Scydmaenus (Scydmaenus) shanghaicus Yin & Zhou, 2025

Yin, Zi-Wei, Zhou, De-Yao, Wang, Qing & Hu, Jia-Yao, 2025, A new species and an additional faunistic record of Scydmaenus Latreille (Coleoptera: Staphylinidae: Scydmaeninae) from Shanghai, China, Zootaxa 5659 (1), pp. 127-132 : 128-130

Scydmaenus (Scydmaenus) shanghaicus Yin & Zhou , sp. nov.

( Figs 1 , 2 )

Type material (4 exx.). HOLOTYPE: CHINA: ♂, ‘China: Shanghai, Chongming, Dongtan Wetland Park , 31°30'55"N, 121°56'38"E, alt. 1 m, 13.v.2025, sifted, Hu et al. leg., 上ả崇ẹ东ûȃ地½园, DZ佳ae, ȒAEŤ, H佳ś, êḙī ’ ( SNUC) . PARATYPES: CHINA: 1 ♀, same collecting data as for holotype; 1 ♂, ‘ China: Shanghai, Jiading , 31°21'15"N, 121°14'2"E, alt. 5 m, 7.v.2022, decomposing Populus log, D.-Y. Zhou leg., 嘉îḿ ẅṽ化*周ª尧ī ’; 1 ♀, same location and collector, except ’ 24.v.2025 ’ (all deposited in SNUC) .

Diagnosis. Male. Body length approximately 1.7 mm. Head and pronotum finely punctate. Head slightly wider than long, suboval, tempora in dorsal view approximately 1.7× as long as eyes; antenna with antennomere 5 as long as 2, and slightly longer than 4 and 6. Pronotum slightly longer than wide, with four small but distinct antebasal pits. Metaventrite and legs lacking modifications. Aedeagus slender and elongate, in dorsal view narrowing from base to apex and with tapered apex, in lateral view sinuate in form; each side of ostium with row of six setae; endophallus armature composed of an elongate, tuberculate sclerite in apical portion and a short, transverse sclerite at middle. Female. Body length subequal to male. Spermatheca dome-shaped, with thin and long ductus spermathecae and coiled accessory gland.

Description. Male. Body elongate, dorsally moderately convex; length 1.67 mm; color uniformly red brown; tarsi and mouthparts slightly paler; integument with dense, light-brown pubescence.

Head in dorsal view broadest posterior to eyes, slightly wider than long; length 0.32 mm, width 0.37 mm; vertex and frons confluent, evenly convex; postantennal tubercles weakly demarcated; tempora, in dorsal view, approximately 1.7× eye length; eyes moderately convex, in lateral view semioval; frons and vertex finely, sparsely punctate, setae relatively long, dense, suberect; antenna ( Fig. 1B ) slender, length 0.88 mm, antennomeres 1–5 each strongly elongate, 6–8 gradually shorter, antennal club of enlarged antennomeres 9–11, length 0.35 mm, antennomere 9 about as long as broad, 10 distinctly larger than 9, 11 much shorter than 9 and 10 combined, approximately 1.6× as long as wide.

Pronotum in dorsal view broadest slightly anterior to distal 1/3, length 0.50 mm, width 0.45 mm; anterior margin broadly convex, lateral margins rounded in anterior half, nearly straight and distinctly convergent posteriorly in posterior half, posterior margin weakly sinuate; four small, distinct antebasal pits present; pronotal disc finely, shallowly punctate, punctures separated by more than their diameters; setae moderately long, dense, suberect.

Elytra conjointly elongate-oval, broadest near midlength, length 0.89 mm, width 0.69 mm, length/width 1.29; humeral calli prominent; basal impressions short, indistinct; suture weakly elevated anteriorly, not demarcated by grooves; elytral apices separately rounded; elytral punctation slightly more distinct, coarser, and deeper than on pronotum, punctures separated by more than their diameters; setae moderately dense, long, suberect, as dense as on head and pronotum but distinctly longer than pronotal setae, not forming setal patterns. Metathoracic wings fully developed, functional.

Legs moderately long, robust, unmodified, including protarsi.

Mesoventrite medially carinate; metaventrite unmodified.

Aedeagus ( Fig. 1C–E ) markedly elongate, slender, length 0.56 mm; median lobe in dorsal view narrowing from base to tapered apex, lateral margins slightly concave below basal 1/3, in lateral view basal half slightly broader than distal half, regions near basal 1/3 and apex curved dorsally, basal curvature more pronounced than apical; ostium flanked by two rows of six setae each, setae gradually decreasing in length basally, apex of dorsal wall with four additional short median setae, endophallic armature composed of elongate, sinuate, tubular sclerite in apical half, and short, transverse sclerite at middle.

Female. Externally similar to male. Body length 1.68 mm, length/width of head 0.36/ 0.38 mm, pronotum 0.48/ 0.45 mm, elytra 0.91/ 0.71 mm, length of antenna 0.89 mm, elytral length/width 1.28. Spermathecae ( Fig. 1F ) dome-shaped, greatest diameter 0.12 mm; ductus spermathecae membranous, thin and elongate; accessary gland thick and coiled.

Comparative notes. Among the 17 species recorded from China and other East Asian congeners, this species shows resemblance to S. obuncatus Kurbatov distributed in Primorsky, Russia ( Kurbatov 1993: figs ∂, е), and to S. hainanensis O’Keefe from Hainan Island, China ( O’Keefe & Li 1999: fig. 3a–c), particularly in the sinuate lateral profile of the aedeagus. The aedeagus of S. shanghaicus sp. nov. is, however, markedly more elongate and slenderer, and narrowing dorsoventrally from its base to the apex. Furthermore, the apical portion of its endophallic armature is composed of an elongate sclerite, versus a broad plate in S. obuncatus , or a complex group of sclerites in S. hainanensis . Scydmaenus obuncatus presents a slightly greater body size (1.7–1.8 mm), whereas S. hainanensis attains a body length exceeding 2.8 mm.

Distribution. China: Shanghai.

Biology. Two adults ( Fig. 2A ) from Chongming were sifted from leaf litter and decaying plant matter along a riverbank ( Fig. 2B ). Adults from Jiading were collected under the bark of decomposing Populus logs ( Fig. 2C, D ).

Etymology. The specific epithet is derived from Shanghai, the city and type locality where this species was discovered. The name is an adjective in the nominative case.

Figures

FIGURE 1. Scydmaenus (Scydmaenus) shanghaicus sp. nov. (A–E. Male. F. Female). A. Dorsal habitus. B. Antenna. C–E. Aedeagus, dorsal (C, D) and lateral (E). F. Spermatheca, lateral. Scale bars: 0.5 mm in A; 0.2 mm in B–E; 0.1 mm in F.

FIGURE 2. In-situ photograph and habitats of Scydmaenus (Scydmaenus) shanghaicus sp. nov. A. A living adult from Chongming. B. Collection site in Chongming, where individuals were sifted along a riverbank. C, D. Collection site and microhabitat in Jiading, specimens were collected under the bark of decomposing Populus logs.