Based on an analysis of the original and subsequent descriptions of Culex (Melanoconion) portesi, Senevet and Abonnenc, 1941 and Cx. (Mel.) cayennensis Floch and Abonnenc, 1945, study of topotypic material and reexamination of male paratypes of cayennensis, the following actions are taken to stabilize the nomenclature: (1) synonymy of cayennensis with portesi, and (2) description of all known stages of portesi. The taxonomic references, including current synonymy are given. The male genitalia and hitherto unknown pupa and larva from Cayenne (type-locality), French Guiana, are illustrated. Literature on bionomics and medical importance is summarized.