Tijdschrift voor Entomologie 156 (2013) 35–56 brill.com/tve Oriental Bolboceras: Introduction to the genus and taxonomy of the nigricans group of species (Coleoptera: Geotrupidae: Bolboceratinae) J. Krikken The taxonomy of the genus Bolboceras Kirby, 1819 (= Indobolbus Nikolajev, 1979) is discussed. The Oriental members of the genus as currently conceived have not been revised for the past 160 years. Operational groups of species are proposed, including the Bolboceras nigricans group. In this group B. nigricans Westwood, 1848 and five new Oriental group members are here keyed, diagnosed, and illustrated. The new species proposed are: Bolboceras schulzei (Bangladesh, India), B. malabaricum (India), B. extraneum (Bangladesh, India, Pakistan), B. insulare (Sri Lanka), and B. mimicans (Myanmar). In an Appendix a single new species is described in the Bolboceras perpunctatum group, to consolidate the key to the Bolboceras species groups – B. perpunctatum (India). A list of names of all Bolboceras species is given, indicating a formal retransfer of some from Indobolbus to Bolboceras, following a 2006 ruling of the ICZN on the use of the name Bolboceras. Keywords: Coleoptera, Geotrupidae, Bolboceras, genus description, nigricans species group, keys, list of species, recombinations, new species, Oriental Region. J. Krikken, Naturalis Biodiversity Center/National Museum of Natural History, PO Box 9517, NL-2300 RA Leiden, The Netherlands. [email protected] Introduction head, pronotum, and of male genitalia, indispensable Bolboceras Kirby, 1819 (= Indobolbus Nikolajev, for species identification, are absent or insufficiently 1979) is one of the genera of Bolboceratinae (“bol- detailed. The original material of some of the Bol- bos”, subcosmopolitan subfamily, with ca 600 species boceras species described by Westwood (1848, 1852) in ca 50 genera) still lacking a modern treatment. was not recovered, while both Westwood himself and For the past 160 years hardly anything has been his contemporaries omitted, overlooked, or mixed added to our knowledge of the Oriental fauna of up some available names; their pictures and descrip- this genus as conceived since the ICZN (2006) rul- tions can hardly be qualified as taxonomically use- ing. I looked at Bolboceras (as currently conceived) ful by today’s standards. The identities of some ap- long ago, and, when recently deciding on another at- parently non-congeneric 19th century species-group tempt at clarifying the taxonomy of the genus, I ex- names combined with the name Bolboceras need clar- perienced again that this is, and will remain, a tax- ification. All in all, ca 30 genuine named and un- onomically resistant group. Several species are virtu- named Bolboceras species, mainly Oriental, are now ally unidentifiable without access to both types and known to me, but the actual number may be higher, informative series (i.e. adequately representing in- particularly among the relatives close to B. quadri- traspecific variation and, where applicable, sexual di- dens (Fabricius, 1781) and B. transversale Westwood, morphism). In publications comparative pictures of 1848. Tijdschrift voor Entomologie 156: 35–56. [ISSN 0040-7496]. brill.com/tve © Nederlandse Entomologische Vereniging. Published by Koninklijke Brill NV, Leiden. Published 15 July 2013. DOI 10.1163/22119434-00002018 Downloaded from Brill.com10/08/2021 04:54:17PM via free access 36 Tijdschrift voor Entomologie, volume 156, 2013 As implied above, in spite of these drawbacks, I am may well have evolved in the subcontinent, in a way not throwing in the towel yet. Some handle on the similar to what has been hypothesized for their rel- taxonomy of Oriental Bolboceras is needed, because atives in Bolbohamatum Krikken, 1980 and other at this moment nothing meaningful can be done for reputedly ancient, Gondwana-based scarab groups the evident lack of verified species names and associ- (the out-of-India hypothesis of some authors, e.g., ated diagnostic information. As a first contribution, Davis in Scholtz et al. 2009). Contrary to Bolbo- therefore, the genus is here defined, provisionally hamatum (13 species in South Asia), which has one subdivided into operational clusters of species, and derived polytypic species ranging from Myanmar to six Oriental species (B. nigricans Westwood, 1848 Java and China, species of Bolboceras have not (yet) plus five new relatives) are keyed and diagnosed in been recorded from regions East and North of Myan- what is called the nigricans group. The species in this mar. There is one record of Bolboceras from the An- group are characterized by K- or X-patterned peri- daman Islands (Chandra 1996). The presence of marginal clypeal ridges culminating in a single an- congeners and other closely related bolbos in sub- teromedian point (Figs 27–32), as opposed to the Saharan Africa (Bolboceratops Krikken, 1978, Bolbaf- roughly trapeziform clypeal surface seen in the bulk froides Nikolajev, 1979, etc., cf. Krikken 1984), and of Bolboceras, and in larger collections usually stand- the absence of bolbos from Madagascar, may indi- ing under B. quadridens as an evidently mixed lot cate that there is more to their historical biogeogra- (see also key to groups of species below, couplets phy than a simple Gondwana-India explanation (cf. 3 and 4). Although the known morphological di- also discussion of Bolboceratops in Carpaneto et al. versity in the nigricans group is adequately repre- 1993). sented in this paper, the taxonomic conclusions can- All these genera seem to evade extensive areas of not yet be final for all taxa, the trivial reason being close multistratal evergreen forest; some of the Bol- that more material is needed. There are in Bolboceras boceras at hand are from upland regions, like the questionable cases of compound polymorphism (ge- higher Himalayan valleys (elevations over 1500 m, cf. ographic + individual [size-related] + sexual, etc.), new species in Appendix, below). The precise role of which cannot be solved without sufficiently infor- Bolboceras in their preferred ecosystems is unknown, mative series, particularly from a larger number of only few significant label data being available. In localities than is currently the case. Local hybridiza- plain savanna in East Africa I collected small series of tion cannot be excluded – I was, for instance, puzzled two Bolboceras species and numerous other bolbos at by the variation in a collection of small forms (cf. B. light, during the rainy season. They all buzz around extraneum sp.n.) from Pusa (Bihar, India) and other the lamp at an audibly higher pitch than do the non- northeastern localities. The application of molecular bolbos among incoming medium-sized scarabs, their techniques could perhaps clarify these puzzles in the arrival thus being announced immediately. Our col- not too distant future. leagues in Asia, particularly India, might be inter- A premise in the intrageneric group distinctions is ested to find out the details of their habits, as noth- that polymorphism in the basic shape of both clypeus ing of substance is known. Bolboceras, like all family and pronotum is indeed limited, but, as experienced members, are certainly ardent soil tunnellers, but in other bolboceratine genera, exceptions cannot be what exactly they feed and breed on (fungi? vegetable ruled out (cf. apparent sexual dimorphism in B. in- debris, humus? dung, in combination with fungi?), sulare sp.n.). Note that members of certain other ge- and how they do this, is still a mystery (similar to nera, i.e. outside the Oriental Region, may have X- what is known of certain North American and Aus- shaped clypeal ridges and/or an anteromedian clypeal tralian bolbos? – cf. papers by Howden et al. between protrusion similar to those seen in the B. nigricans 1955 en 2007, Houston & Bougher 2010, Houston group, but none of these has the full set of other 2012). Remember always to collect and safely store generic features described below. Following this ac- voucher specimens while doing ecological work, else count of the nigricans group, work on other groups naming the species concerned will be virtually im- in Bolboceras and other bolbos is envisaged (see also possible and less progress will be made. Krikken 2011). Apart from the five or six named species recorded Discussion of generic delimitation, from the Palaearctic and Afrotropical Regions, the nomenclature, and position genus Bolboceras, in the sense of the 2006 ruling of Members of the genus Bolboceras Kirby, 1819, the ICZN (Opinion 2138), appears essentially Ori- judged from hundreds of specimens seen, are eas- ental, the majority of the species known to me living ily distinguished from other Oriental bolbos by the in the Indian subcontinent – this then is the geo- combination of the following morphological charac- graphic focus of the present treatment. The genus ters: Downloaded from Brill.com10/08/2021 04:54:17PM via free access Krikken: The Bolboceras nigricans group 37 (1) basic outline of clypeus and its perimarginal ica (and these were during most of the past 60 years ridges usually subtrapeziform (modified in combined with Bolboceras), one is in Europe. the nigricans group); During the past decade it has been argued that (2) shape of eye canthi laterally rounded, with bolbos should be placed in a family of their own variably developed anterior protrusion (or (Bolboceratidae, cf. Scholtz & Grebennikov 2006 angle); and included references). I take, with others, like (3) presence of long transverse interocular ridge; Verdú et al. (2004)