Digitonthophagus Balthasar, 1959

Génier, François & Moretto, Philippe, 2017, Digitonthophagus Balthasar, 1959: taxonomy, systematics, and morphological phylogeny of the genus revealing an African species complex (Coleoptera: Scarabaeidae: Scarabaeinae), Zootaxa 4248 (1), pp. 1-110 : 14-15

Digitonthophagus Balthasar, 1959

Digitonthophagus Balthasar, 1959: 464 (original description) Digitonthophagus — Balthasar 1963: 159 (monograph)

Digitonthophagus — Ferreira 1968: 593 (monograph)

Digitonthophagus — Ferreira 1972: 779 (diagnosis)

Digitonthophagus — Kabakov 1979: 94 (diagnosis)

Digitonthophagus — Zunino 1981: 413 (new combination, comment taxonomy) Digitonthophagus — Zunino & Halffter 1988: 17 (comment taxonomy) Digitonthophagus — Ochi 2003: 260 (diagnosis, comment)

Digitonthophagus — Monaghan et al. 2007: 678 (phylogeny) Digitonthophagus — Tarasov & Kabakov 2010: 24 (comment) Digitonthophagus — Tarasov & Solodovnikov 2011: 2 (phylogeny) Digitonthophagus — Génier 2013: 2 (comment taxonomy)

Digitonthophagus — Mlambo et al. 2015: 318 (phylogeny)

Digitonthophagus — Breeschoten et al, 2016: 87 (phylogeny) Digitonthophagus — Roggero et al. 2016a: [1] (phylogeny)

Digitonthophagus — Roggero et al. 2016b: 2 (phylogeny)

Type species. Scarabaeus bonasus Fabricius, 1775 (original designation)

Diagnosis. Externally, the genus Digitonthophagus is almost indistinguishable from the rest of the Onthophagini . However, all Digitonthophagus species have the anterior portion of the hypomeron produced anteriorly and visible from above; therefore, setae that would be located along the anterior edge in ventral portion are moved to a dorsal position. The only other external characters found separating the genus Digitonthophagus and the other closely related genera, is the presence of a distinctly shaped internoapical tooth of the male protibia ( Figs. 7–22 ). This tooth is usually elongate, ventrally flat, and obliquely oriented downward. This character must be combined with females completely lacking this protibial internoapical tooth. In Onthophagus species where a similar tooth is present, the shape of this tooth is spiniform and forwardly directed in males and present in females as well but reduced in size (in African species examined). Internally, the parameres are rather short and the basolateral paramerites always present with the apex of the later adjacent to the lateral portion of the apical carinae. The internal sac of the aedeagus is lacking the lamella copulatrix and associated small sclerites and bristle pads. The frontolateral peripheral sclerite ( Figs. 2–5 ) is located at the apex of the internal sac and a subapicoventral lobe oriented perpendicularly to the main plan of FLP is present.

Description. Size. Small to moderately large (6.5–17.0 mm). Color. Overall color fulvous to light brown with structure edges and sutures more-or-less darker; pronotal disc and head darker and with distinct metallic sheen; elytral margins brown to green, disc with a more-or-less distinct darker irregular macula; metasternum and femoral ventral surface usually with much darker maculae. Head. With a sharply defined clypeofrontal carina in both sexes; antenna with 9 antennomeres, with deep pits on distal surface of antennomeres 7–8. Pronotum. With distinct squamiform granules anteriorly posterior to the anterior declivity that is always simply punctate, granules larger anteriorly and extending more-or-less posteriorly; anterior discal punctures weakly-defined and becoming well-defined posteriorly, when present. Elytra. Juxtasutural interval with strong metallic sheen along sutures; usually with a dark oval macula on the apical declivity on intervals 4–5. Pygidium. Surface with scattered, fine granulate punctures; each puncture with an erect, yellow seta. Ventrites. Hypomeron slightly convex; anterior hypomeral carina well-defined throughout; mesosternum with a bisinuate, glossy surface anteriorly and a more-orless developed longitudinal glossy, keel-shaped structure medially; posterior portion completely rugopunctate and setose; metasternal median lobe usually with a distinct longitudinal ridge behind the anterior suture. Aedeagus. Parameres rather short and basolateral paramerites always present, with the apex of the later adjacent to the lateral portion of the apical carinae. Female genitalia. Infundibulum thin, simple with a median portion reduced; receptaculum seminis elongate, simple, lacking annulate ridges internally (female genitalia characters from Zunino 1981).

Remarks. Balthasar’s (1959) original description was restricted to external morphology and included a number of unrelated species ( O. actaeon Balthasar , O. anguliceps Boucomont , O. avocetta Arrow , O. blumei van Lansberge , O. bonasus Fabricius , O. cameloides d'Orbigny , O. curvicarinatus Boucomont , O. diabolicus Harold , O. digitatus Arrow , O. diversiformis Boucomont , O. fossor Arrow , O. gazella Fabricius , O. kuluensis Bates , O. manipurensis Arrow , O. ohbayashii Nomura , O. ribbei Boucomont , O. rubricollis Hope , O. solivagus Harold , O. troniceki Balthasar , and O. wallacei Harold ). The main characteristic used by Balthasar to define his subgenus was the elongate and thin protibia of the male. This character state is highly homoplasious in Scarabaeinae and evolved many times in the Onthophagini . The subgenus, as originally defined, was clearly paraphyletic ( Zunino 1981).

Remarks for species descriptions and identification key. Diagnoses based on external morphology refer to welldeveloped individuals. As in many scarabaeine species, strong allometric variation in the development of external secondary sexual characters is present. Smallest males will show completely feminized head and thoracic ornamentation, while largest males present two horns on the vertex. Pronotal and elytral granulations and punctation are usually diagnostic but variable, and extremes of one species can be similar to individuals of another species, which makes identification difficult with external characters for some specimens. Examination of the FLP sclerite shape will always provide a definite identification for males. Diagnoses for species groups must be used in conjunction with species diagnoses.

Species are arranged into six groups based on the current phylogeny in order to facilitate comparison of closely-related species. Species are listed in alphabetical order within each group except for the Digitonthophagus bonasus group, where D. uks is treated next to D. bonasus since it is the most closely related species from the same biogeographical region.

Figures

FIGURE 2. Apical portion of internal sac of Digitonthophagus bonasus (membranous portion colored red).

FIGURE 3. Detailed terminology of the frontolateral peripheral and associated sclerites of Digitonthophagus gazella.

FIGURE 4. Detailed terminology of the frontolateral peripheral and associated sclerites of Digitonthophagus gazella, right lateral view.

FIGURE 5. Detailed terminology of the frontolateral peripheral and associated sclerites of Digitonthophagus eucatta, ventral view.

FIGURES 7 – 10. Male dorsal habitus. 7. Digitonthophagus bonasus, alloreferent (Tamil Nadu State, India); 8. D. uks, holotype; 9. D. sahelicus, holotype; 10. D. catta, alloreferent (Tamil Nadu State, India).

FIGURES 11 – 14. Male dorsal habitus. 11. D. eucatta, holotype; 12. D. falciger, holotype; 13. Digitonthophagus biflagellatus, holotype; 14. D. gazella, non type (Central Province, Zambia).

FIGURES 15 – 18. Male dorsal habitus. 15. D. petilus, holotype; 16. D. viridicollis, holotype; 17. D. aksumensis, holotype; 18. D. dilatatus, holotype.

FIGURES 19 – 22. Male dorsal habitus. 19. Digitonthophagus fimator, holotype; 20. D. lusinganus, lectotype; 21. D. ulcerosus, holotype; 22. D. namaquensis, holotype.