The background and accomplishments of Darwin's work on Catasetinae are analyzed, and issues that he and others did not resolve are discussed in detail. The segments on Catasetinae published by Darwin in the Annals and Magazine of Natural History in September 1869 and in the second edition of his orchid pollination opus (as Catasetidæ) published in 1877, as well as his paper “On the three remarkable sexual forms of Cataseum tridentatum,” all including the text, plates, and notes, are presented in three appendixes.