Research Article |
Corresponding author: Zhiping Liu ( lzpzena@126.com ) Academic editor: Jan Klimaszewski
© 2021 Zhiping Liu, Giulio Cuccodoro.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Liu Z, Cuccodoro G (2021) Megarthrus of China. Part 4. The M. hemipterus complex (Coleoptera, Staphylinidae, Proteininae), with description of a new species from Yunnan Province. ZooKeys 1056: 17-34. https://doi.org/10.3897/zookeys.1056.66553
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The members of the Megarthrus hemipterus species complex occurring in China, i.e., M. dentipes Bernhauer, M. flavolimbatus Cameron and M. hemipterus (Illiger), are diagnosed, and a new species attributed to this informal group, M. panda sp. nov., is described from Yunnan Province. All species are diagnosed and illustrated, and their distribution in mainland China is mapped. The limit of the M. hemipterus species complex is refined morphologically.
Endemism, Megarthrus depressus supergroup, morphology, taxonomy
This paper is the fourth of our series aiming at the taxonomic treatment of the fauna of Megarthrus Curtis, 1929 of mainland China, which consists at present of twelve species (
Here, we deal with the members of the M. hemipterus species complex, i.e., M. dentipes Bernhauer, 1938, M. flavolimbatus Cameron, 1924, and M. hemipterus (Illiger, 1794), which form a subset of the speciose and predominantly Palaearctic, Nearctic and African M. depressus supergroup (
The material treated in this study is deposited in the following collections:
cAss Volker Assing private collection (Hannover, Germany).
cPüt Andreas Pütz private collection (Eisenhüttenstadt, Germany).
cSch Michael Schülke collection (Museum für Naturkunde Berlin, Germany).
SWUC Institute of Entomology, College of Plant Protection, Southwest University, Chongqing, China.
For detailed examination, specimens were relaxed in water prior dissection. Dissected body parts were dehydrated in isopropanol (genitalia after clearing in aqueous 0.1 N solution of potassium hydroxide) and mounted in Canada Balsam on acetate slides. Drawings were made by using a drawing tube mounted on a compound microscope. The habitus images were taken using a Leica DFC425 camera in conjunction with a Leica M205–C compound microscope. Images of morphological structures were made using a Canon G9 camera mounted on a Zeiss Axioscope 50 microscope. Zerene Stacker (version 1.04) was used for image stacking. All images were modified and grouped in Adobe Photoshop CS5 Extended (version 12.0). The distribution map was captured from Google Earth.
Abdominal sternites and tergites are counted from the first morphological segment and quoted in Roman numbers (i.e., last visible tergite = tergite VIII).
The species treated below all share the following features typical of the M. depressus supergroup (
In addition they also share following characters: dorsal pubescence fairly uniform, slightly sparser on elytra than on pronotum and abdomen; pubescence on frons converging, with medial setae directed posteriad; anterior margin of frons slightly carinate, evenly convex in dorsal view; eyes hemispherical, with highest point above level of vertex; temples forming small sharp angle right behind eyes, and posteriorly abruptly narrowed, almost flat and fairly smooth; scape piriform, moderately compressed, about twice longer than wide; pronotum moderately deplanate, moderately convex in frontal view, and weakly convex in lateral view; lateral pronotal margins slightly raised on entire length, in dorsal view gently subangled at middle and strongly subangled subbasally, forming obsolete laterobasal inscision; medial groove well-marked on entire length; elytron slightly expanded posterior to humeral angle, shallowly depressed along lateral margin; lateral margin slightly carinate and denticulate, fairly straight or gently arcuate on posterior three-quarters in both dorsal and lateral views; male mesofemur longer than metafemur; male metatibia about as long as mesotibia; male abdominal sternite VIII similar to that in Fig.
In order to keep the text more concise these characters will not be repeated in their respective descriptions.
Megarthrus dentipes
Bernhauer, 1938: 17;
For detailed morphology see
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
Female. Gonocoxal plate with lateral portions of dorsobasal margin concave to middle portion subangled, markedly projecting anterad. Dorsal part of genitalia (Fig.
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.
(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,
Till now M. dentipes was known only from the Chinese Provinces of Jiangsu and Zhejiang (
Megarthrus flavolimbatus
Cameron, 1924: 164;
For detailed morphology see
Male. Protibia fairly straight and evenly expanding from base to apex; adventral side shallowly depressed transversely. Mesotrochanter with about a dozen peg-like setae arranged in two rows. Mesofemur fairly straight 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 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; metatibial peg-like setae grouped as a dense field on apical third, discontinuously with 1 peg-like seta to at most 7 peg-like setae on distal side of tooth-like process; proximal side of tooth-like process convex, with at most 1 peg-like seta. Aedeagus (Figs
Female. Gonocoxal plate with lateral portions of dorsobasal margin with oblique to middle portion truncate, markedly projecting anterad. Dorsal part of genitalia (Fig.
See above under M. dentipes.
(92 specimens): China: Fujian Prov.: N of Wutongyang, 26°03'N, 117°38'E, 12.v.2010, 1000–1700 m, leg. J. Tuma, 25 ♂ and 9 ♀ in
Megarthrus flavolimbatus is the most widespread member of the genus in the Oriental Realm, with records ranging from North India (Himachal Pradesh and West Bengal) to Yunnan Province and Taiwan in China (
Silpha hemiptera
Illiger, 1794: 597;
For detailed morphology see
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
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.
See above under M. dentipes.
(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
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 (
Holotype
(♂): China: Yunnan Prov.: Jizu Shan 25.58N 100.21E, 2500–2700 m, 6–10.vii.1994, leg. V. Kubáñ, in
Combined length of head, pronotum and elytra = 1.7–2.1 mm; maximal pronotal width = 0.9–1.3 mm. Body (Figs
Male. Protibia fairly straight and evenly expanding from base to apex; adventral side flattened. Mesotrochanter (Fig.
Female. Abdominal tergite VIII as in Figs
Megarthrus panda sp. nov., female genital segments, dorsal part in ventral view 33 and ventral part in dorsal 34 and lateral 35 views antenna 36 female tergite VIII in lateral 37 and dorsal 38 views male left hemitergite IX 39 female sternite VIII in ventral view 40. Scale bar: 0.1 mm.
Megarthrus dentipes, M. flavolimbatus, M. hemipterus and M. panda sp. nov. are the only members of the genus to have the anterior frontal margin carinate, the antennae bearing short and dense pubescence only on antennomeres 5–11, hemispherical eyes with the highest point above level of the vertex, the lateral sides of pronotum and elytra slightly deplanate, the prohypomera without a marked ridge, and the pubescence on abdominal tergites parallel. Within these species M. panda sp. nov. can be easily distinguished by the shape posterior legs of the males (Figs
The species is endemic to Yunnan Province (Fig.
Megarthrus panda sp. nov. shares the main body color and the forested mountains of Yunnan Province with its eponymous mammal the small panda, Ailurus fulgens Cuvier, 1825. Noun in apposition.
Among the four members of the M. hemipterus complex, i.e., M. dentipes, M. flavolimbatus, M. hemipterus and M. panda sp. nov., the male sexual dimorphism shows trends towards 1) moderate enlargement of the protibia with presence of a transverse adventral depression, 2) conspicuous enlargement of the metafemur and metatrochanter, and 3) presence of conspicuous tooth-like metatibial process. However, the precise phylogenetic relationships between these species have not been investigated.
The M. hemipterus complex includes both the most widespread Megarthrus species in the Palaearctic (M. hemipterus) and Oriental (M. flavolimbatus) realms, with its four constitutive members occurring in China. This country is also the only to host all species of this lineage, suggesting this area might have been its center of origin.
We warmly thank V. Assing (Hannover, Germany), M. Bohrer (