Summary
A key, descriptions, and discussion are given for the 52 South American species and subspecies of Esenbeckia (Esenbeckia). Ten of the above are new to science; E. accincta (Ecuador), E. bassleri (Peru), E. cisandeana (Colombia, Peru, ?Chile), E. dressleri (Ecuador), E. erebea (Bolivia), E. laticlava (Ecuador), E. pechumani (Peru), E. perspicua (Brazil), E. wygodzinsky (Peru), and E. xanthoskela (Peru, Ecuador). E. illota which was considered to be the nominate species of a group of forms is separated as distinct while E. osornoi is now considered the nominate species of guianense, meridionale, and planaltina. The 8 species of the ‘lugubris’ group are, in addition, represented in a separate key.