Oudemans described 18 new species of Phytoseiidae. He also redescribed Zercon similis Koch but ultimately relegated it to the status of a nomen nudum .Seven of the 18 species have been redescribed and their identities established by various authors: Typhlodromus aberrans, T. cucumeris, T. foenilis, T. reticulatus, T. rhenanus, T. tiliae and T. tiliarum. Typhlodromus elongatus and T. vitis have been designated as junior synonyms of T. aberrans. Seiulus spoofi, which has been regarded as a junior synonym of Phytoseius macropilis (Banks), is now restored as a separate species and is redescribed. The identities of T. heveae and S. finlandicus are established and redescribed, and the suspected conspecificity of T. pruni with S. finlandicus is confirmed. The identities of five other species remain either uncertain or unknown: T. hevearum, T. musci, T. tiliacolus, T. dahliae and S. truncatus.