scale bars: 145–151, 153–165: 0.2 mm; 152: 0.1 mm.