Macronychus xuhaoi, Jiang & Chen, 2024

Jiang, Ri-Xin & Chen, Xiang-Sheng, 2024, A new species of the genus Macronychus Müller, 1806 from China (Coleoptera, Elmidae), Zootaxa 5419 (2), pp. 275-282 : 276-279

publication ID	https://doi.org/ 10.11646/zootaxa.5419.2.6
publication LSID	lsid:zoobank.org:pub:E7D59E77-AF1A-4DD9-809B-17552E487514
DOI	https://doi.org/10.5281/zenodo.13885318
persistent identifier	https://treatment.plazi.org/id/03B9E05B-FF9B-FF8A-FF0C-FD76FE21079F
treatment provided by	Plazi
scientific name	Macronychus xuhaoi
status	sp. nov.

Treatment

Macronychus xuhaoi sp. nov. (许浩隆¡泥甲)

( Figs 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 )

Type material (52 ♂♂, 90 ♀♀): Holotype: CHINA: ♂, labeled ‘China: Xizang (Ħǝ), Linzhi City (wī市), Motuo County (DZĸ县), Bolonggong 80K (波nū 80 K), H: 2100m, 14–18.VIII.2017, Jian-Yue Qiu & Hao Xu leg.’ ( GUGC) . Paratype: (51 ♂♂, 90 ♀♀): 41 ♂♂, 70 ♀♀, with same label data as the holotype (47 ♂♂, 85 ♀♀, GUGC; 5 ♂♂, 5 ♀♀, MYNU) ; 10 ♂♂, 20 ♀♀, labeled ‘ China: Xizang (Ħǝ), Linzhi City (wī市), Motuo County (DZĸ县), Motuo Town (DZĸDz), H: 1000m, 18.VIII.2017, Jian-Yue Qiu & Hao Xu leg. ’ ( GUGC) .

Description. Male ( Figs 1A View FIGURE 1 , 2 View FIGURE 2 , 3A–D View FIGURE 3 , 4A–E View FIGURE 4 ). Body moderately elongate ( Fig. 1A View FIGURE 1 ), black, legs and antennae dark brown, anterior margin of pronotum reddish brown. Dorsal surface shiny, covered with sparse short setae.

Head ( Fig. 2A View FIGURE 2 ) wider than long, disc covered with dense small punctures, and sparse short setae. Frons smooth, wrinkled near eyes, covered with sparse short and apical blunt setae. Eye large, oval. Clypeus covered with sparse punctures and setae slightly shorter than those of dorsal surface of head, apex of those setae cuspidal, distal part of clypeus microreticulated. Labrum transverse, shorter and narrower than clypeus, surface microreticulated, covered with sparse small punctures and long bristles at anterior portion, anterior margin almost straight, anterolateral angles rounded. Antenna ( Fig. 2B View FIGURE 2 ) 7-segmented, scape about as long as wide, expanded at apex; pedicel about twice as long as wide; antennomere III about as long as pedicel, thinner and expanded near apex; IV–VI transverse, about as long as wide; VII elongate and enlarged, long oval, apex with tuft of long setae.

Pronotum ( Fig. 2C View FIGURE 2 ) longer than wide, widest in basal 1/4, narrowed from base to apex. Surface covered with sparse short setae which are of two types, thin and short setae with apical spiculated, and distinctly longer setae with apical blunt. Anterior margin reddish-brown, curved and with angles sub-orthogonal; lateral margins sinuated; basal margin trisinuate, posterior angles acutangular, posterior half with two large admedian prebasal gibbosities separated by mesal gap. Surface of apical half of pronotum and admedian prebasal gibbosities shiny, apical 1/6 densely micropunctured, other parts of apical half and admedian prebasal gibbosities sparsely micropunctured; transverse middle impression, mesal gap and posterior angles covered with dense small punctures and weakly microreticulate. Prosternum ( Fig. 2D View FIGURE 2 ) disc of anterior half shiny, covered with sparse small punctures, each puncture bearing a long seta; sides of anterior half wrinkled; prosternal process ( Fig. 2D View FIGURE 2 ) strongly wrinkled with apex rounded.

Scutellum ( Fig. 2C View FIGURE 2 ) half fusiform, about twice as long as wide, widest at middle; surface shiny, covered with several small setigerous punctures; lateral margins finely curved, apex acute.

Elytra ( Fig. 3C View FIGURE 3 ) about twice as long as wide, parallel-sided at basal 2/3, widest near apical 1/3. Surface smooth, covered with sparse short setae, nine distinct striae composed of a row of large punctures, punctures much smaller near elytral apex. Hind wings well developed.

Metaventrite ( Fig. 3A View FIGURE 3 ) with disc smooth, covered with sparse short setae, sides with plastron setae. Median sulcus distinct, extending from posterior margin to ca. 2/3 of metasternum. Large impressions present near mesocoxae, along median sulcus and near posterior margin ( Fig. 3A View FIGURE 3 ).

Legs simple, femora weakly clavate, widest subapically. Tibiae widened in apical half. Tarsi slightly shorter than length of tibiae, protarsal segments ( Fig. 3D View FIGURE 3 ) with ventroapical tuft of long setae.

Abdomen ( Fig. 3B View FIGURE 3 ) with 5 visible sternites, surface with plastron setae. Ventrite I longest, about as long as ventrite II and ventrite III combined, disc without plastron setae, smooth, with sparse small punctures and short setae, carinae of ventrite I reduced, not reaching posterior margin. Ventrites II–V completely covered with plastron setae. Ventrite III and ventrite IV about same in length. Ventrite V slightly shorter than ventrite I, apical margin rounded and covered with dense long setae.

Aedeagus ( Figs 4 A–D View FIGURE 4 ), slender, elongate, nearly symmetrical, slightly subpically constricted in lateral view; apex almost rounded, median lobe with four sclerotizations, a pair of smaller, located near base, and two larger ones, located at 1/3 of the median lobe, surface with short hair-like setae along apical 1/2; spiculum gastrale as in Fig. 4E View FIGURE 4 . Sternite VIII ( Fig. 4F View FIGURE 4 ) with deeply emarginate apical margin.

Measurements (n=10): CL: 2.73–3.08 mm; HL: 0.33–0.38 mm, HW: 0.50–0.55 mm; PL: 0.85–0.98 mm, PW: 0.80–0.95 mm; EL: 1.88–2.10 mm, EW: 1.10–1.25 mm.

Female ( Figs 1B View FIGURE 1 , 3E View FIGURE 3 , 4G–I View FIGURE 4 ): externally similar to male, usually larger, protarsal segments ( Fig. 3E View FIGURE 3 ) lacking tuft of long setae at ventral surface. Apical margin of sternite VIII ( Fig. 4G View FIGURE 4 ) weakly rounded. Ovipositor as in Fig. 4H View FIGURE 4 , long and slender; stylus ( Fig. 4I View FIGURE 4 ) weakly curved, apex with several small sensilla; coxite ( Fig. 4I View FIGURE 4 ) with apex distinctly roundly broadened at outer margin, without sensilla; valvifer long, about twice as long as coxite, fibula with basal 1/3 distinctly expanded, finely curved at apical 1/3.

Measurements (n=10): CL: 3.10–3.40 mm; HL: 0.38–0.43 mm, HW: 0.53–0.58 mm; PL: 0.95–1.05 mm, PW: 0.90–1.00 mm; EL: 2.15–2.35 mm, EW: 1.15–1.30 mm.

Distribution. China: Only known from type locality: Motuo County, Linzhi City, Xizang Province.

Biology. All adults were collected by light trap near a hotel of Muotuo County (Linzhi City, Xizang Province; Fig. 5A View FIGURE 5 ), the adults might live in the nearby stream ( Fig. 5B View FIGURE 5 ).

Etymology. The species is named in honor of Dr. Hao Xu (Mianyang Normal University, Sichuan, China), who collected the new species and donated it to us for this study.

Comparative diagnosis. Macronychus xuhaoi sp. nov. could be placed in the Macrynychus quadriluberculatus species group based on the following characters: 1) median keel of pronotum flat with sides slightly declivous; 2) surface of metasternum covered with sparse macropunctures, each puncture bearing a long seta; 3) carinae of ventrite I not reaching posterior margin of ventrite; 4) femora moderately enlarged, not clavate.

Macrynychus quadrituberculatus species group previously included only one widely-distributed species, M. quadrituberculatus . The new species can be easily distinguished from it by the following characters: 1) admedian prebasal gibbosity of pronotum much larger; 2) elytra without impression at anterior part; 3) median lobe of aedeagus weakly gradually dilated from base to near middle, with two pairs of sclerotizations, two of them much smaller and located near base, other two larger, located at 1/3 of the median lobe (vs. median lobe of aedeagus weakly get narrowed for base to middle, with only a pair of sclerotizations located at base in M. quadriluberculatus ); 4) posterior margin of female stemite VIII weakly rounded (vs. emarginated or near straight in M. quadriluberculatus ); 5) fibula distinctly expanded at basal 1/3, finely curved near apex (vs. only expanded at apex and straight at base in M. quadriluberculatus ).

The new species is similar to Macronychus reticulatus Čiampor & Kodada 1998 in habitus character, like the moderately elongated body and legs. M. xuhaoi sp. nov. can be distinguished from the latter species by the following characters:1) body larger,> 2.5 mm; 2) femora slender and weakly clavated; 3) pronotum widest at basal 1/4 (vs. widest at basal 1/3); 4) median lobe of aedeagus not narrowed between base to middle in lateral view, with two pairs of sclerotizations (vs. median lob of aedeagus distinctly narrowed at basal 1/4, with one pair of sclerotizations located at base); 5) spiculum gastrale with base extended (vs. short and not extended at base); 6) apex of preterminal segment of ovipositor not bilobate.

Macronychus xuhaoi sp. nov. is also more or less similar to M. vietnamensis Delève, 1968 and M. levanidovae Say, 1825 , which are included in M. glabratus species group. The new species can be distinguished from them by the following characters: 1) head and tibiae without plastron setae; 2) median lobe of aedeagus with two pairs sclerotizations (vs. with three).