The chaotic taxonomy of the subfamily Ornithoctoninae Pocock, 1895 is partially addressed, with a focus on redefining the arboreal genera Lampropelma Simon, 1892, Omothymus Thorell, 1891, and Phormingochilus Pocock, 1895. Previous works placing heavy emphasis on unstable taxonomic characters are addressed and stable taxonomic features presented for the clear delineation of males of arboreal ornithoctonine genera. The male of Phormingochilus everetti Pocock, 1895 is described for the first time. A new species, Omothymus rafni sp. nov. is described from historical material collected in Sumatra. Lampropelma violaceopes Abraham, 1924 is transferred to Omothymus based on comparative leg measurements and geographical location comb. nov. Lampropelma nigerrimum arboricola Schmidt & Barensteiner, 2015 is transferred to the genus Phormingochilus with full species status acknowledged, giving the new combination Phormingochilus arboricola comb. nov. Omothymus thorelli Simon, 1901 is considered a junior synonym of Omothymus schioedtei Thorell, 1891 syn. nov., based on similar morphology and geographical locations. Phormingochilus carpenteri Smith & Jacobi, 2015 is transferred to the genus Lampropelma based on comparative leg measurements and geographical location comb. nov. Phormingochilus kirki Smith & Jacobi, 2015 is considered a junior synonym of L. carpenteri syn. nov. Phormingochilus fuchsi Strand, 1906 is transferred to the genus Omothymus based on comparative leg measurement and geographic distribution comb. nov. Phormingochilus tigrinus Pocock, 1895 is removed from synonymy with P. everetti based on the lack of justification for the synonymy comb. rest. Omothymus dromeus Chamberlin, 1917 is removed from Omothymus and returned to the restored genus Melognathus comb. rest.