Five neotropical wasp-mimicking species of the genus Aganacris—two known only from females and three from males—are reviewed. Based on observation of interspecific interactions and morphological comparison, it is shown that sexual dimorphism occurs within species, and that female species are conspecific with sympatric male species. This is reinforced by field observations in northern Peru of a pairing between A. pseudosphex and A. nitida, wherein the male was in the process of secreting a spermatophore. Aganacris sphex and A. pseudosphex are morphologically nearly identical and probably represent variants of a single species. Since those species known from females only are both senior to sympatric male species, the number of species is reduced from five to two — A. nitida (A. pseudosphex and A. sphex designated herein as junior synonyms) and A. velutina (A. insectivora designated herein as a junior synonym).