Euconnus (s. str.) bibaculoides, Jałoszyński, 2023

Jałoszyński, Paweł, 2023, Two new species of the Euconnus taiwanus group from Zhejiang, China (Coleoptera, Staphylinidae, Scydmaeninae), Zootaxa 5343 (3), pp. 296-300 : 297-298

Euconnus (s. str.) bibaculoides sp. n.

( Figs 1 , 3–6 )

Type material studied. Holotype ( CHINA): ♁, two labels: “CHINA: Zhejiang Prov. / Lin’an County, 400m / West Tianmu Shan N. R. / 18. v. 1996. J. Cooter ” [white, printed], “ EUCONNUS (s str.) / bibaculoides m. / P. Jałoszyński 2023 / HOLOTYPUS” [red, printed] ( MHNG).

Diagnosis. Antennal club trimerous with antennomere 9 distinctly narrower than 10; males lacking secondary sexual characters; aedeagus with pair of conspicuously long sublateral projections flanking dorsal apical plate, which is about as long as wide.

Description. Body of male ( Fig. 1 ) elongate, strongly convex; pigmentation dark brown, appendages indistinctly lighter except for clearly lighter tarsi and maxillary palps; body covered with setae distinctly lighter than cuticle; BL 1.29 mm.

Head much narrower than pronotum, broadest at eyes, HL 0.30 mm, HW 0.23 mm; tempora in dorsal view about 2.5 times as long as eyes, behind eyes strongly and evenly converging posteriorly, posterior margin of vertex strongly rounded and short, distinctly bulging posterodorsally. Eyes moderately large and weakly convex, in lateral view weakly oval. Frons and vertex with unremarkable, fine punctures, glossy; setae sparse, short and suberect, tempora and posterior margin of vertex covered with dense thick bristles. Antennae short and compact, AnL 0.43 mm, scape and pedicel each distinctly elongate, antennomeres 3‒10 each strongly transverse, 9 only slightly broader than 8 and much narrower than 10, 10 about twice as broad as long, 11 slightly longer than 9 and 10 combined, indistinctly elongate.

Pronotum subconical, broadest slightly behind middle; PL 0.34 mm, PW 0.30 mm. Pronotal base with inner pair of distinct, circular pits connected by faint transverse groove, and with distinct sublateral carinae. Punctures and setae on pronotal disc similar to those on frons and vertex; sides of pronotum with dense thick bristles.

Elytra together oval, broadest between middle and anterior third; EL 0.65 mm, EW 0.48 mm, EI 1.37; humeral calli small, elongate, each mesally demarcated by short elongate impression; elytral apices separately rounded. Punctures indistinct, superficial and unremarkable; setae sparse and suberect.

Legs slender, unmodified, all tibiae slightly curved inwards.

Aedeagus ( Figs 3–6 ) moderately elongate, weakly sclerotized, AeL 0.20 mm; median lobe in ventral view broadest in submedian region, dorsal apical plate in ventral view subtrapezoidal, about as long as wide, with rounded apex, flanked by elongate rod like projections with rounded apices; endophallic structures symmetrical, lightly sclerotized, bell-shaped with biarcuate transverse component near center of median lobe. Parameres broad and short, not reaching apex of median lobe, each with 5 long apical and subapical setae.

Female. Unknown.

Distribution. SE China (Zhejiang Province).

Etymology. The adjective bibaculoides refers to the similarity between the new species and E. bibaculatus .

Remarks. Euconnus bibaculoides sp. n. is externally almost impossible to distinguish from E. mimicus sp. n. described below. The only structure that allows for unambiguous identification is the aedeagus, which is strikingly different in these two species ( Figs 3–6 vs. 7–10). In E. bibaculatus , the dorsal apical plate is subtrapezoidal and flanked by slender, rod-like sublateral projections with rounded apices; in E. mimicus , the apex of median lobe forms a minute narrow and pointed subtriangular median process flanked by elongate sublateral projections with subtriangular apices. Moreover, the general shape of the aedeagus and endophallic structures are clearly different. The aedeagus of E. bibaculoides is shorter in relation to body length than that of E. mimicus : the ratio BL/AeL for the former species being 6.4, and for the latter only 4.8.

Interestingly, the aedeagus of E. bibaculoides is most similar to that of E. bibaculatus , a species known to occur on the southwestern Ryukyuan islands Ishigaki, Iriomote and Yonaguni. Externally, these species clearly differ in antennal structure, with E. bibaculatus having the club more elongate and antennomere 11 clearly longer than wide, whereas in E. bibaculoides the antennal club is much stouter and the terminal antennomere indistinctly elongate. The aedeagus of E. bibaculoides has the dorsal apical plate about as long as broad, and in E. bibaculatus the plate is strongly elongate.

The holotype of E. bibaculoides and of E. mimicus sp. n. described below have been collected from forest floor litter in a mature Cryptomeria forest (J. Cooter, email dated 17.07.2023).

Figures

FIGURES 1‒2. Dorsal habitus of holotype males. Euconnus bibaculoides sp. n. (1), E. mimicus sp. n. (2).

FIGURES 3‒10. Aedeagus in ventral (3, 5, 7, 9) and lateral (4, 6, 8, 10) views. Euconnus bibaculoides sp. n. (3‒6), E. mimicus sp. n. (7‒10).