A synopsis of the genus Ethmia Hubner in Costa Rica: biology, distribution, and description of 22 new species (Lepidoptera, Gelechioidea, Depressariidae, Ethmiinae), with emphasis on the 42 species known from Area de Conservacion Guanacaste

We discuss 45 Costa Rican species of Ethmia Hubner, 1819 including 23 previously described: E. delliella (Fernald), E. bittenella (Busck), E. festiva Busck, E. scythropa Walsingham, E. perpulchra Walsingham, E. terpnota Walsingham, E. elutella Busck, E. janzeni Powell, E. ungulatella Busck, E. exornata (Zeller), E. phylacis Walsingham, E. mnesicosma Meyrick, E. chemsaki Powell, E. baliostola Walsingham, E. duckworthi Powell, E. sandra Powell, E. nigritaenia Powell, E. catapeltica Meyrick, E. lichyi Powell, E. transversella Busck, E. similatella Busck, E. hammella Busck, E. linda Busck, and 22 new species: E. blaineorum, E. millerorum, E. dianemillerae, E. adrianforsythi, E. stephenrumseyi, E. berndkerni, E. dimauraorum, E. billalleni, E. ehakernae, E. helenmillerae, E. johnpringlei, E. laphamorum, E. petersterlingi, E. lesliesaulae, E. turnerorum, E. normgershenzi, E. nicholsonorum, E. hendersonorum, E. randyjonesi, E. randycurtisi, E. miriamschulmanae and E. tilneyorum. We illustrate all species and their male and female genitalia, along with distribution maps of Costa Rican localities. Immature stages are illustrated for 11 species, and food plants are listed when known. Gesneriaceae is added as a new food plant family record for Ethmia. CO1 nucleotide sequences ("DNA barcodes") were obtained for 41 of the species.