The type species of Costarina, C. plena (O. P.-Cambridge), is redescribed, has an unusually broad distribution (extending from southern Mexico to northern Costa Rica), and is sometimes sympatric with a relatively widespread new sibling species, C. subplena. The same region also houses 26 additional new species with much smaller distribution ranges: C. iviei, C. llama, C. oaxaca, C. mixtepec, C. naja, C. sepultura, and C. bochil from southern Mexico, C. belmopan, C. peten, C. macha, C. cahui, C. morales, and C. izabal from Belize and Guatemala, C. cortes, C. cofradia, C. cusuco, C. tela, C. ceiba, C. branstetteri, C. olancho, C. muralla, C. coma, and C. gracias from Honduras, and C. waspuk, C. musun, and C. blanco from Nicaragua. At least 11 of these highly localized, microdistributed species have been taken in sympatry with C. plena. Because C. plena and C. subplena are the only members of the genus that have been collected in western and southern Guatemala, we suspect that this area represents the original range of one or both of the widespread species. However, five pairs of the microdistributed species have also been taken in sympatry with each other (and in one case together with C. plena as well).