Abstract
Hysterionica s.l. (including Neja) comprises ca. 15 species distributed mainly in the grasslands of southern Brazil, Uruguay, central and northern Argentina and Southern Paraguay. Based on field surveys, study of nomenclatural types and other specimens, and review of literature, a new species is proposed here, Hysterionica chamomilloides, endemic of mountainous regions of northern Uruguay, and southwestern Rio Grande do Sul state, Brazil. This work provides a detailed morphological description of the new species, information on its geographic distribution, habitat, phenology, conservation status, and discusses the main differences between H. chamomilloides and the morphologically most similar species. Illustrations, images and a key to the South American species of Hysterionica are also supplied.