Dichotomius agenor (Harold, 1869)

Montoya-Molina, Santiago & Vaz-De, Fernando Z., 2021, Taxonomic review of the Dichotomius (Luederwaldtinia) agenor species group (Coleoptera: Scarabaeidae: Scarabaeinae), European Journal of Taxonomy 734, pp. 1-64 : 7-8

Identification key to the species of the Dichotomius agenor species group based on male characters

1. Dorsally shining coppery, sometimes with green reflections. Large males with cephalic carina narrow, wider than high ( Brazil, Trinidad and Guyana).. Dichotomius subaeneus ( Castelnau, 1840)

– Dorsally black, brown or dull dark blue, or if metallic green then size less than 15 mm. Large males with cephalic carina conspicuous ...................................................................................................... 2

2. Dorsally shining green except for the elytra which are opaque. Cephalic carina undeveloped, narrow. (Anterior edge of the metasternum rugose.) Sixth abdominal sternite and pygidium lower, more depressed than the other sternites. Body length less than 15 mm. ( Brazil: Mato Grosso)............................................................................................ Dichotomius rafanunezi sp. nov.

– Dorsally generally black or at most dull dark blue. Cephalic carina well developed, conspicuous. Sixth abdominal and pygidium as high as the other sternites. Body length greater than 15 mm, except for D. fornicatus (dark blue) .................................................................................................. 3

3. Pronotum surface subrugose. Elytral striae crenulate ( Costa Rica, Guatemala and Nicaragua)......... .................................................................................................................. D. centralis ( Harold, 1869)

– Pronotum with punctures, never rugose. Elytral striae not crenulate................................................ 4

4. Metasternum lateral edges smooth, except for minute setae arising from the centre of each ocellate puncture. Cephalic carina antero-posteriorly flattened, medial tubercle acute distally, never apically expanded or emarginate medially. Pronotum gibbous, smooth and shiny. Body pilosity spare or absent. ( Colombia)......................................................................................... D. belus ( Harold, 1880)

– Metasternum lateral edges usually covered by long/large setae, if smooth then body length less than 15 mm. Cephalic carina not flattened, medial tubercle not acute distally and in some species apically emarginate. Pronotum with small knob, with well-defined punctures. Body pilosity dense............. 5

5. Ventral clypeal process cordate, truncate or bifurcate ....................................................................... 6

– Ventral clypeal process cylindrical, never cordate, truncate or bifurcate .......................................... 7

6. Metasternum with dense pilosity that conceals the metepisternal suture.......................................... 8

– Metasternum without dense pilosity, metepisternal suture clearly visible .......................................11

7. Cephalic carina distinctly arcuate in dorsal view. Pronotum with abrupt anterior declivity when viewed laterally, middle surface deeper than lateral, displaying two well-developed lobes on the anteromedial edge. (Interocular space with scattered simple punctures.) Dark blue to black. Body length less than 15 mm. ( Argentina, Bolivia and Paraguay)........ D. fornicatus ( Luederwaldt, 1931)

– Cephalic carina transverse. Pronotum with smooth declivity, not modified anteriorly. Dense ocellate punctures covering the surface next to the eyes. Black to dark brown. Body length greater than 15 mm. ( Venezuela)...................................................................... Dichotomius henripittieri sp. nov.

8. Cephalic carina antero-posteriorly flattened, trituberculate, inclined anteriorly, apically expanded and emarginate medially. Anterior edge of the declivity medial area deeper and more convex than lateral ones ( Colombia and Venezuela) .................................................... D. deyrollei ( Harold, 1869)

– Cephalic carina conical, not antero-posteriorly flattened neither inclined anteriorly. Anterior edge of the pronotum modified, not convex, displaying undeveloped lobes ................................................. 9

9. Pronotum with three undeveloped lobes on the anterior edge. Cephalic carina with lateral tubercles indistinct, medial tubercle with an acute apex, never emarginate.(Clypeus with a tooth or protuberance before the clypeogenal junction.) ( Colombia and Venezuela) ............. D. inachoides ( Felsche, 1901)

– Pronotum with two underdeveloped lobes on the anterior edge. Cephalic carina with defined lateral tubercles, medial tubercle emarginate at apex ................................................................................. 10

10. Clypeus not rounded. Head with anterior third surface subrugose. Pronotum as wide as the elytra, surface smooth, with ocellate punctation on the posterior margin. ( Venezuela)................................. .................................................................................................. D. validipilosus ( Luederwaldt, 1931)

– Clypeus rounded. Head anterior third transversally rugose. Pronotum wider than the elytra, posterior margin without ocellate punctation, punctation sparse if present. ( Peru)............................................ ................................................................................................ D. simplicicornis ( Luederwaldt, 1935)

11. Setigerous punctures of the medial and lateral edges of the metasternum connected via the inner mesocoxal margins ( Fig. 2G ). Pronotal anterior declivity with a medial subemargination ............ 12

– Setigerous punctures of the medial and lateral edges of the metasternum not connected via the inner mesocoxal margins ( Fig. 2H ). Pronotal anterior declivity without medial subemargination.......... 14

12. Male median tubercle of the cephalic carina thick, cylindrical and with a pronounced apical emargination. Metacoxae posterior edge bearing row of organized, shallow ocellate setigerous punctures which merge together ( Fig. 4H ) ( Mexico) ........................... D. amplicollis ( Harold, 1869)

– Male median tubercle of the cephalic carina not cylindrical, apex feebly emarginate or rounded. Metacoxae posterior edge bearing row of organized, ocellate setigerous punctures not merging together ( Figs 11E and 12E ) ............................................................................................................ 13

13. Interocular space smooth with fine rounded punctures. Male median tubercle of the cephalic carina not emarginate apically ( Fig. 11D ). Pronotum surface covered by fine punctures, margins with row of dense interrupted ocellate punctures. Female pronotum surface smooth with fine punctures ( Mexico) ................................................................................. D. sagittarius ( Harold, 1869) stat. rev.

– Interocular space covered by shagreened microsculpture and flat punctation. Male median tubercle of the cephalic carina feebly emarginate apically. Pronotum surface covered by well-impressed simple punctures, margins with row of dense uninterrupted ocellate punctures. Female pronotum covered with dense and deeply impressed punctures ( Costa Rica, Guatemala and Mexico).. D. enioi sp. nov.

14. Median tubercle of the cephalic carina apically emarginate. Lateral margin of the hypomera with multiple rows of setae ( Fig. 2E ). Metacoxa with more than one row of punctures on the posterior margin ( Colombia, Panamá and Venezuela)............................................... D. agenor ( Harold, 1869)

– Median tubercle of the cephalic carina not apically emarginate. Lateral margin of the hypomera with single row of setae. Metacoxa with single row of punctures on the posterior margin .................... 15

15. Dorsal and ventral surface black. Clypeus with weak central emargination. Anterior portion of the pronotum with a strong, abrupt declivity. Median tubercle of the cephalic carina approximately two and a half times as high as lateral tubercles. Punctures of the lateral edges of the metasternum separated by three times the puncture diameter ( Fig. 2 ). ( Colombia and Venezuela)......................... .............................................................................................................. D. tristis ( Luederwaldt, 1923)

– Dorsal and ventral surface dark brown. Clypeus with deep central emargination separating two obtuse teeth. Median tubercle of the cephalic carina twice as high as lateral tubercles. Punctures of the lateral edges of the metasternum separated by one puncture diameter ( Trinidad) ...................................................................................... D. triquetrus ( Luederwaldt, 1923)

Figures

Fig. 2. General characters that help differentiate the species of the Dichotomius (Luederwaldtinia) agenor species group. A–D. Ventral clypeal process. A. Cordate as in D. agenor (Harold, 1869). B. Truncate as in D. sagittarius (Harold, 1869) stat. rev. C. Bifurcate as in D. belus (Harold, 1880). D. Cylindrical as in D. henripittieri sp. nov. E–F. Hypomeral characters. E. Medial disc smooth, lateral margin with multiple rows of setae as in D. amplicollis (Harold, 1869). F. Medial disc punctate, lateral margin with single row of setae as in D. tristis (Luederwaldt, 1923). G–H. Metasternum characters. G. Setigerous punctures from the medial and lateral edges joining throughout the margin of the mesocaxa as in D. enioi sp. nov. H. Setigerous punctures from the medial and lateral edges not joining throughout the margin of the mesocaxa as in D. centralis (Harold, 1869). I–J. Elytra interstriae. I. Smooth as in D. amplicollis. J. Shagreened as in D. agenor.

Fig. 4. Dichotomius amplicollis (Harold, 1869). A–B. Dorsal habitus. A. ♂. B. ♀. C. Lateral view of the aedeagus. D. Anterior view of the cephalic carina, the central tubercle cylindrical and apically emarginate.E. Ventral view of the aedeagus. F–G. Lamella copulatrix. H. Ventral view of the metacoxa, displaying a single row of organized ocellate setigerous punctures which merge together on the posterior margin.

Fig. 11. Dichotomius inachoides (Felsche, 1901). A–B. Dorsal habitus. A. ♂. B. ♀. C. Frontal view of the head showing the male cephalic carina. D. Sternites smooth, lacking ocellate punctation. E. Female antero-lateral edge of the pronotum rugose. F. Lateral view of the aedeagus. G. Ventral view of the aedeagus. H–I. Lamella copulatrix.

Fig. 12. Dichotomius rafanunezi sp. nov. A–B. Dorsal habitus.A. Holotype, ♂ (CEMT). B. ♀. C. Lateral view of the aedeagus. D. Frontal view of the head. E. Dorsal view of the aedeagus. F–G. Lamella copulatrix. H. Ventral view of the metasternum; antero-medial edge near the interior margin of the mesocoxa rugose.