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.