Pseudotachinus bilobus

Yin, Zi-Wei & Li, Li-Zhen, 2018, A new species and an additional record of Pseudotachinus Cameron from China (Coleoptera: Staphylinidae: Tachyporinae), Zootaxa 4425 (3), pp. 567-574: 568-569

publication ID

publication LSID

persistent identifier

treatment provided by


scientific name

Pseudotachinus bilobus


Comparative diagnosis. Pseudotachinus bilobus  is quite distinct among the genus, and can be readily separated from all congeners by a unique combination of the following features: 1) dorsal surface of the body completely lacks microsculpture 2) the color of the pronotal lateral margins is much lighter than that of the disc, 3) the elytra are markedly transverse (EW / EL = 1.48–1.60), 4) the male sternite VII lacks rows of transparent setae along the posterior margin, 5) the posterior margin of male tergite VIII is angularly protruding posteriorly at middle, 6) the median lobe of female tergite VIII is about as wide as lateral lobes, and 7) the female sternite VIII lacks well-defined median pair of lobes at the posterior margin.

Description. Male. Body ( Fig. 1A View Figure ) flattened, moderately stretched. Measurements: TBL 4.5–5.84 mm, FBL 3.61– 3.39 mm, HL 0.71–0.73 mm, HW 1.01–1.02 mm, EyL 0.26–0.33 mm, AnL 1.95–2.17 mm, PL 1.23–1.40 mm, PW 2.18–2.48 mm, EL 1.40–1.59 mm, EW 2.23–2.49 mm. Head, pronotal disc, elytra, and most parts of abdomen dark-brown, mouthparts, antennae, pronotal lateral margins, apex of abdomen, and legs reddish-brown.

Head ( Fig. 2A View Figure ) strongly transverse, finely and sparsely punctate, lacking microsculpture; eyes hemispherical, roundly protruding laterally, areas mesal to eyes longitudinally impressed ( Fig. 2A View Figure ), lateral area of genae with transverse microsculpture ( Fig. 2B View Figure ); antennae ( Fig. 1A View Figure ) elongate, all antennomeres much longer than wide; antennomeres I–IV lacking dense, fine setae, which are present on antennomeres V–XI. Pronotum ( Figs 1A View Figure , 2C View Figure ) markedly transverse (PI = 1.77–1.83), flattened; longitudinal impressions broad and shallow, present at anterior 3/4 of pronotal length; anterior corners broadly rounded; posterior corners strongly protruding posterolaterally; lateral margins clearly furrowed, impression slightly narrowing anteriorly and posteriorly; whole surface of pronotum finely punctate, smooth, lacking microsculpture. Scutellum lacking microsculpture. Elytra ( Fig. 1A View Figure ) strongly transverse (EI = 1.47–1.59), about as broad as pronotum; punctures ( Fig. 2D View Figure ) much stronger than those of head and pronotum; lacking microsculpture. Hind wings fully developed. Lateral area of prosternum ( Fig. 2E View Figure ) with small tuft of fair hair; mesoventrite ( Fig. 2E View Figure ) with dense transverse microsculpture, median carina thin and slightly raised ( Fig. 2F View Figure ). Protarsi ( Fig. 2G View Figure ) much broader than meso- and metatarsi. Abdomen lacking microsculpture; with slightly elongate punctures on segments IV–VI ( Figs 1A View Figure , 2H View Figure ), which are about as dense and strong as those of elytra, punctures on segments VII–VIII finer; tergite VIII ( Fig. 3A–B View Figure ) with four short lobes separated by short angularly rounded incisions at posterior margin; tergite IX ( Fig. 3C View Figure ) divided laterally to two lobes, each apically with long, spiniform macrosetae; posterior margin of sternite VII ( Fig. 3D View Figure ) broadly and shallowly emarginate at middle, lacking row of transparent bristles (bristles present in other congeners); posterior emargination of sternite VIII ( Fig. 3E–F View Figure ) angularly protruding posteriorly at middle; sternite IX ( Fig. 3G View Figure ) rounded at apex, with several very long bristles. Aedeagus ( Fig. 3H–I View Figure ) strongly elongate, parameres narrow, and broadly separated at base, apices tapering in dorsal and ventral view, slightly curved ventrally in lateral view; central part of endophallus ( Fig. 3J View Figure ) almost symmetric.

Female. General habitus ( Fig. 1B View Figure ) similar to male; size generally larger. Measurements: TBL 5.2–6.17 mm, FBL 3.34–4.0 mm, HL 0.73–0.88 mm, HW 1.08–1.20 mm, EyL 0.27–0.33 mm, AnL 2.0– 2.61 mm, PL 1.25–1.43 mm, PW 2.35–2.56 mm, EL 1.44–1.70 mm, EW 2.31–2.61 mm. Tergite VIII ( Fig. 4A–B View Figure ) tri-lobed, with median lobe longer than and about as broad as lateral lobes; sternite VIII ( Fig. 4C–D View Figure ) with only two distinct lobes at posterior margin, median and outer pairs of lobes largely reduced, apices of median lobes each with apical rim consisting of 10 transparent bristles; segments IX–X and styli as in Fig. 4E View Figure .

Distribution. China: Guizhou, Guangxi ( Fig. 5 View Figure ).

Etymology. The specific epithet refers to the presence of only two well-developed lobes at the posterior margin of female sternite VIII, which is an unusual character state in the genus.