Onthophagus scrutator

Krikken, J. & Huijbregts, J., 2017, Sulawesi Onthophagus: seven new species in select groups (Coleoptera: Scarabaeidae: Scarabaeinae), Zootaxa 4238 (3), pp. 301-334 : 304

The Onthophagus scrutator group

Group diagnosis. Males: Clypeal apex of male with variably-developed, broad, upright lobe; lateral border of clypeus convergent, straight, or arcuate. Pronotum with broad, blunt, frequently strong anteromedian protuberance (in major males with variably bifid apex), surface of pronotum anterolaterally (on either side of protuberance) more-or-less concave. Protibial tip weakly prolonged, internally angular. Both clypeofrontal and vertexal transverse ridge slight or obsolescent. Females: Head with distinct clypeofrontal and vertexal ridge. Pronotal anteromedian gibbosity reduced. Protibial apex simply oblique.

More group characters: Clypeogenal transition at border (virtually) uninterrupted. Dorsal foramen of eyes narrow. Posterior section of lateral pronotal border slightly sinuate. Pronotal base unmodified. Pronotal derm simply punctate-setose. Scutellum indistinct. Elytra with discal interstriae flat, generally punctate-setose (not asperate). Pygidium unmodified, with transverse basal ridge. Antennal club and scapus unmodified. Metaventrite unmodified. Protibia with 3+(1) unmodified external denticles, spur acuminate. Parameral shape relatively simple, tip curved-tapering. Mesotibiae and metatibiae spurs unmodified. Tarsi and claws simple (metatarsomere 1 about as long as subsequent tarsomeres combined). Dorsal colour usually black or brown, pigmented, at most with vague pattern or submetallic tinge. Body length usually 5–8 mm.

Comments. Onthophagus scrutator was, with various other Oriental-Palaearctic species, placed in the subgenus Gibbonthophagus Balthasar, 1963 . This was apparently due to the pronotal gibbosity, but we see no clear synapomorphy for the subgenus as currently conceived, and no direct relationship with the type species of Gibbonthophagus , O. atripennis Waterhouse, 1875 (from China and Japan).

The two species in the O. scrutator group included species are very similar, and particularly O. scrutator appears widespread on Sulawesi. The differences between the species indicated hereafter (dorsal punctation, microsculpture, and inherent glossiness) appear to be fairly constant. The development of the apicomedian clypeal lobe and the pronotal protrusion may vary strongly, in both size and shape.