ABSTRACT On the basis of external morphology and genitalia of males, as well as a comparison between different species belonging to other groups of Dichotomius, we propose a redefinition of the "buqueti" species group separated by Luederwaldt (1929). Six species are excluded from this group and transferred to other groups: D. ribeiroi (Pereira, 1954) in the "cotopaxi" group; D. camposeabraiMartínez, 1974 in the "bitiensis" group; D. reclinatus (Felsche, 1901), D. horridus (Felsche, 1911), D. quadrinodosus (Felsche, 1901) and D. nimuendaju (Luederwaldt, 1925) (revalidated species) forming the newly defined "reclinatus" group. The other species kept in the "buqueti" group include D. buqueti (Lucas, 1857) from Brazil (lectotype here designated), D. haroldi (Waterhouse, 1891) from Argentina and D. nutans (Harold, 1867) from Brazil, Argentina and Uruguay. The taxonomic revision of the "buqueti" group are presented, including a history of the included species, a determination key, illustrations of the structures of external morphology, male genitalia and sclerites of the internal sac, and a distribution map.

Se realiza la redescripción de Dichotomius ribeiroi (Pereira, 1954), en donde se describe por primera vez a la hembra de esta especie hasta ahora desconocida. Se presentan datos sobre la distribución geográfica de la especie, ilustraciones del habitus, el órgano genital y escleritos del saco interno del macho así como las diferencias en la morfología externa de las hembras. Al realizar la comparación de la morfología externa y el órgano genital masculino de D. ribeiroi con las especies del grupo "cotopaxi", se propone la reubicación de esta especie dentro de este grupo, el cual es redefinido.

The redescription of Dichotomius ribeiroi (Pereira, 1954) is done; in which description the female species, unknown so far, is described at first. Data about geographical distribution, illustrations of male habitus, male genital organ and its sclerites of internal sac, also the differences in the female external morphology are presented. When the comparison between the external morphology and male genital organ of this species with of Dichotomius of group "cotopaxi" is made; a transference of this species to this group can be proposed.

The redescription of Dichotomius camposeabrai Martinez, 1974 and D. nemoricola (Pereira, 1942) is presented, including the description of the female of the first species and the male of the second so far unknown. For each species, illustrations of the male habitus, male genital organ, the sclerites of internal sac and head and pronotum of female are presented. Information about geographical distribution and some comments are available. In addition the transfer of D. camposeabrai to the bitiensis group is proposed and discussed, given the similarities of the external morphology and male genital organ with those of D. nemoricola.

Se presentan redescripciones de Dichotomius camposeabrai Martínez, 1974 y D. nemoricola (Pereira, 1942) que incluyen la descripción de la hembra de la primera especie y del macho de la segunda, hasta ahora desconocidos. Para cada especie se realizaron ilustraciones del habitus del macho, del órgano genital masculino y de los escleritos del saco interno, así como de la cabeza y pronoto de las hembras. Se proporcionan datos sobre la distribución geográfica y algunos comentarios de las especies. Además, se propone y discute la transferencia de D. camposeabrai al grupo bitiensis, dadas las similitudes de la morfología externa y del órgano genital masculino que presenta con D. nemoricola.