Bolbochromus (Bolbochromus) pumilus Krikken

Krikken, Jan & Li, Chun-Lin, 2013, Taxonomy of the Oriental genus Bolbochromus: a generic overview and descriptions of four new species (Coleoptera: Geotrupidae: Bolboceratinae), Zootaxa 3731 (4), pp. 495-519 : 513-514

Bolbochromus (Bolbochromus) pumilus Krikken & Li, new species

( Figs. 11–12 , 28–30 , 55)

Material examined. Holotype male (RMNH) from India, labelled “Museum Leiden\ SOUTH INDIA 3500ft \ Anamalai Hills\ Cinchona, XI.1963 \ P Susai Nathan”. The following male and female paratypes:

INDIA: [Tamil Nadu:] Madras, old, 1 specimen in ZSM.—Madras State: Anamalai Hills, v/1970, TR Susai Nathan, 3 specimens, in RMNH. Anamalai Hills: Cinchona, xi/1963, P Susai Nathan, 3500ft, 4 specimens, in RMNH.—Coimbatore, 2 specimens, in MHNG. x/1964, P Susai Nathan, 2 specimens, in USNM. x/1972, 1400ft, 1 specimen, in RMNH. xi/1963, P Susai Nathan, 1400ft, 10 specimens, in RMNH (aedeagus pictured). xi/1972, TR Susai Nathan, 1400m, 1 specimen, in MHNG. xi/1964, P SusaiNathan, 1400ft, 17 specimens, in ZSM. xi/1964, P Susai Nathan, 2 specimens, in CJSB.— Pondicherry: Karikal, viii/1964, P Susai Nathan, 27 specimens, in ZSM.— Total: holotype and 70 paratype specimens.

Identification. The combination of colours and size usually suffice to identify this Indian species. Head black, pronotum and elytra unicolour orange(-brown). Including the smallest Bolbochromus individuals known, body length usually 4.5–6.0 mm. Elytra with 5 distinct, strongly punctate striae, reaching elytral base between scutellum and humeral umbone, and with broader and more strongly convex discal interstriae 1, 3, and 5. Pronotum not with sulcate midline, anterior declivity without antediscal protrusion(s), at most slightly depressed immediately behind apical border. Head with variably developed interocular (sub)conical protrusion; clypeus non-tuberculate. Aedeagus small, with little modified parameres. Its closest known relative, with a similar elytral striation, is presumably B. posticalis from India (distributional details unknown, seen as holotype # 529 in OUMNH), which is much lighter (pale yellow), and has its integument symmetrically infuscated (black) on the discomedian part of the pronotum and on interstria 1 and the broader distal declivity of the elytra; anterior side of pronotum in posticalis abruptly declivous (deplanate) from slight transverse antediscal ridge.

Description (holotype, male). Body length approximately 6 mm. Colour generally orange-brown, dorsum glossy, almost glabrous; head black. Pilosity on underside and legs abundant, long, light brown.

Labrum with vaguely emarginate anteromedian border, upper surface uneven, and with fine ridge paralleling anterior side of clypeus. Clypeal and prefrontal upper surface rugulate-punctate, bordered by fine, widely arcuate perimarginal ridge, Clypeogenal angle non- protuberant. Eye canthus with numerous distinct punctures, generally broad, anterior edge slightly, finely raised, widely, evenly arcuate from clypeogenal angle, tapering to temporal lobe; paraocular ridge (issuing from clypeogenal angle) fine, extending to about halfway eyes; frons with distinct interocular cone, surrounding surface with fine, scattered primary punctures. Eye foramen relatively large.

Pronotum moderately convex, gradually declivous in front, outline of marginate (raised) anterior border evenly arcuate; pronotal midline with sparsely punctate midline from near base to superficially depressed apex; anterolateral angle subrectangular (full-face view), lateral edge posteriorly widely rounded to base. Pronotal surface with scattered, double punctation, primary punctation (size variable) distinct, sparse; smaller punctures lining anterior and lateral marginal ridge; secondary punctation sparse, minute. Pronotal base medially immarginate, but lined with row of small punctures (dorsal outline medially rounded). Scutellum deltoid, with some sparse, indistinct micropunctation.

Elytra with striae 1–5 reaching base between suture and humeral umbone; distinctly impressed and distinctly punctate; punctures usually separated by 2–4 puncture diameters, crenulating interstriae. Elytral interstriae (in cross-section) convex, interstria 2 and 4 less convex than adjacent interstriae; interstrial surface sparsely micropunctate. Punctures in juxtepipleural stria with long seta.

Protibia with 9 external denticles, proximally decreasing in size; apex unmodified, with long, complanate, slightly tapering spur. Outer side of mesotibiae and metatibiae with 2+(2) arcuate anteapical fossorial elevations, their crest fringed with robust, (sub)acuminate spines; apical crest transversely subelliptic, with similar spines; terminal spurs long, apex blunt, slightly curved.

Aedeagus (of paratype), Fig. 55; moderately sclerotised, small, elongate-convex, parameres with rounded tip.

Measurements of respective parts in mm. Median length of head (full-face, excluding labrum and mandibles) 1.15, width 1.70. Median length of pronotum (dorsal) 1.9, maximum width 3.5. Median length of scutellum 0.75, maximum width 0.80. Sutural length of elytra (dorsal) 2.3, maximum width combined 3.7.

Variation and sexual dimorphism. Series present in several collections (stemming from a dealer popular with museums in the 1960s), and apparently constant in their colouration. Body length varies relatively strongly, holotype is one of the largest males. No notable sexual dimorphism.

Distribution. Southern India.

Etymology. Named after its small size (dwarf).

Figures

FIGURES 9 – 16. Habitus of male Bolbochromus (oblique and lateral views). 9 – 10, B. sinensis; 11 – 12, B. pumilus; 13 – 14, B. catenatus; 15 – 16, B. niger. Scale lines 1 mm.

FIGURES 25 – 30. Bolbochromus holotypes, body parts, head (full-face), pronotum (dorsal), left elytron (dorsal). 25 – 27, B. dumogensis; 28 – 30, B. pumilus. Scale lines 1 mm.