The chaotic taxonomy of the subfamily Ornithoctoninae Pocock, 1895 is partially addressed, with a focus on redefining the arboreal genera LampropelmaSimon, 1892, OmothymusThorell, 1891, and PhormingochilusPocock, 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 everettiPocock, 1895 is described for the first time. A new species, Omothymus rafnisp. nov. is described from historical material collected in Sumatra. Lampropelma violaceopesAbraham, 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 arboricolacomb. nov.Omothymus thorelliSimon, 1901 is considered a junior synonym of Omothymus schioedteiThorell, 1891syn. nov., based on similar morphology and geographical locations. Phormingochilus carpenteriSmith & Jacobi, 2015 is transferred to the genus Lampropelma based on comparative leg measurements and geographical location comb. nov.Phormingochilus kirkiSmith & Jacobi, 2015 is considered a junior synonym of L. carpenterisyn. nov.Phormingochilus fuchsiStrand, 1906 is transferred to the genus Omothymus based on comparative leg measurement and geographic distribution comb. nov.Phormingochilus tigrinusPocock, 1895 is removed from synonymy with P. everetti based on the lack of justification for the synonymy comb. rest.Omothymus dromeusChamberlin, 1917 is removed from Omothymus and returned to the restored genus Melognathuscomb. rest.