Taxonomy of the Oriental genus Bolbochromus: a generic overview and descriptions of four new species (Coleoptera: Geotrupidae: Bolboceratinae)

Abstract

A taxonomic overview of the essentially Oriental genus Bolbochromus Boucomont, 1909 is given. Two new southeast Asian subgenera are proposed: Metabolbochromus (type species Scarabaeus sulcicollis Wiedemann, 1819), characterised by unique male genitalia (lacking separated parameres), and Bolbochromops (type species Bolboceras ludekingi Lansberge, 1886), with a distinctly two-horned head (but with separated parameres). The remaining known Bolbochromus, apparently all with a distinct pair of parameres and a distinct frontovertexal protrusion only, are left in the nominotypical subgenus, awaiting a reappraisal of the poorly sampled continental fauna. Four new species are described and compared with close relatives, all in the nominotypical subgenus: Bolbochromus (Bolbochromus) dumogensis (Sulawesi), B. (Bolbochromus) mindanaicus (Philippines), B. (Bolbochromus) pumilus (south India), and B. (Bolbochromus) sinensis (south China). Identity of type species of Bolbochromus to be established (type of Bolboceras laetus Westwood, 1852 not found, and type locality Ceylon doubtful). All named Bolbochromus taxa are listed and characterised (some of them tentatively) in a synoptic table. The southeast Asian island taxa are all keyed and diagnosed, along with notes on variation, range extensions, taxon ranking, and illustrations.

Review of the genus Bolbochromus (Coleoptera, Scarabaeoidea, Geotrupidae, Bolboceratinae) in the Philippines

“…This species is the only representative of the subgenus Metabolbochromus in the Philippines and is also widely distributed from Borneo to Sumatra. Adults are variable in size and the shape of dorsal markings and it was considered by Krikken and Li (2013) that a potential subspecies complex existed. In fact, the pair of specimens collected from Palawan that we treat in this paper have 4 or 5 long, robust setae (Figs 25, 26) on their frons, a feature that has not been observed in other specimens discussed in this paper, which may be due to them having been worn off.…”

“…Bolbochromus Boucomont, 1909 is a group of small to medium-sized (approximately 5.8–13.0 mm body length) bolboceratine beetles which can be distinguished from relatives by having the dorsum shiny, pronotal midline indented, and they are usually bicolored with brownish yellow, reddish brown or dark markings throughout the dorsal surface of the body. The horn-like protrusion on the head and the male genitalia in adults of the genus varies greatly interspecifically and two subgenera, Bolbochromops Krikken & Li, 2013 and Metabolbochromus Krikken & Li, 2013, were erected for the separation of subgroups within the genus (Krikken and Li 2013).…”

“…Unlike other bolboceratine taxa, Bolbochromus species are forest dwellers which have a distribution throughout the Oriental region and a small part of the Palaearctic region in East Asia. The number of the known Bolbochromus species has been increased in the past decade as a result of discoveries of new taxa housed in museums (Krikken and Li 2013), or by the use of improved collecting methods (e.g. flight intercept trap) conducted in Southeast Asia (Hanski and Krikken 1991; Davis 2000; Li et al 2008; Li et al 2013; Krikken and Li 2013).…”

“…The number of the known Bolbochromus species has been increased in the past decade as a result of discoveries of new taxa housed in museums (Krikken and Li 2013), or by the use of improved collecting methods (e.g. flight intercept trap) conducted in Southeast Asia (Hanski and Krikken 1991; Davis 2000; Li et al 2008; Li et al 2013; Krikken and Li 2013). The collecting method of a few recently described species has not been mentioned (Ochi et al 2010; Ochi et al 2011; Keith 2012).…”

“…Bolbochromus is the only bolboceratine genus known in the Philippines and has never been systematically reviewed. In fact, the first species in the genus from the Philippines was not described until 2010 (Ochi et al 2010), and two additional species were named or recorded in 2013 (Krikken and Li 2013). In recent years, a series of Bolbochromus specimens has been collected from selected islands of the Philippines by use of flight intercept traps; these collections constitute the basis of this preliminary review of the Philippine fauna.…”