Onthophagus seseba

Krikken, J. & Huijbregts, J., 2017, Sulawesi Onthophagus: seven new species in select groups (Coleoptera: Scarabaeidae: Scarabaeinae), Zootaxa 4238 (3), pp. 301-334 : 325

The Onthophagus seseba group

Group diagnosis. Male: Clypeal apex round(-truncate) or weakly reflexed-lobate, lateral clypeogenal border evenly round or nearly so, uninterrupted. Clypeofrontal transition at most with slight arcuate ridge between clypeogenal sutures on either side; vertex at most slightly raised (may have obsolescent transverse ridge); no frontal protusion(s) present. Dorsal side punctate-setose (setae relatively short, may be reduced to stubbles, but not claviform). Pronotum at most slightly bulbous in front, lateral edges widely round or straight from anterolateral angle (which is rectangular or nearly so) to obtuse posterolateral angle, feebly sinuate in front of this angle. Protibia with 3+(1) external denticles. Parameres laterally with slight (more-or-less dentiform) protrusion; paramere apex tapering, slender, unmodified. Female: Usually only gradually different from male (proportions of protibia, abdominal ventrites, microsculptural features, etc.).

More group characters: Clypeal apex in both sexes not dentate (full-face view), clypeal surface behind border unmodified (without protrusions). Clypeofrontal transition at most with slight transverse ridge. Frons with transverse ridge. Dorsal foramen of eyes narrow. Posterior section of lateral pronotal border slightly sinuate. Pronotal base not particularly modified. Pronotal derm punctate-setose. Scutellum indistinct. Elytra with discal interstriae flat, generally punctate-setose. Pygidium unmodified, with transverse basal ridge. Antennal club and scapus unmodified. Ridge from procoxa extending to anterolateral margin. Metaventrite largely unmodified. Protibia with 3+(1) unmodified external denticles (proximal denticle small but not disappearing in proximal serration); spur simply acuminate, protibial apex unmodified. Mesotibiae and metatibiae and spurs unmodified. Tarsi and claws simple (metatarsomere 1 about as long as subsequent tarsomeres combined). Dorsal colour usually black or partly (rufous or yellowish) brown, pigmented, any pattern symmetric. Body length usually 3–5 mm.

Comments. These small Onthophagus lack any “sophisticated” external morphological attributes (like diagnostic male forebody elevations), and we initially considered them all “ungrouped”, certainly within the Sulawesi context. Nevertheless, they can be defined as an operational group (note the lateral parameral denticle) and each species is (apart from variable colouration) quite uniform and recognizable in the samples before us; consequently, we have joined them in this O. seseba group of Sulawesi Onthophagus , and composed a tentative key to the species. These species could in Boucomont (1914) key to his O. variolaris group; in more recent synopses they might be placed in the subgenus Indachorius Balthasar, 1941 , but both the head shape (including any surface ornamentation) and the protibial dentation (always just three protibial denticles distinct in Indachorius ) do not fit—note: proximal denticle may be worn away in some specimens (see Onthophagus sembeli Krikken & Huijbregts, 2008 for a “genuine” Sulawesi Indachorius ).

Key to species (males)

1. Dorsal side largely matt, with nothing in the way of metallic reflection, derm microreticulate between numerous punctures or asperities (or other microsculptural elements); elytra may be patterned (for instance, rufous along base). Pronotal punctation on disc superficial and annulate, or simple and minute. Clypeus anteromedially round-truncate, not reflexed................2

- Dorsal side largely black, generally shiny (occasionally submetallic) between numerous distinct, simple punctures (elytral interstriae not asperate or granulate). Elytra unicolour black (narrow margins may be brown). Male with anteromedian section of clypeal margin distinctly but weakly reflexed....................... O. hollowayi Krikken & Huijbregts , new species

2. Pronotum minutely, less densely annulate-punctate (mainly separated by at least one punctural diameter); elytral interstrial surface evenly flat, with rows of short, pale setae set in feebly granuloid micropunctures. Basal surface of elytra with extensive symmetrical, well-defined, reddish-orange markings...................... O. seseba Krikken & Huijbregts , new species

- Pronotum distinctly, densely annulate-punctate; elytral interstrial surface distinctly uneven, asperate-setose (setae distinct). Dorsal side entirely black or dark-brown, but at least elytral base in some populations rufous (i.e., similar to seseba )................................................................ O. annulopunctatus Krikken & Huijbregts , new species