Hallo: I think this species is Ancistrosoma klugi, but with the next links (to see bellow) you will can study all the Ancistrosoma genus.
On another hand, 15 Ancistrosoma species are known (from Colombia, Ecuador, Peru, Venezuela, Trinidad and Tobago and a single species is recorded from Argentina (Katovich, 2008)) and the most useful work is Arrow (1913), but 4 species are not in his key!.
The type species is Ancistrosoma klugi Curtis, 1835 (by monotypy) and according to Katovich (2008): "The genus is characterized by its large size, elongate body, pronotum with the posterior margin bearing a single, narrow acuminate medial process; mesosternum medially interrupted by a broad triangular extension of the prosternum; 1st abdominal ventrite with posterior margin bearing a narrow, blunt acuminate process medially in males."
And please, you say to me when you downloaded all these papers, because I will delete some of them from the 4shared.
Literature on Ancistrosoma (Macrodactylini):
Ley, R. 1923:
Salle 1886 plates:
Frey G. 1964:
Erichson W.F. 1847:
Latreille 1833- pág: 44.(como Melolontha rufipes):
If do you want? I can send to you the next paper by E-amail: Katovich, K. 2008. A generic-level phylogenetic review of the Macrodactylini (Coleoptera:Scarabaeidae: Melolonthinae). Center for Systematic Entomology, Gainesville, Florida Insecta Mundi. 0023: 1- 78.