A new butterfly species, Dynamine sideria Rosa & Freitas sp. nov. (Nymphalidae: Biblidinae), is described from the Atlantic Forest in Southeastern Brazil. The new species is known from only seven adult specimens and three observation records (two from photographs) in five sites, including a large forest reserve, forest fragments on a disturbed landscape, and a backyard in a dense urban site. Illustrations of adults and male genitalia are provided, as well as a distribution map and limited natural history notes.
Keywords: Butterfly; detectability; new taxon; rare species.
© 2021. Sociedade Entomológica do Brasil.