Megarthrus hemipterus (Illiger, 1794)

Liu, Zhiping & Cuccodoro, Giulio, 2021, Megarthrus of China. Part 4. The M. hemipterus complex (Coleoptera, Staphylinidae, Proteininae), with description of a new species from Yunnan Province, ZooKeys 1056, pp. 17-34 : 17

Megarthrus hemipterus (Illiger, 1794)

Figs 7-9 , 12 , 15 , 18 , 41

Silpha hemiptera Illiger, 1794: 597; Cuccodoro 1996: 485 (new synonymy, Japanese records); Cuccodoro and Löbl 1997 (synonymic framework, detailed redescription, general distribution, the first record for China); Cuccodoro et al. 2011 (synonymic framework, photograph of dorsal habitus, records in Korea).

Diagnosis.

For detailed morphology see Cuccodoro and Löbl (1997). Combined length of head, pronotum, and elytra 1.6-1.9 mm; maximal pronotal width = 0.9-1.1 mm. Body and appendages (Figs 7-9 ) rust brown; head markedly darker with frons slightly paler than vertex. Anterior frontal margin slightly carinate, evenly convex in dorsal view.

Male. Protibia fairly straight and slightly enlarged toward apex, evenly, with adventral side markedly depressed transversely at middle. Mesotrochanter with about a dozen of peg-like setae arranged in two rows. Mesofemur slightly arcuate and slightly swollen. Mesotibia subangulate, bearing peg-like setae arranged in one row. Metatrochanter and metafemur slightly swollen; posterior margin of metatrochanter evenly arcuate; inner margin of metafemur slightly concave in ventral view, forming sharp ridge on entire length. Metatibia swollen, at middle forming conspicuous tooth-like process projecting above flattened apical portion of metatibia; metatibial peg-like setae arranged in 1-2 rows on apical third, the latter group of 15-20, discontinuously with more than 12 peg-like setae arranged in two rows on distal side of tooth-like process; proximal side of tooth-like process broad and flat, bearing 4-10 scattered peg-like setae. Aedeagus (Figs 12 , 15 ) with ventral wall not narrowed at base and gradually narrowed to mucronate apex in ventral view, with ventral fairly straight to apex in lateral view.

Female. Gonocoxal plate with lateral portions of dorsobasal margin straight to middle portion forming small blunt process slightly projecting anterad. Dorsal part of genitalia with arcuate sclerite wider at middle (Fig. 18 ).

Comparisons and diagnostic notes.

See above under M. dentipes .

Material examined.

(4 specimens): China: Beijing: ca 1400 m, Dongling Mts, Xiaolongmen, Liu Lang Yu , 39.97N, 115.43E, 15.vi.2001, leg. J. Cooter & P. Hlavá, mixed woodland litter, 1 ♀ in MHNG ; Heilongjiang Prov.: “Süd-Mandshurei Chi-Kuan Shan, leg K. Rost ", 2 ♂ and 1 ♀ in FMNH .

Distribution and natural history.

Megarthrus hemipterus is the most widespread member of the genus, with records ranging from the United Kingdom in the West to China, South Korea, Japan, and Far East Russia in the East ( Cuccodoro 1996; Cuccodoro and Löbl 1997; Cuccodoro et al. 2011). It occurs in a wide range of microhabitats (carrion, fungi, leaf litter, and various types of decaying organic matter); in South Korea it was abundantly collected from fresh and rotten fungi. The first record for China without precise locality data ( Cuccodoro and Löbl 1997) refers to the three specimens cited here from Chi-Kuan Shan from the Max Bernhauer’s collection, housed in the FMNH. The species, which occurs on most land masses surrounding the Sea of Japan, seems to reach its southern limit of extension in China in the Western Hills (Fig. 41 ), where it was collected in mid-April at 1400 m a. s. l. from mixed woodland litter on Mount Dongling (Beijing).

Figures

Figure 41. Distribution map in China of Megarthrus dentipes Bernhauer, M. flavolimbatus Cameron, M. hemipterus (Illiger) and Megarthrus panda sp. nov. Scale bar: 300 km.

Figures 7 - 9. Megarthrus hemipterus (Illiger): habitus, male: dorsal 7 ventral 8 and lateral 9 views. Scale bar: 0.5 mm.

Figures 10 - 18. Megarthrus dentipes Bernhauer (10, 13, 16) M. flavolimbatus Cameron (11, 14, 17) M. hemipterus (Illiger) (12, 15, 18) male: aedeagus in ventral (10 - 12) and lateral (13 - 15) views female: genital segments, dorsal part (16 - 18) in ventral view. Scale bars: 0.1 mm.