Of the American species of Anax characterized by an unmarked frons, A. longipes Hagen (1861) was described from U.S.A. and A. concolor Brauer (1865) from the Amazon in Brazil. But soon after their description HAGEN (1890) was of the opinion that concolor Brauer was only a variety of longipes, in which according to him the odonatologists have taken the same stand. This conception is probably due to the fact that insufficient material of both species is studied. The motive for a reexamination of the two species was a comprehensive material of Anax concolor mostly collected in Suriname and on the Lesser Antilles. Additional specimens of A. longipes from the U.S.A. were received for comparison. The type specimens of both species could be examined but the difficulty was that the types of both species belong to different sexes. New descriptions of the imagines and of the larvae in their last instar are made, with a comparison of the most striking differences between the two species. Beside the morphological points of controversy in both imagines and larvae, there proved to be also a marked difference in their distribution: A. longipes occurs in U.S.A. entering Mexico, the Greater Antilles and Bahamas, while A. concolor occupies tropical South America to the Lesser Antilles and the Bahamas, and Central America. This study has demonstrated that Anax concolor is not a variety of A. longipes, but that both forms belong to different species.