Megarthrus budai Liu and Cuccodoro, 2020

Liu, Zhiping & Cuccodoro, Giulio, 2020, Megarthrus of China. Part 2. Megarthrus basicornis Fauvel, 1904 with description of a new species from Mount Emei (Coleoptera: Staphylinidae: Proteininae), Zootaxa 4895 (1), pp. 124-134 : 130-134

Megarthrus budai Liu and Cuccodoro , sp. nov.

( Figs 8-9 , 12-39 )

urn:lsid:zoobank.org:act:836693E2-8AB5-4D0C-99A7-F61FAE36CD25

Type material. Holotype, male “ China: Sichuan, Emei Shan , N29°33’00’’ E103°21’38’’, 28.v.2011, 1639m, sift08, V. Grebennikov ”( MHNG).

Paratypes: same data as holotype, 1 male in SWUC and 3 females, in MHNG ; “ China, Sichuan, Emei Shan , N29°33’04’’ E103°21’19’’, 25.v.2011, 1729m, sift05, V. Grebennikov ”, 1 male and 5 females in MHNG and 1 female in SWUC .

Description. Habitus as in Figs 14-16 . Combined length of head, pronotum, and elytra 1.7-1.9 mm; maximal pronotal width 0.9-1.1 mm. Body predominantly chestnut brown, with head darker and appendages slightly paler, and lateral portions of pronotum markedly paler. Dorsal pubescence fairly uniform, but denser on basal portion of elytra; pubescence on frons converging, with medial setae directed backward; metaventral setae shorter than proventral setae, becoming longer anteriorly; pubescence on abdominal tergites IV-VII parallel; sternites IV-VII with few longer setae posteromedially, but apparently lacking macrosetae. Frons and vertex finely granulate; pronotum and elytra granulo-fossulate; prohypomeron almost smooth ( Fig. 9 ); metaventrite coarsely punctate laterally, almost smooth in middle.

Frons above clypeus forming sharp ridge, the latter very finely carinate; mesal portion of disc weakly convex in lateral view, evenly; U-shaped frontal impression shallow. Temples slightly expanded just behind eyes, then abruptly narrowed, almost smooth. Occipital ridge indistinct. Antenna ( Fig. 32 ) with scape fairly conical, not compressed; short and dense pubescence present only on antennomeres 5-11; antennomere 11 rather ovoid, slightly compressed. Pronotum as in Fig. 8 ; hypomera lacking transverse ridge ( Fig. 9 ). Scutellum with anterior margin rounded. Elytral disc without notable relief.

Male. Frontoclypeal area, protarsomere 5, metaventrite, and abdominal sternites IV-VI unmodified. Protarsomere 1 possessing ventral patch of modified adhesive setae ( Figs 12-13 ). Metatarsomere 1 about 1.3 times as long as combined length of metatarsomeres 2-4. Peg-like setae absent from protrochanter, metatrochanter, femur, and protibia; arranged in a row on mesotrochanter ( Fig. 19 ); grouped in a field on mesotibiae ( Figs 23-24 ) and metatibiae ( Figs 25-26 ). Metaventrite markedly swollen in middle. Abdominal tergite VIII as in Figs 20, 22 ; sternite VIII as in Fig. 17 ; hemitergites IX as in Fig. 29 ; sternite IX without subbasal medial protuberance. Aedeagus as in Figs 27-28, 30-31 .

Female. Abdominal tergite VIII ( Figs 37-38 ) forming a medioapical projection; sternite VIII as in Fig. 36 . Genitalia as in Figs 33-35 .

Comparisons and diagnostic notes. In the Palaearctic and Oriental regions Megarthrus budai is easily distinguished from its congeners by its deplanate pronotum in combination with the absence of a hypomeral ridge, the presence of short and dense pubescence only on the antennomeres 5-11, and the scape fairly conical and not compressed. Its sexual characters are also diagnostic. The new species possesses a ventral patch of modified adhesive setae on the male protarsomere ( Figs 12-13 ), a feature uniquely shared in the genus by all the members of the M. depressus supergroup ( Cuccodoro 2011). However, neither the shape of its aedeagus nor the male modifications of the legs resemble any of the species currently included in this main lineage of Megarthrus , and thus its affinities remain unclear.

Distribution and natural history. Megarthrus budai sp. nov. is endemic to Mount Emei of Sichuan province in China ( Fig. 39 ), where it was collected from sifted litter, at elevations ranging from approximately 1600 to 1750 m a.s.l.

Etymology. The new species is named after the tenth-century Buddhist monk Budai, famous for his representations with a laughing face and round stomach, with reference to the swollen metaventrite of the males of this species. Name in apposition.

Figures

FIGURE 39. Distribution map of Megarthrus basicornis Fauvel (pink squares) and Megarthrus budai sp. n. (red circle). Scale bar =200 km.

FIGURES 6-9. Megarthrus basicornis Fauvel (6-7) and M. budai sp. n. (8-9): prothorax in dorsal (6, 8) and ventral (7, 9) views. Scale bar = 0.2 mm.

FIGURES 10-13. Megarthrus basicornis Fauvel (10-11) and M. budai sp. n. (12-13): Portarsus of male in ventrolateral (10, 12) and ventral (11, 13) views. Ovals indicate absence (red) or presence (green) of ventral patch of modified adhesive setae (green arrows). Scale bar = 0.1 mm.

FIGURES 14-16. Megarthrus budai sp. n., habitus, male: dorsal (14), ventral (15), and lateral (16) views. Scale bar = 0.5 mm.

FIGURES 17-26. Megarthrus budai sp. n., male: abdominal sternite VIII in ventral view (17); protrochanter and profemur in lateral view (18); mesotrochanter and mesofemur in lateral view (19); metatrochanter and metafemur in lateral view (21); abdominal tergite VIII in lateral (20) and dorsal (22) views. mesotibia in lateral (23) and ventral (24) views; metatibia in lateral (25) and ventral (26) views. Scale bar = 0.1 mm.

FIGURES 27-32. Megarthrus budai sp. n., male: aedeagus in lateral (27, 28) and ventral (30, 31) views; hemitergite IX (29); antenna (32). Scale bar = 0.1 mm.

FIGURES 33-38. Megarthrus budai sp. n., female: genital segments, ventral part in dorsal (33) and lateral (34) views, and dorsal part (35) in ventral view; abdominal sternite VIII in dorsal view (36); abdominal tergite VIII in dorsal (37) and lateral (38) views. Scale bar = 0.1 mm.