Geotrupes (Onthotrupes) lobatus Howden, 1974

Arriaga-Jiménez, Alfonsina, Kohlmann, Bert & Cruz-García, Brenda J., 2020, A predicted new Geotrupes from the mountains of Oaxaca, Mexico, and a description of the male of Geotrupes lobatus (Coleoptera: Geotrupidae), Acta Entomologica Musei Nationalis Pragae 60 (2), pp. 493-508 : 499-500

Geotrupes (Onthotrupes) lobatus Howden, 1974

( Figs 2 , 3 , 4 , 5 )

Geotrupes lobatus Howden, 1974: 573 (original description).

Geotrupes lobatus : HƟඐĐΕΝ (1980): 1960 (key); HƟඐĐΕΝ (2003): 97, 99 (atlas); T*©ƟΤΤΑ-MƟ*©ΕU et al. (2008): 42, 47, 50, 51 (distribution model); KƟΗΓΜΑΝΝ et al. (2018): 21 (key).

Material examined. MEXICO: OΑΧΑർΑ: Sierra Sur. 26- VI.18 CD. 96.244523° W. 16.16096° N. Bosque. 3059 m. Arriaga J.A. Col. (1 ♁, IEXA Entomology Collection, Xalapa, Mexico).

Description. Male ( Fig. 2a ). Body length 13.7 mm. Maximum width 8.3 mm. Color black with distinct greenish-blue cast along margins of head, labium, mandibles, antennal base, pronotum, humeral angles, base of elytral striae, and legs. Antennal club unmodified, grayish-black. Mandible with a large rounded lobe on outer margin just basal to a sharp apical tooth ( Figs 2a and 3b ). Clypeus intermediate between U- and V-shaped, disc closely, contiguously punctate; posterior tubercle low. Vertex largely impunctate, a median sulcus present in anterior half. Ocular canthus broadly arcuate and with a strong greenish-blue cast. Pronotum lacking anterior concavity; posterior marginal line almost absent; disc smooth and impunctate except along anterior and lateral margins, punctures with strong greenish-blue cast. Scutellum impunctate, pentagonal in shape, slightly indented along midline. Elytral striae distinct, first stria terminated by scutellum; striae not crenate or punctate except for outer ten striae which are vaguely punctate. Protibia with seven teeth along outer margin and a row of five small teeth on ventral surface; apical tooth long, slender and spiniform, inwardly curved ( Fig. 2a ); apical spur short, curved, and spiniform; tibiae long and slender forming an arch ( Figs 2a and 3b ). Profemur forming a strong transverse ridge or tooth at its base ( Fig. 3b ). Meso- and metatibia each with three complete transverse carinae on outer surface. Metafemur with a small ventral tooth basally at posterior border. Prosternum with a rounded projection. Mesoventrite excavated and carinate on either side in front of mesocoxae.Aedeagus like Figs 2 c–f.

Taxonomic notes. HƟඐĐΕΝ (1980) indicates in his couplet 8: ‘fore tibiae not distinctly longer than in females’. This is a mistake as the male has distinctly longer and curved protibiae ( Figs 2a and 3b ). It is strange to read this assertion because HƟඐĐΕΝ (1980) did not have any male of G. lobatus for study, only females. Elongate protibiae seem to be more adapted to sexual coupling, as is common in many other scarab beetles, than to digging a nest. The only other Mexican species of Geotrupes that has elongate protibiae is G. onitidipes . Both species share other characteristics such as being black with metallic reflections, having a grayish black antennal club, and pronotum punctate only near margins.

Another similarity between both species is the shape of the aedeagus. In turn, both aedeagi look very similar to the aedeagi of Ceratotrupes , in particular of C. bolivari Halffter & Martínez, 1962 ( Fig. 4a ), probably suggesting some kind of taxonomic relationship or even an evolutionary bridge between both genera.

Distribution and ecology. HƟඐĐΕΝ (1974) described Geotrupes lobatus based on three female specimens that he had collected in the Sierra Sur (Sierra de Miahuatlán) under human feces at 2.450 m. One of us (AAJ) collected the additional specimen during June at a pine forest at 3.050 m a.s.l. ( Fig. 5 ) in the same area, directly under dog dung. However, considering AAJ’s sampling effort in this area (10 pitfall traps every 200 meters in a range from 2.200 to 3.200 m a.s.l.), with a high number of collections for other Geotrupinae species, we presume this is not a strict coprophagous species, possibly a mycetophagous one.

Figures

Fig. 2. Geotrupes lobatus Howden, 1974: a – male dorsal view (16.16096°N, -96.24452°W); b – female dorsal view (16.16096°N, -96.24452°W); c–f – male genitalia: c – in dorsal view, d – in ventral view; e–f – lateral views. Scale bars = 5 mm (a–b), 2 mm (c–f).

Fig. 3. Morphological detail of male protibiae: a – Geotrupes nuntiatus Kohlmann & Arriaga-Jiménez, sp. nov.; b – G. lobatus Howden, 1974; arrow pointing at the apical tooth on the profemur. Scale bar = 2 mm.

Fig. 4. Comparison of male genitalia: a – Ceratotrupes bolivari Halffter & Martínez, 1962; and b – Geotrupes lobatus Howden, 1974. Scale bar = 2 mm.

Fig. 5. Map showing the known distribution of Geotrupes lobatus Howden, 1974, G.sallei Jekel, 1866, and G.nebularum Howden, 1974 (upper map) and the known distribution of G. nuntiatus Kohlmann & Arriaga-Jiménez, sp. nov., G. viridiobscurus Jekel, 1866, and G. pecki Howden, 1974 (lower map).