Despite its wide, almost worldwide distribution, the mayfly genus Cloeon Leach, 1815 (Ephemeroptera: Baetidae) is restricted in the Western hemisphere to North America, where a single species is reported. In the Neotropics, except for some species wrongly attributed to the genus in the past, there are no records of Cloeon. Recently, however, specimens of true Cloeon were collected along the coast of Espírito Santo, Southeastern Brazil. In order to verify the hypothesis that this species was recently introduced to Brazil, our aim was to identify the species based on morphological and molecular characters and to confirm the presence of true representatives of the genus in the Neotropics. Our results revealed that the specimens found in Brazil belong to the Afrotropical species C. smaeleni Lestage, 1924. The identity of the species, its distribution, along with its previous absence in regularly sampled sites, is a clear sign that the specimens of C. smaeleni found in Espírito Santo are introduced, well established, and that the colonization took place very recently.

Asthenopus angelae sp. nov. is described based on male and female imagos and associated nymphs from Argentina, Bolivia, Brazil and Colombia. The new species described is similar to A. curtus (Hagen). The nymphal and adult female stages are indistinguishable from those of that species. The male adults can be separated from its congeners by the following characters: penes tubular, with well developed median basal protrusion, curved ventro-medially, with apex acutely projected, furrow separating penial lobe from median basal protrusion reduced or absent; forceps relatively slender; forelegs of male 0.6-0.7 × the length of the forewing; fore tarsal claws slightly widening distally; fore wings with 5-11 marginal intercalary veins relatively short. ResumoAsthenopus angelae sp. nov. é descrita baseada em imagos machos e fêmeas e ninfas associadas provenientes da Argentina, Bolívia, Brasil e Colômbia. A nova espécie é similar a A. curtus (Hagen), as ninfas e os imagos fêmeas são indistinguíveis, mas os machos adultos podem ser diferenciados pela seguinte combinação de características: pênis tubulares, com membrana basal bem desenvolvida, curvados ventro-medialmente, ápice projetado na porção mediana, sulco que separa os lobos penianos da membrana basal reduzido ou ausente; fórceps relativamente esguio; pernas anteriores relativamente longas, medindo 0.6-0.7 × o comprimento das asas anteriores; garras tarsais anteriores levemente alargadas no ápice; asa anterior com 5-11 veias intercalares marginais relativamente curtas.

Cloeodes Traver, 1938 (Ephemeroptera, Baetidae) was established to include Baetidae specimens from Puerto Rico. Of the three species described by Traver (1938), only the type-species C. maculipes remains in this genus (Domínguez et al. 2006). A revision of Cloeodes by Waltz & McCafferty (1987) redefined its distinct characteristics and revealed the genus to be a widespread group of  Neotropical origin with several species from South and Central America as well as from Southwestern North America and Southeast Asia.

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