Indonthophagus Kabakov, 2006

Ziani, Stefano, 2024, Historical and morphological review of the subgenus Indonthophagus Kabakov, 2006 of Onthophagus Latreille, 1802 (Coleoptera: Scarabaeidae: Scarabaeinae: Onthophagini), Insecta Mundi 2024 (38), pp. 1-42 : 3-5

Subgenus Indonthophagus Kabakov, 2006

Indonthophagus Kabakov 2006: 154 (footnote); Krajcik 2012: 174; Krajcik 2013: 124; Ziani and Bezděk 2016: 188; Král and Batelka 2017: 131; Montreuil 2017: 269; Gupta et al. 2018: 483; Ziani et al. 2019: 18; Ghosh et al. 2020: 243; Kharel et al. 2020: 368 /371; Gupta et al. 2022: 425; Schoolmeesters 2023; Ziani and Keith 2023: 1.

Type species. Onthophagus mopsus ( Fabricius, 1792) , by original designation.

Diagnosis. Onthophagus species of small or medium size (length 3.0 to 10.0 mm), colour blackish brown, sometimes with green or blue metallic lustre, elytra sometimes with dark red basal and apical spots, in one case elytra yellow ochre with symmetrical v-shaped black spots. Antennae yellow, more or less dark. Setation pale-yellow.

Head short, clypeus broadly round, barely or not at all emarginate anteriorly and not sinuate at sides; antenna with 9 antennomeres; clypeofrontal carina distinct, sometimes barely discernible, bent backward, in major males usually halfway between the base of the horn and the anterior clypeal margin, in one case nearly adjacent to the base of the horn; major males with the occipital carina extended in a long horn arising sometimes between eyes or slightly forward, sometimes in front of them, flat and more or less broad at base, directed backward, following the curvature of pronotum, often extending past the middle of the body; occipital carina reduced to a short tubercle in minor males or to a more or less straight carina, placed between eyes, or nearly so, in females ( Fig. 1a ); clypeal surface with transversely rugose, setigerous punctures, frontal surface sparsely punctate, punctures of two sizes.

Pronotum convex, declivous anteriorly, major males with a more or less appreciable anteromedian groove, with or without a tubercle on each side; minor males and females with an anteromedian transverse gibbosity, sometimes hardly appreciable, sometimes divided in two lobes; both sexes with a posterolateral area, more or less wide and depressed, dull with stronger microreticulation, on either side near pronotal posterior angles (Fig. 2), sometimes anteriorly with a tuft of few longer setae; anterior angles distinctly produced, sides not sinuate behind them; dorsal surface setigerously punctate, punctures more or less slightly impressed, usually subregular in distribution, bearing pale-yellow setae.

Elytral striae usually shiny, distinctly impressed, with punctures slightly larger than strial width and barely crenulating interstrial sides; interstriae flat to convex, all rather regularly densely granulate, granules with a more or less short thin setae.

Pygidium basally ridged, with rather regularly distributed, setigerous punctures; setae pale-yellow, thin, usually longer that those of elytra.

Apical margin of male protibiae either oblique or perpendicular to the inner protibial margin, in the latter case with a tuft of short pale-yellow bristles, always with a small denticle strongly curved downward at the inner angle of protibial apex; metatibiae distinctly widened apically.

Male genital armature. Parameres short, apices usually bent ventrally and diverging apically, without basolateral plate denticle, round at apex; endophallus with the presence of accessory endophallites, one (in O. ensifer ), usually two evident raspulae and a U-shaped lamella copulatrix, with arms more or less slender, sometimes with spinelike processes or apically bifurcate.

Epipharynx ( Fig. 1b ). Rounded laterally, front edge not sinuate; acropariae long, rather densely arranged; epitorma very slender, almost indistinguishable, with some bristles along its length, the distal ones longer and stouter; corypha without spinules; chaetopariae stout; tomae rounded at the end.

Distribution. East Palaearctic, east Afrotropical and west Oriental ecozone ( Schoolmeesters 2023).

Historical review. The first author that somehow grouped most of the species treated in this paper was Boucomont (1914). He drawn up a key to some Onthophagus species with the following characteristics: “tête ♂ avec une ited by G. Fiumi.

corne plus ou moins longue, non lamiforme, thorax ♂ sans saillies ni tubercules latéraux ou discaux, tout au plus avec deux petites dents au sommet; intervalles des élytres à ponctuation râpeuse; insectes concolores sans taches accusées” [head ♂ with a more or less long, not lamiform horn, pronotum without projections or lateral tubercles, at most with two small teeth anteriorly; interstriae with raspish punctation; insects unicoloured, without definite spots]. Five species were placed in this “group”: Onthophagus spinifex ( Fabricius, 1781) , O. ensifer Boucomont, 1914 , O. turbatus Walker, 1858 , O. gracilicornis ( Germar, 1813) [now deemed as junior synonym of O. mopsus , see below] and O. hastifer van Lansberge, 1885 .

Arrow (1931) proposed a “ mopsus group” (Group 25) for O. mopsus , O. turbatus , O. hastifer , O. ensifer and for O. nitidulus Klug, 1845 , together with other seventeen species. It’s worth noting that Arrow (1931) placed the male of Onthophagus spinifex in the Group 13 (marginalis group), whereas the female was placed in the Group 6 (rudis group).

Biswas and Chatterjee (1985), probably referring to Arrow (1931), mentioned a “ mopsus group” without specifying any morphological characteristic.

Again, also Kabakov and Napolov (1999) placed O. hastifer in a vaguely defined “ mopsus group”.

Later on, Kabakov (2006) described the subgenus Indonthophagus for all the species quoted by Boucomont (1914) and adding Onthophagus nitidulus .

The subgenus was then accepted and used by Ziani and Bezděk (2016), Král and Batelka (2017), Montreuil (2017), Gupta et al. (2018), Ziani et al. (2019), Ghosh et al. (2020), Kharel et al. (2020), Gupta et al. (2022) and Schoolmeesters (2023), even though none of them dealt with Indonthophagus more in depth.

Phonetic remarks. As explained some years ago ( Ziani 2020a), Indonthophagus , having Onthophagus as suffix, is a proparoxytone word, that is, it has a heavy stress on the third-to-last syllable. It has to be pronounced Indontòfagus.

Biology. All the species cited in this paper should be strictly coprophagous. To confirm that, Mittal (1986) reported O. mopsus and O. spinifex attracted by human dung and Mittal (1999) by cattle and horse dung. Thomas et al. (2006) recorded O. ensifer in a trap baited with Indian elephant dung. Again, O. ensifer with O. turbatus have been recorded in gaur dung from Southern Western Ghats ( India) by Thomas et al. (2007). According to Asha et al. (2022), this last two species ( O. ensifer and O. turbatus ) are specialists of non-ruminant dung, such as elephant and wild boar. And always regarding O. ensifer and O. turbatus, Sathiandran et al. (2021) specified that, in southern India, the two species attend dung of deer, elephant, gaur and especially boar, whereas only O. turbatus has been collected in macaque dung. For what I know, other eating preferences have never been reported. Taiwanese specimens of O. hastifer were collected in buffalo dung deposited in open pastures (D. Král, personal communication). In Western Ghats ( India), O. turbatus seems to be abundant both in open and in shaded areas, with both day and night activity, whereas O. spinifex is a nocturnal species present in open areas ( Asha et al. 2021). Three species at least ( O. turbatus , O. mopsus and O. spinifex ) present positive phototaxis, and were collected at light in Pakistan (unpublished data).

Figures

Figure 1. Onthophagus (Indonthophagus) mopsus (Fabricius, Figure 2. Onthophagus (Indonthophagus) turbatus Walker, 1792) [Pakistan, Islamabad Capital Territory]. 1a) ♀ head, 1858 [Sri Lanka, Uva prov.]. Detail of pronotal posterolateral from above. 1b) Epipharynx. Photos by A. Degiovanni, ed- area. Photos by A. Degiovanni, edited by G. Fiumi.