Onthophagus holosericus

Krikken, J. & Huijbregts, J., 2017, Sulawesi Onthophagus: seven new species in select groups (Coleoptera: Scarabaeidae: Scarabaeinae), Zootaxa 4238 (3), pp. 301-334 : 314-315

The Onthophagus holosericus group

Group diagnosis. Male: Clypeal tip (in major males) with slender, variably long, more-or-less reflexed, narrow projection just behind round or truncate apical edge. Frons with pair of slight (or in males obsolescent) transverse elevations between (anterior part of) eyes. Pronotum with variably shaped forward projection (prong or narrow, well-defined, shorter anteromedian protrusion; species may be polymorphic). Pronotal surface more-or-less sericeous and/or (sub)metallic, changeable (depending on angle of view). Elytra patterned (yellow versus blackbrown, usually marmorate), elytral stria 7 (nearly) straight. Female: Clypeofrontal transition with transverse ridge; frontal paramedian tubercles low, between anterior part of eyes. Pronotum with more-or-less reduced (or modified) antomedian projection, short prong. Protibia more robust.

More group characters: Vertex with (usually slight) transverse elevation. Clypeogenal transition at border uninterrupted. Dorsal foramen of eyes semielliptic. Posterior section of lateral pronotal border sinuate. Pronotal base not particularly modified. Pronotal derm punctate. Scutellum indistinct. Elytra with discal interstriae flat, generally finely, sparsely punctate. Pygidium unmodified, with transverse basal ridge. Antennal club and scapus unmodified. Ridge from procoxa simply running to lateral margin. Metaventrite unmodified. Protibia with 3 or 4 larger, unmodified external denticles, spur simply acuminate; protibial apex unmodified. Parameral shape relatively simple. Mesotibiae and metatibiae and spurs unmodified, elongate-acuminate. Tarsi and claws relatively simple, slender (metatarsomere 1 not distinctly longer than subsequent tarsomeres combined). Body (apart from metallic/sericeous forebody, as indicated above) generally black or brown, with yellow-pigmented elytral pattern variably distinct. Body length usually 4.5–10.0 mm.

Comments. Some species ( Onthophagus holosericus and O. sangirensis ) vary in a number of characters, including: (1) development of protrusion on (and full-face outline of) male clypeal apex and any frontal (paramedian) elevations; (2) development of median protrusion on pronotum in either sex; (3) development of other structural ornamentation on anterior side of pronotum; (3) colouration type and/or pattern of some parts, like forebody (metallic or pigmentary, more-or-less sericeous) and elytra; (4) shape of parameres. As local samples appear constant in some attributes, it may well be that particular morphs represent geographical variation, but with the material at hand no conclusions can be drawn.