Dichotomius globulus (Felsche, 1901)

Valois, Marcely C., Silva, Fernando A. B. & Vaz-de-Mello, Fernando Z., 2022, A taxonomic revision of the globulus species group of Dichotomius Hope, 1838 (Coleoptera: Scarabaeidae: Scarabaeinae), Journal of Natural History 56 (1 - 4), pp. 119-147 : 122-128

Diagnosis of the

globulus species group

The globulus group belongs to the subgenus Dichotomius (Selenocopris) and its species share the following combination of characters: clypeal edge bidentate, clypeogenal junction rounded; ventral clypeal process usually coniform, if bladeshaped then process not bifurcated at apex; inner apical angle of protibia obtuse (>90°); sixth abdominal ventrite of female 2–3 times longer than the fifth; female pygidium without knobs or central emargination ( Nunes and Vaz-de-Mello 2019).

Within Dichotomius (Selenocopris) , species of the globulus group are here considered closely related to the species of the batesi group. All species in these two groups have medium body size (length: 11–14 mm), a single conical process on the head of both sexes, pronotum covered with ocellate punctures, posterior edges of meso and metafemora with a longitudinal groove, apex of paramera weakly sclerotised ( Figure 4 (a–j)) and bent downwards, and the ME at least with a median longitudinal fold ( Figure 5 (b–g)).

However, as defined here, species of the globulus group can be distinguished from the species in the batesi groups by having the following: the pronotum with regular umbilicate ocellate punctures (except for D. femoratus and D. ocellatopunctatus ) (vs irregularly spaced in the batesi group); surface of elytral interstriae dull, entirely shagreened or shagreened along lateral edges ( Figure 3 (g–i)) (the batesi group has the elytral interstriae smooth and finely punctate); anterior and posterior edges of metafemora almost parallel along their lengths (metafemora are slightly club-shaped in the batesi group); posterior edges of meso and metafemora with a thin longitudinal groove along their entire length (while the grooves are usually restricted to the apical half or apical third of metafemora in the batesi group); dorsal surface of paramera usually with a pre-apical longitudinal carina (as in Figure 4 (c), arrows) (while in the batesi group, the paramera have small, laterally directed teeth in the pre-apical region); medial ME slightly longer than wide ( Figure 5 (b–g)), hook-like projections on the inferior part of ME widely separated from each other, not blade-shaped at apex ( Figure 5 (b–g)), and ME with a feeble longitudinal fold restricted to its midline ( Figure 5 (b–g)) (in species of the batesi group, the ME is twice longer than wide, the hook-like projections are close to each other and blade-shaped at the apex, and the lateral edges and the midline of ME are produced into well-developed longitudinal folds along its entire length).

Key to species of the globulus group

1 – Pronotal punctures irregularly spaced, separated by at least their diameter on disc ( Figure 3 (e)) ............................................................................................................................................. 2

1’ – Pronotal punctures umbilicate, equally spaced, separated by less than their diameter on disc (as in Figure 3 (f)).................................................................................................................... 3

2 – Surface of elytral interstriae shinning at centre and shagreened along the lateral portions, near striae ( Figure 3 (h), ShMicro). Clypeofrontal region of both sexes with a central knob. Male pronotum with a distinct anterior declivity at centre ( Figure 1 (c)). Panama and Costa Rica.................... .................... D. femoratus Howden and Young, 1981 .

2’ – Surface of elytral interstriae completely shagreened. Clypeofrontal region of both sexes lacking cephalic process or with a very low central knob (fig. 2(a) in Vaz-de-Mello and Nunes 2016). Male pronotum with a feeble anterior declivity (fig. 2(a) in Vaz-de-Mello and Nunes 2016). Known only from Venezuela................................................. ................................................................................................ D. ocellatopunctatus ( Felsche, 1901) .

3 – Pronotum wider than elytra, brachypterous species ( Figure 1 (a)). Known only from Panama (Santa Fé)................................................. D. benesi Vaz-de-Mello and Nunes, 2016. 3’ – Pronotum as wide as elytra, macropterous species................................................................ 4

4 – Surface of head densely covered with ocellate punctures larger than those on central portion of pronotum ( Figure 3 (c)). Surface of elytral interstriae covered with opaque shagreened microsculpture; medial portion of interstriae with small, smooth dots appearing as pinpricks ( Figure 3 (g)). Ecuador D. fortepunctatus ( Luederwaldt, 1923) .

4’ – Surface of head densely covered with ocellate punctures as large as those on the central portion of pronotum. Surface of elytral interstriae covered with barely shiny shagreened microsculpture; medial portion with dense shiny and smooth dots (as in Figure 3 (i))................................................................................................................................................ 5

5 – Species from Central America ( Figure 6 )..................................................................................... 6

5’ – Species from South America ( Figure 6 )........................................................................................ 9

6 – Clypeofrontal region of male with a central, apically emargined knob. Clypeofrontal region of female with a pair of knobs ( Figure 3 (d)). Dorsal surface of paramera with a pre-apical longitudinal carina as long as half the paramera length ( Figure 4 (i)). Panama.................................................................. D. gamboaensis Howden and Young, 1981 .

6’ – Clypeofrontal region of both sexes with an acute central knob (as in Figure 2 (a,g)). Dorsal surface of paramera smooth or with strong pre-apical teeth (as in Figure 2 (d,p)).............. 7

7 – Male pronotum having a distinct anterior declivity medially ( Figure 2 (m)). Dorsal surface of paramera with strong pre-apical teeth ( Figure 2 (p)). Costa Rica (Puntarenas) ............................................................................................. D. rodrigoi Kohlmann and Solís, 1997 .

7’ – Male pronotum having a feeble anterior declivity medially ( Figure 2 (a,g)). Dorsal surface of paramera smooth ( Figures 2 (d, j))............................................................................. 8

8 – Elytral striae thin and deeply punctate, punctures wider than striae. Costa Rica............ ..................................................................................................... D. favi Kohlmann and Solís, 1997 .

8’ – Elytral striae wide, crenulate, punctures almost as wide as striae. Costa Rica.................. ............................................................................................... D. danieli Kohlmann and Solís, 1997 .

9 – Body elongate ( Figure 1 (b)). Elytral striae thin, punctures wider than striae. Surface of elytral interstriae, in both sexes, covered with barely shiny shagreened microsculpture; medial portion with dense shiny and smooth dots ( Figure 3 (i)). Ventral surface of metafemora with dense coarse punctures concentrated on apical half. Colombia....... .......................................................................................................................... D. berthalutzae sp. nov.

9’ – Body globose ( Figure 2 (s)). Elytral striae almost as wide as their punctures. Surface of elytral interstriae entirely shagreened in males; females with medial portion of elytral striae smooth. Ventral surface of metafemora densely covered with coarse punctures ( Figure 2 (t)). Brazil (Amazonas) and Peru (Iquitos)....... ....... D. globulus ( Felsche, 1901) .

Figures

Figure 1. Dorsal habitus of male. (a) Dichotomius benesi; (b) D. berthalutzae sp. nov.; (c) D. femoratus; (d) D. fortepunctatus; (e) D. gamboaensis.

Figure 2. Holotypes. Dichotomius danieli, male: (a,b) Dorsal and ventral views; (c) labels; (d–f) tegmen in dorsal, ventral and lateral views; D. favi, male: (g,h) dorsal and ventral views; (i) labels; (j–l) tegmen in dorsal, ventral and lateral views. D. rodrigoi, male: (m,n) dorsal and ventral views; (o) labels; (p–r) tegmen in dorsal, ventral view and lateral views. Lectotype D. globulus, male: (s,t) dorsal and ventral views; (u) labels.

Figure 3. Detailed morphology of the species in the globulus group. (a) Ventral view of male, Dichotomius femoratus; (b) ventral view of male, D. gamboaensis; (c) male head, D. fortepunctatus; (d) female head, D. gamboaensis; (e) pronotum of male, D. femoratus; (f) pronotum of male, D. fortepunctatus; (g) elytral striae of male, D. fortepunctatus; (h) elytral striae (Estria) of male (ShMicro, shagreened microsculpture), D. femoratus; (i) elytral striae of male, D. berthalutzae sp. nov.; (j) male abdominal ventrites in ventral view, D. berthalutzae sp. nov.; (k) male abdominal ventrites in ventral view, D. femoratus; (l) female abdominal ventrites in lateral view, D. femoratus.

Figure 4. Tegmen, dorsal and ventral views,respectively. (a,b) Dichotomius benesi; (c,d) D. berthalutzae sp. nov.; (e,f) D. femoratus; (g,h) D. fortepunctatus; (i,j) D. gamboaensis. Scale bar: 500 µm

Figure 5. Endophallites. (a) Dichotomius benesi, endophallus with endophallites, dorsal view. Medial endophallite: (b) D. benesi; (c) D. berthalutzae sp. nov.; (d,e) D. femoratus; (f) D. fortepunctatus; (g) D. gamboaensis. Accessory endophallites: (h) D. benesi; (i) D. berthalutzae sp. nov.; (j) D. femoratus; (k) D. fortepunctatus; (l) D. gamboaensis. Abbreviations: FLP, fronto-lateral peripherical endophallite; A +SA, subaxial and axial endophallites; SRP, superior-right peripheral endophallite.

Figure 6. Known distribution of species of the globulus group.