﻿A systematic review of the genus Bolbelasmus Boucomont (Coleoptera, Geotrupidae, Bolboceratinae) from Indochina and surrounding areas

﻿Abstract Indochinese species of the genus Bolbelasmus (Coleoptera, Geotrupidae, Bolboceratinae) are reviewed. Three new species, Bolbelasmuschifengi Wang & Li, sp. nov., Bolbelasmusconcavisuturalis Li & Wang, sp. nov. and Bolbelasmusyutangi Li & Wang, sp. nov., are described and illustrated. An annotated checklist and modified key to species of the genus are provided. Information for each species in the checklist includes literature review, synonymy, distribution and type locality.


Introduction
Bolbelasmus Boucomont, 1910 (Coleoptera: Geotrupidae: Bolboceratinae: Bolboceratini) is one of the largest bolboceratine genera, currently consisting of 29 species and two subspecies (Schoolmeesters 2023) (including subgenus Kolbeus).Among bolboceratine genera, Bolbelasmus has the widest distribution, occurring throughout the Holarctic and Oriental regions (Li et al. 2008;Hillert et al. 2016).Krikken (1977) published the most recent review dealing with eastern and southeastern Asian species and provided a complete checklist and summary of generic affinities and notes of species from the Middle East and North Africa.In that paper, two new species were described including one, Bolbelasmus meridionalis Krikken, 1977, from Southeast Asia.Additional distribution data were provided for B. coreanus (Kolbe, 1886) in southwestern China, Thailand and India.The Indochinese Bolbelasmus species have received little attention since Krikken's (1977) work.Zinchenko (2016) described a new species, B. korshunovi Zinchenko, from northern Thailand, the only species described during the past four decades.Currently, ten species are recorded in eastern and southeastern Asia, including the three new species described here ZooKeys 1191: 287-305 (2024), DOI: 10.3897/zookeys.1191.114021 Chun-Lin Li & Chuan-Chan Wang: Review of the genus Bolbelasmus from Indochina based on specimens recently obtained from the Indochinese Peninsula and neighboring areas, including the first record from Myanmar.These collections constitute the basis for further detailed knowledge of the Indochinese bolboceratine fauna.
The natural histories of eastern and southeastern Asian Bolbelasmus species are poorly documented.Tsukamoto et al. (2017) reported that two of the Japanese species, B. nativus ishigakiensis Masumoto and B. shibatai Masumoto inhabit densely forested montane areas, where adults are nocturnal and fly about 30 cm over the forest floor from late dusk to midnight.Adults of both species can be sporadically attracted to light, as observed with B. coreanus (Kolbe) in Taiwan (Li et al. 2008).Bolbelasmus specimens can occasionally be collected using baited traps (e.g., Kawai et al. 2005;Li et al. 2008).
In this paper, we review the species of Bolbelasmus occurring in the Indochinese Peninsula and neighboring areas, with descriptions of three new species.We also provide an annotated checklist, distributional data for known species in eastern and southeastern Asia, and a modified key.

Material and methods
The type specimens of the two new species, B. chifengi and B. yutangi, were collected by flight interception traps (FIT).The depository of the type specimens is in the following institutions: National Museum of Nature and Science (NSMT, Tsukuba, Japan); Zoological Museum, University of Copenhagen (ZMUC, Copenhagen, Denmark); Taiwan Agriculture Research Institute (TARI, Taichung, Taiwan); and the private collection of Chun-lin Li (CCLI, Nantou, Taiwan).Habitus images of Bolbelasmus specimens were taken using a Canon 7D digital camera with a Canon EF 100 mm macro lens and a Canon Macro Twin Lite MT-24EX Flash.Detailed images of specimens, body parts and male genitalia were captured using a Leica M205C stereo microscope equipped with a Leica MC190HD microscope camera or by a Hitachi TM3030 Plus tabletop scanning electron microscope.Color images were processed using Helicon Focus v.8.2.0 to increase depth of field, and all images were edited in Adobe Photoshop v.24.0.0 (background removed, images integrated, numbered and scale bars added).Measurements, treatments, and preservation of specimens and genitalia are based on methods described by Li et al. (2008).

Taxonomy
Bolbelasmus Boucomont, 1910 Diagnosis.Species of Bolbelasmus are small to medium-sized (5.6-15.2mm in body length) and can be recognized by the glossy, unicolored, reddish-brown to black dorsal surface; presence of a conical frontal tubercle with a rounded or bifurcated tip in males; transverse frontal carina present in females; eyes protruding, divided by a canthus anteriorly, canthus with anterior margin smooth; antennal club with first segment glabrous on inner side; pronotum usually quadrituberculate in major males (vestigial or reduced to bituberculate in minor males), females with transverse carina only; first elytral stria terminated by scutellum; parameres usually weakly sclerotized.4).Body length 9.7 mm; width across humeri 6.0 mm.Dorsum moderately shiny.Head, pronotum and scutellum dark brown with elytra reddish brown.Head (Fig. 12): labrum with anterior margin crenulate, disc transversally rugose.Clypeus trapezoidal, surface densely rugopunctate; protrusion at basal angle moderately developed.Clypeofrontal suture well defined, distinctly curved in front of frontal tubercle.Frons with surface sparsely punctate, punctures fine, frontal tubercle vertically located in junction of suture, right-triangle in shape in lateral view.Eye prominent, canthus simple, not exceeding eye.Thorax: pronotum (Fig. 18) quadrituberculate, tubercles placed in a line, lateral tubercle greatly reduced in size; anterior face of median tubercles almost perpendicular to plane of pronotum; primary punctures coarse, moderately distributed on disc and intermixed with impunctate area, punctures between lateral margins of pronotum and fovea bigger and denser, posterior area between elytral humeri and suture impunctate except for four coarse punctures in front of scutellum, secondary punctures tiny, evenly scattered throughout surface of pronotum; frontal and lateral margins beaded, posterior margin beaded only in front of elytral humeri.Scutellum elongate, secondary punctures sparse throughout surface with a coarse puncture at center.Elytron (Fig. 24): elytral striae shallow, punctures mostly spaced 2-3 times diameters of punctures.Intervals slightly convex including sutural one, surface with scattered secondary punctures.Male genitalia (Figs 31,32,40).
Female (Figs 46,47).Body length 7.7-10.0mm; width across humeri 5.4-6.5 mm.Similar to male with minor differences in the form of strongly wrinkled surface of clypeus, transverse frontal carina trilobed, central lobe more prominent than lateral lobes, punctures on frons and vertex rugose, transverse pronotal carina feebly bilobed with lobes broadly developed, punctures on pronotal disc coarser and denser than males.
Variation in male.Dorsum brown, smaller body size, 6.6 mm in length and 5.2 mm in width across humeri, frontal tubercle less developed and not in junction of clypeofrontal suture, pronotal tubercles feebly convex, and number of coarse punctures arranged at pronotal posterior margin variable.
Diagnosis.Bolbelasmus chifengi is morphologically similar to B. concavisuturalis, but can be distinguished from the latter by the coarser and denser primary punctures on the pronotal disc (finer and scattered in B. concavisuturalis), elytral intervals evenly convex (elytral intervals flat with sutural interval concave in B. concavisuturalis) and by the longer parameres (shorter in B. concavisuturalis).
Etymology.Bolbelasmus chifengi sp.nov. is named after Dr Chi-feng Lee, the curator of the Department of Applied Zoology, Taiwan Agriculture Research Institute, Taichung, Taiwan, who kindly provided materials used in this study.2).Body length 10.2 mm; width across humeri 6.3 mm.Dorsum distinctly shiny.Head, pronotum and scutellum reddish brown with elytra brown in color.Head (Fig. 11): labrum with anterior margin crenulate, disc transversally rugose.Clypeus trapezoidal, surface densely rugopunctate; protrusion at basal angle reduced.Clypeofrontal suture well defined, distinctly curved in front of frontal tubercle.Frons with surface sparsely punctate, punctures fine, frontal tubercle vertically located in junction of suture, triangular in lateral view.Eye prominent, canthus simple, not exceeding eye.Thorax: pronotum (Fig. 17) quadrituberculate, tubercles situated in a line, lateral tubercle smaller; anterior face of median tubercles almost perpendicular to surface of pronotum; primary punctures weakly defined, sparse on disc except between lateral margin of pronotum and fovea, these coarser and denser, line in front of scutellum with a coarse puncture, secondary punctures tiny, evenly scattered on surface of pronotum; frontal and lateral margins beaded, posterior margin beaded only anterior to humeri of elytra.Scutellum elongate, secondary punctures sparsely distributed.Elytron (Fig. 23): elytral striae shallowly impressed, punctures mostly spaced 2-3 times diameters of punctures.Intervals flat, with sutural interval weakly concave, surface scattered with secondary punctures.Male genitalia (Figs 29,30,39).
Female paratype (Figs 44,45).Body length 9.8 mm; width across humeri 5.8 mm.Similar to male with minor differences in the form of strongly wrinkled surface of clypeus, transverse frontal carina trilobed, central lobe more prominent than lateral lobes, punctures on frons and vertex rugose, transverse pronotal carina feebly bilobed, lobes broad, punctures on pronotal disc coarser and denser than those of males.
Male paratype.The single male paratype is smaller in body size, 9.4 mm in length and 5.1 mm in width across humeri, frontal tubercle less developed and with three coarse punctures along pronotal posterior margin in front of scutellum.
Diagnosis.Body length, males, 6.8-9.0 mm, greatest width at pronotal base 4.4-5.7 mm; females, 7.1-8.7 mm in length, 4.3-5.6 mm in width (Zinchenko 2016).Bolbelasmus korshunovi is distinguished from the other Oriental Bolbelasmus species by elytral sutural intervals that are moderately convex, primary punctures sparsely distributed either side of the center of the pronotum, and shapes of the parameres.
Notes.Thirteen type specimens were designated in the original description of the species (Zinchenko 2016), 12 of them collected from June to August, and the holotype during November.Accordingly, the temporal activity of adults is likely at least half the year during both rainy and dry seasons.This is identical to the sympatric species, B. meridionalis.
Remarks.Bolbelasmus korshunovi inhabits plains to low-elevational montane areas and occurs sympatrically with B. meridionalis in northern Thailand.
Distribution.Northern India.

Material examined. (11♂♂, 8♀♀
). 1♂ (NSMT).Thailand: Sansai, Chiang Mai, 17. VI. 1993 (1 male at NSMT).9♂♂, 7♀♀ (NSMT); same locality, 12-V-1996.Diagnosis.Body length, males, 6.1-8.2 mm, greatest width at pronotal base, 3.7-5.0mm; females, 5.6-8.2mm in length, 3.3-5.2mm in width.Both B. meridionalis and B. minutus constitute a distinctive group among southeastern Asian congeners based on sharing the distinctly convex elytral sutural intervals and the tips of the parameres acute and curved ventrally in lateral view.Due to a lack of further material being available of the later species, B. meridionalis and B. minutus can only be separated by the shape of male genitalia and the lateral margin of the pronotum in B. meridionalis, which is more widely explanate than that of B. minutus.
Chinese name.脊背厚角金龜 Notes.Li et al. (2008) excluded B. meridionalis from the registered Taiwan fauna due to the lack of verified records.During the present study, we examined a male B. meridionalis specimen housed in NSMT bearing identical labels as the paratype of the species collected in Heito (now Pingtung) by the late Japanese coleopterist, Yushiro Miwa.We therefore confirm the record of B. meridionalis in Taiwan, though it has been lacking in reports of the genus for 90 years.Consequently, the conservation status of B. meridionalis in Taiwan is in urgent need of study, along with that of B. minutus Li & Masumoto, 2008 and Bolbotrypes davidis (Fairmaire, 1891).These species are restricted to habitats in highly urbanized areas and/or intensively farmed plains of Taiwan.
Remarks.Bolbelasmus meridionalis has the widest known distribution among congeners in the region in eastern and southeastern Asia.Also, the records from Java for the holotype and paratypes indicated that it is the only member from the Sunda Islands of the genus.

Distribution. Taiwan.
Remarks.Bolbelasmus minutus was described from a pair of specimens collected during 1931, and no further records of the species have been recorded.This species occurs sympatrically with B. meridionalis and B. nativus in the plains of southern Taiwan.
Remarks.Bolbelasmus nativus was originally described based on a single male from Taiwan.Ochi and Masumoto (2005) treated the population distributed on a few small islands near Taiwan as a subspecies, B. nativus ishigakiensis.
Remarks.Populations of B. shibatai are restricted to a few small islands in the southwestern archipelagos of Japan.Males possess strongly sclerotized parts of the parameres that can be distinguished from the similar species, B. coreanus.
Variation in male.Male paratypes differ from the holotype in the following respects: smaller body size, 6.6 mm in body length and 5.2 mm in width across humeri, frontal tubercle less developed and not in junction of clypeofrontal suture, pronotal tubercle feebly convex, reduced, and number of coarse punctures along pronotal posterior margin variable.
Diagnosis.Bolbelasmus yutangi is similar to B. nativus in sharing the frontal tubercle location at the center of the frons as well as having smaller parameres.It can be distinguished from the latter by the weakly convex basal angle of the clypeus (distinctly bulging in B. nativus), primary punctures densely distributed on the disc (almost impunctate along the middle of disc in B. nativus), sutural interval convex, similar to discal intervals (distinctly more convex than discal intervals in B. nativus) and parameres with the tips tapered (parameres broader at tips in B. nativus).
Etymology.Bolbelasmus yutangi sp.nov. is named after Mr Yu-tang Wang, a beetle enthusiast of Taiwan, who collected most of the material used in this study.(29, 31, 33, 35, 37, dorsal views; 30, 32, 34, 36, 38, ventral   Remarks.Bolbelasmus orientalis was described from one male and one female.Krikken (1977) examined both type specimens and found that the female allotype to be a minor male.Also, he noted that the species has no direct