Megarthrus dentipes Bernhauer, 1938

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 dentipes Bernhauer, 1938

Figs 1-3 , 10 , 13 , 16 , 41

Megarthrus dentipes Bernhauer, 1938: 17; Cuccodoro and Löbl 1997: 1364 (detailed redescription).

Diagnosis.

For detailed morphology see Cuccodoro and Löbl (1997). Combined length of head, pronotum, and elytra 1.6-2.0 mm; maximal pronotal width = 0.8-1.1 mm. Body (Figs 1-3 ) predominantly chestnut brown, with pronotum slightly paler along lateral edges, frons slightly paler than vertex, and legs slightly paler than elytra. Anterior frontal margin slightly carinate, evenly convex in dorsal view.

Male. Protibia slightly arcuate and evenly expanding from base to apex; adventral side broadly depressed transversely. Mesotrochanter with about a dozen of peg-like setae arranged in two rows. Mesofemur slightly arcuate and swollen. Mesotibia slightly arcuate, bearing peg-like setae arranged in rows. Metatrochanter and metafemur slightly swollen; posterior margin of metatrochanter evenly arcuate; inner margin of metafemur fairly straight 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; peg-like setae grouped as dense field on apical third, and extending in fairly continuous row to apex of distal side of tooth-like process; proximal side of tooth-like process convex, with at most 2 peg-like setae. Aedeagus (Figs 10 , 13 ) with ventral wall slightly narrowed at base and evenly narrowed to blunt right-angled apex in ventral view, and with ventral outline slightly sinuate to apex slightly recurved ventrally in lateral view.

Female. Gonocoxal plate with lateral portions of dorsobasal margin concave to middle portion subangled, markedly projecting anterad. Dorsal part of genitalia (Fig. 16 ) with evenly thick semi-circular sclerite.

Comparisons and diagnostic notes.

Megarthrus dentipes resembles in most characters of M. flavolimbatus and M. hemipterus . These species can be distinguished by the shape of the anterior frontal margin (i.e., evenly arcuate in M. dentipes and M. hemipterus , while more convex at middle than laterally in M. flavolimbatus ) and the coloration (i.e., head fairly concolor with pronotum, and legs paler than elytra in M. dentipes and M. flavolimbatus , instead of markedly darker than the pronotum, and legs concolorous with the elytra in M. hemipterus ). The males also differ by the shape and vestiture of the metatibial tooth-like process (i.e, its proximal side is flattened in M. hemipterus instead of convex in M. dentipes and M. flavolimbatus , and bearing peg-like setae on its distal side in a fairly continuous row to the apex in M. dentipes , while discontinuoulsy in M. flavolimbatus and M. hemipterus ). The shape of the apical portion of the aedeagus ventral wall is diagnostic (i.e., subangulate in M. dentipes (Fig. 10 ), angulate in M. flavolimbatus (Fig. 11 ), and mucronate in M. hemipterus (Fig. 12 )), as well as that of the medial portion of the dorsobasal margin of the gonocoxal plate (i.e., truncate and projecting anterad in M. flavolimbatus , subangled and projecting anterad in M. dentipes , and mucronate in M. hemipterus ).

Material examined.

(78 specimens): China: Fujian Prov.: Guadun, "Kuatun, Fukien, Tschung Sen [sic], 5.iv.1946, leg J. Klapperich ", 1 ♂ in NHMW; 10 km E Yong’an, 25°58'N, 117°27'E, 31.v. 2008, 700 m, leg. J. Tuma, 2 ♀ in NHMW; Fenshui Guan , 27.9N, 117.85E, 7.v.2005, 1700 m, leg. J. Tuma, 10 ♂ and 13 ♀ in NHMW, MHNG & ZMUC; 2km SE Xinqian, 27.05N, 117.1E, 10.v.2005, 1700 m, leg. J. Tuma, 4 ♂ and 6 ♀ in NHMW & MHNG; Ziyungdongshan, NW slopes, 25°46'N, 117°20'E, 25.iv.2006, 900- 1000 m, leg. J. Tuma, 1 ♂ and 3 ♀ in NHMW ; Guangdong Prov.: Nanling National Nature Reserve, Dadongshan , 24°54.7'N, 112°43.1'E, 770 m, 20-21.iv. 2013, leg. J. Hájek 6 J. Růžička, 1 ♂ in NHMP ; Hubei Prov.: Mulu Shan , Jiugongshan forest park, 29.4N 114.6E, up to 1000 m, 3.v-18.vi.2002, leg. J. Tuma, 2 ♂ and 4 ♀ in NHMW ; Hunan Prov.: Shunhuangshan forest park, 26°22-23'N, 111°00-01'E, 20.vi.2013, 1300-1600 m, leg. Jatua, 5 ♂ and 4 ♀ in NHMW & MHNG ; Jiangxi Prov.: Jinggangshan Mts, Xiangzhou (forested valley S of the village), 26°35.5'N, 114°16.0'E, 374 m, (steam valley), 26.iv.2011, leg. Fikáček and Hájek, Jia and Song, [MF08] cut and decaying tops of bamboo trunks at the side of a trail in the secondary forest and among the fields, 1 ♂ and 2 ♀ in NHMP; Jinggangshan Mts , Songmuping , 26°34.7'N, 114°04.3'E, 1280 m, (stream valley), 27.iv.2011, leg. Fikáček, Hájek, Jia and Song [MF10] cut and decaying tops of bamboo trunks in a sparse bamboo bush, 7 ♂ and 6 ♀ in NHMP, MHNG & ZMUC; Jinggangshan Mts , Huyagta , 26°29.9'N, 114°07.3'E, 1490 m, 28.iv.2011, leg. Fikáček, Hájek, Kubeček, Jia, Song and Zhao, [MF12] cut and decaying tops of bamboo trunks in a sparse secondary bamboo forest, 2 ♂ and 2 ♀ in NHMP ; Zhejiang Prov.: Baima Shan , 28°37'N, 119°09'E, 7-17.vi.2008, 1270- 1520 m, leg. J. Tuma, 1 ♂ and 1 ♀ in NHMW .

Distribution and natural history.

Till now M. dentipes was known only from the Chinese Provinces of Jiangsu and Zhejiang ( Cuccodoro and Löbl 1997: 1364). The new materials examined indicate that the species occurs in Zhejiang Province also at Baima Shan, as well as in several other localities of Hubei, Fujian, Jiangxi, and Guangdong Provinces (Fig. 41 ), where it was collected at elevations ranging from 374 to 1700 m a. s. l., mainly in rotten bamboo trunks and decaying cut tops of bamboo trunks.

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 1 - 3. Megarthrus dentipes Bernhauer: habitus, male: dorsal 1 ventral 2 and lateral 3 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.