Eupatorus siamensis, Laporte, 1867

Prandi, Massimo & Grossi, Paschoal C., 2021, A new species of Eupatorus Burmeister, 1847 related to Eupatorus birmanicus Arrow, 1908 from southwestern China (Coleoptera: Scarabaeidae: Dynastinae), Zootaxa 4966 (1), pp. 29-40 : 39

Eupatorus siamensis species-group

Eupatorus siamensis ( Laporte, 1867) , Eupatorus birmanicus Arrow, 1908 , Eupatorus endoi Nagai, 1999 , and Eupatorus pyros Prandi & Grossi , new species

The present study supports the recognition of the Eupatorus siamensis species-group, which is characterized by the pronotal disc bearing two horns. We do not follow Shimizu’s arrangement (2020) with the use of Alcidosoma as a valid subgenus, but we recognize the need to isolate a group of species within the other Eupatorus . Eupatorus birmanicus and E. siamensis are very similar in the external appearance, mainly in hypotelic males (the bifid male in Arrow’s description for E. birmanicus and the ab. bifidus Endrődi, 1957 for E. siamensis ). Here we illustrate the two major male habitus ( Fig.1B and Fig. 4C ) and the two hypotelic male habitus ( Figs 5D, E ). In E. birmanicus the TL varies from 38 to 70 mm and the area of distribution ranges from Myanmar to Thailand. In E. siamensis the TL varies from 45 to 78 mm and the area of distribution ranges from Myanmar to Vietnam. Also, Eupatorus endoi Nagai, 1999 has a two-horned pronotal disc ( Fig. 4D ) and sometimes displays a bifurcate apex in cephalic horn ( Fig. 5B ). Smaller than the formers (its TL ranges from 33 to 55 mm), it is known from the typical locality of Bao Loc and other localities in southern Vietnam ( Figs 4B, D ).

Figures

FIGURES 1A–D. Habitus of males in dorsal view and detail of thorax in lateral view. A, C, holotype of Eupatorus pyros Prandi & Grossi, new species; B, D, Eupatorus birmanicus Arrow, 1908.

FIGURES 4A–D. Habitus of males in dorsal view and detail of thorax in lateral view.A, C, Eupatorus siamensis Laporte, 1867; B, D, Eupatorus endoi Nagai, 1999.

FIGURES 5A–E. Habitus of males in dorsal view and detail of thorax in anterior view. A, D, Eupatorus birmanicus Arrow, 1908 with bifid horn; B, Eupatorus endoi Nagai, 1999 with bifid horn; C, E, Eupatorus siamensis Laporte, 1867 ab. bifidus sensu Endrődi.