Onthophagus pexatus

Reid, Chris A. M. & Runagall-Mcnaull, Aidan, 2022, A Revision of the Onthophagus pexatus Species-group, with Description of a New Brachypterous Species (Coleoptera: Scarabaeidae: Scarabaeinae), Records of the Australian Museum (Rec. Aust. Mus.) 74 (5), pp. 131-150 : 132-133

Onthophagus pexatus species-group

( Matthews, 1972)

Diagnosis. The species-group diagnosis provided by Matthews (1972) is valid for inclusion of the new species, but we have modified this diagnosis slightly to accommodate our observations of all species in the group: ground colour grey or black, sometimes with faint green or bronze sheen; upper surface microsculptured, dull, male head without frontoclypeal or frontal carinae and without horns, sometimes with pair of short transverse ridges on vertex; female with low frontal ridge; eyes narrow, with 3–7 facet rows across widest point, separated by 12–23 eye widths; canthus complete; labium with shallow apical excision much less than half length and middle of base neither membranous nor deeply depressed; pronotum entirely setose, setae short; anterior of pronotum without tubercles or ridges; elytral intervals 1–6 with conspicuous setae; male protibiae usually elongated, with apical setal tuft; apicolateral edge metatibia with mix of short stout setae and long slender setae; tarsomere 5 with short lobe between claws, not longer than base of claws, with a prominent pulvillus; pygidium without ocellate punctures; pygidial disc sparsely setose and sparsely shallowly punctured; abdominal ventrites at most only slightly foreshortened along midline, I–V in combination much longer than VI; length 4–8 mm. All species have a small swelling at the sides of the pronotal disc near the margins.

Notes. This is a small fairly well-defined group created for four described species ( Matthews, 1972): O. longipes Paulian, 1937 ; O. nammuldi Matthews, 1972 ; O. pexatus Harold, 1869 ; and O. squalidus Lea, 1923 . Three undescribed species are known in collections (Monteith & Kenyon, 2011), including the species designated Onthophagus NSW 4, described here. The group is, however, only distinguished from the O. posticus species-group by visible setae on the inner elytral intervals ( Matthews, 1972; Monteith & Storey, 2013). Both groups include males with unsculptured heads, elongated protibiae with apical setal tufts, and major males with a small median swelling on pronotal anterior. Furthermore, both groups include species with male protibial setal tufts either penicilliform or diffuse, and parameres in lateral view either “crested” or elongated (Monteith & Storey, 2013, fig. 7). The two aedeagal groups seem to correspond to species with densely or sparsely punctured pronota ( Matthews, 1972; Monteith & Storey, 2013). However, the Onthophagus species groups delineated by Matthews are informal assemblages ( Matthews, 1972), based on similarity, that function well for practical purposes. We do not intend to change their definitions here, merely noting that each of the O. pexatus - and O. posticus -groups is likely to be nonmonophyletic and intermixed.

All described species of the O. pexatus species-group are found in southeastern Australia, where they occupy the temperate mesic southeastern coastal and montane region defined by Matthews (1972). He noted that there was a sequence of habitat type preferences in the species, from open grasslands ( O. pexatus ), to woodlands ( O. nammuldi and O. squalidus ) to closed forests ( O. longipes ). The new species belongs to the last category. Specimens of the two undescribed species of the O. pexatus species-group, both occurring outside New South Wales, Onthophagus CQ 9 and Onthophagus WA 5 (Monteith & Kenyon, 2011), have not been examined.