Megarthrus chujiao Liu and Cuccodoro

Liu, Zhiping & Cuccodoro, Giulio, 2020, Megarthrus of China. Part 1. Description of a new species resembling M. antennalis Cameron, 1941 (Coleoptera: Staphylinidae: Proteininae), Zootaxa 4750 (2), pp. 269-276: 270-275

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Megarthrus chujiao Liu and Cuccodoro

sp. nov.

Megarthrus chujiao Liu and Cuccodoro  , sp. nov.

( Figs. 3–29View FIGURES 1–4View FIGURES 5–10View FIGURES 11–21View FIGURES 22–29)

Type material. Holotype, male “ China: N-Sichuan [CH12-26], 70km N Songpan, road S 301, above Gan lake , 33°15’26’’N, 103°46’03’’E, 2700m, spruce forest with birch, litter, mushroom, moss, and dead wood sifted, 12.VIII.2012, M. Schülke ” (cSch).GoogleMaps 

Paratypes: same data as holotype, 6 males, in cSch, MHNG and SWUC; “ China [26]—N-Sichuan, N Songpan, 33°15’26’’N, 103°46’03’’E, 2700m, spruce forest with birch, 12.viii.2012, V. Assing”, 2 males in cAss and MHNG; “ China, W-Sichuan (13) Daxue Shan, Hailuogou Glacier Park, Camp 1, 2100m, 29°36’00’’N, 102°03’35’’E, 27.– 31.05.1997, M. Schülke ”, 1 male and 1 female, in MHNG and cSch; “ China: Sichuan, Gongga Shan, above Camp 2 [29°57’ N, 102°00’ E], 2850m, 26.VII.1994, A. Smetana, [C25]”, 1 male, in MHNG; “ China: Yunnan: [CH07-28], Nujiang Lisu Aut. Pref., Gaoligong Shan, side valley 19km NW Liuku , 25°59’02’’N, 98°42’23’’E, 2730m, devast, prim, forest, litter sifted, 9.VI.2007, A. Pütz ”, 4 males, in MHNG and cPütGoogleMaps  .

Description. Habitus as in Figs. 3–4View FIGURES 1–4. Combined length of head, pronotum and elytra 1.8–2.1 mm; maximal pronotal width= 0.9–1.1 mm. Body and appendages predominantly rust brown, with head darker. Pubescence on frons convergent, with medial setae directed backward; metaventral setae slightly shorter than proventral setae, becoming longer anteriorly; pubescence on abdominal tergites IV–VII convergent; that on sternites IV–VII with few longer setae posteromedially, but apparently lacking macrosetae. Frons and vertex finely granulate; pronotum and elytra granulo-fossulate; prohypomera almost smooth; metaventrite coarsely punctate laterally, almost smooth in middle.

Frons above clypeus forming sharp ridge, the latter not carinate; mesal portion of disc weakly convex in lateral view, evenly; U-shaped frontal impression shallow. Temples abruptly narrowed just behind eyes, almost smooth. Occipital ridge indistinct. Antenna ( Fig. 25View FIGURES 22–29) with scape rather conical, not compressed; short and dense pubescence present only on antennomeres 5–11; antennomere 11 evenly expanded on basal two-thirds and apically rounded, slightly compressed. Pronotum ( Fig. 27View FIGURES 22–29) with hypomera lacking transverse ridge. Scutellum with anterior margin rounded. Elytral disc without notable relief.

Male. Frontoclypeal area, protarsomeres 5, metaventrite and abdominal sternites 4–6 unmodified. Protarsomeres 1 possessing ventral patch of modified adhesive setae. Metatarsomere 1 about 1.3 times as long as combined length of metatarsomeres 2–4. Peg-like setae absent from protrochanters, metatrochanters and metafemora; arranged disjunctly in 1–2 rows on protibiae ( Figs. 16–17View FIGURES 11–21); grouped in a field on mesotrochanters ( Figs. 12–13View FIGURES 11–21); arranged in two rows on mesotibiae ( Figs. 18–19View FIGURES 11–21); arranged a in single row on metatibiae, the latter prolonged apically by cluster of long setae ( Fig. 20View FIGURES 11–21). Abdominal tergite VIII as in Figs. 7, 10View FIGURES 5–10; sternite VIII as in Fig. 11View FIGURES 11–21; hemitergites IX as in Fig. 15View FIGURES 11–21; sternite IX without subbasal medial protuberance. Aedeagus as in Figs. 5–6, 8–9View FIGURES 5–10.

Female. Abdominal tergite VIII ( Figs. 28–29View FIGURES 22–29) without medioapical projection; sternite VIII as in Fig. 26View FIGURES 22–29. Genitalia ( Figs. 22–24View FIGURES 22–29) with membranose dorsal part of genital segment slightly sclerotized in middle and dark yellow; gonocoxal plate without dorsal or ventral medial ridges.

Comparisons and diagnostic notes. Megarthrus chujiao  and M. antennalis  ( Figs. 1–2View FIGURES 1–4) are the only members of the genus to have the metatibia prolonged apically by a cluster of long seta in the male. They are also the only Oriental Megarthrus  to possess protibial peg-like setae in the male. These two species can be easily distinguished by males having the shape of the aedeagal ventral wall evenly narrowed toward apex in M. chujiao  while it is abruptly narrowed at base in M. antennalis  , and in females by the presence in M. chujiao  of a pigmented weakly sclerotized mediobasal area on the dorsal part of genital segment ( Fig. 24View FIGURES 22–29), which is absent in M. antennalis  (see Cuccodoro 2003: Fig. 7eView FIGURES 5–10).

Distribution and natural history. Megarthrus chujiao  is endemic to the Hengduan Mountains of Sichuan and Yunnan provinces in China, where it was collected in spruce-birch forests, from sifted leaf litter, mushroom, moss and dead wood, at elevations ranging from 2100 to 2850 m a.s.l.

Etymology. The name of the new species means antenna in Chinese.


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